Method for producing nanocellulose-containing composition

Abstract

The purpose of the present invention is to provide a method for efficiently manufacturing a nanocellulose-containing composition. The purpose can be fulfilled by means of a method for manufacturing a composition containing nanocellulose, the method including a step for, by agitating a mixture containing a cellulose oxide and components other than the nanocellulose constituting the composition, fibrillating the cellulose oxide into the nanocellulose, wherein the cellulose oxide contains an oxide of a cellulose-based raw material, the oxide being formed by means of hypochlorous acid or a salt thereof.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a nanocellulose-containing composition. [Background technology]

[0002] Various techniques have been proposed for producing nanocellulose materials such as cellulose nanofibers (hereinafter also referred to as "CNF") by oxidizing various cellulosic raw materials with an oxidizing agent and micronizing the resulting oxidized cellulose (see, for example, Patent Documents 1 and 2).

[0003] Patent Document 1 discloses a method for oxidizing a cellulosic raw material using hypochlorous acid or its salts as an oxidizing agent under high-concentration conditions of 14 to 43% available chlorine in the reaction system to obtain oxidized cellulose, which is then micronized to obtain CNF. Patent Document 2 also discloses a method for oxidizing a cellulosic raw material using hypochlorous acid or its salts as an oxidizing agent, maintaining an available chlorine concentration of 6 to 14% by mass in the reaction system while adjusting the pH to 5.0 to 14.0 to obtain oxidized cellulose, which is then micronized to obtain CNF. These techniques involve oxidation without using N-oxyl compounds such as 2,2,6,6-tetramethyl-1-piperidine-N-oxyl radical (TEMPO) as a catalyst, so that N-oxyl compounds do not remain in the cellulose fibers. This allows for the production of nanocellulose materials while minimizing environmental impact.

[0004] Patent Document 3 describes a production method including a step of obtaining a resin composition containing cellulose nanofibers and the defibrating resin by defibrating pulp having a cellulose polymerization degree of 100 to 500 in a defibrating resin. Patent Document 4 describes a method of producing a masterbatch containing acetylated cellulose nanofibers derived from acetylated cellulose fibers and a masterbatch resin by mixing acetylated cellulose fibers and a masterbatch resin and kneading the mixture in a twin-screw kneader at a heating temperature. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 230354 [Patent Document 2] International Publication No. 2020 / 027307 [Patent Document 3] International Publication No. 2015 / 068818 [Patent Document 4] Japanese Patent Publication No. 2020-128513 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Documents 1 and 2 disclose specific examples of producing nanocellulose materials by micronizing oxidized cellulose, in which nanocellulose material (also simply referred to as nanocellulose) is obtained through mechanical fiberization using an ultrasonic homogenizer. The nanocellulose obtained in this manner is blended with other materials to form composites for various applications. However, the mechanical fiberization process increases production costs and reduces production efficiency for nanocellulose obtained as described above. Therefore, when blending nanocellulose with other materials, there are issues with increased costs and efficiency, such as productivity, when producing blends.

[0007] Patent Documents 3 and 4 describe methods for defibrating pulp or acetylated cellulose fibers in a resin to produce cellulose nanofibers. However, the cellulose fibers used in these methods are pulp itself or modified cellulose fibers, and defibration requires an energy load, making it difficult to efficiently obtain a resin composition containing nanocellulose.

[0008] The present invention has been made in view of the above circumstances, and its main object is to provide a method for efficiently obtaining a nanocellulose-containing composition. [Means for solving the problem]

[0009] As a result of extensive research, the inventors discovered that by using a specific oxidized cellulose, it is possible to efficiently obtain a nanocellulose-containing composition without the need for the mechanical defibration process that finely refines the oxidized cellulose, and thus completed the present invention. According to the present invention, the following means are provided.

[0010] [1] A method for producing a composition containing nanocellulose, comprising: The method includes a step of defibrating the oxidized cellulose into the nanocellulose by stirring a mixture containing oxidized cellulose and components other than the nanocellulose that constitute the composition, The oxidized cellulose comprises an oxidation product of a cellulosic raw material with hypochlorous acid or a salt thereof. Manufacturing method. [2] The method according to [1], wherein the mixture further contains a dispersion medium. [3] A method for producing a composition containing nanocellulose, comprising: The method includes a step of defibrating the oxidized cellulose into the nanocellulose by stirring the oxidized cellulose, and subsequently adding components other than the nanocellulose that constitute the composition, The oxidized cellulose comprises an oxidation product of a cellulosic raw material with hypochlorous acid or a salt thereof. Manufacturing method. [4] The method according to [3], wherein the stirring of the oxidized cellulose and the addition of the components are carried out in one pot. [5] The method according to [3] or [4], wherein the oxidized cellulose is dispersed in a dispersion medium. [6] The method according to any one of [1] to [5], wherein the oxidized cellulose is substantially free of N-oxyl compounds. [7] The method according to any one of [1] to [6], wherein the degree of polymerization of the oxidized cellulose is 600 or less. [8] The manufacturing method according to any one of [1] to [7], wherein the light transmittance of the nanocellulose aqueous dispersion obtained by defibrating the aqueous dispersion of oxidized cellulose having a concentration of 0.1% by mass in a planetary centrifugal mixer at a revolution speed of 2000 rpm and a rotation speed of 800 rpm for 10 minutes is 60% or more. [9] The method according to any one of [1] to [8], wherein the stirring is carried out using a submerged disperser.

[10] The method according to any one of [1] to [9], wherein the component contains inorganic particles.

[11] The method according to any one of [1] to [9], wherein the component includes a resin or rubber, or a raw material monomer thereof.

[12] The manufacturing method according to any one of [1] to

[11] , wherein the total amount of the oxidized cellulose and the nanocellulose contained in the composition is 0.1 to 90 mass% based on the total mass of the components constituting the composition (excluding the solvent and dispersion medium). [Effects of the Invention]

[0011] According to the production method of the present invention, a nanocellulose-containing composition containing nanocellulose and a blend can be efficiently obtained.

[0012] The manufacturing method of the present invention is a method for manufacturing a nanocellulose-containing composition comprising nanocellulose and at least one compound. DETAILED DESCRIPTION OF THE INVENTION

[0013] One aspect of the manufacturing method of the present invention is The process involves a step of defibrating oxidized cellulose into nanocellulose by stirring a mixture containing oxidized cellulose and components other than nanocellulose that make up the composition (also referred to as the "blending"). The components stirred together with the oxidized cellulose may be some or all of the components that make up the composition (excluding nanocellulose). When some of the components are stirred together with the oxidized cellulose, the remaining components may be added after stirring. Furthermore, one aspect of the manufacturing method of the present invention is providing oxidized cellulose; obtaining a mixture of the oxidized cellulose and at least one compound; and Agitating the mixture to obtain a nanocellulose-containing composition. In this specification, the above-mentioned embodiment in which oxidized cellulose is defibrated in the presence of other components is also referred to as Production Method I. It is preferable that the composition in Production Method I does not consist of only nanocellulose and a dispersion medium.

[0014] One aspect of the manufacturing method of the present invention is The method includes a step of agitating the oxidized cellulose to defibrate it into nanocellulose, and subsequently mixing the components other than the nanocellulose that make up the composition. Furthermore, one aspect of the manufacturing method of the present invention is providing oxidized cellulose; agitating the oxidized cellulose and sequentially adding at least one compound to obtain a nanocellulose-containing composition. In this specification, the above embodiment in which oxidized cellulose is defibrated and then continuously mixed with other components is also referred to as Production Method II.

[0015] The oxidized cellulose in the present invention includes an oxidation product of a cellulosic raw material with hypochlorous acid or a salt thereof.

[0016] In conventional methods, even if chemical treatment, biological treatment, etc. are carried out as pretreatment before mechanical defibration treatment to obtain nanocellulose, mechanical defibration treatment is still carried out as the final step. The inventors have discovered that oxidized cellulose obtained by oxidizing cellulosic raw materials with hypochlorous acid or its salts has excellent defibration properties. Furthermore, the inventors have discovered that the oxidized cellulose can be converted to nanocellulose with only slight stirring, without the need for the mechanical defibration treatment equipment typically used to obtain nanocellulose. While nanocellulose has traditionally been used to mix or composite nanocellulose with other materials, the production method of the present invention converts the oxidized cellulose into nanocellulose by adding oxidized cellulose when dispersing or emulsifying the other materials and then slight stirring, thereby enabling the other materials to be mixed or composited with nanocellulose. As described above, the production method of the present invention is highly efficient, allowing nanocellulose-containing compositions to be obtained without the need for mechanical defibration.

[0017] In the production method of the present invention, at least a portion of the oxidized cellulose can be defibrated and refined by stirring. As a result, a nanocellulose-containing composition containing nanocellulose and at least one blend is obtained. The stirring method used in the present invention is not particularly limited as long as it can refine at least a portion of the oxidized cellulose, and any ordinary stirring method will do. Furthermore, the stirring method used in the present invention is not particularly limited as long as it is an operation that disperses the components that make up the nanocellulose-containing composition. Furthermore, the oxidized cellulose needs to be refined to an extent that the functionality of nanocellulose can be obtained, and some of the oxidized cellulose may remain unrefined. Therefore, the nanocellulose-containing composition obtained by the production method of the present invention may contain some oxidized cellulose.

