Method for producing onium salt and method for purifying onium salt

Abstract

To provide a method for producing an onium salt that does not contain carboxylic acid, or an onium salt in which a content of carboxylic acid is reduced to an extent capable of obtaining a sufficient solubility of cellulose relative to the onium salt.SOLUTION: A method for obtaining an onium salt from a mixture containing the onium salt and a carboxylic acid, comprises the following steps (1), (2), and (3): Step (1): A step for obtaining a mixture containing an onium salt and a carboxylic acid. Step (2): A step for adding an amine to the mixture containing the onium salt and carboxylic acid to produce an amine-carboxylate salt from the amine and carboxylic acid. Step (3): A step for separating the onium salt from the amine-carboxylate salt generated in step (1) to obtain the onium salt.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing an onium salt and a method for purifying an onium salt. [Background technology]

[0002] Polysaccharides are substances in which many monosaccharide molecules are polymerized through glycosidic bonds. Among them, cellulose, a polysaccharide composed of β-glucose molecules, is the most abundant biomass resource on earth, and as an environmentally friendly material, research on dissolving, molding, etc. is being widely conducted. However, cellulose has strong hydrogen bonds between and within its molecular chains, making it difficult to dissolve in general solvents.

[0003] Onium salts have been proposed as solvents for dissolving cellulose, and Patent Document 1 describes a method for dissolving cellulose using a molten ionic liquid consisting of a 1-alkyl-3-methylimidazolium cation and an acetate anion.

[0004] Patent Document 2 describes a method for producing a quaternary ammonium organic acid salt, which comprises producing a quaternary ammonium carbonate, mixing the produced quaternary ammonium carbonate with an organic acid, and carrying out anion exchange with the organic acid. The method describes a method for producing a quaternary ammonium organic acid salt, which comprises producing a quaternary ammonium carbonate using a nitrogen-containing heterocyclic aromatic compound such as N-methylimidazole or N-methylbenzimidazole as a raw material, mixing it with acetic acid as the organic acid, and carrying out anion exchange.

[0005] Patent Document 3 describes a method for producing a quaternary ammonium carboxylate, characterized by reacting a quaternary ammonium alkyl carbonate with a carboxylic acid, and in the examples, it describes the reaction of N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium methyl carbonate with methoxyacetic acid to obtain N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium methoxyacetate.

[0006] Non-Patent Document 1 describes a one-pot synthesis method for a mixture of 1,3-dialkylimidazolium acetate (when R1 and R2 are the same) and 1-alkyl-3-methylimidazolium acetate, 1,3-dialkylimidazolium acetate, and 1,3-dimethylimidazolium acetate (when R1 is a methyl group and R1 and R2 are different), as shown in the following scheme. It also describes that colored impurities are removed by passing the ionic liquid, such as imidazolium acetate, through a decolorizing charcoal column. [ka]

[0007] Non-Patent Document 2 describes a method for separating acetic acid from a synthetic mixture containing 1-ethyl-3-methylimidazolium acetate, which is an ionic liquid. The separation methods described include evaporating acetic acid as a volatile component from a mixture containing 1-ethyl-3-methylimidazolium acetate, extracting acetic acid with a solvent that is immiscible with 1-ethyl-3-methylimidazolium acetate, and adding methanol to a mixture containing 1-ethyl-3-methylimidazolium acetate to esterify acetic acid and then removing methyl acetate by distillation. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Special Publication No. 2005-506401 [Patent Document 2] Japanese Patent Publication No. 63-280045 [Patent Document 3] JP 2015-83545 A [Non-patent literature]

[0009] [Non-Patent Document 1] Pure Appl. Chem., Vol.84, No.3, pp.745-754, 2012 [Non-Patent Document 2] J. Chem. Eng. Data 2013, 58, 197-202 Summary of the Invention [Problem to be solved by the invention]

[0010] In the method for producing a quaternary ammonium carboxylate, which is an ionic liquid and an onium salt, described in the prior art, the carboxylic acid used remains in the quaternary ammonium carboxylate product. The remaining carboxylic acid forms an association with the produced quaternary ammonium carboxylate, and when the quaternary ammonium carboxylate containing the association is used to dissolve cellulose, the solubility of cellulose in the quaternary ammonium carboxylate decreases.

[0011] In the context of such prior art, an object of the present invention is to provide a method for producing an onium salt that does not contain a carboxylic acid, or an onium salt in which the carboxylic acid content is reduced to such an extent that sufficient solubility of cellulose in the onium salt can be obtained. Another object of the present invention is to provide a method for purifying an onium salt, which removes a carboxylic acid contained in the onium salt or reduces the content of the carboxylic acid to an extent that sufficient solubility of cellulose in the onium salt can be obtained. [Means for solving the problem]

[0012] The present inventors have conducted extensive research into a method for producing an onium salt that does not contain carboxylic acid or an onium salt in which the carboxylic acid content is reduced to such an extent that sufficient solubility of cellulose in the onium salt is obtained, and a method for purifying the onium salt, and have completed the present invention.

[0013] That is, the present invention provides the following [1] to

[10] . [1] A method for producing an onium salt represented by the following formula (1), comprising the following steps (1), (2) and (3). Formula (1): [ka] (In formula (1), R 3 , R 4 , R 5 R may be the same or different and represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 1 , R 2 R may be the same or different and represents a hydrocarbon group which may contain a heteroatom. 1 , R 2 may contain branched and / or cyclic structures and / or double bonds, R 1 , R 2 , R 3 , R 4 and R 5 Part or all of R 1 , R 2 , R 3 , R 4 and R 5 may be bonded together with the nitrogen atom and carbon atom to which they are attached to form a ring structure. In addition, in formula (1), R 6 represents a hydrocarbon group which may contain a heteroatom, and which may contain a double bond and / or a ring structure and / or a branched structure. Process (1): A step of obtaining a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3) below, which is obtained by the reaction represented by formula (2) below. Formula (2): [ka] Formula (3): [ka] (In formula (3), R 6 represents a hydrocarbon group which may contain a heteroatom, and which may contain a double bond and / or a ring structure and / or a branched structure. Process (2): A step of adding an amine to a mixture containing the onium salt represented by formula (1) obtained in step (1) and the carboxylic acid of formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid of formula (3). Process (3): A step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2) to obtain the onium salt represented by formula (1). [2] The method for producing an onium salt according to [1], wherein the amine added in the step (2) is an amine represented by the following formula (4): Formula (4): [ka] (In formula (4), R 7 , R 8 and R 9 may be the same or different and are a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and the hydrocarbon group may contain a double bond and may contain a branched structure and / or a ring structure. 7 , R 8 and R 9 The total number of carbon atoms in each of these is 8 or more.) [3] The method for producing an onium salt according to [1], wherein the onium salt represented by formula (1) is of at least two types. [4] The method for producing an onium salt according to [1], wherein the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) further contains water and / or a hydrophilic solvent. [5] The method for producing an onium salt according to [1], wherein the amine added in step (2) is an amine solution diluted with a solvent. [6] A method for purifying an onium salt represented by the following formula (1), which comprises removing a carboxylic acid of the following formula (3) from a mixture containing the onium salt represented by the following formula (1) and a carboxylic acid of the following formula (3), the method comprising the following steps (1), (2) and (3): Formula (1): [ka] (In formula (1), R 3 , R 4 , R 5 R may be the same or different and represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 1 , R 2 R may be the same or different and represents a hydrocarbon group which may contain a heteroatom. 1 , R 2 may contain branched and / or cyclic structures and / or double bonds, R 1 , R 2 , R 3 , R 4 and R 5 Part or all of R 1 , R 2 , R 3 , R 4 and R 5 may be bonded together with the nitrogen atom and carbon atom to which they are attached to form a ring structure. In addition, in formula (1), R 6 represents a hydrocarbon group which may contain a heteroatom, and which may contain a double bond and / or a ring structure and / or a branched structure. Process (1): A step of obtaining a mixture containing the onium salt of formula (1) and the carboxylic acid of formula (3) by the reaction of formula (2). Formula (2): [ka] Formula (3): [ka] (In formula (3), R 6 represents a hydrocarbon group which may contain a heteroatom, and which may contain a double bond and / or a ring structure and / or a branched structure. Process (2): A step of adding an amine to the mixture containing the onium salt of formula (1) obtained in step (1) and the carboxylic acid of formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid of formula (3). Process (3): A step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2) to obtain the onium salt represented by formula (1). [7] The method for purifying an onium salt according to [6], wherein the amine added in the step (2) is an amine represented by the following formula (4): Formula (4): [ka] (In formula (4), R 7 , R 4 and R 9 may be the same or different and are a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and the hydrocarbon group may contain a double bond and may contain a branched structure and / or a ring structure. 7 , R 8 and R 9 The total number of carbon atoms in each of these is 8 or more.) [8] The method for purifying an onium salt according to [6], wherein the onium salt represented by formula (1) is of at least two kinds. [9] The method for purifying an onium salt according to [6], wherein the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) further contains water and / or a hydrophilic solvent.

[10] The method for purifying an onium salt according to [6], wherein the amine added in the step (2) is an amine solution diluted with a solvent. Effect of the Invention

[0014] According to the present invention, a method for producing an onium salt that does not contain carboxylic acid or an onium salt in which the content of carboxylic acid is reduced to such an extent that sufficient solubility of cellulose in the onium salt can be obtained can be provided. Also, according to the present invention, a method for purifying an onium salt can be provided that removes carboxylic acid contained in the onium salt or reduces the content of carboxylic acid to such an extent that sufficient solubility of cellulose in the onium salt can be obtained. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be specifically described below. One embodiment of the present invention relates to a method for producing an onium salt represented by the following formula (1), which includes the following steps (1), (2), and (3). Formula (1): [ka] (In formula (1), R 3 , R 4 , R 5 R may be the same or different and represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 1 , R 2 R may be the same or different and represents a hydrocarbon group which may contain a heteroatom. 1 , R 2 may contain branched and / or cyclic structures and / or double bonds, R 1 , R 2 , R 3 , R 4 and R 5 Part or all of R 1 , R 2 , R 3 , R 4 and R 5 may be bonded together with the nitrogen atom and carbon atom to which they are attached to form a ring structure. In addition, in formula (1), R 6 represents a hydrocarbon group which may contain a heteroatom, and which may contain a double bond and / or a ring structure and / or a branched structure. Process (1): A step of obtaining a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3) below, which is obtained by the reaction represented by formula (2) below. Formula (2): [ka] Formula (3): [ka] (In formula (3), R6 represents a hydrocarbon group which may contain a heteroatom, and which may contain a double bond and / or a ring structure and / or a branched structure. Process (2): A step of adding an amine to a mixture containing the onium salt represented by formula (1) obtained in step (1) and the carboxylic acid of formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid of formula (3). Process (3): A step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2) to obtain the onium salt represented by formula (1).

