Method for producing amino group-containing cellulose

Abstract

To provide a method for efficiently producing amino group-containing cellulose from a biomass raw material containing cellulose.　A method for producing amino group-containing cellulose which includes a mixing step for mixing a biomass raw material containing cellulose and an amine-based compound in the presence of a catalyst.

Description

Method for producing amino group-containing cellulose

[0001] The present disclosure relates to a method for producing amino group-containing cellulose.

[0002] In recent years, due to the increasing interest in environmental issues, the development of materials derived from biomass resources is required instead of materials derived from petroleum resources. In particular, the use of lignocellulosic biomass, which does not compete with food and does not increase carbon dioxide in the atmosphere, is desired.

[0003] The main component of lignocellulosic biomass is a natural polymer mixture called lignocellulose. Lignocellulose forms a strong higher-order structure in which cellulose, hemicellulose, and lignin are intricately intertwined. Specifically, in lignocellulose, cellulose, which is a linear polymer, forms a crystal structure through intramolecular and intermolecular hydrogen bonds to constitute strong microfibrils. Hemicellulose such as xylan and glucomannan is intertwined with this, and furthermore, lignin, which is an irregular aromatic polymer, fills the voids in the matrix of these polysaccharides to form a strong complex. Therefore, lignocellulose as a whole does not dissolve in solvents such as water and organic solvents under mild conditions. This makes it difficult to directly convert the functional groups of the hydroxyl groups in lignocellulose. In order to dissolve the entire lignocellulose in these solvents, a pretreatment for physically destroying the plant cell wall by grinding treatment such as ball milling or a pretreatment for separating cell wall components by a high-temperature reaction in a solvent containing a catalyst is required. Since the energy and cost required for grinding treatment and high-temperature reaction are large, it has been a major problem in the utilization of lignocellulosic biomass. In addition, changes in the molecular structure of lignocellulose due to pretreatment also become a problem.

[0004] Thus, conventionally, in order to dissolve lignocellulose, studies have been made to dissolve lignocellulose in a solvent by chemical decomposition at high temperature, mechanical treatment, etc.

[0005] For example, Patent Document 1 (Japanese Patent No. 3155603) discloses a method for producing a liquefied solution of lignocellulose by heating lignocellulose materials such as wood in the presence of an acid catalyst, a cyclic ester, and a polyhydric alcohol. This method is a wood liquefaction method that promotes the acid decomposition of wood in chemicals, and requires the use of an acid catalyst such as sulfuric acid and a polyhydric alcohol-based chemical such as polyethylene glycol, as well as heating to a reaction temperature of about 150°C. Furthermore, the lignocellulose obtained by this method has a low molecular weight.

[0006] Japanese Patent Publication No. 3155603, Japanese Unexamined Patent Publication No. 2024-128845, Japanese Unexamined Patent Publication No. 2009-247981

[0007] On the other hand, the introduction of nitrogen atoms into cellulose obtained from biomass and its application to various uses is being considered. For example, Patent Document 2 (Japanese Patent Application Publication No. 2024-128845) discloses a technology relating to a peptidoglycan adsorbent comprising cellulose nanofibers having cationic groups containing nitrogen atoms.

[0008] Furthermore, for example, Patent Document 3 (Japanese Patent Application Publication No. 2009-247981) discloses a technology relating to an adsorbent characterized in that iminodiacetic acid or dialkylamine is bonded to cellulose contained in a substrate as a functional group for adsorbing noble metals, the degree of crystallinity of the cellulose is approximately 70% or less, and the substrate contains an appropriate amount of hemicellulose and / or lignin.

[0009] However, in conventional technology, when producing amino group-containing cellulose from biomass raw materials containing cellulose, it is difficult to efficiently introduce amino groups into the cellulose contained in the biomass raw materials, as it requires multi-stage processing of the biomass raw materials or the introduction of linker groups between the cellulose and the amino groups.

[0010] Furthermore, as mentioned above, lignocellulose forms a robust higher-order structure in which cellulose, hemicellulose, and lignin are intricately intertwined. For this reason, especially with regard to biomass raw materials containing lignocellulose, there are currently no practical technologies to efficiently introduce amino groups into the cellulose contained in the biomass raw materials.

[0011] The primary objective of this disclosure is to provide a method for efficiently producing amino group-containing cellulose from biomass raw materials including cellulose.

[0012] The inventors of this disclosure diligently conducted research to solve the above-mentioned problems. As a result, they found that when a biomass raw material containing cellulose is mixed with an amine compound in the presence of a catalyst, amino group-containing cellulose is efficiently produced. Furthermore, the inventors of this disclosure also found that amino group-containing cellulose can be efficiently produced even when the biomass raw material contains lignocellulose.

[0013] This disclosure is the result of further consideration based on the aforementioned findings. Specifically, this disclosure provides inventions in the following embodiments.

