Method for producing esterified polysaccharide

Abstract

To provide a method for producing an esterified polysaccharide, the method being capable of recycling a recovery liquid containing an onium salt by removing or reducing carboxylic acid without substantially using a catalyst for esterifying cellulose.SOLUTION: The method for producing an esterified polysaccharide comprises the following steps (1) to (8): (1) dissolving a polysaccharide in an onium salt, (2) adding an esterifying agent, (3) adding a solvent to precipitate an esterified polysaccharide, (4) filtering the esterified polysaccharide, (5) removing the solvent from the filtrate, (6) adding an amine to separate the onium salt from the amine-carboxylic acid salt, (7) recovering the onium salt, and (8) recycling the recovered onium salt.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing an esterified polysaccharide.

Background Art

[0002] The protection and maintenance of the global environment or the natural environment are required, and there is a demand for chemical substances and functional materials that have a low environmental impact or can reduce the impact. As such, natural polymers, particularly polysaccharides or polysaccharide derivatives, have attracted attention.

[0003] Among polysaccharides, cellulose is used in applications such as films, fibers, and pharmaceuticals. Also, cellulose derivatives are used in a wide range of commercial applications. Generally, cellulose is a β-1,4-linked polymer of glucose as a structural unit, and is a polymer of anhydroglucose. Also, a cellulose derivative is a compound in which at least a part of three hydroxyl groups present in glucose, which is a structural unit of cellulose, is derivatized into another functional group. In addition, esterified products of cellulose obtained by esterifying cellulose and esterified products of cellulose derivatives obtained by esterifying hydroxyl groups remaining in cellulose derivatives are also used in a wide range of commercial applications.

[0004] And, as a method for producing an esterified product of cellulose, for example, Patent Document 1 describes a method for producing a cellulose ester in which cellulose is dissolved in a carboxylated ionic liquid, the cellulose solution is contacted in the presence of an acylating reagent and a catalyst to prepare a solution containing a cellulose ester, the solution is contacted with a non-solvent to precipitate the cellulose ester, the precipitated cellulose ester is separated from the carboxylated ionic liquid to recover the cellulose ester, and the separated carboxylated ionic liquid is recycled for use in dissolving cellulose.

Prior Art Documents

Patent Documents

[0005] Patent Document 1 Japanese Patent Application Laid-Open No. 2010-518244 Summary of the Invention Problems to be Solved by the Invention

[0006] The method for producing a cellulose ester described in Patent Document 1 is a production method in which an acylating reagent is used to esterify cellulose, and specifically, methanesulfonic acid, which is a protonic acid, is used as a catalyst to increase the rate of esterification. The catalyst may remain in the esterified cellulose, and if it remains, there is a concern that it may affect the quality of the esterified cellulose that becomes the product. Specifically, acetic anhydride is used as the acylating reagent. After acylating cellulose, methanol is added to remove the remaining acetic acid as methyl acetate because acetic acid remains. However, it cannot be said that the removal or reduction of the remaining acetic acid is sufficient, and further removal or reduction of acetic acid is required for the recycling of the carboxylated ionic liquid. Therefore, a catalyst is required to esterify cellulose, and further removal or reduction of acetic acid is an issue.

[0007] In view of the prior art situation as described above, an object of the present invention is to provide a method for producing an esterified polysaccharide, preferably a method for producing an esterified cellulose, which substantially does not use a catalyst for esterifying cellulose and can further remove or reduce a carboxylic acid. Means for Solving the Problems

[0008] The present inventors have intensively studied a method for producing an esterified polysaccharide that substantially does not use a catalyst for esterifying cellulose and can further remove or reduce a carboxylic acid, and have completed the present invention.

[0009] That is, the present invention provides the following [1] to [7]. [1] A method for producing an esterified polysaccharide having the following steps (1) to (8). Step (1): A step of mixing an onium salt represented by formula (1) and a polysaccharide and dissolving the polysaccharide in the onium salt. (Formula 1):

Chemical formula

Chemical formula

Chemical formula

[0010] According to the present invention, there is provided a method for producing an esterified polysaccharide that can substantially eliminate the use of a catalyst for esterifying cellulose and can further remove or reduce carboxylic acid, and a recovered liquid containing an onium salt recovered by the production method can be recycled. [Embodiments for Carrying Out the Invention]

[0011] Hereinafter, the present invention will be specifically described. One embodiment of the present invention relates to a method for producing an esterified polysaccharide having the following steps (1) to (8). Step (1): A step of mixing an onium salt represented by formula (1) and a polysaccharide and dissolving the polysaccharide in the onium salt. (Formula 1):

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0012] The onium salt represented by the following formula (1) used in step (1) of the production method of the present invention will be described. Formula (1):

Chemical formula

[0013] The onium salt represented by formula (1) is composed of an imidazolium cation represented by the following formula (1-1) and a carboxylic acid anion represented by the following formula (1-2). Formula (1-1):

Chemical formula

Chemical formula

[0014] The imidazolium cation represented by the following formula (1-1) will be described. Formula (1-1):

Chemical formula

[0015] In formula (1) and formula (1-1), R 1 , R 2 represent the same or different hydrocarbon groups which may contain heteroatoms. R 1 , R2 may contain a branch, a ring structure, or a double bond. R 3 is a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms.)

[0016] In Formula (1) and Formula (1-1), R 1 , R 2 will be described for the case where it is "a hydrocarbon group containing no heteroatom".

[0017] In Formula (1) and Formula (1-1), R 1 , R 2 When is "a hydrocarbon group containing no heteroatom", the number of carbon atoms of the hydrocarbon group is preferably 1 to 12, more preferably 1 to 8, and still more preferably 1 to 3. The hydrocarbon group may be linear, and may contain a branch, a ring structure, or a double bond.

[0018] In Formula (1) and Formula (1-1), R 1 , R 2 Examples of "a hydrocarbon group containing no heteroatom" for R, R include an alkyl group having a straight chain or a branch and containing no heteroatom, an alkenyl group having a straight chain or a branch and containing no heteroatom, an alkynyl group having a straight chain or a branch and containing no heteroatom, a cycloalkyl group which may have a branch and contains no heteroatom, a cycloalkenyl group which may have a branch and contains no heteroatom, an aryl group which may have a branch and contains no heteroatom, an aralkyl group which may have a branch and contains no heteroatom, and the like. Preferably, it is an alkyl group having a straight chain or a branch and containing no heteroatom, an alkenyl group having a straight chain or a branch and containing no heteroatom, or a cycloalkyl group which may have a branch and contains no heteroatom.

[0019] In Formula (1) and Formula (1-1), R 1 , R 2In the formula, the "alkyl group having a straight chain or a branch and containing no heteroatom" is preferably an alkyl group having a straight chain or a branch and having 1 to 12 carbon atoms and containing no heteroatom, more preferably an alkyl group having a straight chain or a branch and having 1 to 8 carbon atoms and containing no heteroatom, still more preferably an alkyl group having a straight chain or a branch and having 1 to 4 carbon atoms and containing no heteroatom, and even more preferably an alkyl group having a straight chain or a branch and having 1 to 3 carbon atoms and containing no heteroatom.

[0020] In formulas (1) and (1-1), R 1 , R 2 In the formula, the "alkenyl group having a straight chain or a branch and containing no heteroatom" is preferably an alkenyl group having a straight chain or a branch and having 2 to 12 carbon atoms and containing no heteroatom, more preferably an alkenyl group having a straight chain or a branch and having 2 to 8 carbon atoms and containing no heteroatom, still more preferably an alkenyl group having a straight chain or a branch and having 2 to 4 carbon atoms and containing no heteroatom, and even more preferably an alkenyl group having a straight chain or a branch and having 2 to 3 carbon atoms and containing no heteroatom.

[0021] In formulas (1) and (1-1), R 1 , R 2 In the formula, the "cycloalkyl group which may have a branch and contains no heteroatom" is preferably a cycloalkyl group which may have a branch and has 3 to 12 carbon atoms and contains no heteroatom, more preferably a cycloalkyl group which may have a branch and has 3 to 8 carbon atoms and contains no heteroatom, still more preferably a cycloalkyl group which may have a branch and has 3 to 4 carbon atoms and contains no heteroatom, and even more preferably a cycloalkyl group having 3 carbon atoms.

[0022] 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.

[0023] In formula (1) and formula (1-1), R 1 , R 2 The case where the group is a "hydrocarbon group containing a hetero atom" will be described below.

[0024] In formula (1) and formula (1-1), R 1 , R 2 When is a hydrocarbon group containing a hetero atom, the number of carbon atoms is preferably 2 to 12, more preferably 2 to 8, and further preferably 2 to 4. The hydrocarbon group may be linear, or may contain a branched or cyclic structure or a double bond.

[0025] In formula (1) and formula (1-1), R 1 , R 2 is a "hydrocarbon group containing a hetero atom", examples of the "hetero atom" include a nitrogen atom, an oxygen atom, a sulfur atom, etc. The number of hetero atoms is preferably 1 to 5, and more preferably 1 to 2.