[0018] In Production Method I of the present invention, when obtaining a mixture of oxidized cellulose and a compound, the order or method of adding these is not particularly limited.

[0019] In Production Method II of the present invention, oxidized cellulose is stirred while at least one compound is continuously added. More specifically, one embodiment of Production Method II of the present invention is a production method in which oxidized cellulose is stirred to micronize at least a portion, and then at least one compound is continuously added. Here, "continuously" means that the micronization of at least a portion of the oxidized cellulose by stirring and the addition of the compound are carried out in succession. Specific embodiments in which stirring and the addition of the compound are carried out in succession include, but are not limited to, a one-pot operation in which oxidized cellulose is stirred to micronize it and at least one compound is added; and an embodiment in which at least one compound is added simultaneously while oxidized cellulose is stirred. In this way, users of oxidized cellulose can obtain nanocellulose by micronizing it themselves and use it.

[0020] As described above, the stirring in the present invention is not particularly limited as long as it is an operation that disperses the components that make up the nanocellulose-containing composition, and can utilize, for example, a velocity field and velocity fluctuation of any intensity; collision with inclusions or obstacles; ultrasound; pressure loading; etc. A submerged disperser can be suitably used for such a dispersing operation. Therefore, one aspect of the production method of the present invention is a production method in which stirring is performed using a submerged disperser.

[0021] The submerged disperser is not particularly limited, and examples thereof include methods using a homomixer, a magnetic stirrer, a stirring rod, a stirrer with stirring blades, a disperser-type mixer, a homogenizer, an external circulation stirrer, a planetary stirrer, a vibration stirrer, an ultrasonic disperser, etc. In addition to the above-mentioned devices, examples of the submerged disperser include a rotary shear type stirrer, a colloid mill, a roll mill, a pressure homogenizer, a container-driven mill, a media stirring mill, etc. Furthermore, a kneader can be used as the submerged disperser.

[0022] A rotary shear agitator is a device that disperses materials by passing them through the gap between a rotor and an outer cylinder. Dispersion occurs due to shear flow in the gap and strong speed fluctuations between the front and rear. The peripheral speed of the rotor at the tip of the blade is not particularly limited, but is usually 100 m / s or less. From the viewpoint of cost and production efficiency, the peripheral speed is preferably 50 m / s or less, more preferably 30 m / s or less, and even more preferably 15 m / s or less. The lower limit of the peripheral speed is not particularly limited, but is usually greater than 0 m / s.

[0023] A colloid mill is a device that disperses materials by shear flow in the gap between a rotating disk and a fixed disk, while a roll mill is a device that disperses materials by shear and compression forces using the gap between multiple rotating rolls.

[0024] A pressure homogenizer is used as a disperser that ejects a slurry or the like from fine holes at high pressure, and is also called a pressure injection disperser. As the pressure homogenizer, a high-pressure homogenizer is preferred. A high-pressure homogenizer refers to a homogenizer capable of ejecting a slurry at a pressure of, for example, 10 MPa or more, preferably 100 MPa or more. The upper limit of the pressure of the high-pressure homogenizer is not particularly limited, but may be 400 MPa or less. Furthermore, from the viewpoint of cost and production efficiency, the upper limit of the pressure of the high-pressure homogenizer is preferably 200 MPa or less, more preferably 100 MPa or less, even more preferably 50 MPa or less, and even more preferably 30 MPa or less. Examples of high-pressure homogenizers include opposed collision-type high-pressure homogenizers such as microfluidizers and wet jet mills.

[0025] A container-driven mill is a device that disperses by collision and friction of media such as balls in a container, and specific examples include a rotary mill, a vibration mill, and a planetary mill.

[0026] A media agitation mill is a device that uses media such as balls or beads to disperse materials by the impact and shear forces of the media, and specific examples include an attritor and a bead mill (sand mill).

[0027] A kneader is a device used to wet powders and other materials with a liquid (also known as kneading or kneading).Specific examples include twin-arm kneaders (devices that disperse materials using two mixing blades inside two semi-cylindrical containers); Banbury mixers (devices that disperse materials under pressure in a closed system); and extrusion-type kneaders such as screw extruders, co-kneaders, and extruders.

[0028] These devices may be used alone or in combination of two or more.

[0029] Although stirring using such an apparatus can promote the refinement of oxidized cellulose, stirring may be continued until the components of the nanocellulose-containing composition are homogenized or emulsified, which allows the nanocellulose to be uniformly dispersed in the nanocellulose-containing composition and also allows the nanocellulose-containing composition to be obtained as an emulsion.

[0030] Stirring is preferably carried out in a state in which the oxidized cellulose is mixed with a dispersion medium. Therefore, it is preferable that the mixture containing oxidized cellulose and at least one compound in Production Method I further contains a dispersion medium. Also, it is preferable that the oxidized cellulose in Production Method II is dispersed in a dispersion medium. The dispersion medium is not particularly limited and can be appropriately selected depending on the purpose. Specific examples of the dispersion medium include water, alcohols, ethers, ketones, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. As the solvent, one of these may be used alone, or two or more may be used in combination.

[0031] Among the dispersion media, examples of alcohols include methanol, ethanol, isopropanol, isobutanol, sec-butyl alcohol, tert-butyl alcohol, methyl cellosolve, ethylene glycol, and glycerin. Examples of ethers include ethylene glycol dimethyl ether, 1,4-dioxane, and tetrahydrofuran. Examples of ketones include acetone and methyl ethyl ketone.

[0032] When a dispersing medium is included, the concentration of oxidized cellulose during stirring can be adjusted as appropriate depending on the stirring equipment and type of compound, but is typically in the range of 0.01% by mass or more and 30% by mass or less, preferably more than 1.0% by mass and 30% by mass or less, more preferably 1.5% by mass or more and 20% by mass or less, and even more preferably 1.5% by mass or more and 15% by mass or less, based on the total amount of the object to be stirred (in Production Method I, this refers to a mixture containing oxidized cellulose, at least one compound, and a dispersing medium, and in Production Method II, this refers to a dispersion containing oxidized cellulose and a dispersing medium).

[0033] When a homomixer is used for mixing, the rotation speed is usually 100 rpm to 1,000 x 10 3 The rotation speed is preferably in the range of 1,000 to 100,000 rpm. From the viewpoint of more efficient micronization, the rotation speed is preferably in the range of 1,000 to 100,000 rpm. The stirring time is not particularly limited, but from the viewpoint of productivity, it is preferably in the range of 1 minute to 1 hour. When a homomixer is used for stirring, the concentration of oxidized cellulose is preferably in the range of 0.1 to 30% by mass relative to the total amount of the object to be stirred. By keeping the concentration of oxidized cellulose in the range of 0.1 to 30% by mass, micronization tends to proceed more easily and a nanocellulose-containing composition tends to be obtained more efficiently. From the same viewpoint, the concentration of oxidized cellulose is more preferably more than 1.0% by mass and not more than 30% by mass, even more preferably 1.5% to 20% by mass, and even more preferably 1.5% to 15% by mass.

[0034] A planetary centrifugal mixer is a device that mixes materials in a container by rotating and revolving the container around its axis. A planetary centrifugal mixer allows mixing without the use of stirring blades. The revolution speed and rotation speed during mixing can be set appropriately; for example, the revolution speed can be set to 400-3000 rpm and the rotation speed to 200-1500 rpm. When using a planetary centrifugal mixer, in order to ensure uniform quality while achieving gentle mixing, mixing is preferably performed under conditions of a revolution speed of 1200-2500 rpm and a rotation speed of 600-1000 rpm for 3-15 minutes. The revolution speed is more preferably 1500-2300 rpm, and the rotation speed is more preferably 700-950 rpm. When mixing is performed using a planetary centrifugal mixer, the concentration of oxidized cellulose is, for example, 0.01-1.0% by mass, preferably 0.1-0.5% by mass.

[0035] An example of a vibration-type agitator is a vortex mixer (touch mixer). In a vortex mixer, agitation is performed by forming a vortex in the liquid material in a container. A vibration-type agitator such as a vortex mixer performs agitation without using a stirring blade, thereby achieving gentler agitation. Furthermore, a vibration-type agitator such as a vortex mixer can achieve gentle agitation with simple equipment, making it advantageous in terms of production equipment and production costs. The rotation speed of the vortex mixer is, for example, 600 to 3000 rpm, and stirring is preferably performed for 3 to 15 minutes. When agitation is performed using a vortex mixer, the concentration of the oxidized cellulose aqueous dispersion used as the raw material is, for example, 0.01 to 1.0% by mass, and preferably 0.1 to 0.5% by mass.

[0036] <Oxidized cellulose> The process for preparing oxidized cellulose in the present invention is not particularly limited, and oxidized cellulose may be obtained as a commercially available product or may be prepared by oxidizing a cellulosic raw material with hypochlorous acid or a salt thereof. The oxidized cellulose may be in the form of, for example, a solid (dried) form or a slurry form. While not particularly limited, the form of a slurry is preferred. That is, the oxidized cellulose is preferably prepared as a slurry. The term "slurry" as used herein refers to a suspension containing oxidized cellulose. The slurry may contain the solvent used in preparing the oxidized cellulose. Furthermore, the above-mentioned dispersion medium may be added appropriately to form a slurry. When the oxidized cellulose is in the form of a slurry, it is easier to handle and tends to be more easily micronized. When the oxidized cellulose of the present invention is in the form of a slurry, the amount of oxidized cellulose is typically in the range of 0.1% to 95% by mass, preferably 1% to 50% by mass, and more preferably 1% to 30% by mass, when the total amount of the slurry is taken as 100% by mass.