[0014] Item 1. A method for producing amino group-containing cellulose, comprising a mixing step of mixing a biomass raw material containing cellulose with an amine compound in the presence of a catalyst. Item 2. The method for producing amino group-containing cellulose according to Item 1, wherein the catalyst includes a metal catalyst. Item 3. The method for producing amino group-containing cellulose according to Item 2, wherein the metal catalyst is at least one selected from the group consisting of iridium-based catalysts, iron-based catalysts, ruthenium-based catalysts, palladium-based catalysts, cobalt-based catalysts, nickel-based catalysts, rhodium-based catalysts, platinum-based catalysts, gold-based catalysts, osmium-based catalysts, manganese-based catalysts, chromium-based catalysts, copper-based catalysts, rhenium-based catalysts, and molybdenum-based catalysts. Item 4. The method for producing amino group-containing cellulose according to any one of Items 1 to 3, wherein the biomass raw material is a biomass raw material containing lignocellulose. Item 5. The method for producing amino group-containing cellulose according to any one of Items 1 to 4, wherein the mixing step is carried out in the presence of a solvent. Item 6. The method for producing amino group-containing cellulose according to claim 5, wherein the solvent is at least one of water and an organic solvent that does not have hydroxyl groups. Claim 7. The method for producing amino group-containing cellulose according to claim 5 or claim 6, wherein the catalyst is dissolved in the solvent. Claim 8. The method for producing amino group-containing cellulose according to any one of claims 1 to 7, wherein the mixing ratio of the amine compound with respect to 1 part by mass of the cellulose is 0.001 parts by mass or more and 1000 parts by mass or less. Claim 9. The method for producing amino group-containing cellulose according to any one of claims 1 to 8, wherein the mixing ratio of the catalyst with respect to 1 mole of hydroxyl groups contained in the cellulose is 0.0001 moles or more and 0.5 moles or less. Claim 10. The method for producing amino group-containing cellulose according to any one of claims 1 to 9, wherein in the mixing step, a basic compound is further mixed. Claim 11. The method for producing amino group-containing cellulose according to any one of claims 1 to 10, wherein the mixing temperature in the mixing step is 50°C or more and 200°C or less. Claim 12. A method for producing amino group-containing cellulose according to any one of claims 1 to 11, wherein the mixture obtained in the mixing step is subjected to one or more treatments selected from the group consisting of centrifugation, filtration, extraction, and washing.

[0015] This disclosure provides a method for efficiently producing amino group-containing cellulose from biomass raw materials including cellulose.

[0016] Furthermore, according to this disclosure, even if the biomass raw material contains lignocellulose, a method for efficiently producing amino group-containing cellulose from a cellulose-containing biomass raw material can be provided.

[0017] These are images of the cedar wood powder used as a biomass raw material, the dried solids obtained in Comparative Example 4 and Example 10, observed using a stereomicroscope and a benchtop scanning electron microscope, respectively. These are photographs of the freeze-dried solids of Comparative Example 4 and Example 10, and the suspensions obtained when evaluating the dispersibility of the cedar wood powder in water. This is a SEM image obtained by observing the dried solid obtained in Example 10 using a benchtop scanning electron microscope, and the measured values ​​of the width of the obtained amino group-containing cellulose fibers and the thickness of the sheet are indicated.

[0018] Each configuration and its combination in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments.

[0019] In the numerical ranges described in stages in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Alternatively, the upper and lower limits, upper and lower limits, or lower and lower limits described separately may be combined to form numerical ranges. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples.

[0020] [Method for Producing Amino Group-Containing Cellulose] The method for producing amino group-containing cellulose according to this disclosure is characterized by including a mixing step of mixing a biomass raw material containing cellulose with an amine compound in the presence of a catalyst. By having this feature, the method for producing amino group-containing cellulose according to this disclosure exhibits the excellent effect of efficiently producing amino group-containing cellulose from a biomass raw material containing cellulose, even if the biomass raw material contains lignocellulose. The disclosure will be described in detail below.

[0021] In the method for producing amino group-containing cellulose according to this disclosure, the biomass raw material used may or may not contain lignocellulose, as long as it contains cellulose. Furthermore, the biomass raw material containing cellulose may consist solely of cellulose, or it may contain components other than cellulose (e.g., lignin, hemicellulose, etc.). In other words, the biomass raw material containing cellulose may consist substantially solely of cellulose, or it may be biomass containing lignocellulose, such as the woody biomass described later.

[0022] Examples of biomass raw materials that consist substantially solely of cellulose include highly refined cellulose such as microcrystalline cellulose (MCC) and alpha-cellulose. Microcrystalline cellulose is used, for example, as a food additive, pharmaceutical, cosmetic, and industrial material. In food grade, it is known as E460 and is used as a thickener and stabilizer. Alpha-cellulose is a high-purity cellulose used in the manufacture of paper and textile products, and has relatively high chemical resistance and excellent processability. It should be noted that when a biomass raw material is said to consist substantially solely of cellulose, it means that the cellulose content in the biomass raw material is, for example, 95% by mass or more, preferably 98% by mass or more, more preferably 99% by mass or more, and may be 100% by mass.

[0023] There are no particular limitations on the biomass raw materials containing lignocellulose; woody biomass such as broad-leaved trees (eucalyptus, etc.) and coniferous trees (cedar, cypress, etc.), and herbaceous biomass such as rice straw and wheat bran are appropriately selected and used. Biomass raw materials containing lignocellulose include various materials such as wood flour, wood fibers, crushed wood such as wood chips and veneer scraps, plant fiber such as straw and rice husks, pulp such as GP (ground pulp) and TMP (thermomechanical pulp), and paper such as recycled paper, and any of the materials that have been conventionally used in this field can be used. Here, lignocellulose refers to a mixture of natural polymers mainly consisting of cellulose, hemicellulose, and lignin. The content of cellulose, hemicellulose, and lignin will differ depending on the type of biomass selected, but the composition is not particularly limited in the manufacturing method of this disclosure. The cellulose content in the biomass raw material containing lignocellulose is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and preferably 80% by mass or more, 85% by mass or more, and so on.

[0024] The biomass raw material used in the manufacturing method of this disclosure may be one type or two or more types.

[0025] The biomass raw material used in the manufacturing method of this disclosure preferably includes a biomass raw material containing lignocellulose, and more preferably includes woody biomass.

[0026] The amine compound is not particularly limited as long as it is an amine compound that can substitute for the hydroxyl group contained in cellulose, and primary amines, secondary amines, and ammonia are preferred. Specific examples of amine compounds include primary amines such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, decylamine, dodecylamine, cyclopentylamine, cyclohexylamine, 1-adamantylamine, benzylamine, phenethylamine, aniline, toluidine, and 1-naphthylamine; linear secondary amines such as dimethylamine, diethylamine, dipropylamine, dicyclohexylamine, dibenzylamine, N-methylbenzylamine, and N-methylaniline; and cyclic secondary amines such as pyrrolidine, piperidine, and morpholine. Among these, secondary amines such as dimethylamine, diethylamine, and pyrrolidine are particularly preferred.

