Method for producing esterified polysaccharide

Abstract

To provide a method for producing an esterified polysaccharide substantially without using a catalyst by increasing the solubility of cellulose in ionic liquids compared to conventional methods.SOLUTION: There is provided a method for producing an esterified polysaccharide comprises the following steps (1), (2), (3) and (4): step (1): dissolving a polysaccharide in an onium salt represented by formula (1), the formula (1): step (2): adding an esterifying agent, step (3): adding at least one selected from water, alcohol, and ketone to precipitate esterified polysaccharides, and step (4): filtering the esterified polysaccharide.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 film, fiber, pharmaceutical applications, etc. Also, cellulose derivatives are used in a wide range of commercial applications. Generally, cellulose is a polymer with β-1,4-linkages of anhydroglucose, having glucose as a constituent unit. Also, a cellulose derivative is a compound in which at least a part of the three hydroxyl groups present in glucose, which is a constituent unit of cellulose, is derivatized into another functional group. Also, esterified products of cellulose obtained by esterifying cellulose and esterified products of cellulose derivatives obtained by esterifying the 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 with an acylating reagent in the presence of a catalyst to prepare a solution containing a cellulose ester, the solution is contacted with a non-solvent to precipitate the cellulose ester, and the precipitated cellulose ester is separated from the carboxylated ionic liquid to recover the cellulose ester.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The method for producing a cellulose ester described in Patent Document 1 specifically uses 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, or 1-allyl-3-methylimidazolium chloride as a carboxylated ionic liquid. Further, in order to increase the rate of esterification, a production method using methanesulfonic acid, which is a protonic acid, as a catalyst is used specifically. Since the solubility of cellulose in 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, or 1-allyl-3-methylimidazolium chloride used in the production method is low, a catalyst is used to increase the rate of esterification. The catalyst may remain in the esterified cellulose, and if it remains, there is a concern that it will affect the quality of the esterified cellulose that becomes the product. Therefore, the low solubility of cellulose in the ionic liquid and the need for a catalyst have become problems.

[0007] In the situation of the prior art 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 can increase the solubility of cellulose in an ionic liquid more than before and substantially does not use a catalyst.

Means for Solving the Problems

[0008] The present inventors have intensively studied a method for producing an esterified polysaccharide using an onium salt represented by the following (Formula 1) and have completed the present invention.

[0009] That is, the present invention provides the following [1] to [4]. [1] A method for producing an esterified polysaccharide, comprising the following steps (1), (2), (3) and (4). Step (1): A step of mixing a polysaccharide with an onium salt represented by formula (1) and dissolving the polysaccharide in the onium salt. (Formula 1) [Chemical formula] (In the formula, R 1 and R 2 are the same or different and each represents a hydrocarbon group having 2 to 12 carbon atoms containing 1 to 5 heteroatoms, or a group represented by the following formula (1a). -O-R a (1a) (R a represents a hydrocarbon group having 1 to 12 carbon atoms which may contain 1 to 4 heteroatoms.) R 3 represents a hydrogen atom or a hydrocarbon group which may contain a heteroatom. The heteroatom is at least one selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom. R 4 represents a hydrocarbon group. However, when R 1 and R 2 are methoxyethyl groups and R 3 is a hydrogen atom, R 4 represents a hydrocarbon group having 2 or more carbon atoms.) Step (2): A step of adding an esterifying agent to the mixture obtained in step (1) to produce an esterified polysaccharide. Step (3): A step of adding at least one solvent selected from water, alcohol and ketone to the mixture obtained in step (2) to precipitate the esterified polysaccharide. Step (4): A step of filtering the esterified polysaccharide from the mixture obtained in step (3) to obtain the esterified polysaccharide. [2] The method for producing an esterified polysaccharide according to [1], wherein at least two types of onium salts represented by formula (1) are used in step (1). [3] The method for producing an esterified polysaccharide according to [1], wherein at least two types of esterifying agents are used in the step (2). [4] The method for producing an esterified polysaccharide according to [1], wherein in the step (1), a polysaccharide is mixed with a mixed solution of an onium salt represented by the formula (1) and an aprotic polar solvent.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a method for producing an esterified polysaccharide, preferably a method for producing an esterified cellulose, which can increase the solubility of cellulose in an ionic liquid to a higher level than before and substantially does not use a catalyst.

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), (2), (3) and (4). Step (1): A step of mixing a polysaccharide with an onium salt represented by the formula (1) and dissolving the polysaccharide in the onium salt. Formula (1):

Chemical Formula

[0012] The onium salt represented by the following formula (1) 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.