[0037] The oxidized cellulose of the present invention includes fibrous cellulose obtained by oxidizing a cellulosic raw material with hypochlorous acid or a salt thereof. Oxidized cellulose refers to an oxide of a cellulosic raw material prior to defibration (micronization). The oxidized cellulose of the present invention is also referred to as oxidized cellulose fiber. That is, the oxidized cellulose of the present invention includes an oxide of a cellulosic raw material with hypochlorous acid or a salt thereof. Note that the main component of plants is cellulose, and bundles of cellulose molecules are called cellulose microfibrils. The cellulose in the cellulosic raw material is also contained in the form of cellulose microfibrils.

[0038] (Degree of polymerization) In one embodiment of the present disclosure, the degree of polymerization of the oxidized cellulose may be 600 or less. When the degree of polymerization of oxidized cellulose is 600 or less, there is a tendency that large amounts of energy are not required for defibration, and sufficient easy defibration properties are likely to be exhibited. As a result, it tends to be pulverized under mild conditions and can be pulverized by ordinary stirring or kneading, and a nanocellulose-containing composition tends to be obtained efficiently. From the viewpoint of easy defibration properties, no particular lower limit is set for the degree of polymerization of the oxidized cellulose. Furthermore, when the degree of polymerization of oxidized cellulose is 30 or more, the proportion of particulate cellulose rather than fibrous cellulose decreases, the quality of the slurry containing oxidized cellulose becomes uniform and the viscosity becomes stable, and thixotropy, one of the characteristics of nanocellulose, is more likely to be obtained. From the above viewpoints, the degree of polymerization of oxidized cellulose is preferably 30 to 600.

[0039] The degree of polymerization is more preferably 580 or less, even more preferably 560 or less, even more preferably 550 or less, still more preferably 500 or less, even more preferably 450 or less, and even more preferably 400 or less. From the viewpoint of improving the viscosity stability of the slurry, the lower limit of the degree of polymerization is more preferably 50 or more, even more preferably 60 or more, even more preferably 70 or more, even more preferably 80 or more, even more preferably 90 or more, even more preferably 100 or more, particularly preferably 110 or more, and most preferably 120 or more. A preferred range of the degree of polymerization can be determined by appropriately combining the above-mentioned upper and lower limits. The degree of polymerization of oxidized cellulose is more preferably 50 to 600, even more preferably 60 to 600, even more preferably 80 to 600, even more preferably 80 to 550, even more preferably 80 to 500, even more preferably 80 to 450, and particularly preferably 80 to 400.

[0040] The degree of polymerization of oxidized cellulose can be adjusted by changing the reaction time, reaction temperature, pH, and available chlorine concentration of hypochlorous acid or its salt during the oxidation reaction. Specifically, since the degree of polymerization tends to decrease as the degree of oxidation increases, methods for decreasing the degree of polymerization include increasing the oxidation reaction time and / or reaction temperature. Alternatively, the degree of polymerization of oxidized cellulose can be adjusted by adjusting the stirring conditions of the reaction system during the oxidation reaction. For example, under conditions where the reaction system is sufficiently homogenized using a stirring blade or the like, the oxidation reaction proceeds smoothly and the degree of polymerization tends to decrease. On the other hand, under conditions where the reaction system is likely to be insufficiently stirred, such as stirring with a stirrer, the reaction tends to become non-uniform, making it difficult to sufficiently reduce the degree of polymerization of oxidized cellulose. Furthermore, the degree of polymerization of oxidized cellulose tends to vary depending on the selection of the cellulosic raw material. Therefore, the degree of polymerization of oxidized cellulose can also be adjusted by selecting the cellulosic raw material. In this specification, the degree of polymerization of oxidized cellulose is the average degree of polymerization (viscosity-average degree of polymerization) measured by a viscosity method. Details are given in accordance with the method described in the Examples below.

[0041] (carboxyl group amount) The amount of carboxy groups in the oxidized cellulose is preferably 0.30 to 2.0 mmol / g. A carboxy group amount of 0.30 mmol / g or more can impart sufficient defibrability to the oxidized cellulose. This allows for micronization under mild conditions, and tends to be achieved by ordinary stirring or kneading. On the other hand, a carboxy group amount of 2.0 mmol / g or less can prevent excessive decomposition of the oxidized cellulose when blended with other components, resulting in nanocellulose of uniform quality with a low proportion of particulate cellulose. From this perspective, the amount of carboxy groups in the oxidized cellulose is more preferably 0.35 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.42 mmol / g or more, even more preferably 0.50 mmol / g or more, even more preferably greater than 0.50 mmol / g, even more preferably 0.55 mmol / g or more, and even more preferably 0.60 mmol / g. The upper limit of the carboxyl group content is more preferably 1.5 mmol / g or less, even more preferably 1.2 mmol / g, even more preferably 1.0 mmol / g or less, even more preferably 0.9 mmol / g, and even more preferably 0.80 mmol / g or less. A preferred range of the carboxyl group content can be determined by appropriately combining the above-mentioned upper and lower limits. The carboxyl group content of the present oxidized cellulose is more preferably 0.35 to 2.0 mmol / g, even more preferably 0.35 to 1.5 mmol / g, even more preferably 0.40 to 1.5 mmol / g, even more preferably 0.50 to 1.2 mmol / g, even more preferably greater than 0.50 to 1.2 mmol / g, even more preferably 0.55 to 1.0 mmol / g, and even more preferably 0.60 to 0.80 mmol / g.

[0042] The amount of carboxy groups (mmol / g) in oxidized cellulose was calculated using the following formula from the amount of sodium hydroxide (a) consumed in the neutralization stage of the weak acid, where the change in electrical conductivity is gradual, after adding 0.1 M (hereinafter also referred to as mol / L) hydrochloric acid aqueous solution to an aqueous solution prepared by mixing oxidized cellulose with water to adjust the pH to 2.5, adding 0.05 N sodium hydroxide aqueous solution dropwise, and measuring the electrical conductivity until the pH reaches 11.0. The amount of carboxy groups in oxidized cellulose can be adjusted by changing the reaction time, reaction temperature, pH of the reaction solution, etc. of the oxidation reaction. Amount of carboxyl group = a (ml) x 0.05 / mass of oxidized cellulose (g)

[0043] Specifically, the amount of carboxy groups can be measured according to the method described in the Examples below.

[0044] Furthermore, in one embodiment of the oxidized cellulose used in the present invention, a nanocellulose aqueous dispersion obtained by defibrating a 0.1% by mass aqueous dispersion of the oxidized cellulose in a planetary centrifugal mixer at a revolution speed of 2000 rpm and a rotation speed of 800 rpm for 10 minutes preferably exhibits a light transmittance of 60% or greater. The light transmittance of this nanocellulose aqueous dispersion is more preferably 70% or greater, even more preferably 75% or greater, and even more preferably 80% or greater. The light transmittance is measured at a wavelength of 660 nm using a spectrophotometer. Specifically, the light transmittance can be measured according to the method described in the Examples below.

[0045] Furthermore, the oxidized cellulose used in the present invention is preferably a nanocellulose aqueous dispersion obtained by defibrating a 0.1% by mass aqueous dispersion of the oxidized cellulose in a vortex mixer at 3000 rpm for 10 minutes, and the optical transmittance of this nanocellulose aqueous dispersion is preferably 60% or higher. The optical transmittance of this nanocellulose aqueous dispersion is more preferably 70% or higher, even more preferably 75% or higher, and even more preferably 80% or higher.

[0046] The oxidized cellulose of the present invention is obtained by oxidation using hypochlorous acid or a salt thereof. The oxidized cellulose thus obtained preferably has a structure in which at least two of the hydroxyl groups on the glucopyranose ring that constitutes the cellulose have been oxidized, more specifically, the hydroxyl groups at the second and third positions on the glucopyranose ring have been oxidized and a carboxyl group has been introduced. Furthermore, it is preferable that the hydroxyl group at the sixth position on the glucopyranose ring in the nanocellulose or oxidized cellulose is not oxidized and remains as a hydroxyl group. The position of the carboxyl group on the glucopyranose ring of oxidized cellulose can be determined by the solution NMR spectrum using oxidized rayon as a model molecule and the solid NMR spectrum of oxidized cellulose. 13 It can be analyzed by comparing C-NMR spectra.

[0047] Rayon has the same chemical structure as cellulose, and its oxide (rayon oxide) is water-soluble. 13 C-NMR measurements reveal a carbon peak attributable to carboxy groups at 165 to 185 ppm. In one embodiment of the oxidized cellulose or nanocellulose used in the present invention, obtained by oxidizing a cellulosic raw material with hypochlorous acid or its salt, two signals appear within this chemical shift range. Furthermore, solution two-dimensional NMR measurements reveal that the carboxy groups are introduced at the 2- and 3-positions.

[0048] Oxidized cellulose or nanocellulose solid obtained by oxidizing 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 this is difficult to achieve with low-resolution solid state spectroscopy. 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. 13In the C-NMR spectrum, the introduction of carboxy groups at the 2nd and 3rd positions can be confirmed by evaluating the broadening of the peaks appearing at 165 to 185 ppm.

