Modified cellulose

Abstract

Provided is modified cellulose in which at least some of the hydroxyl groups of cellulose are modified using an acyl group. The cellulose contains an oxide, of a cellulose-based feedstock, resulting from hypochlorous acid or a salt thereof, and is substantially free of an N-oxyl compound. The degree of modification of the hydroxyl groups by the acyl group is within a range in which a mixed solution of the modified cellulose and an organic solvent exhibits birefringence and a light transmittance of 75% or greater, and the organic solvent is at least one type of substance selected from the group consisting of acetone, methanol, and ethyl acetate.

Description

Modified cellulose

[0001] The present invention relates to modified cellulose.

[0002] Various techniques have been proposed for producing nanocellulose materials by oxidizing various cellulosic raw materials with an oxidizing agent and then micronizing the resulting oxidized cellulose.

[0003] For example, Patent Document 1 discloses a method for producing cellulose nanofibers, which includes a step of oxidizing a cellulosic raw material using hypochlorous acid or a salt thereof having an available chlorine concentration of 14 to 43% by mass to produce oxidized cellulose, and a step of defibrating the oxidized cellulose to nanosize it. Patent Document 2 also discloses a method for producing oxidized cellulose, which involves oxidizing a cellulosic raw material using hypochlorous acid or a salt thereof having an available chlorine concentration of 6 to 14% by mass while adjusting the pH to a range of 5.0 to 14.0. These methods perform the oxidation treatment without using N-oxyl compounds such as 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (TEMPO), so no N-oxyl compounds remain in the cellulose fibers, thereby reducing their impact on the environment, etc.

[0004] Patent Document 3 discloses oxidized cellulose, which is an oxidation product of a cellulosic raw material with hypochlorous acid or a salt thereof, which is substantially free of N-oxyl compounds and has a degree of polymerization of 600 or less.

[0005] Patent Document 4 discloses nanocellulose, which is an oxide of a cellulose-based raw material with hypochlorous acid or a salt thereof, has an average fiber width of 1 nm or more and 200 nm or less, is substantially free of N-oxyl compounds, and has a zeta potential of -30 mV or less.

[0006] International Publication No. WO 2018 / 230354 International Publication No. WO 2020 / 027307 International Publication No. WO 2022 / 009979 International Publication No. WO 2022 / 009980

[0007] An object of the present invention is to provide cellulose that has excellent dispersibility in organic solvents.

[0008] By modifying the hydroxyl groups of cellulose oxidized by a predetermined method with acyl groups, it is possible to provide cellulose that is excellent in dispersibility in organic solvents.

[0009] The present invention includes the following embodiments. [1] Modified cellulose in which at least some of the hydroxyl groups of cellulose have been modified with acyl groups, the modified cellulose having a structure in which the second and third hydroxyl groups of the glucopyranose ring have been oxidized to introduce dicarboxy groups, the degree of modification of the hydroxyl groups with the acyl groups is within a range in which a mixture of the modified cellulose and an organic solvent exhibits birefringence and a light transmittance of 75% or more, and the organic solvent is at least one selected from the group consisting of acetone, methanol, and ethyl acetate. [2] Modified cellulose in which at least some of the hydroxyl groups of cellulose have been modified with acyl groups, the cellulose comprising an oxide of a cellulose-based raw material with hypochlorous acid or a salt thereof and substantially free of N-oxyl compounds, the degree of modification of the hydroxyl groups with the acyl groups is within a range in which a mixture of the modified cellulose and an organic solvent exhibits birefringence and a light transmittance of 75% or more, and the organic solvent is at least one selected from the group consisting of acetone, methanol, and ethyl acetate. [3] The modified cellulose according to [1] or [2], wherein the modified cellulose is modified nanocellulose. [4] The modified cellulose according to any one of [1] to [3], wherein the hydroxyl group modified with the acyl group is represented by the following formula (1): R-C(=O)-O- (1) [R is a hydrocarbon group]. [5] The modified cellulose according to [4], wherein the hydrocarbon group has 1 to 8 carbon atoms. [5-1] The modified cellulose according to [4] or [5], wherein the hydrocarbon group has 1 to 5 carbon atoms. [5-2] The modified cellulose according to any one of [4] to [5-1], wherein the hydrocarbon group has 1 to 3 carbon atoms. [5-3] The modified cellulose according to any one of [4] to [5-2], wherein the hydrocarbon group is an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, a cycloalkynyl group, or an aryl group. [5-4] The modified cellulose according to any one of [4] to [5-3], wherein the hydrocarbon group is an alkyl group or an alkenyl group.[5-5] The modified cellulose according to any one of [4] to [5-4], wherein the acyl group (R—C(═O)—) is an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, an acryloyl group, a methacryloyl group, or a benzoyl group. [6] A modified cellulose in which at least some of the hydroxyl groups of cellulose have been modified with acyl groups, wherein the cellulose has a structure in which the hydroxyl groups at the second and third positions of a glucopyranose ring have been oxidized to introduce dicarboxy groups, and the hydroxyl groups modified with the acyl groups are represented by the following formula (1): R—C(═O)—O- (1), where R is a hydrocarbon group. [7] Modified cellulose in which at least some of the hydroxyl groups of cellulose are modified with acyl groups, the cellulose comprising an oxidation product of a cellulose-based raw material with hypochlorous acid or a salt thereof and substantially free of N-oxyl compounds, the hydroxyl groups modified with the acyl groups being represented by the following formula (1): R-C(=O)-O- (1) [R is a hydrocarbon group]. [7-1] The modified cellulose according to [6] or [7], wherein the hydrocarbon group has 1 to 8 carbon atoms. [7-2] The modified cellulose according to any one of [6] to [7-1], wherein the hydrocarbon group has 1 to 5 carbon atoms. [7-3] The modified cellulose according to any one of [6] to [7-2], wherein the hydrocarbon group has 1 to 3 carbon atoms. [7-4] The modified cellulose according to any one of [6] to [7-3], wherein the hydrocarbon group is an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, a cycloalkynyl group, or an aryl group. [7-5] The modified cellulose according to any one of [6] to [7-4], wherein the hydrocarbon group is an alkyl group or an alkenyl group. [7-6] The modified cellulose according to any one of [6] to [7-5], wherein the acyl group (R—C(═O)—) is an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, an acryloyl group, a methacryloyl group, or a benzoyl group. [8] A cellulose dispersion comprising the modified cellulose according to any one of [1] to [7-5], and an organic solvent.[9] A composition comprising the modified cellulose according to any one of [1] to [7-5] and a hydrophobic material.