Chemical formula

[0015] In formula (1) and formula (1-1), R 1 and R 2 are the same or different and represent a hydrocarbon group having 2 to 12 carbon atoms containing 1 to 5 heteroatoms, or a group represented by the following formula (1a). -O-Ra (1a) (Ra represents a hydrocarbon group having 1 to 12 carbon atoms which may contain 1 to 4 heteroatoms.)

[0016] In formula (1) and formula (1-1), R 1 and R 2 When they are "hydrocarbon groups having 2 to 12 carbon atoms containing 1 to 5 heteroatoms", it will be described.

[0017] In formula (1) and formula (1-1), R 1 and R 2 The "hydrocarbon group having 2 to 12 carbon atoms containing 1 to 5 heteroatoms" may be linear, and may contain a branch, a ring structure, a double bond, or a triple bond. The number of heteroatoms is preferably 1 to 3, more preferably 1 to 2. The number of carbon atoms of the hydrocarbon group is preferably 3 to 10, more preferably 4 to 7.

[0018] In formula (1) and formula (1-1), R 1 and R 2 Examples of the "heteroatom" include a nitrogen atom, an oxygen atom, and a sulfur atom.

[0019] In formula (1) and formula (1-1), R 1 and R 2In this context, the "hydrocarbon group having 2 to 12 carbon atoms and containing 1 to 5 heteroatoms" is a hydrocarbon group without heteroatoms where the bond between (i) 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 within the range where the heteroatoms in R 1 , R 2 are 1 to 5, and it is not particularly limited as long as it is within this range.

[0020] The "hydrocarbon group without heteroatoms" in which the bond of (i) and / or the hydrogen atom of (ii) is substituted by the structure containing the heteroatoms to form a "hydrocarbon group having 2 to 12 carbon atoms and containing 1 to 5 heteroatoms" is a "hydrocarbon group having 2 to 12 carbon atoms and without heteroatoms", which may be linear, may contain branches, ring structures, double bonds, or triple bonds. Examples of the hydrocarbon group having 2 to 12 carbon atoms and without heteroatoms include, but are not particularly limited to, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, cycloalkenyl groups, aryl groups, aralkyl groups, etc.

[0021] As the "hydrocarbon group containing no heteroatom" which becomes the "hydrocarbon group having 2 to 12 carbon atoms and containing 1 to 5 heteroatoms" described above, specifically, 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 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 2,4,6-trimethylphenyl group, etc. can be mentioned, but it is not particularly limited.

[0022] In Formula (1) and Formula (1-1), R 1 and R 2 in, as the "hydrocarbon group having 2 to 12 carbon atoms and containing 1 to 5 heteroatoms", preferably, the bond between two adjacent carbon atoms of the hydrocarbon group (i), and / or (ii) 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-, and more preferably, those substituted by the structure of -O-.

[0023] R 1 and R 2 in, as the structure in which the bond between two adjacent carbon atoms of the "hydrocarbon group having 2 to 12 carbon atoms and containing 1 to 5 heteroatoms" (i), and / or (ii) 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 structure of -O- (ether structure) or -S- (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, etc. may be formed. In this case, R 1 or R 2 may be an epoxy group, a thioepoxy group, etc.

[0024] R 1 and R2 When two or more -O- or / and -S- structures are included, the number of carbon atoms between the -O- or / and -S- structures is desirably 2 or more.

[0025] R 1 and R 2 The number of carbon atoms between the nitrogen atom on the imidazole ring to which each of them is bonded and the heteroatom closest to the nitrogen atom on the imidazole ring in R 1 or R 2 is more desirably 2 or more.

[0026] In formula (1) and formula (1-1), R 1 and R 2 The "hydrocarbon group having 1 to 5 heteroatoms and 2 to 12 carbon atoms" includes, for example, an alkyl group having a straight chain or a branch and having 1 to 5 heteroatoms and 2 to 12 carbon atoms, an alkenyl group having a straight chain or a branch and having 1 to 5 heteroatoms and 2 to 12 carbon atoms, an alkynyl group having a straight chain or a branch and having 1 to 5 heteroatoms and 2 to 12 carbon atoms, a cycloalkyl group which may have a branch and has 1 to 5 heteroatoms and 3 to 12 carbon atoms, a cycloalkenyl group which may have a branch and has 1 to 5 heteroatoms and 3 to 12 carbon atoms, an aryl group which may have a branch and has 1 to 5 heteroatoms and 6 to 12 carbon atoms, an aralkyl group which may have a branch and has 1 to 5 heteroatoms and 7 to 12 carbon atoms, and the like.

[0027] Preferably, it is an alkyl group having a straight chain or a branch and having 1 to 5 heteroatoms and 2 to 12 carbon atoms, an alkenyl group having a straight chain or a branch and having 1 to 5 heteroatoms and 2 to 12 carbon atoms, or a cycloalkyl group which may have a branch and has 1 to 5 heteroatoms and 3 to 12 carbon atoms.