[0049] That is, solid 13 A baseline is drawn around the peak in the range of 165 ppm to 185 ppm in the 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 ​​(large area value / small area value). If the ratio of the peak area values ​​is 1.2 or more, the peak can be said to be broad. The presence or absence of the 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 more, it can be determined that a broad peak is present. The ratio L' / L may be 0.2 or more, 0.3 or more, 0.4 or more, or even 0.5 or more. There is no particular upper limit to the ratio L' / L, but it is usually 3.0 or less, and may be 2.0 or less, or 1.0 or less.

[0050] 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.

[0051] When the nanocellulose or oxidized cellulose used in the present invention contains a carboxyl group, it may be in the salt form, proton form, or modified form with a modifying group. The modifying group is not particularly limited, as long as it is a compound capable of forming an ionic or covalent bond with the carboxyl or hydroxyl group of the nanocellulose or oxidized cellulose. The physical properties of the nanocellulose or oxidized cellulose can be adjusted by adjusting the form of the carboxyl group. Examples of compounds having a modifying group capable of forming an ionic bond include primary amines, secondary amines, tertiary amines, quaternary ammonium compounds, and phosphonium compounds. Examples of compounds having a modifying group capable of forming a covalent bond include alcohols, isocyanate compounds, and epoxy compounds.

[0052] The oxidized cellulose of the present invention is prepared without the need for N-oxyl compounds such as TEMPO. There are concerns about the impact of N-oxyl compounds on the environment and the human body. For this reason, the oxidized cellulose and nanocellulose of the present invention are preferably substantially free of N-oxyl compounds. Herein, "substantially free of N-oxyl compounds" in the oxidized cellulose or nanocellulose means that no N-oxyl compounds are used during oxidation, or that the content of nitrogen derived from N-oxyl compounds in the oxidized cellulose or nanocellulose is 2.0 ppm by mass or less, preferably 1.0 ppm by mass or less, as increased from the cellulosic raw material. Furthermore, "substantially free of N-oxyl compounds" also means that the content of N-oxyl compounds is preferably 2.0 ppm by mass or less, more preferably 1.0 ppm by mass or less, as increased from the cellulosic raw material. The residual nitrogen component can be measured using a trace total nitrogen analyzer, and more specifically, can be measured by the method described in the Examples.

[0053] (Method of producing oxidized cellulose) Next, a method for producing oxidized cellulose will be described. Oxidized cellulose can be produced by a method including a step of oxidizing a cellulosic raw material with hypochlorous acid or a salt thereof.

[0054] 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, regenerated cellulose, and fine cellulose obtained by depolymerizing cellulose through mechanical processing. Commercially available cellulosic raw materials, such as crystalline cellulose derived from pulp, can be used as they are. Alternatively, unused biomass containing a large amount of cellulose components, such as soybean pulp refuse or soybean hulls, can also be used as the raw material. Furthermore, the cellulosic raw material may be pre-treated with an alkali of an appropriate concentration in order to facilitate the penetration of the oxidizing agent used into the raw pulp.

[0055] In the production method of the present invention, it is preferable to use fine cellulose obtained by mechanically or chemically treating cellulose as the cellulosic raw material. Pulp powder is a suitable example of fine cellulose. The use of pulp powder promotes further pulverization, tending to result in efficient production of nanocellulose. The particle size of the pulp powder is typically in the range of 1 to 1000 μm, preferably in the range of 1 to 500 μm, and more preferably in the range of 1 to 100 μm. The particle size referred to here is the average particle size, and refers to the value at which the volume accumulation distribution is 50% when the particle size distribution is expressed as a volume accumulation distribution using a laser scattering method as the measurement principle.

[0056] Examples of hypochlorous acid or a salt thereof used for oxidizing a cellulosic raw material include hypochlorous acid water, sodium hypochlorite, potassium hypochlorite, calcium hypochlorite, and ammonium hypochlorite. Among these, sodium hypochlorite is preferred from the viewpoint of ease of handling.

[0057] One method for producing oxidized cellulose by oxidation of a cellulosic raw material is to mix the cellulosic raw material with a reaction solution containing hypochlorous acid or a salt thereof. The solvent contained in the reaction solution is preferably water, as it is easy to handle and is less likely to cause side reactions. In the oxidation, it is preferable to use hypochlorous acid or a salt thereof with an available chlorine concentration of 6% by mass or more and 43% by mass or less. By using hypochlorous acid or a salt thereof with an available chlorine concentration of 6% by mass or more and 43% by mass or less, the amount of carboxy groups in the oxidized cellulose can be sufficiently increased, allowing for sufficient pulverization, and making it possible to omit the mechanical fiberization treatment that follows the oxidation reaction. The available chlorine concentration of hypochlorous acid or a salt thereof in the reaction liquid (reaction system) is also preferably in the range of 6 to 43 mass %.

[0058] From the viewpoint of smoothly proceeding with the micronization of oxidized cellulose, the available chlorine concentration is more preferably 7% by mass or more, even more preferably 10% by mass or more, even more preferably 14% by mass or more, even more preferably 15% by mass or more, even more preferably 18% by mass or more, and even more preferably 20% by mass or more. Furthermore, from the viewpoint of suppressing excessive decomposition of cellulose, the available chlorine concentration of the reaction solution is more preferably 40% by mass or less, even more preferably 38% by mass or less. The range of the available chlorine concentration of the reaction solution can be an appropriate combination of the above-mentioned lower and upper limits. The range of the available chlorine concentration is more preferably 7 to 43% by mass, even more preferably 14 to 43% by mass.

[0059] The available chlorine concentration of hypochlorous acid or its salts is defined as follows: Hypochlorous acid is a weak acid that exists as an aqueous solution, and hypochlorite is a compound in which the hydrogen of hypochlorous acid is replaced by another cation. For example, sodium hypochlorite, a hypochlorite, exists in a solvent (preferably in an aqueous solution), so the concentration is measured as the amount of available chlorine in the solution, not the concentration of sodium hypochlorite. Here, with regard to the available chlorine of sodium hypochlorite, the oxidizing power of the divalent oxygen atom generated by the decomposition of sodium hypochlorite is equivalent to two atomic equivalents of monovalent chlorine, so the bonded chlorine atoms of sodium hypochlorite (NaClO) have the same oxidizing power as two atoms of unbonded chlorine (Cl2), and the available chlorine = 2 × (chlorine in NaClO). The specific measurement procedure is as follows: First, the sample is precisely weighed, and water, potassium iodide, and acetic acid are added and left to stand. The liberated iodine is titrated with a sodium thiosulfate solution using a starch aqueous solution as an indicator to measure the available chlorine concentration.

[0060] The oxidation reaction of the cellulosic raw material with hypochlorous acid or a salt thereof is preferably carried out while adjusting the pH to a range of 5.0 or higher. Within this range, the oxidation reaction of the cellulosic raw material can proceed sufficiently, the amount of carboxy groups in the oxidized cellulose becomes sufficiently large, and pulverization by stirring tends to proceed easily. The pH of the reaction system is more preferably 7.0 or higher, and even more preferably 8.0 or higher. There is no particular upper limit to the pH of the reaction system, but it is preferably 14.5 or lower, more preferably 14.0 or lower, and even more preferably 13.0 or lower. The pH range of the reaction system is more preferably 7.0 to 14.0, and even more preferably 8.0 to 13.5.

[0061] Hereinafter, the method for producing oxidized cellulose will be further explained using as an example the case where sodium hypochlorite is used as hypochlorous acid or a salt thereof.

[0062] When oxidizing a cellulosic raw material using sodium hypochlorite, the reaction liquid is preferably a sodium hypochlorite aqueous solution. Methods for adjusting the effective chlorine concentration of a sodium hypochlorite aqueous solution to a target concentration (for example, target concentration: 6% by mass to 43% by mass) include concentrating a sodium hypochlorite aqueous solution having a lower effective chlorine concentration than the target concentration, diluting a sodium hypochlorite aqueous solution having a higher effective chlorine concentration than the target concentration, and dissolving sodium hypochlorite crystals (for example, sodium hypochlorite pentahydrate) in a solvent. Among these, the method of diluting a sodium hypochlorite aqueous solution or dissolving sodium hypochlorite crystals in a solvent to adjust the effective chlorine concentration as an oxidizing agent is preferred because it causes less self-decomposition (i.e., less reduction in effective chlorine concentration) and is easy to adjust the effective chlorine concentration.

[0063] The method for mixing the cellulosic raw material with the aqueous sodium hypochlorite solution is not particularly limited, but from the viewpoint of ease of operation, it is preferable to add the cellulosic raw material to the aqueous sodium hypochlorite solution and mix them.

[0064] To efficiently promote the oxidation reaction of the cellulosic raw material, it is preferable to stir the mixture of the cellulosic raw material and the aqueous sodium hypochlorite solution during the oxidation reaction. Examples of stirring methods include a magnetic stirrer, a stirring rod, a stirrer with stirring blades (Three-One Motor), a homomixer, a disperser-type mixer, a homogenizer, and external circulation stirring. Among these, methods using one or more of shear-type stirrers such as homomixers and homogenizers, stirrers with stirring blades, and disperser-type mixers are preferred, as they allow the oxidation reaction of the cellulosic raw material to proceed smoothly and make it easy to adjust the degree of polymerization of oxidized cellulose to a predetermined value or less. Methods using a stirrer with stirring blades are particularly preferred. When using a stirrer with stirring blades, devices equipped with known stirring blades such as propeller blades, paddle blades, and turbine blades can be used. Furthermore, when using a stirrer with stirring blades, stirring is preferably performed at a rotation speed of 50 to 300 rpm.

