Method for producing acylated cellulose, acylated cellulose, and composition containing acylated cellulose

Abstract

The present invention provides a method for obtaining an acylated cellulose by performing a delignification treatment and an acylation treatment in a single-step reaction.　A method for producing an acylated cellulose according to the present disclosure enables the achievement of an acylated cellulose that has a repeating unit represented by formula (1), a total degree of substitution of R1CO groups of 0.1 to 3, and a structure of a cellulose crystal and / or a cellulose triester crystal through a step (I) in which lignocellulose (A) and a carboxylic acid (B) that is represented by formula (b) R1(COOH)m (wherein R1 represents a hydrocarbon group and m represents an integer of 1 or more) are reacted with each other.

Description

Method for producing acylated cellulose, acylated cellulose, and composition containing acylated cellulose

[0001] The present disclosure relates to a method for producing acylated cellulose, acylated cellulose, a resin composition containing acylated cellulose, a fiber-reinforced plastic containing acylated cellulose, a fiber-reinforced rubber containing acylated cellulose, a structure having a coating containing acylated cellulose, and a sheet containing acylated cellulose. This disclosure claims priority to PCT application PCT / JP2024 / 7613, filed February 29, 2024, the contents of which are incorporated herein by reference.

[0002] The cell walls of trees and herbs are mainly composed of lignocellulose, which is the most abundant natural polymer on Earth. It is therefore desirable to extract useful components from trees and herbs and utilize them effectively.

[0003] Lignocellulose is a plant material composed of cellulose, hemicellulose, and lignin, which have a complex intertwined higher-order structure. These components form the structural framework of plant cell walls. Specifically, cellulose, a linear polymer, forms a crystalline structure through intramolecular and intermolecular hydrogen bonds, forming strong microfibrils (cellulose microfibrils). Hemicelluloses such as xylan and glucomannan are entangled with this, and lignin, an irregular aromatic polymer, fills the voids in the polysaccharide matrix. In this way, lignin is tightly bound to cellulose and hemicellulose. Cellulose is a polymer compound formed by the polymerization of numerous glucose rings (glucopyranose units) via β-1,4-glycosidic bonds, making it a highly hydrophilic material. It is also difficult to mix with hydrophobic materials. Therefore, for applications where it is mixed with hydrophobic materials or where water resistance is required, it is derivatized to make it hydrophobic. Known examples of such cellulose derivatives include acylated celluloses such as cellulose acetate.

[0004] Known methods for producing acylated cellulose include reacting cellulose with an acylating agent such as acetic anhydride, propionic anhydride, or butyric anhydride (see, for example, Patent Document 1).

[0005] Furthermore, since cellulose contained in trees, herbs, etc. forms a complex with lignin, it is necessary to first decompose and remove the lignin before subjecting the cellulose to reaction with an acylating agent.

[0006] Patent Document 2 describes the production of dissolving pulp by subjecting lignocellulose to a hydrolysis-alkali cooking treatment to delignification.

[0007] Patent Document 3 describes a delignification reaction in which cedar powder is reacted with 1-methyl-3-(3-sulfopropyl)imidazolium p-toluenesulfonate (1 ml) in the presence of an aqueous hydrogen peroxide solution and toluene. Example 26 describes that cellulose obtained as a precipitate after the delignification reaction is acetylated in the presence of acetic anhydride.

[0008] Patent Document 4 describes the preparation of acetylated cellulose using wood flour, toluene, acetic anhydride, acetic acid, and sulfuric acid. In this document, acetylation is carried out without separating lignin from the wood flour, so the resulting product is an acetylated product of lignocellulose.

[0009] Patent Document 5 describes reacting lignocellulose in a mixture containing an ionic liquid and a linear or cyclic ester compound or an epoxy compound. That is, this document describes dissolving lignocellulose in an ionic liquid and reacting it.

[0010] Patent Document 6 describes that lignocellulose such as wood flour can be dissolved in formic acid, and that dissolving the cellulose in formic acid results in formylation of the cellulose.

[0011] Patent Document 7 describes a process of dissolving lignocellulose in an organic acid to obtain a solution, a process of adding water or an alkali to the solution to precipitate a solid, a process of recovering the solid, and a process of thermoforming the recovered solid. Formic acid is exemplified as the organic acid, and it is described that some or all of the hydroxyl groups of cellulose are formylated with formic acid.

[0012] Patent Document 8 describes that cellulose acetate nanofibers can be obtained by reacting defibrated cellulose nanofibers with a sulfuric acid catalyst and acetic anhydride in an organic solvent that does not dissolve cellulose. This document describes that the cellulose acetate nanofibers have a cellulose triacetate type I structure that maintains the cellulose type I structure.

[0013] US Patent No. 2,705,710 Specification Japanese Patent Application Laid-Open No. 2013-227705 International Publication No. 2021 / 125362 Japanese Patent Application Laid-Open No. 09-221501 International Publication No. 2016 / 068053 International Publication No. 2023 / 058088 International Publication No. 2023 / 199402 International Publication No. 2017 / 155054

[0014] As described above, conventionally, obtaining acylated cellulose from lignocellulose requires a two-step reaction: first, delignification to obtain cellulose, and then subjecting the obtained cellulose to an acylation reaction. This complicated process is problematic. The delignification process requires a huge amount of energy, and the black liquor obtained from delignification cannot be used and can only be incinerated.

[0015] Furthermore, as mentioned above, the acylated product obtained without delignification was merely an acetylated product of a lignin-cellulose complex, and it was not possible to separate fibrous acetyl cellulose from the lignin. Furthermore, when lignocellulose is directly dissolved in an ionic liquid, formic acid, or the like and acetylated, the cellulose type I crystal structure disappears. Naturally, the loss of the properties of the cellulose type I crystal (e.g., high strength, high elastic modulus, etc.) was a problem. A technology has been proposed that acetylates cellulose while maintaining its type I structure to provide nanofibers with a cellulose triacetate type I structure, but this does not use lignocellulose as a raw material, and separation of lignin and cellulose requires the conventional delignification process. A method of delignifying lignocellulose and then acetylating the resulting precipitate has also been proposed, but this requires a complicated two-step reaction and only yields nanofibers with a wide molecular weight distribution.

[0016] Therefore, an object of the present disclosure is to provide a method for obtaining acylated cellulose by performing delignification and acylation in a single reaction step. Another object of the present disclosure is to provide a method for obtaining acylated cellulose having a high affinity for hydrophobic materials and / or excellent water resistance by performing delignification and acylation in a single reaction step. Another object of the present disclosure is to provide an acylated cellulose, acylated cellulose nanofiber, or acylated cellulose nanosheet having a cellulose crystalline and / or cellulose triester crystalline structure. Another object of the present disclosure is to provide a method for obtaining acylated cellulose having a highly substituted cellulose triacetate type I crystalline structure having a high affinity for hydrophobic materials and / or excellent water resistance by performing delignification and acylation in a single reaction step. Another object of the present disclosure is to provide the acylated cellulose obtained by the method. Another object of the present disclosure is to provide acylated cellulose fiber, acylated microfibrillated cellulose, acylated cellulose nanofiber, and acylated cellulose nanosheet. Another object of the present disclosure is to provide a resin composition containing the acylated cellulose. Another object of the present disclosure is to provide a fiber-reinforced plastic containing the acylated cellulose. Another object of the present disclosure is to provide a fiber-reinforced rubber containing the acylated cellulose. Another object of the present disclosure is to provide a structure having a coating containing the acylated cellulose. Another object of the present disclosure is to provide a sheet containing the acylated cellulose.

[0017] As a result of intensive research to solve the above problems, the present inventors have found that when lignocellulose is heated in a solvent containing a carboxylic acid as both a solvent and an acylating agent, a delignification reaction and an acylation reaction proceed simultaneously, yielding acylated cellulose, and that the acylated cellulose thus obtained retains the properties of cellulose crystals (e.g., high strength, high elastic modulus, etc.) while also possessing newly acquired water resistance. The present disclosure has been completed based on these findings.

[0018] That is, the present disclosure provides a method for producing a lignocellulose (A) and a cellulose derivative represented by the following formula (b): １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more) in a ratio of 1.3 to 30 parts by weight of (B) per 1 part by weight of (A) (in terms of dry weight), to obtain a compound represented by the following formula (1): (In the formula, R １１ ~R １３ are the same or different and are a hydrogen atom or R １ R represents a CO group. １ is the same as above), and R １ A method for producing acylated cellulose is provided, which produces acylated cellulose having a total degree of CO group substitution of 0.1 to 3.

[0019] The present disclosure also provides a method for producing acylated cellulose, in which the reaction in step (I) is carried out in a solvent containing a carboxylic acid (B), and the concentration of the carboxylic acid (B) in the solvent is 30 wt % or more. The content of the water-insoluble organic solvent in the solvent is preferably 50 wt % or less (preferably 30 wt % or less, 15 wt % or less, or 0 wt %).

[0020] The present disclosure also provides that the acylated cellulose obtained has a cellulose crystal content of 30% or more by X-ray diffraction method or a solid content of 30% or more by X-ray diffraction method. １３ The present invention provides a method for producing the acylated cellulose, in which the proportion of cellulose crystals determined by C-NMR is 0.1 or more.

[0021] The present disclosure also provides a method for producing the acylated cellulose, wherein the resulting acylated cellulose has a lignin content of 7% by weight or less.

[0022] The present disclosure also provides the method for producing the acylated cellulose, in which the reaction in step (I) is further carried out in the presence of a peroxide and / or peracid (C), and the amount of (C) is 0.03 to 0.7 mol per mol of (B).

[0023] The present disclosure also provides the method for producing the acylated cellulose, in which the reaction in step (I) is carried out in the presence of a peroxide and / or peracid (C) and an acid catalyst (D), and the amount of (D) is 0.003 to 0.3 mol per 1 mol of (C).

[0024] The present disclosure also provides the method for producing the acylated cellulose, in which the reaction of the step (I) is further carried out in the presence of an acid catalyst (D), and the amount of (D) is 0.0003 to 0.03 mol per 1 mol of (B).

[0025] The present disclosure also provides the method for producing acylated cellulose, wherein the acid catalyst (D) is a compound represented by the following formula (d-1): (In the above formula, ring Z represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and R ２ represents a divalent hydrocarbon group; t represents an integer of 0 or more; and n represents an integer of 1 or more.

[0026] The present disclosure also provides a method for producing the acylated cellulose, which includes, in addition to step (I), step (II) of reacting the solid content of the reaction solution of step (I) with the following acylating agent (B') in an amount of 0.5 to 150 mmol per 1 g of lignocellulose (A) (in terms of dry weight): acylating agent (B'): at least one compound R selected from a carboxylic acid represented by formula (b') below, a halide of a carboxylic acid represented by formula (b') below, an anhydride of a carboxylic acid represented by formula (b') below, and a vinyl ester of a carboxylic acid represented by formula (b') below: １ (COOH) ｍ (b') (wherein, R １ , m is the same as above)

[0027] The present disclosure also provides the method for producing acylated cellulose, wherein the reaction in step (II) is carried out in the presence of a solvent that is a non-solvent or a poor solvent for the acylated cellulose to be produced, and the amount of the solvent used is 1 to 40 parts by weight per part by weight of the residue.