[0028] The "alkyl group having 1 to 5 heteroatoms and having a straight-chain or branched structure with 2 to 12 carbon atoms" is preferably an alkyl group having 1 to 3 heteroatoms and having a straight-chain or branched structure with 3 to 10 carbon atoms. In another aspect, it is preferably an alkyl group having 1 to 2 heteroatoms and having a straight-chain or branched structure with 3 to 10 carbon atoms, more preferably an alkyl group having 1 to 2 heteroatoms and having a straight-chain or branched structure with 4 to 7 carbon atoms.

[0029] The "alkenyl group having 1 to 5 heteroatoms and having a straight-chain or branched structure with 2 to 12 carbon atoms" is preferably an alkenyl group having 1 to 3 heteroatoms and having a straight-chain or branched structure with 3 to 10 carbon atoms. In another aspect, it is preferably an alkenyl group having 1 to 2 heteroatoms and having a straight-chain or branched structure with 3 to 10 carbon atoms, more preferably an alkenyl group having 1 to 2 heteroatoms and having a straight-chain or branched structure with 4 to 7 carbon atoms.

[0030] The "cycloalkyl group having 1 to 5 heteroatoms and optionally having a branched structure with 3 to 12 carbon atoms" is preferably a cycloalkyl group having 1 to 3 heteroatoms and optionally having a branched structure with 3 to 10 carbon atoms. In another aspect, it is preferably a cycloalkyl group having 1 to 2 heteroatoms and optionally having a branched structure with 3 to 10 carbon atoms, more preferably a cycloalkyl group having 1 to 2 heteroatoms and optionally having a branched structure with 4 to 7 carbon atoms.

[0031] R represented by formula (1) and formula (1-1) 1 and R 2Specifically, as such, 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 and the like. Preferably, they are 2-methoxyethyl, 3-methoxypropyl, 3-ethoxypropyl, 3-isopropoxypropyl, 3-butoxypropyl, 3-(2-methoxyethoxy)propyl, 3-methylthiopropyl, 3-(dimethylamino)propyl. More preferably, they are 2-methoxyethyl, 3-methoxypropyl, 3-(2-methoxyethoxy)propyl. However, the present invention is not limited thereto.,

[0032] In Formula (1) and Formula (1-1), R 1 and R 2 are preferably the same.

[0033] In Formula (1) and Formula (1-1), R 1 and / or R 2 is the group represented by the following Formula (1a): -O-R a (1a) (R a represents a hydrocarbon group having 1 to 4 heteroatoms and 1 to 12 carbon atoms.) The case where it is a group represented by will be described.

[0034] In Formula (1a), the case where R a is "a hydrocarbon group not containing a heteroatom" will be described. R a When is "a hydrocarbon group not containing a heteroatom", R a is "a hydrocarbon group having 1 to 12 carbon atoms and not containing a heteroatom", and the number of carbon atoms of the hydrocarbon group is preferably 1 to 6, more preferably 1 to 3.

[0035] In Formula (1a), in R a the "hydrocarbon group having 1 to 12 carbon atoms and not containing a heteroatom" may be linear, or may contain a branch, a ring structure, a double bond, or a triple bond. Examples of the "hydrocarbon group having 1 to 12 carbon atoms and not containing a heteroatom" include, but are not particularly limited to, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, and an aralkyl group. Preferably, it is an alkyl group, an alkenyl group, or a cycloalkyl group.

[0036] Preferably, the alkyl group is a linear or branched alkyl group having 1 to 12 carbon atoms, more preferably a linear or branched alkyl group having 1 to 6 carbon atoms, and still more preferably a linear or branched alkyl group having 1 to 3 carbon atoms.

[0037] As the alkenyl group, preferably an alkenyl group having a linear or branched chain with 2 to 12 carbon atoms, more preferably an alkenyl group having a linear or branched chain with 2 to 8 carbon atoms, and even more preferably an alkenyl group having a linear or branched chain with 2 to 3 carbon atoms.

[0038] As the cycloalkyl group, preferably a cycloalkyl group which may have a branch with 3 to 12 carbon atoms, more preferably a cycloalkyl group which may have a branch with 3 to 8 carbon atoms, and even more preferably a cycloalkyl group with 3 carbon atoms.

[0039] In formula (1a), R a In the case of "a hydrocarbon group having 1 to 12 carbon atoms and not containing a heteroatom", specifically, 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, 2,4,6-trimethylphenyl group, etc. can be mentioned, but it is not particularly limited.