[0010] The present invention can provide cellulose that is excellent in dispersibility in organic solvents.

[0011] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these and various modifications are possible without departing from the gist of the present invention.

[0012] <Modified Cellulose 1> One embodiment of the present invention relates to modified cellulose in which at least some of the hydroxyl groups of cellulose have been modified with acyl groups, the cellulose comprising an oxide of a cellulose-based raw material with hypochlorous acid or a salt thereof and substantially free of N-oxyl compounds, the degree of modification of the hydroxyl groups with the acyl groups being within a range in which a mixture of the modified cellulose and an organic solvent exhibits birefringence and a light transmittance of 75% or more, and the organic solvent is at least one selected from the group consisting of acetone, methanol, and ethyl acetate.

[0013] The modified cellulose according to the present embodiment, which is derived from an oxidation product of a cellulose-based raw material using hypochlorous acid or its salt, has excellent dispersibility in organic solvents because the hydroxyl groups have been modified with acyl groups. On the other hand, modified cellulose derived from cellulose obtained by other methods (e.g., TEMPO oxidation or mechanical defibration) aggregates in organic solvents even if the hydroxyl groups have been modified with acyl groups. Therefore, it is surprising that the modified cellulose according to the present embodiment has excellent dispersibility in organic solvents.

[0014] Furthermore, in the modified cellulose according to the present embodiment, the degree of modification of hydroxyl groups by acyl groups is controlled within a predetermined range, so that the modified cellulose has excellent dispersibility in organic solvents while avoiding dissolution in organic solvents. By preventing the modified cellulose from dissolving in organic solvents, a high degree of crystallinity (high strength) can be achieved.

[0015] The cellulose in this embodiment includes an oxide of a cellulosic raw material with hypochlorous acid or a salt thereof. The oxide of a cellulosic raw material with hypochlorous acid or a salt thereof may be either oxidized cellulose or nanocellulose, but is preferably nanocellulose.

[0016] [Oxidized Cellulose] In this specification, "oxidized cellulose" refers to an oxide of a cellulosic raw material with hypochlorous acid or a salt thereof, before defibration.

[0017] Examples of hypochlorous acid or salts thereof include hypochlorous acid water, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and ammonium hypochlorite.

[0018] Although the amount of hypochlorous acid or its salt to be used is not particularly limited, it is preferable to use it so that the effective chlorine concentration in the reaction system is 6 to 43 mass%. The effective chlorine concentration may be a low concentration of 6 to 14 mass% or a high concentration of 14 to 43 mass%.

[0019] The definition of the effective chlorine concentration of hypochlorous acid or a salt thereof is as described in WO 2022 / 009979.

[0020] The cellulosic raw material is not particularly limited as long as it is a material primarily composed of cellulose, and examples thereof include pulp, natural cellulose, and fine cellulose obtained by depolymerizing cellulose through mechanical processing. The cellulosic raw material preferably has a type I crystal structure. Commercially available cellulose-based raw materials, such as crystalline cellulose derived from pulp, can be used as is. Alternatively, unused biomass containing a large amount of cellulose, such as soybean hulls or soybean pulp, may also be used as the raw material. Furthermore, the cellulosic raw material may be pre-treated with an appropriate concentration of alkali to facilitate the penetration of the oxidizing agent into the raw pulp. Cellulose is the main component of plants, and bundles of cellulose molecules are called cellulose microfibrils. The cellulose in the cellulosic raw material is also present in the form of cellulose microfibrils.

[0021] (N-oxyl compounds) The oxidized cellulose of the present embodiment is substantially free of N-oxyl compounds. By being substantially free of N-oxyl compounds, its impact on the environment and human body is sufficiently reduced, resulting in a high level of safety. An example of an N-oxyl compound is 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO).