[0026] In formula (1) and formula (1-1), R 1 , R 2In this case, the "hydrocarbon group containing a heteroatom" is a hydrocarbon group without a heteroatom, where (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 substituted by structures such as -O-, -N<, -NH-, -S-, -C(=O)-O-, -C(=O)-, =N-, -C(=O)-N<, -C(=O)-NH-, -O-C(=O)-O-, -O-C(=O)-N<, -O-C(=O)-NH-, -C(=O)-N[-C(=O)-]-, -C(=O)-NH-C(=O)-, >N-C(=O)-N<, >N-C(=O)-NH-, -HN-C(=O)-NH-, -S(=O)-, -S(=O)2-, -S(=O)2-O-, -O-S(=O)2-O-, >N-C(=S)-N<, >N-C(=S)-NH-, -HN-C(=S)-NH-, -C(=N-)-, -C(=NH)-, etc. The number and combination of substitutions by these structures are not particularly limited, but R 1 , R 2 preferably contains 1 to 5 heteroatoms, more preferably 1 to 2 heteroatoms.

[0027] Preferably, (i) the bond between two adjacent carbon atoms of the hydrocarbon group, and / or (ii) the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of another -CH2- (methylene group) are substituted by a -O- or -S- structure, and more preferably by an -O- structure.

[0028] In the present invention, as the structure in which (i) the bond between two adjacent carbon atoms of the hydrocarbon group, and / or (ii) the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of another -CH2- (methylene group) are substituted by a -O- or -S- structure, in addition to the -O- structure (ether structure) and -S- structure (thioether structure), for example, epoxy structures or thioepoxy structures such as epoxy groups, thioepoxy groups, glycidyl ether groups, epoxycyclohexyl groups, etc. may be formed. In this case, R 1 , R 2 may be an epoxy group, a thioepoxy group, etc.

[0029] R 1 、R 2 In R and R, when containing two or more -O- or / and -S- structures, the number of carbon atoms between the -O- or / and -S- structures is desirably 2 or more.

[0030] In Formula (1) and Formula (1-1), as the "hydrocarbon group containing a heteroatom" for R1 and R2, examples include an alkyl group having a straight chain or branch containing a heteroatom, an alkenyl group having a straight chain or branch containing a heteroatom, an alkynyl group having a straight chain or branch containing a heteroatom, a cycloalkyl group which may have a branch containing a heteroatom, a cycloalkenyl group which may have a branch containing a heteroatom, an aryl group which may have a branch containing a heteroatom, an aralkyl group which may have a branch containing a heteroatom, and the like. Preferably, it is an alkyl group having a straight chain or branch containing a heteroatom, an alkenyl group having a straight chain or branch containing a heteroatom, or a cycloalkyl group which may have a branch containing a heteroatom.

[0031] The "alkyl group having a straight chain or branch containing a heteroatom" is preferably an alkyl group having a straight chain or branch with 1 to 12 carbon atoms and containing 1 to 5 heteroatoms. In another aspect, preferably, it is an alkyl group having a straight chain or branch with 1 to 12 carbon atoms and containing 1 to 2 heteroatoms, more preferably an alkyl group having a straight chain or branch with 1 to 8 carbon atoms and containing 1 to 2 heteroatoms, and even more preferably an alkyl group having a straight chain or branch with 1 to 4 carbon atoms and containing 1 to 2 heteroatoms.

[0032] The "alkenyl group having a straight chain or branch containing a heteroatom" is preferably an alkenyl group having a straight chain or branch with 2 to 12 carbon atoms and containing 1 to 5 heteroatoms. In another preferred embodiment, it is an alkenyl group having a straight or branched chain with 2 to 12 carbon atoms and containing 1 to 2 heteroatoms, more preferably an alkenyl group having a straight or branched chain with 2 to 8 carbon atoms and containing 1 to 2 heteroatoms, and even more preferably an alkenyl group having a straight or branched chain with 2 to 4 carbon atoms and containing 1 to 2 heteroatoms.

[0033] The "cycloalkyl group which may have a branch containing a heteroatom" is preferably a cycloalkyl group which may have a branch with 3 to 12 carbon atoms and contains 1 to 5 heteroatoms. In another preferred embodiment, it is preferably a cycloalkyl group which may have a branch with 3 to 12 carbon atoms and contains 1 to 2 heteroatoms, more preferably a cycloalkyl group which may have a branch with 3 to 8 carbon atoms and contains 1 to 2 heteroatoms, and even more preferably a cycloalkyl group which may have a branch with 3 to 4 carbon atoms and contains 1 to 2 heteroatoms.

[0034] In formulas (1) and (1-1), R 1 , R 2Specific examples of the "hydrocarbon group containing a heteroatom" include 2-methoxyethyl, 2-ethoxyethyl, 2-propoxyethyl, 2-isopropoxyethyl, 2-phenoxyethyl, 2-(benzyloxy)ethyl, 2-(p-methoxybenzyloxy)ethyl, 2-(2-methoxyethoxymethoxy)ethyl, 2-(2-benzyloxyethoxy)ethyl, 2-(dimethylamino)ethyl, 3-methoxypropyl, 3-ethoxypropyl, 3-propoxypropyl, 3-allyloxypropyl, 3-isopropoxypropyl, 3-(1-methylpropoxy)propyl, 3-(2-methylpropoxy)propyl, 3-(1,1-dimethylethoxy)propyl, 3-butoxypropyl, 3-pentyloxypropyl, 3-neopentyloxypropyl, 3-hexyloxypropyl, 3-cyclohexyloxypropyl, 3-heptyloxypropyl, 3-octyloxypropyl, 3-nonyloxypropyl, 3-(2-ethylhexan-1-yl)oxypropyl, 3-(2,4,6-trimethylphenoxy)propyl, 3-(2-methoxyethoxy)propyl, 3-(dimethylamino)propyl, 4-methoxybutyl, 4-ethoxybutyl, 4-propoxybutyl, 4-isopropoxybutyl, 4-allyloxybutyl, 4-butoxybutyl, 4-(1-methylpropoxy)butyl, 4-(2-methylpropoxy)butyl, 4-(1,1-dimethylethoxy)butyl, 4-pentyloxybutyl, 4-neopentyloxybutyl, 4-hexyloxybutyl, 4-cyclohexyloxybutyl, 4-heptyloxybutyl, 4-octyloxybutyl, 4-(2-ethylhexan-1-yl)oxybutyl, 5-methoxypentyl, 5-ethoxypentyl, 5-propoxypentyl, 5-isopropoxypentyl, 5-allyloxypentyl, 5-butoxypentyl, 5-(1-methylpropoxy)pentyl, 5-(2-methylpropoxy)pentyl, 5-(1,(1 - dimethylethoxy)pentyl, 5 - pentyloxypentyl, 5 - neopentyloxypentyl, 5 - hexyloxypentyl, 5 - cyclohexyloxypentyl, 5 - heptyloxypentyl, 6 - methoxyhexyl, 6 - ethoxyhexyl, 6 - propoxyhexyl, 6 - isopropoxyhexyl, 6 - allyloxyhexyl, 6 - butoxyhexyl, 6-(1 - methylpropoxy)hexyl, 6-(2 - methylpropoxy)hexyl, 6-(1,1 - dimethylethoxy)hexyl, 6 - pentyloxypentyl, 6 - neopentyloxypentyl, 6 - hexyloxypentyl, 6 - cyclohexyloxypentyl, (2 - methoxycyclohexan - 1 - yl)methyl, (2 - ethoxycyclohexan - 1 - yl)methyl, (2 - propoxycyclohexan - 1 - yl)methyl, (2 - isopropoxycyclohexan - 1 - yl)methyl, (2 - butoxycyclohexan - 1 - yl)methyl, [2-(1 - methylpropoxy)cyclohexan - 1 - yl]methyl, [2-(2 - methylpropoxy)cyclohexan - 1 - yl]methyl, [2-(1,1 - dimethylethoxy)cyclohexan - 1 - yl]methyl, (2 - pentyloxypentyl)methyl, (2 - neopentyloxypentyl)methyl, 2 - methylthioethyl, 3 - methylthiopropyl, 1-(methoxymethyl)propyl, (oxolan - 2 - yl)methyl, (furan - 2 - yl)methyl, 2 - [(furan - 2 - yl)methylthio]ethyl, 2-(methylsulfonyl)ethyl, (thiophen - 2 - yl)methyl, p - methoxyphenyl, p - ethoxyphenyl, 3,4 - methylenedioxyphenyl, 3,4 - methylenedioxybenzyl, (7 - oxabicyclo[2,2,1]heptan - 2 - yl)methyl, etc. are mentioned. Preferably, they are 2 - methoxyethyl, 3 - methoxypropyl, 3 - ethoxypropyl, 3 - isopropoxypropyl, 3 - butoxypropyl, 3-(2 - methoxyethoxy)propyl, 3 - methylthiopropyl, 3-(dimethylamino)propyl, more preferably 2 - methoxyethyl, 3 - methoxypropyl, 3-(2 - methoxyethoxy)propyl, but the present invention is not limited thereto.,

[0035] In Formula (1) and Formula (1-1), R 3 is a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. The number of carbon atoms of the hydrocarbon group is preferably 1 to 3. The hydrocarbon group may be linear, and may contain a branch, a ring structure, a double bond, or a triple bond.