[0028] The present disclosure also provides a compound represented by the following formula (1): (In the formula, R １１ ~R １３ are the same or different and are a hydrogen atom or R１ represents a CO group, and the R １ represents a monovalent hydrocarbon group), and R １ An acylated cellulose having a total degree of CO group substitution of 0.1 to 3 is provided.

[0029] The present disclosure also provides the acylated cellulose described above, wherein the lignin content is 7% by weight or less.

[0030] The present disclosure also provides the acylated cellulose, which is fibrous and has an average aspect ratio (average fiber length / average fiber width) of 5 or more.

[0031] The present disclosure also provides a method for producing a cellulose crystalline product having a cellulose crystallinity of 30% or more by X-ray diffraction method, or a solid cellulose crystalline product having a cellulose crystallinity of 30% or more by X-ray diffraction method. １３ The acylated cellulose has a cellulose crystallinity of 0.1 or more as determined by C-NMR.

[0032] The present disclosure also provides a resin composition containing the acylated cellulose and a resin component.

[0033] The present disclosure also provides a fiber-reinforced plastic comprising the acylated cellulose and a plastic component.

[0034] The present disclosure also provides a fiber-reinforced rubber comprising the acylated cellulose and a rubber component.

[0035] The present disclosure also provides a structure having a coating comprising the acylated cellulose.

[0036] The present disclosure also provides a sheet comprising the acylated cellulose.

[0037] According to the manufacturing method disclosed herein, acylated cellulose can be obtained from lignocellulose in a single reaction step. The acylated cellulose thus obtained retains the properties of cellulose crystals (e.g., high strength, high modulus, etc.) while also exhibiting newly acquired water resistance and easy miscibility with hydrophobic materials. Therefore, when added to plastics or rubber, it is easily mixed, resulting in fiber-reinforced plastics or fiber-reinforced rubbers with high strength, high modulus, and excellent water resistance. Furthermore, by coating a structure with a film containing the acylated cellulose, a structure with high strength, high modulus, and excellent water resistance can be obtained. Furthermore, by incorporating the acylated cellulose into a sheet, a sheet with high strength, high modulus, and excellent water resistance can be obtained.

[0038] 1 is a diagram showing IR charts of Example 1, Comparative Example 1, and cedar heartwood flour used as a raw material. １３

[0033] Figure 1 shows the results of C-NMR measurement. Figure 2 shows a scanning electron microscope photograph of the acylated cellulose obtained in Example 13. Figure 3 shows a scanning electron microscope photograph of the acylated cellulose obtained in Example 14. Figure 4 shows an external photograph (a) of the sheet obtained in Example 15 and an external photograph (b) of the sheet obtained in Comparative Example 3. Figure 5 shows the results of X-ray diffraction of cellulose triacetate type I crystals (CTA I), cellulose triacetate type II crystals (CTA II), cellulose I (Reference Example 1), and cellulose II (Reference Example 2).

[0039] [Method for Producing Acylated Cellulose] The method for producing acylated cellulose according to the present disclosure comprises the steps of: １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more), to produce a compound represented by the following formula (1): (In the formula, R １１ ~R １３ are the same or different and are a hydrogen atom or R １ R represents a CO group. １ is the same as above), and R １The method for producing acylated cellulose provides acylated cellulose having a total degree of CO group substitution of 0.1 to 3 and a cellulose crystalline and / or cellulose triester crystalline structure.

[0040] (Lignocellulose (A)) Lignocellulose is a plant material containing cellulose, hemicellulose, and lignin, which have a higher-order structure in which they are intricately intertwined. Lignocellulose encompasses the aspects of "lignocellulose material" and "lignocellulose raw material." In this specification, "lignocellulose material" and "lignocellulose raw material" refer to materials containing, as their main component, "a higher-order structure containing cellulose, hemicellulose, and lignin, which are intricately intertwined." Furthermore, in this specification, "lignocellulose raw material" refers to a raw material that is subjected to the treatment specified in this disclosure, and is preferably obtained by crushing or disintegrating a lignocellulose material. However, in this embodiment, crushing or disintegration is not required, and any lignocellulose material having dimensions suitable for the treatment specified in this disclosure can be used as is as a lignocellulose raw material.

[0041] The lignocellulosic material used in this embodiment is not particularly limited, but may include one or more materials selected from the group consisting of woody biomass, herbaceous biomass, agricultural crops, leaf materials, fruit peels, cotton, and hemp.

[0042] The woody biomass may be coniferous trees such as cedar, cypress, red pine, etc., or broad-leaved trees such as eucalyptus and beech, and one or more of these may be used. From the viewpoint of effective utilization of dwindling forest resources, woody biomass that has traditionally been discarded can be suitably used. For example, wood flour generated during sawing, small pieces (chips) that cannot be used as scrap wood, etc. may be used in this embodiment. The woody biomass may be natural wood, or may be lumber products cut from natural wood. There are no particular limitations on the shape of the woody biomass, and it may be used in an appropriate form such as a plate, chips, or powder.

[0043] However, kraft pulp, which is made by treating wood chips with chemicals to decompose lignin and hemicellulose and liberate cellulose fibers, contains a small amount of lignin but is not suitable as a lignocellulosic material in the present disclosure. Furthermore, pulp contains lignin, but the strong bonds between hemicellulose and cellulose and lignin are almost completely freed, making it unsuitable as a lignocellulosic material in the present disclosure. In other words, in the present disclosure, lignocellulose preferably does not include products of delignification reactions and / or pulp that does not contain hemicellulose or bonds between cellulose and lignin.

[0044] Examples of herbaceous biomass include sugarcane bagasse, rice straw, wheat, bran, tomato, onion, and moso bamboo, and one or more of these may be used.

[0045] It should be noted that some edible plant grains, such as wheat flour, do not contain any lignin. These grains are not lignocellulosic materials. On the other hand, husks (e.g., rice and wheat husks) contain lignocellulose and are considered lignocellulosic materials in this disclosure.

[0046] The total content of higher-order structures in which cellulose, hemicellulose, and lignin are intricately intertwined in the lignocellulosic material is not particularly limited. The lignin content in the lignocellulosic material is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more. From the viewpoint of eliminating the need for a process for extracting higher-order structures in which cellulose, hemicellulose, and lignin are intricately intertwined from the lignocellulosic material, the lignin content in the lignocellulosic material is preferably 50% by mass or less.

[0047] The size of the lignocellulosic raw material subjected to the treatment specified in the present disclosure is not particularly limited, but from the viewpoint of promoting the reaction, the maximum diameter in plan view may be 50 mm or less, 40 mm or less, or 30 mm or less. On the other hand, from the viewpoint of preventing dust and reducing the energy required for fine grinding, the size of the lignocellulosic raw material is preferably a maximum diameter in plan view of 0.1 mm or more. Furthermore, from the viewpoint of promoting the reaction, it is preferable to use undersized lignocellulosic raw material that has passed through a sieve with a nominal mesh size of 3 mm when sieved according to JIS Z 8801:2019, and more preferably a sieve with a nominal mesh size of 1 mm. Furthermore, from the viewpoint of preventing dust and reducing the energy required for fine grinding, it is preferable to use oversized lignocellulosic raw material that does not pass through a sieve with a nominal mesh size of 0.1 mm.

[0048] (Lignocellulose components) Cellulose is a polysaccharide that forms the backbone of plant cell walls. ６ H １０ O ５ In plant cell walls, several dozen cellulose molecules are bundled together to form microfibrils, and multiple microfibrils then associate in a rope-like fashion to form microfibrils.

[0049] The percentage of cellulose relative to the total weight of cellulose and hemicellulose varies depending on the type of plant used as the raw material for the polysaccharides. When wood is used as the raw material, the cellulose content is approximately 50% by weight. When cotton fiber is used as the raw material, the cellulose content is, for example, 88 to 96% by weight.

[0050] Hemicellulose is a general term for polysaccharides other than cellulose that exist between cellulose microfibrils. Hemicellulose is composed of monosaccharides such as xylose, arabinose, mannose, and galactose, and has the effect of strengthening the cell wall by linking cellulose microfibrils to form a mesh structure.

[0051] Lignin is a polymeric compound in which a three-dimensional network structure is formed by the high degree of polymerization of phenolic compounds (for example, sinapyl alcohol, coniferyl alcohol, p-coumaryl alcohol, etc.).

[0052] (Cellulose crystalline structure and cellulose ester crystalline structure) The cellulose type I crystalline structure is a crystalline structure observed when naturally occurring cellulose is able to maintain its crystalline structure. For example, when natural cellulose is dissolved and then solidified to form crystals, it becomes a cellulose type II crystalline structure, and does not have a cellulose type I crystalline structure. Crystals obtained by triesterification without dissolving cellulose are called cellulose triester type I. Even when cellulose is acetylated, if the cellulose is dissolved and reacted once, it becomes a cellulose triacetate type II crystalline structure. The cellulose triacetate type I crystalline structure is only exhibited when the cellulose is acetylated without dissolving (i.e., while maintaining its crystallization). In this case, the cellulose crystals naturally have a microfibrillary structure, and therefore become fibrous. Acylated cellulose can be identified as having a cellulose triacetate type I crystal (hereinafter also referred to as CTA I) structure by the presence of typical peaks at two positions, around 2θ=7.6 to 8.6° and around 2θ=15.9 to 16.9°, in a diffraction profile obtained from an X-ray diffraction photograph using CuKα (λ=1.542184 Å).

[0053] Furthermore, the acylated cellulose can be identified as having a cellulose triacetate type II crystal (hereinafter also referred to as CTA II) structure by the presence of typical peaks at three positions: around 2θ = 7.9 to 8.9°, around 2θ = 9.9 to 10.9°, and around 2θ = 12.6 to 13.6°.

[0054] The acylated cellulose, acylated cellulose nanofiber, and acylated cellulose nanosheet of the present disclosure preferably have at least a cellulose crystalline and / or cellulose triester crystalline structure. The cellulose crystalline structure is preferably a cellulose type I crystalline structure. The cellulose triester crystalline is preferably a cellulose triacetate crystalline structure. The cellulose triacetate crystalline structure is preferably a cellulose triacetate type I structure. That is, it is preferable that the cellulose crystals have a portion that does not dissolve. Alternatively, it is preferable that the cellulose crystals have a portion that is acylated without dissolving. The greater the degree of acylation, the more cellulose triacetate type I structure there is in the acylated cellulose. When the degree of acylation is low (for example, an average degree of substitution of about 1), the surface layer of the fiber has a cellulose triacetate type I structure, and the interior has a cellulose triacetate type I crystalline structure.