[0022] As used herein, "substantially free of N-oxyl compounds" means that no N-oxyl compounds are used in producing the oxidized cellulose, that the oxidized cellulose contains no N-oxyl compounds, or that the content of N-oxyl compounds is 2.0 ppm by mass or less, preferably 1.0 ppm by mass or less, relative to the total amount of oxidized cellulose. Furthermore, when the content of N-oxyl compounds, as an increase from the cellulosic raw material, is preferably 2.0 ppm by mass or less, more preferably 1.0 ppm by mass or less, it is also considered to be "substantially free of N-oxyl compounds."

[0023] The content of N-oxyl compounds can be measured by known means, such as a method using a trace total nitrogen analyzer (for example, TN-2100H manufactured by Nitto Seiko Analytech Co., Ltd.).

[0024] (Carboxy group amount) The carboxy group amount of the oxidized cellulose in this embodiment is preferably 0.1 to 3.0 mmol / g, more preferably 0.2 to 2.0 mmol / g, even more preferably 0.3 to 1.5 mmol / g, particularly preferably 0.4 to 1.2 mmol / g, and most preferably 0.5 to 0.9 mmol / g.

[0025] The amount of carboxy groups in oxidized cellulose can be measured by the method described in WO 2022 / 009979.

[0026] The oxidized cellulose in this embodiment preferably has a structure in which at least two of the hydroxyl groups on the glucopyranose ring that constitutes the cellulose are oxidized, and more specifically, preferably has a structure in which the hydroxyl groups at the second and third positions on the glucopyranose ring are oxidized and dicarboxyl groups are introduced. Furthermore, it is preferable that the hydroxyl group at the sixth position on the glucopyranose ring is not oxidized and remains as a hydroxyl group. The position of the carboxyl group on the glucopyranose ring is determined by the solid １３ It can be analyzed by C-NMR spectrum.

[0027] Rayon has the same chemical structure as cellulose, and its oxide (rayon oxide) is water-soluble. １３ By performing C-NMR measurement, a carbon peak attributable to a carboxy group is observed at 165 to 185 ppm. In one embodiment of the oxidation of a cellulosic raw material with hypochlorous acid or its salt, two signals appear in this chemical shift range. Furthermore, by solution two-dimensional NMR measurement, it can be determined that the carboxy groups are introduced at the 2- and 3-positions.

[0028] Solid oxide of cellulosic raw materials with hypochlorous acid or its salts １３ In C-NMR, when the amount of carboxyl groups introduced is large, two signals appear at 165 to 185 ppm, and when the amount of carboxyl groups introduced is small, a very broad signal may appear. As can be seen from the results for oxidized rayon, the signals of the carboxyl group carbons introduced at the 2nd and 3rd positions are close to each other, and the signals are not clearly visible in solid state analysis with low resolution. １３ In C-NMR, the separation of the two signals is insufficient. Therefore, when the amount of carboxyl group introduced is small, a broad signal is observed. １３ In the C-NMR spectrum, the introduction of carboxy groups at the 2- and 3-positions can be confirmed by evaluating the broadening of the peak appearing at 165 to 185 ppm.

[0029] That is, solid １３A baseline is drawn around the peak in the range of 165 ppm to 185 ppm in a C-NMR spectrum to determine the overall area value, and then the area value is vertically divided at the peak top to determine the ratio of the two peak area values ​​(larger area value / smaller area value). If this peak area value ratio is 1.2 or greater, the peak is considered to be broad. The presence or absence of a broad peak can be determined by the ratio of the length L of the baseline in the range of 165 ppm to 185 ppm to the length L' of the perpendicular line from the peak top to the baseline. That is, if the ratio L' / L is 0.1 or greater, it can be determined that a broad peak is present. The ratio L' / L may be 0.2 or greater, 0.3 or greater, 0.4 or greater, or 0.5 or greater. The upper limit of the ratio L' / L is not particularly limited, but it is usually 3.0 or less, or may be 2.0 or less, or 1.0 or less.

[0030] The structure of the glucopyranose ring can also be determined by analysis according to the method described in Sustainable Chem. Eng. 2020, 8, 48, 17800-17806.

[0031] (Viscosity-average degree of polymerization) The viscosity-average degree of polymerization of the oxidized cellulose in this embodiment is preferably 30-500, more preferably 60-300, even more preferably 70-150, and particularly preferably 80-130.

[0032] The viscosity average degree of polymerization is the average degree of polymerization measured by a viscosity method. The viscosity average degree of polymerization can be measured by the method described in WO 2022 / 009979.

[0033] [Method for producing oxidized cellulose] The oxidized cellulose in this embodiment can be produced by oxidizing a cellulosic raw material with hypochlorous acid or a salt thereof. Specific production methods include those described in WO 2022 / 009979 and WO 2022 / 009980. Oxidized cellulose is also available as a commercially available product, such as Aronfibro (registered trademark) manufactured by Toagosei Co., Ltd.

[0034] [Nanocellulose] In this specification, "nanocellulose" refers to an oxide of a cellulose-based raw material with hypochlorous acid or a salt thereof, after defibration.

