Polyalkyleneimine derivative, composition, method for producing same, and carbon dioxide absorbent

Abstract

Provided is a novel polyalkyleneimine derivative.　This polyalkyleneimine derivative contains a bond between a methyl group and a nitrogen atom. The derivative preferably has a degree of substitution of methyl groups on hydrogen atoms bonded to nitrogen atoms of more than 0% and 100% or less. The derivative preferably has a number average molecular weight of 250-10,000.

Description

Polyalkylene imine derivatives, compositions, methods for producing the same, and carbon dioxide absorbers

[0001] The present invention relates to polyalkyleneimine derivatives and methods for producing the same. The present invention also relates to compositions containing polyalkyleneimine derivatives and methods for producing the same. Furthermore, the present invention relates to carbon dioxide absorbents using the polyalkyleneimine derivatives.

[0002] Patent Document 1 discloses a carbon dioxide adsorption / desorption material comprising a carrier and polyethyleneimine supported on the carrier. Specifically, the examples in Patent Document 1 describe alkylated branched polyethyleneimine alkylated with a lower alkyl group, which is either an ethyl group or an isopropyl group. Considering the application history, it was pointed out in the rejection notice that it was common technical knowledge at the time of application that carbon dioxide adsorption / desorption performance differs depending on the substituent, and the lower alkyl group in the claims was amended to an ethyl group or an isopropyl group. It is also stated that alkylated branched polyethyleneimine could not be synthesized in the case of a hexyl group.

[0003] Japanese Patent Publication No. 2020-168624

[0004] Based on the aforementioned background technology, Patent Document 1 did not disclose, to the extent that it could manufacture and use cases where the alkyl group of alkylated branched polyethyleneimine has neither two nor three carbon atoms. In other words, Patent Document 1 does not describe any specific compounds in which the hydrogen atom bonded to the nitrogen atom of polyethyleneimine is substituted with a methyl group.

[0005] Generally, carbon dioxide absorbents oxidize or degrade through the adsorption and desorption cycle, reducing their carbon dioxide absorption capacity. However, if a carbon dioxide absorbent with excellent oxidation resistance is used, the decrease in carbon dioxide absorption capacity after the adsorption and desorption cycle can be suppressed, extending the service life. Furthermore, if a carbon dioxide absorbent with excellent carbon dioxide desorption capacity at low temperatures is used when desorbing adsorbed carbon dioxide by raising the temperature, the energy and time required for the adsorption and desorption cycle can be reduced.

[0006] The object of the present invention is to provide novel polyalkyleneimine derivatives. In one aspect of the present invention, the polyalkyleneimine derivative exhibits excellent oxidation resistance (carbon dioxide absorption capacity maintenance rate). In one aspect of the present invention, the polyalkyleneimine derivative exhibits excellent carbon dioxide desorption ability at low temperatures (e.g., 58°C, 65°C, etc.). In one aspect of the present invention, the polyalkyleneimine derivative exhibits superior carbon dioxide absorption capacity maintenance rate compared to unsubstituted polyalkyleneimine, and superior initial carbon dioxide absorption capacity compared to polyalkyleneimine derivatives in which the hydrogen atoms bonded to the nitrogen atoms of polyethyleneimine are substituted with ethyl groups.

[0007] Another object of the present invention is to provide a novel composition comprising a polyalkyleneimine derivative. In one aspect of the present invention, the composition exhibits excellent oxidation resistance (carbon dioxide absorption capacity retention rate). In one aspect of the present invention, the composition exhibits excellent carbon dioxide desorption capacity at low temperatures (e.g., 58°C, 65°C, etc.). In one aspect of the present invention, the composition exhibits superior carbon dioxide absorption capacity retention rate compared to a composition containing unsubstituted polyalkyleneimine as a carbon dioxide absorbent, and superior initial carbon dioxide absorption capacity compared to a composition containing a polyalkyleneimine derivative in which a hydrogen atom bonded to the nitrogen atom of polyethyleneimine is substituted with an ethyl group as a carbon dioxide absorbent.

[0008] Another object of the present invention is to provide a novel method for producing polyalkyleneimine derivatives. In one aspect of the present invention, the polyalkyleneimine derivative produced by the method has excellent oxidation resistance (carbon dioxide absorption capacity retention rate). In one aspect of the present invention, the polyalkyleneimine derivative produced by the method has excellent carbon dioxide desorption capacity at low temperatures (e.g., 58°C, 65°C, etc.). In one aspect of the present invention, the polyalkyleneimine derivative produced by the method has a better carbon dioxide absorption capacity retention rate than unsubstituted polyalkyleneimines, and a better initial carbon dioxide absorption capacity than polyalkyleneimine derivatives in which the hydrogen atoms bonded to the nitrogen atoms of polyethyleneimine are substituted with ethyl groups.

[0009] Another object of the present invention is to provide a method for producing a novel composition containing a polyalkyleneimine derivative. In one aspect of the present invention, the composition produced by the method has excellent oxidation resistance (carbon dioxide absorption capacity retention rate). In one aspect of the present invention, the composition produced by the method has excellent carbon dioxide desorption capacity at low temperatures (e.g., 58°C, 65°C, etc.). In one aspect of the present invention, the composition produced by the method has a better carbon dioxide absorption capacity retention rate than a composition containing an unsubstituted polyalkyleneimine as a carbon dioxide absorbent, and a better initial carbon dioxide absorption capacity than a composition containing a polyalkyleneimine derivative in which a hydrogen atom bonded to the nitrogen atom of polyethyleneimine is substituted with an ethyl group as a carbon dioxide absorbent.

[0010] Another object of the present invention is to provide a novel carbon dioxide absorbent. In one aspect of the present invention, the carbon dioxide absorbent has excellent oxidation resistance (carbon dioxide absorption capacity retention rate). In one aspect of the present invention, the carbon dioxide absorbent has excellent carbon dioxide desorption capacity at low temperatures (e.g., 58°C, 65°C, etc.). In one aspect of the present invention, the carbon dioxide absorbent has a better carbon dioxide absorption capacity retention rate than a carbon dioxide absorbent containing an unsubstituted polyalkyleneimine, and a better initial carbon dioxide absorption capacity than a carbon dioxide absorbent containing a polyalkyleneimine derivative in which a hydrogen atom bonded to the nitrogen atom of polyethyleneimine is substituted with an ethyl group.

[0011] As a result of diligent research to achieve the above objective, the inventors have found that polyalkyleneimine derivatives in which the hydrogen atoms bonded to the nitrogen atom of polyethyleneimine are substituted with methyl groups exhibit excellent oxidation resistance (carbon dioxide absorption capacity maintenance rate) and carbon dioxide desorption capacity at low temperatures (e.g., 58°C, 65°C, etc.). In particular, they exhibit superior carbon dioxide absorption capacity maintenance rate compared to unsubstituted polyalkyleneimines, and furthermore, superior initial carbon dioxide absorption capacity compared to polyalkyleneimines in which the hydrogen atoms bonded to the nitrogen atom of polyethyleneimine are substituted with ethyl groups. The present invention was completed based on these findings.

[0012] In other words, the present invention provides polyalkylene imine derivatives containing a bond between a methyl group and a nitrogen atom.

[0013] The polyalkylene imine derivative preferably has a substitution rate of methyl groups on hydrogen atoms bonded to the nitrogen atom that is greater than 0% and less than or equal to 100%.

[0014] The polyalkylene imine derivative preferably has a number-average molecular weight of 250 to 10,000.

[0015] The present invention also provides a composition comprising a polyalkylene imine derivative containing a bond between a methyl group and a nitrogen atom, and further comprising a composition in which the amount of halogen ions is less than 4500 ppm by mass relative to the amount of the polyalkylene imine derivative.

[0016] Furthermore, the present invention provides a composition comprising a polyalkylene imine derivative containing a bond between a methyl group and a nitrogen atom, wherein the amount of halogen ions (mass ratio) relative to the amount of the polyalkylene imine derivative in the composition is less than the total amount (mass ratio) of alkali metal ions and alkaline earth metal ions relative to the amount of the polyalkylene imine derivative in the composition.

[0017] Furthermore, the present invention provides a method for producing a polyalkylene imine derivative containing a bond between a methyl group and a nitrogen atom, comprising a methylation step in which a hydrogen atom bonded to the nitrogen atom of the polyalkylene imine is replaced with a methyl group.

[0018] The methylation step is preferably a step of reacting a polyalkylene imine with a methyl halide.

[0019] The methylation step preferably includes a step of reacting the polyalkyleneimine with formalin and formic acid.

[0020] Furthermore, the present invention provides a method for producing a composition containing a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, comprising the following purification step: Purification step: A purification step to reduce the amount of halogen ions in a composition in which the amount of halogen ions relative to the amount of polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom is 4500 ppm by mass or more to less than 4500 ppm by mass.

[0021] Furthermore, the present invention provides a carbon dioxide absorbent comprising a carrier and the polyalkyleneimine derivative or a polyalkyleneimine derivative contained in the composition, supported on the carrier.

[0022] According to the present invention, novel polyalkyleneimine derivatives can be provided. In one aspect of the present invention, the polyalkyleneimine derivative exhibits excellent oxidation resistance (carbon dioxide absorption capacity maintenance rate). In one aspect of the present invention, the polyalkyleneimine derivative exhibits excellent carbon dioxide desorption ability at low temperatures (e.g., 58°C, 65°C, etc.). In one aspect of the present invention, the polyalkyleneimine derivative exhibits superior carbon dioxide absorption capacity maintenance rate compared to unsubstituted polyalkyleneimines, and superior initial carbon dioxide absorption capacity compared to polyalkyleneimine derivatives in which the hydrogen atoms bonded to the nitrogen atoms of polyethyleneimine are substituted with ethyl groups.

[0023] Furthermore, the present invention can provide a novel composition containing a polyalkyleneimine derivative. In one aspect of the present invention, the composition exhibits excellent oxidation resistance (carbon dioxide absorption capacity maintenance rate). In one aspect of the present invention, the composition exhibits excellent carbon dioxide desorption capacity at low temperatures (e.g., 58°C, 65°C, etc.). In one aspect of the present invention, the composition exhibits superior carbon dioxide absorption capacity maintenance rate compared to a composition containing unsubstituted polyalkyleneimine as a carbon dioxide absorbent, and superior initial carbon dioxide absorption capacity compared to a composition containing a polyalkyleneimine derivative in which a hydrogen atom bonded to the nitrogen atom of polyethyleneimine is substituted with an ethyl group as a carbon dioxide absorbent.