[0016] The onium salt represented by the following formula (1) is an imidazolium carboxylate consisting of an imidazolium cation and a carboxylate anion. Formula (1): [ka] (In formula (1), R 3 , R 4 , R 5 R may be the same or different and represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 1 , R 2 R may be the same or different and represents a hydrocarbon group which may contain a heteroatom. 1 , R 2 may contain branched and / or cyclic structures and / or double bonds, R 1 , R 2 , R 3 , R 4 and R 5 Part or all of R 1 , R 2 , R 3 , R 4 and R 5 may be bonded together with the nitrogen atom and carbon atom to which they are attached to form a ring structure. In addition, in formula (1), R 6 represents a hydrocarbon group which may contain a heteroatom, and which may contain a double bond and / or a ring structure and / or a branched structure.

[0017] In formula (1), the imidazolium cation represented by the following formula (1-1) will be described. Formula (1-1): [ka] (In formula (1-1), R 3 , R 4 , R 5 R may be the same or different and represents a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms. 1 , R 2 R may be the same or different and represents a hydrocarbon group which may contain a heteroatom. 1 , R 2 may contain branched and / or cyclic structures and / or double bonds, R 1 , R 2 , R 3 , R 4 and R 5 Part or all of R 1 , R 2 , R 3 , R 4 and R 5 may be bonded together with the nitrogen atom and carbon atom to which they are bonded to form a ring structure.

[0018] In formula (1-1), R 1 , R 2 represents a hydrocarbon group which may contain a heteroatom. The "hydrocarbon group which may contain a heteroatom" may be linear, branched and / or containing a ring structure and / or a double bond. R 1 , R 2 In the above formula, the hydrocarbon group does not necessarily contain a heteroatom.

[0019] In formula (1-1), R 1 , R 2 When R is a hydrocarbon group containing no heteroatom, it preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and further preferably 1 to 3 carbon atoms. 1 , R 2 When is a hydrocarbon group containing a hetero atom, it preferably has 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 2 to 4 carbon atoms.

[0020] In formula (1-1), R 1 , R 2 When it contains a heteroatom, the number of heteroatoms is preferably 1 to 5, and more preferably 1 to 2. The number of carbon atoms in the hydrocarbon group is 2 or more, preferably 2 to 12, more preferably 2 to 8, and further preferably 2 to 4.

[0021] In formula (1-1), R 1 , R 2 When is a hydrocarbon group containing a heteroatom, examples of the "heteroatom" include a nitrogen atom, an oxygen atom, a sulfur atom, etc. The number of heteroatoms is preferably 1 to 5, and more preferably 1 to 2.

[0022] In formula (1-1), R 1 , R 2 In the above, a "hydrocarbon group containing a heteroatom" refers to a hydrocarbon group not containing a heteroatom, in which (i) the bond between two adjacent carbon atoms and / or (ii) the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of another -CH2- (methylene group) are bonded together such that -O-, -N<, -NH-, -S-, -C(=O)-O-, -C(=O)-, =N-, -C(=O)-N<, -C(=O)-NH-, -OC(=O)-O-, -OC(=O)-N<, -OC(=O)-NH-, -C(=O)- N[-C(=O)-]-, -C(=O)-NH-C(=O)-, >NC(=O)-N<, >NC(=O)-NH-, -HN-C(=O)-NH-, -S(=O)-, -S(=O)2-, -S(=O)2-O-, -OS(=O)2-O-, >NC(=S)-N<, >NC(=S)-NH-, -HN-C(=S)-NH-, -C(=N-)-, -C(=NH)-, and the like are substituted with structures such as these. The number and combination of substitutions with these structures are not particularly limited. 1 , R 2 The number of heteroatoms therein is preferably 1 to 5, and more preferably 1 or 2.

[0023] Preferably, (i) the bond between two adjacent carbon atoms and / or (ii) the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of the other -CH2- (methylene group) are replaced by an -O- or -S- structure, more preferably by an -O- structure.

[0024] In the present invention, the structure in which (i) the bond between two adjacent carbon atoms and / or (ii) the hydrogen atom of one -CH2- (methylene group) of a hydrocarbon group is replaced with a -O- or -S- structure may be an ether structure, a thioether structure, or an epoxy structure or thioepoxy structure such as an epoxy group, a thioepoxy group, a glycidyl ether group, or an epoxycyclohexyl group. In this case, R 1 , R 2 may be an epoxy group, a thioepoxy group, or the like.

[0025] R 1 , R 2 When the compound contains two or more -O- and / or -S- structures, the number of carbon atoms between the -O- and / or -S- structures is desirably two or more.

[0026] In formula (1-1), R 1 , R 2In the above, examples of the "hydrocarbon group which may contain a heteroatom" include a linear or branched alkyl group which may contain a heteroatom, a linear or branched alkenyl group which may contain a heteroatom, a linear or branched alkynyl group which may contain a heteroatom, a cycloalkyl group which may contain a heteroatom and may be branched, a cycloalkenyl group which may contain a heteroatom and may be branched, an aryl group which may contain a heteroatom and may be branched, an aralkyl group which may contain a heteroatom and may be branched, etc. Preferred are a linear or branched alkyl group which may contain a heteroatom, a linear or branched alkenyl group which may contain a heteroatom, and a cycloalkyl group which may contain a heteroatom and may be branched.

[0027] The "linear or branched alkyl group which may contain a heteroatom" is preferably a linear or branched alkyl group having 1 to 12 carbon atoms which may contain 1 to 5 heteroatoms. In another embodiment, it is preferably a linear or branched alkyl group having 1 to 12 carbon atoms which may contain 1 to 2 heteroatoms, more preferably a linear or branched alkyl group having 1 to 8 carbon atoms which may contain 1 to 2 heteroatoms, and even more preferably a linear or branched alkyl group having 1 to 4 carbon atoms which may contain 1 to 2 heteroatoms. In yet another embodiment, it is preferably a linear or branched alkyl group having 1 to 12 carbon atoms, more preferably a linear or branched alkyl group having 1 to 8 carbon atoms, and even more preferably a linear or branched alkyl group having 1 to 3 carbon atoms.

[0028] The "linear or branched alkenyl group which may contain a heteroatom" is preferably a linear or branched alkenyl group having 2 to 12 carbon atoms which may contain 1 to 5 heteroatoms. In another embodiment, it is preferably a linear or branched alkenyl group having 2 to 12 carbon atoms which may contain 1 to 2 heteroatoms, more preferably a linear or branched alkenyl group having 2 to 8 carbon atoms which may contain 1 to 2 heteroatoms, and even more preferably a linear or branched alkenyl group having 2 to 4 carbon atoms which may contain 1 to 2 heteroatoms. In yet another embodiment, it is preferably a linear or branched alkenyl group having 2 to 12 carbon atoms, more preferably a linear or branched alkenyl group having 2 to 8 carbon atoms, and even more preferably a linear or branched alkenyl group having 2 to 3 carbon atoms.

[0029] The "cycloalkyl group which may contain a heteroatom or may have a branch" is preferably a cycloalkyl group having 3 to 12 carbon atoms which may contain 1 to 5 heteroatoms and which may have a branch. In another embodiment, it is preferably a cycloalkyl group having 3 to 12 carbon atoms which may contain 1 to 2 heteroatoms and which may have a branch, more preferably a cycloalkyl group having 3 to 8 carbon atoms which may contain 1 to 2 heteroatoms and which may have a branch, and even more preferably a cycloalkyl group having 3 to 4 carbon atoms which may contain 1 to 2 heteroatoms. In yet another embodiment, it is preferably a cycloalkyl group having 3 to 12 carbon atoms which may have a branch, more preferably a cycloalkyl group having 3 to 8 carbon atoms which may have a branch, and even more preferably a cycloalkyl group having 3 carbon atoms.

[0030] In formula (1-1), R 1 , R 2In the above, specific examples of the "hydrocarbon group not containing a hetero atom" include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a vinyl group, an ethynyl group, a propenyl group, an isopropenyl group, an allyl group, a propargyl group, a butenyl group, a crotyl group, a butadienyl group, a cyclopropyl group, a cyclobutyl ... Examples of the aryl group include a methyl group, an ethyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, a phenyl group, a benzyl group, a tolyl group, a styryl group, and a 2,4,6-trimethylphenyl group. Of these, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group are preferred, and a methyl group, an ethyl group, a propyl group, an isopropyl group, and a tert-butyl group are more preferred.

[0031] In formula (1-1), R 1 , R 2 In the above, the "hydrocarbon group containing a hetero atom" is preferably a 3-indolyl group, a p-methoxyphenyl group, a 7-oxabicyclo[2,2,1]hept-5-en-2-yl group, a 1,2-epoxyethyl group, a 1-methyl-2-methoxyvinyl group, a 2-furyl group, a 2-pyridyl group, a 4-imidazolyl group, or a benzyloxymethyl group, and more preferably a 1-methyl-2-methoxyvinyl group or a 2-furyl group, although the present invention is not limited thereto.

[0032] In formula (1-1), R 3 , R 4 and R 5 is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

[0033] In formula (1-1), R 1 , R 2 , R 3 , R 4 and R 5may be bonded together with the nitrogen atom or carbon atom to which they are attached to form a ring structure. 1 and R 3 , R 3 and R 2 , R 2 and R 5 , R 5 and R 4 , or R 1 and R 4 Examples of such structures include, but are not limited to, a cyclic structure formed by linking the ring structure with a hydrocarbon having 2 to 24 carbon atoms and containing 2 to 10 heteroatoms.

[0034] In the formula (1-1), specific examples of imidazolium having a hydrocarbon group not containing a hetero atom include 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-methyl-3-propylimidazolium, 1-butyl-3-methylimidazolium, 1-methyl-3-pentylimidazolium, 1-hexyl-3-methylimidazolium, 1-heptyl-3-methylimidazolium, 1- Examples of the imidazolium salt include methyl-3-octylimidazolium, 1-methyl-3-nonylimidazolium, 1-decyl-3-methylimidazolium, 1-allyl-3-methylimidazolium, and 1-allyl-3-ethylimidazolium. Preferred examples include 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,3-diethylimidazolium, and 1-butyl-3-methylimidazolium, although the present invention is not limited to these.