[0055] (Carboxylic Acid (B)) Carboxylic acid (B) is a compound represented by the following formula (b): １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more.

[0056] The hydrocarbon group is an m-valent hydrocarbon group, and includes m-valent aliphatic hydrocarbon groups, m-valent alicyclic hydrocarbon groups, m-valent aromatic hydrocarbon groups, and m-valent groups formed by combining these groups.

[0057] Among the m-valent aliphatic hydrocarbon groups, the monovalent aliphatic hydrocarbon group has 1 to 20 carbon atoms (=C １－２０) is preferred, and examples thereof include alkyl groups having 1 to 20 carbon atoms (preferably 1 to 10, particularly preferably 1 to 5, and most preferably 1 to 3), such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, decyl, and dodecyl; alkenyl groups having 2 to 20 carbon atoms (preferably 2 to 10, particularly preferably 2 to 3), such as vinyl, allyl, and 1-butenyl; and alkynyl groups having 2 to 20 carbon atoms (preferably 2 to 10, particularly preferably 2 to 3), such as ethynyl and propynyl.

[0058] Examples of the m-valent aliphatic hydrocarbon group include groups in which (m-1) hydrogen atoms have been removed from the structural formula of the monovalent aliphatic hydrocarbon group.

[0059] Among the m-valent alicyclic hydrocarbon groups, the monovalent alicyclic hydrocarbon group is C ３－２０ Alicyclic hydrocarbon groups are preferred, and examples thereof include cycloalkyl groups having about 3 to 20 members (preferably 3 to 15 members, particularly preferably 5 to 8 members) such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cyclooctyl groups; cycloalkenyl groups having about 3 to 20 members (preferably 3 to 15 members, particularly preferably 5 to 8 members) such as cyclopentenyl and cyclohexenyl groups; perhydronaphthalen-1-yl groups, norbornyl groups, adamantyl groups, tricyclo[5.2.1.0] groups, and the like. ２，６ ] decan-8-yl group, tetracyclo[4.4.0.1 ２，５ .1 ７，１０ ] Bridged cyclic hydrocarbon groups such as dodecan-3-yl group and the like can be given.

[0060] Examples of the m-valent alicyclic hydrocarbon group include groups in which (m-1) hydrogen atoms have been removed from the structural formula of the monovalent alicyclic hydrocarbon group.

[0061] Among the m-valent aromatic hydrocarbon groups, the monovalent aromatic hydrocarbon group is C ６－１４ (Especially C ６－１０ Aromatic hydrocarbon groups are preferred, such as phenyl and naphthyl groups.

[0062] Examples of the m-valent aromatic hydrocarbon group include groups in which (m-1) hydrogen atoms have been removed from the structural formula of the monovalent aromatic hydrocarbon group.

[0063] The hydrocarbon group may have various substituents [e.g., halogen atoms, oxo groups, hydroxy groups, substituted oxy groups (e.g., alkoxy groups, aryloxy groups, aralkyloxy groups, acyloxy groups, etc.), substituted oxycarbonyl groups (e.g., alkoxycarbonyl groups, aryloxycarbonyl groups, aralkyloxycarbonyl groups, etc.), substituted or unsubstituted carbamoyl groups, cyano groups, nitro groups, substituted or unsubstituted amino groups, sulfo groups, heterocyclic groups, etc.]. The hydroxy groups may be protected with protective groups commonly used in the field of organic synthesis. Furthermore, aromatic or non-aromatic heterocycles may be condensed with the rings of the alicyclic hydrocarbon group or aromatic hydrocarbon group.

[0064] The above m is the number of carboxy groups that the carboxylic acid (B) has, and represents an integer of 1 or more. m is preferably an integer of 1 to 5, particularly preferably 1 or 4, and most preferably 1.

[0065] Examples of the carboxylic acid (B) include aliphatic monocarboxylic acids such as acetic acid, propionic acid, lactic acid, glycolic acid, and glyoxylic acid; aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, maleic acid, glutamic acid, and malic acid; aliphatic polycarboxylic acids such as citric acid, 1,2,3,4-cyclobutanetetracarboxylic acid, and 1,2,4,5-cyclohexanetetracarboxylic acid; aromatic monocarboxylic acids such as benzoic acid, 2-chlorobenzoic acid, 4-(chloromethyl)benzoic acid, salicylic acid, 1-naphthoic acid, and diphenylacetic acid; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid; and aromatic polycarboxylic acids such as trimesic acid. These may be used alone or in combination of two or more.

[0066] In accordance with common technical knowledge, in the present disclosure, carboxylic acid anhydrides are classified as carboxylic acid anhydrides and are not included in the category of carboxylic acid (B), because carboxylic acid anhydrides have the function of destroying cellulose type I structure and promoting acylation, particularly in the presence of sulfuric acid.

[0067] It is of course permissible to add a step of reacting the solid obtained through step (I) of the present disclosure with a carboxylic acid anhydride.

[0068] In addition, as is clear from the definition of carboxylic acid (B) in the present disclosure, formic acid is not included in carboxylic acid (B). The reason is that, as mentioned above, high concentrations of formic acid alone have the function of destroying cellulose type I structures and dissolving lignocellulose. It is preferable not to use formic acid in step (I).

[0069] The amount of carboxylic acid (B) used is preferably 1.3 to 30 parts by weight per part by weight of the lignocellulose (A) (in terms of dry weight). The lower limit of the amount of carboxylic acid (B) used is preferably 3 parts by weight, more preferably 5 parts by weight, and particularly preferably 8 parts by weight. The upper limit of the amount of carboxylic acid (B) used is preferably 20 parts by weight.

[0070] The reaction is preferably carried out in a solvent containing the carboxylic acid (B).

[0071] From the viewpoint of promoting the reaction, the concentration of the carboxylic acid (B) in the solvent is, for example, 30% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 85% by weight or more. The upper limit of the concentration of the carboxylic acid (B) in the solvent is 100% by weight.

[0072] For example, a carboxylic acid may be produced in the reaction system by using a carboxylic acid anhydride that reacts with water to produce a carboxylic acid, together with water, thereby making it possible to adjust the concentrations of water and carboxylic acid in the solvent.

[0073] The solvent may also contain a water-insoluble organic solvent such as toluene, but the content of the water-insoluble organic solvent in the solvent is, for example, 70% by weight or less, preferably 40% by weight or less, particularly preferably 30% by weight or less, most preferably 20% by weight or less, and particularly preferably 15% by weight or less, 10% by weight or less, 5% by weight or less, or 0% by weight.

[0074] The amount of the solvent used (total amount when two or more types are used) is preferably 1.3 times or more by weight, more preferably 2 times or more by weight, and even more preferably 3 times or more by weight relative to the weight (dry weight) of lignocellulose (A). From the viewpoint of efficiently promoting the reaction, the upper limit of the amount of the solvent used is, for example, 30 times by weight, preferably 20 times by weight, more preferably 15 times by weight, even more preferably 10 times by weight, particularly preferably 8 times by weight, and most preferably 6 times by weight relative to the weight of lignocellulose (A).

[0075] (Peroxide and / or Peracid (C)) The reaction can be carried out in the presence of a peroxide and / or a peracid. Peroxides and peracids have excellent delignification effects, so when the reaction is carried out in the presence of a peroxide and / or a peracid, the amount of lignin contained in the acylated cellulose can be further reduced.

[0076] The peroxide may be a compound represented by the following formula (c): ２１ -O-O-R ２２ (c) (wherein, R ２１ , R ２２ are the same or different and represent a hydrogen atom, a monovalent hydrocarbon group, or an acyl group. The acyl group is represented by an RCO group, where R is a monovalent hydrocarbon group.

[0077] The monovalent hydrocarbon group includes a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, a monovalent aromatic hydrocarbon group, and a monovalent group formed by combining these groups.

[0078] Of the monovalent hydrocarbon groups, monovalent aliphatic hydrocarbon groups, monovalent aromatic hydrocarbon groups, and monovalent groups in which two or more of the above groups are bonded are preferred.

[0079] The monovalent aliphatic hydrocarbon group is preferably an aliphatic hydrocarbon group having 1 to 20 carbon atoms, and particularly preferably a linear or branched alkyl group having 1 to 20 carbon atoms (preferably 1 to 10, and particularly preferably 1 to 5).

[0080] The monovalent aromatic hydrocarbon group is preferably an aryl group having 6 to 14 carbon atoms (preferably 6 to 10 carbon atoms), such as a phenyl group or a naphthyl group.

[0081] As the monovalent group formed by bonding two or more groups selected from monovalent aliphatic hydrocarbon groups and monovalent aromatic hydrocarbon groups, an aralkyl group having 7 to 10 carbon atoms, such as a benzyl group, is preferred.

[0082] The peroxide may be, for example, hydrogen peroxide (a compound represented by formula (c), wherein R ２１ , R ２２ represents a hydrogen atom); hydroperoxides such as t-butyl hydroperoxide and benzyl hydroperoxide (compounds represented by formula (c), ２１ represents a monovalent hydrocarbon group, and R ２２ represents a hydrogen atom); peroxides such as di-t-butyl peroxide and benzoyl peroxide (compounds represented by formula (c), ２１ , R ２２ and the like may be the same or different and each represents a monovalent hydrocarbon group or an acyl group).

[0083] Examples of the peracid include organic peracids such as percarboxylic acids (e.g., peracetic acid, trifluoroperacetic acid, perbenzoic acid, metachloroperbenzoic acid, monoperoxyphthalic acid, etc.); and inorganic peracids such as permanganic acid. These may be used alone or in combination of two or more.

[0084] The amount of peroxide or peracid used (the total amount when a peroxide and a peracid are used in combination) is, for example, 0.03 to 0.7 mol, preferably 0.06 to 0.3 mol, and particularly preferably 0.075 to 0.2 mol per mol of carboxylic acid (B).

[0085] The amount of peroxide or peracid used (or the total amount when a peroxide and a peracid are used in combination) can be varied depending on the amount of lignin contained in the lignocellulose (A), but is, for example, 0.2 to 5.0 mmol, preferably 0.5 to 5.0 mmol, particularly preferably 0.7 to 4.0 mmol, and most preferably 1.0 to 3.0 mmol per 100 mg of lignocellulose (A). When the amount of peroxide or peracid used is within the above range, the oxidation and / or decomposition reaction of the lignin contained in the lignocellulose (A) proceeds rapidly, resulting in an acylated cellulose with an extremely low residual lignin content. Furthermore, by suppressing excessive decomposition, an acylated cellulose with an appropriate molecular weight can be obtained.