[0024] Further, according to the present invention, a novel method for producing a polyalkyleneimine derivative can be provided. In one aspect of the present invention, the polyalkyleneimine derivative produced by the method is excellent in oxidation resistance (carbon dioxide absorption capacity retention rate). In one aspect of the present invention, the polyalkyleneimine derivative produced by the method is excellent in carbon dioxide desorption ability at low temperatures (for example, 58 ° C, 65 ° C, etc.). In one aspect of the present invention, the polyalkyleneimine derivative produced by the method is superior in carbon dioxide absorption capacity retention rate to unsubstituted polyalkyleneimine and superior in initial carbon dioxide absorption capacity to polyalkyleneimine in which hydrogen atoms bonded to nitrogen atoms of polyethyleneimine are substituted with ethyl groups.

[0025] Further, according to the present invention, a novel method for producing a composition containing a polyalkyleneimine derivative can be provided. In one aspect of the present invention, the composition produced by the method is excellent in oxidation resistance (carbon dioxide absorption capacity retention rate). In one aspect of the present invention, the composition produced by the method is excellent in carbon dioxide desorption ability at low temperatures (for example, 58 ° C, 65 ° C, etc.). In one aspect of the present invention, the composition produced by the method is superior in carbon dioxide absorption capacity retention rate to a composition containing unsubstituted polyalkyleneimine as a carbon dioxide absorbent and superior in initial carbon dioxide absorption capacity to a composition containing a polyalkyleneimine derivative in which hydrogen atoms bonded to nitrogen atoms of polyethyleneimine are substituted with ethyl groups as a carbon dioxide absorbent.

[0026] Further, according to the present invention, a novel carbon dioxide absorbent can be provided. In one aspect of the present invention, the carbon dioxide absorbent is excellent in oxidation resistance (carbon dioxide absorption capacity retention rate). In one aspect of the present invention, the carbon dioxide absorbent is excellent in carbon dioxide desorption ability at low temperatures (for example, 58 ° C, 65 ° C, etc.). In one aspect of the present invention, the carbon dioxide absorbent is superior in carbon dioxide absorption capacity retention rate to unsubstituted polyalkyleneimine and superior in initial carbon dioxide absorption capacity to a polyalkyleneimine derivative in which hydrogen atoms bonded to nitrogen atoms of polyethyleneimine are substituted with ethyl groups.

[0027] The preferred embodiments of the present invention will be specifically described below. However, the present invention is not limited to the following description and can be appropriately modified and applied without changing the gist of the present invention. In addition, forms in which two or more of the individual preferred embodiments of the present invention described below are combined also fall within the preferred embodiments of the present invention. Further, in this specification, "X to Y" indicating a range means "X or more and Y or less", and "weight" and "mass", "weight %" and "mass %", and "parts by weight" and "parts by mass" are treated as synonyms. Also, unless otherwise specified, measurements of operations and physical properties are made under the conditions of room temperature (20 to 25°C) / relative humidity 40 to 50%.

[0028] [Polyalkyleneimine derivative] The present invention provides a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom. The polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom may be referred to as the "polyalkyleneimine derivative of the present invention". The polyalkyleneimine derivative of the present invention has such a structure that it is excellent in oxidation resistance (maintenance rate of carbon dioxide absorption capacity after deterioration treatment), and is also excellent in initial carbon dioxide absorption capacity compared to a polyalkyleneimine derivative in which a hydrogen atom bonded to a nitrogen atom of polyethyleneimine is substituted with an ethyl group. Therefore, it can be suitably used, for example, in the carbon dioxide absorbent described later.

[0029] (Polyalkyleneimine) In this specification, mere "polyalkyleneimine" means a polyalkyleneimine that does not contain a bond between a methyl group and a nitrogen atom, that is, a polyalkyleneimine before substituting a hydrogen atom bonded to a nitrogen atom with a methyl group. This "polyalkyleneimine" may be a polyalkyleneimine in which not all hydrogen atoms are substituted, a polyalkyleneimine in which some hydrogen atoms are substituted with substituents other than methyl groups, and can also be referred to as "raw material polyalkyleneimine".

[0030] The polyalkyleneimine is a compound having structural units derived from alkyleneimine. The structural units derived from alkyleneimine are not particularly limited, but structural units derived from alkyleneimine having 2 to 6 carbon atoms are preferred. The polyalkyleneimine may be used alone or two or more types.

[0031] The polyalkylene imine may or may not have substituents other than methyl groups. Examples of substituents other than methyl groups include alkylene oxides having 2 to 30 carbon atoms (e.g., ethylene oxide, propylene oxide, butylene oxide, etc.), epoxy compounds, vinyl group-containing compounds, isocyanate group-containing compounds, acid anhydrides, etc. It is preferable that the polyalkylene imine does not contain ethyl groups, does not contain propyl groups, or does not contain both ethyl and propyl groups.

[0032] Examples of the polyalkyleneimine include polymers of alkyleneimines. Examples of the alkyleneimines include alkyleneimines having 2 to 6 carbon atoms, such as aziridine, 2-methylaziridine, azetidine, 1,2-butyleneimine, 2,3-butyleneimine, and 2,2-dimethylethyleneimine. Only one type of alkyleneimine may be used, or two or more types may be used. That is, the polyalkyleneimine may be a homopolymer or a copolymer of alkyleneimines.

[0033] Among the polyalkyleneimines, polyethyleneimine (PEI) having ethyleneimine structural units is preferred. The polyalkyleneimines are not particularly limited, and commercially available products may be used, or those produced by known manufacturing methods may be used.

[0034] (Derivatives) The polyalkyleneimine derivatives of the present invention are the same as the polyalkyleneimine described above, except that they contain a bond between a methyl group and a nitrogen atom. In the polyalkyleneimine derivatives of the present invention, it is preferable that the substitution rate of methyl groups to the hydrogen atom bonded to the nitrogen atom of the polyalkyleneimine is greater than 0% and less than or equal to 100%. Examples of lower limits for the substitution rate include 1% or more, 3% or more, 5% or more, 10% or more, etc. In particular, a substitution rate of 10% or more provides excellent carbon dioxide desorption ability at low temperatures (e.g., 58°C, 65°C, etc.). Examples of upper limits for the substitution rate include 99% or less, 90% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20%, 15% or less, etc. Any combination of the lower and upper limits may be used. In the polyalkylene imine derivative of the present invention, the substitution rate of methyl groups on hydrogen atoms bonded to the nitrogen atom is preferably 1 to 20% from the viewpoint of even greater oxidation resistance (retention rate of carbon dioxide absorption capacity after degradation treatment), and more preferably 10 to 20% from the viewpoint of superior carbon dioxide desorption capacity at low temperatures (e.g., 58°C, 65°C, etc.). Furthermore, the lower the substitution rate (e.g., 15% or less), the more likely it is to exhibit initial carbon dioxide absorption capacity equivalent to or greater than that of a polyalkylene imine in which hydrogen atoms bonded to the nitrogen atom are not substituted.

[0035] The substitution rate X (%) of methyl groups on hydrogen atoms bonded to the nitrogen atom can be calculated by applying the number of methyl groups a in the polyalkylene imine derivative of the present invention, the number of nitrogen atoms b in the primary amino group of the polyalkylene imine, and the number of nitrogen atoms c in the secondary amino group to the following formula: X (%) = a / (2b + c) × 100

[0036] Furthermore, the substitution rate can be determined by performing known measurements such as nuclear magnetic resonance (NMR) spectroscopy. In this case, for example, the peaks originating from hydrogen derived from methyl groups in the polyalkylene imine derivative and the peaks originating from hydrogen derived from ethylene chains in the polyalkylene imine may be identified, and the substitution rate may be calculated from the intensity ratio of these peaks.

[0037] In the polyalkylene imine derivative of the present invention, the ratio of the number of bonds between nitrogen atoms and methyl groups to the number of bonds between nitrogen atoms and hydrogen atoms is preferably (1 to 99):(1 to 99), more preferably (5 to 30):(70 to 95), and even more preferably (10 to 20):(90 to 80).

[0038] The polyalkylene imine derivative of the present invention may have substituents other than methyl groups, or it may not have substituents other than methyl groups, but from the viewpoint of having even better oxidation resistance (retention rate of carbon dioxide absorption capacity after degradation treatment), it is preferable that it does not have substituents other than methyl groups. Examples of substituents other than methyl groups include alkylene oxides having 2 to 30 carbon atoms (e.g., ethylene oxide, propylene oxide, butylene oxide, etc.), epoxy compounds, vinyl group-containing compounds, isocyanate group-containing compounds, acid anhydrides, etc. It is preferable that the polyalkylene imine derivative of the present invention does not contain ethyl groups, does not contain propyl groups, or does not contain both ethyl and propyl groups.

[0039] If the polyalkylene imine derivative of the present invention further has substituents other than methyl groups, the molar ratio of methyl groups to substituents other than methyl groups in the polyalkylene imine derivative of the present invention is preferably (50-99):(1-50), more preferably (80-99):(1-20), and even more preferably (90-99):(1-10). If the polyalkylene imine derivative of the present invention further has substituents other than methyl groups, the ratio of the number of methyl groups to the total number of substituents including methyl groups is preferably 0.5-0.99, more preferably 0.8-0.99, and even more preferably 0.9-0.99.

[0040] The number-average molecular weight (Mn) of the polyalkylene imine derivative of the present invention is preferably 250 to 10000 from the viewpoint of even greater oxidation resistance. The lower limit of the number-average molecular weight is more preferably 400, and even more preferably 600. The upper limit of the number-average molecular weight is more preferably 8000, even more preferably 5000, even more preferably 3000, particularly preferably 2000, and most preferably 1500.

