Method for producing a modified cellulose nanofiber composition

Abstract

To provide a method for producing a modified cellulose nanofiber composition that allows cellulose nanofiber to be well dispersed, and is capable of easily widening a range of application of cellulose.SOLUTION: A method for producing a modified cellulose nanofiber composition includes: a process for producing modified cellulose nanofiber, including a cellulose nanofiber dispersion liquid preparation step for preparing cellulose nanofiber dispersion liquid having cellulose nanofiber dispersed in water, a silane coupling agent-containing dispersion liquid preparation step for adding, to the cellulose nanofiber dispersion liquid, an epoxy group-bearing silane coupling agent at a rate of 0.005 mol or more and 6.0 mol or less per 1.0 mol of a β-glucose unit of the cellulose nanofiber, to obtain silane coupling agent-containing dispersion liquid, and a drying step for drying the silane coupling agent-containing dispersion liquid to modify the cellulose nanofiber with the silane coupling agent; a dispersion medium preparation process for preparing a dispersion medium; a cellulose derivative addition process for adding a cellulose derivative to the prepared dispersion medium to prepare a cellulose derivative-containing solution; and a modified cellulose nanofiber addition process for adding, to the cellulose derivative-containing solution, the modified cellulose nanofiber so that the cellulose derivative is 10 pts.mass or more and 2000 pts.mass or less relative to the modified cellulose nanofiber 100 pts.mass.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a modified nanocellulose composition modified with a silane coupling agent, and more particularly to a method for producing a modified cellulose nanofiber composition that also exhibits affinity for hydrophobic substances. [Background technology]

[0002] Nanocellulose is a cellulose fiber with a thickness on the order of nanometers, obtained by defibrating plant fibers such as pulp in an aqueous medium. Nanocellulose is classified into cellulose nanofibers, cellulose crystals, cellulose whiskers, and bacterial cellulose depending on the structure of the cellulose. Cellulose nanofibers are attracting attention for their use as a reinforcing material for thermoplastic resins, for example, due to their lightweight and high strength (see, for example, Patent Document 1).

[0003] On the other hand, because cellulose nanofibers are hydrophilic, uniform dispersion in organic solvents and uniform mixing with hydrophobic materials such as resins are difficult, which limits their range of application. Therefore, for example, it has been proposed to improve the dispersibility in organic solvents by imparting hydrophobicity to cellulose nanofibers by reacting them with vinyl organic acid in a hydrated state and then recovering the product (see, for example, Patent Document 2). Hereinafter, cellulose nanofibers that have been given desired properties such as hydrophobicity from naturally derived cellulose nanofibers obtained from plant fibers, etc., are sometimes referred to as "modified cellulose nanofibers."

[0004] However, the modified cellulose nanofibers described in Patent Document 2 have strict reaction conditions between cellulose nanofibers and vinyl organic acids, and the production process is complicated, necessitating improvements in manufacturing efficiency. Furthermore, in modified cellulose nanofibers modified with vinyl organic acids, the molecular structure of the cellulose nanofiber skeleton itself changes depending on the degree of modification, potentially altering the properties of the cellulose nanofibers. In addition, there was room for improvement in terms of improving the hydrophobicity of the modified cellulose nanofibers, and consequently, improving their dispersibility in dispersion media such as organic solvents. Therefore, the modified cellulose nanofibers described in Patent Document 2 still need improvement in obtaining dispersions with excellent dispersibility of cellulose nanofibers, and the application range of cellulose nanofibers remains limited.

[0005] Furthermore, as a technique for imparting hydrophobicity to cellulose nanofibers, it has been proposed to bond two types of modifying groups to the surface of cellulose nanofibers: a modifying group selected for its wettability, such as aromatic groups, and a modifying group selected for its steric repulsion and hydrophobicity, such as polyalkylene glycol groups. This method allows for the acquisition of hydrophobic cellulose nanofibers with a small mass of modifying groups. However, modified cellulose nanofibers produced using two types of modifying groups, such as aromatic groups and polyalkylene glycol groups, have a complex chemical structure, and there is still a need for improvement in obtaining dispersions with excellent dispersibility of cellulose nanofibers. In addition, modified cellulose nanofibers using two types of modifying groups, such as aromatic groups and polyalkylene glycol groups, do not possess highly reactive functional groups, which makes it difficult to expand their application fields. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-11392 [Patent Document 2] International Publication No. 2016 / 010016 [Overview of the Initiative] [Problems to be Solved by the Invention]

[0007] In view of the above circumstances, an object of the present invention is to provide a method for producing a modified cellulose nanofiber composition that has excellent dispersibility of cellulose nanofibers, can easily expand the application range of cellulose, and has excellent hydrophobicity imparted to the cellulose nanofibers and excellent affinity with hydrophobic substances. [Means for Solving the Problems]

[0008] The gist of the configuration of the present invention is as follows. [1] A cellulose nanofiber dispersion liquid preparation step of preparing a cellulose nanofiber dispersion liquid in which cellulose nanofibers are dispersed in water, and Adding a silane coupling agent having an epoxy group to the cellulose nanofiber dispersion liquid in an amount of 0.005 mol or more and 6.0 mol or less per 1.0 mol of β-glucose units of the cellulose nanofibers to obtain a dispersion liquid containing a silane coupling agent, a silane coupling agent-containing dispersion liquid preparation step, and A drying step of subjecting the dispersion liquid containing a silane coupling agent to a drying treatment to modify the cellulose nanofibers with the silane coupling agent, and A step of producing modified cellulose nanofibers in a step having, and A dispersion medium preparation step of preparing a dispersion medium, and A cellulose derivative addition step of adding a cellulose derivative to the prepared dispersion medium to prepare a cellulose derivative-containing solution, and A modified cellulose nanofiber addition step of adding the modified cellulose nanofibers to the cellulose derivative-containing solution in a range of 100 parts by mass of the modified cellulose nanofibers: 10 parts by mass or more and 2000 parts by mass or less of the cellulose derivative, and A method for producing a modified cellulose nanofiber composition including. [2] A cellulose nanofiber dispersion liquid preparation step of preparing a cellulose nanofiber dispersion liquid in which cellulose nanofibers are dispersed in water, A step of preparing a dispersion liquid containing a silane coupling agent, in which a silane coupling agent having an epoxy group is added to the cellulose nanofiber dispersion liquid in an amount of 0.005 mol or more and 6.0 mol or less per 1.0 mol of β-glucose units of the cellulose nanofibers to obtain a dispersion liquid containing a silane coupling agent. A drying step of subjecting the dispersion liquid containing the silane coupling agent to a drying treatment to modify the cellulose nanofibers with the silane coupling agent. A step of manufacturing modified cellulose nanofibers in a step having the above steps. A step of preparing a dispersion medium. A step of adding the modified cellulose nanofibers to the prepared dispersion medium to prepare a dispersion medium containing modified cellulose nanofibers. A step of adding a cellulose derivative to the dispersion medium containing modified cellulose nanofibers in a range of 100 parts by mass of the modified cellulose nanofibers: 10 parts by mass or more and 2000 parts by mass or less of the cellulose derivative. A method for manufacturing a modified cellulose nanofiber composition, including the above steps. [3] A step of preparing a cellulose nanofiber dispersion liquid in which cellulose nanofibers are dispersed in water. A step of preparing a dispersion liquid containing a silane coupling agent, in which a silane coupling agent having an epoxy group is added to the cellulose nanofiber dispersion liquid in an amount of 0.005 mol or more and 6.0 mol or less per 1.0 mol of β-glucose units of the cellulose nanofibers to obtain a dispersion liquid containing a silane coupling agent. A drying step of subjecting the dispersion liquid containing the silane coupling agent to a drying treatment to modify the cellulose nanofibers with the silane coupling agent. A step of manufacturing modified cellulose nanofibers in a step having the above steps. A step of preparing a dispersion medium. A cellulose component addition step is to add a cellulose derivative and the modified cellulose nanofiber as cellulose components to the prepared dispersion medium in a range of 100 parts by mass of the modified cellulose nanofiber and 10 to 2000 parts by mass of the cellulose derivative, A method for producing a modified cellulose nanofiber composition containing [the specified substance]. [4] A cellulose nanofiber dispersion is prepared by dispersing cellulose nanofibers in water, a step of preparing a cellulose nanofiber dispersion, A silane coupling agent-containing dispersion preparation step is performed by adding a silane coupling agent having an epoxy group to the cellulose nanofiber dispersion in an amount of 5.0 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber to obtain a silane coupling agent-containing dispersion. A drying step in which the silane coupling agent-containing dispersion is subjected to a drying treatment to modify the cellulose nanofiber with the silane coupling agent, A process for producing modified cellulose nanofibers in a process having the following: The dispersion medium preparation process involves preparing the dispersion medium, A modified cellulose nanofiber addition step is performed to prepare a modified cellulose nanofiber-containing dispersion medium by adding the modified cellulose nanofiber to the prepared dispersion medium, A method for producing a modified cellulose nanofiber composition containing [the specified substance]. [5] A method for producing a modified cellulose nanofiber composition according to any one of [1] to [4], wherein the drying treatment is a drying treatment using freeze-drying. [6] A method for producing a modified cellulose nanofiber composition according to any one of [1] to [5], further comprising a dialysis step of dialyzing the silane coupling agent-containing dispersion using a dialysis membrane between the silane coupling agent-containing dispersion preparation step and the drying step. [7] A method for producing a modified cellulose nanofiber composition according to any one of [1] to [6], wherein the silane coupling agent has at least an epoxy group and an alkoxy group. [8] A method for producing a modified cellulose nanofiber composition according to any one of [1] to [7], wherein the silane coupling agent has an epoxy group, an alkoxy group, and an alkyl group. [9] The silane coupling agent is the following general formula (1) [ka] (In general formula (1), X represents an organic functional group containing an epoxy group, and R 1 , R 2 , R 3 A method for producing a modified cellulose nanofiber composition according to any one of [1] to [8], wherein each of the following independently represents a chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms.