[0035] In the formula (1-1), specific examples of the imidazolium having a hydrocarbon group containing a hetero atom include 1,3-bis(2-methoxyethyl)imidazolium, 1,3-bis(2-ethoxyethyl)imidazolium, 1,3-bis(2-propoxyethyl)imidazolium, 1,3-bis(2-isopropoxyethyl)imidazolium, 1,3-bis(2-phenoxyethyl)imidazolium, 1,3-bis(2-benzyloxyethyl)imidazolium, 1,3-bis[2-(p-methoxybenzyloxy)ethyl]imidazolium, 1,3-bis[2- (2-methoxyethoxymethoxy)ethyl]imidazolium, 1,3-bis[2-(2-benzyloxyethoxy)ethyl]imidazolium, 1,3-bis(3-methoxypropyl)imidazolium, 1,3-bis(3-ethoxypropyl)imidazolium, 1,3-bis(3-propoxypropyl)imidazolium, 1,3-bis(3-isopropoxypropyl)imidazolium, 1,3-bis(3-allyloxypropyl)imidazolium, 1,3-bis(3-butoxypropyl)imidazolium, 1,3-bis[3-(1-methylpropoxy)propyl]imidazolium, pyryl]imidazolium, 1,3-bis[3-(2-methylpropoxy)propyl]imidazolium, 1,3-bis[3-(1,1-dimethylethoxy)propyl]imidazolium, 1,3-bis[(oxolan-2-yl)methyl]imidazolium, 1,3-bis(3-pentyloxypropyl)imidazolium, 1,3-bis(3-neopentyloxypropyl)imidazolium, 1,3-bis(3-hexyloxypropyl)imidazolium, 1,3-bis(3-cyclohexyloxypropyl)imidazolium, 1,3-bis(3-heptyloxypropyl)imidazolium, propyl)imidazolium, 1,3-bis(3-octyloxypropyl)imidazolium, 1,3-bis(3-nonyloxypropyl)imidazolium, 1,3-bis{3-[(2-ethylhexyl)oxy]propyl}imidazolium, 1,3-bis[3-(2,4,6-trimethylphenoxy)propyl]imidazolium, 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium, 1,3-bis[2-(dimethylamino)ethyl]imidazolium, 1,3-bis[3-(dimethylamino)propyl]imidazolium, 1,3-Bis(2-methylthioethyl)imidazolium, 1,3-bis{2-[(furan-2-yl)methylthio]ethyl]imidazolium, 1,3-bis[2-(furan-2-yl)methyl]imidazolium, 1,3-bis[1-(methoxymethyl)propyl]imidazolium, 1,3-bis(4-methoxybutyl)imidazolium, 1,3-bis(4-ethoxybutyl)imidazolium, 1,3-bis(4-propoxybutyl)imidazolium, 1,3-bis(4-isopropoxybutyl)imidazolium, 1,3-bis(4-allyloxybutyl)imidazolium )imidazolium, 1,3-bis(4-butoxybutyl)imidazolium, 1,3-bis[4-(1-methylpropoxy)butyl]imidazolium, 1,3-bis[4-(2-methylpropoxy)butyl]imidazolium, 1,3-bis[4-(1,1-dimethylethoxy)butyl]imidazolium, 1,3-bis(4-pentyloxybutyl)imidazolium, 1,3-bis(4-neopentyloxybutyl)imidazolium, 1,3-bis(4-hexyloxybutyl)imidazolium, 1,3-bis(4-cyclohexyloxybutyl)imidazolium imidazolium, 1,3-bis(4-heptyloxybutyl)imidazolium, 1,3-bis(4-octyloxybutyl)imidazolium, 1,3-bis{4-[(2-ethylhexyl)oxy]butyl}imidazolium, 1,3-bis(5-methoxypentyl)imidazolium, 1,3-bis(5-ethoxypentyl)imidazolium, 1,3-bis(5-propoxypentyl)imidazolium, 1,3-bis(5-isopropoxypentyl)imidazolium, 1,3-bis(5-allyloxypentyl)imidazolium, 1,3-bis (5-butoxypentyl)imidazolium, 1,3-bis[5-(1-methylpropoxy)pentyl]imidazolium, 1,3-bis[5-(2-methylpropoxy)pentyl]imidazolium, 1,3-bis[5-(1,1-dimethylethoxy)pentyl]imidazolium, 1,3-bis(5-pentyloxypentyl)imidazolium, 1,3-bis(5-neopentyloxypentyl)imidazolium, 1,3-bis(5-hexyloxypentyl)imidazolium, 1,3-bis(5-cyclohexyloxypentyl)imidazolium, 1,3-Bis(5-heptyloxypentyl)imidazolium, 1,3-bis(6-methoxyhexyl)imidazolium, 1,3-bis(6-ethoxyhexyl)imidazolium, 1,3-bis(6-propoxyhexyl)imidazolium, 1,3-bis(6-isopropoxyhexyl)imidazolium, 1,3-bis(6-allyloxyhexyl)imidazolium, 1,3-bis(6-butoxyhexyl)imidazolium, 1,3-bis[6-(1-methylpropoxy)hexyl]imidazolium, 1,3-bis[6-(2-methylpropoxy)hexyl ]imidazolium, 1,3-bis[6-(1,1-dimethylethoxy)hexyl]imidazolium, 1,3-bis(6-pentyloxyhexyl)imidazolium, 1,3-bis(6-neopentyloxyhexyl)imidazolium, 1,3-bis(6-hexyloxyhexyl)imidazolium, 1,3-bis(6-cyclohexyloxyhexyl)imidazolium, 1,3-bis[(2-methoxycyclohexan-1-yl)methyl]imidazolium, 1,3-bis[(2-ethoxycyclohexan-1-yl)methyl]imidazolium, 1,3- Bis[(2-propoxycyclohexan-1-yl)methyl]imidazolium, 1,3-bis[(2-isopropoxycyclohexan-1-yl)methyl]imidazolium, 1,3-bis[(2-butoxycyclohexan-1-yl)methyl]imidazolium, 1,3-bis{[2-(1-methylpropoxy)cyclohexan-1-yl]methyl}imidazolium, 1,3-bis{[2-(2-methylpropoxy)cyclohexan-1-yl]methyl}imidazolium, 1,3-bis{[2-(1,1-dimethylethoxy)cyclohexan-1-yl] methyl}imidazolium, 1,3-bis[(2-pentyloxycyclohexan-1-yl)methyl]imidazolium, 1,3-bis[(2-neopentyloxycyclohexan-1-yl)methyl]imidazolium, 1,3-bis(3-methylthiopropyl)imidazolium, 1,3-bis[2-(methylsulfonyl)ethyl]imidazolium, 1,3-bis[(thiophen-2-yl)methyl]imidazolium, 1,3-bis(p-methoxyphenyl)imidazolium, 1,3-bis(p-ethoxyphenyl)imidazolium, 1,3-bis(3,4-methylenedioxyphenyl)imidazolium, 1,3-bis(3,4-methylenedioxybenzyl)imidazolium, 1,3-bis{(7-oxabicyclo[2,2,1]heptan-2-yl)methyl}imidazolium, 1-methoxypropyl-3-methylthiopropylimidazolium, 1,3-bis(3-methoxypropyl)-2-methylimidazolium, 1,3-bis(2-methoxyethyl)-2-methylimidazolium, and the like are included, and 1,3-bis(3-methoxypropyl)-2-methylimidazolium is preferable. 1,3-bis(3-ethoxypropyl)imidazolium, 1,3-bis(3-propoxypropyl)imidazolium, 1,3-bis(3-isopropoxypropyl)imidazolium, 1,3-bis(3-allyloxypropyl)imidazolium, 1,3-bis(3-butoxypropyl)imidazolium, 1,3-bis[3-(1-methylpropoxy)propyl]imidazolium, 1,3-bis[3-(2-methylpropoxy)propyl]imidazolium , 1,3-bis[3-(1,1-dimethylethoxy)propyl]imidazolium, 1,3-bis[(oxolan-2-yl)methyl]imidazolium, 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium, 1,3-bis(3-methylthiopropyl)imidazolium, 1-methoxypropyl-3-methylthiopropylimidazolium, 1,3-bis(3-methoxypropyl)-2-methylimidazolium, 1,3-bis(2-methoxyethyl)-2-methylimidazolium Imidazolium, more preferably 1,3-bis(3-methoxypropyl)imidazolium, 1,3-bis(3-ethoxypropyl)imidazolium, 1-methoxypropyl-3-methylthiopropylimidazolium, 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium, 1,3-bis(2-methoxyethyl)-2-methylimidazolium, and 1,3-bis(3-methoxypropyl)-2-methylimidazolium, but the present invention is not limited thereto.

[0036] In the formula (1), the carboxylate anion represented by the following formula (1-2) will be described. Formula (1-2): [ka] (In formula (1-2), R 6 represents a hydrocarbon group which may contain a heteroatom and may contain a double bond and / or a ring structure and / or a branched structure.

[0037] In formula (1-2), R 6 represents a hydrocarbon group which may contain a heteroatom. The "hydrocarbon group which may contain a heteroatom" may be linear, branched and / or containing a ring structure and / or a double bond. 6 In the above formula, the hydrocarbon group does not necessarily contain a heteroatom.

[0038] In formula (1-2), R 6 When R is a hydrocarbon group containing no heteroatom, it preferably has 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and further preferably 1 to 3 carbon atoms. 6 When is a hydrocarbon group containing a hetero atom, it preferably has 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 2 to 4 carbon atoms.

[0039] In formula (1-2), R 6 When it contains a heteroatom, the number of heteroatoms is preferably 1 to 5, and more preferably 1 to 2. The number of carbon atoms in the hydrocarbon group is 2 or more, preferably 2 to 12, more preferably 2 to 8, and further preferably 2 to 4.

[0040] In formula (1-2), R 6 When is a hydrocarbon group containing a heteroatom, examples of the "heteroatom" include a nitrogen atom, an oxygen atom, a sulfur atom, etc. The number of heteroatoms is preferably 1 to 5, and more preferably 1 to 2.