[0036] In Formula (1) and Formula (1-1), R 3 Examples of the "hydrocarbon group having 1 to 5 carbon atoms" include, but are not particularly limited to, an alkyl group, an alkenyl group, an alkynyl group, and a cycloalkyl group.

[0037] Preferably, the alkyl group is a linear or branched alkyl group having 1 to 5 carbon atoms, more preferably a linear or branched alkyl group having 1 to 3 carbon atoms.

[0038] Preferably, the alkenyl group is a linear or branched alkenyl group having 2 to 5 carbon atoms, more preferably a linear or branched alkenyl group having 2 to 3 carbon atoms.

[0039] Preferably, the cycloalkyl group is a cycloalkyl group which may have a branch having 3 to 5 carbon atoms, more preferably a cycloalkyl group having 3 carbon atoms.

[0040] In Formula (1) and Formula (1-1), R 3 Specific examples of the "hydrocarbon group having 1 to 5 carbon atoms" 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 vinyl group, an ethynyl group, a propenyl group, an isopropenyl group, etc. Preferably, they are 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 more preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, a tert-butyl group.

[0041] In formula (1-1), examples of the imidazolium cation having a hydrocarbon group not containing a heteroatom 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-methyl-3-octylimidazolium, 1-methyl-3-nonylimidazolium, 1-decyl-3-methylimidazolium, 1,3-diallylimidazolium, 1-allyl-3-methylimidazolium, 1-allyl-3-ethylimidazolium, etc. Preferably, they are 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,3-diethylimidazolium, 1-butyl-3-methylimidazolium, but the present invention is not limited thereto.

[0042] In formula (1-1), examples of the imidazolium cation 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, 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, 1,3-bis(3-octyloxypropyl)imidazolium, 1,3-bis(3-nonyloxypropyl)imidazolium, 1,3-bis{3-[(2-ethylhexan-1-yl)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, 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, 1,3 - bis(4 - heptyloxybutyl)imidazolium, 1,3 - bis(4 - octyloxybutyl)imidazolium, 1,3 - bis{4 - [(2 - ethylhexan - 1 - yl)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, etc. may be mentioned, preferably 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, 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, and 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, 1,3-bis(3-methoxypropyl)-2-methylimidazolium, but the present invention is not limited thereto.,

[0043] In formula (1), the carboxylic acid anion represented by the following formula (1-2) will be described. Formula (1-2):

Chemical formula

[0044] In Formula (1) and Formula (1-2), R 4 represents a hydrocarbon group having 1 to 12 carbon atoms, and may contain a hetero atom, a double bond, a branched structure, or a ring structure.

[0045] In Formula (1) and Formula (1-2), R 4 The number of carbon atoms of the "hydrocarbon group having 1 to 12 carbon atoms" in R is preferably 1 to 8, more preferably 1 to 3. The hydrocarbon may be linear, and may contain a branch, a ring structure, or a double bond.

[0046] In Formula (1) and Formula (1-2), R 4 The "hydrocarbon group having 1 to 12 carbon atoms" in R includes a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched alkenyl group having 2 to 12 carbon atoms, a linear or branched alkynyl group having 2 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms which may have a branch, a cycloalkenyl group having 3 to 12 carbon atoms which may have a branch, an aryl group having 6 to 12 carbon atoms which may have a branch, an aralkyl group having 7 to 12 carbon atoms which may have a branch, and the like. Preferably, it is a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched alkenyl group having 2 to 12 carbon atoms, or a cycloalkyl group having 3 to 12 carbon atoms which may have a branch.

[0047] In Formula (1) and Formula (1-1), R 4 The "linear or branched alkyl group having 1 to 12 carbon atoms" in R is preferably a linear or branched alkyl group having 1 to 8 carbon atoms, more preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and still more preferably a linear or branched alkyl group having 1 to 3 carbon atoms.

[0048] In Formula (1) and Formula (1-1), R 4In this case, the "alkenyl group having 2 to 12 carbon atoms and being linear or branched" is preferably an alkenyl group having 2 to 8 carbon atoms and being linear or branched, more preferably an alkenyl group having 2 to 4 carbon atoms and being linear or branched, and still more preferably an alkenyl group having 2 to 3 carbon atoms and being linear or branched.

[0049] In formulas (1) and (1-1), R 4 In this case, the "cycloalkyl group having 3 to 12 carbon atoms and optionally having a branch" is preferably a cycloalkyl group having 3 to 8 carbon atoms and optionally having a branch, more preferably a cycloalkyl group having 3 to 4 carbon atoms and optionally having a branch, and still more preferably a cycloalkyl group having 3 carbon atoms.

[0050] In formulas (1) and (1-2), R 4 In this case, the "hydrocarbon group having 1 to 12 carbon atoms" specifically includes 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 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, a 2,4,6-trimethylphenyl group, etc. Preferably, it is 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, and more preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, a tert-butyl group.

[0051] In formulas (1) and (1-1), R 4 The case where R is a "hydrocarbon group containing a hetero atom" will be described.

[0052] In formulas (1) and (1-2), R 4When it is a "hydrocarbon group containing a heteroatom", the hydrocarbon group may be linear, and may contain a branch, a ring structure, or a double bond.

[0053] In formulas (1) and (1-2), R 4 When it is a hydrocarbon group containing a heteroatom, the number of carbon atoms is preferably 2 to 12, more preferably 2 to 8, and even more preferably 2 to 4.

[0054] In formulas (1) and (1-2), R 4 When it is a hydrocarbon group containing a heteroatom, the number of heteroatoms is preferably 1 to 5, more preferably 1 to 2. Examples of the "heteroatom" include a nitrogen atom, an oxygen atom, and a sulfur atom.

[0055] In formulas (1) and (1-2), R 4 In R, the "hydrocarbon group containing a heteroatom" is a hydrocarbon group not containing a heteroatom which is substituted by (i) a bond between two adjacent carbon atoms, and / or (ii) a hydrogen atom of one -CH2- (methylene group) and a hydrogen atom of another -CH2- (methylene group) with a structure such as -O-, -N<, -NH-, -S-, -C(=O)-O-, -C(=O)-, =N-, -C(=O)-N<, -C(=O)-NH-, -O-C(=O)-O-, -O-C(=O)-N<, -O-C(=O)-NH-, -C(=O)-N[-C(=O)-]-, -C(=O)-NH-C(=O)-, >N-C(=O)-N<, >N-C(=O)-NH-, -HN-C(=O)-NH-, -S(=O)-, -S(=O)2-, -S(=O)2-O-, -O-S(=O)2-O-, >N-C(=S)-N<, >N-C(=S)-NH-, -HN-C(=S)-NH-, -C(=N-)-, -C(=NH)-, etc. The number and combination of substitutions by these structures are not particularly limited.

[0056] Preferably, the bond between two adjacent carbon atoms of the hydrocarbon group (i) and / or the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of another -CH2- (methylene group) are substituted by the structure of -O- or -S-, more preferably substituted by the structure of -O-.

[0057] In formula (1) and formula (1-2), R 4 In this case, as the structure in which the bond between two adjacent carbon atoms of the hydrocarbon group (i) and / or the hydrogen atom of one -CH2- (methylene group) and the hydrogen atom of another -CH2- (methylene group) are substituted by the structure of -O- or -S-, in addition to the -O- structure (ether structure) and the -S- structure (thioether structure), for example, an epoxy structure or a thioepoxy structure such as an epoxy group, a thioepoxy group, a glycidyl ether group, an epoxycyclohexyl group may be formed.

[0058] In formula (1) and formula (1-2), R 4 In this case, when two or more structures of -O- or / and -S- are included, the number of carbon atoms between the structures of -O- or / and -S- is preferably 2 or more.

[0059] In formula (1) and formula (1-2), R 4 In this case, the "hydrocarbon group containing a heteroatom" includes a linear or branched alkyl group containing a heteroatom, a linear or branched alkenyl group containing a heteroatom, a linear or branched alkynyl group containing a heteroatom, a cycloalkyl group which may have a branch containing a heteroatom, a cycloalkenyl group which may have a branch containing a heteroatom, an aryl group which may have a branch containing a heteroatom, an aralkyl group which may have a branch containing a heteroatom, and the like. Preferably, it is a linear or branched alkyl group containing a heteroatom, a linear or branched alkenyl group containing a heteroatom, or a cycloalkyl group which may have a branch containing a heteroatom.