[10] The R 1 , the R 2 , the R 3 A method for producing a modified cellulose nanofiber composition according to [9], wherein at least one of the members is an alkoxy group having 1 to 5 carbon atoms, and at least one is an alkyl group having 1 to 5 carbon atoms.

[11] A method for producing a modified cellulose nanofiber composition according to any one of [1] to

[10] , wherein the silane coupling agent comprises 3-glycidoxypropyl(dimethoxy)methylsilane.

[12] A method for producing a modified cellulose nanofiber composition according to any one of [1] to [3], wherein the cellulose derivative comprises at least one selected from the group consisting of hydroxyalkylcellulose and alkylcellulose.

[13] A method for producing a modified cellulose nanofiber composition according to any one of [1] to [3], wherein the cellulose derivative is hydroxyalkylcellulose.

[14] A method for producing a modified cellulose nanofiber composition according to

[12] or

[13] , wherein the hydroxyalkyl cellulose is hydroxypropyl cellulose.

[15] A method for producing a modified cellulose nanofiber composition according to any one of [1] to [3], wherein 0.5 parts by mass or more and 120 parts by mass or less of the cellulose derivative are added to 100 parts by mass of the dispersion medium.

[16] A method for producing a modified cellulose nanofiber composition according to any one of [1] to

[15] , which is a dispersion of the modified cellulose nanofibers.

[17] A method for producing the modified cellulose nanofiber composition according to

[16] , wherein the average value of the transmittance of the dispersion of the modified cellulose nanofibers at a wavelength of 400 nm at a rotation speed of 1000 rpm of the stirring means is less than 5.0.

[18] A method for producing a modified cellulose nanofiber composition according to

[16] or

[17] , wherein the standard deviation of the transmittance of the dispersion of the modified cellulose nanofibers at a wavelength of 400 nm at a rotation speed of 1000 rpm of the stirring means is less than 1.0.

[0009] The method for producing the modified cellulose nanofiber composition described in [1] includes a step of producing modified cellulose nanofibers modified with a silane coupling agent by chemically bonding the silanol groups of the silane coupling agent to the hydroxyl groups of the cellulose nanofibers. In other words, the modified cellulose nanofibers have a structure in which the silane coupling agent is chemically bonded to the hydroxyl groups of cellulose. Note that "cellulose nanofibers" refers to cellulose fibers with an average fiber diameter of less than 1.0 μm, that is, cellulose fibers with an average fiber diameter on the nanoscale.

[0010] Furthermore, the cellulose derivative used in the method for producing the modified cellulose nanofiber composition [1] is dissolved in the dispersion medium within the obtained modified cellulose nanofiber composition. It is thought that because the cellulose derivative is dissolved in the dispersion medium within the modified cellulose nanofiber composition, the hydroxyl groups of the cellulose derivative interact with the hydroxyl groups of the modified cellulose nanofibers in the modified cellulose nanofiber composition, resulting in a state where the cellulose derivative is coordinated to the modified cellulose nanofibers.

[0011] "The transmittance of light at a wavelength of 400 nm in a dispersion of cellulose nanofibers at a stirring speed of 1000 rpm" refers to the transmittance of light at a path length of 1 cm and wavelength of 400 nm measured at the center of the cellulose nanofiber dispersion, when 2.0 ml of a dispersion of cellulose nanofibers (prepared by adding a predetermined amount of cellulose derivative to 0.1 g of cellulose nanofibers per 20 ml of dispersion medium) is placed in a 4.5 ml container and stirred at a rotation speed of 1000 rpm using a stirrer (stirring bar) with a diameter of 9 mm and a height of 6.5 mm under conditions of 25°C. The transmittance measurement result for a single measurement is calculated as the average transmittance over 180 seconds, measured every 2 seconds from the start of stirring. "Average transmittance" refers to the average of the average transmittance measurements from three measurements. Furthermore, "standard deviation of transmittance" refers to the average of the standard deviations obtained from three average transmittance measurements, calculated by taking a single average transmittance measurement, that is, a measurement of transmittance taken every two seconds for 180 seconds. [Effects of the Invention]

[0012] The present invention provides a method for producing a modified cellulose nanofiber composition, comprising: a cellulose nanofiber dispersion preparation step, in which cellulose nanofibers are dispersed in water to prepare a cellulose nanofiber dispersion; a silane coupling agent-containing dispersion preparation step, in which a silane coupling agent having an epoxy group is added to the cellulose nanofiber dispersion in an amount of 0.005 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofibers to obtain a silane coupling agent-containing dispersion; a drying step, in which the silane coupling agent-containing dispersion is subjected to a drying treatment to modify the cellulose nanofibers with the silane coupling agent; a dispersion medium preparation step, in which a cellulose derivative is added to the prepared dispersion medium to prepare a cellulose derivative-containing solution; and a modified cellulose nanofiber is added to the cellulose derivative-containing solution in an amount of 100 parts by mass of the modified cellulose nanofiber and 10 to 2000 parts by mass of the cellulose derivative. The method includes a nanofiber addition step, or a dispersion medium preparation step of preparing a dispersion medium, a modified cellulose nanofiber addition step of adding the modified cellulose nanofiber to the prepared dispersion medium to prepare a modified cellulose nanofiber-containing dispersion medium, and a cellulose derivative addition step of adding a cellulose derivative to the modified cellulose nanofiber-containing dispersion medium in the range of 100 parts by mass of the modified cellulose nanofiber: 10 to 2000 parts by mass of the cellulose derivative, or a dispersion medium preparation step of preparing a dispersion medium, and a cellulose component addition step of adding a cellulose derivative and the modified cellulose nanofiber as cellulose components to the prepared dispersion medium in the range of 100 parts by mass of the modified cellulose nanofiber: 10 to 2000 parts by mass of the cellulose derivative, thereby providing excellent dispersibility of the modified cellulose nanofiber, easily expanding the range of applications for cellulose, and imparting excellent hydrophobicity to the cellulose nanofiber, thereby producing a modified cellulose nanofiber composition with excellent affinity to hydrophobic substances.Therefore, the modified cellulose nanofiber composition obtained by the manufacturing method of the present invention allows for uniform dispersion of the modified cellulose nanofibers in the hydrophobic substance to be applied, and reliably imparts the properties of the cellulose nanofibers to the target substance. Furthermore, the manufacturing method of the modified cellulose nanofiber composition of the present invention allows for the production of the modified cellulose nanofiber composition through a simple production process, resulting in excellent production efficiency.

[0013] Furthermore, the present invention provides a method for producing a modified cellulose nanofiber composition that includes the following steps: a cellulose nanofiber dispersion preparation step of preparing a cellulose nanofiber dispersion by dispersing cellulose nanofibers in water; a silane coupling agent-containing dispersion preparation step of adding 5.0 moles to 6.0 moles of a silane coupling agent having epoxy groups to the cellulose nanofiber dispersion at a rate of 1.0 mole to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber to obtain a silane coupling agent-containing dispersion; a drying step of drying the silane coupling agent-containing dispersion to modify the cellulose nanofibers with the silane coupling agent; a dispersion medium preparation step of preparing a dispersion medium; and a modified cellulose nanofiber addition step of adding the modified cellulose nanofibers to the prepared dispersion medium to prepare a modified cellulose nanofiber-containing dispersion medium. This method provides excellent dispersibility for the modified cellulose nanofibers, easily expands the range of applications for cellulose, imparts excellent hydrophobicity to the cellulose nanofibers, and produces a modified cellulose nanofiber composition with excellent affinity to hydrophobic substances. Moreover, the modified cellulose nanofiber composition can be produced using a simple production process.

[0014] Furthermore, the method for producing the modified cellulose nanofiber composition of the present invention makes it possible to obtain a modified cellulose nanofiber composition having epoxy groups with excellent reactivity as functional groups. Therefore, the obtained modified cellulose nanofiber composition can be further modified via epoxy groups. Accordingly, the range of hydrophobic substances to which the modified cellulose nanofiber composition obtained by the production method of the present invention can be easily expanded.

[0015] The method for producing the modified cellulose nanofiber composition of the present invention, by using freeze-drying as the drying process, facilitates the drying process and suppresses the occurrence of ring-opening reactions of the epoxy group of the silane coupling agent.

[0016] The present invention provides a method for producing a modified cellulose nanofiber composition, which further includes a dialysis step between the silane coupling agent-containing dispersion preparation step and the drying step. This step allows for the removal of unreacted silane coupling agent and by-products remaining in the silane coupling agent-containing dispersion by dialysis, thereby improving the purity of the modified cellulose nanofiber.

[0017] According to the method for producing the modified cellulose nanofiber composition of the present invention, the silane coupling agent has at least an epoxy group and an alkoxy group, thereby reliably modifying the cellulose and producing a modified cellulose nanofiber composition that reliably possesses excellent hydrophobicity.

[0018] According to the method for producing a modified cellulose nanofiber composition of the present invention, by using a silane coupling agent having epoxy groups, alkoxy groups, and alkyl groups, it is possible to produce a modified cellulose nanofiber composition that reliably modifies cellulose to reliably impart excellent hydrophobicity while reliably suppressing aggregation of modified cellulose nanofibers. Therefore, it is possible to produce a modified cellulose nanofiber composition that can be dispersed more reliably and uniformly in hydrophobic substances such as organic solvents and resins.

[0019] According to the method for producing a modified cellulose nanofiber composition of the present invention, the silane coupling agent has the following general formula (1) [Chemical formula] (In general formula (1), X represents an organic functional group containing an epoxy group, and R 1 , R 2 , R 3 each independently represents chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms.) By being a compound represented by the above formula, modified cellulose nanofibers with reliably improved hydrophobicity can be produced.