[0086] (Acid Catalyst (D)) The reaction can be further carried out in the presence of an acid catalyst. The acid catalyst preferably reacts with a peroxide or a peracid to produce a peroxide derived from the acid catalyst. The produced peroxide derived from the acid catalyst exhibits the effect of promoting the progress of the delignification reaction. Furthermore, the oxides and / or decomposition products of lignin produced by the delignification reaction are released from the lignin-polysaccharide complex and dissolve in water and / or an organic solvent. Therefore, the acid catalyst has the effect of acting as a dissolution promoter, promoting the dissolution of lignin in water and / or an organic solvent.

[0087] The acid catalyst may be an inorganic acid or an organic acid, and these may be used alone or in combination of two or more.

[0088] Examples of the inorganic acid include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

[0089] Examples of the organic acid include sulfonic acid, phosphonic acid, and phosphinic acid. The organic acid may be a hydrate. When the organic acid has a plurality of acid groups, some of the acid groups may form salts. An organic acid in which some of the acid groups form salts may be liquid at room temperature (25°C). That is, the organic acid may be an ionic liquid.

[0090] Examples of the salts that may be formed by the organic acids include alkali metal salts such as sodium salts and potassium salts; alkaline earth metal salts such as calcium salts and magnesium salts; and amine salts such as imidazole salts and pyridine salts.

[0091] The sulfonic acid has a sulfonic acid group (SO ３ R—(H group) and is represented by the following formula (d): ３ H) ｎ (d) (wherein R represents an n-valent hydrocarbon group or an n-valent heterocyclic group, and n represents an integer of 1 or more)

[0092] Among the n-valent hydrocarbon groups in R, the monovalent hydrocarbon group is １ Examples of the n-valent hydrocarbon group, where n is an integer of 2 or greater, include groups in which (n-1) hydrogen atoms have been removed from the structural formula of the monovalent hydrocarbon group described above.

[0093] The heterocycle constituting the n-valent heterocyclic group in R includes aromatic heterocycles and non-aromatic heterocycles. Examples of the heterocycle include 3- to 10-membered rings (preferably 4- to 6-membered rings) containing carbon atoms and at least one heteroatom (e.g., oxygen atom, sulfur atom, nitrogen atom, phosphorus atom, etc.) as ring-constituting atoms. The heterocycle may be condensed with a 3- to 8-membered cycloalkane ring.

[0094] The sulfonic acids include aliphatic sulfonic acids such as methanesulfonic acid and trifluoromethanesulfonic acid; and aromatic sulfonic acids such as compounds represented by the following formula (d-1). (In the above formula, ring Z represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and R ２ represents a divalent hydrocarbon group; t represents an integer of 0 or more; and n represents an integer of 1 or more.

[0095] As the sulfonic acid, the aromatic sulfonic acid is preferred because it has an excellent effect of accelerating the delignification reaction.

[0096] Examples of the aromatic hydrocarbon ring in the ring Z include aromatic hydrocarbon rings having 6 to 14 carbon atoms, such as a benzene ring, a naphthalene ring, and an anthracene ring. A 3- to 8-membered cycloalkane ring may be condensed with the aromatic hydrocarbon ring.

[0097] Examples of the aromatic heterocycle for ring Z include a 3- to 10-membered (preferably 4- to 6-membered) aromatic heterocycle having at least one heteroatom, and a fused ring formed by fusing a 3- to 8-membered cycloalkane ring to the aromatic heterocycle. Specific examples include pyrrole, furan, thiophene, phosphole, pyrazole, imidazole, oxazole, isoxazole, thiazole, indole, benzofuran, benzothiophene, isoindole, isobenzofuran, benzophosphole, benzimidazole, benzoxazole, benzothiazole, benzisoxazole, indazole, benzisothiazole, benzotriazole, purine, pyridine, phosphinine, pyrimidine, pyrazine, pyridazine, triazine, 1,2,4,5-tetrazine, 1,2,3,4-tetrazine, 1,2,3,5-tetrazine, hexazine, quinoline, isoquinoline, quinoxaline, quinazoline, cinnoline, pteridine, phthalazine, acridine, 4aH-phenoxazine, and carbazole.

[0098] The R ２ The divalent hydrocarbon group in is preferably a divalent (saturated) aliphatic hydrocarbon group, particularly preferably an alkylene group having 1 to 10 carbon atoms, and most preferably an alkylene group having 1 to 7 carbon atoms.

[0099] Examples of the compound represented by formula (d-1) in which ring Z in the formula is an aromatic hydrocarbon ring include benzenesulfonic acid; toluenesulfonic acids such as p-toluenesulfonic acid; and naphthalenesulfonic acids such as 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, 1,5-naphthalenedisulfonic acid, and 2-naphthylmethanesulfonic acid.

[0100] Examples of the compound represented by formula (d-1) in which ring Z is an aromatic heterocycle include 1-methyl-3-(3-sulfopropyl)imidazolium p-toluenesulfonate and 2-(3-(2-sulfoethyl)-1H-imidazol-1-yl)ethanesulfonate.

[0101] Examples of the phosphonic acids include aliphatic phosphonic acids such as methylphosphonic acid; and aromatic phosphonic acids such as phenylphosphonic acid.

[0102] Examples of the phosphinic acid include aliphatic phosphinic acids such as dimethylphosphinic acid; and aromatic phosphinic acids such as diphenylphosphinic acid.

[0103] Of these, the acid catalyst is preferably sulfonic acid or sulfuric acid, more preferably sulfonic acid, and most preferably aromatic sulfonic acid.

[0104] The amount of the acid catalyst (D) used (the total amount when two or more acid catalysts are used) is, for example, 0.0001 to 0.03 mol, preferably 0.0005 to 0.01 mol, and particularly preferably 0.001 to 0.005 mol per 1 mol of the carboxylic acid (B).

[0105] The amount of the acid catalyst (D) used (the total amount when two or more acid catalysts are used) is, for example, 0.001 to 0.3 mol, preferably 0.005 to 0.1 mol, and particularly preferably 0.01 to 0.05 mol per mol of the peroxide or peracid (C).

[0106] The amount of the acid catalyst (D) used (total amount when two or more types of acid catalysts are used) is, for example, 0.001 to 1.0 mmol, preferably 0.005 to 0.5 mmol, particularly preferably 0.01 to 0.1 mmol per 100 mg of lignocellulose (A).

[0107] When the acid catalyst (D) is sulfonic acid or sulfuric acid, the amount used is, for example, 1 to 100 μmol, preferably 5 to 70 μmol, particularly preferably 10 to 50 μmol, and most preferably 15 to 40 μmol, per 100 mg of lignocellulose (A).

[0108] (Reaction Conditions) The reaction atmosphere is not particularly limited as long as it does not inhibit the reaction, and may be, for example, any of an air atmosphere, a nitrogen atmosphere, an argon atmosphere, and the like.

[0109] In the present disclosure, a preferred combination of the solvent, the acylating agent (B'), and the acid catalyst (D) is as follows: Solvent: Carboxylic acid (B) Acylating agent (B'): Carboxylic acid represented by the above formula (b') Acid catalyst (D): One or more selected from the group consisting of sulfonic acid, phosphonic acid, phosphinic acid, and ionic liquid

[0110] The delignification reaction may be carried out under normal pressure, reduced pressure, or increased pressure.

[0111] The reaction temperature is, for example, 120°C or lower, preferably 100°C or lower, more preferably 90°C or lower, even more preferably 85°C or lower, and particularly preferably 80°C or lower. The lower limit of the reaction temperature is, for example, 20°C, preferably 50°C, and particularly preferably 60°C. The reaction time is, for example, about 0.5 to 48 hours, preferably 1 to 12 hours, and particularly preferably 1 to 4 hours. The reaction can be carried out by any method, such as a batch method, a semi-batch method, or a continuous method.

[0112] When lignocellulose (A) is subjected to the reaction, the lignin contained in the lignocellulose (A) is oxidized and / or decomposed and released from the cellulose fibers. After the lignin is released, the cellulose fibers are partially acylated on the surface, producing acylated cellulose, with cellulose crystals remaining in the fiber shafts.

[0113] The acyl group substitution degree of the acylated cellulose thus obtained (R １ The total degree of CO group substitution is 0.1 or more (for example, 0.1 to 3, preferably 0.3 to 2.0, particularly preferably 0.4 to 1.5, most preferably 0.5 to 1.4, and particularly preferably 0.6 to 1.2).

[0114] If it is desired to further increase the degree of acyl group substitution of the acylated cellulose, the following step (II) may be carried out after the above step (I): Step (II): The solid content of the reaction solution of step (I) is reacted with the acylating agent (B') described below in a proportion of 0.5 to 150 mmol per 1 g of lignocellulose (A) (in terms of dry weight).

[0115] The acylating agent (B') is at least one compound selected from the group consisting of a carboxylic acid represented by the following formula (b'), a halide of a carboxylic acid represented by the following formula (b'), an anhydride of a carboxylic acid represented by the following formula (b'), and a vinyl ester of a carboxylic acid represented by the following formula (b'). The acylating agent (B') is sometimes referred to as an esterifying agent. １ (COOH) ｍ (b') (wherein, R １ , m is the same as above)

[0116] In place of the acylating agent (B'), a compound capable of forming the acylating agent (B') in the reaction system can also be used.

[0117] The amount of the acylating agent (B') used is, for example, 0.5 to 150 mmol, preferably 1 to 50 mmol, and particularly preferably 1.5 to 20 mmol, per 1 g of the lignocellulose (A) (calculated as dry weight).

[0118] In step (II), the acylating agent (B') may be added to the reaction solution of step (I) to carry out the reaction, but from the viewpoint of more efficient acylation, it is preferable to subject the reaction solution of step (I) to a treatment such as filtration or centrifugation to remove the liquid component (including lignin and hemicellulose-derived components), and then add the acylating agent (B') to the solid component (or filtrate) to carry out the reaction. If the acylating agent (B') is added directly to the reaction solution of step (I), the lignin and hemicellulose-derived components contained in the filtrate will also be acylated, so the timing of carrying out the treatment such as filtration or centrifugation should be selected depending on the intended use of the filtrate.

[0119] The reaction in step (II) is preferably carried out in the presence of a solvent that is a non-solvent or a poor solvent for the acylated cellulose produced, since this allows acylation to a higher degree while maintaining the shape of the lignocellulose-derived cellulose fibers and / or cellulose crystals.

[0120] When the acylated cellulose to be produced is cellulose acetate, examples of the non-solvent or poor solvent include aromatic hydrocarbon solvents such as benzene, toluene, and xylene; hexane, cyclohexane, etc. These can be used alone or in combination of two or more.

[0121] The amount of the solvent used (the total amount when two or more solvents are used) is 1 to 40 times by weight, preferably 2 to 20 times by weight, and more preferably 3 to 10 times by weight, relative to the weight of the residue (preferably, the dry weight), from the viewpoint of efficiently promoting the reaction.