[0065] The reaction temperature in the oxidation reaction is preferably 15°C to 100°C, and more preferably 20°C to 90°C. During the reaction, the pH of the reaction system decreases as carboxyl groups are generated in the cellulosic raw material by the oxidation reaction. Therefore, from the viewpoint of efficiently progressing the oxidation reaction, it is preferable to add an alkaline agent (e.g., sodium hydroxide) or an acid (e.g., hydrochloric acid) to the reaction system and carry out the oxidation reaction while adjusting the pH of the reaction system. The reaction time for the oxidation reaction can be set according to the degree of progress of the oxidation, but is preferably about 15 minutes to 50 hours. When the pH of the reaction system is to be 10 or higher, it is preferable to set the reaction temperature to 30°C or higher and / or the reaction time to 30 minutes or longer.

[0066] The concentration of the cellulosic raw material during the oxidation reaction is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total amount of the reaction mixture during the oxidation reaction, from the viewpoint of improving workability, such as facilitating stirring during the oxidation reaction, and from the viewpoint of promoting pulverization. The lower limit of the concentration of the cellulosic raw material during the oxidation reaction is usually 0.1% by mass or more, and from the viewpoint of productivity, it is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. The concentration of the cellulosic raw material during the oxidation reaction is preferably in the range of 0.1% by mass or more to 30% by mass or less, more preferably 1% by mass or more to 20% by mass or less, and even more preferably 1% by mass or more to 10% by mass or less.

[0067] In the production of oxidized cellulose, after the oxidization of the cellulosic raw material, a treatment to terminate the oxidation reaction may be carried out. The treatment to terminate the oxidation reaction is not particularly limited, but examples thereof include a method of adding an acid or a metal catalyst. Another preferred example is a method of reducing hypochlorous acid or a salt thereof. Specific examples of treatment to terminate the oxidation reaction include a method of adding a reducing agent such as sodium sulfite. The amount of reducing agent added may be adjusted appropriately depending on the amount of hypochlorous acid or a salt thereof (available chlorine concentration).

[0068] The solution containing oxidized cellulose obtained by the above reaction can be subjected to known isolation processes such as centrifugation and filtration, and further purified as necessary to obtain oxidized cellulose as an oxide of a cellulosic raw material with hypochlorous acid or a salt thereof. Alternatively, the solution containing oxidized cellulose obtained by the above reaction can be directly subjected to the next step.

[0069] <Composition> The nanocellulose-containing composition of the present invention contains at least one compound other than nanocellulose. In the present invention, the compound refers to any material to be mixed or composited with nanocellulose. The compound may be any material, and may be organic or inorganic, and may be solid or liquid. The compound may be selected appropriately depending on the application of the nanocellulose-containing composition.

[0070] Nanocellulose is used in, for example, resins, fibers, rubber, food, cosmetics, medical products, paints, inks, sheet films, moldings, or inorganic materials, but its uses are not limited to these. Therefore, the nanocellulose-containing composition can be used in applications such as resins, fibers, rubber, food, cosmetics, medical products, paints, inks, sheet films, moldings, or inorganic materials, or as an intermediate in the production of these applications. That is, examples of uses of the nanocellulose-containing composition include resins, fibers, rubber, food, cosmetics, medical products, paints, inks, sheet films, moldings, or inorganic materials containing the nanocellulose-containing composition, or nanocellulose-containing compositions for forming resins, fibers, rubber, food, cosmetics, medical products, paints, inks, sheet films, moldings, or inorganic materials. The formulation may be any component that can be included in these applications or intermediates for these applications.

[0071] Nanocellulose can be used, for example, to improve the functionality of resins or rubbers by incorporating it therein. Therefore, the manufacturing method of the present invention can be applied to the manufacture of resins or rubbers, for example. When the nanocellulose-containing composition is used for resin or rubber, the compound may be the resin or rubber itself, or it may be the raw material monomer for the resin or rubber before polymerization.

[0072] The resin to which the production method of the present invention can be applied is not particularly limited, and examples thereof include polymers of ethylenically unsaturated monomers, etc. In this case, either a polymer of an ethylenically unsaturated monomer or an ethylenically unsaturated monomer may be used as the blend. Specific examples of the ethylenically unsaturated monomer include (meth)acrylic acid, alkyl (meth)acrylate, alkylene glycol (meth)acrylate, (meth)acrylonitrile, vinyl halide, maleic acid imide, phenylmaleimide, (meth)acrylamide, styrene, α-methylstyrene, vinyl acetate, etc. Examples of the alkyl (meth)acrylate include those having an alkyl moiety with 1 to 10 carbon atoms. The alkyl moiety may be linear, branched, or cyclic, and may be unsubstituted or substituted. The ethylenically unsaturated monomer may have a functional group such as a carboxyl group, a hydroxyl group, an epoxy group, an amino group, an amide group, or a cyano group. Having these functional groups enhances affinity for nanocellulose. On the other hand, to avoid difficulty in emulsification or dispersion and unstable polymerization, the proportion of ethylenically unsaturated monomers having these functional groups is preferably 5 mol % or less, more preferably 3 mol % or less, and even more preferably 1 mol % or less of the total ethylenically unsaturated monomers.

[0073] The weight-average molecular weight of the polymer of the ethylenically unsaturated monomer is not particularly limited. For example, it may be 5,000 to 3,000,000. When the weight-average molecular weight of the particulate polymer is 5,000 or more, a decrease in the strength of the resin is suppressed, and when the weight-average molecular weight of the particles is 3,000,000 or less, the particles tend to melt easily in the resin, resulting in a sufficient modification effect. Specifically, the weight average molecular weight (Mw) of the polymer of the ethylenically unsaturated monomer can be measured by the following method. The weight-average molecular weight of the polymer of the ethylenically unsaturated monomer is measured using GPC (gel permeation chromatography, e.g., HLC-8220, manufactured by Tosoh Corporation). Specifically, an appropriate solvent is added to a resin modifier containing nanocellulose and a polymer of the ethylenically unsaturated monomer to dissolve the polymer. The solution is then filtered using a 0.45 μm filter, and the resulting solution is measured in terms of polystyrene.

[0074] The nanocellulose of the present invention has carboxyl groups. At least a portion of the carboxyl groups in the nanocellulose contained in the nanocellulose-containing composition may be modified. Therefore, the compound may be a compound that modifies the carboxyl groups. Examples of such compounds include amines and quaternary ammonium salts. When the nanocellulose-containing composition is in the form of a resin, the nanocellulose is modified by reacting with the carboxyl groups on the surface of the nanocellulose, improving the hydrophobicity of the nanocellulose and its affinity for monomers or resins.

[0075] The amine used to modify nanocellulose is not particularly limited and may be primary, secondary, or tertiary. The number of carbon atoms in the hydrocarbon or aromatic group bonded to the nitrogen atom of the amine or quaternary ammonium salt compound (when two or more hydrocarbon or aromatic groups are bonded to the nitrogen atom, the total carbon number) is not particularly limited and may be selected from between 1 and 100 carbon atoms. As the amine, an amine having a polyalkylene oxide structure such as an ethylene oxide / propylene oxide (EO / PO) copolymer moiety may be used. From the viewpoint of imparting sufficient hydrophobicity to nanocellulose, the number of carbon atoms is preferably 3 or more, and more preferably 5 or more.

[0076] The quaternary ammonium salt compound that modifies nanocellulose is not particularly limited. Specific examples of the quaternary ammonium salt compound include quaternary ammonium hydroxides such as tetrabutylammonium hydroxide, quaternary ammonium chlorides such as tetrabutylammonium chloride, quaternary ammonium bromides such as tetrabutylammonium bromide, and quaternary ammonium iodides such as tetrabutylammonium iodide.

[0077] The amine or quaternary ammonium may be a compound, but the timing of its addition in the production method of the present invention is not particularly limited. In Production Method I, the amine or quaternary ammonium may be included in a mixture of oxidized cellulose and at least one compound (i.e., an embodiment in which the compound is an amine or quaternary ammonium), or may be added after stirring the mixture. In Production Method II, the oxidized cellulose may be stirred, and then the amine or quaternary ammonium may be added as at least one compound.