[0020] According to the method for producing a modified cellulose nanofiber composition of the present invention, since the silane coupling agent contains 3-glycidoxypropyl(dimethoxy)methylsilane, a modified cellulose nanofiber composition can be produced that can more reliably suppress the aggregation of modified cellulose nanofibers while surely imparting more excellent hydrophobicity.

[0021] According to the method for producing a modified cellulose nanofiber composition of the present invention, by including at least one selected from the group consisting of hydroxyalkyl cellulose and alkyl cellulose as the cellulose derivative, excellent dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition can be surely obtained.

[0022] According to the method for producing a modified cellulose nanofiber composition of the present invention, when the cellulose derivative is hydroxyalkyl cellulose, the dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition is more surely improved.

[0023] According to the method for producing the modified cellulose nanofiber composition of the present invention, the dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition is further improved by using hydroxypropyl cellulose instead of hydroxyalkyl cellulose. [Modes for carrying out the invention]

[0024] Details of the method for producing the modified cellulose nanofiber composition of the present invention will be described below. First, the method for producing the modified cellulose nanofibers used in the method for producing the modified cellulose nanofiber composition of the present invention will be described.

[0025] In the method for producing modified cellulose nanofibers, modified cellulose nanofibers can be produced in which at least a portion of the hydroxyl groups of the cellulose nanofibers are modified with a silane coupling agent having epoxy groups. In other words, modified cellulose nanofibers are cellulose nanofibers modified with a silane coupling agent.

[0026] <Method for manufacturing modified cellulose nanofibers> The method for producing modified cellulose nanofibers is described in detail below. The method for producing modified cellulose nanofibers comprises: (1) a step of preparing a cellulose nanofiber dispersion by dispersing cellulose nanofibers in water; (2) a step of preparing a silane coupling agent-containing dispersion by adding 0.005 moles to 6.0 moles of a silane coupling agent having epoxy groups to the cellulose nanofiber dispersion at a rate of 0.005 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofibers; and (3) a drying step of subjecting the silane coupling agent-containing dispersion to a drying treatment to modify the cellulose nanofibers with the silane coupling agent.

[0027] (1) Preparation of cellulose nanofiber dispersion The cellulose nanofiber dispersion preparation process is a process of preparing a cellulose nanofiber aqueous dispersion by dispersing cellulose nanofibers (hereinafter sometimes referred to as "raw material cellulose nanofibers") used as raw materials for modified cellulose nanofibers in water. The raw material cellulose nanofibers form the backbone of the modified cellulose nanofibers.

[0028] Raw cellulose nanofibers may not have undergone specific hydrophobic treatments, and are generally hydrophilic. One method for preparing raw cellulose nanofibers is to defibrate a cellulose precursor derived from a natural product to obtain nanofibers. Examples of cellulose precursors used as raw materials for cellulose nanofibers include plant fibers such as pulp. The method for defibrating the cellulose precursor is not particularly limited and can include defibration using a mixer, high-speed homomixer, ultrasonic homogenizer, low-pressure homogenizer, high-pressure homogenizer, high-speed rotary mixer, grinder, freeze-drying, media mill, ball mill, etc.

[0029] The size of the raw cellulose nanofibers is not particularly limited as long as the average fiber diameter is less than 1.0 μm. However, from the viewpoint of homogenizing the cellulose modification sites by the silane coupling agent and expanding the range of application of the modified cellulose nanofibers, the average fiber diameter is preferably 4 nm to 100 nm, and particularly preferably 10 nm to 50 nm. Similarly, the average fiber length of the raw cellulose nanofibers is not particularly limited, but from the viewpoint of homogenizing the cellulose modification sites by the silane coupling agent and expanding the range of application of the modified cellulose nanofibers, it is preferably 20 μm to 200 μm, and particularly preferably 50 μm to 150 μm. The average fiber diameter and average fiber length of the raw cellulose nanofibers can be measured, for example, by scanning probe microscopy or nitrogen adsorption for the average fiber diameter, and by electron microscopy (transmission electron microscope (TEM), scanning electron microscope (SEM)) or scanning probe microscopy for the average fiber length.

[0030] As described above, raw cellulose nanofibers pre-dispersed in water can be prepared as a cellulose nanofiber dispersion. The content of raw cellulose nanofibers in the cellulose nanofiber dispersion is not particularly limited, and its lower limit is determined by appropriately diluting it with water until it can be sufficiently stirred using a stirrer such as a magnetic stirrer. In particular, when determining an appropriate dispersion state by considering the stirrer, stirring container, and amount of raw cellulose nanofibers, it is preferable to use 0.05 parts by mass, and especially preferable to use 0.1 parts by mass, per 100 parts by mass of water, in order to ensure uniform dispersion of raw cellulose nanofibers in water while improving the production efficiency of modified cellulose nanofibers. On the other hand, the upper limit of the cellulose nanofiber content in the cellulose nanofiber dispersion is determined by appropriately diluting it with water until it can be sufficiently stirred using a stirrer such as a magnetic stirrer. In particular, when determining an appropriate dispersion state based on the stirrer, stirring container, and amount of raw material cellulose nanofiber, 1.0 part by mass is preferred, and 0.8 parts by mass is particularly preferred, in order to ensure that the dispersion of raw material cellulose nanofiber in water is made uniform, and to ensure that the raw material cellulose nanofiber is uniformly modified with a silane coupling agent in the drying process described later.

[0031] One method for dispersing the cellulose nanofiber raw material prepared as described above in water is to add the cellulose nanofiber raw material to water and stir it under predetermined stirring conditions. The stirring conditions can be appropriately selected depending on the size of the cellulose nanofiber raw material and the amount added to the water. For example, stirring temperature can be 10°C to 60°C, stirring time can be 1 minute to 120 minutes, and stirring speed can be 600 rpm to 1350 rpm. The stirring means is not particularly limited and can be a stirrer, impeller, etc.

[0032] (2) Preparation of silane coupling agent-containing dispersion The silane coupling agent-containing dispersion preparation step involves (1) adding a silane coupling agent having epoxy groups to the cellulose nanofiber aqueous dispersion prepared in the cellulose nanofiber dispersion preparation step, in an amount of 0.005 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber, thereby obtaining a dispersion containing raw material cellulose nanofibers and a silane coupling agent. In the production of modified cellulose nanofibers, a cellulose nanofiber dispersion prepared by dispersing hydrophilic raw material cellulose nanofibers in water can be used as the reaction system, eliminating the need for pretreatment of the raw material cellulose nanofibers. Furthermore, the silane coupling agent can be used as a modifier for hydrophobicizing the raw material cellulose nanofibers. Therefore, hydrophobicization of the raw material cellulose nanofibers can be performed with simple operations.

[0033] The silane coupling agent described above is a compound having a functional group and a hydrolyzable silyl group within a single molecule, which reacts with water to convert the hydrolyzable silyl group into a silanol group. The silane coupling agent has substituents for modifying the hydroxyl groups of cellulose that constitute cellulose nanofibers. In the production of modified cellulose nanofibers, the silane coupling agent must have an epoxy group as a functional group. The silanol group of the silane coupling agent chemically bonds with the hydroxyl groups of cellulose that constitute cellulose nanofibers, thereby modifying the hydroxyl groups of cellulose. Cellulose is modified by the silane coupling agent when the silanol group, which is produced by the hydrolysis of the hydrolyzable silyl group of the silane coupling agent, chemically bonds with the hydroxyl groups of cellulose.

[0034] As the hydrolyzable silyl group of the silane coupling agent, an alkoxy group is preferred because it can reliably modify cellulose and produce a modified cellulose nanofiber composition that reliably possesses excellent hydrophobicity. In other words, an organosilicon compound having at least an epoxy group and an alkoxy group is preferred as the silane coupling agent.

[0035] Furthermore, the hydrolyzable silyl group of the silane coupling agent is more preferably one having an alkoxy group and an alkyl group, as this allows for the production of a modified cellulose nanofiber composition that reliably modifies cellulose, thereby reliably imparting excellent hydrophobicity, while reliably suppressing aggregation of modified cellulose nanofibers. In other words, an organosilicon compound having at least an epoxy group, an alkoxy group, and an alkyl group is more preferable as the silane coupling agent. By reliably suppressing aggregation of modified cellulose nanofibers, it is possible to produce a modified cellulose nanofiber composition that can be dispersed more reliably and uniformly in hydrophobic substances such as organic solvents and resins.

[0036] As a silane coupling agent, for example, it is possible to produce modified cellulose nanofibers with reliably improved hydrophobicity, as shown in the general formula (1) below. [ka] (In general formula (1), X represents an organic functional group containing an epoxy group, and R 1 , R 2 , R 3 Each of these independently represents a chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. Compounds represented by ) are preferred. In compounds of general formula (1), R 1 , R 2 , R 3 A hydrolyzable silyl group is formed by a chemical bond between it and Si.

[0037] R in compounds of general formula (1) 1 , R 2 , R 3As such, in order to more reliably modify cellulose nanofibers, an alkoxy group having 1 to 3 carbon atoms or an alkyl group having 1 to 3 carbon atoms is more preferable, and an alkoxy group having 1 to 2 carbon atoms or an alkyl group having 1 to 2 carbon atoms is particularly preferable. Furthermore, in order to produce a modified cellulose nanofiber composition that can more reliably modify cellulose nanofibers and reliably impart excellent hydrophobicity while more reliably suppressing aggregation of modified cellulose nanofibers, the R in the compound of general formula (1) is preferable. 1 , R 2 , R 3 Preferably, at least one of these is an alkoxy group having 1 to 5 carbon atoms, and at least one is an alkyl group having 1 to 5 carbon atoms.