[0041] In formula (1-2), R 6In the above, a "hydrocarbon group containing a heteroatom" refers to a hydrocarbon group not containing a heteroatom, in which (i) the bond between two adjacent carbon atoms and / or (ii) the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of another -CH2- (methylene group) are bonded together such that -O-, -N<, -NH-, -S-, -C(=O)-O-, -C(=O)-, =N-, -C(=O)-N<, -C(=O)-NH-, -OC(=O)-O-, -OC(=O)-N<, -OC(=O)-NH-, -C(=O)- N[-C(=O)-]-, -C(=O)-NH-C(=O)-, >NC(=O)-N<, >NC(=O)-NH-, -HN-C(=O)-NH-, -S(=O)-, -S(=O)2-, -S(=O)2-O-, -OS(=O)2-O-, >NC(=S)-N<, >NC(=S)-NH-, -HN-C(=S)-NH-, -C(=N-)-, -C(=NH)-, and the like are substituted with structures such as these. The number and combination of substitutions with these structures are not particularly limited. 6 The number of heteroatoms therein is preferably 1 to 5, and more preferably 1 or 2.

[0042] Preferably, (i) the bond between two adjacent carbon atoms and / or (ii) the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of the other -CH2- (methylene group) are replaced by an -O- or -S- structure, more preferably by an -O- structure.

[0043] In formula (1-2), R 6 In the above, the structure in which (i) the bond between two adjacent carbon atoms and / or (ii) the hydrogen atom of one -CH2- (methylene group) of the hydrocarbon group is replaced with a -O- or -S- structure may be an ether structure, a thioether structure, or an epoxy structure or thioepoxy structure such as an epoxy group, a thioepoxy group, a glycidyl ether group, or an epoxycyclohexyl group. In this case, R 1 may be an epoxy group, a thioepoxy group, or the like.

[0044] In formula (1-2), R 6 When the compound contains two or more -O- and / or -S- structures, the number of carbon atoms between the -O- and / or -S- structures is desirably two or more.

[0045] In formula (1-2), R 6 In the above, examples of the "hydrocarbon group which may contain a heteroatom" include a linear or branched alkyl group which may contain a heteroatom, a linear or branched alkenyl group which may contain a heteroatom, a linear or branched alkynyl group which may contain a heteroatom, a cycloalkyl group which may contain a heteroatom and may be branched, a cycloalkenyl group which may contain a heteroatom and may be branched, an aryl group which may contain a heteroatom and may be branched, an aralkyl group which may contain a heteroatom and may be branched, etc. Preferred are a linear or branched alkyl group which may contain a heteroatom, a linear or branched alkenyl group which may contain a heteroatom, and a cycloalkyl group which may contain a heteroatom and may be branched.

[0046] The "linear or branched alkyl group which may contain a heteroatom" is preferably a linear or branched alkyl group having 1 to 12 carbon atoms which may contain 1 to 5 heteroatoms. In another embodiment, it is preferably a linear or branched alkyl group having 1 to 12 carbon atoms which may contain 1 to 2 heteroatoms, more preferably a linear or branched alkyl group having 1 to 8 carbon atoms which may contain 1 to 2 heteroatoms, and even more preferably a linear or branched alkyl group having 1 to 4 carbon atoms which may contain 1 to 2 heteroatoms. In yet another embodiment, it is preferably a linear or branched alkyl group having 1 to 12 carbon atoms, more preferably a linear or branched alkyl group having 1 to 8 carbon atoms, and even more preferably a linear or branched alkyl group having 1 to 3 carbon atoms.

[0047] The "linear or branched alkenyl group which may contain a heteroatom" is preferably a linear or branched alkenyl group having 2 to 12 carbon atoms which may contain 1 to 5 heteroatoms. In another embodiment, it is preferably a linear or branched alkenyl group having 2 to 12 carbon atoms which may contain 1 to 2 heteroatoms, more preferably a linear or branched alkenyl group having 2 to 8 carbon atoms which may contain 1 to 2 heteroatoms, and even more preferably a linear or branched alkenyl group having 2 to 4 carbon atoms which may contain 1 to 2 heteroatoms. In yet another embodiment, it is preferably a linear or branched alkenyl group having 2 to 12 carbon atoms, more preferably a linear or branched alkenyl group having 2 to 8 carbon atoms, and even more preferably a linear or branched alkenyl group having 2 to 3 carbon atoms.

[0048] The "cycloalkyl group which may contain a heteroatom or may have a branch" is preferably a cycloalkyl group having 3 to 12 carbon atoms which may contain 1 to 5 heteroatoms and which may have a branch. In another embodiment, it is preferably a cycloalkyl group having 3 to 12 carbon atoms which may contain 1 to 2 heteroatoms and which may have a branch, more preferably a cycloalkyl group having 3 to 8 carbon atoms which may contain 1 to 2 heteroatoms and which may have a branch, and even more preferably a cycloalkyl group having 3 to 4 carbon atoms which may contain 1 to 2 heteroatoms. In yet another embodiment, it is preferably a cycloalkyl group having 3 to 12 carbon atoms which may have a branch, more preferably a cycloalkyl group having 3 to 8 carbon atoms which may have a branch, and even more preferably a cycloalkyl group having 3 carbon atoms.

[0049] In formula (1-2), R 6In the above, specific examples of the "hydrocarbon group not containing a hetero atom" include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, a vinyl group, an ethynyl group, a propenyl group, an isopropenyl group, an allyl group, a propargyl group, a butenyl group, a crotyl group, a butadienyl group, a cyclopropyl group, a cyclobutyl ... Examples of the aryl group include a methyl group, an ethyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, a phenyl group, a benzyl group, a tolyl group, a styryl group, and a 2,4,6-trimethylphenyl group. Of these, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group are preferred, and a methyl group, an ethyl group, a propyl group, an isopropyl group, and a tert-butyl group are more preferred.

[0050] In formula (1-2), R 6 In the above, the "hydrocarbon group containing a hetero atom" is preferably a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, a propoxy group, or a 2-methoxyethoxy group, and more preferably a methoxymethyl group, a methoxyethyl group, or a 2-methoxyethoxy group, although the present invention is not limited thereto.

[0051] In formula (1-2), R 6 is preferably a methyl group, an ethyl group, a methoxymethyl group, or a methoxyethyl group.

[0052] Specific examples of the carboxylate anion represented by formula (1-2) include acetate ion, propionate ion, acrylate ion, propargyl ion, butyrate ion, isobutyrate ion, methacrylate ion, crotonate ion, tetrolate ion, cyclopropanecarboxylate ion, valerate ion, isovalerate ion, pivalate ion, angelic acid ion, tiglate ion, cyclobutanecarboxylate ion, caproate ion, cyclopentanecarboxylate ion, enanthate ion, sorbic acid ion, cyclohexanecarboxylate ion, benzoate ion, caprylate ion, 2-ethylhexylcarboxylate ion, toluate ion, 2-norbornanecarboxylate ion, pelargonate ion, cinnamate ion, capric acid ion, adamantanecarboxylate ion, geranate ion, undecylate ion, laurate ion, and naphthalenecarboxylate ion. Of these, acetate ion, propionate ion, acrylate ion, propargyl ion, butyrate ion, isovalerate ion, and naphthalenecarboxylate ion are preferred. sobutyrate ion, methacrylate ion, crotonate ion, tetrolate ion, valerate ion, isovalerate ion, pivalate ion, methoxyacetate ion, ethoxyacetate ion, propoxyacetate ion, (2-methoxyethoxy)acetate ion, (2-ethoxyethoxy)acetate ion, (2-propoxyethoxy)acetate ion, 3-(2-methoxyethoxy)propanoate ion, 3-(2-ethoxyethoxy)propanoate ion, 3-(2-propoxyethoxy)propanoate ion, 3-(3- methoxypropoxy)propanoic acid ion, 3-(3-ethoxypropoxy)propanoic acid ion, 3-(3-propoxypropoxy)propanoic acid ion, 3-[2-(2-methoxyethoxy)ethoxy]propanoic acid ion, 3-[2-(2-ethoxyethoxy)ethoxy]propanoic acid ion, 4,7,10,13-tetraoxatetradecanoic acid ion, 4,7,10,13-tetraoxapentadecanoic acid ion, 4,7,10,13,16-pentaoxaheptadecanoic acid ion, 4,7,10,Examples of the cations include 13,16-pentaoxaoctadecanoic acid ion, (methylthio)acetate ion, (ethylthio)acetate ion, 3-(methylthio)propanoic acid ion, 3-[(2-methoxyethyl)thio]propanoic acid ion, and 3-[(2-ethoxyethyl)thio]propanoic acid ion. Particularly preferred are acetate ion, methoxyacetate ion, acrylate ion, and methacrylate ion, but the present invention is not limited to these.

[0053] The imidazolium carboxylate represented by formula (1) is preferably an onium salt composed of a combination of one cation selected from the group consisting of 1,3-bis(2-methoxyethyl)imidazolium, 1,3-bis(3-methoxypropyl)imidazolium, 1,3-bis(3-ethoxypropyl)imidazolium, 1,3-bis(3-methylthiopropyl)imidazolium, 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium, 1-methoxypropyl-3-methylthiopropylimidazolium, 1,3-bis(2-methoxyethyl)-2-methylimidazolium, and 1,3-bis(3-methoxypropyl)-2-methylimidazolium, and one anion selected from the group consisting of acetate ion, methoxyacetate ion, acrylate ion, and methacrylate ion.

[0054] More specifically, the onium salt represented by formula (1) includes 1,3-bis(2-methoxyethyl)imidazolium acetate, 1,3-bis(3-methoxypropyl)imidazolium acetate, 1,3-bis(3-methoxypropyl)imidazolium acrylate, 1,3-bis(3-methoxypropyl)imidazolium methacrylate, 1,3-bis(3-ethoxypropyl)imidazolium acetate, 1-methoxypropyl-3-methylthiopropylimidazolium acetate, 1,3-bis(3-methylthiopropyl)imidazolium acetate, 1,3-bis(2-methoxyethyl)-2-methylimidazolium acetate, 1,3-bis(2-methoxyethyl)-2-methylimidazolium acrylate, 1,3-bis(2-methoxyethyl)-2-methylimidazolium methacrylate, 1, Examples of the imidazolium methacrylate include 3-bis(3-methoxypropyl)-2-methylimidazolium acetate, 1,3-bis(3-methoxypropyl)-2-methylimidazolium acrylate, 1,3-bis(3-methoxypropyl)-2-methylimidazolium methacrylate, 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium acetate, 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium acrylate, and 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium methacrylate. Preferred are 1,3-bis(3-methoxypropyl)imidazolium acetate, 1,3-bis(3-methoxypropyl)imidazolium acrylate, and 1,3-bis(3-methoxypropyl)imidazolium methacrylate, but the present invention is not limited thereto.