[0027] The amine compound used in the manufacturing method of this disclosure may be one type or two or more types.

[0028] The mixing ratio of the amine compound to 1 part by mass of cellulose is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, even more preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more. Also, it is preferably 1000 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. The preferred range is 0.001 to 1000 parts by mass, 0.001 to 5 Examples of the amounts include 0 parts by mass, 0.001 to 20 parts by mass, 0.001 to 10 parts by mass, 0.01 to 1000 parts by mass, 0.01 to 50 parts by mass, 0.01 to 20 parts by mass, 0.01 to 10 parts by mass, 0.1 to 1000 parts by mass, 0.1 to 50 parts by mass, 0.1 to 20 parts by mass, 0.1 to 10 parts by mass, 1 to 1000 parts by mass, 1 to 50 parts by mass, 1 to 20 parts by mass, 1 to 10 parts by mass, 2 to 1000 parts by mass, 2 to 50 parts by mass, 2 to 20 parts by mass, 2 to 10 parts by mass, 5 to 1000 parts by mass, 5 to 50 parts by mass, 5 to 20 parts by mass, and 5 to 10 parts by mass. By adjusting the mixing ratio of the amine compound, the rate of amination of the resulting aminated cellulose can be adjusted. For example, increasing the mixing ratio of the amine compound yields aminated cellulose with a high degree of amino group substitution.

[0029] In the manufacturing method of this disclosure, the catalyst is a compound that promotes the reaction (amination reaction) between a biomass raw material containing cellulose and an amine compound, and more specifically, is a compound that promotes a chemical reaction in which hydroxyl groups contained in cellulose are replaced with amino groups (derived from the amine compound).

[0030] From the viewpoint of more favorably exhibiting the effects of the invention disclosed herein, the catalyst preferably includes a metal catalyst. A metal catalyst is a catalyst composed of a compound containing a metal. Preferred metal catalysts include iridium-based catalysts, iron-based catalysts, ruthenium-based catalysts, palladium-based catalysts, cobalt-based catalysts, nickel-based catalysts, rhodium-based catalysts, platinum-based catalysts, gold-based catalysts, osmium-based catalysts, manganese-based catalysts, chromium-based catalysts, copper-based catalysts, rhenium-based catalysts, and molybdenum-based catalysts. Among these, iridium-based catalysts and iron-based catalysts are preferred, and iridium-based catalysts are even more preferred.

[0031] Examples of iridium-based catalysts include iridium complexes having phosphine ligands (e.g., binaphthylphosphine ligands), chelate ligands, pincer-type ligands (CNN, POCOP, PNP, etc.), strongly electron-donating ligands such as cyclopentadienyls, nitrogen-containing heterocyclic carbene ligands, pyridine ring-containing (pyridyl, polypyridyl) ligands, bisimine ligands, cyclooctadiene ligands, carbonyl ligands, sulfur-containing ligands, and Schiff base ligands. Preferred iridium-based catalysts include compounds represented by the following formulas (1) to (3), and [Cp * IrCl2]2, [Cp * Examples include IrI2]2.

[0032]

[0033] In formula (1), R is an aliphatic group or an aromatic group. Examples of aliphatic groups include alkyl groups having 1 to 20 carbon atoms, which may have substituents such as methyl, ethyl, isopropyl, and benzyl groups. Examples of substituents include aryl, carbonyl, carboxyl, amino, haloalkyl, alkoxy, alkyne, alkene, alkane, amide, halogen, acyl, ether, sulfur-based, silyl, hydroxyl, carbamoyl, and imino groups. Examples of aromatic groups include aryl groups having 3 to 14 carbon atoms, such as phenyl, pyridyl, naphthyl, anthranyl, imidazolyl, and pyrrolyl groups.

[0034]

[0035] In formula (2), R is an aliphatic group or an aromatic group. Examples of the aliphatic group include an alkyl group having 1 to 20 carbon atoms which may have substituents such as a methyl group, an ethyl group, an isopropyl group, a benzyl group, etc. Examples of the substituents include an aryl group, a carbonyl group, a carboxy group, an amino group, a haloalkyl group, an alkoxy group, an alkyne group, an alkene group, an alkane group, an amide group, a halogen group, an acyl group, an ether group, a sulfur-based group, a silyl group, a hydroxy group, a carbamoyl group, an imino group, etc. Examples of the aromatic group include an aryl group having 3 to 14 carbon atoms such as a phenyl group, a pyridyl group, a naphthyl group, an anthranyl group, an imidazolyl group, a pyrrolyl group, etc.

[0036]

[0037] In formula (3), R is an aliphatic group or an aromatic group. Examples of the aliphatic group include an alkyl group having 1 to 20 carbon atoms which may have substituents such as a methyl group, an ethyl group, an isopropyl group, a benzyl group, etc. Examples of the substituents include an aryl group, a carbonyl group, a carboxy group, an amino group, a haloalkyl group, an alkoxy group, an alkyne group, an alkene group, an alkane group, an amide group, a halogen group, an acyl group, an ether group, a sulfur-based group, a silyl group, a hydroxy group, a carbamoyl group, an imino group, etc. Examples of the aromatic group include an aryl group having 3 to 14 carbon atoms such as a phenyl group, a pyridyl group, a naphthyl group, an anthranyl group, an imidazolyl group, a pyrrolyl group, etc.

[0038] Specific examples of the preferred iridium-based catalysts include compounds represented by the following formula (A), the following formula (B), and the following formula (C).

[0039]

[0040] In addition, specific examples of the preferred iridium-based catalysts also include compounds containing the structure represented by the following formula (D).