[0040] In formula (1a), R a The case where R is "a hydrocarbon group containing a heteroatom" will be described. R a When R is "a hydrocarbon group containing a heteroatom", R a is "a hydrocarbon group having 2 to 12 carbon atoms and containing 1 to 4 heteroatoms". The number of heteroatoms is preferably 1 to 2, and the number of carbon atoms of the hydrocarbon group is preferably 2 to 6. R a In the case of "a hydrocarbon group having 2 to 12 carbon atoms and containing 1 to 4 heteroatoms", it may be linear, or may contain a branch, a ring structure, a double bond or a triple bond.

[0041] In formula (1a), R aIn the case of the "hydrocarbon group having 2 to 12 carbon atoms containing 1 to 4 heteroatoms", examples of the "heteroatom" include a nitrogen atom, an oxygen atom, a sulfur atom, etc.

[0042] In formula (1a), R a In the case of the "hydrocarbon group having 2 to 12 carbon atoms containing 1 to 4 heteroatoms", the (i) bond between two adjacent carbon atoms of the hydrocarbon group not containing a heteroatom, 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-, >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 as long as the number of heteroatoms in R a is in the range of 1 to 4.

[0043] Preferably, the (i) 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 structure of -O- or -S-, and more preferably substituted by a structure of -O-.

[0044] In formula (1a), R aIn this case, as for 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 the structure of -O- or -S-, in addition to the structure of -O- (ether structure) or the structure of -S- (thioether), for example, epoxy structures or thioepoxy structures such as epoxy groups, thioepoxy groups, glycidyl ether groups, epoxycyclohexyl groups may be formed. In this case, R a may be an epoxy group, a thioepoxy group or the like.

[0045] In formula (1a), R a When containing two or more structures of -O- or / and -S-, it is desirable that the number of carbon atoms between the structures of -O- or / and -S- is 2 or more. The number of carbon atoms between the oxygen atom to which R a is bonded and the heteroatom in Ra closest to the oxygen atom is more desirably 2 or more.

[0046] In formula (1a), R a The "hydrocarbon group having 2 to 12 carbon atoms containing 1 to 4 heteroatoms" includes an alkyl group having a straight chain or a branch and having 2 to 12 carbon atoms and containing 1 to 4 heteroatoms, an alkenyl group having a straight chain or a branch and having 2 to 12 carbon atoms and containing 1 to 4 heteroatoms, an alkynyl group having a straight chain or a branch and having 2 to 12 carbon atoms and containing 1 to 4 heteroatoms, a cycloalkyl group which may have a branch and has 3 to 12 carbon atoms and contains 1 to 4 heteroatoms, a cycloalkenyl group which may have a branch and has 3 to 12 carbon atoms and contains 1 to 4 heteroatoms, an aryl group which may have a branch and has 6 to 12 carbon atoms and contains 1 to 4 heteroatoms, an aralkyl group which may have a branch and has 7 to 12 carbon atoms and contains 1 to 4 heteroatoms, and the like. Preferably, it is an alkyl group having a straight chain or a branch and having 2 to 12 carbon atoms and containing 1 to 4 heteroatoms, an alkenyl group having a straight chain or a branch and having 2 to 12 carbon atoms and containing 1 to 4 heteroatoms, or a cycloalkyl group which may have a branch and has 3 to 12 carbon atoms.

[0047] As the "alkyl group having a straight or branched chain with 2 to 12 carbon atoms and containing 1 to 4 heteroatoms", it is preferably an alkyl group having a straight or branched chain with 2 to 6 carbon atoms and containing 1 to 4 heteroatoms. In another preferred embodiment, it is an alkyl group having a straight or branched chain with 2 to 12 carbon atoms and containing 1 to 2 heteroatoms, more preferably an alkyl group having a straight or branched chain with 2 to 6 carbon atoms and containing 1 to 2 heteroatoms.

[0048] As the "alkenyl group having a straight or branched chain with 2 to 12 carbon atoms and optionally containing 1 to 4 heteroatoms", it is preferably an alkenyl group having a straight or branched chain with 2 to 6 carbon atoms and optionally containing 1 to 4 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 6 carbon atoms and containing 1 to 2 heteroatoms.

[0049] As the "cycloalkyl group having 3 to 12 carbon atoms and optionally having a branch and containing 1 to 4 heteroatoms" it is preferably a cycloalkyl group having 3 to 6 carbon atoms, optionally having a branch and containing 1 to 4 heteroatoms. In another preferred embodiment, it is a cycloalkyl group having 3 to 12 carbon atoms, optionally having a branch and containing 1 to 2 heteroatoms, more preferably a cycloalkyl group having 3 to 6 carbon atoms, optionally having a branch and containing 1 to 2 heteroatoms.