[0038] In the compound of general formula (1), X is not particularly limited as long as it is an organic functional group containing an epoxy group, but in order to reliably produce modified cellulose nanofibers with excellent hydrophobicity, X is as follows: ER 4 -OR 5 - (2) (In general formula (2), E is an epoxy group, R 4 , R 5 Each of these independently represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, preferably an aliphatic hydrocarbon group having 1 to 3 carbon atoms. Organic functional groups represented by ) are preferred.

[0039] Examples of silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyl(dimethoxy)methylsilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Of these, 3-glycidoxypropyl(dimethoxy)methylsilane is preferred because it can produce a modified cellulose nanofiber composition that reliably imparts superior hydrophobicity while more reliably suppressing aggregation between modified cellulose nanofibers.

[0040] In the process of preparing the silane coupling agent-containing dispersion, the amount of silane coupling agent added is not particularly limited as long as it is in the range of 0.005 moles to 6.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. However, the lower limit is preferably 0.01 moles of silane coupling agent per 1.0 mole of β-glucose units of cellulose, more preferably 0.05 moles, and particularly preferably 0.20 moles, in order to reliably impart excellent hydrophobicity to the modified cellulose nanofibers. On the other hand, the upper limit of the amount of silane coupling agent added in the process of preparing the silane coupling agent-containing dispersion is preferably 5.0 moles per 1.0 mole of β-glucose units of cellulose, more preferably 3.0 moles, and particularly preferably 2.0 moles, in order to prevent the residue of silane coupling agent in the silane coupling agent-containing dispersion. The above "β-glucose unit" refers to the constituent unit of cellulose.

[0041] One method for dispersing a silane coupling agent having epoxy groups in a cellulose nanofiber dispersion is to add the silane coupling agent having epoxy groups to the cellulose nanofiber dispersion and stir under predetermined stirring conditions. The stirring conditions can be appropriately selected depending on the size and amount of raw cellulose nanofibers, the amount of silane coupling agent added, the size of the stirring container, the type of stirrer, etc. For example, stirring temperature of 10°C to 60°C, stirring time of 1 minute to 120 minutes, and stirring speed of 600 rpm to 1350 rpm can be used. The stirring time and stirring speed can be determined under appropriate conditions depending on the type of stirrer, the size of the stirring container, the size and amount of raw cellulose nanofibers, etc. Furthermore, the stirring means is not particularly limited and can include, for example, a stirrer, agitator blades, etc.

[0042] (3) Drying process The drying process involves drying the silane coupling agent-containing dispersion obtained in (2) the silane coupling agent-containing dispersion preparation process, thereby modifying the raw material cellulose nanofibers with the silane coupling agent. Modified cellulose nanofibers can be produced by modifying the raw material cellulose nanofibers with the silane coupling agent.

[0043] The drying step involves removing water from the silane coupling agent-containing dispersion obtained in the silane coupling agent-containing dispersion preparation step to obtain the target modified cellulose nanofibers. The modified cellulose nanofibers obtained as described above are formed when the silanol groups of the silane coupling agent, which has epoxy groups, chemically bond to the hydroxyl groups of the cellulose that constitute the raw material cellulose nanofibers through dehydration condensation, thereby modifying the cellulose nanofibers with the silane coupling agent.

[0044] The drying method for the silane coupling agent-containing dispersion is not particularly limited, but freeze-drying is preferred, for example, from the viewpoint of ease of drying. Furthermore, by using freeze-drying, the occurrence of ring-opening reactions of the epoxy groups of the silane coupling agent can be suppressed, so the resulting modified cellulose nanofibers can be further modified via the epoxy groups, and the range of hydrophobic substances to which they can be applied can be easily expanded according to the properties of the hydrophobic substances. In addition, freeze-drying can be used to more reliably produce modified cellulose nanofibers that have excellent affinity for hydrophobic substances.

[0045] The conditions for freeze-drying are not particularly limited, but examples include a predetermined freezing temperature, reduced pressure (vacuum level) of 30 Pa or less, and a freeze-drying time of 72 hours to 120 hours.

[0046] Regarding optional processes In the above-described method for producing modified cellulose nanofibers, in addition to (1) the step of preparing a cellulose nanofiber dispersion, (2) the step of preparing a silane coupling agent-containing dispersion, and (3) the drying step, other steps may be added as needed.

[0047] Other steps that may be added as needed include, for example, a dialysis step between (2) the silane coupling agent-containing dispersion preparation step and (3) the drying step, in which the silane coupling agent-containing dispersion is dialyzed using a dialysis membrane. By further including a dialysis step, unreacted silane coupling agent and by-products remaining in the silane coupling agent-containing dispersion can be removed by dialysis, thereby improving the purity of the modified cellulose nanofibers.

[0048] The dialysis time in the dialysis process is not particularly limited, but for example, 48 hours or more is preferred in order to more reliably remove the silane coupling agent remaining in the silane coupling agent-containing dispersion, and 48 hours to 120 hours is particularly preferred in order to more reliably remove the silane coupling agent while reliably obtaining the production efficiency of modified cellulose nanofibers.

[0049] As dialysis membranes used in the dialysis process, for example, regenerated cellulose (RC), polystyrene (PS), polymethyl methacrylate (PMMA), cellulose triacetate (CTA), polyethersulfone (PES), polyester polymer alloy (PEPA), sodium acrylonitrile methacrylate polymer (AN69), and ethylene vinyl alcohol polymer (EVAL) are preferred because they have high hydrophilicity and high strength, allowing for dialysis in water.

[0050] <Modified cellulose nanofibers> The modified cellulose nanofibers obtained by the above-described manufacturing method are cellulose nanofibers modified with a silane coupling agent having epoxy groups. More specifically, the modified cellulose nanofibers obtained by the above-described manufacturing method are modified cellulose nanofibers in which the cellulose nanofibers are modified with a silane coupling agent, by chemical bonding of the silanol groups of the silane coupling agent having epoxy groups to the hydroxyl groups of cellulose through dehydration condensation.

[0051] The amount of silane coupling agent added to the modified cellulose nanofibers obtained by the above manufacturing method is not particularly limited as long as it is in the range of 0.005 moles to 6.0 moles per 1.0 mole of cellulose nanofiber β-glucose units. However, the lower limit is preferably 0.01 moles of silane coupling agent per 1.0 mole of cellulose β-glucose units, more preferably 0.05 moles, and particularly preferably 0.20 moles, from the standpoint of reliably imparting excellent hydrophobicity to the cellulose. On the other hand, the upper limit of the amount of silane coupling agent added to the modified cellulose nanofibers is preferably 5.0 moles per 1.0 mole of cellulose β-glucose units, from the standpoint of preventing loss of high strength by maintaining the crystalline structure of the cellulose nanofibers, and particularly preferably 3.0 moles per 1.0 mole of cellulose β-glucose units, from the standpoint of more reliably maintaining the crystalline structure of the cellulose nanofibers. The above-mentioned ratio of silane coupling agent to be added represents the ratio of silane coupling agent units to one β-glucose molecule, which is a constituent unit of cellulose.

[0052] The size of the modified cellulose nanofibers obtained by the above-described manufacturing method is not particularly limited, but corresponding to the average fiber diameter of the raw material cellulose nanofibers being less than 1.0 μm, for example, an average fiber diameter of less than 1.0 μm is preferred. The size of the modified cellulose nanofibers corresponds to the average fiber diameter of the raw material cellulose nanofibers described above, and from the viewpoint of homogenizing the cellulose modification sites by the silane coupling agent and expanding the range of application of the modified cellulose nanofibers, the average fiber diameter is preferably 4 nm to 100 nm, and particularly preferably 10 nm to 50 nm. Furthermore, the average fiber length of the modified cellulose nanofibers corresponds to the average fiber length of the raw material cellulose nanofibers described above, and from the viewpoint of homogenizing the cellulose modification sites by the silane coupling agent and expanding the range of application of the modified cellulose nanofibers, the average fiber length is preferably 20 μm to 200 μm, and particularly preferably 50 μm to 150 μm.

[0053] The fact that modified cellulose nanofibers could be produced by modifying raw cellulose nanofibers with a silane coupling agent, that is, that cellulose nanofibers could be modified by modifying them with a silane coupling agent, can be confirmed by visually observing the dispersion state of the modified cellulose nanofibers in the organic solvent immediately after dispersing them in the organic solvent, and by visually observing the time required for the modified cellulose nanofibers to aggregate and settle in the organic solvent after dispersing them in the organic solvent. If the time required for the modified cellulose nanofibers to aggregate and settle in the organic solvent is longer than a predetermined time, it is proven that the modified cellulose nanofibers have excellent dispersibility in the organic solvent and are modified with the silane coupling agent.

[0054] Examples of organic solvents used to confirm the successful production of modified cellulose nanofibers modified with a silane coupling agent include tetrahydrofuran, acetone, ethanol, propanol, and other C1-C5 alcohols.

[0055] Furthermore, the successful production of modified cellulose nanofibers by modifying raw cellulose nanofibers with a silane coupling agent can be confirmed by Fourier transform infrared spectroscopy (FT-IR). Specifically, by comparing the infrared absorption spectrum of raw cellulose nanofibers not modified with a silane coupling agent with the infrared absorption spectrum of the obtained modified cellulose nanofibers, it can be confirmed that at least some of the hydroxyl groups of cellulose are modified by a silane coupling agent containing epoxy groups.

[0056] Specifically, in modified cellulose nanofibers modified with a silane coupling agent, if the silane coupling agent has an alkyl group, the infrared absorption spectrum at 1260 cm² is... -1 , 798cm -1 , 763cm -1 In the region where absorption peaks originating from Si-C bonds appear, in the raw material cellulose nanofiber, 1260 cm² -1 , 798cm -1 , 763cm -1 No absorption peak appears in this region. Therefore, the infrared absorption spectrum at 1260 cm⁻¹ -1 , 798cm -1 , 763cm -1 By checking for the presence or absence of absorption peaks in this region, it is possible to confirm whether or not modified cellulose nanofibers modified with a silane coupling agent have been produced, that is, whether or not cellulose nanofibers have been modified with a silane coupling agent.