[0041]

[0042] In formula (D), each R is independently an aliphatic group or an aromatic group. Examples of the aliphatic group include an alkyl group having 1 to 20 carbon atoms which may have substituents such as a methyl group, an ethyl group, an isopropyl group, a benzyl group, etc. Examples of the substituents include an aryl group, a carbonyl group, a carboxy group, an amino group, a haloalkyl group, an alkoxy group, an alkyne group, an alkene group, an alkane group, an amide group, a halogen group, an acyl group, an ether group, a sulfur-based group, a silyl group, a hydroxy group, a carbamoyl group, an imino group, etc. Examples of the aromatic group include an aryl group having 3 to 14 carbon atoms such as a phenyl group, a pyridyl group, a naphthyl group, an anthranyl group, an imidazolyl group, a pyrrolyl group, etc.

[0043] Examples of the iron-based catalyst include an iron complex having a phosphine ligand (e.g., a binaphthylphosphine ligand), a chelate-type ligand, a pincer-type (CNN, POCOP, PNP, etc.) ligand, a ligand showing strong electron-donating property such as cyclopentadienyls, a nitrogen-containing heterocyclic carbene ligand, a ligand having a pyridine ring (pyridyl, polypyridyl), a bisimine ligand, a cyclooctadiene ligand, a carbonyl ligand, a sulfur-containing ligand, a Schiff base ligand. Specific examples of the iron-based catalyst include a compound containing a structure represented by the following formula (4).

[0044]

[0045] In the above formula (4), each R is independently an aliphatic group or an aromatic group. Examples of the aliphatic group include an alkyl group having 1 to 20 carbon atoms which may have substituents such as a methyl group, an ethyl group, an isopropyl group, a benzyl group, etc. Examples of the substituents include an aryl group, a carbonyl group, a carboxy group, an amino group, a haloalkyl group, an alkoxy group, an alkyne group, an alkene group, an alkane group, an amide group, a halogen group, an acyl group, an ether group, a sulfur-based group, a silyl group, a hydroxy group, a carbamoyl group, an imino group, etc. Examples of the aromatic group include an aryl group having 3 to 14 carbon atoms such as a phenyl group, a pyridyl group, a naphthyl group, an anthranyl group, an imidazolyl group, a pyrrolyl group, etc.

[0046] Furthermore, examples of ruthenium catalysts include ruthenium complexes having phosphine ligands (e.g., binaphthylphosphine ligands), chelate ligands, pincer-type ligands (CNN, POCOP, PNP, etc.), strongly electron-donating ligands such as cyclopentadienyls, nitrogen-containing heterocyclic carbene ligands, pyridine ring-containing (pyridyl, polypyridyl) ligands, bisumine ligands, cyclooctadiene ligands, carbonyl ligands, sulfur-containing ligands, and Schiff base ligands. Specific examples of preferred ruthenium catalysts include compounds containing the structure represented by the following formulas: RuH2(PPh3)4, RuCl2(PPh3)3, Ru3(CO) 12 Examples include the following.

[0047]

[0048] In the above formula for the ruthenium catalyst, R is independently either an aliphatic group or an aromatic group. Examples of aliphatic groups include alkyl groups having 1 to 20 carbon atoms, which may have substituents such as methyl, ethyl, isopropyl, and benzyl groups. Examples of substituents include aryl, carbonyl, carboxyl, amino, haloalkyl, alkoxy, alkyne, alkene, alkane, amide, halogen, acyl, ether, sulfur-based, silyl, hydroxyl, carbamoyl, and imino groups. Examples of aromatic groups include aryl groups having 3 to 14 carbon atoms, such as phenyl, pyridyl, naphthyl, anthranyl, imidazolyl, and pyrrolyl groups.

[0049] Furthermore, examples of palladium-based catalysts, cobalt-based catalysts, nickel-based catalysts, rhodium-based catalysts, platinum-based catalysts, gold-based catalysts, osmium-based catalysts, manganese-based catalysts, chromium-based catalysts, copper-based catalysts, rhenium-based catalysts, and molybdenum-based catalysts include phosphine ligands (e.g., binaphthylphosphine ligands), chelate-type ligands, pincer-type ligands (CNN, POCOP, PNP, etc.), strongly electron-donating ligands such as cyclopentadienyls, nitrogen-containing heterocyclic carbene ligands, pyridine ring-containing (pyridyl, polypyridyl) ligands, bisimine ligands, cyclooctadiene ligands, carbonyl ligands, sulfur-containing ligands, and Schiff base ligands, as well as palladium complexes, cobalt complexes, nickel complexes, rhodium complexes, platinum complexes, gold complexes, osmium complexes, manganese complexes, chromium complexes, copper complexes, rhenium complexes, and molybdenum complexes, respectively. Examples of cobalt-based catalysts include cobalt complexes having porphyrin ligands. Examples of nickel-based catalysts include nickel complexes having acetylacetonate ligands. Specific examples of palladium-based catalysts include Pd(OAc)2.

[0050] The catalyst used in the manufacturing method of this disclosure may be one type or two or more types.

[0051] From the viewpoint of more effectively exhibiting the effects of the invention disclosed herein, it is preferable that the catalyst is dissolved in the solvent described later. That is, it is preferable that the catalyst is dissolved in the solvent during the mixing step.

[0052] In the manufacturing method of the present disclosure, the mixing ratio of the catalyst to 1 mole of hydroxyl groups contained in cellulose is preferably 0.0001 moles or more, more preferably 0.001 moles or more, even more preferably 0.01 moles or more, and also preferably 0.5 moles or less, more preferably 0.1 moles or less. Preferred ranges include 0.0001 to 0.5 moles, 0.0001 to 0.1 moles, 0.001 to 0.5 moles, 0.001 to 0.1 moles, 0.01 to 0.5 moles, and 0.01 to 0.1 moles.