[0041] The aforementioned number-average molecular weight can be measured by a known method using pullulan as a standard substance in gel permeation chromatography (GPC). In this invention, the following conditions are adopted for GPC measurement: Measurement apparatus: GPC apparatus (manufactured by Shimadzu Corporation) Column used: Shodex OHpak SB-807HQ (2 tubes) + SB-806M / HQ (2 tubes) manufactured by Resonaq Corporation Column temperature: 40°C Eluent: Aqueous solution prepared as 0.5 mol% sodium nitrate and 0.5 mol% acetic acid Flow rate: 0.4 mL / min Sample concentration: 0.5 mass% Sample injection volume: 50 μL Standard substance: Shodex STANDARD P-82 (manufactured by Resonaq Corporation) Detector: Differential refractometer (manufactured by Shimadzu Corporation)

[0042] The polyalkylene imine derivative of the present invention comprises at least a primary amino group (-NH ２ The polyalkylene imine derivative of the present invention preferably has a primary amino group and a secondary amino group, and more preferably has a primary amino group, a secondary amino group, and a tertiary amino group (-N<).

[0043] The molar ratio (amine ratio) of primary amino groups, secondary amino groups, and tertiary amino groups in the polyalkyleneimine derivative of the present invention is preferably 1 to 35:10 to 70:10 to 70 (total 100) for primary amino groups:secondary amino groups:tertiary amino groups, more preferably 1 to 30:10 to 80:10 to 80 (total 100), even more preferably 1 to 20:20 to 80:20 to 80 (total 100), and particularly preferably 1 to 10:30 to 80:30 to 80 (total 100).

[0044] In this specification, the amine ratio can be determined by performing a measurement on the polyalkylene imine derivative of the present invention using nuclear magnetic resonance (NMR) spectroscopy. For example, １３When it is possible to identify the carbon atom directly bonded to the nitrogen atom in the primary amino group, the carbon atom directly bonded to the nitrogen atom in the secondary amino group, and the carbon atom directly bonded to the nitrogen atom in the tertiary amino group from the chart obtained by measuring 13C-NMR, the amine ratio can be calculated by determining the intensity ratio of the peaks derived from each of these carbon atoms. Specifically, the number b of nitrogen atoms in the primary amino group, the number c of secondary amino groups, and the number d of tertiary amino groups are calculated, and the ratio of b, c, and d is defined as the amine ratio, such that primary amino group:secondary amino group:tertiary amino group = b:c:d. When the structure of the polyalkyleneimine is complex or the like, when the analysis is difficult only by the measurement of 13C-NMR as described above, the peak derived from a characteristic atom such as the peak derived from each of the carbon atoms is identified by a known method as appropriate, and the amine ratio may be calculated by determining the intensity ratio of each peak. Examples of the method suitable for the analysis include, for example, １３ when the analysis is difficult only by the measurement of 13C-NMR, the peak derived from a characteristic atom such as the peak derived from each of the carbon atoms is identified by a known method as appropriate, and the amine ratio may be calculated by determining the intensity ratio of each peak. Examples of the method suitable for the analysis include, for example, １ 1H-NMR, １３ 13C-NMR, １５ one-dimensional NMR such as 15N-NMR, １ 1H- １ 1H-1H COSY (COrrelation Spectroscopy) and other homonuclear correlation two-dimensional NMR, １ 1H- １３ 13C HMQC (Heteronuclear Multiple Quantum Coherence), １ 1H- １３ 13C HMBC (Heteronuclear Multiple Bond Connectivity), １ 1H- １３ 13C HMQC-TOCSY (TOtally Correlated Spectroscopy), １ 1H- １５ 1H-15N HMBC and other heteronuclear correlation two-dimensional NMR, etc. can be mentioned.

[0045] The primary amino group content in the polyalkyleneimine derivative of the present invention is preferably 1 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on 100 mol% of the total amount of alkyleneimine constituting the polyalkyleneimine derivative of the present invention. Furthermore, the above content is preferably 50 mol% or less, more preferably 45 mol% or less, and even more preferably 40 mol% or less.

[0046] The secondary amino group content in the polyalkyleneimine derivative of the present invention is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, based on 100 mol% of the total amount of alkyleneimine constituting the polyalkyleneimine derivative of the present invention. Furthermore, the above content is preferably 80 mol% or less, more preferably 75 mol% or less, and even more preferably 70 mol% or less.

[0047] The content of tertiary amino groups in the polyalkyleneimine derivative of the present invention is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, based on 100 mol% of the total amount of alkyleneimine constituting the polyalkyleneimine derivative of the present invention. Furthermore, the content is preferably 80 mol% or less, more preferably 75 mol% or less, and even more preferably 70 mol% or less.

[0048] [Method for Producing Polyalkyleneimine Derivatives Containing a Bond Between a Methyl Group and a Nitrogen Atom] A method for producing polyalkyleneimine derivatives containing a bond between a methyl group and a nitrogen atom preferably includes a methylation step in which a hydrogen atom bonded to the nitrogen atom of the polyalkyleneimine is replaced with a methyl group. A method for producing polyalkyleneimine derivatives containing a bond between a methyl group and a nitrogen atom, which includes a methylation step in which a hydrogen atom bonded to the nitrogen atom of the polyalkyleneimine is replaced with a methyl group, may be referred to as "Method 1 of the Present Invention." The polyalkyleneimine derivatives of the Present Invention may be produced by methods other than Method 1 of the Present Invention. Furthermore, for the polyalkyleneimine and the polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom in Method 1 of the Present Invention, you may refer to the description of polyalkyleneimine in the above-mentioned polyalkyleneimine derivative of the Present Invention and the above-mentioned description of the polyalkyleneimine derivative of the Present Invention, respectively.

[0049] (Methylation step) Examples of the methylation step include a step of reacting polyalkyleneimine with methyl halogen, a step of reacting polyalkyleneimine with formalin and formic acid, and from the viewpoint of further improving the oxidation resistance of the polyalkyleneimine derivative obtained after the step, a step of reacting polyalkyleneimine with methyl halogen is preferred.

[0050] The reactivity of amines is generally considered to be higher at the primary amino group than at the secondary amino group. Therefore, in the step of reacting the polyalkylene imine with methyl halogen, the methyl halogen is usually considered to preferentially add to the primary amino group of the polyalkylene imine. However, the methyl halogen may also add to the secondary amino group of the polyalkylene imine.

[0051] In the step of reacting polyalkyleneimine with methyl halide, the mass ratio of polyalkyleneimine to methyl halide may be 0.01 to 50 parts by mass, 0.01 to 30 parts by mass, or 0.01 to 20 parts by mass of methyl halide per 100 parts by mass of polyalkyleneimine. The reaction temperature may be 50 to 100°C, 70 to 100°C, or 90 to 100°C. At high temperatures above 200°C, the polyalkyleneimine may decompose and the yield may decrease. At low temperatures below 50°C, the reactivity decreases, and the reaction time may be longer. The reaction time may be 1 to 24 hours, 2 to 12 hours, or 3 to 6 hours. Examples of methyl halide include methyl fluoride, methyl chloride, methyl bromide, and methyl iodide, and methyl chloride is preferred from the viewpoint of further improving the oxidation resistance of the polyalkyleneimine derivative obtained after the step. The above reaction may be carried out in the presence or absence of a solvent. Examples of the solvent include polar organic solvents such as methanol, ethanol, 2-propanol, and butanol.

[0052] Furthermore, the process of reacting polyalkyleneimine with formalin and formic acid preferably includes a step of mixing the polyalkyleneimine, formalin and formic acid (mixing step). In the mixing step, the method of mixing each component is not particularly limited; for example, all components may be mixed at once, or any of the components may be added and mixed later. In the mixing step, the method of adding each component is not particularly limited, and known or conventional methods can be applied. For example, they may be added at once to the reaction system, continuously (added over a certain period of time), or intermittently (added in multiple installments). Also, the rate of addition may be changed once or more during the addition process. In addition, a solvent may be used in the mixing step as needed, and a solvent may or may not be used for any of the components. From the viewpoint of excellent reactivity, the step of reacting polyalkyleneimine with formalin and formic acid preferably includes a methylation step of mixing the polyalkyleneimine with formalin, a heating step, and a methylation step of mixing formic acid with the solution in which formalin has been completely dissolved by heating. Formalin may be formaldehyde or paraformaldehyde.

[0053] In the heating step, the temperature may be raised to 50-100°C, 70-100°C, or 90-100°C. In the methylation step where formic acid is mixed, the reaction temperature may be 50-100°C, 60-90°C, or 60-80°C. In the methylation step where formic acid is mixed, formic acid may be added dropwise by known or conventional methods. After the methylation step where formic acid is mixed, there may be a further aging step. In the aging step, for example, the reaction solution is maintained at 90-110°C for 1-6 hours (preferably 2-4 hours).

[0054] (Composition) A composition can be prepared using the polyalkyleneimine derivative of the present invention. The composition tends to have excellent oxidation resistance (retention rate of carbon dioxide absorption capacity after degradation treatment) due to containing the polyalkyleneimine derivative of the present invention. In other words, the composition is preferably a composition for carbon dioxide absorbent.

[0055] The composition may be liquid or solid. When the composition is used in a carbon dioxide absorbent described later, it is preferable that the composition be liquid from the viewpoint of superior handling and support properties. Examples of liquid compositions include compositions containing a solvent such as water, in which the polyalkyleneimine derivative of the present invention is dissolved or dispersed in the solvent. Other examples of liquid compositions include compositions that do not contain a solvent such as water, in which the polyalkyleneimine derivative of the present invention is in liquid form. Examples of solid compositions include solvent-free compositions containing the polyalkyleneimine derivative of the present invention.

[0056] (Other Components) The above composition can be produced, for example, by adding various components to the polyalkylene imine derivative of the present invention. Other components other than the polyalkylene imine derivative of the present invention can be used as appropriate. Examples of other components include solvents (e.g., water; organic solvents such as methanol and ethanol), surfactants (anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants), antioxidants, antioxidant aids, crystallization inhibitors, etc. Other components may also include impurities such as metals that are not intentionally included. Only one of the other components may be used, or two or more may be used. The HLB (hydrophilic-lipophilic balance) of the surfactant is preferably 10 or more, more preferably 12 or more, and even more preferably 15 or more.