[0050] In Formula (1) and Formula (1-1), R 3 represents a hydrogen atom or a "hydrocarbon group which may contain a heteroatom". R 3 The case where is a "hydrocarbon group not containing a heteroatom" will be described. R 3In the case of a "hydrocarbon group containing no heteroatom", the number of carbon atoms in the hydrocarbon group is preferably from 1 to 12, more preferably from 1 to 8, and still more preferably from 1 to 3. The "hydrocarbon group containing no heteroatom" may be linear, or may contain a branch, a ring structure, a double bond or a triple bond.

[0051] Examples of the "hydrocarbon group containing no heteroatom and having 1 to 12 carbon atoms" include, but are not particularly limited to, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, etc. Preferably, they are an alkyl group, an alkenyl group, or a cycloalkyl group.

[0052] The alkyl group is preferably an alkyl group having a straight chain or a branch with 1 to 12 carbon atoms, more preferably an alkyl group having a straight chain or a branch with 1 to 6 carbon atoms, and still more preferably an alkyl group having a straight chain or a branch with 1 to 3 carbon atoms.

[0053] The alkenyl group is preferably an alkenyl group having a straight chain or a branch with 2 to 12 carbon atoms, more preferably an alkenyl group having a straight chain or a branch with 2 to 8 carbon atoms, and still more preferably an alkenyl group having a straight chain or a branch with 2 to 3 carbon atoms.

[0054] The cycloalkyl group is preferably a cycloalkyl group which may have a branch with 3 to 12 carbon atoms, more preferably a cycloalkyl group which may have a branch with 3 to 8 carbon atoms, and still more preferably a cycloalkyl group with 3 carbon atoms.

[0055] In formula (1) and formula (1-1), R 3In 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.

[0056] In formula (1) and formula (1-1), R 3 The case where is a "hydrocarbon group containing a hetero atom" will be described below. The "hydrocarbon group containing a heteroatom" may be linear or may contain a branched or cyclic structure, a double bond, or a triple bond. The heteroatom is at least one selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom. The number of heteroatoms is preferably 1 to 5, and more preferably 1 to 2. R 3 When is a "hydrocarbon group containing a hetero atom", the hydrocarbon group preferably has 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 2 to 4 carbon atoms.

[0057] In formula (1) and formula (1-1), R 3In this context, 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 in R 3 it is preferable that the number of heteroatoms in it is 1 to 5, and more preferably 1 to 2.

[0058] 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 a -O- structure.

[0059] In formula (1) and formula (1 - 1), R 3 In this context, as the structure where (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) or -S- structure (thioether structure), for example, an epoxy structure or thioepoxy structure such as an epoxy group, thioepoxy group, glycidyl ether group, epoxycyclohexyl group, etc. may be formed. In this case, R 3 may be an epoxy group, thioepoxy group, etc.

[0060] R 3 In the case where it contains 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.

[0061] In formulas (1) and (1-1), R 3 The "hydrocarbon group containing a heteroatom" includes an alkyl group having a straight chain or a branch containing a heteroatom, an alkenyl group having a straight chain or a branch containing a heteroatom, an alkynyl group having a straight chain or a 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 a branch containing a heteroatom, an alkenyl group having a straight chain or a branch containing a heteroatom, or a cycloalkyl group which may have a branch containing a heteroatom.

[0062] The "alkyl group having a straight chain or a branch containing a heteroatom" is preferably an alkyl group having a straight chain or a branch and containing 1 to 5 heteroatoms and having 1 to 12 carbon atoms. In another aspect, preferably, it is an alkyl group having a straight chain or a branch and containing 1 to 2 heteroatoms and having 1 to 12 carbon atoms, more preferably an alkyl group having a straight chain or a branch and 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 and containing 1 to 2 heteroatoms and having 1 to 4 carbon atoms.

[0063] The "alkenyl group having a straight chain or a branch containing a heteroatom" is preferably an alkenyl group having a straight chain or a branch and containing 1 to 5 heteroatoms and having 2 to 12 carbon atoms. Preferably, as another embodiment, it is an alkenyl group having 2 to 12 carbon atoms and having 1 to 2 heteroatoms, more preferably an alkenyl group having 2 to 8 carbon atoms and having 1 to 2 heteroatoms, and still more preferably an alkenyl group having 2 to 4 carbon atoms and having 1 to 2 heteroatoms and having a straight chain or a branch.