[0055] The present invention is a method for producing an onium salt represented by formula (1), which includes the following steps (1), (2), and (3). Process (1): A step of obtaining a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3) below, which is obtained by the reaction represented by formula (2) below. Formula (2): [ka] Formula (3): [ka] (In formula (3), R 6 represents a hydrocarbon group which may contain a heteroatom and which may contain a double bond and / or a ring structure and / or a branched structure. Process (2): A step of adding an amine to a mixture containing the onium salt represented by formula (1) obtained in step (1) and a carboxylic acid represented by formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid represented by formula (3). Process (3): A step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2) to obtain the onium salt represented by formula (1).

[0056] Step (1) is a step of obtaining a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3) through the reaction represented by formula (2) below. Formula (2): [ka] (In formula (2), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are R in formula (1), 1 , R 2 , R 3 , R 4 , R 5 and R 6 is the same as

[0057] The reaction of formula (2) is explained below. 1 -NH2 and / or R 2 Amine compounds represented by -NH2, R 3 Aldehyde compounds represented by -CHO, R 4 -C(=O)-C(=O)-R 5 and dicarbonyl compounds represented by R 6A carboxylic acid represented by -COOH (formula (3)) is reacted.

[0058] R 1 -NH2 and / or R 2Specific examples of the amine compound represented by -NH2 include 2-methoxyethylamine, 2-ethoxyethylamine, 2-propoxyethylamine, 2-isopropoxyethylamine, 2-allyloxyethylamine, 2-butoxyethylamine, 2-(1-methylpropoxy)ethylamine, 2-(2-methylpropoxy)ethylamine, 2-(1,1-dimethylethoxy)ethylamine, 2-pentyloxyethylamine, 2-neopentyloxyethylamine, 2-hexyloxyethylamine, 2-phenoxyethylamine, 2-heptyloxyethylamine, 2-octyloxyethylamine, 2-nonyloxyethylamine, 2-decyloxyethylamine, 2-cyclopentyloxyethylamine, 2-cyclohexyloxyethylamine, 2-(2-ethylhexyl-1-yl)oxyethylamine, 2-(2,4,6-trimethylphenoxy)ethylamine, 2-(benzyloxy)ethylamine, and 2-(1,1-dimethylethoxy)ethylamine. , 2-(p-methoxybenzyloxy)ethylamine, 2-(2-methoxyethoxymethoxy)ethylamine, 2-(2-benzyloxyethoxy)ethylamine, 2-(dimethylamino)ethylamine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-propoxypropylamine, 3-allyloxypropylamine, 3-isopropoxypropylamine, 3-(1-methylpropoxy)propylamine, 3-(2-methylpropoxy)propylamine, 3-(1,1-dimethylethoxy)propylamine, 3-butoxypropylamine, 3-pentyloxypropylamine, 3-neopentyloxypropylamine, 3-hexyloxypropylamine, 3-cyclohexyloxypropylamine, 3-heptyloxypropylamine, 3-octyloxypropylamine, 3-nonyloxypropylamine, 3-(2-ethylhexyl)oxypropylamine, 3-(2,4,6-trimethylphenoxy)propylamine, 3-(2-methoxyethoxy)propylamine, 3-(dimethylamino)propylamine, 4-methoxybutylamine, 4-ethoxybutylamine, 4-propoxybutylamine, 4-isopropoxybutylamine, 4-allyloxybutylamine, 4-butoxybutylamine, 4-(1-methylpropoxy)butylamine, 4-(2-methylpropoxy)butylamine, 4-(1,1-dimethylethoxy)butylamine, 4-pentyloxybutylamine, 4-neopentyloxybutylamine, 4-hexyloxybutylamine, 4-cyclohexyloxybutylamine, 4-heptyloxybutylamine, 4-octyloxybutylamine, 4-(2-ethylhexyl)oxybutylamine, 5-methoxypentylamine, 5-ethoxypentylamine amine, 5-propoxypentylamine, 5-isopropoxypentylamine, 5-allyloxypentylamine, 5-butoxypentylamine, 5-(1-methylpropoxy)pentylamine, 5-(2-methylpropoxy)pentylamine, 5-(1,1-dimethylethoxy)pentylamine, 5-pentyloxypentylamine, 5-neopentyloxypentylamine, 5-hexyloxypentylamine, 5-cyclohexyloxypentylamine, 5-heptyloxypentylamine, 6-methoxyhexylamine, 6-ethoxyhexylamine, 6-propoxyhexylamine, 6-isopropoxyhexylamine, 6-allyloxyhexylamine, 6-butoxyhexylamine, 6-(1-methylpropoxy)hexylamine, 6-(2-methylpropoxy)hexylamine, 6-(1,1-Dimethylethoxy)hexylamine, 6-Pentyloxyhexylamine, 6-Neopentyloxyhexylamine, 6-Hexyloxyhexylamine, 6-Cyclohexyloxyhexylamine, 2-Methoxycyclohexyl-1-ylmethylamine, (2-Ethoxycyclohexan-1-yl)methylamine, (2-Propoxycyclohexan-1-yl)methylamine, (2-Isopropoxycyclohexan-1-yl)methylamine, (2-Butoxycyclohexyl -1-yl)methylamine, [2-(1-methylpropoxy)cyclohexan-1-yl]methylamine, [2-(2-methylpropoxy)cyclohexan-1-yl]methylamine, [2-(1,1-dimethylethoxy)cyclohexan-1-yl]methylamine, (2-pentyloxycyclohexan-1-yl)methylamine, (2-neopentyloxycyclohexan-1-yl)methylamine, 2-methylthioethylamine, 3-methylthiopropylamine, 1-(methoxy) Examples of suitable amines include (dimethyl)propylamine, (oxolan-2-yl)methylamine, (furan-2-yl)methylamine, 2-[(furan-2-yl)methylthio]ethylamine, 2-(methylsulfonyl)ethylamine, (thiophen-2-yl)methylamine, p-methoxyphenylamine, p-ethoxyphenylamine, 3,4-methylenedioxyaniline, 3,4-methylenedioxybenzylamine, and (7-oxabicyclo[2,2,1]heptan-2-yl)methylamine. Preferred are 2-methoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3-(2-methoxyethoxy)propylamine, 3-methylthiopropylamine, and 3-(dimethylamino)propylamine. More preferred are 2-methoxyethylamine, 3-methoxypropylamine, and 3-(2-methoxyethoxy)propylamine, but the present invention is not limited thereto. 1 -NH2 or R 2 The amine compounds represented by -NH2 may be the same or different.

[0059] R 3Specific examples of the aldehyde compound represented by -CHO include formaldehyde, acetaldehyde, propionaldehyde, butanal, etc., and are preferably formaldehyde and acetaldehyde, but the present invention is not limited thereto. As the formaldehyde, a cyclic oligomer or polymer capable of generating formaldehyde in the reaction system, such as paraformaldehyde, trioxane, or tetraoxane, may be used.

[0060] R 3 The aldehyde compound represented by --CHO may be used in the form of an aqueous solution of the aldehyde compound or a solution in an alcohol such as methanol, butanol, or 2-ethylhexanol.

[0061] R 4 -C(=O)-C(=O)-R 5 Specific examples of the dicarbonyl compound represented by the formula (I) include glyoxal, methylglyoxal, diacetyl, 3,4-hexanedione, 2,3-pentanedione, 2,3-heptanedione, 5-methyl-2,3-hexanedione, 3-methyl-2,3-cyclopentanedione, 1,2-cyclohexanedione, 1-phenyl-1,2-propanedione, and dibenzoyl, more preferably glyoxal, methylglyoxal, and diacetyl, and more preferably glyoxal.

[0062] R 4 -C(=O)-C(=O)-R 5 The dicarbonyl compound represented by the formula (I) may be used in the form of an aqueous solution of the dicarbonyl compound or a solution in an alcohol such as methanol, butanol, or 2-ethylhexanol.

[0063] R 6Specific examples of the carboxylic acid represented by -COOH (formula (3)) include acetic acid, propionic acid, acrylic acid, propargylic acid, butyric acid, isobutyric acid, methacrylic acid, crotonic acid, tetrolic acid, cyclopropanecarboxylic acid, valeric acid, isovaleric acid, pivalic acid, angelic acid, tiglic acid, cyclobutanecarboxylic acid, caproic acid, cyclopentanecarboxylic acid, enanthic acid, sorbic acid, cyclohexanecarboxylic acid, benzoic acid, caprylic acid, 2-ethylhexyl carboxylic acid, toluic acid, 2-methylbutanediol, and 2-methylbutanediol. -norbornane carboxylic acid, pelargonic acid, cinnamic acid, capric acid, adamantane carboxylic acid, geranic acid, undecylic acid, lauric acid, naphthalene carboxylic acid, etc. are included, and preferable are acetic acid, propionic acid, acrylic acid, propargylic acid, butyric acid, isobutyric acid, methacrylic acid, crotonic acid, tetrolic acid, valeric acid, isovaleric acid, pivalic acid, methoxyacetic acid, ethoxyacetic acid, propoxyacetic acid, (2-methoxyethoxy)acetic acid, (2-ethoxyethoxy)acetic acid, (2-propoxyethoxy)acetic acid, Acetic acid, 3-(2-methoxyethoxy)propanoic acid, 3-(2-ethoxyethoxy)propanoic acid, 3-(2-propoxyethoxy)propanoic acid, 3-(3-methoxypropoxy)propanoic acid, 3-(3-ethoxypropoxy)propanoic acid, 3-(3-propoxypropoxy)propanoic acid, 3-[2-(2-methoxyethoxy)ethoxy]propanoic acid, 3-[2-(2-ethoxyethoxy)ethoxy]propanoic acid, 4,7,10,13-tetraoxatetradecanoic acid, 4,7,1 Examples of the acetic acid include 0,13-tetraoxapentadecanoic acid, 4,7,10,13,16-pentaoxaheptadecanoic acid, 4,7,10,13,16-pentaoxaoctadecanoic acid, (methylthio)acetic acid, (ethylthio)acetic acid, 3-(methylthio)propanoic acid, 3-[(2-methoxyethyl)thio]propanoic acid, and 3-[(2-ethoxyethyl)thio]propanoic acid. Particularly preferred are acetic acid, methoxyacetic acid, acrylic acid, and methacrylic acid, but the present invention is not limited to these.