[0057] Furthermore, in modified cellulose nanofibers modified with a silane coupling agent having an epoxy group, even when the silane coupling agent does not have an alkyl group, the infrared absorption spectrum at 900 cm² is -1 Absorption peaks originating from epoxy groups appear in the surrounding region. Even with the raw material cellulose nanofiber, the infrared absorption spectrum is 900 cm². -1 An absorption peak appears in the surrounding region, but in modified cellulose nanofibers, at 900 cm². -1In the surrounding region, the absorption peaks originating from epoxy groups and raw cellulose nanofibers overlap, resulting in increased peak intensity. Therefore, 900 cm² -1 By checking the peak intensity in the surrounding region, it is possible to confirm whether or not modified cellulose nanofibers modified with an epoxy-grouped silane coupling agent were produced, that is, whether or not cellulose nanofibers were modified with an epoxy-grouped silane coupling agent.

[0058] The modified cellulose nanofibers used in the method for producing the modified cellulose nanofiber composition of the present invention are endowed with excellent hydrophobicity and have excellent affinity for hydrophobic substances, thus exhibiting excellent mixing and dispersibility with hydrophobic substances such as resins. Furthermore, even though the modified cellulose nanofibers used in the method for producing the modified cellulose nanofiber composition of the present invention are modified, the change in the molecular structure of the cellulose nanofibers themselves is suppressed, thus maintaining the original properties of the cellulose nanofibers. Therefore, the modified cellulose nanofibers used in the method for producing the modified cellulose nanofiber composition of the present invention have high strength and, for example, exhibit excellent functionality as a reinforcing material for hydrophobic substances.

[0059] Next, the details of the method for producing the modified cellulose nanofiber composition of the present invention will be described below. First, a first aspect of the method for producing the modified cellulose nanofiber composition of the present invention will be described.

[0060] <First aspect of a method for producing a modified cellulose nanofiber composition> A first aspect of the method for producing a modified cellulose nanofiber composition includes (A1) a dispersion medium preparation step of preparing a dispersion medium, (B1) a cellulose derivative addition step of adding a cellulose derivative to the prepared dispersion medium to prepare a cellulose derivative-containing solution, and (C1) a modified cellulose nanofiber addition step of adding the modified cellulose nanofibers produced as described above to the cellulose derivative-containing solution in a range of 100 parts by mass of the modified cellulose nanofibers to 10 to 2000 parts by mass of the cellulose derivative. In the first aspect, after adding a predetermined amount of cellulose derivative to the dispersion medium, the modified cellulose nanofibers produced by the production method having steps (1) to (3) above are added to produce a modified cellulose nanofiber composition. In the modified cellulose nanofiber composition obtained by the method for producing a modified cellulose nanofiber composition of the present invention, the cellulose derivative is dissolved in the dispersion medium and the modified cellulose nanofibers are dispersed in the dispersion medium.

[0061] According to the first aspect of the method for producing a modified cellulose nanofiber composition, the modified cellulose nanofibers exhibit excellent dispersibility in the simple manufacturing process described in (A1) to (C1) above, allowing for easy expansion of the application range of cellulose. Furthermore, the modified cellulose nanofiber composition can be produced with excellent hydrophobicity, resulting in superior affinity to hydrophobic substances. The first aspect of the method for producing a modified cellulose nanofiber composition of the present invention allows for uniform dispersion of the modified cellulose nanofibers into the target hydrophobic substance, and ensures that the properties of the cellulose nanofibers are reliably imparted to the target. Moreover, the first aspect of the method for producing a modified cellulose nanofiber composition of the present invention allows for the production of the modified cellulose nanofiber composition in a simple production process, resulting in excellent production efficiency. Furthermore, the first aspect of the method for producing a modified cellulose nanofiber composition of the present invention allows for the production of a modified cellulose nanofiber composition having highly reactive epoxy groups as functional groups. Therefore, the obtained modified cellulose nanofiber composition can be further modified via the epoxy groups. Consequently, the range of hydrophobic substances to which it can be applied can be easily expanded.

[0062] (A1) Dispersion medium preparation process The dispersion medium functions to disperse the modified cellulose nanofibers in the modified cellulose nanofiber composition and also as a medium for dissolving the cellulose derivative. Examples of dispersion liquids prepared in the dispersion medium preparation step include organic solvents. Examples of organic solvents include C1-C5 alcohols such as tetrahydrofuran, acetone, ethanol, and propanol, cyclohexanol, propylene glycol, acetone, cyclohexanone, dioxane, cellosolve, butyl cellosolve, glacial acetic acid, formic acid, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, methylene chloride, chloroform, a mixture of benzene:methanol (1:1 volume ratio), a mixture of toluene:ethanol (3:2 volume ratio), and a mixture of glycerin:water (3:7 volume ratio). Water can also be used as the dispersion medium. These various dispersion media may be used individually or in combination of two or more. Furthermore, as the dispersion prepared in the dispersion medium preparation step, a solution obtained by mixing organic solvents that are miscible with water in any proportion may be used.

[0063] (B1) Cellulose derivative addition process The cellulose derivative addition step involves adding a predetermined amount of cellulose derivative to a dispersion medium to prepare a cellulose derivative-containing solution in which the cellulose derivative is dissolved in the dispersion medium. The cellulose derivative added to the dispersion medium is a different component from modified cellulose nanofibers in that it is a compound in which cellulose is modified with a chemical structure other than a silane coupling agent having an epoxy group. The cellulose derivative is dissolved in the dispersion medium within the modified cellulose nanofiber composition. Because the cellulose derivative is dissolved in the dispersion medium within the modified cellulose nanofiber composition, it is thought that the hydroxyl groups of the cellulose derivative interact with the hydroxyl groups of the modified cellulose nanofibers added to the cellulose derivative-containing solution in the subsequent step (C) modified cellulose nanofiber addition step, resulting in a state in which the cellulose derivative is coordinated to the modified cellulose nanofibers. Furthermore, since both modified cellulose nanofibers and cellulose derivatives have a cellulose backbone, their molecular structures are similar. Therefore, it is thought that modified cellulose nanofibers have a high affinity for cellulose derivatives, making it easy for the cellulose derivative to coordinate to the modified cellulose nanofibers. It is believed that the cellulose derivative is coordinated to the modified cellulose nanofiber, allowing the surfactant properties of the cellulose derivative to be exhibited, resulting in the modified cellulose nanofiber having excellent dispersibility within the modified cellulose nanofiber composition.

[0064] Furthermore, the modified cellulose nanofiber composition obtained by the manufacturing method of the present invention uses a cellulose derivative, which is a biocompatible material, thus reducing environmental impact and offering excellent safety.

[0065] The cellulose derivative is not particularly limited as long as it is a derivative obtained by a chemical reaction of at least some of the hydroxyl groups of cellulose, and examples include hydroxyalkylcellulose, alkylcellulose, carboxyalkylcellulose, and hydroxyalkylalkylcellulose. Of these, hydroxyalkylcellulose and alkylcellulose are preferred because they can reliably obtain excellent dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition, and hydroxyalkylcellulose is particularly preferred because it more reliably improves the dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition. As the cellulose derivative, for example, hydroxyalkylcellulose and alkylcellulose may be used in combination, or either may be used alone.

[0066] Examples of hydroxyalkylcellulose include hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxybutylcellulose, hydroxypentylcellulose, and hydroxyhexylcellulose. These compounds may be used individually or in combination of two or more. Of these, hydroxyethylcellulose and hydroxypropylcellulose are preferred, and hydroxypropylcellulose is particularly preferred, as they further improve the dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition.

[0067] Examples of alkylcelluloses include methylcellulose, ethylcellulose, propylcellulose, butylcellulose, pentylcellulose, and hexylcellulose. These compounds may be used individually or in combination of two or more. Of these, methylcellulose and ethylcellulose are preferred, and ethylcellulose is particularly preferred, as they allow for more reliable acquisition of the excellent dispersibility of modified cellulose nanofibers.

[0068] Examples of carboxyalkylcellulose include carboxymethylcellulose, carboxyethylcellulose, carboxypropylcellulose, carboxybutylcellulose, carboxypentylcellulose, and carboxyhexylcellulose.

[0069] Hydroxyalkylalkylcellulose is a type of cellulose having both a hydroxyalkyl and an alkyl group. Examples of hydroxyalkylalkylcellulose include cellulose having both a hydroxymethyl and an alkyl group, such as hydroxymethylmethylcellulose, hydroxymethylethylcellulose, hydroxymethylpropylcellulose, and hydroxymethylbutylcellulose; cellulose having both a hydroxyethyl and an alkyl group, such as hydroxyethylmethylcellulose, hydroxyethylethylcellulose, hydroxyethylpropylcellulose, and hydroxyethylbutylcellulose; cellulose having both a hydroxypropyl and an alkyl group, such as hydroxypropylmethylcellulose, hydroxypropylethylcellulose, hydroxypropylpropylcellulose, and hydroxypropylbutylcellulose; and cellulose having both a hydroxybutyl and an alkyl group, such as hydroxybutylmethylcellulose, hydroxybutylethylcellulose, hydroxybutylpropylcellulose, and hydroxybutylbutylcellulose.

[0070] One method for preparing a cellulose derivative-containing solution is to add the cellulose derivative to a dispersion medium and stir under predetermined stirring conditions to dissolve the cellulose derivative in the dispersion medium. The stirring conditions can be appropriately selected depending on the molecular weight and amount of the cellulose derivative, the size of the stirring container, the type of stirrer, etc., and are not particularly limited, but examples include a stirring temperature of 10°C to 60°C, a stirring time of 1 minute to 120 minutes, and a stirring speed of 600 rpm to 1350 rpm. The stirring time and stirring speed can be set appropriately depending on the type of stirrer, the size of the stirring container, the molecular weight and amount of the cellulose derivative, etc. Furthermore, the stirring means are not particularly limited and examples include stirrers and impellers.