[0078] Nanocellulose may be used, for example, to disperse components that may be included in the above-mentioned applications. Suitable examples of such components include inorganic particles. The inorganic particles may be inorganic fine particles. The inorganic particles may be used in combination with nanocellulose, not limited to the above-mentioned applications. Inorganic particles that can be used in combination with nanocellulose are not particularly limited, and examples include metal elements such as copper, silver, nickel, palladium, carbon, silicon, aluminum, zinc, and platinum, as well as metal compounds containing at least one of these metals. The metal compounds may be oxides, chlorides, halides (bromides, fluorides, etc.), inorganic acid salts (nitrates, sulfates, hydrochlorides, phosphates, phosphites, etc.), and organic acid salts (carboxylates such as formates and acetates, and oxycarboxylates such as lactates and malates). Examples of metal compounds include alumina, zirconia, titanium oxide, barium titanate, alumina nitride, silicon nitride, boron nitride, silicate glass, lead glass, inorganic glass, ruthenium oxide, yttrium oxide, cerium oxide, aluminum silicate, zinc oxide, and copper silicate. Carbon-containing compounds also include carbon black and carbon nanotubes. Further, examples of inorganic particles include copper oxide (CuO), iron oxide (Fe2O3), cobalt oxide (Co2O3), zinc oxide (ZnO), cerium oxide (CeO2), lithium oxide (Li2O), sodium oxide (Na2O), potassium oxide (K2O), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), yttrium oxide (Y2O3), manganese oxide (Mn2O3), indium oxide (In2O3), tin oxide (SnO2), alumina (Al2O3), lanthanum oxide (La2O3), praseodymium oxide (Pr2O3), neodymium oxide (Nd2O3), and samarium oxide. Examples of inorganic particles include SmO, europium oxide (EuO), gadolinium oxide (GdO), terbium oxide (TbO), and dysprosium oxide (DyO), silicon carbide (SiC), lime, calcium phosphate, hydroxyapatite (also called calcium hydroxide phosphate), tricalcium silicate (3CaO·SiO) (also called alite), dicalcium silicate (2CaO·SiO) (also called belite), calcium aluminate (3CaO·AlO) (also called aluminate), calcium aluminoferrite (4CaO·AlO·FeO) (also called ferrite), and calcium sulfate. The inorganic particles may be used alone or in combination of two or more.

[0079] The size of the inorganic particles is not particularly limited, and the inorganic particles preferably include particles having a particle size of 1 nm to 1000 μm. The median diameter of the inorganic particles is preferably 0.01 μm to 100 μm, more preferably 0.05 μm to 50 μm, and even more preferably 0.1 μm to 20 μm. The BET specific surface area of ​​the inorganic particles is 10 m 2 / g or more 2000m 2 / g or less, and 2 / g or more 1000m 2 / g or less is more preferable, and 50m 2 / g or more 1000m 2 / g or less is even more preferable. By having the median diameter and BET specific surface area in the above ranges, sedimentation of inorganic particles in the nanocellulose-containing composition tends to be further suppressed. The median diameter can be measured using a laser diffraction particle size distribution analyzer. Furthermore, the BET specific surface area can be measured using a specific surface area pore size distribution analyzer.

[0080] The content of the compound in the production method of the present invention is not particularly limited and may be any amount.

[0081] The total amount of oxidized cellulose and nanocellulose contained in the nanocellulose-containing composition is not particularly limited, but may be, for example, 0.1 to 90 mass%, 0.1 to 80 mass%, 0.1 to 70 mass%, 0.1 to 60 mass%, 0.1 to 50 mass%, 0.1 to 40 mass%, 0.1 to 30 mass%, or 0.1 to 50 mass%, based on the total mass of the components constituting the nanocellulose-containing composition (excluding the solvent and dispersion medium, if any). 0% by mass, 0.1-20% by mass, 0.1-10% by mass, 0.1-5% by mass, 0.1-1% by mass, 0.5-90% by mass, 1-90% by mass, 5-90% by mass, 10-90% by mass, 20-90% by mass, 3 It may be 0-90% by mass, 40-90% by mass, 50-90% by mass, 60-90% by mass, 70-90% by mass, 80-90% by mass, 40-60% by mass, 30-70% by mass, 20-80% by mass, etc.

[0082] <Nanocellulose> Nanocellulose in the present invention refers to oxidized cellulose obtained by oxidizing a cellulosic raw material with hypochlorous acid or a salt thereof, and refers to the oxidized cellulose that has been defibrated and refined. Nanocellulose includes fine cellulose fibers.

[0083] The average fiber length of the nanocellulose in the present invention is not particularly limited, but is preferably 50 nm or more and 800 nm or less. An average fiber length of 50 nm or more tends to make the quality of the nanocellulose more uniform. From the viewpoint of making the quality more uniform, the lower limit of the average fiber length is more preferably 100 nm or more, and even more preferably 150 nm or more. An average fiber length of 800 nm or less tends to reduce the proportion of coarse cellulose fibers and suppress the occurrence of nanocellulose precipitation. From the viewpoint of further suppressing the occurrence of precipitation, the upper limit of the average fiber length is more preferably 700 nm or less, even more preferably 600 nm or less, even more preferably 500 nm or less, even more preferably 400 nm or less, and even more preferably 300 nm or less. From the viewpoint of further improving the quality of nanocellulose, the average fiber length is more preferably 50 nm to 700 nm, even more preferably 100 nm to 700 nm, even more preferably 100 nm to 600 nm, still more preferably 100 nm to 500 nm, even more preferably 100 nm to 400 nm, and even more preferably 100 nm to 300 nm.

[0084] The average fiber width of the nanocellulose in the present invention is preferably 1 nm or more and 100 nm or less. When the average fiber width is 1 nm or more, the quality of the nanocellulose tends to be more uniform. From the viewpoint of more uniform quality, the lower limit of the average fiber width is more preferably 2 nm or more, and even more preferably 3 nm or more. When the average fiber width is 100 nm or less, the proportion of coarse nanocellulose tends to be reduced and the occurrence of nanocellulose precipitation tends to be suppressed. From the viewpoint of further suppressing the occurrence of precipitation, the average fiber width is more preferably 50 nm or less, even more preferably 30 nm or less, even more preferably 20 nm or less, and even more preferably 10 nm or less. From the viewpoint of further improving the quality of nanocellulose, the average fiber width is more preferably 2 nm or more and 50 nm or less, even more preferably 3 nm or more and 30 nm or less, even more preferably 3 nm or more and 20 nm or less, and even more preferably 3 nm or more and 10 nm or less.

[0085] In the nanocellulose of the present invention, the aspect ratio (average fiber length / average fiber width), which is the ratio of the average fiber width to the average fiber length, is preferably 20 or more and 200 or less. An aspect ratio of 200 or less tends to result in uniform dispersion of nanocellulose and improved quality. From this perspective, the aspect ratio is more preferably 190 or less, and even more preferably 180 or less. On the other hand, an aspect ratio of 20 or more tends to improve the quality of the nanocellulose, as it prevents the nanocellulose from becoming thick and rod-like, which can lead to aggregation due to uneven distribution. Therefore, the aspect ratio is more preferably 30 or more, and even more preferably 40 or more.

[0086] The average fiber width and average fiber length were calculated by mixing nanocellulose with water to a nanocellulose concentration of approximately 1 to 10 ppm, air-drying the resulting diluted cellulose aqueous dispersion on a mica substrate, observing the shape of the nanocellulose using a scanning probe microscope, randomly selecting any number of fibers from the obtained image, and calculating the cross-sectional height of the shape image = fiber width and the perimeter divided by 2 = fiber length. Image processing software can be used to calculate these average fiber widths and lengths. While the image processing conditions are arbitrary, differences in calculated values ​​may occur even for the same image depending on the conditions. The range of difference in values ​​between conditions is preferably within ±100 nm for average fiber length. The range of difference in values ​​between conditions is preferably within ±10 nm for average fiber width. More detailed measurement methods follow the methods described in the Examples below.

[0087] When measuring various physical properties of nanocellulose in the present invention, the nanocellulose-containing composition may be used as the measurement sample, or the nanocellulose obtained after separating the nanocellulose from the nanocellulose-containing composition and other components (compounds) may be used as the measurement sample. In addition, in Production Method II, the measurement sample may be the oxidized cellulose at the end of stirring (before adding at least one compound).

[0088] The average fiber width, average fiber length, and aspect ratio can be suitably controlled by carrying out oxidation using hypochlorous acid or a salt thereof.

[0089] In one aspect, the nanocellulose of the present invention can be characterized by the average fiber width, average fiber length, or aspect ratio, as described above, but in other aspects, it may have a predetermined zeta potential or light transmittance.

[0090] (zeta potential) In one embodiment of the present disclosure, the nanocellulose of the present invention preferably has a zeta potential of -30 mV or less. When the zeta potential is -30 mV or less (i.e., an absolute value of 30 mV or more), sufficient repulsion between microfibrils is obtained, making it easier to produce nanocellulose with a high surface charge density. This improves the dispersion stability of the nanocellulose, and when made into a slurry, it can achieve excellent viscosity stability and handleability. From the perspective of dispersion stability, there is no particular lower limit for the zeta potential. However, when the zeta potential is -100 mV or more (i.e., an absolute value of 100 mV or less), oxidative scission in the fiber direction as oxidation progresses tends to be suppressed, and nanocellulose of uniform size tends to be obtained. The zeta potential tends to be increased by, for example, setting one or more of the reaction time, reaction temperature, and stirring conditions of the oxidation to the side where oxidation is further advanced (i.e., the side where oxidation degree is increased) (for example, by lengthening the reaction time). In addition, the zeta potential can be suitably controlled by performing oxidation using hypochlorous acid or its salt.

[0091] From the above viewpoint, the zeta potential of the nanocellulose in the present invention is more preferably -35 mV or less, even more preferably -40 mV or less, and even more preferably -50 mV or less. The lower limit of the zeta potential is preferably -90 mV or more, more preferably -85 mV or more, even more preferably -80 mV or more, and even more preferably -77 mV or more. The range of the zeta potential can be appropriately combined with the above-mentioned lower and upper limits. The zeta potential is preferably -90 mV or more and -35 mV or less, more preferably -85 mV or more and -40 mV or less, and even more preferably -80 mV or more and -50 mV or less. Note that the zeta potential in this specification is a value measured at pH 8.0 and 20°C for a cellulose aqueous dispersion obtained by mixing the nanocellulose of the present invention with water to a nanocellulose concentration of 0.1% by mass.