[0064] R 1 -NH2 and R 2 The amount of the amine compound represented by -NH2 to be used is 1 mole of the dicarbonyl compound. 1 -NH2 and R 2The total amount of -NH2 is preferably 0.1 to 10 mol, more preferably 0.5 to 3 mol. 1 and R 2 When R 1 -NH2 and R 2 The ratio (molar ratio) of R 1 -NH2:R 2 -NH2=0:100~100:0. 1 -NH2:R 2 -NH2=0:100 or 100:0, R 1 =R 2 It becomes. R 1 -NH2:R 2 When -NH2 is not 0:100 or 100:0, the onium salt represented by formula (1) obtained by the reaction of formula (2) is a mixture of compounds represented by the following formulas. Both compounds represented by the following formulas (1') and (1'') are included in the onium salt represented by formula (1), and the mixture may be used as an onium salt mixture described below. In addition, the mixture may be optionally purified to obtain a desired single compound and then used as the onium salt represented by formula (1).

[0065] [ka]

[0066] R 3 The aldehyde compound represented by -CHO may be used as an aqueous solution of the aldehyde compound or an alcohol solution such as methanol, butanol, 2-ethylhexanol, etc. The amount of the aldehyde compound used is preferably 0.1 to 10 mol, more preferably 0.5 to 5 mol, per 1 mol of the dicarbonyl compound.

[0067] R 6The amount of the carboxylic acid represented by -COOH (formula (3)) used is preferably an excess amount per mole of the imidazole cation purified by formula (2). The amount of the carboxylic acid per mole of the dicarbonyl compound is preferably 1.1 to 10 moles, more preferably 1.2 to 5 moles, and particularly preferably 1.5 to 3 moles. Thus, a mixture containing the onium salt of formula (1) and the carboxylic acid of formula (3) is obtained by the reaction of formula (2).

[0068] In the reaction of formula (2), a solvent may or may not be used. When a solvent is used, the solvent to be used is not particularly limited as long as it does not affect the reaction. Specific examples of the solvent include aromatic hydrocarbon solvents such as toluene, benzene, and xylene, hydrocarbon solvents such as methylcyclohexane, cyclohexane, hexane, heptane, and octane, halogenated hydrocarbon solvents such as dichloromethane and chloroform, ether solvents such as diethyl ether, tetrahydrofuran, and 1,4-dioxane, alcohol solvents such as methanol, ethanol, and 2-propanol, N,N-dimethylformamide, acetonitrile, and water, and preferably alcohol solvents and water.

[0069] Also, the onium salt represented by formula (1) previously prepared can be used as a reaction solvent for the reaction of formula (2). Two or more kinds of solvents can be mixed and used as desired. The amount of the solvent used is preferably 50 parts by mass or less, more preferably 0.1 to 10 parts by mass, per part by mass of the dicarbonyl compound.

[0070] The reaction of formula (2) may be optionally carried out under an inert gas atmosphere that does not affect the reaction, such as nitrogen, argon, or helium.

[0071] When the reaction of formula (2) is carried out, the reaction pressure is usually atmospheric pressure, but depending on the raw materials and / or solvent used, the reaction may be carried out by pressurizing the reaction system to a pressure of atmospheric pressure to 1 MPa.

[0072] When carrying out the reaction of formula (2), the optimum reaction temperature differs depending on the raw materials, solvent, etc. used, but is preferably -10°C or higher, and more preferably 0°C to 100°C.

[0073] After completion of the reaction of the formula (2), the onium salt represented by the formula (1) may be purified by a known purification method or may not be purified. The purification method includes, but is not limited to, concentration, separation, recrystallization, dialysis, adsorption, filtration, etc.

[0074] Step (2) in the method for producing an onium salt represented by formula (1) of the present invention is a step of adding an amine to a mixture containing the onium salt represented by formula (1) obtained in step (1) and a carboxylic acid of formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid of formula (3).

[0075] The amine added in step (2) is preferably an amine represented by the following formula (4). Formula (4): [ka] (In formula (4), R 7 , R 8 and R 9 may be the same or different and are a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and the hydrocarbon group may contain a double bond and may contain a branched structure and / or a ring structure. 7 , R 8 and R 9 The total number of carbon atoms in each of these is 8 or more.)

[0076] In formula (4), R 7 , R 8 and R 9 In the above formula, the hydrocarbon group has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, and further preferably 1 to 8 carbon atoms. R 7 , R 8 and R 9 The total number of carbon atoms contained in each of these is 8 or more, and preferably 12 or more and 24 or less.

[0077] R 7 , R 8 and R 9 In the above, specific examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a decyl group, a dodecyl group, an octadecyl group, etc. In addition, the isopropyl group, the sec-butyl group, the isobutyl group, the tert-butyl group, the neopentyl group, and the 2-ethylhexyl group each include a branched structure.

[0078] R 7 , R 8 and R 9 Specific examples of the hydrocarbon group containing a double bond in the above formula include a vinyl group, an ethynyl group, a propenyl group, an isopropenyl group, an allyl group, a propargyl group, a butenyl group, a crotyl group, a butadienyl group, and an oleyl group.

[0079] R 7 , R 8 and R 9 In the above, specific examples of the hydrocarbon group containing a ring structure include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, a phenyl group, a benzyl group, a tolyl group, a styryl group, and a 2,4,6-trimethylphenyl group. In addition, the cyclopropyl group, the cyclobutyl group, the cyclopentyl group, the cyclohexyl group, the norbornyl group, and the adamantyl group each contain a branched structure.

[0080] R 7 , R 8 and R 9 is preferably a hydrogen atom, a methyl group, an oleyl group, a 2-ethylhexyl group, a cyclohexyl group, an octadecyl group, or an octyl group.

[0081] Specific examples of the amine represented by formula (4) include tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, oleylamine, di-2-ethylhexylamine, dicyclohexylamine, methyloctadecylamine, dimethyloctadecylamine, and trioctylamine.

[0082] The amount of amine added to the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) is 1 equivalent or more of amine relative to 1 equivalent of carboxylic acid, preferably 1 to 1.5 equivalents, more preferably 1 to 1.2 equivalents, and particularly preferably 1 to 1.1 equivalents. An amine-carboxylate consisting of the added amine and the carboxylic acid represented by formula (3) is generated, and a mixture of the onium salt represented by formula (1), the amine-carboxylate, and the remaining amine is obtained.

[0083] The amine to be added may be added as an amine solution diluted with a solvent, such as chloroform, dichloromethane, 2-ethylhexanol, cyclohexanol, 1-octanol, ethyl acetate, etc., and preferably chloroform, 2-ethylhexanol, cyclohexanol, or 1-octanol. The concentration of the amine solution is preferably 0.01 g / L to 10.0 g / L, and more preferably 0.1 g / L to 5.00 g / L.

[0084] The reaction conditions for generating an amine-carboxylate by adding an amine to a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3) are as follows: the temperature is 0°C to 100°C, and preferably 25°C to 80°C; and the reaction time is preferably 0.5 hours to 3 hours, and more preferably 1 hour to 2 hours, after completion of the addition of the amine, during which the mixture is stirred. In a preferred embodiment of the present invention, the mixture in step 1 further contains water and a solvent. The solvent may be a solvent for diluting the amine to be added, or may be added to the mixture in step 1 alone without being used to dilute the amine. The solvent contained in the mixture is preferably a solvent that undergoes phase separation with water. Examples of the solvent that undergoes phase separation with water include hexane, heptane, toluene, chloroform, dichloromethane, 2-ethylhexanol, cyclohexanol, 1-octanol, and ethyl acetate, and preferably include chloroform, 2-ethylhexanol, cyclohexanol, and 1-octanol. When the mixture in step 1 contains water and the solvent, the added amine forms an amine-carboxylate and is extracted mainly into the solvent layer. On the other hand, since the onium salt represented by formula (1) is present in the water layer, the amine-carboxylate is separated by separating the solvent layer, and the amount of the carboxylic acid represented by formula (3) is reduced or almost completely removed, resulting in a water layer containing the onium salt represented by formula (1). The carboxylic acid represented by formula (3) coexisting with the onium salt represented by formula (1) is difficult to remove by evaporation, but the water in the water layer containing the onium salt represented by formula (1) can be easily removed by evaporation, and the onium salt represented by formula (1) can be obtained. In the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) before carrying out the production method or purification method of the present invention, the solubility of cellulose is greatly reduced due to the presence of the carboxylic acid represented by formula (3), but the solubility of cellulose can be greatly improved by carrying out the production method or purification method of the present invention. For example, in a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3), the solubility of cellulose can be greatly improved by removing 50% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 100% of the carboxylic acid represented by formula (3).

[0085] Step (3) is a step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2). Examples of the separation method include separation and crystallization.

[0086] By the separation in step (3), a separated liquid containing the onium salt represented by formula (1) is obtained. When the separated liquid contains residual amine, the residual amine can be distilled off by heating and / or reducing the pressure of the separated liquid. In addition, when the amine is added as an amine solution diluted with a solvent, and the separated liquid containing the onium salt represented by formula (1) separated in step (3) contains the solvent, the solvent can be distilled off by heating and / or reducing the pressure of the separated liquid obtained.

[0087] In the present invention, the onium salt represented by formula (1) may be one type or a mixture of at least two types. Specific examples of the mixture of at least two types include a mixture of 1,3-dimethylimidazolium acetate and 1,3-diethylimidazolium acetate, a mixture of 1,3-dimethylimidazolium acetate and 1-ethyl-3-methylimidazolium acetate, a mixture of 1,3-diethylimidazolium acetate and 1-ethyl-3-methylimidazolium acetate, and a mixture of 1,3-dimethylimidazolium acetate, 1,3-diethylimidazolium acetate and 1-ethyl-3-methylimidazolium acetate.