[0035] Nanocellulose is a general term for micronized cellulose, and includes micronized cellulose fibers, cellulose nanocrystals (CNC), etc. Micronized cellulose fibers are also called cellulose nanofibers (CNF).

[0036] The nanocellulose in this embodiment contains a carboxyl group. The carboxyl group may be in the H type (—COOH) or in the salt type. The type of salt is not particularly limited, but examples include alkali metal salts such as lithium salts, sodium salts, and potassium salts; alkaline earth metal salts such as calcium salts and barium salts; other metal salts such as magnesium salts and aluminum salts; ammonium salts, and organic amine salts.

[0037] Nanocellulose is a collection of individual fibers. When nanocellulose contains carboxylated nanocellulose, it is sufficient that it contains at least one carboxylated nanocellulose, and it is preferable that carboxylated nanocellulose is the main component. Here, carboxylated nanocellulose being the main component means that the proportion of carboxylated nanocellulose in the total amount of nanocellulose exceeds 50% by mass, preferably exceeds 70% by mass, and more preferably exceeds 80% by mass. The upper limit of the above proportion is 100% by mass, but it may also be 98% by mass or 95% by mass.

[0038] (N-oxyl compounds) The nanocellulose in this embodiment is substantially free of N-oxyl compounds. The meaning of "nanocelulose is substantially free of N-oxyl compounds" and the method for measuring the content of N-oxyl compounds are as described in the (N-oxyl compounds) section of [Oxidized Cellulose] above.

[0039] (Carboxy group amount) The carboxy group amount of nanocellulose in this embodiment and the method for measuring it shall follow the description in the (Carboxy group amount) section of [Oxidized cellulose] above.

[0040] (Average fiber length) The average fiber length of the nanocellulose in this embodiment is preferably 50 to 700 nm, more preferably 50 to 500 nm, even more preferably 50 to 300 nm, still more preferably 60 to 300 nm, and particularly preferably 70 to 200 nm.

[0041] (Average fiber width) The average fiber width of the nanocellulose in this embodiment is preferably 1 to 200 nm, more preferably 1 to 15 nm, even more preferably 1 to 10 nm, and particularly preferably 1 to 5 nm.

[0042] The average fiber width and average fiber length of nanocellulose can be measured by the method described in WO 2022 / 009980.

[0043] (Aspect Ratio) The aspect ratio (average fiber length / average fiber width) of the nanocellulose in this embodiment is preferably 20 to 200, more preferably 30 to 190, and even more preferably 40 to 180.

[0044] (Zeta potential) The zeta potential of the nanocellulose in this embodiment is preferably −30 mV or less, more preferably −90 mV or more and −30 mV or less, even more preferably −80 mV or more and −30 mV or less, still more preferably −70 mV or more and −30 mV or less, and particularly preferably −65 mV or more and −35 mV or less.

[0045] The zeta potential can be measured by the method described in WO 2022 / 009980.

[0046] [Method for producing nanocellulose] The nanocellulose in this embodiment can be produced by defibrating the above-mentioned oxidized cellulose. Specific production methods include those described in WO 2022 / 009979 and WO 2022 / 009980. Nanocellulose can also be obtained by defibrating commercially available oxidized cellulose (for example, Aronfibro (registered trademark) manufactured by Toagosei Co., Ltd.).

[0047] [Modification (Substitution)] The modified cellulose in this embodiment is cellulose in which at least some of the hydroxyl groups have been modified with acyl groups. The modified cellulose may be either oxidized cellulose in which at least some of the hydroxyl groups have been modified with acyl groups (hereinafter referred to as "modified oxidized cellulose"), or nanocellulose in which at least some of the hydroxyl groups have been modified with acyl groups (hereinafter referred to as "modified nanocellulose"). Modified nanocellulose is preferred. Modified nanocellulose also includes modified oxidized cellulose that has been defibrated. The modified cellulose in this embodiment does not necessarily include modified cellulose in which at least some of the hydroxyl groups of cellulose have been modified with acyl groups derived from maleic acid and / or itaconic acid.

[0048] Modification of cellulose hydroxyl groups with acyl groups can increase the hydrophobicity of cellulose and improve its dispersibility in organic solvents. Modification of hydroxyl groups with acyl groups can also be expressed as the substitution of hydrogen atoms of hydroxyl groups with acyl groups. For example, by reacting an acylating agent with the hydroxyl groups of cellulose, the hydroxyl groups can be modified with acyl groups (substituting hydrogen atoms of hydroxyl groups with acyl groups). In this specification, the substitution of hydrogen atoms of hydroxyl groups with acyl groups is simply referred to as "substitution of hydroxyl groups with acyl groups," and "substitution of hydroxyl groups with acyl groups" is synonymous with modifying hydroxyl groups with acyl groups, and "modification" is also referred to as "substitution."

[0049] The hydroxyl group modified with an acyl group is preferably represented by the following formula (1): R—C(═O)—O— (1)

[0050] R in formula (1) is a hydrocarbon group, preferably an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, a cycloalkenyl group, a cycloalkynyl group, or an aryl group, and more preferably an alkyl group or an alkenyl group.