[0057] As the antioxidant, radical scavengers, peroxide decomposers, etc., can be used. As the radical scavenger, phenolic antioxidants, amine antioxidants, etc., can be used, and amine antioxidants are preferred. As the peroxide decomposer, there are no particular limitations as long as it can effectively decompose peroxides, but sulfur-based antioxidants, phosphorus-based antioxidants, phenolic antioxidants, hindered amine antioxidants, etc., can be used. Examples of the sulfur-based antioxidants include 2-hydroxyethyl disulfide, 1,2-bis[(2-hydroxyethyl)thio]ethane, thiodipropionic acid, dilauryl thiodipropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, dimyristyl thiodipropionate, distearyl-β,β'-thiodibutyrate, thiobis(β-naphthol), thiobis(N-phenyl-β-naphthylamine), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, dodecyl mercaptan, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, nickel dibutyldithiocarbamate, nickel isopropyl xanthate, dodecanethiol, and the like, with 2-hydroxyethyl disulfide and 1,2-bis[(2-hydroxyethyl)thio]ethane being more preferred.Examples of the phosphorus-based antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, phenyldiisodecyl phosphite, tris(nonylphenyl) phosphite, diisodecylpentaerythritol phosphite, tris(2,4-di-t-butylphenyl) phosphite, cyclic neopentanetetraylbis(octadecyl) phosphite, cyclic neopentanetetraylbis(2,4-di-t-butylphenyl) phosphite, and cyclic neopentanetetraylbis(2,4-di-t- Phosphates such as butyl-4-methylphenyl) phosphite and bis[2-t-butyl-6-methyl-4-{2-(octadecyloxycarbonyl)ethyl}phenyl]hydrogen phosphite (phosphite-based antioxidants); oxaphosphaphenanthrene oxides such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are examples.Examples of the phenolic antioxidants include monophenols such as 4-methoxyphenol, hydroquinone, 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-p-ethylphenol, and stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy} Examples include bisphenols such as ethyl[2,4,8,10-tetraoxaspiro[5.5]undecane; 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane; 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene; tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane; bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester; 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1H,3H,5H)trione; and high molecular weight phenols such as tocopherol. Examples of the hindered amine antioxidants include bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, and 4-hydroxy-2,2,6,6-tetramethylpiperidine.

[0058] Examples of crystallization inhibitors include water-soluble polymers such as polyvinylpyrrolidone, polyvinyl alcohol, and hydroxyethylcellulose. By using water-soluble polymers as crystallization inhibitors, it is possible to suppress the secondary interaction between carbamic acid, which is produced by the reaction of the oligoamine compound with carbon dioxide, and the oligoamine compound, which can lead to the formation of insoluble salts.

[0059] Examples of the metal impurity include elemental metals and components containing metals (e.g., metal oxides). Examples of the metal include transition metals. The transition metal is an element from any of groups 3 to 12 of the periodic table, and more specifically, at least one selected from the group consisting of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, and more specifically, at least one selected from the group consisting of chromium, manganese, iron, cobalt, nickel, and copper.

[0060] From the viewpoint of excellent durability, the content of metal-containing components in the composition is preferably 50 ppm or less, more preferably 30 ppm or less, and even more preferably 10 ppm or less, based on 100% by mass of the total amount of the composition. Furthermore, it is particularly preferable that the composition is substantially free of metal-containing components. The content may also be 0.5 ppm or more, or 1 ppm or more, based on 100% by mass of the total amount of the composition. More specifically, the total content of each component containing chromium, manganese, iron, cobalt, nickel, and copper in the composition is preferably within the above range, based on 100% by mass of the total amount of the composition. The content can be measured, for example, by X-ray fluorescence (XRF) analysis.

[0061] The aforementioned composition can be produced by known or conventional methods. For example, it can be produced by mixing the other components with the polyalkylene imine derivative of the present invention and stirring.

[0062] [Composition containing a polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom, with a halogen ion content of less than 4500 ppm by mass] The present invention provides a composition containing a polyalkyleneimine derivative having a halogen ion content of less than 4500 ppm by mass, with a bond between a methyl group and a nitrogen atom. A composition containing a polyalkyleneimine derivative having a halogen ion content of less than 4500 ppm by mass, with a bond between a methyl group and a nitrogen atom, may be referred to as "Composition 1 of the present invention." The halogen ion content is the amount (in ppm by mass) relative to the amount of the polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom, and can be converted to the solid content of the composition if no other nonvolatile components are added to the composition. That is, Composition 1 of the present invention can be rephrased as "a composition comprising a polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom, and further comprising a composition in which the amount of halogen ions is less than 4500 ppm by mass relative to the amount of the polyalkyleneimine derivative." Composition 1 of the present invention has excellent oxidation resistance (retention rate of carbon dioxide absorption capacity after degradation treatment), and can therefore be suitably used, for example, in carbon dioxide absorbents described later. For polyalkylene imine derivatives containing a bond between a methyl group and a nitrogen atom in Composition 1 of the present invention, refer to the above description of polyalkylene imine derivatives of the present invention.

[0063] Examples of the halogen ions include fluoride ions, chloride ions, bromide ions, and iodide ions. Among these, a low concentration of chloride ions is preferred. The amount of halogen ions in composition 1 of the present invention (i.e., the mass ratio (ppm) of the halogen ions to the polyalkylene imine derivative, the same applies hereinafter) can be measured by ion chromatography or the like. The conditions for ion chromatography may be, for example, the following conditions.

[0064] Apparatus: Dionex® ICS-2000 (manufactured by Thermo Fisher Scientific K.K.) Detector: Conductivity detector Column: Dionex® IonPac® AS-18 (manufactured by Thermo Fisher Scientific K.K.) Guard column: Dionex® IonPac® AG-18 (manufactured by Thermo Fisher Scientific K.K.) Column temperature: 30°C Eluent: KOH aqueous solution (15 mmol / L) Flow rate: 0.9 mL / min Injection volume: 25 μL

[0065] Examples of lower limits for the halogen ion content of composition 1 of the present invention include greater than 0 ppm by mass, 1 ppm or more by mass, 10 ppm or more by mass, 100 ppm or more by mass, 200 ppm or more by mass, 250 ppm or more by mass, etc. Examples of upper limits for the halogen ion content of composition 1 of the present invention include 4100 ppm or less by mass, 4000 ppm or less by mass, 3000 ppm or less by mass, 2000 ppm or less by mass, 1500 ppm or less by mass, etc. Any combination of the lower and upper limits mentioned above may be used.

[0066] [A composition comprising a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, wherein the amount of halogen ions (mass ratio) to the amount of the polyalkyleneimine derivative in the composition is less than the total amount (mass ratio) of alkali metal ions and alkaline earth metal ions to the amount of the polyalkyleneimine derivative in the composition.] The present invention provides a composition comprising a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, wherein the amount of halogen ions (mass ratio) to the amount of the polyalkyleneimine derivative in the composition is less than the total amount (mass ratio) of alkali metal ions and alkaline earth metal ions to the amount of the polyalkyleneimine derivative in the composition. The composition may be referred to as "Composition 2 of the present invention." The composition of the present invention encompasses embodiments of Composition 1 and Composition 2 of the present invention. Composition 2 of the present invention has excellent oxidation resistance (carbon dioxide absorption capacity maintenance rate after degradation treatment), and can therefore be suitably used, for example, in carbon dioxide absorbents described later. For polyalkylene imine derivatives containing a bond between a methyl group and a nitrogen atom in Composition 2 of the present invention, refer to the above description of the polyalkylene imine derivatives of the present invention.

[0067] The amount of halogen ions relative to the amount of the polyalkylene imine derivative (mass ratio) and the total amount of alkali metal ions and alkaline earth metal ions relative to the amount of the polyalkylene imine derivative (mass ratio) in composition 2 of the present invention can be measured by performing ion chromatography analysis or the like on the composition.

[0068] Examples of the halogen ions include fluoride ions, chloride ions, bromide ions, and iodide ions. Among these, a low concentration of chloride ions is preferred.

[0069] The conditions for ion chromatography analysis to measure the amount (mass ratio) of halogen ions relative to the polyalkylene imine derivative in composition 2 of the present invention may be the same as, for example, the conditions for ion chromatography analysis to measure the halogen ion concentration of composition 1 of the present invention.

[0070] Examples of alkali metal ions include lithium ions, sodium ions, potassium ions, rubidium ions, and cesium ions, with sodium ions being preferred. Examples of alkaline earth metal ions include beryllium ions, magnesium ions, calcium ions, strontium ions, barium ions, and radium ions, with magnesium ions being preferred.

[0071] The conditions for ion chromatographic analysis to measure the amount (mass ratio) of at least one selected from the group consisting of alkali metal ions and alkaline earth metal ions relative to the amount of the polyalkylene imine derivative in the composition may be, for example, the following conditions.

[0072] Apparatus: Dionex® ICS-2000 (manufactured by Thermo Fisher Scientific K.K.) Detector: Conductivity detector Column: Dionex® IonPac® CS-16 (manufactured by Thermo Fisher Scientific K.K.) Guard column: Dionex® IonPac® CG-16 (manufactured by Thermo Fisher Scientific K.K.) Column temperature: 30°C Eluent: Methanesulfonic acid aqueous solution (15 mmol / L) Flow rate: 0.9 mL / min Injection volume: 25 μL

[0073] In composition 2 of the present invention, even when the amount of halogen ions (mass ratio) to the amount of polyalkylene imine derivative is 4500 ppm by mass or more, the composition tends to have a better carbon dioxide absorption capacity maintenance rate than a composition containing unsubstituted polyalkylene imine as a carbon dioxide absorbent, and a better initial carbon dioxide absorption capacity than a composition containing a polyalkylene imine derivative in which the hydrogen atoms bonded to the nitrogen atom of polyethyleneimine are substituted with ethyl groups.

[0074] [Method for producing a composition containing a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom] A method for producing a composition containing a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom preferably includes, for example, a "purification step that reduces the amount of halogen ions in a composition containing a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, where the amount of halogen ions is 4500 ppm by mass or more, to less than 4500 ppm by mass" (hereinafter sometimes referred to as the "purification step"). A method for producing a composition containing a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, which includes the purification step, may be referred to as "Method 2 of the present invention". Note that the composition of the present invention may be produced by a method other than Method 2 of the present invention. The amount of halogen ions is the amount relative to the amount of the polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom. That is, the purification step can be rephrased as "a purification step that reduces the amount of halogen ions in a composition where the amount of halogen ions relative to the amount of the polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom is 4500 ppm by mass or more, to less than 4500 ppm by mass". For the composition produced by the manufacturing method 2 of the present invention, you may refer to the description of composition 1 of the present invention above. For the amount of halogen ions (mass ppm) relative to the amount of polyalkylene imine derivative in the composition produced by the manufacturing method 2 of the present invention, you may refer to the description of the amount of halogen ions in composition 1 of the present invention above.