[0092] Specifically, the zeta potential can be measured according to the following method. Pure water is added to the nanocellulose to dilute it to a nanocellulose concentration of approximately 0.1%. After dilution, a 0.05 mol / L aqueous solution of sodium hydroxide is added to the nanocellulose aqueous dispersion to adjust the pH to approximately 8.0, and the zeta potential is measured at 20°C using, for example, a zeta potential meter (ELSZ-1000) manufactured by Otsuka Electronics Co., Ltd.

[0093] (light transmittance) The nanocellulose dispersion of the present invention, in which nanocellulose is dispersed in a dispersion medium, exhibits little light scattering by cellulose fibers and exhibits high light transmittance. Specifically, in a preferred embodiment, the nanocellulose of the present invention has a light transmittance of 95% or more in a mixed solution obtained by mixing with water to a solids concentration of 0.1% by mass. The light transmittance is more preferably 96% or more, even more preferably 97% or more, and even more preferably 99% or more. The light transmittance is a value measured at a wavelength of 660 nm using a spectrophotometer.

[0094] The light transmittance can be measured, for example, by placing an aqueous dispersion of nanocellulose in a 10 mm thick quartz cell and using a spectrophotometer (JASCO V-550).

[0095] The nanocellulose of the present invention is an aggregate of individual fibers. When a carboxyl group is introduced into the nanocellulose of the present invention, it is sufficient that it contains at least one carboxylated nanocellulose (also referred to as carboxylated CNF), and it is preferable that the carboxylated nanocellulose is the main component. Here, "carboxylated CNF is the main component" means that the proportion of carboxylated CNF in the total amount of fine cellulose 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.

[0096] The presence of nanocellulose in the nanocellulose-containing composition of the present invention can be determined by the physical properties of the nanocellulose-containing composition as an indicator. That is, the composition has the function provided by nanocellulose, for example, by the nanocellulose-containing composition becoming a slurry or viscous state. Specifically, when compared with a composition that does not contain nanocellulose, the composition obtained by the manufacturing method of the present invention can be determined to contain nanocellulose because it is in a slurry state, thickens, and the blend does not precipitate. Furthermore, when compared with a composition containing nanocellulose produced in accordance with, for example, WO 2018 / 230354, the composition obtained by the production method of the present invention has a slurry-like consistency and viscosity equivalent to those of the above composition. Therefore, it can be determined that the composition contains nanocellulose.

[0097] Whether the nanocellulose-containing composition obtained by the manufacturing method of the present invention contains nanocellulose can also be determined by observing it with a transmission phase contrast optical microscope and determining whether the oxidized cellulose used remains coarse (whether the original oxidized cellulose is maintained).

[0098] The nanocellulose-containing composition obtained by the production method of the present invention can be applied to a variety of uses. Specifically, it may be used, for example, as various materials (e.g., resins, fibers, rubber, etc.) or in various applications (e.g., food, cosmetics, medical products, paints, inks, etc.). The nanocellulose-containing composition can also be formed into a membrane and used as various sheets or films. The fields in which the nanocellulose-containing composition can be applied are not particularly limited, and it can be used in the production of products in various fields such as automotive parts, machine parts, electrical appliances, electronic devices, cosmetics, medical products, building materials, daily necessities, stationery, etc. [Example]

[0099] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0100] [Method for measuring fiber length and fiber width] The compositions obtained in Examples 1 to 12 and Comparative Examples 1 and 2 were diluted 1,000 to 1,000,000 times with pure water, and then naturally dried on a mica substrate. The shapes of the CNFs were observed in AC mode using an Oxford Asylum scanning probe microscope "MFP-3D infinity." The obtained images were binarized using the image processing software "ImageJ" and analyzed for fiber length. For 100 or more fibers, the average fiber length was calculated as fiber length = "perimeter" ÷ 2. Regarding the fiber width, the software attached to the "MFP-3D infinity" was used to calculate the average fiber width for 50 or more fibers, taking the cross-sectional height of the shape image as the fiber width.

[0101] [Measurement of Viscosity Average Degree of Polymerization] Oxidized cellulose was added to an aqueous solution of sodium borohydride adjusted to pH 10, and reduction treatment was carried out at 25°C for 5 hours. The amount of sodium borohydride was 0.1 g per 1 g of oxidized cellulose. After reduction treatment, solid-liquid separation was carried out by suction filtration, followed by washing with water, and the resulting oxidized cellulose was freeze-dried. 0.04 g of dried oxidized cellulose was added to 10 ml of pure water and stirred for 2 minutes, after which 10 ml of 1 mol / L copper ethylenediamine solution was added to dissolve it. The flow time of the blank solution and the flow time of the cellulose solution were then measured at 25°C using a capillary viscometer. The relative viscosity (η) was calculated from the flow time of the blank solution (t0), the flow time of the cellulose solution (t), and the concentration of oxidized cellulose (c [g / ml]) using the following equation: r ), specific viscosity (η sp ) and intrinsic viscosity ([η]) were measured sequentially, and the degree of polymerization (DP) of the oxidized cellulose was calculated using the viscosity measurement equation. η r =η / η0=t / t0 η sp =η r -1 [η]=η sp / (100×c(1+0.28η sp )) DP=175×[η]

[0102] (Measurement of Carboxy Group Amount) To 60 ml of an oxidized cellulose aqueous dispersion, in which the oxidized cellulose concentration had been adjusted to 0.5% by mass, 0.1 mol / L 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 carboxyl groups (mmol / g) was calculated using the following formula from the amount of sodium hydroxide (a) consumed in the neutralization stage of the weak acid, in which the change in electrical conductivity was gradual. Amount of carboxyl group = a (ml) x 0.05 / mass of oxidized cellulose (g)

[0103] [Production Example 1] Preparation of oxidized cellulose 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 adjust the effective chlorine concentration to 21% by mass. 35% by mass of hydrochloric acid was added thereto and stirred to obtain a sodium hypochlorite aqueous solution with a pH of 11. The above sodium hypochlorite aqueous solution was heated to 30°C in a constant temperature water bath while being stirred at 200 rpm using a propeller-type stirring blade in a Shinto Scientific mixer (Three-One Motor, BL600), and then 50 g of powdered pulp (VP-1) from TDI was added as a cellulosic raw material. After supplying the cellulosic raw material, the mixture was kept at 30°C in the same thermostatic water bath, and the pH during the reaction was adjusted to 11 by adding 48% by mass of sodium hydroxide, followed by stirring under the same conditions for 2 hours using a stirrer. After the reaction was completed, oxidized cellulose was recovered by repeating centrifugation (1000 G, 10 minutes), decantation, and adding pure water in an amount equivalent to the removed liquid. Furthermore, the nitrogen content derived from N-oxyl compounds in the oxidized cellulose was measured using a trace total nitrogen analyzer (manufactured by Mitsubishi Chemical Analytech Co., Ltd., device name: TN-2100H), and the increase from the raw pulp was calculated to be 1.0 mass ppm or less. The resulting oxidized cellulose was used to prepare an oxidized cellulose aqueous dispersion with an oxidized cellulose concentration of 0.1%. This oxidized cellulose aqueous dispersion was stirred, and the resulting nanocellulose aqueous dispersion was placed in a 10 mm thick quartz cell and measured for light transmittance at a wavelength of 660 nm using a spectrophotometer (JASCO V-550). A Thinky Planetary Mixer "Awatori Rentaro ARE-310" was used as the stirrer, and the mixture was stirred for 10 minutes in mix mode at a revolution speed of 2000 rpm and a rotation speed of 800 rpm. The evaluation criteria were as follows: A: Light transmittance is 80% or more B: Light transmittance is 70% or more but less than 80% C: Light transmittance is 60% or more but less than 70% D: Light transmittance less than 60%

[0104] The available chlorine concentration in the aqueous sodium hypochlorite solution was measured by the following method. (Measurement of available chlorine concentration in sodium hypochlorite solution) 0.582 g of an aqueous solution of sodium hypochlorite pentahydrate crystals in purified water was precisely weighed, 50 mL of purified water was added, 2 g of potassium iodide, and 10 mL of acetic acid were added, and the solution was immediately sealed and left in the dark for 15 minutes. After leaving the solution for 15 minutes, the liberated iodine was titrated with 0.1 mol / L sodium thiosulfate solution (solution factor 1.000) (indicator: starch TS). The titer was 34.55 mL. A blank test was performed separately, and correction was made. Since 1 mL of 0.1 mol / L sodium thiosulfate solution corresponds to 3.545 mg Cl, the available chlorine concentration in the sodium hypochlorite aqueous solution was 21% by mass.

[0105] [Manufacturing Example 2] Oxidized cellulose was obtained in the same manner as in Production Example 1, except that the reaction time was changed to 4 hours.

[0106] [Manufacturing Example 3] Oxidized cellulose was obtained in the same manner as in Production Example 1, except that the reaction time was changed to 1.5 hours.

[0107] [Manufacturing Example 4] Oxidized cellulose was obtained in the same manner as in Production Example 1, except that KC Flock W-100GK manufactured by Nippon Paper Industries Co., Ltd. was used as the raw material and the reaction time was 4 hours.

[0108] [Manufacturing Example 5] Oxidized cellulose was obtained in the same manner as in Production Example 4, except that the reaction time was changed to 3 hours.