[0051] The hydrocarbon group R in formula (1) is a group consisting of only carbon and hydrogen. The hydrocarbon group preferably has 1 to 8 carbon atoms, more preferably 1 to 5 carbon atoms, and even more preferably 1 to 3 carbon atoms.

[0052] The alkyl group, alkenyl group, and alkynyl group represented by R in formula (1) may be linear or branched.

[0053] The alkyl group, alkenyl group, and alkynyl group represented by R in formula (1) preferably have 1 to 8 carbon atoms, more preferably 1 to 5 carbon atoms, and even more preferably 1 to 3 carbon atoms.

[0054] The cycloalkyl group, cycloalkenyl group, cycloalkynyl group, and aryl group represented by R in formula (1) preferably have 3 to 14 carbon atoms, more preferably 4 to 10 carbon atoms, and even more preferably 5 to 6 carbon atoms.

[0055] R in formula (1) may be substituted or unsubstituted.

[0056] The acyl group (R—C(═O)—) in formula (1) is preferably an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, an acryloyl group, a methacryloyl group, or a benzoyl group.

[0057] The multiple hydroxyl groups of the cellulose may be modified with one type of acyl group or multiple types of acyl groups.

[0058] The degree of modification (substitution degree) of hydroxyl groups with acyl groups is preferably within a range in which a mixture of modified cellulose and an organic solvent exhibits birefringence and a light transmittance of 75% or more (preferably 80% or more). Exhibiting birefringence means that the modified cellulose is not dissolved in the organic solvent. Exhibiting a light transmittance of 75% or more means that the modified cellulose is dispersed in the organic solvent without agglomeration. The methods for measuring birefringence and light transmittance are as follows.

[0059] (Birefringence) A mixture of modified cellulose and an organic solvent (modified cellulose concentration: 1% by mass) is defibrated using an ultrasonic dispersion device and diluted to 0.1% by mass with the same organic solvent. The diluted mixture is sandwiched between crossed polarizing plates, and the presence or absence of birefringence is visually confirmed. A more specific method for measuring birefringence is as described in the Examples below.

[0060] (Light transmittance) A mixture of modified cellulose and an organic solvent (modified cellulose concentration: 1% by mass) is defibrated using an ultrasonic dispersion device and diluted to 0.1% by mass with the same organic solvent. The diluted mixture is measured using a UV-visible spectrophotometer (glass cell optical path length: 10 mm, wavelength: 660 nm) to measure the light transmittance. A more specific method for measuring the light transmittance is as described in the Examples below.

[0061] The organic solvents used in the measurement of birefringence and light transmittance are acetone, methanol, or ethyl acetate. It is preferable that the birefringence and the predetermined light transmittance are exhibited in at least one, preferably at least two, and more preferably all of these organic solvents.

[0062] Increasing the degree of modification tends to increase light transmittance. On the other hand, if the degree of modification is too high, the modified cellulose dissolves in an organic solvent, preventing birefringence. Therefore, the degree of modification can be appropriately adjusted so as to exhibit birefringence and a predetermined light transmittance. The specific degree of modification varies depending on the type of acyl group, but may be, for example, 0.8 to 2.5 or 0.9 to 2.0. In order to exhibit birefringence and achieve a light transmittance of 75% or more, the type of acyl group can be appropriately selected and the degree of modification can be appropriately adjusted.

[0063] The method for measuring the degree of modification is as described in the Examples below.

[0064] <Modified Cellulose 2> One embodiment of the present invention relates to modified cellulose in which at least some of the hydroxyl groups of cellulose are modified with acyl groups, the cellulose comprising an oxide of a cellulose-based raw material with hypochlorous acid or a salt thereof and substantially free of N-oxyl compounds, and the hydroxyl groups modified with the acyl groups are represented by the following formula (1): R—C(═O)—O— (1) [R is a hydrocarbon group].

[0065] To avoid repetitive explanation, the description in the above section <Modified Cellulose 1> will be quoted here to explain the elements of the modified cellulose according to this embodiment.

[0066] <Cellulose Dispersion> One embodiment of the present invention relates to a cellulose dispersion containing the above-described modified cellulose and an organic solvent. The dispersion of the present invention is not a solution, but a liquid in which the modified cellulose is dispersed in an organic solvent. In the dispersion of the present invention, the modified cellulose is preferably dispersed without agglomeration. Whether or not a dispersion is applicable can be determined by the presence or absence of birefringence and light transmittance. For example, a dispersion is determined to be one that has birefringence and is within a range showing a light transmittance of 75% or more.

[0067] The type of organic solvent is not particularly limited, and examples thereof include ketone solvents, alcohol solvents, ester solvents, ether solvents, nitrile solvents, and hydrocarbon solvents. The organic solvent may be appropriately selected depending on the target to be mixed with the cellulose dispersion.

[0068] <Composition> One embodiment of the present invention relates to a composition comprising the above-mentioned modified cellulose and a hydrophobic material. The hydrophobic material is not particularly limited, and is preferably miscible with the modified cellulose.

[0069] <Applications> The modified nanocellulose described above, as well as dispersions and compositions containing the same, can be used in a variety of applications. Specifically, for example, it may be mixed with resins, fibers, rubber, etc., and may be used in foods, cosmetics, medical products, paints, inks, adhesives, etc. The paint may be an organic paint or an inorganic paint, and the type of paint is not particularly limited, but examples include metallic paints. The modified nanocellulose may also be used as an emulsifier.