[0064] As the "cycloalkyl group which may have a branch containing a heteroatom", preferably, it is a cycloalkyl group which may have a branch containing 1 to 5 heteroatoms and having 3 to 12 carbon atoms. Preferably, as another embodiment, it is a cycloalkyl group which may have a branch containing 1 to 2 heteroatoms and having 3 to 12 carbon atoms, more preferably a cycloalkyl group which may have a branch containing 1 to 2 heteroatoms and having 3 to 8 carbon atoms, and still more preferably a cycloalkyl group which may have a branch containing 1 to 2 heteroatoms and having 3 to 4 carbon atoms.

[0065] In formula (1) and formula (1-1), R 3 In this case, as the "hydrocarbon group containing a heteroatom", preferably, it is 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, a benzyloxymethyl group, more preferably a 1-methyl-2-methoxyvinyl group, a 2-furyl group, but the present invention is not limited thereto.

[0066] In formula (1) and formula (1-1), R 3 is preferably a hydrogen atom or a methyl group, and more preferably a hydrogen atom.

[0067] In formula (1) and formula (1-1), some or all of R 1 ~R 3 may combine with the nitrogen atom or carbon atom to which they are attached to form a ring structure. Specifically, R 1 and R 2 , R 1 and R 3or R 2 and R 3 Examples thereof include, but are not particularly limited to, a structure in which they are bonded and crosslinked by a hydrocarbon having 2 to 24 carbon atoms containing 2 to 10 heteroatoms. The ring structure is included in the crosslinked structure.

[0068] The following formula (1-1):

Chemical formula

[0069] The carboxylic acid anion represented by the following formula (1-2) will be described. Formula (1-2):

Chemical formula

[0070] In Formula (1) and Formula (1-2), R 4 represents a hydrocarbon group, which may be linear, and may contain a branch, a ring structure, a double bond, or a triple bond. Preferably, it is a hydrocarbon group having 1 to 12 carbon atoms, more preferably a hydrocarbon group having 1 to 8 carbon atoms, and even more preferably a hydrocarbon group having 1 to 3 carbon atoms.

[0071] In Formula (1) and Formula (1-2), R 4 Examples of the "hydrocarbon group" of R include an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group, etc. Preferably, it is an alkyl group having 1 to 12 carbon atoms and having a linear or branched structure, an alkenyl group having 2 to 12 carbon atoms and having a linear or branched structure, an alkynyl group having 2 to 12 carbon atoms and having a linear or branched structure, a cycloalkyl group having 3 to 12 carbon atoms and optionally having a branch, a cycloalkenyl group having 3 to 12 carbon atoms and optionally having a branch, an aryl group having 6 to 12 carbon atoms and optionally having a branch, an aralkyl group having 7 to 12 carbon atoms and optionally having a branch. More preferably, it is an alkyl group having 1 to 3 carbon atoms and having a linear or branched structure, an alkenyl group having 2 to 3 carbon atoms and having a linear or branched structure.

[0072] In Formula (1) and Formula (1-2), R 4Examples of the "hydrocarbon group" 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, heptyl group, octyl group, 2-ethylhexyl group, nonyl group, decyl group, undecyl group, dodecyl group, vinyl group, ethynyl group, propenyl group, isopropenyl group, allyl group, propargyl group, 1-propynyl group, butenyl group, crotyl group, butadienyl group, pentadienyl 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, naphthyl group, 2,6-dimethyl-1,5-heptadienyl group, etc., but are not particularly limited.

[0073] In Formula (1) and Formula (1-2), the following Formula (1-2) Formula (1-2): [Chemical formula] Examples of the anion represented by 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, and particularly preferred are acetate ion, acrylate ion or methacrylate ion. However, the present invention is not limited thereto.

[0074] The following formula (1):

Chemical formula

[0075] 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.

[0076] However, in the case of the onium salt represented by the formula (1) used in the present invention, when the imidazolium cation represented by the formula (1-1) has R 1 and R 2 being a methoxyethyl group and R 3 being a hydrogen atom, the carboxylic acid anion represented by the formula (1-2) has R 4 being a carboxylic acid anion of a hydrocarbon group having 2 or more carbon atoms.

[0077] The polysaccharides in the present invention are substances in which a large number of monosaccharide molecules are polymerized by glycosidic bonds. Examples of the constituent monosaccharide molecules include glucose, fructose, glucosamine, N-acetylglucosamine, etc. Polysaccharides derived from glucose include glycogen, starch, cellulose, dextrin, curdlan, etc., polysaccharides derived from fructose include fructan, etc., and polysaccharides derived from glucosamine include chitin, chitosan, etc. Particularly preferred for the present invention are cellulose, curdlan, chitin, chitosan, etc., which are particularly poorly soluble.

[0078] Cellulose refers to a polymer in which glucose is polymerized by β-1,4-glycosidic bonds and its derivatives. 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, i.e., lignocellulose, and may further be a complex with pectin, etc. Cellulose may be crystalline cellulose or amorphous cellulose, but preferably crystalline cellulose. Furthermore, cellulose may be of natural origin or artificially synthesized. The origin of cellulose is not particularly limited either. It may be of plant origin, fungal origin, or bacterial origin.