[0053] Furthermore, in the manufacturing method of the present disclosure, the mixing ratio of the catalyst to 1 g of biomass raw material containing cellulose is preferably 0.001 moles or more, more preferably 0.01 moles or more, and also preferably 5 moles or less, more preferably 1 mole or less, and even more preferably 0.1 moles or less. Preferred ranges include 0.001 to 5 moles, 0.001 to 1 mole, 0.001 to 0.1 moles, 0.01 to 5 moles, 0.01 to 1 mole, and 0.01 to 0.1 moles.

[0054] In the manufacturing method of this disclosure, the mixing step (a step of mixing a biomass raw material containing cellulose with an amine compound in the presence of a catalyst) may be carried out in the presence of a solvent or without a solvent. From the viewpoint of more favorably exhibiting the effects of the invention of this disclosure, it is preferable to carry out the mixing step in the presence of a solvent.

[0055] Suitable solvents include water and organic solvents that do not have hydroxyl groups. Of these, water is preferred as the solvent. Suitable organic solvents that do not have hydroxyl groups include alkane solvents (e.g., hexane, pentane, isooctane), halogenated hydrocarbons (chloroform, dichloromethane (methylenedichloride), carbon tetrachloride, etc.), ethers (diethyl ether, tetrahydrofuran (THF), dibenzyl ether, etc.), ketones (acetone, methyl ethyl ketone (MEK), cyclohexanone, etc.), esters (ethyl acetate, methyl acetate, butyl acetate, etc.), aromatic hydrocarbons (aromatic hydrocarbon compounds having monocyclic or fused rings, such as alkylbenzenes, dialkylbenzenes, and aromatic hydrocarbon mixed solvents; preferred specific examples include toluene, xylene, and styrene), and amide solvents (N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), N-methylpyrrolidone, pyridine, etc.).

[0056] When a solvent is used in the manufacturing method of this disclosure, only one type of solvent may be used, or two or more types may be used.

[0057] When a solvent is used in the manufacturing method of this disclosure, the amount of solvent used is not particularly limited, but from the viewpoint of dissolving the catalyst in the solvent and allowing the amination reaction to proceed, for example, about 10 to 100 parts by mass per 1 part by mass of cellulose is recommended.

[0058] From the viewpoint of more favorably exhibiting the effects of the present invention, it is preferable to further mix a basic compound in the mixing step. That is, it is preferable that the mixing step involves mixing the biomass raw material containing cellulose with the amine compound in the presence of a catalyst and a basic compound. Furthermore, when a solvent is used in the mixing step, it is preferable to mix the biomass raw material containing cellulose with the amine compound in the presence of a catalyst, a basic compound and a solvent, and it is even more preferable that the catalyst is dissolved in the solvent.

[0059] The basic compound is not particularly limited as long as it promotes the amination reaction of cellulose or the dissolution of cellulose, and examples include inorganic salt compounds. Examples of inorganic salt compounds include sodium hydroxide, hydroxides (lithium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, etc.), chlorides (sodium chloride, lithium chloride, potassium chloride, ammonium chloride, etc.), sulfates, carbonates, nitrates, phosphates, and sodium thiosulfate.

[0060] When a basic compound is used in the manufacturing method of this disclosure, only one basic compound may be used, or two or more basic compounds may be used.

[0061] In the manufacturing method of this disclosure, when a basic compound is used, the concentration (mass%) of the basic compound in 100% by mass of the solution obtained by removing the solid content from the mixed solution (biomass raw material containing cellulose, amine compound, catalyst, basic compound, solvent mixed as needed) subjected to the reaction in the mixing step is preferably 0.1% by mass or more, more preferably 1% by mass or more, and also preferably 30% by mass or less, more preferably 15% by mass or less. Preferred ranges include 0.1 to 30% by mass, 0.1 to 15% by mass, 1 to 30% by mass, and 1 to 15% by mass.

[0062] The mixing temperature in the mixing step is preferably 50°C or higher, more preferably 100°C or higher, even more preferably 130°C or higher, and also preferably 200°C or lower, more preferably 170°C or lower, even more preferably 150°C or lower. Preferred ranges include approximately 50 to 200°C, 50 to 170°C, 50 to 150°C, 100 to 200°C, 100 to 170°C, 100 to 150°C, 130 to 200°C, 130 to 170°C, and 130 to 150°C.

[0063] The mixing process can be carried out under atmospheric pressure (air) or under an inert gas, and is preferably carried out under an inert gas. Examples of inert gases include nitrogen and argon.

[0064] The mixing time in the mixing process is preferably 1 hour or more, more preferably 5 hours or more, and also preferably 4 days or less, more preferably 1 day or less. Preferred ranges include 1 hour to 4 days, 1 hour to 1 day, 5 hours to 4 days, and 5 hours to 1 day.

[0065] In the manufacturing method of this disclosure, the mixture obtained in the mixing step can be subjected to one or more treatments selected from the group consisting of centrifugation, filtration, extraction, and washing. By subjecting it to these treatments, the purity of the amino group-containing cellulose can be increased. The methods of centrifugation, filtration, extraction, and washing are not particularly limited, and known methods can be used.

[0066] The amino group-containing cellulose obtained by the manufacturing method of this disclosure is a compound in which at least some of the hydroxyl groups contained in the β-glucose constituting the cellulose are replaced with amino groups derived from an amine compound. The amino group may have a hydrogen atom replaced by a substituent (for example, a hydrocarbon group such as a benzyl group). That is, the amino group may be N-substituted or an unsubstituted amino group. The average degree of substitution of the amino group is greater than 0 and less than or equal to 3, and is set appropriately depending on the application. For example, when the amino group-containing cellulose is used as a support, it is about 0.02 to 0.1; when imparting water solubility to the amino group-containing cellulose, it is about 0.5 to 1; and when imparting hydrophobicity to the amino group-containing cellulose, it is about 1.5 to 3. The average degree of substitution referred to here represents the average value of the aminated substituents among the three hydroxyl groups present in the glucose unit in the cellulose.