[0122] The solvent may contain a good solvent (a solvent that is a good solvent for the acylated cellulose to be produced) in addition to the non-solvent and poor solvent. However, the content of the good solvent is preferably within a range in which the solvent is a non-solvent or poor solvent for the acylated cellulose to be produced (i.e., within a range in which the proportion of the acylated cellulose to be produced that dissolves is, for example, 10 wt % or less).

[0123] The solvent may be present from the stage of step (I). When the reaction of step (II) is carried out in the presence of a good solvent for the acylated cellulose to be produced, it is preferable to carry out the reaction without using the acid catalyst (D) or using a very small amount of the acid catalyst (D), since this makes it easier to acylate the lignocellulose-derived cellulose while maintaining the shape of the cellulose fibers and / or the cellulose crystals.

[0124] After completion of the reaction, the liquid in the reaction system is cooled to room temperature (e.g., 25°C) as necessary and then subjected to filtration (for example, filter paper with a pore size of 1 to 5 µm can be used as the filtration membrane), thereby obtaining acylated cellulose as a residue.

[0125] The residue may be subjected to a drying treatment. Furthermore, the residue may be subjected to a washing treatment, if necessary, before the drying treatment. Water or the organic solvents described above can be used for the washing treatment.

[0126] The acylated cellulose obtained as the residue may be subjected to a micronization treatment, if necessary. The acylated cellulose is a fiber bundle in which multiple fibers are bonded together by hydrogen bonds. By severing the hydrogen bonds between the fibers through a micronization treatment, the fiber bundle can be broken down along the axial direction, resulting in acylated cellulose with a fiber width on the micro- to nano-level, i.e., acylated microfibrillated cellulose or acylated cellulose nanofiber. Furthermore, by combining the reaction conditions and micronization conditions, it is also possible to obtain acylated cellulose nanosheets with a thickness on the order of nanometers (e.g., 10 to 90 nm).

[0127] In step (I), acyl groups are formed in the gaps (e.g., on the surfaces of cellulose microfibrils or bundles thereof) that are generated after the removal of lignin and hemicellulose from lignocellulose (A), thereby preventing the formation of strong hydrogen bonds between the molecules or microfibril surfaces of the newly generated acylated cellulose. This allows acylation to proceed extremely smoothly in the subsequent step (II). On the other hand, in conventional methods, the cellulose is dried after delignification and then acylated. However, the drying treatment generates strong (hydrogen) bonds between the cellulose microfibrils, eliminating the gaps, making it difficult for the subsequent acylation reaction to proceed. Therefore, various pretreatments were required before acylation.

[0128] The method of the present disclosure makes it possible to produce acylated cellulose similar to that obtained by conventional methods at lower cost, with higher quality, and with less energy consumption than conventional methods. Furthermore, the method of the present disclosure is energy-efficient because it omits the drying process, which is energy-intensive in conventional methods.

[0129] The acylated cellulose obtained through the above process has a low lignin content, for example, 7% by weight or less, preferably 5% by weight or less, particularly preferably 3% by weight or less, and most preferably 2.5% by weight or less. The lignin is a lignin-derived component remaining after hydrolysis of acylated cellulose by the Klason method and removal of sugars and the like.

[0130] The acylated cellulose obtained through the above steps may be subjected to a step of further reducing lignin, if necessary, within the range that does not result in elimination of the introduced acyl groups. For example, an oxidizing agent (e.g., hypochlorite, chlorine dioxide, ozone, oxygen, etc.) different from the peroxide and / or peracid used in step (I) can be used.

[0131] Furthermore, the low lignin content of the acylated cellulose obtained through the above process can also be confirmed by IR measurement. －１ (e.g., 1490-1530 cm －１ ) peak is reduced or almost disappeared, or the peak at 1032 cm －１ around (for example, 1010 to 1040 cm －１ ) absorbance of the peak at 1510 cm －１ This can be confirmed by checking that the ratio of absorbances of nearby peaks is 0.008 or less (preferably 0.006 or less, and more preferably 0.005 or less).

[0132] The acylated cellulose obtained through the above steps has a cellulose crystal content determined by the XRD area method of, for example, 30% or more, preferably 50% or more, more preferably 60% or more, particularly preferably 65% ​​or more, and most preferably 70% or more. The upper limit of the cellulose crystal content is, for example, 80%.

[0133] The acylated cellulose obtained through the above process is a solid １３The proportion of cellulose crystals determined by C-NMR is, for example, 0.1 or more, preferably 0.2 or more, particularly preferably 0.3 or more, and most preferably 0.4 or more. The upper limit of the proportion of cellulose crystals is, for example, 0.8, preferably 0.6, particularly preferably 0.5.

[0134] The acylated cellulose obtained through the above process may contain hemicellulose, but the hemicellulose content is, for example, 15% by weight or less, preferably 12% by weight or less, more preferably 10% by weight or less, and particularly preferably 8% by weight or less.

[0135] The acylated cellulose obtained through the above steps may be further subjected to a step of reducing hemicellulose, if necessary, within the range that does not result in elimination of the introduced acyl groups.

[0136] The average fiber width of the acylated cellulose is, for example, 3 nm to 400 μm, preferably 10 nm to 100 μm, particularly preferably 10 nm to 1 μm, and most preferably 10 nm to 50 nm. The average fiber width of the acylated cellulose is determined by taking electron microscope images of a sufficient number of fibers (e.g., 30 fibers) using an electron microscope (SEM, TEM), measuring the fiber widths, and calculating the arithmetic average.

[0137] The average fiber length (L) of the acylated cellulose is, for example, 1 μm or more, preferably 2 μm or more, and more preferably 10 μm or more. The upper limit of the average fiber length is, for example, 5 mm, and preferably 3 mm.

[0138] The acylated cellulose is fibrous, and has an average aspect ratio (average fiber length / average fiber width) of, for example, 5 or more, preferably 10 or more, particularly preferably 50 or more, preferably 100 or more, preferably 500 or more, more preferably 1000 or more, even more preferably 1500 or more, particularly preferably 2000 or more, and most preferably 2500 or more. The upper limit of the average aspect ratio is, for example, 100,000, preferably 50,000, and particularly preferably 10,000.

[0139] The acylated cellulose obtained by the above method is useful not only as a sheet-forming material but also as an additive for imparting water resistance, high strength and high elastic modulus to resins such as plastics and rubbers.

[0140] [Resin Composition] The resin composition of the present disclosure contains the acylated cellulose and resin components, which include a thermoplastic resin and a thermosetting resin.

[0141] Thermoplastic resins include general-purpose plastics, engineering plastics, and super engineering plastics.

[0142] Examples of general-purpose plastics include polyolefins such as polyethylene and polypropylene; vinyl chloride resins such as polyvinyl chloride (PVC) and vinylidene chloride (PVDC); acrylic resins such as polymethyl methacrylate; styrene resins such as polystyrene, ABS resin, AS resin, AAS resin, ACS resin, AES resin, MS resin, SMA resin, and MBS resin; polyesters such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; alkyd resins; and unsaturated polyester resins.

[0143] Examples of engineering plastics include polyamides such as nylon 6, nylon 66, nylon 610, nylon 11, and nylon 12; polyethers such as polyacetal and polyphenylene ether; and polycarbonate.

[0144] Examples of super engineering plastics include fluorine-based resins such as polyvinylidene fluoride; sulfur-containing polymers such as polyphenylene sulfide and polyether sulfone; polyimide; polyamide imide; polyether imide; polyether ether ketone; and the like.

[0145] Examples of thermosetting resins include silicone resins, urethane resins, vinyl ester resins, phenoxy resins, epoxy resins, amino resins such as urea resins, melamine resins, and benzoguanamine resins, phenol resins, acrylic urethane resins, and acrylic silicone resins.

[0146] Other examples of thermosetting resins include synthetic rubbers such as styrene-isoprene block polymer, isoprene rubber, butadiene rubber, styrene-butadiene rubber, chloroprene rubber, nitrile rubber, butyl rubber, ethylene-propylene rubber, acrylic rubber, fluororubber, epichlorohydrin rubber, urethane rubber, and silicone rubber; and natural rubber.

[0147] The resin composition contains, for example, 0.1 to 400 parts by weight of the acylated cellulose per 100 parts by weight of the resin component.

[0148] The resin composition may contain other components (for example, a solvent, a curing agent, a flame retardant, a plasticizer, an antioxidant, an ultraviolet absorber, a colorant, a filler, etc.) in addition to the above, as needed.

[0149] The resin composition can be produced by blending and mixing the above components with other components as required.

[0150] [Fiber-reinforced plastic] The fiber-reinforced plastic of the present disclosure contains the acylated cellulose and a plastic component.

[0151] The plastic components include general-purpose plastics, engineering plastics, and super engineering plastics.

[0152] The content of the acylated cellulose is, for example, 0.1 to 200 parts by weight per 100 parts by weight of the plastic component.

[0153] The fiber-reinforced plastic can be molded by a method such as injection molding, etc. The molded article thus obtained has the water resistance, high strength, and high elastic modulus imparted by the acylated cellulose.

[0154] [Fiber-reinforced rubber] The fiber-reinforced rubber of the present disclosure contains the acylated cellulose and a rubber component.

[0155] The rubber component includes the above-mentioned synthetic rubber and natural rubber.

[0156] The content of the acylated cellulose is, for example, 0.1 to 100 parts by weight based on 100 parts by weight of the rubber component.

[0157] The fiber-reinforced rubber can be filled into a mold or the like and subjected to a heat treatment to form a molded article. The molded article thus obtained has the water resistance, high strength, and high elastic modulus imparted by the acylated cellulose.

[0158] [Sheet] The sheet of the present disclosure contains the acylated cellulose.

[0159] In the sheet, the content of the acylated cellulose is, for example, 10% by weight or more.

[0160] The sheet can be produced by applying an aqueous dispersion of the acylated cellulose to a substrate or the like and drying it.

[0161] The sheet has water resistance, high strength, and high elastic modulus provided by the acylated cellulose, and is also transparent.

[0162] The sheet is useful as, for example, an optical film for liquid crystal displays, a filter membrane, a filter, a cigarette filter, and the like.

[0163] The above-described configurations and combinations thereof of the present disclosure are merely examples, and additions, omissions, substitutions, and modifications of the configurations are possible as appropriate within the scope of the present disclosure. Furthermore, the present disclosure is not limited to the embodiments, but is limited only by the claims.

[0164] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples.