[0070] Furthermore, for example, a dispersion containing modified nanocellulose can be formed into a film and used as various sheets or films. That is, a dispersion containing modified nanocellulose can be used as a coating agent. A film obtained from modified nanocellulose can be used as a protective sheet or protective film. Examples of objects that can be protected by the protective sheet or protective film include liquid crystal displays. Furthermore, modified nanocellulose can also be used as a gas barrier film, a battery separator film, etc., in combination with various resins, etc., as needed.

[0071] The fields in which the modified nanocellulose, and nanocellulose dispersions and compositions containing the same can be applied are not particularly limited, and can be used in the manufacture of products in various fields such as automotive components, machine parts, electrical appliances, electronic devices, cosmetics, medical products, building materials, daily necessities, stationery, etc.

[0072] The present invention will be described in more detail below using examples and comparative examples, but the technical scope of the present invention is not limited thereto. Various values ​​in the examples may be used as preferred lower or upper limits in the embodiments of the present invention. Furthermore, two values ​​of the same type in the examples may be appropriately combined to form a preferred numerical range.

[0073] <Preparation of Cellulose> [Example 1] (Oxidation Step) Pulp (KC Flock W100GK, Nippon Paper Industries Co., Ltd.) was used as the cellulosic raw material. 350 g of sodium hypochlorite pentahydrate crystals with an effective chlorine concentration of 42% by mass were placed in a beaker, and pure water was added and stirred to obtain a sodium hypochlorite aqueous solution with an effective chlorine concentration of 21% by mass. 35% by mass of hydrochloric acid was then added and stirred to adjust the pH to 11.0. This sodium hypochlorite aqueous solution was heated to 30°C in a thermostatic water bath while stirring at 200 rpm using a propeller-type stirring blade in a Shinto Scientific mixer (Three-One Motor, BL600), and 50 g of the pulp was then added. After adding the cellulosic raw material, the solution was kept at 30°C in the same thermostatic water bath while adding a 48% by mass aqueous sodium hydroxide solution to maintain the pH at 11.0 during the reaction. The mixture was stirred at 200 rpm using a propeller-type stirring blade, and the oxidation reaction was carried out for 4 hours (pH was maintained). After the reaction was completed, the mixture was filtered using a filter cloth (manufactured by Nakao Filter Co., Ltd., KE022, air permeability 0.3 cc / cm ２ The product was subjected to solid-liquid separation by pressure filtration using a pressure filtration filter (pressure filtration / sec), and the resulting oxidized cellulose solid was washed with pure water. The amount of carboxy groups in the oxidized cellulose was 0.7 mmol / g.

[0074] The effective chlorine concentration in the sodium hypochlorite aqueous solution was measured by the following method. (Measurement of effective chlorine concentration in sodium hypochlorite aqueous solution) 0.582 g of an aqueous solution prepared by adding sodium hypochlorite pentahydrate crystals to pure water was precisely weighed, 50 mL of pure water was added, 2 g of potassium iodide and 10 mL of acetic acid were added, and the container was immediately sealed and left in the dark for 15 minutes. After leaving the container for 15 minutes, the liberated iodine was titrated with 0.1 mol / L sodium thiosulfate solution (solution factor 1.000) (indicator: starch test solution), and the titration amount was 34.55 mL. A blank test was separately performed to correct for this, and since 1 mL of 0.1 mol / L sodium thiosulfate solution corresponds to 3.545 mg Cl, the effective chlorine concentration in the sodium hypochlorite aqueous solution was 21% by mass.

[0075] (Defibrillation process) An aqueous dispersion of Na-type oxidized cellulose (7.5% solids) was treated with a homomixer (Robomix, manufactured by Tokushu Kikka) at 10,000 rpm for 33 minutes, using 440 g of liquid, to defibrate the oxidized cellulose into nanocellulose, yielding an aqueous nanocellulose dispersion (T-CN 100). A 1N aqueous solution of hydrochloric acid was added to the resulting aqueous dispersion to adjust the pH to 2.0-2.1, and the mixture was washed twice with pure water using a tabletop multi-rack centrifuge (H-40α, manufactured by Kokusan). The mixture was then washed four times with acetone in the same manner, and concentrated by suction filtration using a vacuum pump to obtain H-type nanocellulose.

[0076] (Modification step) To 1 part by mass of H-type nanocellulose, 1.2 parts by mass of acetic anhydride, 6.0 parts by mass of acetone, and 14.4 parts by mass of toluene were added with stirring, and then 0.02 parts by mass of perchloric acid was added and stirred at room temperature for 1 hour. After quenching by adding ethanol to the reaction solution, washing to remove the supernatant after centrifugation was repeated seven times using a tabletop multi-rack centrifuge (KOKUSAN, H-40α) and acetone to obtain acetyl-modified H-type nanocellulose.

[0077] [Example 2] Acetyl-modified H-type nanocellulose was obtained in the same manner as in Example 1, except that the amount of acetic anhydride in the modification step of Example 1 was changed to 1.5 parts by mass.