[0067] The amino group-containing cellulose obtained by the manufacturing method of this disclosure can be produced as amino group-containing cellulose fibers with widths of, for example, 1000 nm or less, 500 nm or less, 200 nm or less, and 100 nm or less (for the lower limit of the width, for example, 1 nm or more). The amino group-containing cellulose obtained by the manufacturing method of this disclosure can be easily broken down to nanocellulose (width of about 1 to 100 nm) using a wet atomization device / agitator such as a homogenizer. The amino group-containing cellulose can also be produced as a sheet of such fibers. The thickness of the sheet can be, for example, 1000 nm or less, 500 nm or less, 200 nm or less, and 100 nm or less. The width of the amino group-containing cellulose can be measured using a scanning electron microscope (SEM) image. For widths of 100 nm or less, it can also be measured using an atomic force microscope (AFM). Furthermore, the amino group-containing cellulose obtained by the manufacturing method of this disclosure can also be produced as a porous material, for example. A porous material made of amino group-containing cellulose is lightweight and has a sponge-like structure. Specific examples of porous materials containing amino group-containing cellulose include sponges, sound-absorbing materials, heat-insulating materials, moisture-absorbing materials, cushioning materials, artificial bones, filters, catalyst carriers, insulating materials, and shock-absorbing materials.

[0068] The amination cellulose obtained by the manufacturing method of this disclosure can be used, for example, in the medical field as a drug delivery system (used as a carrier to control the rate of drug release), a biomaterial (used in tissue engineering and wound dressings, etc., and possessing excellent biocompatibility), a diagnostic tool (used as a material for sensors and assays, especially for specific molecular binding), in environmental technology as a water treatment (used as a filter material to adsorb heavy metal ions (e.g., lead, cadmium, etc.) and harmful substances), a pollutant removal (used as an adsorbent or catalyst support for environmental purification), in the chemical industry as a catalyst carrier (a base material for immobilizing enzymes and chemical catalysts using amino groups), a surfactant and emulsifier (contributing to the acceleration of specific chemical reactions and the dispersion of substances), an adhesive, in the food and cosmetics fields as a food additive (used as a gel-forming or thickening agent to adjust the texture of food), a cosmetic material (used in skincare products to improve moisturizing effects and stability), and as a functional material as a separation membrane (exhibiting high selectivity as a membrane material used for gas separation and liquid separation), a packaging material, a film, a lightweight composite material for automobiles and aircraft, and a building material.

[0069] The present disclosure will be explained in more detail below with reference to examples.

[0070] [Production of amino group-containing cellulose] (Example 1) A pressure vessel (manufactured by Tokyo Rikakikai Co., Ltd., 14 mL, φ30) was used. An Ar atmosphere was created inside the pressure vessel by performing an Ar flow for 1 minute. 243 mg of cedar wood powder as a biomass raw material was placed in the pressure vessel, along with 17.8 mg of iridium catalyst represented by the following formula (A) and a stirring bar. The cedar wood powder was thoroughly air-dried, then pulverized using a Willie mill, and the particles that passed through a sieve with a mesh size of 1000 μm were collected. 5 mL of a 50 wt% dimethylamine aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was placed in the pressure vessel. The lid of the pressure vessel was closed and sealed. The lid of the pressure vessel was equipped with a pressure gauge and a pressure relief valve. The solution inside the pressure vessel was heated and stirred with a magnetic stirrer at a mixing temperature of 150°C and a reaction time (mixing time) of 4 days to obtain a solid-containing slurry.

[0071]

[0072] After cooling the pressure vessel in an ice bath, the solid-containing slurry was filtered by suction using No. 5C filter paper to separate it into an amine aqueous solution and solid matter on the filter paper. The resulting solid matter on the filter paper was further washed with a 50 wt% dimethylamine aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and ultrapure water to obtain water-washed solid matter. The obtained washing solution was mixed with the amine aqueous solution to obtain a dilute amine washing solution. All solid matter and water-soluble components remaining in the reaction vessel were transferred to the filter paper using dimethylamine and water and recovered as water-washed solid matter or dilute amine washing solution. The obtained water-washed solid matter was washed with methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to obtain washed solid matter and organic solvent washing solution. The dilute amine washing solution and the organic solvent washing solution were dried using a Convenience Evaporator (K4, manufactured by Biochromat Co., Ltd.) and a vacuum drying apparatus (manufactured by Ishii Rika Kiki Seisakusho Co., Ltd.) to obtain the dried dilute amine washing solution and the dried organic solvent washing solution. The washed solids were dried using a vacuum drying apparatus (manufactured by Ishii Rika Kiki Seisakusho Co., Ltd.) to obtain dried solids (amino group-containing cellulose). The weights of the dried solids and the dried dilute amine washing solution were measured (Table 1).

[0073] (Example 2) Except that the iridium catalyst was replaced with the compound shown in the following formula (B) and the amount added was 15.1 mg, a dried solid (amino group-containing cellulose) was obtained in the same manner as in Example 1.

[0074]

[0075] (Example 3) Except for using 135 mg of lyocell (manufactured by Fuji Spinning Holdings Co., Ltd.) instead of cedar wood flour as the biomass raw material, dried solid material (amino group-containing cellulose) was obtained in the same manner as in Example 1.

[0076] (Example 4) Except that the iridium catalyst was replaced with the compound shown in formula (B) above and the amount added was 15.1 mg, a dried solid (amino group-containing cellulose) was obtained in the same manner as in Example 3.

[0077] (Example 5) A dried solid (amino group-containing cellulose) was obtained in the same manner as in Example 3, except that the reaction time (mixing time) was set to 1 day.

[0078] (Example 6) A dried solid (amino group-containing cellulose) was obtained in the same manner as in Example 3, except that the reaction time (mixing time) was set to 2 days.