[0075] The purification process preferably includes a step of adsorbing halogen ions contained in a composition in which the amount of halogen ions relative to the amount of polyalkylene imine derivative containing a bond between a methyl group and a nitrogen atom is 4500 ppm by mass or more onto an ion exchange resin (adsorption step), a step of neutralizing the by-product acid, a step of separating the salt, and so on.

[0076] In the adsorption step, an anion exchange resin is preferred as the ion exchange resin. Examples of the anion exchange resin include a strongly basic anion exchange resin which is the OH form of a copolymer of styrene-ethylstyrene-divinylbenzene having a triethylamine functional group, a strongly basic anion exchange resin having a quaternary ammonium group, and a weakly basic anion exchange resin having a primary or secondary amine. The amount of halogen ions in the composition subjected to the purification step (adsorption step, etc.) may be 20,000 ppm by mass or less relative to the amount of the polyalkylene imine derivative. The method for adsorbing halogen ions onto the ion exchange resin may be a known or conventional method.

[0077] Furthermore, the neutralization step is not particularly limited in its specific operation as long as it can neutralize the by-product acid, and known or conventional methods can be employed. For example, such a neutralization step may involve adding an alkaline aqueous solution containing one or more bases, such as sodium hydroxide or potassium hydroxide, and neutralizing it at an appropriate temperature and time.

[0078] Furthermore, regarding the salt separation step, there are no particular restrictions on the specific operation as long as the target product can be recovered in the organic layer, and known or conventional methods such as decantation and filtration can be employed.

[0079] A method for producing a composition containing a polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom is preferably also comprising, for example, "a step of adding at least one selected from the group consisting of alkali metal ion hydroxides and alkoxylated compounds, alkaline earth metal ion hydroxides and alkoxylated compounds, alkali metal ion salts with a conjugate base of a weak acid, and alkaline earth metal ion salts with a conjugate base of a weak acid to a composition containing a polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom, to obtain a composition in which the amount of halogen ions (mass ratio) to the amount of the polyalkyleneimine derivative is less than the total amount (mass ratio) of alkali metal ions and alkaline earth metal ions to the amount of the polyalkyleneimine derivative" (hereinafter sometimes referred to as the "addition step"). A method for producing a composition containing a polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom, having the above addition step, may be referred to as "production method 3 of the present invention". Furthermore, the manufacturing method 3 of the present invention may include subjecting the composition obtained after the purification step (such as the adsorption step) to the addition step, or subjecting the composition obtained after the addition step to the purification step (such as the adsorption step). In addition, the composition of the present invention may be manufactured by a method other than the manufacturing method 3 of the present invention.

[0080] Examples of alkali metal ion hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, with sodium hydroxide being preferred. Examples of alkali metal ion alkoxyides include sodium methoxide. Examples of alkaline earth metal hydroxides include beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, and radium hydroxide, with magnesium hydroxide being preferred. Examples of alkaline earth metal ion alkoxyides include magnesium methoxide. Examples of alkali metal ion salts with a conjugate base of a weak acid include salts of alkali metals such as sodium and potassium with weak acids such as citric acid, acetic acid, carbonic acid, and phosphoric acid, specifically sodium bicarbonate, tripotassium phosphate, and trisodium citrate. Examples of alkaline earth metal ion salts with a conjugate base of a weak acid include salts of alkaline earth metals such as magnesium and calcium with weak acids such as citric acid, acetic acid, carbonic acid, and phosphoric acid, specifically magnesium acetate, calcium acetate, and magnesium citrate.

[0081] The aforementioned addition step may be carried out in the presence of a polar organic solvent such as water, methanol, ethanol, or isopropanol, or in the absence of a solvent.

[0082] In the manufacturing method 3 of the present invention, it is preferable to include a salt separation step after the addition step. For the salt separation step, refer to the explanation of the salt separation step in the purification step described above.

[0083] For compositions produced by the manufacturing method 3 of the present invention, you may refer to the description of composition 2 of the present invention above.

[0084] [Carbon Dioxide Absorbent] A carbon dioxide absorbent can be prepared using the polyalkyleneimine derivative of the present invention or the composition and carrier of the present invention. A carbon dioxide absorbent comprising a carrier and the polyalkyleneimine derivative of the present invention or a polyalkyleneimine derivative contained in the composition of the present invention supported on the carrier may be referred to as "the carbon dioxide absorbent of the present invention." The carbon dioxide absorbent of the present invention tends to have excellent oxidation resistance (retention rate of carbon dioxide absorption capacity after degradation treatment) because the polyalkyleneimine derivative of the present invention is supported on the carrier.

[0085] The polyalkylene imine derivative of the present invention in the carbon dioxide absorbent of the present invention can adsorb and desorb carbon dioxide because the amino groups within the molecule undergo a chemical reaction with carbon dioxide to reversibly form carbamates and bicarbonates. In this specification, "absorption" is used to include adsorption and desorption, and may also be referred to as sorption.

[0086] The carbon dioxide absorbent of the present invention may contain other components besides the polyalkylene imine derivative or composition of the present invention and the carrier. The carbon dioxide absorbent of the present invention may consist of the polyalkylene imine derivative or composition of the present invention and the carrier, or it may be manufactured by adding various components to the polyalkylene imine derivative or composition of the present invention and the carrier, for example. Examples of the various components are those described and illustrated as other components that may be contained in the composition. Only one of the various components may be used, or two or more may be used.

[0087] From the viewpoint of improving carbon dioxide adsorption and desorption capacity, the aforementioned carrier is preferably a porous carrier particle. Furthermore, examples of materials constituting the carrier include inorganic materials and polymer materials. Specifically, the carrier is preferably a porous carrier particle composed of an inorganic material and / or a polymer material.

[0088] The inorganic material preferably includes at least one selected from the group consisting of bentonite, attapulgite, kaolinite, montmorillonite, ball clay, fuller's earth, hectorite, palygorskite, saponite, sepiolite, halloysite, silica, calcium sulfate, zeolite, alumina, activated carbon, and metal-organic structures, with silica and / or alumina being more preferred, and silica even more preferred. The silica is not particularly limited, and known silicas such as fumed silica produced by a dry method, precipitated silica produced by a wet method, silica gel, and silica sol can be used as appropriate. The inorganic material may be used by one or more types.

[0089] Examples of the polymer material include ether sulfone (PES), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), cellulose mixed ester or nitrocellulose (NC), polyolefin, polyethylene, polypropylene, polymethylpentene, polyketone, polyimide, polystyrene, polymethyl methacrylate, polydimethylsiloxane, polyester, nylon, polycaprolactone, polylactic acid, polyvinyl alcohol, and polyglycolic acid. One type of polymer material may be used, or two or more types may be used.

[0090] The specific surface area of ​​the aforementioned carrier is set at 70 m² from the viewpoint of having excellent carbon dioxide adsorption and desorption capabilities. ２ Preferably 80 m / g or more, and more preferably 80 m ２ / g or more, more preferably 100m ２ It is 1 / g or more. Furthermore, the specific surface area is 800 m². ２ It may be less than / g, and 650m ２ It may be less than / g, and 500m ２ It may be less than / g.

[0091] From the viewpoint of excellent carbon dioxide adsorption / desorption ability, the content of the polyalkylene imine derivative of the present invention in the carbon dioxide absorbent is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the total amount of the carrier. Furthermore, from the viewpoint of excellent carbon dioxide adsorption / desorption ability and support, the content is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the total amount of the carrier. Furthermore, the content of the composition in the carbon dioxide absorbent is preferably within the above range per 100 parts by mass of the total amount of the carrier.

[0092] The carrier may contain metals as impurities. Examples of the metals are those described and illustrated as other metal components that may be included in the composition. From the viewpoint of excellent durability, the content of the metal-containing component in the carrier is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, even more preferably 3,000 ppm or less, and particularly preferably 2,000 ppm or less, based on 100% by mass of the total amount of the carrier. Furthermore, from the viewpoint of industrial applicability (productivity), the content may be 10 ppm or more, 30 ppm or more, or 50 ppm or more, based on 100% by mass of the total amount of the carrier. More specifically, the total content of each component containing chromium, manganese, iron, cobalt, nickel, and copper in the carrier is preferably within the above range, based on 100% by mass of the total amount of the carrier. The content can be measured, for example, by X-ray fluorescence (XRF) analysis.

[0093] The carbon dioxide absorbent can separate carbon dioxide not only from gases containing high concentrations of carbon dioxide, but also from dilute carbon dioxide in conditioned air and the atmosphere. Furthermore, by going through a process of desorption (removal) of the absorbed carbon dioxide, it is possible to recover the carbon dioxide and even reabsorb it. Therefore, by using the carbon dioxide absorbent, it is possible to suppress the decrease in carbon dioxide absorption and desorption capacity even after repeated absorption and desorption of carbon dioxide.

[0094] The carbon dioxide absorbent can be manufactured by known or conventional methods. Here, the carbon dioxide absorbent can be manufactured, for example, by mixing and stirring the above-mentioned components. Specifically, if the carbon dioxide absorbent contains the polyalkylene imine derivative of the present invention or the composition of the present invention and the carrier, the method for manufacturing the carbon dioxide absorbent preferably includes a step of mixing and stirring the polyalkylene imine derivative of the present invention or the composition of the present invention and the carrier to support the polyalkylene imine derivative of the present invention or the composition of the present invention on the carrier (supporting step). From the viewpoint of excellent handling and supportability, it is more preferable that the method for manufacturing the carbon dioxide absorbent includes a step of mixing and stirring a composition containing at least the polyalkylene imine derivative of the present invention and a solvent or the composition of the present invention and the carrier to support the polyalkylene imine derivative of the present invention on the carrier (supporting step). When using the composition of the present invention, the loading step may be a step of adding the composition of the present invention to the carrier and loading it (step (a)), or a step of adding each component contained in the composition of the present invention separately to the carrier and loading it (step (b)). From the viewpoint of superior manufacturing efficiency, step (a) is preferred as the loading step. In step (b), the order in which each component is added is not particularly limited.

[0095] The aforementioned supporting step can employ known or conventional methods. For example, the support may be made by impregnating the carrier with the polyalkyleneimine derivative or composition of the present invention (impregnation), by dropping the polyalkyleneimine derivative or composition of the present invention onto the carrier (dropping), or by filling the carrier into a container such as a column and then passing the polyalkyleneimine derivative or composition of the present invention through it (liquid passage). Among these, the impregnation method is preferred from the viewpoint of ease of operation and equipment.