[0071] The amount of cellulose derivative added to the dispersion medium is not particularly limited, but the lower limit is preferably 0.5 parts by mass, more preferably 2.0 parts by mass, and especially preferably 3.0 parts by mass, per 100 parts by mass of the dispersion medium, in order to reliably obtain excellent dispersibility of the modified cellulose nanofibers. On the other hand, the upper limit of the amount of cellulose derivative added to the dispersion medium is preferably 120 parts by mass, more preferably 75 parts by mass, and especially preferably 50 parts by mass, per 100 parts by mass of the dispersion medium, in order to reliably impart the properties of the modified cellulose nanofibers to the target application.

[0072] (C1) Modified cellulose nanofiber addition process The modified cellulose nanofiber addition step involves adding modified cellulose nanofibers to the cellulose derivative-containing solution obtained as described above. By adding modified cellulose nanofibers to the cellulose derivative-containing solution and dispersing the modified cellulose nanofibers in the cellulose derivative-containing solution, a modified cellulose nanofiber composition can be produced.

[0073] Modified cellulose nanofibers can be produced by a manufacturing method comprising steps (1) to (3) of the above-described method for producing modified cellulose nanofibers. As a method for adding and dispersing modified cellulose nanofibers in a cellulose derivative-containing solution, for example, a method can be used in which modified cellulose nanofibers are added to a cellulose derivative-containing solution and stirred under predetermined stirring conditions. The stirring conditions can be appropriately selected depending on the molecular weight and amount of modified cellulose nanofibers added, the size of the stirring container, the type of stirrer, etc., and are not particularly limited, but for example, a stirring temperature of 10°C to 60°C, a stirring time of 1 minute to 120 minutes, and a stirring speed of 600 rpm to 1350 rpm can be used. The stirring time and stirring speed can be set appropriately depending on the type of stirrer, the size of the stirring container, the molecular weight and amount of modified cellulose nanofibers added, etc. Furthermore, the stirring means are not particularly limited, and for example, a stirrer, a stirring blade, etc.

[0074] The amount of modified cellulose nanofiber added to the dispersion medium is not particularly limited and can be appropriately selected depending on the usage conditions of the cellulose nanofiber composition and the dispersion state of the cellulose nanofiber in the dispersion medium.

[0075] The ratio of cellulose derivative to modified cellulose nanofibers is not particularly limited as long as it is in the range of 10 parts by mass or more and 2000 parts by mass of cellulose derivative per 100 parts by mass of modified cellulose nanofibers. However, the lower limit is preferably 30 parts by mass, more preferably 40 parts by mass, and particularly preferably 50 parts by mass of cellulose derivative per 100 parts by mass of modified cellulose nanofibers, in order to reliably obtain excellent dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition. On the other hand, the upper limit of the ratio of cellulose derivative to modified cellulose nanofibers is preferably 1800 parts by mass, more preferably 1600 parts by mass, and particularly preferably 1500 parts by mass of cellulose derivative per 100 parts by mass of modified cellulose nanofibers, in order to reliably impart the properties of the modified cellulose nanofibers to the target and to reliably obtain excellent dispersibility of the modified cellulose nanofibers.

[0076] <Second aspect of the method for producing a modified cellulose nanofiber composition> A second aspect of the method for producing a modified cellulose nanofiber composition includes (A2) a dispersion medium preparation step of preparing a dispersion medium, (B2) a modified cellulose nanofiber addition step of adding modified cellulose nanofibers to the prepared dispersion medium to prepare a modified cellulose nanofiber-containing dispersion medium, and (C2) a cellulose derivative addition step of adding a cellulose derivative to the modified cellulose nanofiber-containing dispersion medium in an amount of 100 parts by mass of the modified cellulose nanofibers to 10 to 2000 parts by mass of the cellulose derivative. In the second aspect, a predetermined amount of modified cellulose nanofibers is added to the dispersion medium to disperse the modified cellulose nanofibers in the dispersion medium to prepare a modified cellulose nanofiber-containing dispersion medium, and then a cellulose derivative is added to the modified cellulose nanofiber-containing dispersion medium and dissolved to produce a modified cellulose nanofiber composition. Therefore, the second aspect differs from the first aspect in that the order of addition of the modified cellulose nanofibers and the cellulose derivative to the dispersion medium is different, but in other respects, it is the same as the first aspect described above, including the amount of each component to be added and the stirring conditions. In the second embodiment as well, the modified cellulose nanofibers can be manufactured by a manufacturing method comprising the steps (1) to (3) described above.

[0077] In the second embodiment of the method for producing a modified cellulose nanofiber composition, the resulting modified cellulose nanofiber composition is in which the cellulose derivative is dissolved in the dispersion medium and the modified cellulose nanofibers are dispersed in the dispersion medium.

[0078] In the second embodiment of the method for producing a modified cellulose nanofiber composition, the modified cellulose nanofibers exhibit excellent dispersibility in the simple manufacturing process described in (A2) to (C2) above, the range of applications for cellulose can be easily expanded, and a modified cellulose nanofiber composition with excellent hydrophobicity and affinity to hydrophobic substances can be produced by imparting excellent hydrophobicity to the cellulose nanofibers. In the second embodiment of the method for producing a modified cellulose nanofiber composition, the dispersion of the modified cellulose nanofibers in the hydrophobic substance to be applied can be made uniform, and the properties of the cellulose nanofibers can be reliably imparted to the application.

[0079] <Third aspect of the method for producing a modified cellulose nanofiber composition> A third aspect of the method for producing a modified cellulose nanofiber composition includes (A3) a dispersion medium preparation step of preparing a dispersion medium, and (B3) a cellulose component addition step of adding a cellulose derivative and modified cellulose nanofibers as cellulose components to the prepared dispersion medium in an amount of 100 parts by mass of the modified cellulose nanofibers and 10 to 2000 parts by mass of the cellulose derivative. In the third aspect, the modified cellulose nanofiber composition is produced by adding the modified cellulose nanofibers and the cellulose derivative to the dispersion medium, dissolving the cellulose derivative in the dispersion medium, and dispersing the modified cellulose nanofibers in the dispersion medium. Therefore, the third aspect differs from the first aspect in that the modified cellulose nanofibers and the cellulose derivative are added to the dispersion medium simultaneously, but in other respects, it is the same as the first aspect described above, including the amount of each component added and the stirring conditions. In the third aspect as well, the modified cellulose nanofibers can be produced by the production method having the steps (1) to (3) above.

[0080] In the third embodiment, the modified cellulose nanofibers and the cellulose derivatives may be added to the dispersion medium via different input routes. For example, a cellulose component containing the modified cellulose nanofibers and the cellulose derivative may be prepared first, and this cellulose component may be added to the dispersion medium.

[0081] In the third embodiment of the method for producing a modified cellulose nanofiber composition, the resulting modified cellulose nanofiber composition is in which the cellulose derivative is dissolved in the dispersion medium and the modified cellulose nanofibers are dispersed in the dispersion medium.

[0082] In the third embodiment of the method for producing a modified cellulose nanofiber composition, the modified cellulose nanofibers exhibit excellent dispersibility, the range of applications for cellulose can be easily expanded, and excellent hydrophobicity is imparted to the cellulose nanofibers, resulting in a modified cellulose nanofiber composition with excellent affinity to hydrophobic substances. In the third embodiment of the method for producing a modified cellulose nanofiber composition, the dispersion of the modified cellulose nanofibers in the hydrophobic substance to be applied can be made uniform, and the properties of the cellulose nanofibers can be reliably imparted to the application.

[0083] In the modified cellulose nanofiber compositions obtained by the manufacturing methods according to the first to third aspects of the present invention, the cellulose derivative is dissolved in the dispersion medium, and the modified cellulose nanofibers are dispersed in the dispersion medium, resulting in a state where the cellulose derivative is coordinated to the modified cellulose nanofibers. Therefore, the modified cellulose nanofibers in the modified cellulose nanofiber composition have excellent dispersibility. From the above, the aspects of the modified cellulose nanofiber compositions obtained by the manufacturing methods according to the first to third aspects of the present invention are dispersions of modified cellulose nanofibers, for example, dispersions in which modified cellulose nanofibers are dispersed in an organic solvent.

[0084] <Fourth aspect of the method for producing a modified cellulose nanofiber composition> A fourth aspect of the method for producing a modified cellulose nanofiber composition includes (A4) a dispersion medium preparation step of preparing a dispersion medium, and (B4) a modified cellulose nanofiber addition step of adding the modified cellulose nanofibers to the prepared dispersion medium to prepare a modified cellulose nanofiber-containing dispersion medium. In the fourth aspect of the method for producing a modified cellulose nanofiber composition, in the silane coupling agent-containing dispersion preparation step of the steps for producing modified cellulose nanofibers, a silane coupling agent having epoxy groups is added to the cellulose nanofiber dispersion at a rate of 5.0 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofibers to obtain a silane coupling agent-containing dispersion.

[0085] In the fourth embodiment, a modified cellulose nanofiber is used, to which a silane coupling agent is added in an amount of 5.0 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber, and this modified cellulose nanofiber is added to the dispersion medium. The fourth embodiment differs from the first to third embodiments in that no cellulose derivative is added. Therefore, in the fourth embodiment, a modified cellulose nanofiber composition is produced by dispersing the modified cellulose nanofiber as the cellulose component in the dispersion medium.