[0109] [Manufacturing Example 6] Oxidized cellulose was obtained in the same manner as in Production Example 4, except that the reaction time was changed to 1 hour.

[0110] The oxidized cellulose obtained in Production Examples 1 to 6 was freeze-dried, and the solid of the sample was left at 23°C and 50% RH for 24 hours or more. 13As a result of measuring C-NMR, it was confirmed that both compounds have a structure in which the hydroxyl groups at the second and third positions of the glucopyranose ring have been oxidized and carboxyl groups have been introduced. 13 The measurement conditions for C-NMR are as follows: (1) Sample tube: Zirconia tube (4 mm diameter) (2) Magnetic field strength: 9.4T (1H resonance frequency: 400MHz) (3) MAS rotation speed: 15 kHz (4) Pulse sequence: CPMAS method (5) Contact time: 3 ms (6) Waiting time: 5 seconds (7) Accumulation count: 10,000 to 15,000 times (8) Measuring device: JNM ECA-400 (manufactured by JEOL Ltd.)

[0111] Furthermore, the fact that the oxidized cellulose obtained in Production Examples 1 to 6 has a structure in which the hydroxyl groups at the second and third positions of the glucopyranose ring have been oxidized and carboxyl groups have been introduced was also confirmed by the results of measuring model molecules of the oxidized cellulose as samples. In addition, regarding the sixth place, solid cellulosic raw materials 13 C-NMR and solid state oxidized cellulose 13 Since no change was observed in the spectral data with C-NMR, it was determined that the hydroxyl group at position 6 was not oxidized and remained as a hydroxyl group in the oxidized cellulose.

[0112] The degree of polymerization, acid value (amount of carboxy groups), and light transmittance of the oxidized cellulose obtained in Production Examples 1 to 6 are shown in Table 1.

[0113] [Table 1]

[0114] [Example 1] Production of nanocellulose-containing composition A mixture was obtained by adding purified water to a mixture of zinc oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., average particle size 20 nm) and the oxidized cellulose of Production Example 1 to adjust the concentration to 10% by mass of zinc oxide and 5% by mass of oxidized cellulose. The resulting mixture was dispersed by stirring in a homomixer at 10,000 rpm for 10 minutes. The dispersed mixture was analyzed using the [Method for Measuring Fiber Length and Fiber Width] and CNFs with an average fiber length of 196 nm and an average fiber width of 3.7 nm were confirmed. In other words, it was confirmed that a nanocellulose-containing composition had been obtained. In this analysis, some particles (average height 10 nm to 30 nm) rather than fibers were observed, but these were presumed to be zinc oxide nanoparticles or their crushed particles or aggregates based on their shape, and were therefore excluded from the CNF shape measurement. Furthermore, the dispersed mixture thickened, and no precipitation of zinc oxide was observed even after leaving it to stand for two days at 23°C. The fact that the mixture thickened and no precipitation was observed was due to the expression of the nanocellulose function, and it was confirmed that a nanocellulose-containing composition had been obtained.

[0115] [Examples 2 to 6] A nanocellulose-containing composition was obtained in the same manner as in Example 1, except that the oxidized celluloses of Production Examples 2 to 6 were used.

[0116] The evaluation results of the nanocellulose-containing compositions of Examples 1 to 6 are shown in Table 2. In the table, "Thickening" indicates that, for the mixture, A indicates that thickening was observed, B indicates that thickening was observed but some separation was observed, and C indicates that no thickening occurred. In the table, "Precipitation" indicates that, with respect to zinc oxide, A means no precipitation, B means that most of the zinc oxide did not precipitate but a small amount of precipitate was observed, and C means that zinc oxide precipitated.

[0117] [Table 2]

[0118] [Example 7] Production of nanocellulose-containing composition The oxidized cellulose from Production Example 1 was defibrated using a homomixer at 10,000 rpm for 10 minutes to obtain an aqueous dispersion of nanocellulose (concentration: 1.0% by mass). Analysis of the aqueous dispersion revealed nanocellulose with an average fiber length of 165 nm and an average fiber width of 4.2 nm. The resulting CNF aqueous dispersion was then appropriately concentrated using an evaporator, and purified water was added to obtain a mixture containing 10% by mass of zinc oxide (average particle size 20 nm) and 5% by mass of nanocellulose. The mixture thickened, but no precipitation was observed.

[0119] [Examples 8 to 12] A nanocellulose-containing composition was obtained in the same manner as in Example 7, except that the oxidized celluloses of Production Examples 2 to 6 were used.

[0120] The evaluation results of the nanocellulose-containing compositions of Examples 7 to 12 are shown in Table 3. The evaluation criteria for "thickening" and "precipitation" in the table are the same as those in Table 2.

[0121] [Table 3]

[0122] [Comparative Example 1] A mixture was obtained in the same manner as in Example 1, except that the dispersion treatment by stirring with a homomixer was not performed. When this mixture was left to stand at 23°C for 2 days, no increase in viscosity was observed, and precipitation of zinc oxide was observed. Since no increase in viscosity was observed and precipitation was observed, it became clear that the pulverization had not progressed. In other words, a nanocellulose-containing composition could not be obtained. When observed using a transmission phase contrast optical microscope (Nikon Corporation, product number LV100ND), the oxidized cellulose did not become finer and remained coarse. Furthermore, because the mixture could not be analyzed using the [method for measuring fiber length and fiber width], nanocellulose could not be observed and the average fiber length and average fiber width could not be calculated.

[0123] Comparative Example 2 (Preparation of oxidized cellulose) Oxidized cellulose was prepared by TEMPO oxidation. 0.8 g of TEMPO, 5.0 g of sodium bromide, and purified water were added to a beaker and stirred to prepare an aqueous solution. The above aqueous solution was heated to 25°C in a constant temperature water bath while being stirred at 200 rpm using a propeller-type stirring blade in a Shinto Scientific mixer (Three-One Motor, BL600), and then 50 g of powdered pulp (VP-1) from TDI was added as a cellulosic raw material. 0.1 M sodium hydroxide was added and stirred to obtain an aqueous solution with a pH of 10.0. 129 g of an aqueous sodium hypochlorite solution with an available chlorine concentration of 13.2% by mass was added, and while maintaining the temperature at 25°C in the same thermostatic water bath, the pH during the reaction was adjusted to 10.0 by adding 0.1 M sodium hydroxide, and the mixture was stirred for 2 hours. After the reaction was completed, oxidized cellulose was recovered by repeated centrifugation (1000 G, 10 minutes) and decantation. (Preparation of CNF blended composition) Oxidized cellulose obtained by TEMPO oxidation was mixed with pure water to prepare a solution containing 10% by mass of zinc oxide (average particle size 20 nm) and 5% by mass of TEMPO-oxidized cellulose, and the mixture was stirred at 10,000 rpm in a homomixer for 10 minutes. When observed using a transmission phase contrast optical microscope (Nikon Corporation, product number LV100ND), the oxidized cellulose did not become finer and remained coarse. Furthermore, the mixture was analyzed using the [Method for measuring fiber length and fiber width], and therefore nanocellulose could not be observed, and the average fiber length and average fiber width could not be calculated. [Industrial Applicability]

[0124] The present invention has industrial applicability in fields where nanocellulose is used, specifically in fields such as resins, fibers, rubber, foods, cosmetics, medical products, paints, inks, sheets, and films.

Claims

1. A method for producing a composition containing nanocellulose, comprising: The method includes a step of defibrating the oxidized cellulose into the nanocellulose by stirring a mixture containing oxidized cellulose and an optional dispersion medium, and components other than the nanocellulose and the dispersion medium that constitute the composition, The oxidized cellulose contains an oxidation product of a cellulosic raw material with hypochlorous acid or a salt thereof, and has a structure in which the hydroxyl groups at the second and third positions of the glucopyranose ring are oxidized to introduce carboxyl groups. Manufacturing method.

2. A method for producing a composition containing nanocellulose, comprising: The method includes a step of defibrating oxidized cellulose dispersed in a dispersion medium into nanocellulose by stirring the oxidized cellulose, and subsequently adding components other than the nanocellulose and the dispersion medium that constitute the composition, the oxidized cellulose comprises an oxidation product of a cellulose-based raw material with hypochlorous acid or a salt thereof, and has a structure in which hydroxyl groups at the second and third positions of a glucopyranose ring are oxidized to introduce carboxyl groups; The stirring of the oxidized cellulose and the addition of the ingredients are carried out in one pot; Manufacturing method.

3. The degree of polymerization of the oxidized cellulose is 600 or less. The method according to claim 1 or 2.

4. The nanocellulose aqueous dispersion obtained by defibrating an aqueous dispersion of oxidized cellulose having a concentration of 0.1% by mass using a planetary centrifugal mixer at a revolution speed of 2000 rpm and a rotation speed of 800 rpm for 10 minutes has a light transmittance of 60% or more. The method according to any one of claims 1 to 3.

5. The stirring is performed by a submerged disperser. The method according to any one of claims 1 to 4.

6. The component comprises inorganic particles. The method according to any one of claims 1 to 5.

7. The component includes a resin or a rubber, or a raw material monomer thereof. The method according to any one of claims 1 to 6.

8. The total amount of the oxidized cellulose and the nanocellulose contained in the composition is 0.1 to 90% by mass based on the total mass of the components constituting the composition (excluding the solvent and dispersion medium), The method according to any one of claims 1 to 7.

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