[0060] The "alkyl group having a straight chain or a branch and containing a heteroatom" is preferably an alkyl group having a straight chain or a branch, containing 1 to 5 heteroatoms and having 1 to 12 carbon atoms. In another aspect, it is preferably an alkyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 1 to 12 carbon atoms, more preferably an alkyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 1 to 8 carbon atoms, and still more preferably an alkyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 1 to 4 carbon atoms.

[0061] The "alkenyl group having a straight chain or a branch and containing a heteroatom" is preferably an alkenyl group having a straight chain or a branch, containing 1 to 5 heteroatoms and having 2 to 12 carbon atoms. In another aspect, it is preferably an alkenyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 2 to 12 carbon atoms, more preferably an alkenyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 2 to 8 carbon atoms, and still more preferably an alkenyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 2 to 4 carbon atoms.

[0062] The "cycloalkyl group which may have a branch and contains a heteroatom" is preferably a cycloalkyl group which may have a branch, contains 1 to 5 heteroatoms and has 3 to 12 carbon atoms. In another aspect, it is preferably a cycloalkyl group which may have a branch, contains 1 to 2 heteroatoms and has 3 to 12 carbon atoms, more preferably a cycloalkyl group which may have a branch, contains 1 to 2 heteroatoms and has 3 to 8 carbon atoms, and still more preferably a cycloalkyl group which may have a branch, contains 1 to 2 heteroatoms and has 3 to 4 carbon atoms.

[0063] In Formula (1) and Formula (1-2), R 4 The "hydrocarbon group containing a heteroatom" is preferably a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, a propoxy group, or a 2-methoxyethoxy group, more preferably a methoxymethyl group, a methoxyethyl group, or a 2-methoxyethoxy group, but the present invention is not limited thereto.

[0064] In Formula (1) and Formula (1-2), R 4 is preferably a methyl group, an ethyl group, a methoxymethyl group, or a methoxyethyl group.

[0065] Examples of the carboxylic acid anion represented by formula (1-2) include acetate ion, propionate ion, acrylate ion, propargylate ion, butyrate ion, isobutyrate ion, methacrylate ion, crotonate ion, tetrolate ion, cyclopropanecarboxylate ion, valerate ion, isovalerate ion, pivalate ion, angelate ion, tiglate ion, cyclobutanecarboxylate ion, caproate ion, cyclopentanecarboxylate ion, enanthate ion, sorbate ion, cyclohexanecarboxylate ion, benzoate ion, caprylate ion, 2-ethylhexanecarboxylate ion, toluylate ion, 2-norbornanecarboxylate ion, pelargonate ion, cinnamate ion, caprate ion, adamantanecarboxylate ion, geranate ion, undecylate ion, laurate ion, naphthalenecarboxylate ion, etc. Preferred are acetate ion, propionate ion, acrylate ion, propargylate ion, butyrate ion, isobutyrate 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)propionate ion, 3-(2-ethoxyethoxy)propionate ion, 3-(2-propoxyethoxy)propionate ion, 3-(3-methoxypropoxy)propionate ion, 3-(3-ethoxypropoxy)propionate ion, 3-(3-propoxypropoxy)propionate ion, 3-[2-(2-methoxyethoxy)ethoxy]propionate ion, 3-[2-(2-ethoxyethoxy)ethoxy]propionate ion, 4,7,10,13-tetraoxatetradecanoate ion, 4,7,10,13-tetraoxapentadecanoate ion, 4,7,10,13,16-pentaoxaheptadecanoate ion, 4,7,10,13,16 - pentaoxaoctadecanoate ions, (methylthio)acetate ions, (ethylthio)acetate ions, 3-(methylthio)propanoate ions, 3-[(2-methoxyethyl)thio]propanoate ions, 3-[(2-ethoxyethyl)thio]propanoate ions, etc., and particularly preferably acetate ions, methoxyacetate ions, acrylate ions or methacrylate ions, but the present invention is not limited thereto.,

[0066] 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, 1,3-bis(3-methoxypropyl)-2-methylimidazolium, and one anion selected from the group consisting of acetate ions, methoxyacetate ions, acrylate ions, methacrylate ions.,

[0067] As the onium salt represented by the formula (1), more specifically, 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, 1,3-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, 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium methacrylate and the like can be mentioned. Preferably, they are 1,3-bis(3-methoxypropyl)imidazolium acetate, 1,3-bis(3-methoxypropyl)imidazolium acrylate, 1,3-bis(3-methoxypropyl)imidazolium methacrylate. However, the present invention is not limited thereto.

[0068] The polysaccharide in the present invention is a substance in which a large number of monosaccharide molecules are polymerized by a glycosidic bond. Examples of the constituent monosaccharide molecules include glucose, fructose, glucosamine, N-acetylglucosamine and the like. Polysaccharides derived from glucose include glycogen, starch, cellulose, dextrin, curdlan and the like, polysaccharides derived from fructose include fructan and the like, and polysaccharides derived from glucosamine include chitin, chitosan and the like. Particularly, cellulose, curdlan, chitin, chitosan and the like which are hardly soluble are suitable for the present invention.

[0069] Cellulose refers to polymers and their derivatives in which glucose is polymerized by β-1,4-glucoside bonds. The degree of polymerization of glucose in cellulose is not particularly limited, but is preferably 200 or more. Examples of the derivatives include derivatives such as carboxymethylation, aldehyde formation, and esterification. Further, cellulose may contain cellooligosaccharide and cellobiose, which are partial decomposition products thereof. Furthermore, cellulose may be a complex with β-glucoside, lignin and / or hemicellulose which are glycosides, and further may be a complex with pectin or the like. Cellulose may be crystalline cellulose or amorphous cellulose, but is preferably crystalline cellulose. Furthermore, cellulose may be of natural origin or artificially synthesized. The origin of cellulose is not particularly limited. It may be of plant origin, fungal origin, or bacterial origin.

[0070] In addition, the cellulose in the present invention includes materials containing the above cellulose. Specific examples of the materials containing the cellulose include biomass containing pulp, natural fiber products such as cotton and hemp, regenerated fiber products such as rayon, cupra, and acetate, various straws such as rice straw, agricultural waste such as bagasse and wood chips, waste paper, and various wastes such as construction waste. When biomass containing the above pulp, natural fiber products such as cotton and hemp, regenerated fiber products such as rayon, cupra, and acetate, various straws such as rice straw, agricultural waste such as bagasse and wood chips, waste paper, and various wastes such as construction waste is dissolved in the onium salt of the present invention, it is preferable to use those obtained by cutting them in order to shorten the time until dissolution.

[0071] The "esterifying agent" used in step (2) of the production method of the present invention will be described. The "esterifying agent" used in the present invention is an esterifying agent represented by the following formula (2) or the following formula (3). (Formula 2):

Chemical formula

[0072] In formula (2) or formula (3), R 5 is a hydrocarbon group having 1 to 12 carbon atoms, and may contain a hetero atom, a double bond, a branched structure, or a ring structure.

[0073] In formula (2) or formula (3), R 5 In the case of "a hydrocarbon group having 1 to 12 carbon atoms" for R, the number of carbon atoms is preferably 1 to 8, more preferably 1 to 3. The hydrocarbon may be linear, or may contain a branch, a ring structure, or a double bond.

[0074] In formula (2) or formula (3), R 5 Examples of the "hydrocarbon group having 1 to 12 carbon atoms" for R include a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched alkenyl group having 2 to 12 carbon atoms, a linear or branched alkynyl group having 2 to 12 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms which may have a branch, a cycloalkenyl group having 3 to 12 carbon atoms which may have a branch, an aryl group having 6 to 12 carbon atoms which may have a branch, an aralkyl group having 7 to 12 carbon atoms which may have a branch, and the like. Preferably, it is a linear or branched alkyl group having 1 to 12 carbon atoms, a linear or branched alkenyl group having 2 to 12 carbon atoms, or a cycloalkyl group having 3 to 12 carbon atoms which may have a branch.

[0075] In formula (2) or formula (3), R 5 In the case of the "linear or branched alkyl group having 1 to 12 carbon atoms" for R, it is preferably a linear or branched alkyl group having 1 to 8 carbon atoms, more preferably a linear or branched alkyl group having 1 to 4 carbon atoms, and still more preferably a linear or branched alkyl group having 1 to 3 carbon atoms.

[0076] In formula (2) or formula (3), R 5In this case, the "alkenyl group having 2 to 12 carbon atoms which may be linear or branched" is preferably an alkenyl group having 2 to 8 carbon atoms which may be linear or branched, more preferably an alkenyl group having 2 to 4 carbon atoms which may be linear or branched, and even more preferably an alkenyl group having 2 to 3 carbon atoms which may be linear or branched.