[0086] In the fourth embodiment of the method for producing a modified cellulose nanofiber composition, the modified cellulose nanofibers exhibit excellent dispersibility in the simple manufacturing process described in (A4) to (B4) above, the range of applications for cellulose can be easily expanded, and a modified cellulose nanofiber composition with excellent hydrophobicity and affinity to hydrophobic substances can be produced by imparting excellent hydrophobicity to the cellulose nanofibers. In the fourth embodiment of the method for producing a modified cellulose nanofiber composition, the dispersion of the modified cellulose nanofibers in the hydrophobic substance to be applied can be made uniform, and the properties of the cellulose nanofibers can be reliably imparted to the application.

[0087] A modified cellulose nanofiber composition obtained by a manufacturing method according to a fourth aspect of the present invention is a dispersion of modified cellulose nanofibers, for example, a dispersion in which modified cellulose nanofibers are dispersed in an organic solvent.

[0088] The dispersion state of modified cellulose nanofibers in a dispersion of modified cellulose nanofibers obtained by the manufacturing method of the present invention can be evaluated by measuring the transmittance of light at a wavelength of 400 nm. The lower the dispersibility of the modified cellulose nanofibers in the dispersion, and the more the modified cellulose nanofibers aggregate at the bottom of the dispersion, the higher the transmittance of light at a wavelength of 400 nm measured in the center of the vertical direction of the dispersion. On the other hand, the higher the dispersibility of the modified cellulose nanofibers in the dispersion, and the reduced aggregation of the modified cellulose nanofibers, i.e., the more uniform the dispersion of the modified cellulose nanofibers, the lower the transmittance of light at a wavelength of 400 nm measured in the center of the vertical direction of the dispersion.

[0089] The average value of the transmittance of light at a wavelength of 400 nm in a dispersion of modified cellulose nanofibers at a stirring speed of 1000 rpm is preferably less than 5.0, more preferably less than 2.0, and particularly preferably less than 1.0, as this ensures excellent dispersibility of the modified cellulose nanofibers. A lower limit of the above-mentioned average value of light transmittance can be, for example, 0.02.

[0090] The dispersion state of modified cellulose nanofibers in the dispersion obtained by the manufacturing method of the present invention can be evaluated by measuring the standard deviation of light transmittance at a wavelength of 400 nm at a stirring speed of 1000 rpm. The lower the dispersibility of the modified cellulose nanofibers in the dispersion, and the more likely the modified cellulose nanofibers are to aggregate at the bottom of the dispersion, the lower the dispersion stability of the modified cellulose nanofibers, and the higher the standard deviation of transmittance. On the other hand, the lower the aggregation state of the modified cellulose nanofibers and the more uniform the dispersion of the modified cellulose nanofibers, the higher the dispersion stability of the modified cellulose nanofibers, and the lower the standard deviation of transmittance.

[0091] The standard deviation of the transmittance of light at a wavelength of 400 nm at a stirring speed of 1000 rpm of the dispersion of modified cellulose nanofibers is preferably less than 1.0, more preferably less than 0.80, and even more preferably less than 0.60, and particularly preferably less than 0.50, in that the excellent dispersibility of the modified cellulose nanofibers is reliably obtained.

[0092] <Molded product of modified cellulose nanofiber film> After forming the modified cellulose nanofiber composition obtained by the manufacturing method of the present invention into a predetermined shape, a modified cellulose nanofiber molded product of the predetermined shape can be obtained by removing the dispersion medium from the modified cellulose nanofiber composition by drying or other means. In the modified cellulose nanofiber composition obtained by the manufacturing method of the present invention, the aggregation state of the modified cellulose nanofibers is reduced and the dispersion of the modified cellulose nanofibers is made uniform. Therefore, the modified cellulose nanofiber molded product obtained by removing the dispersion medium from the modified cellulose nanofiber composition obtained by the manufacturing method of the present invention has a uniform distribution of modified cellulose nanofibers and a smooth surface. Furthermore, the modified cellulose nanofiber composition obtained by the manufacturing method of the present invention has not only excellent dispersibility of modified cellulose nanofibers but also appropriate fluidity, so a film-like molded product can be easily obtained. [Examples]

[0093] Next, embodiments of the present invention will be described, but the present invention is not limited to these examples unless it exceeds the spirit of the invention.

[0094] <Manufacturing of Modified Cellulose Nanofiber Composition> Example 1 A cellulose nanofiber aqueous dispersion (average fiber length 100 μm, average fiber diameter 30-40 nm, manufactured by Mori Machinery Co., Ltd., "CellFim C-100 (moisture content approximately 95% by mass)") was dispersed at a rate of 1.0 g in 300 g of water to prepare a cellulose nanofiber dispersion (cellulose nanofiber dispersion preparation step). The prepared cellulose nanofiber dispersion was stirred with a stirrer at a stirring speed of 1350 rpm at room temperature, and 3-glycidoxypropyl (dimethoxy)methylsilane (hereinafter sometimes referred to as "GOPDMS," which corresponds to a silane coupling agent having an epoxy group) was added at a rate of 0.005 moles per 1.0 mole of β-glucose units of cellulose nanofibers. The mixture was then stirred for a predetermined time to prepare a silane coupling agent-containing dispersion in which the cellulose nanofibers and the silane coupling agent were dispersed in water (silane coupling agent-containing dispersion preparation step). The obtained silane coupling agent-containing dispersion was dialyzed in pure water using a dialysis membrane. Dialysis using a dialysis membrane was performed for 24 hours. From the addition of GOPDMS to the end of dialysis using the dialysis membrane, the process was carried out at room temperature of 25°C (dialysis process). The dialysis-treated silane coupling agent-containing dispersion was dried in a freeze-dryer under predetermined freezing temperature, reduced pressure conditions (vacuum level) of 10 Pa, and freeze-drying time of 72 hours, thereby sublimating the water in the frozen silane coupling agent-containing dispersion (drying process). In this way, modified cellulose nanofibers used in Example 1, which were modified with GOPDMS, were produced.

[0095] The modification of cellulose nanofibers with GOPDMS was confirmed by analyzing the obtained modified cellulose nanofibers using FT-IR (PerkinElmer Corporation's "Spectrum One(A)"), and the obtained infrared absorption spectrum was found at 1260 cm⁻¹. -1 , 798cm -1 , 763cm -1 Absorption peaks originating from Si-C bonds appear in this region, and compared to cellulose nanofibers before modification with GOPDMS, the infrared absorption spectrum at 900 cm² is different. -1This was confirmed by the strong peak intensity in the surrounding area.

[0096] 0.01 g of hydroxypropyl cellulose (cellulose derivative) was added to 20 ml of tetrahydrofuran (dispersion medium) and stirred to dissolve the hydroxypropyl cellulose in tetrahydrofuran and prepare a cellulose derivative-containing solution. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:0.1) prepared as described above was added to the cellulose derivative-containing solution and stirred for 24 hours to produce the modified cellulose nanofiber composition of Example 1, which is a dispersion of modified cellulose nanofibers.

[0097] Example 2 The modified cellulose nanofiber composition of Example 2 was prepared in the same manner as in Example 1, except that 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber to hydroxypropyl cellulose = 1:0.5) was added to a cellulose derivative-containing solution prepared by adding 0.05 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium).

[0098] Example 3 The modified cellulose nanofiber composition of Example 3 was prepared in the same manner as in Example 1, except that 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber to hydroxypropyl cellulose = 1:1) was added to a cellulose derivative-containing solution prepared by adding 0.1 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium).

[0099] Example 4 The modified cellulose nanofiber composition of Example 4 was prepared in the same manner as in Example 1, except that 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber to hydroxypropyl cellulose = 1:5) was added to a cellulose derivative-containing solution prepared by adding 0.5 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium).

[0100] Example 5 The modified cellulose nanofiber composition of Example 5 was prepared in the same manner as in Example 1, except that 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber to hydroxypropyl cellulose = 1:10) was added to a cellulose derivative-containing solution prepared by adding 1.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium).

[0101] Example 6 The modified cellulose nanofiber composition of Example 6 was prepared in the same manner as in Example 1, except that 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber to hydroxypropyl cellulose = 1:20) was added to a cellulose derivative-containing solution prepared by adding 2.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium).

[0102] Example 7 The modified cellulose nanofiber composition of Example 7 was prepared in the same manner as in Example 1, except that GOPDMS was added at a rate of 1.0 mole per 1.0 mole of β-glucose units of the cellulose nanofiber.

[0103] Example 8 GOPDMS was added at a rate of 1.0 mole per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:0.5) was added to a cellulose derivative-containing solution prepared by adding 0.05 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 8 was prepared in the same manner as in Example 1.

[0104] Example 9 GOPDMS was added at a rate of 1.0 mole per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:1) was added to a cellulose derivative-containing solution prepared by adding 0.1 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 9 was prepared in the same manner as in Example 1.

[0105] Example 10 GOPDMS was added at a rate of 1.0 mole per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:5) was added to a cellulose derivative-containing solution prepared by adding 0.5 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 10 was prepared in the same manner as in Example 1.

[0106] Example 11 GOPDMS was added at a rate of 1.0 mole per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:10) was added to a cellulose derivative-containing solution prepared by adding 1.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 11 was prepared in the same manner as in Example 1.

[0107] Example 12 GOPDMS was added at a rate of 1.0 mole per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:20) was added to a cellulose derivative-containing solution prepared by adding 2.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 12 was prepared in the same manner as in Example 1.

[0108] Example 13 GOPDMS was added at a rate of 3.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber. Except as described above, the modified cellulose nanofiber composition of Example 13 was prepared in the same manner as in Example 1.

[0109] Example 14 GOPDMS was added at a rate of 3.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:0.5) was added to a cellulose derivative-containing solution prepared by adding 0.05 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 14 was prepared in the same manner as in Example 1.

[0110] Example 15 GOPDMS was added at a rate of 3.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:1) was added to a cellulose derivative-containing solution prepared by adding 0.1 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 15 was prepared in the same manner as in Example 1.