[0088] In the present invention, The mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) may further contain water and / or a hydrophilic solvent. The hydrophilic solvent refers to a solvent that can be dissolved or miscible in water, and specific examples thereof include lower alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, propanol, and ethylene glycol. The content of water and / or hydrophilic solvent is 0.1% by mass to 90% by mass, 1% by mass to 70% by mass, and preferably 5% by mass to 50% by mass, based on the total amount of the mixture containing the onium salt represented by formula (1), the carboxylic acid represented by formula (3), and the water and / or hydrophilic solvent being 100% by mass.

[0089] One embodiment of the present invention relates to a method for purifying an onium salt represented by formula (1) by removing a carboxylic acid represented by formula (3) from a mixture containing the onium salt represented by formula (1) and a carboxylic acid represented by formula (3), the method including the following steps (1), (2) and (3). Process (1): A step of obtaining a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3) obtained by the reaction represented by formula (2). Process (2): A step of adding an amine to a mixture containing the onium salt represented by formula (1) obtained in step (1) and a carboxylic acid represented by formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid represented by formula (3). Process (3): A step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2) to obtain the onium salt represented by formula (1).

[0090] In the onium salt purification method of the present invention, the onium salt represented by formula (1) is the same as the onium salt represented by formula (1) in the above-mentioned onium salt production method. In addition, in the onium salt represented by formula (1) in the onium salt purification method of the present invention, the imidazolium cation represented by formula (1-1) is the same as the imidazolium cation represented by formula (1-1) in the above-mentioned onium salt production method. In addition, in the onium salt represented by formula (1) in the onium salt purification method of the present invention, the carboxylate anion represented by formula (1-2) is the same as the carboxylate onion represented by formula (1-2) in the above-mentioned onium salt production method.

[0091] In the method for purifying an onium salt of the present invention, the carboxylic acid of formula (3) is the same as the carboxylic acid represented by formula (3) in the above-mentioned method for producing an onium salt.

[0092] In the onium salt purification method of the present invention, the mixture containing the onium salt represented by formula (1) obtained by the reaction of formula (2) in step (1) of the purification method and the carboxylic acid of formula (3) is the same as the mixture containing the onium salt represented by formula (1) and the carboxylic acid of formula (3) obtained by the reaction of formula (2) in step (1) of the above-mentioned onium salt production method.

[0093] In the onium salt purification method of the present invention, the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) obtained by the reaction of formula (2) in step (1) of the purification method is a mixture in which the carboxylic acid of formula (3) used in the reaction of formula (2) remains in the onium salt represented by formula (1). The remaining carboxylic acid of formula (3) is usually 1.5 equivalents or less per equivalent of the onium salt represented by formula (1).

[0094] In the method for purifying an onium salt of the present invention, step (2) is the same as step (2) in the above-mentioned method for producing an onium salt, and is a step of adding an amine to a mixture containing the onium salt represented by formula (1) and a carboxylic acid of formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid of formula (3).

[0095] The amine added in step (2) of the method for purifying an onium salt of the present invention is preferably the amine represented by formula (4) in the above-mentioned method for producing an onium salt.

[0096] In step (2) of the onium salt purification method of the present invention, the amount and preferred amount of the amine added to the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) are the same as the amount and preferred amount of the amine added in the above-mentioned onium salt production method. In step (2) of the onium salt purification method of the present invention, an amine-carboxylate consisting of the added amine and a carboxylic acid of formula (3) is produced, as in step (2) of the above-described onium salt production method, and a mixture of the onium salt represented by formula (1), the amine-carboxylate, and the remaining amine is obtained.

[0097] The amine added in step (2) of the onium salt purification method of the present invention may be added as an amine solution diluted with a solvent, similar to the amine added in step (2) of the above-mentioned onium salt production method. Examples of the solvent include the same solvents as those used in step (2) of the above-mentioned production method, and the concentration of the amine solution may be the same as that in step (2) of the above-mentioned production method.

[0098] In step (2) of the onium salt purification method of the present invention, the reaction conditions for generating an amine-carboxylate by adding an amine to a mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) are the same as the reaction conditions in step (2) of the above-mentioned production method, such as the temperature conditions and reaction time.

[0099] In the method for purifying an onium salt of the present invention, step (3) is the same as step (3) in the above-mentioned method for producing an onium salt, and is a step for separating the onium salt represented by formula (1) from the amine-carboxylate salt produced in step (2). The method for separation is the same as the method used in step (3) in the above-mentioned method for producing an onium salt.

[0100] By the separation in step (3) in the onium salt purification method of the present invention, a separated liquid containing the onium salt represented by formula (1) is obtained. When the separated liquid contains residual amine and / or solvent of the amine solution, the residual amine and / or solvent can be distilled off by heating and / or reducing the pressure of the separated liquid, similarly to step (3) in the above-mentioned onium salt production method.

[0101] In the onium salt purification method of the present invention, the onium salt represented by formula (1) may be one type or a mixture of at least two types. The mixture of at least two types is the same as the mixture of at least two types of onium salt represented by formula (1) in the above-mentioned onium salt production method.

[0102] In the onium salt purification method of the present invention, the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) may further contain water and / or a hydrophilic solvent, as in the above-mentioned method for producing an onium salt. Examples of the hydrophilic solvent include the same hydrophilic solvents as those used in the above-mentioned method for producing an onium salt, and the content of water and / or hydrophilic solvent is also the same as that in the above-mentioned method for producing an onium salt.

[0103] The onium salt produced by the method of the present invention can be used, for example, as a solvent for dissolving cellulose and as a carbon dioxide absorbent. EXAMPLES

[0104] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples.

[0105] [Example 1] A 1L four-necked reactor purged with nitrogen was charged with 113g (1.40mol) of 37wt% formaldehyde aqueous solution (manufactured by Junsei Chemical Co., Ltd.), 126g (2.10mol) of acetic acid (manufactured by Junsei Chemical Co., Ltd.), 250g (2.81mol) of 3-methoxypropylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 202g (1.40mol) of 40wt% glyoxal aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.). The resulting mixture was heated to 40°C and stirred for 3 hours to synthesize 691g of 1,3-bis(3-methoxypropyl)imidazolium acetate aqueous solution ([(MeOPr)2Im][AcO]). Hereinafter, this will be referred to as the reaction solution. The reaction solution 1 H NMR analysis was performed to obtain the integral value of the peaks at 1.55-1.65 ppm derived from acetate ions and acetic acid. The integral value of the peak at 1.55-1.65 ppm was 4.66, based on 1.94-2.14 ppm (quin., 4H). To 10.0 g of the reaction solution, 5.57 g of ion-exchanged water, 10.0 g of chloroform (manufactured by Junsei Chemical Co., Ltd.), and various amines (0.02 mol) shown in Evaluation Examples 1 to 4 in Table 1 were added, stirred, and then separated. About 3 drops of the aqueous layer were added to about 1 g of DMSO-d6, and the mixture was stirred for 1 hour. 1The sample was subjected to H NMR analysis. The integral value of the peak at 1.55-1.65 ppm was obtained based on 1.94-2.14 ppm (quin., 4H) as the standard, and the removal rate (%) of acetic acid was calculated using the following formula. Acetic acid removal rate (%) = (1-(integral value-3.00) / (4.66-3.00)) x 100 In addition, in Evaluation Example 2, since the peak derived from dicyclohexylamine overlaps with the peaks derived from acetate ion and acetic acid, the removal rate was calculated after removing the 2H component derived from the amine. The results are shown in Table 1. The onium salts obtained using the amines of Evaluation Examples 1 to 3 have had acetic acid removed, and therefore all of them can improve the solubility of cellulose compared to the onium salt before acetic acid removal. On the other hand, the onium salt obtained using the amine of Evaluation Example 4 has a low acetic acid removal rate, and therefore it is presumed that the solubility of cellulose is hardly improved at all.

[0106] [Table 1]

[0107] [Example 2] 5.57 g of ion-exchanged water, 10.0 g of 2-ethylhexanol (manufactured by Junsei Chemical Co., Ltd.), and various amines (0.02 mol) shown in Evaluation Examples 5 and 6 in Table 2 were added to 10.0 g of the reaction solution obtained in Example 1, stirred, and then separated. 1 The sample was subjected to H NMR analysis. The integral value of the peaks at 1.55-1.65 ppm derived from acetate ions and acetic acid was obtained based on 1.94-2.14 ppm (quin., 4H) as the standard, and the removal rate (%) of acetic acid was calculated by the following formula. As described in Example 1, the integral value of the peak at 1.55-1.65 ppm in the reaction solution was 4.66. Acetic acid removal rate (%) = (1-(integral value-3.00) / (4.66-3.00)) x 100 In addition, in Evaluation Example 6, since the peak derived from dicyclohexylamine overlaps with the peaks derived from acetate ion and acetic acid, the removal rate was calculated after removing the 2H component derived from the amine. The results are shown in Table 2. The onium salts obtained using the amines of Evaluation Examples 5 to 7 were those from which acetic acid had been removed, and therefore all of them were able to improve the solubility of cellulose compared to the onium salt before removal of acetic acid.

[0108] [Table 2]

[0109] [Example 3] In a nitrogen-substituted 30 mL three-necked reactor, 1.69 g (0.21 mol) of 37 wt% formaldehyde aqueous solution (manufactured by Junsei Chemical Co., Ltd.), 1.83 g (0.30 mol) of acetic acid (manufactured by Junsei Chemical Co., Ltd.), 1.63 g (0.21 mol) of 40% methylamine methanol solution (manufactured by Tokyo Chemical Industry Co., Ltd.), 1.32 g (0.20 mol) of 70% ethylamine aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.), and 2.99 g (0.21 mol) of 40 wt% glyoxal aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.) were charged. The resulting mixture was heated to 40°C and stirred for 3 hours to synthesize 8.97 g of a mixed aqueous solution of 1,3-dimethylimidazolium acetate, 1,3-diethylimidazolium acetate, and 1-ethyl-3-methylimidazolium acetate. Reaction solution 1 H NMR analysis was performed to obtain the integral values ​​of the peaks at 1.55-1.65 ppm derived from acetate ions and acetic acid. The integral value of the peak at 1.55-1.67 ppm was 4.70, based on 7.55-7.75 ppm (m, 2H). To the reaction solution, 5.22 g of ion-exchanged water, 4.77 g of 2-ethylhexanol, and 2.72 g (0.21 mol) of di-2-ethylhexylamine were added, and the mixture was stirred and separated. Add about 3 drops of the aqueous layer to about 1 g of DMSO-d6. 1 The sample was subjected to H NMR analysis. The integral value of the peak from 1.55 to 1.67 ppm was obtained based on 7.55 to 7.75 ppm (m, 2H) as the standard, and the removal rate (%) of acetic acid was calculated using the following formula. Acetic acid removal rate (%) = (1-(integral value-3.00) / (4.70-3.00)) x 100 The results are shown in Table 3. The onium salt obtained using the amine of Evaluation Example 8 is one from which acetic acid has been removed, and therefore the solubility of cellulose can be improved compared to the onium salt before removal of acetic acid.