[0077] In formula (2) or formula (3), R 5 In this case, the "cycloalkyl group having 3 to 12 carbon atoms which may have a branch" is preferably a cycloalkyl group having 3 to 8 carbon atoms which may have a branch, more preferably a cycloalkyl group having 3 to 4 carbon atoms which may have a branch, and even more preferably a cycloalkyl group having 3 carbon atoms.

[0078] In formula (2) or formula (3), R 5 In this case, examples of the "hydrocarbon group having 1 to 12 carbon atoms" specifically include methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, octyl group, 2-ethylhexyl group, decyl group, dodecyl group, vinyl group, ethynyl group, propenyl group, isopropenyl group, allyl group, propargyl group, butenyl group, crotyl group, butadienyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, norbornyl group, adamantyl group, phenyl group, benzyl group, tolyl group, styryl group, 2,4,6-trimethylphenyl group, etc. Among them, preferably, methyl group, ethyl group, propyl group, isopropyl group, butyl group, sec-butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group are selected, and more preferably, methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group are selected.

[0079] In formula (2) or formula (3), R 5 The case where R is a "hydrocarbon group containing a hetero atom" will be described.

[0080] In formula (2) or formula (3), R 5When it is a "hydrocarbon group containing a heteroatom", the hydrocarbon group may be linear, and may contain a branch, a ring structure, or a double bond.

[0081] In formula (2) or formula (3), R 5 When it is a hydrocarbon group containing a heteroatom, the number of carbon atoms is preferably 2 to 12, more preferably 2 to 8, and still more preferably 2 to 4.

[0082] In formula (2) or formula (3), R 5 When it is a hydrocarbon group containing a heteroatom, the number of heteroatoms is preferably 1 to 5, more preferably 1 to 2. Examples of the "heteroatom" include a nitrogen atom, an oxygen atom, and a sulfur atom.

[0083] In formula (2) or formula (3), R 5 In this case, the "hydrocarbon group containing a heteroatom" is 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 substituted by structures such as -O-, -N<, -NH-, -S-, -C(=O)-O-, -C(=O)-, =N-, -C(=O)-N<, -C(=O)-NH-, -O-C(=O)-O-, -O-C(=O)-N<, -O-C(=O)-NH-, -C(=O)-N[-C(=O)-]-, -C(=O)-NH-C(=O)-, >N-C(=O)-N<, >N-C(=O)-NH-, -HN-C(=O)-NH-, -S(=O)-, -S(=O)2-, -S(=O)2-O-, -O-S(=O)2-O-, >N-C(=S)-N<, >N-C(=S)-NH-, -HN-C(=S)-NH-, -C(=N-)-, -C(=NH)-, etc. The number and combination of substitutions by these structures are not particularly limited.

[0084] Preferably, the bond between two adjacent carbon atoms of the hydrocarbon group (i) and / or the hydrogen atoms of one -CH2- (methylene group) and the hydrogen atoms of another -CH2- (methylene group) are substituted by the structure of -O- or -S-, more preferably substituted by the structure of -O-.

[0085] In formula (2) or formula (3), R 5 In this case, as the structure in which the bond between two adjacent carbon atoms of the hydrocarbon group (i) and / or the hydrogen atoms of one -CH2- (methylene group) and the hydrogen atoms of another -CH2- (methylene group) are substituted by the structure of -O- or -S-, in addition to the structure of -O- (ether structure) and -S- (thioether structure), for example, epoxy structures or thioepoxy structures such as epoxy groups, thioepoxy groups, glycidyl ether groups, epoxycyclohexyl groups may be formed.

[0086] In formula (2) or formula (3), R 5 In this case, when two or more structures of -O- or / and -S- are included, it is desirable that the number of carbon atoms between the structures of -O- or / and -S- is 2 or more.

[0087] In formula (2) or formula (3), R 5 In this case, examples of the "hydrocarbon group containing a heteroatom" include a linear or branched alkyl group containing a heteroatom, a linear or branched alkenyl group containing a heteroatom, a linear or branched alkynyl group containing a heteroatom, a cycloalkyl group that may have a branch containing a heteroatom, a cycloalkenyl group that may have a branch containing a heteroatom, an aryl group that may have a branch containing a heteroatom, an aralkyl group that may have a branch containing a heteroatom, etc. Preferably, it is a linear or branched alkyl group containing a heteroatom, a linear or branched alkenyl group containing a heteroatom, or a cycloalkyl group that may have a branch containing a heteroatom.

[0088] The "alkyl group having a straight chain or a branch and containing a heteroatom" is preferably an alkyl group having a straight chain or a branch, containing 1 to 5 heteroatoms and having 1 to 12 carbon atoms. In another aspect, it is preferably an alkyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 1 to 12 carbon atoms, more preferably an alkyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 1 to 8 carbon atoms, and still more preferably an alkyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 1 to 4 carbon atoms.

[0089] The "alkenyl group having a straight chain or a branch and containing a heteroatom" is preferably an alkenyl group having a straight chain or a branch, containing 1 to 5 heteroatoms and having 2 to 12 carbon atoms. In another aspect, it is preferably an alkenyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 2 to 12 carbon atoms, more preferably an alkenyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 2 to 8 carbon atoms, and still more preferably an alkenyl group having a straight chain or a branch, containing 1 to 2 heteroatoms and having 2 to 4 carbon atoms.

[0090] The "cycloalkyl group which may have a branch and contains a heteroatom" is preferably a cycloalkyl group which may have a branch, contains 1 to 5 heteroatoms and has 3 to 12 carbon atoms. In another aspect, it is preferably a cycloalkyl group which may have a branch, contains 1 to 2 heteroatoms and has 3 to 12 carbon atoms, more preferably a cycloalkyl group which may have a branch, contains 1 to 2 heteroatoms and has 3 to 8 carbon atoms, and still more preferably a cycloalkyl group which may have a branch, contains 1 to 2 heteroatoms and has 3 to 4 carbon atoms.

[0091] In formula (2) or formula (3), R 5 The "hydrocarbon group containing a heteroatom" is preferably a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, a propoxy group or a 2-methoxyethoxy group, more preferably a methoxymethyl group, a methoxyethyl group or a 2-methoxyethoxy group, but the present invention is not limited thereto.

[0092] In formula (2) or formula (3), R 5 is preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a hexyl group, an octyl group, a dodecyl group, a tert-butyl group, a dodecyl group, an allyl group, a phenyl group, or a methoxymethyl group.

[0093] In formula (2) or (3), R 5 is preferably the same as R in formula (1) and formula (1-2). 4

[0094] In formula (3), R 6 is a hydrogen atom or a methyl group.

[0095] More specifically, examples of the esterifying agent represented by formula (2) or formula (3) include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, isovaleric anhydride, pivalic anhydride, hexanoic anhydride, heptanoic anhydride, octanoic anhydride, nonanoic anhydride, decanoic anhydride, lauric anhydride, cyclohexanoic anhydride, benzoic anhydride, 2-methylbenzoic anhydride, allylic anhydride, crotonic anhydride, methacrylic anhydride, methoxyacetic anhydride, phenoxyacetic anhydride, 4-methoxybenzoic anhydride, isopropenyl acetate, vinyl acetate, vinyl propionate, vinyl crotonate, vinyl butyrate, vinyl pivalate, etc. Preferably, acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, isovaleric anhydride, pivalic anhydride, hexanoic anhydride, heptanoic anhydride, octanoic anhydride, benzoic anhydride, allylic anhydride, methoxyacetic anhydride, isopropenyl acetate, vinyl acetate, vinyl propionate, vinyl butyrate are used, and more preferably, acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, isovaleric anhydride, pivalic anhydride, benzoic anhydride, isopropenyl acetate, vinyl acetate, vinyl butyrate are used.

[0096] The "solvent in which the esterified polysaccharide is insoluble" used in step (3) of the production method of the present invention will be described. ​The "solvent in which the esterified polysaccharide is insoluble" used in step (3) is at least one solvent selected from water, alcohol, and ketone. Specific examples of the alcohol include methanol, ethanol, propanol, butanol, etc., and specific examples of the ketone include acetone, methyl ethyl ketone, etc., and these may be used in combination.

[0097] The carboxylic acid represented by the following formula (4) contained in the filtrate separated in step (4) of the production method of the present invention will be described. (Formula 4):

Chemical formula

[0098] In formula (4), R 5 is a hydrocarbon group having 1 to 12 carbon atoms, and may contain a hetero atom, a double bond, a branched structure, or a ring structure. R 5 is the same as R 5 in formula (2) or formula (3).

[0099] Specific examples of the carboxylic acid represented by formula (4) include acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, cyclohexanoic acid, benzoic acid, 2-methylbenzoic acid, allylic acid, crotonic acid, methacrylic acid, methoxyacetic acid, phenoxyacetic acid, 4-methoxybenzoic acid, etc. Preferably, they are acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, hexanoic acid, heptanoic acid, octanoic acid, benzoic acid, allylic acid, methoxyacetic acid, and more preferably acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, benzoic acid.