[0096] The pressure conditions in the loading process are not particularly limited and can be arbitrarily selected from atmospheric pressure, reduced pressure, or increased pressure. If the carrier has pores, it is preferable to process it under reduced pressure from the viewpoint of removing air bubbles in the pores and efficiently loading it onto the carrier. The specific processing pressure is preferably 1 Pa to 100 Pa, more preferably 1 Pa to 50 Pa, and even more preferably 10 Pa to 30 Pa.

[0097] The temperature conditions in the loading process are not particularly limited, but from the viewpoint of excellent loading performance, 20°C to 90°C is preferred, more preferably 30°C to 80°C, and even more preferably 40°C to 70°C.

[0098] Furthermore, the method for producing the carbon dioxide absorbent may, if necessary, include a step of separating the excess solvent from the carrier on which the polyalkylene imine derivative of the present invention is supported (separation step), and / or a step of removing the solvent from the carrier (drying step).

[0099] The separation step can employ known or conventional methods, such as filtration, decantation, or centrifugation. Among these, filtration is preferred due to its ease of procedure.

[0100] The temperature conditions in the drying process are not particularly limited, but are preferably 30°C to 100°C, more preferably 40°C to 98°C, even more preferably 50°C to 95°C, and most preferably 50°C to 90°C.

[0101] The processing time in the drying step is not particularly limited, but is preferably 0.1 to 48 hours, more preferably 0.2 to 24 hours, and even more preferably 0.5 to 12 hours.

[0102] The pressure conditions in the drying process are not particularly limited and can be arbitrarily selected from atmospheric pressure, reduced pressure, or increased pressure. Among these, atmospheric pressure is preferred from the viewpoint of maintaining the state in which the polyalkylene imine derivative of the present invention is supported on the carrier.

[0103] The carbon dioxide absorbent can be installed and used in a device (carbon dioxide recovery device) that separates and recovers carbon dioxide from a gas to be treated that contains carbon dioxide. The gas to be treated is a carbon dioxide-containing gas that contains at least carbon dioxide, but may also contain other gases. Examples of the gas to be treated include the atmosphere, or high-concentration gases with a higher carbon dioxide concentration than the atmosphere. Such high-concentration gases are, for example, those emitted from internal combustion engines or factories.

[0104] Methods for using the carbon dioxide absorbent include a carbon dioxide separation method that includes a step of contacting the carbon dioxide absorbent with carbon dioxide in a gas (contact step), and a carbon dioxide recovery method that includes a step of desorbing the carbon dioxide from the carbon dioxide absorbent that has absorbed the carbon dioxide (desorption step). In the contact step, the carbon dioxide absorbent absorbs the carbon dioxide in the gas, so carbon dioxide can be removed (separated) from the gas. In the desorption step, carbon dioxide can be recovered by desorbing the carbon dioxide from the carbon dioxide absorbent.

[0105] The pressure conditions for the contact process may be, for example, 0.8 atmospheres to 1.1 atmospheres. The temperature conditions for the contact process may be, for example, -40°C to 50°C.

[0106] The pressure conditions for the de-attachment process may be, for example, under reduced pressure, or between 0.02 atmospheres and 0.5 atmospheres, or between 0.1 atmospheres and 0.3 atmospheres. The temperature conditions for the de-attachment process may be, for example, under heating, or between 50°C and 130°C.

[0107] The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to these examples. Unless otherwise specified below, "ppm", "%", and "parts" in this specification refer to "mass ppm", "mass %", and "mass parts".

[0108] [Synthesis Example] Synthesis Example 1 Polyalkyleneimine Derivative 1 (Methyl Chloride Method, Modification Rate 20% / Primary Amino Group) 100 parts by mass of polyethyleneimine (Epomin SP-006, manufactured by Nippon Shokubai Co., Ltd.) (equivalent to 0.70 mol of primary amino groups) were charged into a 300 mL autoclave equipped with a stirrer, and the temperature was raised to 90°C. 7.1 parts by mass (0.14 mol) of methyl chloride were injected under pressure, and the mixture was aged at the same temperature for 3 hours to obtain a reaction solution. 150 parts by mass of a 48% sodium hydroxide aqueous solution were further added to the obtained reaction solution, and the mixture was allowed to stand at 50°C or below to separate layers, thereby obtaining a composition (1) containing polyalkyleneimine derivative 1 as a colorless transparent liquid. Ion chromatography analysis of composition (1) showed that the amount of Cl ions was 300 ppm on a solid basis, and the amount of Na ions was 500 ppm on a solid basis. １ The substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 1, as measured by 1H-NMR, was 7%.

[0109] Synthesis Example 2 Polyalkyleneimine Derivative 2 (Methyl Chloride Method, Modification Rate 40% / Primary Amino Group) A composition (2) containing polyalkyleneimine derivative 2, which is a colorless, transparent liquid, was obtained in the same manner as in Synthesis Example 1, except that the amount of methyl chloride was changed from 7.1 parts by mass (0.14 mol) to 14.2 parts by mass (0.28 mol). The amount of Cl ions in composition (2), measured by ion chromatography, was 1200 ppm on a solid content basis, and the amount of Na ions was 100 ppm on a solid content basis. １ The substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 2, as measured by 1H-NMR, was 14%.

[0110] Synthesis Example 3 Polyalkyleneimine Derivative 3 (Formic Acid / Formalin Method, Denaturation Rate 20% / Primary Amino Group) 100 parts by mass of polyethyleneimine (Epomin SP-006, manufactured by Nippon Shokubai Co., Ltd.) (equivalent to 0.70 mol of primary amino groups) and 4.6 parts by mass (0.14 mol) of 92% paraformaldehyde were added to a 300 mL four-necked flask, and the mixture was heated to a predetermined temperature. After the paraformaldehyde had completely dissolved, 7.3 parts by mass (0.14 mol) of 88% formic acid aqueous solution were added dropwise, and the mixture was allowed to mature at the same temperature to obtain a composition (3) containing polyalkyleneimine derivative 3 as a transparent orange or brown liquid. The amount of Cl ions in composition (3), measured by ion chromatography, was 4600 ppm in terms of solid content. １ The substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 3, as measured by 1H-NMR, was 2%.

[0111] Synthesis Example 4 Polyalkyleneimine Derivative 4 (Formic Acid / Formalin Method, Denaturation Rate 60% / Primary Amino Group) A composition (4) containing polyalkyleneimine derivative 4, which is an orange or brown transparent liquid, was obtained in the same manner as in Synthesis Example 3, except that 30 parts by mass of ion-exchanged water was added as the reaction solvent, and the amount of 92% paraformaldehyde was changed to 13.7 parts by mass (0.42 mol) and the amount of 88% formic acid aqueous solution was changed to 21.8 parts by mass (0.42 mol). The amount of Cl ions in composition (4), measured by ion chromatography, was 4200 ppm in terms of solid content. １ The substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 4, as measured by 1H-NMR, was 9%.

[0112] Synthesis Example 5 Polyalkyleneimine Derivative 5 (Methyl Chloride Method, Modification Rate 60% / Primary Amino Group) A reaction solution was obtained in the same manner as in Synthesis Example 1, except that the amount of methyl chloride was changed from 7.1 parts by mass (0.14 mol) to 21.3 parts by mass (0.42 mol) and 100 parts by mass of 2-propanol was used as the solvent. 90.7 parts by mass of 28% sodium methoxide / methanol solution (0.47 mol as sodium methoxide) was further added to the obtained reaction solution, and a colorless, transparent liquid 2-propanol solution of polyalkyleneimine derivative 5 (composition (5)) was obtained by membrane filtration. Ion chromatography analysis of composition (5) showed that the amount of Cl ions was 400 ppm on a solid basis and the amount of Na ions was 15,000 ppm on a solid basis. １ The substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 5, as measured by 1H-NMR, was 18%.

[0113] Synthesis Example 6 Polyalkyleneimine Derivative 6 (Methyl Chloride Method, Modification Rate 60% / Primary Amino Group) A reaction solution was obtained in the same manner as in Synthesis Example 1, except that the amount of methyl chloride was changed from 7.1 parts by mass (0.14 mol) to 21.3 parts by mass (0.42 mol) and 100 parts by mass of 2-propanol was used as the solvent. The obtained reaction solution was diluted with 2-propanol, and 150 parts by mass of a 48% sodium hydroxide aqueous solution was further added. The mixture was allowed to stand at 50°C or below to separate the layers, thereby obtaining a colorless, transparent liquid 2-propanol solution of polyalkyleneimine derivative 6 (solid content 40.4%) (composition (6)). Composition (6) was measured by ion chromatography, and the amount of Cl ions was 6700 ppm on a solid content basis, and the amount of Na ions was 7000 ppm on a solid content basis. １ The substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 6, as measured by 1H-NMR, was 18%.

[0114] Synthesis Example 7 Ten parts of a solution (40.4% solids) of the polyalkylene imine derivative 6 obtained in Synthesis Example 6 were mixed with 1.8 parts of strongly basic anion exchange resin No. 8 (OH form) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., the OH form of a copolymer of styrene-ethylstyrene-divinylbenzene having a triethylamine functional group). After stirring for 1 hour, the ion exchange resin was filtered off. The obtained liquid was concentrated. Ion chromatography analysis of the obtained concentrate (composition (7)) showed that the amount of Cl ions was 800 ppm on a solids basis and the amount of Na ions was 4600 ppm on a solids basis.

[0115] Synthesis Example 8 Polyalkyleneimine Derivative 8 (Methyl Chloride Method, Modification Rate 60% / Primary Amino Group) The reaction solution obtained in the same manner as in Synthesis Example 6 was diluted with 2-propanol, and 300 parts by mass of a 48% sodium hydroxide aqueous solution was further added. The mixture was allowed to stand at 70°C or below to separate the layers, thereby obtaining a colorless, transparent liquid 2-propanol solution of polyalkyleneimine derivative 8 (solid content 34.3%) (Composition (8)). Ion chromatography analysis of the composition showed that the amount of Cl ions was 2600 ppm on a solid content basis, and the amount of Na ions was 1900 ppm on a solid content basis. １ The substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 8, as measured by 1H-NMR, was 18%.