[0165] Example 1 A cylindrical glass reactor with a diameter of 35 mm was charged with 2 g of 1 mm-pass cedar wood flour (10% moisture) pulverized using a Willey mill, 0.526 mmol of p-toluenesulfonic acid monohydrate (Fujifilm Wako Pure Chemical Industries, Ltd.) as a catalyst, 2 mL of 30% hydrogen peroxide solution (Fujifilm Wako Pure Chemical Industries, Ltd.), 10 mL of acetic acid (Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent, and a stirrer, and the reaction was carried out by stirring at 60 °C for 24 hours. After cooling, the reaction product was removed from the glass reactor and filtered using filter paper with a pore size of 5 μm. The residue on the filter paper was washed sequentially with acetic acid, water, a 0.15% aqueous sodium bicarbonate solution, and water. The weight of the resulting water-wet residue was measured. A portion was collected and dried using a freeze dryer, and the solids concentration of the residue was calculated based on the change in weight before and after drying. The dry weight (A) of the total solids obtained in the reaction was calculated from this solid concentration and the weight of the water-wet filter cake. The ratio of (A) to the dry weight (B) of the wood flour used in the reaction was calculated as the yield (%).

[0166] Comparative Example 1 A reaction product was obtained in the same manner as in Example 1, except that toluene was used instead of acetic acid as the solvent and the cleaning agent.

[0167] The IR charts of Example 1, Comparative Example 1, and the cedar wood flour used as the raw material are shown in Figure 1. In both Example 1 and Comparative Example 1, the 1510 cm －１ In Example 1, the peak at 1735 cm disappeared, indicating that the delignification was successful. －１ Near and 1230 cm －１ A new peak is observed around this area. This is thought to be due to CO introduced by acetyl groups, and it is clear that acetylation occurred while delignifying by using acetic acid as a solvent.

[0168] Examples 2 to 9, Comparative Examples 1 and 2 Water-wet filter cakes were obtained in the same manner as in Example 1, except that the type and amount of catalyst, reaction temperature, and reaction time were changed as shown in the table below. The obtained filter cakes were subjected to the following X-ray diffraction measurement and solid １３The amount of cellulose crystals was measured by C-NMR measurement, and the lignin content and the degree of acetyl group substitution were measured by the following methods.

[0169] <Measurement of Lignin Amount> The amount of lignin in the obtained filter cake was measured by the following method. That is, approximately 20 mg of a dried sample of the filter cake was precisely weighed, and 0.3 mL of sulfuric acid with a concentration of 72% by mass was added and decomposed at 30°C for 60 minutes. 8.4 mL of pure water was added to the mixture, and the mixture was heated and decomposed at 120°C for 1 hour using an autoclave. The reaction product after the thermal decomposition was centrifuged (3500 rpm x 10 minutes) to separate the supernatant and precipitate. The precipitate was taken as lignin, washed with water, dried, and then weighed and expressed as a percentage (%) of the dry weight of the original biomass.

[0170] <Hemicellulose Content Measurement> The hemicellulose content in the obtained filtrate was measured using the following method. Specifically, approximately 20 mg of a dried sample of the filtrate was weighed, and 0.3 mL of 72% by mass sulfuric acid was added and decomposed at 30°C for 60 minutes. To this was added 8.4 mL of pure water, and the mixture was heated at 120°C for 1 hour using an autoclave. The reaction product after thermal decomposition was centrifuged (3500 rpm x 10 minutes) to separate the supernatant and precipitate. The resulting supernatant was neutralized by adding barium carbonate (the pH of the supernatant was adjusted to 6-8). The neutralized supernatant was then filtered through a 0.22 μm syringe filter (product name "FILTSTAR Syringe Filter", manufactured by Hawach Scientific) and analyzed by HPLC. The neutral sugar concentration was calculated using a previously prepared calibration curve. The neutral sugars glucose, mannose, xylose, galactose, and arabinose were quantified. Of these, mannose, xylose, galactose, and arabinose were considered to be monosaccharides derived from hemicellulose, and the amounts of these monosaccharides were converted into the amounts of polysaccharides, and the total was estimated as the amount of hemicellulose.

[0171] Measurement by HPLC was carried out under the following conditions: Apparatus: LC-4000 HPLC (manufactured by JASCO Corporation) Column: Aminex HPX-87P (300 x 7.8 mm) (manufactured by Bio-Rad Laboratories) Guard column: Micro-Guard Carbo-P Refill Cartridges (30 x 4.6 mm) (manufactured by Bio-Rad Laboratories) Column temperature: 85°C Mobile phase: water Mobile phase flow rate: 0.6 mL / min Detector: ELSD detector

[0172] <ATR-IR measurement, measurement of acetyl substitution degree> A small amount of the sample obtained by freeze-drying was subjected to ATR-IR measurement using FT / IR-4700 manufactured by JASCO Corporation. Cellulose acetates having various degrees of acetyl substitution were also subjected to ATR-IR measurement in the same manner. After baseline correction, the peaks at 1735 cm －１ The absorbance of the peak derived from the acetyl group near 1032 cm －１ The ratio of absorbance of the peaks around 1735 cm －１ / 1032cm －１ ) was calculated and plotted against the degree of substitution, a good correlation was obtained. －１ / 1032cm －１ Using the relational expression between the degree of acetyl group substitution and the Abs value of the sample obtained in the example, －１ / 1032cm －１ was measured and the degree of acetyl substitution was calculated.

[0173] <X-ray diffraction measurement> A small amount of the freeze-dried sample was subjected to X-ray diffraction measurement using a Malvern Panalytical benchtop X-ray diffractometer Aeris. The amount of cellulose crystals was estimated from the obtained X-ray diffraction pattern using the area method as follows. Peaks at 2θ: 14.5° (110 plane), 16.5° (110 plane), 20.7° (102 plane), 22.5° (200 plane), and 34.9° (004 plane) were set as diffractions derived from cellulose crystals, and peaks at 6° to 10° and 18.5° were set as peaks derived from amorphous regions and cellulose acetate. Peak separation was performed using the software of the X-ray diffractometer, and the amount of cellulose crystals was estimated according to the following formula. For Cellulose I, typical peaks can be observed at 2θ = 14.5°, 16.5°, and 22.5°. Amount of cellulose crystals = [total area of ​​diffraction peaks derived from cellulose crystals / total area] x 100 (%)

[0174] <Solid １３ C-NMR Measurement> A small amount of the sample obtained by freeze-drying was subjected to solid analysis using JNM-ECS400NR manufactured by JEOL Ltd. １３ C-NMR (CP / MAS) measurements were performed. The results are shown in Figure 2. For cellulose, two peaks derived from the C4 position were observed near 80 to 95 ppm. The peak on the low magnetic field side was derived from crystalline cellulose (referred to as "C4c"), and the peak on the high magnetic field side was derived from amorphous cellulose. After peak separation using a Lorentz function, the peak area of ​​C4c relative to the peak area of ​​the C1 position (near 100 to 110 ppm) was calculated, and this was used as the relative amount of crystalline cellulose.

[0175]

[0176] Table 1 shows that when a carboxylic acid is used as a solvent, the delignification and acylation reactions proceed without a catalyst. Furthermore, the use of a catalyst promotes delignification and increases the degree of acyl group substitution. Microscopic observation confirmed that the products of Examples 1 to 7 were fibrous. The hemicellulose content of Example 1 was 8.0 wt %, and the hemicellulose content of Example 4 was 11.1 wt %.

[0177] Example 10 The contents of the glass reactor after the reaction in Example 1 were removed and filtered using filter paper with a pore size of 5 μm. The filter cake was washed with acetic acid, and then acetic anhydride was added as an additional reaction solution at a ratio of 9.8 mmol per 1 g of wood flour (equivalent to dry weight), and the reaction was carried out at 60 ° C. for 2 hours. After cooling, the reaction product was removed from the glass reactor and filtered using filter paper with a pore size of 5 μm. The filter cake on the filter paper was washed sequentially with acetic acid, water, a 0.15% aqueous sodium bicarbonate solution, and water. This resulted in a water-wet filter cake. The obtained filter cake was measured for cellulose crystal content, lignin content, and degree of acetyl group substitution in the same manner as in Example 2.

[0178] Examples 11 and 12 The same procedures as in Example 10 were carried out except that the additional reaction solution was changed as shown in Table 2. In Example 12, acetic anhydride was added after the filter cake and toluene were mixed.

[0179] Comparative Example 1 A reaction product was obtained in the same manner as in Example 1, except that toluene was used instead of acetic acid as the solvent and the cleaning agent. The cellulose crystal content, lignin content, and acetyl group substitution degree of the obtained reaction product were measured in the same manner as in Example 10.

[0180] In Examples 1, 10, 11, and 12, it was found that delignification had progressed and acetylation had progressed while leaving cellulose crystals (as can be seen from the IR substitution degree). Furthermore, microscopic observation showed that the products of Examples 1, 10, 11, and 12 were fibrous.

[0181]

[0182] Example 13 A portion of the water-wet filter cake after washing obtained in Example 1 was collected and freeze-dried, and the solid content concentration of the filter cake was calculated based on the weight change before and after drying. Based on this solid content concentration, an amount of filter cake containing 0.3 g of solids was collected and water was added to obtain 100 g of a suspension. This suspension was subjected to a micronization treatment for 10 minutes or 60 minutes using a Hiscotron NS-50 manufactured by Microtec Nition Co., Ltd. at 45, to obtain an acylated cellulose dispersion. A scanning electron microscope photograph of the obtained acylated cellulose is shown in Figure 3. Before micronization, the majority of fibers were several tens of μm in width, but after 60 minutes of micronization, a fibrous material micronized to a width of 1 μm or less was obtained. It was also found that after 10 minutes of micronization, peeled sheets with a thickness on the order of nanometers were obtained. The photograph in Figure 3 before micronization (after reaction) corresponds to the scanning electron microscope photograph of the filter cake obtained in Example 1.

[0183] Example 14 The washed, water-wet filter cake obtained in Example 10 was subjected to a 60-minute micronization treatment in the same manner as in Example 13 to obtain an acylated cellulose dispersion. A scanning electron microscope photograph of the obtained acylated cellulose is shown in Figure 4. Before micronization, most fibers were several tens of μm wide, but after 60 minutes of micronization, a fibrous material was obtained whose width was much smaller than 1 μm, and which had been micronized to several tens of nm. The photograph in Figure 4 before micronization (after reaction) corresponds to the scanning electron microscope photograph of the filter cake obtained in Example 10.

[0184] Example 15: A cellulose acylate dispersion was obtained by pulverization treatment for 60 minutes in the same manner as in Example 13. The resulting cellulose acylate dispersion was diluted twice with water. The resulting diluted solution was then subjected to suction filtration using a membrane filter with a pore size of 0.45 μm. The residue on the filter was collected, pressed at 5 MPa, and dried at 105°C for 10 minutes to obtain a sheet (thickness: 25 μm). A photograph of the appearance of the resulting sheet is shown in Figure 5(a). Figure 5 shows that the resulting sheet is translucent.

[0185] (Tensile Strength Measurement) A dumbbell-shaped test piece was prepared from the sheet obtained in Example 15, and the tensile strength was measured using a small desktop tester EZ-SX50N manufactured by Shimadzu Corporation. As a result, the tensile strength was 38 MPa, which was 3.8 times higher than that of the sheet obtained in Comparative Example 3 described below. This is thought to be because, when subjected to the pulping treatment under the same conditions, the acylated cellulose of the present invention is more easily pulverized than commercially available pulp, and therefore, when pressed and dried, the fibers more easily interact with each other, forming a dense sheet.