[0100] The amine represented by the following formula (5) used in step (6) of the production method of the present invention will be described. (Formula 5):

Chemical formula

[0101] In formula (5), 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 may contain a double bond or a branched or cyclic structure. Also, the total number of carbon atoms contained in each of R 7 , R 8 and R 9 is 8 or more. )

[0102] In formula (5), R 7 , R 8 and R 9 in the hydrocarbon group has 1 to 18 carbon atoms, preferably 1 to 12, more preferably 1 to 8 carbon atoms. R 7 , R 8 and R 9 the total number of carbon atoms contained in each of is 8 or more, preferably 12 or more and 24 or less.

[0103] R 7 , R 8 and R 9 as the hydrocarbon group, specifically, 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. may be mentioned. Also, an isopropyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, a neopentyl group, a 2-ethylhexyl group contains a branched structure.

[0104] R 7 , R 8 and R 9 as the hydrocarbon group containing a double bond, specifically, 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, an oleyl group may be mentioned.

[0105] R 7 , R 8 and R9 Among them, 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, a 2,4,6-trimethylphenyl group, and the like. Further, the cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, norbornyl group, and adamantyl group contain a branched structure.

[0106] R 7 、R 8 and R 9 are preferably a hydrogen atom, a methyl group, an oleyl group, a 2-ethylhexyl group, a cyclohexyl group, an octadecyl group, and an octyl group.

[0107] Specific examples of the amine represented by formula (5) include tripropylamine, tributylamine, tripentylamine, trihexylamine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, oleylamine, di-2-ethylhexylamine, dicyclohexylamine, methyloctadecylamine, dimethyloctadecylamine, trioctylamine, and the like.

[0108] Hereinafter, steps (1) to (8) of the production method of the present invention will be described.

[0109] Step (1) is a step of mixing an onium salt represented by formula (1) and a polysaccharide and dissolving the polysaccharide in the onium salt.

[0110] In step (1), the concentration of the polysaccharide contained in the mixture of the onium salt and the polysaccharide is 5 to 40% by weight, preferably 10 to 25% by weight, based on 100% by weight of the total weight of the mixture of the onium salt and the polysaccharide. The temperature at which the polysaccharide is dissolved in the onium salt is 10 to 120°C, preferably 20 to 100°C, and more preferably 25 to 80°C.

[0111] In step (1), dissolution of the polysaccharide can be promoted by subjecting the mixture of the onium salt and the polysaccharide to stirring, shaking, ultrasonic irradiation, or the like.

[0112] Step (2) is a step of adding an esterifying agent represented by formula (2) or formula (3) to the mixture obtained in step (1) to produce an esterified polysaccharide.

[0113] The amount of the esterifying agent added to the mixture obtained in step (1) is 0.1 to 10 equivalents, preferably 1 to 3 equivalents, relative to the glucose unit of the polysaccharide. The temperature at the time of adding the esterifying agent to the mixture obtained in step (1) is -10 to 100°C, preferably 0 to 80°C.

[0114] The reaction between the polysaccharide and the esterifying agent is usually carried out by stirring at -10 to 100°C, preferably 0 to 80°C, for 0.5 to 2 hours.

[0115] The degree of esterification of the esterified polysaccharide to be produced is not particularly limited, but is preferably 1 to 3.

[0116] Step (3) is a step of adding a solvent in which the esterified polysaccharide is insoluble to the mixture obtained in step (2) to precipitate the esterified polysaccharide.

[0117] The amount of the solvent in which the esterified polysaccharide is insoluble used is 1 to 100 times, preferably 5 to 50 times, the total weight of the onium salt used in step (1). The temperature at the time of precipitation is not particularly limited, but is preferably 10 to 50°C.

[0118] Step (4) is a step of filtering the esterified polysaccharide precipitated in step (3) to separate it from the filtrate containing the onium salt represented by formula (1), the carboxylic acid represented by formula (4), and the solvent in which the esterified polysaccharide is insoluble.

[0119] The filtration method in step (4) is not particularly limited, and it may be carried out under normal pressure or reduced pressure conditions or with heating.

[0120] The filtrate separated in step (4) may contain acetone or acetaldehyde which is a decomposition product of the esterifying agent represented by formula (2) or formula (3).

[0121] Step (5) is a step of heating and / or reducing the pressure of the filtrate separated in step (4) to remove the solvent in which the esterified polysaccharide is insoluble from the filtrate.

[0122] The method of removing the solvent in which the esterified polysaccharide is insoluble from the filtrate separated in step (4) by heating and / or reducing the pressure is not particularly limited.

[0123] When removing the solvent in which the esterified polysaccharide is insoluble by heating and / or reducing the pressure, acetone or acetaldehyde which is a decomposition product of the esterifying agent represented by formula (2) or formula (3) may be removed simultaneously.

[0124] Step (6) is a step of adding an amine represented by formula (5) to the mixture containing the onium salt represented by the above formula (1) and the carboxylic acid represented by formula (4) obtained in step (5) to form an amine-carboxylate, and separating it into a layer containing the onium salt and a layer containing the amine-carboxylate.

[0125] The amount of the amine added to the mixture containing the onium salt represented by formula (1) and the carboxylic acid of formula (4) is 1 equivalent or more of the amine with respect to 1 equivalent of the carboxylic acid, usually 1 equivalent to 1.5 equivalents, preferably 1 equivalent to 1.2 equivalents, more preferably 1 equivalent to 1.1 equivalents. An amine-carboxylate composed of the added amine and the carboxylic acid of formula (4) is formed, and a mixture of the onium salt represented by formula (1), the amine-carboxylate, and the remaining amine is obtained.

[0126] As reaction conditions for adding an amine to a mixture containing an onium salt represented by formula (1) and a carboxylic acid of formula (4) to produce an amine-carboxylate, the temperature is 0°C to 100°C, preferably 25°C to 80°C, and the reaction time is preferably 0.5 to 3 hours, more preferably 1 to 2 hours, with stirring after the addition of the amine is completed.

[0127] Step (7) is a step of recovering the layer containing the onium salt separated in step (6) as a recovered liquid containing the onium salt.

[0128] In step (7), the layer containing the onium salt separated in step (6) may be recovered, and examples of the recovery method include liquid separation.

[0129] In step (7), a recovered liquid containing the onium salt represented by formula (1) is obtained. If the obtained recovered liquid contains the amine remaining therein, the remaining amine can be removed by heating and / or reducing the pressure of the obtained recovered liquid.

[0130] Step (8) is a step of introducing the recovered liquid recovered in step (7) into step (1), and is a step of recycling the recovered liquid containing the onium salt represented by formula (1) as the onium salt used in step (1).

[0131] Step (8) is a step of introducing the recovered liquid containing the onium salt obtained in step (7) into step (1), and the method is not particularly limited.

[0132] As a preferred embodiment of the present invention, in step (6), a method for producing an esterified polysaccharide is provided, in which water and / or a hydrophilic solvent is added to the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (4) obtained in step (5).

[0133] A hydrophilic solvent is a solvent that can be dissolved or mixed with water, and specifically includes 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 weight to 90% by weight, preferably 1% by weight to 70% by weight, more preferably 5% by weight to 50% by weight, with the total amount of the mixture containing the onium salt represented by the formula (1), the carboxylic acid of the formula (4), water and / or hydrophilic solvent being 100% by weight.

[0134] As a preferred embodiment of the present invention, in the step (6), to the mixture containing the onium salt represented by the formula (1) and the carboxylic acid represented by the formula (4) obtained in the step (5), (i) an amine represented by the formula (5) is added, or (ii) an amine solution diluted with a hydrophobic solvent is added. The method for producing an esterified polysaccharide according to claim 1 may be mentioned.

[0135] In the above (ii) when an amine solution diluted with a hydrophobic solvent is added, examples of the solvent used include chloroform, dichloromethane, 2-ethylhexanol, cyclohexanol, 1-octanol, ethyl acetate, etc., preferably chloroform, 2-ethylhexanol, cyclohexanol, 1-octanol. The concentration of the amine solution diluted with a hydrophobic solvent is usually 0.01 g / L to 10.0 g / L, preferably 0.1 g / L to 5.00 g / L.

[0136] As a preferred embodiment of the present invention, water and a hydrophobic solvent may be further added to the mixture containing the onium salt represented by the formula (1) and the carboxylic acid represented by the formula (4) obtained in the step (5) and used in the step (6).

[0137] The hydrophobic solvent may be a solvent for diluting the added amine, or may be added alone to the mixture in step (6) without being used for diluting the amine. The hydrophobic solvent added to the mixture obtained in step (5) is preferably a solvent that phase-separates from water. Examples of the hydrophobic solvent that phase-separates from water include hexane, heptane, toluene, chloroform, dichloromethane, 2-ethylhexanol, cyclohexanol, 1-octanol, ethyl acetate, etc., and preferably chloroform, 2-ethylhexanol, cyclohexanol, 1-octanol.