[0116] Synthesis Example 9 Ten parts of a solution (34.3% solids) of polyalkylene imine derivative 8 obtained in Synthesis Example 8 were mixed with 0.2 parts of strongly basic anion exchange resin No. 8 (OH form) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., the OH form of a copolymer of styrene-ethylstyrene-divinylbenzene having a triethylamine functional group). After stirring for 1 hour, the ion exchange resin was filtered off. The obtained liquid was concentrated. Ion chromatography analysis of the obtained concentrate (composition (9)) showed that the amount of Cl ions was 800 ppm on a solids basis and the amount of Na ions was 1200 ppm on a solids basis.

[0117] Synthesis Example 10 Polyalkyleneimine Derivative 10 (Ethyl Iodide Method, Modification Rate 60% / Primary Amino Group) 100 parts by mass of polyethyleneimine (Epomin SP-006, manufactured by Nippon Shokubai Co., Ltd.) (equivalent to 0.70 mol of primary amino groups) and 100 parts by mass of 2-propanol were added to a 300 mL four-necked flask and mixed. Then, 65.5 parts by mass (0.42 mol) of ethyl iodide was added dropwise at a temperature of 30°C or below. The reaction solution was then aged at 30°C for 3 hours to obtain the reaction solution. Further dilution of the reaction solution with 2-propanol yielded a colorless, transparent liquid 2-propanol solution (solid content 30%) of polyalkyleneimine derivative 10.

[0118] Ten parts of the obtained solution (30% solids) and eleven parts of strongly basic anion exchange resin No. 8 (OH form) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., the OH form of a copolymer of styrene-ethylstyrene-divinylbenzene having a triethylamine functional group) were mixed and stirred for 6 hours, after which the ion exchange resin was filtered off. The obtained liquid was concentrated. Ion chromatography analysis of the obtained concentrate (composition (10)) showed that the amount of Cl ions was 2900 ppm on a solids basis, the amount of I ions was less than 10 ppm on a solids basis, and the amount of Na ions was 150 ppm on a solids basis, yielding a polyalkylene imine derivative 10. １ The substitution rate of ethyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imine derivative 10, as measured by 1H-NMR, was 18%.

[0119] [Examples] Using compositions containing the polyalkyleneimine derivatives obtained in Synthesis Examples 1 to 10 and polyethyleneimine (PEI) (Epomin SP-006, SP-012, manufactured by Nippon Shokubai Co., Ltd.; the substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms was 0% in all cases), carbon dioxide absorbents were prepared by the following method.

[0120] Example 1 A homogeneous solution was prepared by mixing 0.5 parts of composition (1) containing the polyalkylene imine derivative obtained in Synthesis Example 1 with 5.0 parts of water. Subsequently, 1.0 part of CARiACT G-10 (manufactured by Fuji Silysia Chemical Co., Ltd.) was added as a support and impregnated while stirring for 30 minutes. Subsequently, the material was treated under reduced pressure at 60°C and 20 Pa, and then heated and dried in an oven at 80°C for 2 hours to obtain a carbon dioxide absorbent material on which the polyalkylene imine derivative was supported.

[0121] Examples 2-9 and Comparative Examples 1-3 Composition (1) containing the polyalkyleneimine derivative obtained in Synthesis Example 1, Composition (2) containing the polyalkyleneimine derivative obtained in Synthesis Example 2, Composition (3) containing the polyalkyleneimine derivative obtained in Synthesis Example 3, Composition (4) containing the polyalkyleneimine derivative obtained in Synthesis Example 4, Composition (5) containing the polyalkyleneimine derivative obtained in Synthesis Example 5, Composition (6) containing the polyalkyleneimine derivative obtained in Synthesis Example 6, Composition (7) containing the polyalkyleneimine derivative obtained in Synthesis Example 7, Composition (8) containing the polyalkyleneimine derivative obtained in Synthesis Example 8, Composition (8) containing the polyalkyleneimine derivative obtained in Synthesis Example 9 Except for changing to composition (9) containing a real chilenimine derivative, composition (9) containing polyethyleneimine (PEI) (Epomin SP-006 manufactured by Nippon Shokubai Co., Ltd.; the substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms in PEI is 0%), composition (10) containing polyethyleneimine (PEI) (Epomin SP-012 manufactured by Nippon Shokubai Co., Ltd.), and composition (10) containing the polyalkyleneimine derivative obtained in Synthesis Example 10, carbon dioxide absorbers for Examples 2, 3, 4, 5, 6, 7, 8, 9, Comparative Example 1, Comparative Example 2, and Comparative Example 3 were obtained in the same manner as in Example 1.

[0122] [Evaluation Method] (1) Number average molecular weights of polyalkyleneimine derivative 1 contained in composition (1) of Synthesis Example 1, polyalkyleneimine derivative 2 contained in composition (2) of Synthesis Example 2, polyalkyleneimine derivative 3 contained in composition (3) of Synthesis Example 3, polyalkyleneimine derivative 4 contained in composition (4) of Synthesis Example 4, polyalkyleneimine derivative 5 contained in composition (5) of Synthesis Example 5, polyalkyleneimine derivative 6 contained in composition (6) of Synthesis Example 6, polyalkyleneimine derivative 8 contained in composition (8) of Synthesis Example 8, polyethyleneimine (PEI) (Epomin SP-006, SP-012 manufactured by Nippon Shokubai Co., Ltd.), and polyalkyleneimine derivative 10 contained in composition (10) of Synthesis Example 10 were measured under the following conditions and were found to be 631, 639, 634, 645, 626, 626, 626, 617, 1134, and 624, respectively.

[0123] Measurement equipment: GPC instrument (manufactured by Shimadzu Corporation) Column used: Resonax Shodex OHpak SB-807HQ (2 tubes) + SB-806M / HQ (2 tubes) Column temperature: 40°C Eluent: Aqueous solution prepared as 0.5 mol% sodium nitrate and 0.5 mol% acetic acid Standard substance: Shodex STANDARD P-82 (manufactured by Resonax Corporation) Detector: Differential refractometer (manufactured by Shimadzu Corporation)

[0124] (2) Analysis of chloride ion and sodium ion content (ion chromatography) Ion chromatography was performed under the following conditions to calculate the amount of chloride ions (mass ppm) (on a solid basis) and sodium ions (mass ppm) (on a solid basis) relative to the amount of polyalkylene imine derivative in the compositions containing polyalkylene imine derivatives of Synthesis Examples 1 to 10. In addition, the amount of chloride ions (mass ppm) (on a solid basis) and sodium ions (mass ppm) (on a solid basis) relative to the amount of polyethyleneimine (PEI) in the compositions containing polyethyleneimine (PEI) (Epomin SP-006 and Epomin SP-012 manufactured by Nippon Shokubai Co., Ltd.) was calculated. The calculation results are shown in the columns for chloride ion amount (mass ppm) and sodium ion amount (mass ppm) for the corresponding examples and comparative examples in Tables 1 and 2.

[0125] Equipment: Dionex® ICS-2000 (manufactured by Thermo Fisher Scientific K.K.) Detector: Conductivity detector Column: Dionex® IonPac® AS-18 (manufactured by Thermo Fisher Scientific K.K.) (for chloride ions) Column: Dionex® IonPac® CS-16 (manufactured by Thermo Fisher Scientific K.K.) (for sodium ions) Guard column: Dionex® IonPac® AG-18 (manufactured by Thermo Fisher Scientific K.K.) (for chloride ions) Guard column: Dionex® IonPac® CG-16 (manufactured by Thermo Fisher Scientific K.K.) (for sodium ions) Column temperature: 30°C Eluent: KOH aqueous solution (15 mmol / L) (for chloride ions) Eluent: Methanesulfonic acid aqueous solution (15 mmol / L) (for sodium ions) Flow rate: 0.9 mL / min Injection volume: 25 μL

[0126] (3) Carbon dioxide adsorption and desorption test using carbon dioxide-containing gas simulating dry air 1 The amount of carbon dioxide adsorbed and desorbed for each carbon dioxide absorbent was measured by the following test.

[0127] A differential thermal-thermogravimetric analyzer (TG-DTA) (TG-DTA8120, 8122, manufactured by Rigaku Corporation) will be used to measure the mass at the absorption temperature (40°C) and the desorption temperature (75°C). The sample will be held at the absorption temperature for 120 minutes and at the desorption temperature for 60 minutes. A carbon dioxide-containing gas, with its nitrogen and carbon dioxide flow rates adjusted using a mass flow controller, will be supplied to the TG-DTA oven at a rate of 200 ml / min. The carbon dioxide concentration of the simulated gas will be kept constant at approximately 400 ppm, and the humidity of the supplied gas will be kept constant at an absolute humidity of 2 g / kg.

[0128] The amount of solid absorbent material during carbon dioxide absorption and the amount of solid absorbent material during carbon dioxide desorption by heating are measured from TG-DTA measurements, and the amount of carbon dioxide absorption and desorption is calculated from the following formula: Amount of carbon dioxide absorption and desorption (g / g) = (W Ａ -W Ｄ ) / W １ WＡ : Mass (g) of carbon dioxide absorbent at absorption temperature W Ｄ : Mass of carbon dioxide absorbent at desorption temperature (g) W １ : Mass (g) of the carbon dioxide absorbent used in the test

[0129] (a) Amount of carbon dioxide adsorption and desorption of carbon dioxide absorbent without degradation treatment The carbon dioxide adsorption and desorption test described above was performed on each carbon dioxide absorbent (without degradation treatment) and the amount of carbon dioxide adsorption and desorption was measured. The amount of carbon dioxide adsorption and desorption at this time is shown in Tables 1 and 2 below as "CO ２ This is shown in the "Initial" section of the "Absorption Amount (g / g)" item. Furthermore, hereafter, the amount of carbon dioxide absorbed and desorbed at this time will also be referred to as the amount of carbon dioxide absorbed and desorbed without degradation treatment.

[0130] (b) Amount of carbon dioxide adsorption and desorption of carbon dioxide absorbent after degradation treatment (oxidation resistance) For each carbon dioxide absorbent, degradation treatment 1 or 2 described below was applied, and then the carbon dioxide adsorption and desorption test was performed on each carbon dioxide absorbent (after degradation treatment 1 or 2), and the amount of carbon dioxide adsorption and desorption was measured. Using the obtained amount of carbon dioxide adsorption and desorption, the maintenance rate after degradation treatment 1 or 2 was calculated from the following calculation formula.