[0079] In addition, the cellulose in the present invention includes materials containing the 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 dissolving the biomass containing the above-mentioned 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 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.

[0080] The esterifying agent in the present invention is not particularly limited, and an esterifying agent corresponding to the type of the esterified polysaccharide to be produced can be appropriately selected and used. Among them, from the viewpoint of reactivity, the esterifying agent used in the present invention is preferably at least one selected from the group consisting of a chain ester compound, a cyclic ester compound, an unsaturated aldehyde, a saturated aldehyde, an acid halide, an acid anhydride, and allyl alcohol.

[0081] As the esterifying agent used in the present invention, specifically, acetic anhydride, propionic anhydride, butyric anhydride, valeric anhydride, caproic anhydride, enanthic anhydride, caprylic anhydride, pelargonic anhydride, capric anhydride, lauric anhydride, myristic anhydride, palmitic anhydride, stearic anhydride, oleic anhydride, linoleic anhydride, linolenic anhydride, benzoic anhydride, phthalic anhydride, maleic anhydride, succinic anhydride, acetyl fluoride, acetyl chloride, acetyl bromide, acetyl iodide, propionyl fluoride, propionyl chloride, propionyl bromide, propionyl iodide, butyryl fluoride, butyryl chloride, butyryl bromide, butyryl iodide, benzoyl fluoride, benzoyl chloride, benzoyl bromide, benzoyl iodide, β-propiolactone, δ-valerolactone, ε-caprolactone, vinyl butyrate, isopropenyl acetate, etc. may be mentioned. Preferably, acetic anhydride, propionic anhydride, butyric anhydride, acetyl chloride, propionyl chloride, benzoyl chloride, vinyl butyrate, isopropenyl acetate may be mentioned. More preferably, acetic anhydride, propionic anhydride, lauric anhydride, acetyl chloride, benzoyl chloride, vinyl butyrate, isopropenyl acetate are used.

[0082] The degree of esterification of the esterified polysaccharide produced by the present invention is not particularly limited, but is preferably 1 to 3.

[0083] Hereinafter, steps (1) to (4) of the production method of the present invention will be described.

[0084] Step (1) is a step of mixing a polysaccharide with an onium salt represented by formula (1) and dissolving the polysaccharide in the onium salt. In step (1), the amount of the polysaccharide dissolved in the onium salt is 5 to 40 parts by mass, preferably 10 to 25 parts by mass, with respect to 100 parts by mass of the mass of the onium salt. The temperature of the mixture of the onium salt and the polysaccharide at the time of dissolution is 10 to 120 ° C, preferably 20 to 100 ° C, and more preferably 25 to 80 ° C.

[0085] Also, in step (1), by subjecting the mixture of the onium salt and the polysaccharide to stirring, shaking, ultrasonic irradiation, etc., the dissolution of the polysaccharide in the ghost onium salt can be promoted.

[0086] Step (2) is a step of adding an esterifying agent to the mixture obtained in step (1) to produce an esterified polysaccharide. In step (2), 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, and the temperature when adding the esterifying agent to the mixture obtained in step (1) is -10 to 100°C, preferably 0 to 80°C.

[0087] In step (2), an esterified polysaccharide can be produced by reacting the polysaccharide contained in the mixture obtained in step (1) with the esterifying agent. 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.

[0088] Step (3) is a step of adding at least one solvent selected from water, alcohol, and ketone to the mixture obtained in step (2) to precipitate the esterified polysaccharide. To precipitate the esterified polysaccharide produced in step (2), a solvent in which the esterified polysaccharide is insoluble may be added. As the solvent in which the esterified polysaccharide is insoluble, at least one solvent selected from water, alcohol, and ketone may be used. In step (3), water, alcohol, or ketone can be used as the solvent for precipitating the esterified polysaccharide. Specifically, water, methanol, ethanol, propanol, butanol, acetone, methyl ethyl ketone, etc. can be mentioned, and these can be used in combination.

[0089] The amount of the solvent in which the esterified polysaccharide is insoluble and which is used in step (3) is 1 to 100 times, preferably 5 to 50 times the weight of the onium salt. The temperature at which the esterified polysaccharide is precipitated from the mixture containing the esterified polysaccharide is not particularly limited, but is preferably 10 to 50 °C.

[0090] Step (4) is a step of filtering the esterified polysaccharide from the mixture obtained in step (3) to obtain the esterified polysaccharide. The filtration method and filtration conditions in step (4) are not particularly limited, and may be carried out under normal pressure or reduced pressure conditions or with heating.