[0138] When the mixture obtained in step (5) used in step (6) contains water and the hydrophobic solvent, the added amine forms an amine-carboxylate salt and is mainly extracted into the hydrophobic solvent layer. On the other hand, since the onium salt represented by formula (1) is present in the aqueous layer, by separating the solvent layer, the amine-carboxylate salt is separated, and an aqueous layer containing the onium salt represented by formula (1) with the amount of the carboxylic acid represented by formula (4) reduced or almost completely removed is obtained. Although it is difficult to remove the carboxylic acid of formula (4) coexisting with the onium salt represented by formula (1) by evaporation, the water in the aqueous 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.

[0139] In the mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (4), the solubility of cellulose is greatly reduced due to the presence of the carboxylic acid represented by formula (4), but the solubility of cellulose can be greatly improved by carrying out step (6) of the production method of the present invention. For example, in a mixture containing the onium salt represented by formula (1) and the carboxylic acid represented by formula (4), 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 (4), the solubility of cellulose can be greatly improved.

[0140] Further, when the amine is added as an amine solution diluted with a solvent and the separation liquid containing the onium salt represented by the formula (1) separated in the step (6) contains a solvent, the solvent can be distilled off by heating and / or reducing the pressure of the obtained separation liquid.

[0141] As one preferred embodiment of the present invention, there is provided a method for producing an esterified polysaccharide, wherein in the step (1), at least two kinds of the onium salts represented by the formula (1) are used.

[0142] Specific examples of the mixture of at least two kinds of the onium salts represented by the formula (1) 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.

[0143] As one preferred embodiment of the present invention, there is provided a method for producing an esterified polysaccharide, wherein in the step (2), at least two kinds of the esterifying agents represented by the formula (2) or the formula (3) are used.

[0144] Specific examples of the mixture of at least two kinds of the esterifying agents represented by the formula (2) or the formula (3) include a mixture of acetic anhydride and propionic anhydride, a mixture of acetic anhydride and butyric anhydride, and a mixture of isopropenyl acetate and vinyl butyrate.

[0145] As one preferred embodiment of the present invention, there is provided a method for producing an esterified polysaccharide, wherein in the step (1), the onium salt represented by the formula (1) is an onium salt solution diluted with an aprotic polar solvent.

[0146] Examples of aprotic polar solvents include, but are not particularly limited to, dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, acetonitrile, pyridine, etc., and may contain two or more organic solvents. Such organic solvents themselves hardly dissolve polysaccharides, but when mixed with the onium salt (1) or the onium salt composition and used, they can contribute to improving the solubility of polysaccharides, accelerating the dissolution rate of polysaccharides due to a decrease in viscosity, improving workability in the polysaccharide recovery process, controlling the physical properties of the recovered polysaccharides, and the like.

[0147] As a preferred embodiment of the present invention, in the step (7), An amine represented by the formula (5) is added to the recovery liquid containing the onium salt to form an amine-carboxylate salt, and it is separated into a layer containing the onium salt and a layer containing the amine-carboxylate salt, and the separated layer containing the onium salt is recovered as a recovery liquid containing the onium salt. A method for producing an esterified polysaccharide can be mentioned.

[0148] The uses of the polysaccharide esterified product obtained by the present invention are not particularly limited. For example, in the fiber field such as fibers, ropes, nets, woven and knitted fabrics, felts, fleeces, wood plastics, carbon fiber composite materials, glass fiber composite materials, cellulose nanofiber composite materials, lignocellulose nanofiber composite materials, and other fiber composite materials; in the film field such as polarizing plate protection films, optical films, etc.; in the plastic field such as medical devices, electronic component materials, packaging materials, spectacle frames, pipes, rods, tools, tableware, toys, etc.; in the civil engineering-related field such as concrete viscosity modifiers, clay mineral viscosity modifiers, etc., it can be used.

Examples

[0149] Next, the present invention will be specifically described based on examples, but the present invention is not limited thereto.

[0150] 1,3-Bis(3-methoxypropyl)imidazolium acetate ([(MeOPr)2Im][AcO]) used in the examples was produced as described in the following [Production Example 1].

[0151] [Production Example 1] Into a 5 L three-necked reactor purged with nitrogen, 260 g of a 37 wt% aqueous formaldehyde solution (manufactured by Tokyo Chemical Industry Co., Ltd.) (3.22 mol in terms of formaldehyde), 290 g of acetic acid (manufactured by Junsei Chemical Co., Ltd.) (4.83 mol), 573 g of 3-methoxypropylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) (6.43 mol), and 461 g of a 40 wt% aqueous glyoxal solution (manufactured by Tokyo Chemical Industry Co., Ltd.) (3.22 mol in terms of glyoxal) were charged. The resulting mixture was heated to 40 °C and stirred for 3 hours to obtain a yellow transparent liquid. The results of the 1H NMR data of the obtained yellow transparent liquid are shown below. 1H NMR (DMSO-d6) δ (ppm) = 9.41 (s, 1H), 7.78 (d, 2H), 4.22 (t, 4H), 3.33 (t, 4H), 3.22 (s, 6H), 2.07 - 2.00 (m, 4H), 1.56 (s, 3H) From the results of this 1H NMR data, it was confirmed that the obtained yellow transparent liquid was 1,3-bis(3-methoxypropyl)imidazolium acetate ([(MeOPr)2Im][AcO]). The obtained 1,3-bis(3-methoxypropyl)imidazolium acetate ([(MeOPr)2Im][AcO]) was 811 g, and the yield was 93%.

[0152] 1-Ethyl-3-methylimidazolium acetate used in Example 2 was purchased from Tokyo Chemical Industry Co., Ltd.

[0153] [Example 1] 1,3-Di(3-methoxypropyl)imidazolium acetate (9.20 g) and cellulose (1.02 g) (Avicel® PH-101) were placed in a vial and stirred at 80 °C for 1 hour. After 1 hour, when the situation was checked, the cellulose had completely dissolved. While cooling this reaction solution in an ice bath, acetic anhydride (6.75 g, 3 equivalents relative to the glucose unit) (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added. After the addition, the mixture was returned to room temperature (25 °C) and stirred for 2 hours. After the reaction, the reaction solution was put into methanol (100 mL) to precipitate a solid. The precipitated solid was filtered, washed, and then dried under vacuum to obtain a white solid. The IR data of the obtained white solid are shown below. The wavelengths of C=O stretching vibration, C-H symmetric bending vibration, and C-O stretching vibration were confirmed by FT-IR (manufactured by JASCO Corporation). IR 1738 cm -1 (C=O stretching vibration), 1365 cm -1 (C-H symmetric bending vibration), 1211 cm -1 (C-O stretching vibration) From the results of this IR data, it was confirmed that the obtained white solid was acetylated cellulose. Also, the hydroxyl groups remaining in the glucose, which is a constituent molecule of the obtained acetylcellulose, were modified with a large excess of benzoyl chloride (manufactured by FUJIFILM Wako Pure Chemical Corporation), and the degree of acetylation was measured by 1H NMR analysis. The measurement results are shown below. Degree of acetylation 2.90 Acetic acid was removed from the filtrate containing 1,3-di(3-methoxypropyl)imidazolium acetate and acetic acid as follows. The filtrate was concentrated to remove methanol. To the concentrated filtrate (2.00 g), ion-exchanged water (6.04 g), 2-ethylhexanol (4.00 g) (manufactured by Junsei Chemical Co., Ltd.), and oleylamine (2.98 g) (manufactured by Sigma) were added and stirred. The filtrate was separated into an aqueous layer containing 1,3-di(3-methoxypropyl)imidazolium acetate and an organic layer containing oleylamine acetate and 2-ethylhexanol. The obtained aqueous layer was concentrated and dried, and then 1H NMR was measured to measure the acetic acid removal rate from the following formula. Acetic acid removal rate (%) = (1 - (integral value of CH3 after removal - 3.00) / (integral value of CH3 before removal - 3.00)) × 100 Acetic acid removal rate (%) = 98.05 Into a vial, 1,3-di(3-methoxypropyl)imidazolium acetate (0.91 g) from which the above acetic acid had been removed and cellulose (0.10 g) were placed, and the mixture was stirred at 80 °C for 1 hour. After 1 hour, when the situation was checked, the cellulose had completely dissolved. While cooling this reaction solution in an ice bath, acetic anhydride (0.68 g, 3 equivalents relative to the glucose unit) (manufactured by Fujifilm Wako Pure Chemical Corporation) was added. After the addition, the mixture was returned to room temperature (25 °C) and stirred for 2 hours. After the reaction, the reaction solution was put into methanol (50 mL) to precipitate a solid. The precipitated solid was filtered, washed, and then dried under vacuum to obtain a white solid. The IR data of the obtained white solid are shown below. The wavelengths of C=O stretching vibration, C-H symmetric bending vibration, and C-O stretching vibration were confirmed by FT-IR (manufactured by JASCO Corporation). IR 1738 cm -1 (C=O stretching vibration), 1365 cm -1 (C-H symmetric bending vibration), 1211 cm -1 (C-O stretching vibration) From the results of this IR data, it was confirmed that the obtained white solid was acetylated cellulose. Also, the hydroxyl groups remaining in glucose, which is a constituent molecule of the obtained acetylcellulose, were modified with a large excess of benzoyl chloride (manufactured by Fujifilm Wako Pure Chemical Corporation), and the degree of acetylation was measured by 1H NMR. The measurement results are shown below. Degree of acetylation 2.92

[0154] [Comparative Example 1] Cellulose (0.10 g) (Avicel® PH-101) was added to the filtrate (0.99 g) before acetic acid removal obtained in Example 1, and the mixture was stirred at 100 °C for 3 hours. After 3 hours, when the situation was checked, the cellulose had not dissolved at all.