[0131] Degradation Treatment 1 Each carbon dioxide absorbent obtained in the above examples and comparative examples was weighed to 0.03 g each into a 10 mL vial. The top of each vial was protected with weighing paper that had several holes punched in it to prevent contamination with foreign matter while allowing air to pass through. After standing in a 100°C oven for 24 hours, the vial was cooled to obtain carbon dioxide absorbent that had undergone degradation treatment. This treatment causes the carbon dioxide absorbent to undergo oxidative degradation, thus mimicking absorbents that have undergone heating or repeated adsorption / desorption treatments. The amount of carbon dioxide adsorbed and desorbed after treatment by degradation treatment 1 is shown in Tables 1 and 2 below as "CO ２ The amount absorbed (g / g) is shown in the section "After heating at 100°C for 24 hours".

[0132] Degradation treatment 2 was performed under the same conditions as degradation treatment 1, except that the 24-hour treatment was changed to 48 hours. The amount of carbon dioxide absorbed and desorbed after treatment by degradation treatment 2 is shown in Tables 1 and 2 below as "CO ２The amount absorbed (g / g) is shown in the section "After heating at 100°C for 48 hours".

[0133] Formula for calculating the retention rate after degradation treatment 1: Retention rate after degradation treatment 1 (%) = [(Amount of carbon dioxide adsorption / desorption after degradation treatment 1) / (Amount of carbon dioxide adsorption / desorption without degradation treatment)] × 100

[0134] In Tables 1 and 2 below, the retention rate (%) after degradation treatment 1 is denoted as "Retention Rate 1 (100°C 24h / Initial)".

[0135] Maintenance rate after degradation treatment 2 (%) = [(Amount of carbon dioxide adsorption / desorption after degradation treatment 2) / (Amount of carbon dioxide adsorption / desorption without degradation treatment)] × 100

[0136] In Tables 1 and 2 below, the retention rate (%) after degradation treatment 2 is denoted as "Retention Rate 2 (100°C 48h / Initial)".

[0137]

[0138]

[0139] (4) Carbon dioxide adsorption and desorption test 2 using carbon dioxide-containing gas simulating dry air The amount of carbon dioxide adsorbed and desorbed was measured for each carbon dioxide absorbent in Examples 1, 2, and 5 and Comparative Examples 1 and 2, under the same conditions as in Carbon Dioxide Adsorption and Desorption Test 1, except that the desorption temperature (75°C) was sequentially set to predetermined temperatures (58, 65, 75, 85, 95°C) and degradation treatment 2 was not performed. The results are shown in Table 3 below.

[0140]

[0141] Table 1 shows that Examples 1 and 2 have an initial carbon dioxide absorption amount (carbon dioxide absorption amount without degradation treatment) that is equal to or greater than that of Comparative Examples 1 and 2, and Tables 1 and 2 show that all examples have higher oxidation resistance (carbon dioxide absorption capacity retention rate after degradation treatment 1) compared to Comparative Examples 1 and 2. Also, Table 1 shows that Example 2 has a higher initial carbon dioxide absorption amount and higher oxidation resistance (carbon dioxide absorption capacity retention rate after degradation treatments 1 and 2) than Example 1. Furthermore, Example 5 has particularly high oxidation resistance (carbon dioxide absorption capacity retention rate after degradation treatment 1 or 2). From these findings, it was found that the substitution of methyl groups on hydrogen atoms bonded to nitrogen atoms in polyalkylene imines contributes to improving the carbon dioxide absorption capacity retention rate after degradation treatment, that the lower the substitution rate (e.g., 15% or less), the more the initial carbon dioxide absorption capacity is equal to or greater than that of polyalkylene imines in which hydrogen atoms bonded to nitrogen atoms are not substituted, and that the higher the substitution rate (e.g., 10% or more), the more the carbon dioxide absorption capacity retention rate after degradation treatment improves. Furthermore, a comparison of all examples with Comparative Example 3 in Tables 1 and 2 revealed that when the hydrogen atoms bonded to the nitrogen atoms in the polyalkylene imine are substituted with methyl groups, the initial carbon dioxide absorption capacity is superior compared to when the hydrogen atoms bonded to the nitrogen atoms in the polyalkylene imine are substituted with ethyl groups.

[0142] Furthermore, a comparison of Examples 1, 2, 5, and 7-9, prepared using compositions in which the amount of halogen ions relative to the amount of polyalkylene imine derivative was less than 4500 ppm by mass, as shown in Tables 1 and 2, with Comparative Examples 1 and 2, prepared using compositions in which the amount of halogen ions relative to the amount of polyalkylene imine derivative was 4500 ppm by mass or more, revealed that a low concentration of halogen ions contributes to improving the oxidation resistance (maintenance rate of carbon dioxide absorption capacity after degradation treatment 1) of the carbon dioxide absorber. Furthermore, from Example 6, it was found that even when a composition was prepared using a composition in which the amount of halogen ions relative to the amount of polyalkyleneimine derivative was 4500 ppm by mass or more, if the amount of halogen ions relative to the amount of polyalkyleneimine derivative (ppm by mass) was less than the total amount of alkali metal ions and alkaline earth metal ions relative to the amount of polyalkyleneimine derivative (ppm by mass), then, as with the other examples, the oxidation resistance (retention rate of carbon dioxide absorption capacity after degradation treatment 1) was improved compared to Comparative Examples 1 and 2, and the initial carbon dioxide absorption capacity was superior to that of Comparative Example 3, which used a polyalkyleneimine derivative in which the hydrogen atoms were substituted with ethyl groups.

[0143] Table 3 shows that Examples 1, 2, and 5, compared to Comparative Examples 1 and 2, had higher carbon dioxide desorption amounts (g / g) at low temperatures of 58°C and 65°C, respectively, with 40°C after degradation treatment 1 as the baseline, indicating superior low-temperature desorption ability and oxidation resistance (retention rate of carbon dioxide absorption capacity after degradation treatment).

[0144] Furthermore, a comparison of Example 1 with Examples 2 and 5 in Table 3 revealed that Examples 2 and 5 exhibited higher carbon dioxide desorption amounts (g / g) at low temperatures of 58°C to 95°C, particularly 58°C and 65°C, relative to 40°C, both initially and after degradation treatment 1, demonstrating superior low-temperature desorption capabilities.

[0145] These findings indicate that the substitution of a methyl group with a hydrogen atom bonded to a nitrogen atom in polyalkylene imines contributes to low-temperature desorption ability, and that the higher the substitution rate (e.g., 10% or more), the better the low-temperature desorption ability.

[0146] The following describes variations of the invention according to the present invention. [Note 1] A polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom. [Note 2] The polyalkyleneimine derivative according to Note 1, wherein the substitution rate of the methyl group on the hydrogen atom bonded to the nitrogen atom is greater than 0% and less than or equal to 100%. [Note 3] The polyalkyleneimine derivative according to Note 1 or 2, wherein the number average molecular weight is 250 to 10000. [Note 4] A composition comprising a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, and further comprising a composition in which the amount of halogen ions is less than 4500 ppm by mass relative to the amount of the polyalkyleneimine derivative. [Note 5] A composition comprising a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, wherein the amount of halogen ions (mass ratio) relative to the amount of the polyalkyleneimine derivative in the composition is less than the total amount (mass ratio) of alkali metal ions and alkaline earth metal ions relative to the amount of the polyalkyleneimine derivative in the composition. [Note 6] A method for producing a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, comprising a methylation step of substituting a hydrogen atom bonded to the nitrogen atom of the polyalkyleneimine with a methyl group. [Note 7] The method for producing a polyalkyleneimine derivative according to Note 6, wherein the methylation step is a step of reacting the polyalkyleneimine with a methyl halide. [Note 8] The method for producing a polyalkyleneimine derivative according to Note 6, wherein the methylation step is a step of reacting the polyalkyleneimine with formalin and formic acid. [Note 9] A method for producing a composition containing a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, comprising the purification step described below. Purification step: A step of reducing the amount of halogen ions in a composition in which the amount of halogen ions relative to the amount of polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom is 4500 ppm by mass or more to less than 4500 ppm by mass. [Note 10] A carbon dioxide absorbent comprising a carrier and a polyalkyleneimine derivative according to any one of Notes 1 to 3 or a polyalkyleneimine derivative contained in the composition according to Note 4 or 5, supported on the carrier.

Claims

1. Polyalkylene imine derivatives containing a bond between a methyl group and a nitrogen atom.

2. The polyalkylene imine derivative according to claim 1, wherein the substitution rate of methyl groups on hydrogen atoms bonded to nitrogen atoms is greater than 0% and less than or equal to 100%.

3. The polyalkyleneimine derivative according to claim 1, wherein the number average molecular weight is 250 to 10,000.

4. A composition comprising a polyalkyleneimine derivative containing a bond between a methyl group and a nitrogen atom, wherein the amount of halogen ions in the composition is less than 4500 ppm by mass relative to the amount of the polyalkyleneimine derivative.

5. A composition comprising a polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom, wherein the amount of halogen ions (mass ratio) relative to the amount of the polyalkyleneimine derivative in the composition is less than the total amount (mass ratio) of alkali metal ions and alkaline earth metal ions relative to the amount of the polyalkyleneimine derivative in the composition.

6. A method for producing a polyalkylene imine derivative containing a bond between a methyl group and a nitrogen atom, comprising a methylation step of substituting a hydrogen atom bonded to the nitrogen atom of the polyalkylene imine with a methyl group.

7. The method for producing a polyalkylene imine derivative according to claim 6, wherein the methylation step is a step of reacting a polyalkylene imine with a methyl halide.

8. The method for producing a polyalkyleneimine derivative according to claim 6, wherein the methylation step is a step of reacting the polyalkyleneimine with formalin and formic acid.

9. A method for producing a composition containing a polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom, comprising the following purification step: Purification step: A step of reducing the amount of halogen ions in a composition where the amount of halogen ions relative to the amount of polyalkyleneimine derivative having a bond between a methyl group and a nitrogen atom is 4500 ppm by mass or more to less than 4500 ppm by mass.

10. A carbon dioxide absorbent comprising a carrier and a polyalkyleneimine derivative according to any one of claims 1 to 3 or a polyalkyleneimine derivative contained in the composition according to claim 4 or 5, supported on the carrier.

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