[0186] Comparative Example 3: Commercially available softwood pulp was finely shredded and then immersed in water for 24 hours. It was then subjected to a pulp milling treatment for 60 minutes under the same conditions as in Example 15, and pressed and dried to obtain a sheet (thickness: 45 μm). A photograph of the appearance of the obtained sheet is shown in FIG. 5(b). As shown in FIG. 5, the obtained sheet was white and opaque. Furthermore, the tensile strength was measured using the same method as in Example 15. The measured tensile strength was 10 MPa, which was brittle and weak.

[0187] Comparative Example 4 A delignification reaction was carried out under the conditions shown in the following formula to obtain a precipitate.

[0188] The resulting precipitate was washed with water to obtain a wet solid (1). The water content of the wet solid (1) (weight excluding water: 0.125 g) was replaced with acetic acid, and in the presence of acetic acid (52 eq per 1 eq of cellulose), acetic anhydride in an amount equivalent to 30 eq per eq of cellulose in the wet solid (1) and 5 mol% scandium(III) trifluoromethanesulfonate were added, followed by a reaction at room temperature for 20 hours. As a result, a transparent viscous liquid was obtained. In other words, because a transparent viscous liquid was obtained by the delignification reaction of Ceder powder and the subsequent acetylation reaction with acetic anhydride, neither solid-liquid separable fibrous cellulose acetate nor cellulose crystals were obtained in Comparative Example 4, as in the Examples.

[0189] The resulting viscous liquid was washed with water and freeze-dried. The resulting product was subjected to ATR-IR measurement. Abs 1735 cm －１ / 1032cm －１Using the relationship between the degree of acetyl substitution and the Abs value of the above product, －１ / 1032cm －１ The degree of acetyl substitution of the product was 2.9. The proportion of lignin in the total product was 2% by weight or less.

[0190] Reference Example 1 X-ray diffraction was performed on commercially available microcrystalline cellulose (CEOLUS FD-F20 manufactured by Asahi Kasei Corporation). The results are shown in Figure 6 as Cellulose I. The data show the cellulose type I crystalline structure, with typical peaks observed at 2θ = 14.5°, 15.8°, and 22.3°.

[0191] Reference Example 2: Commercially available cellulose acetate (L-50, manufactured by Daicel Corporation) was deacetylated by stirring in a large excess of 1N aqueous sodium hydroxide solution at 30°C for 24 hours, followed by washing with water and drying to prepare regenerated cellulose, which was then subjected to X-ray diffraction analysis. The results are shown in Figure 6 as Cellulose II. The data show the cellulose type II crystalline structure, with typical peaks observed at 2θ = 11.6°, 19.8°, and 20.9°.

[0192] In summary, the configuration of the present disclosure and its variations are described below. [1] A method for producing a lignocellulose (A) and a cellulose derivative represented by the following formula (b): １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more), to form a compound having a repeating unit represented by formula (1), １A method for producing acylated cellulose, which obtains an acylated cellulose having a total degree of CO group substitution of 0.1 to 3 and a cellulose crystalline and / or cellulose triester crystalline structure. (The cellulose triester is preferably cellulose triacetate.) [2] A method for producing acylated cellulose according to [1], wherein the reaction in step (I) is carried out in a solvent containing (B) in a proportion of 1.3 to 30 parts by weight of (B) per part by weight of (A) (on a dry weight basis), the concentration of carboxylic acid (B) in the solvent is 30% by weight or more, and the content of a water-insoluble organic solvent in the solvent is 50% by weight or less (preferably 15% by weight or less, 10% by weight or less, 5% by weight or less, or 0% by weight or less). [3] The obtained acylated cellulose has a cellulose crystalline proportion of 30% or more or a solid state proportion of 30% or more as determined by X-ray diffraction. １３ [1] The method for producing acylated cellulose according to [1] or [2], wherein the proportion of cellulose crystals determined by C-NMR is 0.1 or more. [4] The method for producing acylated cellulose according to any one of [1] to [3], wherein the obtained acylated cellulose has a lignin content of 7% by weight or less. [5] The method for producing acylated cellulose according to any one of [1] to [4], wherein the reaction in step (I) is further carried out in the presence of a peroxide and / or peracid (C), and the amount of (C) is 0.03 to 0.7 mol per mol of (B). [6] The method for producing acylated cellulose according to any one of [1] to [5], wherein the reaction in step (I) is carried out in the presence of a peroxide and / or peracid (C) and an acid catalyst (D), and the amount of (D) is 0.003 to 0.3 mol per mol of (C). [7] The method for producing acylated cellulose according to any one of [1] to [6], wherein the reaction of the step (I) is further carried out in the presence of an acid catalyst (D), and the amount of the acid catalyst (D) is 0.0003 to 0.03 mol per 1 mol of the acid catalyst (B). [8] The method for producing acylated cellulose according to [7], wherein the acid catalyst (D) is a compound represented by formula (d-1). [9] A method for producing acylated cellulose according to [7], comprising the following steps (I) and (II): １ A method for producing acylated cellulose, which provides an acylated cellulose having a total degree of CO group substitution of 0.1 to 3. Step (I): Reacting lignocellulose (A) with a compound represented by the following formula (b) R１ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more) Step (II): In addition to the step (I), a step of reacting the solid content of the reaction solution of step (I) with the following acylating agent (B') in a proportion of 0.5 to 150 mmol per 1 g of lignocellulose (A) (converted to dry weight): Acylating agent (B'): at least one compound selected from a carboxylic acid represented by the following formula (b'), a halide of a carboxylic acid represented by the following formula (b'), an anhydride of a carboxylic acid represented by the following formula (b'), and a vinyl ester of a carboxylic acid represented by the following formula (b'): １ (COOH) ｍ (b') (wherein, R １ , m is the same as above)

[10] The method for producing acylated cellulose according to [9], wherein the reaction in step (II) is carried out in the presence of a solvent that is a non-solvent or a poor solvent for the acylated cellulose to be produced, and the amount of the solvent used is 1 to 40 parts by weight per part by weight of the residue.

[11] The method for producing acylated cellulose according to any one of [1] to

[10] , wherein one or more selected from carboxylic acid anhydride, formic acid, and sulfuric acid are not used in step (I).

[12] A method for producing acylated cellulose according to any one of [1] to

[10] , wherein the acylated cellulose has a repeating unit represented by formula (1), and R １ An acylated cellulose having a total degree of CO group substitution of 0.1 to 3 and a cellulose crystalline and / or cellulose triester crystalline structure. (The cellulose triester is preferably cellulose triacetate.)

[13] The acylated cellulose according to

[12] , having a lignin content of 7% by weight or less.

[14] The acylated cellulose according to

[12] or

[13] , which is fibrous and has an average aspect ratio (average fiber length / average fiber width) of 5 or more.

[15] The acylated cellulose according to

[12] or

[13] , having a cellulose crystalline content of 30% or more or a solid content of 30% or more as determined by X-ray diffraction. １３

[16] The acylated cellulose according to any one of

[12] to

[14] , having a ratio of cellulose crystals of 0.1 or more as determined by C-NMR.

[16] The acylated cellulose according to any one of

[12] to

[15] , having a degree of substitution of 0.5 to 1.4.

[17] A resin composition comprising the acylated cellulose according to any one of

[12] to

[16] and a resin component.

[18] A fiber-reinforced plastic comprising the acylated cellulose according to any one of

[12] to

[16] and a plastic component.

[19] A fiber-reinforced rubber comprising the acylated cellulose according to any one of

[12] to

[16] and a rubber component.

[20] A structure having a coating comprising the acylated cellulose according to any one of

[12] to

[16] .

[21] A sheet comprising the acylated cellulose according to any one of

[12] to

[16] .

[22] Acylated cellulose produced by the production method according to any one of [1] to

[11] , or the acylated cellulose according to any one of

[12] to

[16] .

[23] A resin composition comprising the acylated cellulose according to

[22] and a resin component.

[24] A fiber-reinforced plastic comprising the acylated cellulose according to

[22] and a plastic component.

[25] A fiber-reinforced rubber comprising the acylated cellulose according to

[22] and a rubber component.

[26] A structure having a coating comprising the acylated cellulose according to

[22] .

[27] A sheet comprising the acylated cellulose according to

[22] .

[28] A nanofiber or nanosheet comprising the acylated cellulose according to any one of

[12] to

[16] and

[22] .

[29] A composition comprising a lignocellulose (A) and a polymerizable compound represented by the following formula (b): R １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more), to form a compound having a repeating unit represented by formula (1), １

[30] A method for producing acylated cellulose nanofibers or cellulose nanosheets, which produces acylated cellulose nanofibers or cellulose nanosheets having a total degree of CO group substitution of 0.1 to 3 and one or more selected from a cellulose type I crystal structure and a cellulose triacetate type I crystal structure.

[30] A method for producing acylated cellulose nanofibers or cellulose nanosheets according to

[29] , wherein the reaction in step (I) is carried out in a solvent containing (B) in a proportion of 1.3 to 30 parts by weight per part by weight of (A) (in terms of dry weight), and the concentration of carboxylic acid (B) in the solvent is 30% by weight or more.

[31] The obtained acylated cellulose has a cellulose crystallinity of 30% or more by X-ray diffraction analysis or a solid state crystalline structure of 30% or more by X-ray diffraction analysis. １３

[32] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to any one of

[29] to

[31] , wherein the proportion of cellulose crystals determined by C-NMR is 0.1 or more.

[33] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to any one of

[29] to

[32] , wherein the acylated cellulose obtained has a lignin content of 7% by weight or less.

[34] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to any one of

[29] to

[32] , wherein the reaction in step (I) is further carried out in the presence of a peroxide and / or peracid (C), and the amount of (C) is 0.03 to 0.7 moles per mole of (B).

[34] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to any one of

[29] to

[33] , wherein the reaction in step (I) is carried out in the presence of a peroxide and / or peracid (C) and an acid catalyst (D), and the amount of (D) is 0.003 to 0.3 mol per mol of (C).

[35] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to any one of

[29] to

[34] , wherein the reaction in step (I) is further carried out in the presence of an acid catalyst (D), and the amount of (D) is 0.0003 to 0.03 mol per mol of (B).

[36] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to

[35] , wherein the acid catalyst (D) is a compound represented by formula (d-1).