[0078] [Comparative Example 1] Acetyl-modified H-type nanocellulose was obtained in the same manner as in Example 1, except that the amount of acetic anhydride in the modification step of Example 1 was changed to 0.8 parts by mass.

[0079] [Comparative Example 2] Acetyl-modified H-type nanocellulose was obtained in the same manner as in Example 1, except that the amount of acetic anhydride in the modification step of Example 1 was changed to 2.7 parts by mass.

[0080] [Example 3] Methacryloyl-modified H-type nanocellulose was obtained in the same manner as in Example 1, except that the acetic anhydride in the modification step of Example 1 was changed to 1.5 parts by mass of methacrylic anhydride and the reaction temperature was changed to 50 ° C. For 1 part by mass of methacryloyl-modified H-type nanocellulose, 1.1 parts by mass of acetic anhydride, 6.0 parts by mass of acetone, and 14.4 parts by mass of toluene were added with stirring, and then 0.02 parts by mass of perchloric acid was added and stirred at room temperature for 1 hour. After quenching by adding ethanol to the reaction solution, washing to remove the supernatant after centrifugation was repeated seven times using a tabletop multi-rack centrifuge (KOKUSAN, H-40α) and acetone to obtain acetyl-modified and methacryloyl-modified H-type nanocellulose.

[0081] Comparative Example 3 Acetyl-modified cellulose was obtained in the same manner as in Example 1, except that the H-type nanocellulose in the modification step of Example 1 was changed to powdered cellulose (KC Flock, manufactured by Nippon Paper Industries Co., Ltd.).

[0082] Comparative Example 4 Acetyl-modified cellulose was obtained in the same manner as in Example 1, except that the H-type nanocellulose in the modification step of Example 1 was changed to mechanically defibrated cellulose (manufactured by Sugino Machine Corporation, BiNFis standard grade).

[0083] Comparative Example 5 Acetyl-modified cellulose was obtained in the same manner as in Example 1, except that the H-type nanocellulose in the modification step of Example 1 was changed to TEMPO-oxidized CNF (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Rheocrysta I-2SX).

[0084] <Test Method> [Carboxy Group Amount] To 100 mL of the cellulose aqueous dispersion obtained in each Example and Comparative Example, in which the cellulose concentration was adjusted to 0.1% by mass, 0.1 M aqueous hydrochloric acid was added to adjust the pH to 2.5, and then 0.05 N aqueous sodium hydroxide solution was added dropwise, and the electrical conductivity was measured until the pH reached 11.0. The amount of carboxy groups (mmol / g) was calculated using the following formula from the amount of sodium hydroxide (a) consumed in the neutralization stage of weak acid, in which the change in electrical conductivity was gradual: Amount of carboxy groups = a (mL) × 0.05 / mass of cellulose (g).

[0085] [Degree of substitution (degree of modification)] 0.05 g of modified cellulose (i.e., acetylated H-type oxidized nanocellulose, methacryloyl-modified H-type nanocellulose, or acetyl-modified and methacryloyl-modified H-type nanocellulose) was precisely weighed, and 1.5 ml of ethanol and 0.5 ml of distilled water were added to it. After leaving this in a water bath at 60 to 70 ° C for 30 minutes, 2 ml of 0.5 M aqueous sodium hydroxide solution was added. After leaving this in a water bath at 60 to 70 ° C for 3 hours, it was ultrasonically shaken for 30 minutes in an ultrasonic cleaner. This was titrated with a 0.1 M standard solution of hydrochloric acid using phenolphthalein as an indicator. Here, the amount Z (ml) of 0.1 M aqueous hydrochloric acid solution required for the above titration, and the amount Z of 0.1 N aqueous hydrochloric acid solution required for titration of a blank sample (= sample without modified cellulose) were ０ From the total amount of carboxyl groups and acyl groups (ml), the total amount Q (mol) was calculated using the following formula: Q (mol) = (Z ０ -Z)×0.1 / 1000

[0086] The mass of the modified cellulose (=0.05 g precisely weighed value, symbolized as A) is the mass of the unmodified glucopyranose ring structure (C ６ H １０ O ５ , Mw=162) and the mass of the glucopyranose structure (C ６ H ８ O ７ The mass of the glucopyranose structure (Mw = 192) modified (substituted) with an acyl group (Mw = 145 + T (T is the molecular weight of the acyl group)) can be considered as the sum of these. If the number of moles of each structure is x, y, and z (mol), then Equation 1 is established. A(g) = 162 x + 192 x y + (145 + T) x z Equation 1

[0087] Furthermore, the Q (mol) previously determined by titration satisfies Equation 2: Q (mol) = 2y + z...Equation 2

[0088] The amount of carboxy groups in cellulose (mmol / g, symbolized as B) determined by the method described in the section [Amount of Carboxy Groups] above can be converted to y using Equation 3: y (mol) = B (mmol / g) × A (g) / 1000 × 1 / 2 Equation 3

[0089] Here, the degree of substitution is the value obtained by dividing the number of moles of introduced acyl groups by the total number of moles of glucopyranose rings, and can be calculated using Equation 4: Degree of substitution (dimensionless number) = z / (x + y + z) Equation 4

[0090] Using Equations 1 to 4 and rearranging them with A, B, Q, and T, the degree of substitution can be determined by the following Equation 5. The degree of substitution of each modified cellulose was calculated from Equation 5.