[0155] [Example 2] 1-Ethyl-3-methylimidazolium acetate (1.80 g) and cellulose (0.20 g) (Avicel® PH-101) were placed in a vial and stirred at 80 °C for 1 hour. After 1 hour, upon checking the situation, the cellulose had completely dissolved. While cooling this reaction solution in an ice bath, acetic anhydride (1.37 g, 3 equivalents relative to the glucose unit) (manufactured by Fujifilm Wako Pure Chemical Corporation) was added. After the addition, it was returned to room temperature (25 °C) and stirred for 2 hours. After the reaction, the reaction solution was put into methanol (50 mL) to precipitate a solid. The precipitated solid was filtered, washed, and then dried under vacuum to obtain a pale yellow solid. The IR data of the obtained white solid are shown below. The wavelengths of C=O stretching vibration, C-H symmetric bending vibration, and C-O stretching vibration were confirmed by FT-IR (manufactured by JASCO Corporation). IR 1738 cm -1 (C=O stretching vibration), 1365 cm -1 (C-H symmetric bending vibration), 1211 cm -1 (C-O stretching vibration) From the results of this IR data, it was confirmed that the obtained white solid was acetylated cellulose. Also, the hydroxyl groups remaining in glucose, which is a constituent molecule of the obtained acetylcellulose, were modified with a large excess of benzoyl chloride (manufactured by Fujifilm Wako Pure Chemical Corporation), and the degree of acetylation was measured by analyzing with 1H NMR. The measurement results are shown below. Degree of acetylation 2.77 Acetic acid was removed from the filtrate containing 1-ethyl-3-methylimidazolium acetate and acetic acid as follows. The filtrate was concentrated to remove methanol. To the concentrated filtrate (2.82 g), ion-exchanged water (5.43 g), 2-ethylhexanol (3.61 g) (manufactured by Junsei Chemical Co., Ltd.), and di-2-ethylhexylamine (3.81 g) (manufactured by Koei Chemical Co., Ltd.) were added and stirred. It was separated into an aqueous layer containing 1-ethyl-3-methylimidazolium acetate and an organic layer containing di-2-ethylhexylamine-acetate and 2-ethylhexanol. The obtained aqueous layer was concentrated and dried, and 1H NMR was measured to measure the removal rate of acetic acid from the following formula. Acetic acid removal rate (%) = (1 - (integrated value of CH3 after removal - 3.00) / (integrated value of CH3 before removal - 3.00)) × 100 Acetic acid removal rate (%) = 96.17 Put the above-mentioned acetic acid-removed 1-ethyl-3-methylimidazolium acetate (0.91 g) and cellulose (0.11 g) into a vial and stir at 80 °C for 1 hour. After 1 hour, when checked, the cellulose had completely dissolved. While cooling this reaction solution in an ice bath, acetic anhydride (0.67 g, 3 equivalents relative to the glucose unit) was added. After the addition, it was returned to room temperature (25 °C) and stirred for 2 hours. After the reaction, the reaction solution was put into methanol (100 mL) to precipitate a solid. The precipitated solid was filtered, washed, and then dried under vacuum to obtain a white solid. The IR data of the obtained white solid are shown below. The wavelengths of C=O stretching vibration, C-H symmetric bending vibration, and C-O stretching vibration were confirmed by FT-IR (manufactured by JASCO Corporation). IR 1738 cm -1 (C=O stretching vibration), 1365 cm -1 (C-H symmetric bending vibration), 1211 cm -1 (C-O stretching vibration) From the results of this IR data, it was confirmed that the obtained white solid was acetylated cellulose. Also, the hydroxyl groups remaining in the glucose, which is a constituent molecule of the obtained acetylcellulose, were modified with a large excess of benzoyl chloride and analyzed by 1H NMR to measure the degree of acetylation. The measurement results are shown below. Degree of acetylation 2.97

Industrial Applicability

[0156] According to the present invention, it is possible to provide a method for producing an esterified polysaccharide that can substantially eliminate the use of a catalyst for esterifying cellulose and can further remove or reduce carboxylic acids, and the recovery liquid containing the onium salt recovered by the production method can be recycled.

Claims

1. A method for producing an esterified polysaccharide, comprising the following steps (1) to (8). Step (1): A step of mixing an onium salt represented by the formula (1) and a polysaccharide, and dissolving the polysaccharide in the onium salt. (Formula 1): 【Chemical Formula 1】 (wherein R １ , R ２ are the same or different and each represents a hydrocarbon group which may contain a hetero atom. R １ , R ２ may contain a branch, a ring structure or a double bond. R ３ is a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. R ４ represents a hydrocarbon group having 1 to 12 carbon atoms, which may contain a hetero atom, a double bond, a branched structure or a ring structure.) Step (2): A step of adding an esterifying agent represented by the formula (2) or the formula (3) to the mixture obtained in step (1) to produce an esterified polysaccharide. (Formula 2): [Chemical 2] (wherein, R ５ is a hydrocarbon group having 1 to 12 carbon atoms, and may contain a hetero atom, a double bond, a branched structure, or a ring structure.) (Formula 3): [Chemical Formula 3] (In the formula, R ５ is a hydrocarbon group having 1 to 12 carbon atoms, and may contain a hetero atom, a double bond, a branched structure, or a ring structure. R ６ is a hydrogen atom or a methyl group.) Step (3): A step of adding a solvent in which at least one selected from water, alcohol, and ketone is insoluble in the esterified polysaccharide to the mixture obtained in step (2) to precipitate the esterified polysaccharide. Step (4): A step of filtering the esterified polysaccharide precipitated in step (3) and separating it from a filtrate containing the onium salt represented by the formula (1), the carboxylic acid represented by the formula (4), and the solvent in which the esterified polysaccharide is insoluble. (Formula 4): 【Chemical Formula 4】 (wherein, R ５ is a hydrocarbon group having 1 to 12 carbon atoms, and may contain a hetero atom, a double bond, a branched structure, or a ring structure.) Step (5): A step of heating and / or reducing the pressure of the filtrate separated in step (4) to remove the solvent in which the esterified polysaccharide is insoluble from the filtrate. Step (6): To the mixture containing the onium salt represented by the formula (1) and the carboxylic acid represented by the formula (4) obtained in step (5), add an amine represented by the formula (5) to form an amine-carboxylate, and separate it into a layer containing the onium salt and a layer containing the amine-carboxylate. (Formula 5): 【Chemical Formula 5】 (wherein 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 may contain a double bond, a branched structure, or a ring structure. Also, the total number of carbon atoms contained in each of R ７ , R ８ and R ９ is 8 or more.) Step (7): A step of recovering the layer containing the onium salt separated in step (6) as a recovered liquid containing the onium salt. Step (8): A step of introducing the recovered liquid recovered in step (7) into step (1).

2. In the step (6), the obtained in step (5) To the mixture containing the onium salt represented by the formula (1) and the carboxylic acid represented by the formula (4), add water and / or a hydrophilic solvent. The method for producing an esterified polysaccharide according to claim 1.

3. In the step (6), the obtained in step (5) To the mixture containing the onium salt represented by the formula (1) and the carboxylic acid represented by the formula (4), (i) add an amine represented by the formula (5), or (ii) add an amine solution in which the amine is diluted with a hydrophobic solvent. The method for producing an esterified polysaccharide according to claim 1.

4. In step (1), the onium salt represented by the formula (1) is at least two types. The method for producing an esterified polysaccharide according to claim 1.

5. The method for producing an esterified polysaccharide according to claim 1, wherein in step (2), at least two types of esterifying agents represented by the formula (2) or the formula (3) are used.

6. The method for producing an esterified polysaccharide according to claim 1, wherein in step (1), the onium salt represented by the formula (1) is an onium salt solution diluted with an aprotic polar solvent.

7. In step (7), to the recovery liquid containing the onium salt, the amine represented by the formula (5) is added to form an amine-carboxylate salt, and the mixture is separated into a layer containing the onium salt and a layer containing the amine-carboxylate salt, and the separated layer containing the onium salt is recovered as a recovery liquid containing the onium salt. The method for producing an esterified polysaccharide according to claim 1.

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