[0091] The onium salt represented by the formula (1) used in the production method of the present invention may be one kind or a mixture of at least two kinds. Specific examples of the mixture of at least two kinds include a mixture of 1,3-bis(3-methoxypropyl)imidazolium acetate and 1,3-bis(ethoxypropyl)imidazolium acetate, a mixture of 1,3-bis(3-methoxypropyl)imidazolium acetate and 1,3-bis(2-methoxyethyl)imidazolium acetate, and a mixture of 1,3-bis(3-methoxypropyl)imidazolium acetate and 1,3-bis[3-(2-methoxyethoxy)propyl]imidazolium acetate.

[0092] In the production method of the present invention, the esterifying agent used may be one kind or a mixture of at least two kinds. Specific examples of the mixture of at least two kinds 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.

[0093] The onium salt represented by formula (1) may contain an aprotic polar solvent. Examples of the aprotic polar solvent include, but are not particularly limited to, dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, acetonitrile, pyridine, etc., and it may contain two or more kinds of aprotic polar solvents. The aprotic polar solvent as described above hardly dissolves polysaccharides by itself, but when mixed with an onium salt or an onium salt composition and used, it can contribute to improving the solubility of polysaccharides, accelerating the dissolution rate of polysaccharides due to viscosity reduction, improving workability in the process of recovering polysaccharides and / or esterified polysaccharides, controlling the physical properties of the recovered polysaccharides and / or esterified polysaccharides, etc.

[0094] The use of the esterified polysaccharide obtained by the production method of the present invention is 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 protective 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 utilized.

Examples

[0095] Next, the present invention will be specifically described based on examples, but the present invention is not limited thereto in any way.

[0096] 1,3-bis(3-methoxypropyl)imidazolium acetate ([(MeOPr)2Im][AcO]) used in the examples was produced as described in the following [Production Example 1].

[0097] [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%.

[0098] As the 1-butyl-3-methylimidazolium acetate used in Comparative Example 1, that manufactured by Tokyo Chemical Industry Co., Ltd. was used.

[0099] [Comparative Example 1] Into a vial, 1.61 g of 1-butyl-3-methylimidazolium acetate and 0.41 g of cellulose (Avicel® PH-101) were placed and stirred at 80 °C for 5 hours. After 5 hours, when the dissolution of cellulose was checked, since cellulose remained undissolved, the production of esterified cellulose was aborted without adding an esterifying agent.

[0100] [Example 1] 1,3 - Di(3 - methoxypropyl)imidazolium acetate (1.60 g) and cellulose (0.41 g) (Avicel® PH - 101) were placed in a vial and stirred at 80 °C for 1 hour. After 1 hour, when the dissolution of cellulose was checked, the cellulose had completely dissolved. While cooling this reaction solution in an ice bath, acetic anhydride (2.74 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 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 as follows using 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 analysis. The measurement results were as follows. Degree of acetylation (DS) = 2.92

Industrial Applicability

[0101] According to the present invention, it is possible to increase the solubility of cellulose in an ionic liquid compared to the prior art, and to provide a method for producing an esterified polysaccharide, particularly a method for producing esterified cellulose, that substantially does not use a catalyst.

Claims

1. A method for producing an esterified polysaccharide, comprising the following steps (1), (2), (3) and (4). Step (1): A step of mixing a polysaccharide with an onium salt represented by formula (1) and dissolving the polysaccharide in the onium salt. (Formula 1) 【Chemical 1】 (In the formula, R １ and R ２ are the same or different and each represents a hydrocarbon group having 2 to 12 carbon atoms containing 1 to 5 heteroatoms, or a group represented by the following formula (1a). -O-R ａ (1a) (R ａ represents a hydrocarbon group having 1 to 12 carbon atoms which may contain 1 to 4 heteroatoms.) R ３ represents a hydrogen atom or a hydrocarbon group which may contain a hetero atom. The heteroatom is at least one selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom. R ４ represents a hydrocarbon group. However, when R １ and R ２ are a methoxyethyl group and R ３ is a hydrogen atom, R ４ represents a hydrocarbon group having 2 or more carbon atoms. ) Step (2): A step of adding an esterifying agent to the mixture obtained in step (1) to produce an esterified polysaccharide. Step (3): A step of adding at least one solvent selected from water, alcohol, and ketone to the mixture obtained in step (2) to precipitate the esterified polysaccharide. Step (4): A step of filtering the esterified polysaccharide from the mixture obtained in step (3) to obtain the esterified polysaccharide.

2. The method for producing an esterified polysaccharide according to claim 1, wherein at least two types of onium salts represented by formula (1) are used in step (1).

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

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

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