[37] A method for producing an acylated cellulose nanofiber or cellulose nanosheet according to any one of

[29] to

[36] , comprising, in addition to step (I), step (II) of reacting the solid content of the reaction solution of step (I) with the following acylating agent (B') in a proportion of 0.5 to 150 mmol per 1 g of lignocellulose (A) (in terms of dry weight): acylating agent (B'): at least one compound R selected from a carboxylic acid represented by the following formula (b'), a halide of a carboxylic acid represented by the following formula (b'), an anhydride of a carboxylic acid represented by the following formula (b'), and a vinyl ester of a carboxylic acid represented by the following formula (b'): １ (COOH) ｍ (b') (wherein, R １, m is the same as above)

[38] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to

[37] , wherein the reaction in step (II) is carried out in the presence of a solvent that is a non-solvent or a poor solvent for the acylated cellulose produced, and the amount of the solvent used is 1 to 40 parts by weight per part by weight of the residue.

[39] The method for producing acylated cellulose nanofibers or cellulose nanosheets according to any one of

[29] to

[38] , wherein one or more selected from carboxylic acid anhydride, formic acid, and sulfuric acid are not used in step (I).

[40] A method for producing acylated cellulose nanofibers or cellulose nanosheets according to any one of

[29] to

[38] , wherein plant-derived biomass (A) and a cellulose derivative represented by the following formula (b) R １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more), in a ratio of 1.3 to 30 parts by weight of (B) per 1 part by weight of (A) (in terms of dry weight), to obtain a polymer having a repeating unit represented by formula (1), and R １ A method for producing acylated cellulose, which produces acylated cellulose having a total degree of CO group substitution of 0.1 to 3. (Note that the plant-derived biomass (A) may be lignocellulose (A).)

[41] A method for producing acylated cellulose according to

[40] , wherein the reaction in step (I) is carried out in a solvent containing a carboxylic acid (B), and the concentration of the carboxylic acid (B) in the solvent is 30% by weight or more.

[42] The obtained acylated cellulose has a cellulose crystal content of 30% or more or a solid content of 30% or more as determined by X-ray diffraction. １３

[40] or

[41] , wherein the proportion of cellulose crystals determined by C-NMR is 0.1 or more.

[43] The method for producing acylated cellulose according to any one of

[40] to

[42] , wherein the obtained acylated cellulose has a lignin content of 7% by weight or less.

[44] The method for producing acylated cellulose according to any one of

[40] to

[43] , wherein the reaction in step (I) is further carried out in the presence of a peroxide and / or peracid (C), and the amount of (C) is 0.03 to 0.7 mol per mol of (B).

[45] The method for producing acylated cellulose according to any one of

[40] to

[44] , wherein the reaction in step (I) is carried out in the presence of a peroxide and / or peracid (C) and an acid catalyst (D), and the amount of (D) is 0.003 to 0.3 mol per mol of (C).

[46] The method for producing acylated cellulose according to any one of

[40] to

[45] , wherein the reaction in step (I) is further carried out in the presence of an acid catalyst (D), and the amount of (D) is 0.0003 to 0.03 mol per 1 mol of (B).

[47] The method for producing acylated cellulose according to

[46] , wherein the acid catalyst (D) is a compound represented by formula (d-1).

[48] The method for producing acylated cellulose according to any one of

[40] to

[47] , further comprising, in addition to step (I), step (II) of reacting the solid content of the reaction solution in step (I) with the following acylating agent (B') in a proportion of 0.5 to 150 mmol per 1 g of plant-derived biomass (A) (in terms of dry weight): Acylating agent (B'): at least one compound selected from the group consisting of a carboxylic acid represented by the following formula (b'), a halide of a carboxylic acid represented by the following formula (b'), an anhydride of a carboxylic acid represented by the following formula (b'), and a vinyl ester of a carboxylic acid represented by the following formula (b'): １ (COOH) ｍ (b') (wherein, R １

[49] The method for producing an acylated cellulose according to

[48] , wherein the reaction in step (II) is carried out in the presence of a solvent that is a non-solvent or a poor solvent for the acylated cellulose to be produced, and the amount of the solvent used is 1 to 40 parts by weight per part by weight of the residue.

[50] A method for producing an acylated cellulose according to

[48] , wherein the acylated cellulose has a repeating unit represented by formula (1), and R １An acylated cellulose having a total degree of CO group substitution of 0.1 to 3.

[51] The acylated cellulose according to

[50] , which has a lignin content of 7% by weight or less.

[52] The acylated cellulose according to

[50] or

[51] , which is fibrous and has an average aspect ratio (average fiber length / average fiber width) of 5 or more.

[53] The acylated cellulose according to

[50] or

[51] , which has a cellulose crystallinity of 30% or more or a solid state crystalline cellulose content of 30% or more as determined by X-ray diffraction. １３

[50] An acylated cellulose according to any one of

[50] to

[52] , having a cellulose crystallinity of 0.1 or more as determined by C-NMR.

[54] A resin composition comprising the acylated cellulose according to any one of

[50] to

[53] and a resin component.

[55] A fiber-reinforced plastic comprising the acylated cellulose according to any one of

[50] to

[53] and a plastic component.

[56] A fiber-reinforced rubber comprising the acylated cellulose according to any one of

[50] to

[53] and a rubber component.

[57] A structure having a coating comprising the acylated cellulose according to any one of

[50] to

[53] .

[58] A sheet comprising the acylated cellulose according to any one of

[50] to

[53] .

[0193] According to the manufacturing method disclosed herein, acylated cellulose can be obtained from lignocellulose in a single reaction step. The acylated cellulose thus obtained retains the properties of cellulose crystals (e.g., high strength, high modulus, etc.) while also exhibiting newly acquired water resistance and easy miscibility with hydrophobic materials. Therefore, when added to plastics or rubber, it is easily mixed, resulting in fiber-reinforced plastics or fiber-reinforced rubbers with high strength, high modulus, and excellent water resistance. Furthermore, by coating a structure with a film containing the acylated cellulose, a structure with high strength, high modulus, and excellent water resistance can be obtained. Furthermore, by incorporating the acylated cellulose into a sheet, a sheet with high strength, high modulus, and excellent water resistance can be obtained.

Claims

1. Lignocellulose (A) and the following formula (b) R １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more), to form a compound represented by the following formula (1): (In the formula, R １１ ~R １３ are the same or different and are a hydrogen atom or R １ R represents a CO group. １ R is the same as above), １ A method for producing acylated cellulose, which provides acylated cellulose having a total degree of CO group substitution of 0.1 to 3 and a cellulose crystalline and / or cellulose triester crystalline structure.

2. A method for producing acylated cellulose according to claim 1, wherein the reaction in step (I) is carried out in a solvent containing (B) in a proportion of 1.3 to 30 parts by weight of (B) per part by weight of (A) (in dry weight terms), the concentration of carboxylic acid (B) in the solvent is 30% by weight or more, and the content of a water-insoluble organic solvent in the solvent is 50% by weight or less.

3. The acylated cellulose obtained has a cellulose crystal content of 30% or more by X-ray diffraction method or a solid １３ The method for producing acylated cellulose according to claim 1 or 2, wherein the proportion of cellulose crystals determined by C-NMR is 0.1 or more.

4. A method for producing acylated cellulose according to claim 1 or 2, wherein the acylated cellulose obtained has a lignin content of 7% by weight or less.

5. A method for producing acylated cellulose according to claim 1 or 2, wherein the reaction in step (I) is further carried out in the presence of a peroxide and / or peracid (C), and the amount of (C) is 0.03 to 0.7 moles per mole of (B).

6. The method for producing acylated cellulose according to claim 1 or 2, wherein the reaction in step (I) is carried out in the presence of a peroxide and / or peracid (C) and an acid catalyst (D), and the amount of (D) is 0.003 to 0.3 moles per mole of (C).

7. The method for producing acylated cellulose according to claim 1 or 2, wherein the reaction in step (I) is further carried out in the presence of an acid catalyst (D), and the amount of (D) is 0.0003 to 0.03 moles per mole of (B).

8. The method for producing acylated cellulose according to claim 7, wherein the acid catalyst (D) is a compound represented by the following formula (d-1): (In the above formula, ring Z represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and R ２ represents a divalent hydrocarbon group; t represents an integer of 0 or more; and n represents an integer of 1 or more.

9. A compound represented by the following formula (1), comprising the following steps (I) and (II): (In the formula, R １１ ~R １３ are the same or different and are a hydrogen atom or R １ R represents a CO group. １ R is the same as above), １ A method for producing acylated cellulose, which provides an acylated cellulose having a total degree of CO group substitution of 0.1 to 3. Step (I): Reacting lignocellulose (A) with a compound represented by the following formula (b) R １ (COOH) ｍ (b) (wherein, R １ represents a hydrocarbon group, and m represents an integer of 1 or more) Step (II): In addition to the step (I), a step of reacting the solid content of the reaction solution of step (I) with the following acylating agent (B') in a proportion of 0.5 to 150 mmol per 1 g of lignocellulose (A) (converted to dry weight), wherein acylating agent (B'): at least one compound selected from a carboxylic acid represented by the following formula (b'), a halide of a carboxylic acid represented by the following formula (b'), an anhydride of a carboxylic acid represented by the following formula (b'), and a vinyl ester of a carboxylic acid represented by the following formula (b'): １ (COOH) ｍ (b') (wherein, R １ , m is the same as above) 10. The method for producing acylated cellulose according to claim 9, wherein the reaction in step (II) is carried out in the presence of a solvent that is a non-solvent or a poor solvent for the acylated cellulose produced, and the amount of the solvent used is 1 to 40 parts by weight per part by weight of the residue.

11. A method for producing acylated cellulose according to claim 1 or 2, wherein one or more selected from carboxylic acid anhydride, formic acid, and sulfuric acid are not used in step (I).

12. The following formula (1) (In the formula, R １１ ~R １３ are the same or different and are a hydrogen atom or R １ represents a CO group, and the R １ represents a monovalent hydrocarbon group), and R １ An acylated cellulose having a total degree of CO group substitution of 0.1 to 3 and having a cellulose crystalline and / or cellulose triester crystalline structure.

13. The acylated cellulose according to claim 12, having a lignin content of 7% by weight or less.

14. The acylated cellulose according to claim 12, which is fibrous and has an average aspect ratio (average fiber length / average fiber width) of 5 or more.

15. The proportion of cellulose crystals by X-ray diffraction method is 30% or more or solid １３ The acylated cellulose according to claim 12, having a cellulose crystallinity of 0.1 or more as determined by C-NMR.

16. The acylated cellulose according to any one of claims 12 to 15, having a degree of substitution of 0.5 to 1.

4.

17. A resin composition comprising the acylated cellulose according to any one of claims 12 to 16 and a resin component.

18. A fiber-reinforced plastic comprising the acylated cellulose according to any one of claims 12 to 16 and a plastic component.

19. A fiber-reinforced rubber comprising the acylated cellulose according to any one of claims 12 to 16 and a rubber component.

20. A structure provided with a coating comprising the acylated cellulose according to any one of claims 12 to 16.

21. A sheet comprising the acylated cellulose according to any one of claims 12 to 16.

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