[0079] (Example 7) The reaction vessel was a larger pressure vessel (manufactured by Tokyo Rikakikai Co., Ltd., 63 mL, φ60), and 540 mg of pulp (Sulfite pulp "Fibenier J" Rayonier, Inc.) was used instead of lyocell as the biomass raw material, and 71.2 mg of iridium catalyst was used. The procedure was the same as in Example 3 to obtain dried solid material (amino group-containing cellulose).

[0080] (Example 8) Dried solid material (amino group-containing cellulose) was obtained in the same manner as in Example 7, except that lyocell was used instead of pulp as the biomass raw material.

[0081] (Example 9) A Schlenk container with a greaseless valve (φ16 × 120 mm, manufactured by Asahi Seisakusho) was substituted with Ar, and 270 mg of pulp as a biomass raw material (Sulfite pulp "Fibenier J" manufactured by Rayonier), 35.6 mg of iridium catalyst (formula (A) above), and a stirring bar were added. 1.07 g of benzylamine (manufactured by Nacalai Tesque Co., Ltd.) and 1 g of water were added to the Schlenk container. The stopcock of the Schlenk container was closed and sealed. The solution in the Schlenk container was heated and stirred at 110°C for 4 days while stirring with a magnetic stirrer to obtain a solid-containing slurry.

[0082] After cooling the pressure vessel in an ice bath, the solid-containing slurry was filtered by suction using No. 5C filter paper to separate it into an amine aqueous solution and solid matter on the filter paper. The obtained solid matter on the filter paper was further washed with methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to obtain washed solid matter and organic solvent washing solution. The washed solid matter was dried using a vacuum drying apparatus (manufactured by Ishii Rika Kiki Seisakusho Co., Ltd.) to obtain dried solid matter (amino group-containing cellulose). The weight of the dried solid matter was measured (Table 1).

[0083] (Example 10) Dried solid material (amino group-containing cellulose) was obtained in the same manner as in Example 7, except that 972 mg of cedar wood flour was used instead of pulp as the biomass raw material.

[0084] (Example 11) Except that the iridium catalyst was replaced with the compound shown in the following formula (C), the amount added was 19.2 mg, and 3 mL of pyrrolidine (manufactured by Nacalai Tesque) was used instead of a 50 wt% aqueous dimethylamine solution, a dried solid (amino group-containing cellulose) was obtained in the same manner as in Example 1.

[0085]

[0086] (Example 12) Except that the iridium catalyst was replaced with the compound shown in formula (C) above, the amount added was 19.2 mg, and 3 mL of pyrrolidine (manufactured by Nacalai Tesque) was used instead of a 50 wt% aqueous dimethylamine solution, a dried solid (amino group-containing cellulose) was obtained in the same manner as in Example 3.

[0087] (Comparative Example 1) A dried solid was obtained in the same manner as in Example 1, except that an iridium catalyst was not added.

[0088] (Comparative Example 2) A dried solid was obtained in the same manner as in Example 3, except that the iridium catalyst was not added.

[0089] (Comparative Example 3) A dried solid was obtained in the same manner as in Example 1, except that no iridium catalyst was added and water was added instead of a 50 wt% aqueous dimethylamine solution.

[0090] (Comparative Example 4) A dried solid was obtained in the same manner as in Example 10, except that no iridium catalyst was added.

[0091]

[0092] The yields (mass%) of the dried solid, the dried solid of the dilute amine washing solution, and the dried solid of the organic solvent washing solution in Table 1 are based on the mass of the raw material, cedar wood flour, being 100% by mass.

[0093] The evaluation methods used in the examples and comparative examples are as follows.

[0094] <NMR Measurement> NMR measurements were performed on the dried solid obtained in Example 8 under the following conditions. In an NMR test tube with an outer diameter of 5 mm, 50 mg of the powder sample (amination of cellulose) was mixed with 500 μL of DMSO-d6 and pyridine-d5 ((4:1, v / v)), and the sample was swollen by sonication at room temperature for 2 hours (S.D. Mansfield, H. Kim, F. Lu and J. Ralph, Nat. Protoc., 2012, 7, 1579-1589). A Brucker AVANCE III 600 spectrometer equipped with a cryoprobe (Brucker BioSpin, USA) was used to perform 2D spectroscopy of the swollen sample at 298 K. 1 H- 13 CHSQC spectra were acquired using Bruker's standard pulse program (hsqcetgpsisp2.2). The acquired NMR data was processed and analyzed using TopSpin (version 3.6, Bruker BioSpin, USA).

[0095] NMR measurements confirmed that in the dried solid (amino group-containing cellulose) obtained in Example 8, the hydroxyl groups in the cellulose structure were partially (4.5%) replaced with dimethylamino groups. The rate of dimethylamino group introduction (amination rate) was determined as follows.

[0096] <Integration range for aminated methylene group> Region 1 δC: 57.85–59.66 δH: 2.31–2.65

[0097] <Integration range for other methylene groups> Region 2 δC: 59.35–65.30 δH: 2.99–4.28 Region 3 δC: 65.69–68.34 δH: 3.71–4.06

[0098] <Calculation of Amination Rate>

[0099] <Measurement of Neutral Sugar and Lignin Content> The content (mass%) of neutral sugars (glucose, xylose, and mannose) and lignin was measured for the dried solids obtained in Examples 2, 10, and 11 and Comparative Examples 1, 3, and 4, respectively, according to the following procedure. The results are shown in Table 2.

[0100] (Procedure) 1. 20 mg of the dried biomass composition was mixed with 0.3 mL of 72% by weight sulfuric acid and stirred at 30°C for 1 hour. 2. 8.4 mL of water was added and the mixture was heated and decomposed in an autoclave at 120°C for 1 hour. 3. The reaction product after heating and decomposition was centrifuged (3500 rpm x 10 mins) to separate the supernatant from the precipitate. The precipitate was identified as lignin, washed with water until neutral, and then freeze-dried for 12 hours or more to completely dry it, after which its weight was measured. 4. Barium carbonate was added to the supernatant obtained by the centrifugation to neutralize it (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 pre-prepared calibration curve. Calibration curves were created for glucose, mannose, and xylose, and their concentrations in the measurement solution were quantified. The amounts of these monosaccharides were then converted to the equivalent amounts of polysaccharides.