[0091] [Birefringence] (Preparation of mixed solution of cellulose and organic solvent) The cellulose obtained in each example and comparative example and various organic solvents were placed in a 9 mL vial to prepare 5 mL of mixed solution (cellulose concentration: 1% by mass). The mixed solution was defibrated for 1 minute using a laboratory-use high-power ultrasonic dispersion device (Hielscher UP-400s) and then diluted with the same organic solvent to obtain a mixed solution (cellulose concentration: 0.1% by mass).

[0092] (Preparation of a mixed solution of cellulose and water) The cellulose obtained in each Example and Comparative Example, water, and an aqueous solution (0.05N) of sodium hydroxide in an amount equivalent to the carboxyl groups of the cellulose were placed in a 9 mL vial to prepare 5 mL of a mixed solution (cellulose concentration: 1% by mass). The mixed solution was defibrated for 1 minute using a laboratory-use high-power ultrasonic dispersion device (Hielscher UP-400s) and then diluted with water to obtain a mixed solution (cellulose concentration: 0.1% by mass).

[0093] (Measurement of birefringence) Various mixed solutions (cellulose concentration: 0.1% by mass) were transferred to screw tubes and observed between crossed polarizing plates to visually confirm the presence or absence of birefringence. In the cases of the following evaluations A and B, it was determined that birefringence was present. The results are shown in Tables 1 and 2. (Evaluation criteria) A: Birefringence was clearly observable B: Hazy birefringence was observable C: Birefringence was not observable

[0094] [Light Transmittance] The light transmittance of the mixed solution (cellulose concentration: 0.1% by mass) obtained in the above [Birefringence] section was measured using a UV-Vis spectrophotometer. The optical path length of the glass cell was 10 mm, and the solvent used in each mixed solution was used as a standard sample. The value at 660 nm was read and used as the measurement result. The results are shown in Tables 1 and 2.

[0095] [Fiber length] The fiber length of the cellulose contained in the mixed solution (cellulose concentration: 0.1% by mass) obtained in the above [Birefringence] section was measured using a DLS measurement device (ELSZ-1000, manufactured by Otsuka Electronics Co., Ltd.). The optical path length of the glass cell was 10 mm, and the particle diameter corresponding to the median (D50) of the particle size distribution by the Marquardt method was used as the measurement result. The results are shown in Tables 1 and 2. Note that the fiber length was measured despite the birefringence rating being C. This is thought to be because some of the cellulose remained undissolved as fibrous material in the various mixed solutions and was measured.

[0096]

[0097]

Claims

1. A modified cellulose in which at least some of the hydroxyl groups of cellulose are modified with acyl groups, the modified cellulose having a structure in which the second and third hydroxyl groups of the glucopyranose ring are oxidized to introduce dicarboxy groups, the degree of modification of the hydroxyl groups with the acyl groups is within a range in which a mixture of the modified cellulose and an organic solvent exhibits birefringence and a light transmittance of 75% or more, and the organic solvent is at least one selected from the group consisting of acetone, methanol and ethyl acetate.

2. Modified cellulose in which at least some of the hydroxyl groups of cellulose are modified with acyl groups, the cellulose containing an oxide of a cellulose-based raw material with hypochlorous acid or a salt thereof and substantially free of N-oxyl compounds, the degree of modification of the hydroxyl groups with the acyl groups being within a range in which a mixture of the modified cellulose and an organic solvent exhibits birefringence and a light transmittance of 75% or more, and the organic solvent is at least one selected from the group consisting of acetone, methanol, and ethyl acetate.

3. The modified cellulose according to claim 1 or 2, wherein the modified cellulose is modified nanocellulose.

4. The modified cellulose according to claim 1 or 2, wherein the hydroxyl group modified with the acyl group is represented by the following formula (1): R-C(=O)-O- (1) [R is a hydrocarbon group].

5. The modified cellulose according to claim 4, wherein the hydrocarbon group has 1 to 8 carbon atoms.

6. Modified cellulose in which at least a portion of the hydroxyl groups of cellulose are modified with acyl groups, the cellulose having a structure in which the second and third hydroxyl groups of a glucopyranose ring are oxidized to introduce dicarboxy groups, and the hydroxyl groups modified with the acyl groups are represented by the following formula (1): R-C(=O)-O- (1) [R is a hydrocarbon group].

7. A modified cellulose in which at least a portion of hydroxyl groups of cellulose are modified with acyl groups, the cellulose comprising an oxidation product of a cellulose-based raw material with hypochlorous acid or a salt thereof and substantially free of N-oxyl compounds, the hydroxyl groups modified with the acyl groups being represented by the following formula (1): R-C(=O)-O- (1) [R is a hydrocarbon group].

8. A cellulose dispersion comprising the modified cellulose according to any one of claims 1, 2, 6 and 7, and an organic solvent.

9. A composition comprising the modified cellulose according to any one of claims 1, 2, 6 and 7, and a hydrophobic material.

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