[0110] [Table 3]

[0111] [Example 4] A 300 L four-necked reactor purged with nitrogen was charged with 28.40 g (0.35 mol) of 37 wt% formaldehyde aqueous solution (manufactured by Junsei Chemical Co., Ltd.), 31.59 g (0.53 mol) of acetic acid (manufactured by Junsei Chemical Co., Ltd.), 62.31 g (0.70 mol) of 3-methoxypropylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 50.45 g (0.35 mol) of 40 wt% glyoxal aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.). The resulting mixture was heated to 40°C and stirred for 3 hours to synthesize 172 g of 1,3-bis(3-methoxypropyl)imidazolium acetate aqueous solution ([(MeOPr)2Im][AcO]). Hereinafter, this will be referred to as the reaction solution. The reaction solution was concentrated as is. 1 H NMR analysis and cellulose dissolution tests were carried out. 1 As a result of 1 H NMR analysis, the integral value of the peaks derived from acetate ion and acetic acid based on 1.94-2.14 ppm (quin., 4H) was 4.49. <Acetic acid removal> To the reaction solution (15.0 g), ion-exchanged water (8.36 g), chloroform (15.0 g) (manufactured by Junsei Chemical Co., Ltd.), and various amines (0.03 mol) shown in Table 4 were added, and the mixture was stirred and allowed to stand (80°C, 1 hour each). After separation, the lower layer was concentrated, 1 H NMR analysis and a cellulose dissolution test were carried out. Hereinafter, these are referred to as Evaluation Examples 9 to 11 and Comparative Example 2. In addition, in Comparative Example 1, a cellulose dissolution test was carried out in the same manner as above, except that no amine was used. In the NMR analysis, the integral value of the peak derived from acetic acid was confirmed. The integral value of the peak from 1.55 to 1.65 ppm was obtained based on 1.94 to 2.14 ppm (quin., 4H) as the standard, and the removal rate (%) of acetic acid was calculated from the integral value. The formula is as follows. Acetic acid removal rate (%) = (1-(integral value-3.00) / (4.49-3.00)) x 100 In addition, in Evaluation Example 10, since the peak derived from dicyclohexylamine overlaps with the peak derived from acetic acid, the removal rate was calculated after removing the 2H component derived from the amine. The results are shown in Table 5. <Dissolution test> In the dissolution test, the dissolution of microcrystalline cellulose (10 wt% vs. concentrated solution) (Avicel (registered trademark) PH-101, manufactured by Sigma-Aldrich Co. LLC) was confirmed at 25°C. The concentrated solution of the reaction solution (Comparative Example 1) and the concentrated solutions (1.0 g) of Evaluation Examples 9 to 11 and Comparative Example 2 were placed in test tubes, and microcrystalline cellulose (10 wt% vs. concentrated solution) was added at 25°C and stirred. After 24 hours, the dissolution of the microcrystalline cellulose was visually confirmed. Crystalline cellulose that was completely dissolved was marked with an ◯, and that was not completely dissolved was marked with an ×. The dissolution results are shown in Table 5.

[0112] [Example 5] <Acetic acid removal> To the reaction solution (15.0 g) obtained in Example 4, ion-exchanged water (8.36 g), 2-ethylhexanol (15.0 g) (manufactured by Junsei Chemical Co., Ltd.), and various amines (0.03 mol) shown in Table 1 were added, and the mixture was stirred and allowed to stand (80° C., 1 hour each). After separation, the lower layer was concentrated, 1 1 H NMR analysis and a dissolution test were carried out. These are hereinafter referred to as Evaluation Examples 12 to 14. In the NMR analysis, the integral value of the peak derived from acetic acid was confirmed. The integral value of the peak from 1.55 to 1.65 ppm was obtained based on 1.94 to 2.14 ppm (quin., 4H) as the standard, and the removal rate (%) of acetic acid was calculated from the integral value. The formula is as follows. Acetic acid removal rate (%) = (1-(integral value-3.00) / (4.49-3.00)) x 100 In addition, in Evaluation Example 13, since the peak derived from dicyclohexylamine overlaps with the peak derived from acetic acid, the removal rate was calculated after removing the 2H component derived from the amine. The results are shown in Table 6. <Dissolution test> In the dissolution test, the dissolution of microcrystalline cellulose (10 wt% vs. concentrated solution) (Avicel (registered trademark) PH-101, manufactured by Sigma-Aldrich Co. LLC) was confirmed at 25°C. The concentrates (1.0 g) of Evaluation Examples 12 to 14 were placed in test tubes, and microcrystalline cellulose (10 wt% vs. concentrate) was added at 25°C and stirred. After 24 hours, the dissolution of the microcrystalline cellulose was visually confirmed. Crystalline cellulose that was completely dissolved was marked with an ◯, and that was not completely dissolved was marked with an ×. The dissolution results are shown in Table 6.

[0113] [Table 4]

[0114] [Table 5]

[0115] [Table 6] [Industrial Applicability]

[0116] According to the present invention, there can be provided a method for producing an onium salt that does not contain a carboxylic acid or an onium salt in which the carboxylic acid content is reduced to such an extent that sufficient solubility of cellulose in the onium salt is obtained. Furthermore, according to the present invention, a method for purifying an onium salt can be provided, which removes a carboxylic acid contained in the onium salt, or reduces the content of the carboxylic acid to an extent that sufficient solubility of cellulose in the onium salt can be obtained.

Claims

1. A method for producing an onium salt represented by the following formula (1), comprising the following steps (1), (2) and (3). Formula (1): 【Chemistry 1】 (In formula (1), R 1 , R 2 , R 3 , R 4 and R 5 R may be the same or different and represents a hydrogen atom or a hydrocarbon group which may contain a heteroatom. 1 , R 2 , R 3 , R 4 and R 5 may contain branched and / or cyclic structures and / or double bonds, R 1 , R 2 , R 3 , R 4 and R 5 Part or all of 1 , R 2 , R 3 , R 4 and R 5 may be bonded together with the nitrogen atom and carbon atom to which they are attached to form a ring structure. In addition, in formula (1), R 6 represents a hydrocarbon group which may contain a heteroatom, and may contain a double bond and / or a ring structure and / or a branched structure. Process (1): A step of obtaining a mixture containing an onium salt represented by formula (1) and a carboxylic acid represented by formula (3) below, which is obtained by a reaction formula represented by formula (2) below. Formula (2): 【Chemistry 2】 Formula (3): 【Chemistry 3】 (In formula (3), R 6 represents a hydrocarbon group which may contain a heteroatom, and may contain a double bond and / or a ring structure and / or a branched structure. Process (2): A step of adding an amine to a mixture containing the onium salt represented by formula (1) obtained in step (1) and a carboxylic acid represented by formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid represented by formula (3). Process (3): A step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2) to obtain the onium salt represented by formula (1).

2. The method for producing an onium salt according to claim 1, wherein the amine added in the step (2) is an amine represented by the following formula (4): Formula (4): 【Chemistry 4】 (In formula (4), R 7 , R 8 and R 9 may be the same or different and are a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and the hydrocarbon group may contain a double bond and may contain a branched structure and / or a ring structure. 7 , R 8 and R 9 The total number of carbon atoms contained in each of is 8 or more.)

3. The method for producing an onium salt according to claim 1, wherein the onium salt represented by formula (1) is of at least two types.

4. The method for producing an onium salt according to claim 1, wherein the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) further contains water and / or a hydrophilic solvent.

5. The method for producing an onium salt according to claim 1, wherein the amine added in step (2) is an amine solution diluted with a solvent.

6. A method for purifying an onium salt represented by the following formula (1), which comprises removing a carboxylic acid of the following formula (3) from a mixture containing the onium salt represented by the following formula (1) and a carboxylic acid of the following formula (3), the method comprising the following steps (1), (2) and (3): Formula (1): 【Chemistry 5】 (In formula (1), R 1 , R 2 , R 3 , R 4 and R 5 R may be the same or different and represents a hydrogen atom or a hydrocarbon group which may contain a heteroatom. 1 , R 2 , R 3 , R 4 and R 5 may contain branched and / or cyclic structures and / or double bonds, R 1 , R 2 , R 3 , R 4 and R 5 Part or all of 1 , R 2 , R 3 , R 4 and R 5 may be bonded together with the nitrogen atom and carbon atom to which they are attached to form a ring structure. In addition, in formula (1), R 6 represents a hydrocarbon group which may contain a heteroatom, and may contain a double bond and / or a ring structure and / or a branched structure. Process (1): A step of obtaining a mixture containing an onium salt of formula (1) and a carboxylic acid of formula (3) obtained by the reaction of formula (2) below. Formula (2): 【Chemistry 6】 Formula (3): 【Chemistry 7】 (In formula (3), R 6 represents a hydrocarbon group which may contain a heteroatom, and may contain a double bond and / or a ring structure and / or a branched structure. Process (2): A step of adding an amine to the mixture containing the onium salt of formula (1) obtained in step (1) and the carboxylic acid of formula (3) to produce an amine-carboxylate consisting of the amine and the carboxylic acid of formula (3). Process (3): A step of separating the onium salt represented by formula (1) from the amine-carboxylate produced in step (2) to obtain the onium salt represented by formula (1).

7. The method for purifying an onium salt according to claim 6, wherein the amine added in the step (2) is an amine represented by the following formula (4): Formula (4): 【Chemistry 8】 (In formula (4), R 7 , R 4 and R 9 may be the same or different and are a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and the hydrocarbon group may contain a double bond and may contain a branched structure and / or a ring structure. 7 , R 8 and R 9 The total number of carbon atoms contained in each of is 8 or more.)

8. The method for purifying an onium salt according to claim 6, wherein the onium salt represented by formula (1) is of at least two types.

9. The method for purifying an onium salt according to claim 6, wherein the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (3) further contains water and / or a hydrophilic solvent.

10. 7. The method for purifying an onium salt according to claim 6, wherein the amine added in step (2) is an amine solution diluted with a solvent.

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