[0101] Measurements were performed using the HPLC method 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

[0102]

[0103] <Molecular Weight Measurement> The molecular weight of the dried solids obtained in Examples 3, 5, and 6 was measured under the following conditions. The weight-average molecular weight and molecular weight distribution (in pullulan equivalent) were determined by the GPC method. (GPC measurement conditions) Instrument: LC-4000 HPLC (manufactured by JASCO Corporation) Column: GPC KD-806M (300 x 8.0 mm) (manufactured by Shodex) Guard column: GPC KD-G 4A (10 x 4.6 mm) (manufactured by Shodex) Detector: RI detector Eluent: 1% (w / v) LiCl / DMAc Sample preparation: After dissolving the sample in accordance with the literature (Y. Ono, R. Tanaka, R. Funahashi et al. Cellulose, 2016, 23, 1639-1647.), filter with a PTFE cartridge filter Calibration curve: First-order approximation using Shodex standard pullulan

[0104]

[0105] <Elemental Analysis> The dried solids obtained in each example and comparative example were subjected to elemental analysis (apparatus: Flash smart organic elemental analyzers (Thermo Fisher Scientific Co., Ltd.)) to measure the percentage of element N (N%). The results are shown in Table 1.

[0106] <Microscopic Observation> 300 mg each of the cedar wood powder used as biomass raw material, the dried solid obtained in Comparative Example 4, and Example 10 were measured out and placed in 20 mL screw-cap vials (Maruemu Co., Ltd., No. 5). The samples were suspended in 10 mL of water and ultrasonically treated for 1 hour at a frequency of 28 kHz using a benchtop ultrasonic cleaner (Honda Electronics Co., Ltd., W-113). Each sample was observed at 2x magnification using a stereomicroscope (Nikon SMZ1500), and the resulting images are shown in Figure 1. Furthermore, the samples were observed at 50x and 500x magnification using a benchtop scanning electron microscope (JEOL Ltd., JCM-7000), and the resulting images are also shown in Figure 1. The observation conditions were low vacuum mode and an acceleration voltage of 15.0 kV. As shown in Figure 1, the dried solid material of Example 10 is very finely defibrated compared to the cedar wood powder used as a biomass raw material, and the woody cell walls have broken down, resulting in a sheet-like structure with a thickness of 1 μm or less. Furthermore, when the dried solid material of Example 10 was measured using the same method as in Figure 1 but with a magnification of 1000x, the fibers (amino group-containing cellulose) constituting the dried solid material of Example 10 were mainly very fine, with a width of several hundred nanometers (see the SEM image in Figure 3). Similarly, the dried solid material of Comparative Example 4 is also finely defibrated compared to the cedar wood powder used as a biomass raw material, but the observed fiber width is 20 μm or more, indicating that the cell wall structure of the wood has not broken down.

[0107] <Dispersibility Test> 30 mg each of the freeze-dried solids from Comparative Example 4 and Example 10, and the cedar wood powder were measured and placed in microtubes (Maruemu Co., Ltd., No. 1). The samples were suspended in 1 mL of water and ultrasonically treated at a frequency of 28 kHz for 30 minutes using a tabletop ultrasonic cleaner (Honda Electronics Co., Ltd., W-113). The suspension was left to stand for 12 hours, and the height from the liquid surface to the dispersion was measured. The results are shown in Figure 2. From this, it was found that the dispersibility in water was improved in Example 10.

Claims

1. A method for producing amino group-containing cellulose, comprising a mixing step of mixing a biomass raw material containing cellulose with an amine compound in the presence of a catalyst.

2. The method for producing amino group-containing cellulose according to claim 1, wherein the catalyst includes a metal catalyst.

3. The method for producing amino group-containing cellulose according to claim 2, wherein the metal catalyst is at least one selected from the group consisting of iridium-based catalysts, iron-based catalysts, ruthenium-based catalysts, palladium-based catalysts, cobalt-based catalysts, nickel-based catalysts, rhodium-based catalysts, platinum-based catalysts, gold-based catalysts, osmium-based catalysts, manganese-based catalysts, chromium-based catalysts, copper-based catalysts, rhenium-based catalysts, and molybdenum-based catalysts.

4. The method for producing amino group-containing cellulose according to any one of claims 1 to 3, wherein the biomass raw material is a biomass raw material containing lignocellulose.

5. The method for producing amino group-containing cellulose according to any one of claims 1 to 3, wherein the mixing step is carried out in the presence of a solvent.

6. The method for producing amino group-containing cellulose according to claim 5, wherein the solvent is at least one of water and an organic solvent that does not have hydroxyl groups.

7. The method for producing amino group-containing cellulose according to claim 5, wherein the catalyst is dissolved in the solvent.

8. A method for producing amino group-containing cellulose according to any one of claims 1 to 3, wherein the mixing ratio of the amine compound with respect to 1 part by mass of the cellulose is 0.001 parts by mass or more and 1000 parts by mass or less.

9. A method for producing amino group-containing cellulose according to any one of claims 1 to 3, wherein the mixing ratio of the catalyst to 1 mole of hydroxyl groups contained in the cellulose is 0.0001 moles or more and 0.5 moles or less.

10. A method for producing amino group-containing cellulose according to any one of claims 1 to 3, wherein a basic compound is further mixed in the mixing step.

11. A method for producing amino group-containing cellulose according to any one of claims 1 to 3, wherein the mixing temperature in the mixing step is 50°C or more and 200°C or less.

12. A method for producing amino group-containing cellulose according to any one of claims 1 to 3, wherein the mixture obtained in the mixing step is subjected to one or more treatments selected from the group consisting of centrifugation, filtration, extraction, and washing.

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