[0111] Example 16 GOPDMS was added at a rate of 3.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:5) was added to a cellulose derivative-containing solution prepared by adding 0.5 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 16 was prepared in the same manner as in Example 1.

[0112] Example 17 GOPDMS was added at a rate of 3.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:10) was added to a cellulose derivative-containing solution prepared by adding 1.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 17 was prepared in the same manner as in Example 1.

[0113] Example 18 GOPDMS was added at a rate of 3.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:20) was added to a cellulose derivative-containing solution prepared by adding 2.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 18 was prepared in the same manner as in Example 1.

[0114] Example 19 GOPDMS was added at a rate of 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber. Except as described above, the modified cellulose nanofiber composition of Example 19 was prepared in the same manner as in Example 1.

[0115] Example 20 GOPDMS was added at a rate of 6.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:0.5) was added to a cellulose derivative-containing solution prepared by adding 0.05 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 20 was prepared in the same manner as in Example 1.

[0116] Example 21 GOPDMS was added at a rate of 6.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:1) was added to a cellulose derivative-containing solution prepared by adding 0.1 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 21 was prepared in the same manner as in Example 1.

[0117] Example 22 GOPDMS was added at a rate of 6.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:5) was added to a cellulose derivative-containing solution prepared by adding 0.5 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 22 was prepared in the same manner as in Example 1.

[0118] Example 23 GOPDMS was added at a rate of 6.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:10) was added to a cellulose derivative-containing solution prepared by adding 1.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 23 was prepared in the same manner as in Example 1.

[0119] Example 24 GOPDMS was added at a rate of 6.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers to hydroxypropyl cellulose = 1:20) was added to a cellulose derivative-containing solution prepared by adding 2.0 g of hydroxypropyl cellulose (cellulose derivative) to 20 ml of tetrahydrofuran (dispersion medium). Except as described above, the modified cellulose nanofiber composition of Example 24 was prepared in the same manner as in Example 1.

[0120] Example 25 The modified cellulose nanofiber composition of Example 25 was prepared in the same manner as in Example 19, except that 0.1 g of modified cellulose nanofiber was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0121] Comparative Example 1 A modified cellulose nanofiber composition of Comparative Example 1 was prepared in the same manner as in Example 1, except that 0.1 g of modified cellulose nanofiber was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0122] Comparative Example 2 A modified cellulose nanofiber composition for Comparative Example 2 was prepared in the same manner as in Example 7, except that 0.1 g of modified cellulose nanofiber was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0123] Comparative Example 3 A modified cellulose nanofiber composition for Comparative Example 3 was prepared in the same manner as in Example 13, except that 0.1 g of modified cellulose nanofiber was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0124] <Evaluation Criteria> (1) Transmittance of light with a wavelength of 400 nm For the modified cellulose nanofiber compositions of Examples 1-25 and Comparative Examples 1-3, 2.0 ml was placed in a 4.5 ml container and stirred at 1000 rpm using a stirrer with a diameter of 9 mm and a height of 6.5 mm at 25°C. During stirring, 400 nm light was shone onto the central part of the modified cellulose nanofiber composition in the height direction with a path length of 1 cm. The transmittance of 400 nm light was measured from the radiant intensity of the incident light (I0) and the radiant intensity of the light transmitted through the cellulose nanofiber composition (I). The transmittance measurement for one test was calculated as the average value (average transmittance) of the transmittance measured at 2-second intervals over 180 seconds from the start of stirring. The average value of the average transmittance (n=3) obtained by repeating this three times was taken as the transmittance of 400 nm light. The transmittance was evaluated as follows. ◎: The transmittance is less than 1.0, indicating excellent dispersion of modified cellulose nanofibers. ○: The transmittance is between 1.0 and 5.0, and although some aggregation of modified cellulose nanofibers is observed, the dispersion state is good. ×: The transmittance is 5.0 or higher, and many of the modified cellulose nanofibers are in an aggregated state, indicating that the dispersibility of the modified cellulose nanofibers is not observed.

[0125] (2) Standard deviation of transmittance For each average transmittance measurement taken every 2 seconds over a 180-second period, the standard deviation was calculated. The standard deviation of transmittance was then determined from the average of the standard deviations obtained from three average transmittance measurements. The standard deviation of transmittance was evaluated as follows: ◎: Standard deviation of transmittance is less than 0.50 ○: Standard deviation of transmittance is 0.50 or greater and less than 1.0 ×: Standard deviation of transmittance is 1.0 or greater.

[0126] The evaluation results are shown in Tables 1 to 4 below.

[0127] [Table 1]

[0128] [Table 2]

[0129] [Table 3]

[0130] [Table 4]

[0131] From Tables 1 to 4 above, the modified cellulose nanofiber compositions of Examples 1 to 24, prepared by adding 10 to 2000 parts by mass of a cellulose derivative to 100 parts by mass of modified cellulose nanofibers in which a silane coupling agent was added in an amount of 0.005 to 6.0 moles per 1.0 mole of β-glucose units of cellulose nanofibers as a dispersion medium, showed excellent transmittance and standard deviation of transmittance at a wavelength of 400 nm, indicating excellent dispersibility of the modified cellulose nanofibers. In particular, the modified cellulose nanofiber compositions of the Examples in which 50 parts by mass or more of a cellulose derivative was added to 100 parts by mass of modified cellulose nanofibers tended to show further improved dispersibility of the modified cellulose nanofibers. Furthermore, the modified cellulose nanofiber compositions of the Examples using modified cellulose nanofibers in which a silane coupling agent was added in an amount of 1.0 mole per 1.0 mole of β-glucose units of cellulose nanofibers showed even better transmittance and standard deviation of transmittance at a wavelength of 400 nm, indicating further improved dispersibility of the modified cellulose nanofibers.

[0132] Furthermore, as shown in Table 4 above, in the modified cellulose nanofiber composition of the example using modified cellulose nanofibers to which 6.0 moles of silane coupling agent were added per 1.0 mole of β-glucose units of cellulose nanofibers, even in Example 25 where no cellulose derivative was added, the transmittance and standard deviation of transmittance at a wavelength of 400 nm were excellent, indicating excellent dispersibility of the modified cellulose nanofibers.

[0133] On the other hand, as shown in Tables 1 to 3 above, in Comparative Examples 1 to 3, where modified cellulose nanofibers were used with a silane coupling agent added at a rate of 3.0 moles or less per 1.0 mole of β-glucose units of the cellulose nanofiber, and no cellulose derivative was added, it was not possible to achieve both excellent light transmittance at a wavelength of 400 nm and excellent transmittance standard deviation, and thus the dispersibility of the modified cellulose nanofibers could not be obtained. [Industrial applicability]

[0134] The method for producing the modified cellulose nanofiber composition of the present invention yields a modified cellulose nanofiber composition that exhibits excellent dispersibility of modified cellulose nanofibers and can easily expand the range of applications for cellulose. Therefore, it can be used in a wide range of fields, for example, in the field of resin compositions used as materials for molded articles.

Claims

1. The process involves preparing a cellulose nanofiber dispersion by dispersing cellulose nanofibers in water, and A silane coupling agent-containing dispersion preparation step is performed by adding a silane coupling agent having an epoxy group to the cellulose nanofiber dispersion in an amount of 0.005 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber to obtain a silane coupling agent-containing dispersion. A drying step in which the silane coupling agent-containing dispersion is subjected to a drying treatment to modify the cellulose nanofiber with the silane coupling agent, A process for producing modified cellulose nanofibers in a process having the following: The dispersion medium preparation process involves preparing the dispersion medium, A cellulose derivative addition step is performed in which a cellulose derivative is added to the prepared dispersion medium to prepare a cellulose derivative-containing solution, A modified cellulose nanofiber addition step is performed by adding the modified cellulose nanofiber to the cellulose derivative-containing solution in an amount of 100 parts by mass of the modified cellulose nanofiber to 10 to 2000 parts by mass of the cellulose derivative. Includes, The silane coupling agent is defined by the following general formula (1) 【Chemistry 1】 (In general formula (1), X represents an organic functional group containing an epoxy group, and R1, R2, and R3 each independently represent a chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms.) This is a compound represented by this formula. Of the aforementioned R1, R2, and R3, at least one is an alkoxy group having 1 to 5 carbon atoms, and at least one is an alkyl group having 1 to 5 carbon atoms. The aforementioned X is given by the following general formula (2) E-R 4 -O-R 5 - (2) (In general formula (2), E represents an epoxy group, and R4 and R5 each independently represent an aliphatic hydrocarbon group having 1 to 5 carbon atoms.) This is an organic functional group represented by this formula. The cellulose derivative is at least one selected from the group consisting of hydroxyalkylcellulose and alkylcellulose. A method for producing a modified cellulose nanofiber composition, wherein the dispersion medium is selected from the group consisting of tetrahydrofuran, acetone, an alcohol having 1 to 5 carbon atoms, cyclohexanol, propylene glycol, cyclohexanone, dioxane, cellosolve, butyl cellosolve, glacial acetic acid, formic acid, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, methylene chloride, chloroform, a mixture of benzene and methanol (1:1 by volume), a mixture of toluene and ethanol (3:2 by volume), a mixture of glycerin and water (3:7 by volume), and mixtures of two or more of these.

2. The process involves preparing a cellulose nanofiber dispersion by dispersing cellulose nanofibers in water, and A silane coupling agent-containing dispersion preparation step is performed by adding a silane coupling agent having an epoxy group to the cellulose nanofiber dispersion in an amount of 0.005 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber to obtain a silane coupling agent-containing dispersion. A drying step in which the silane coupling agent-containing dispersion is subjected to a drying treatment to modify the cellulose nanofiber with the silane coupling agent, A process for producing modified cellulose nanofibers in a process having the following The dispersion medium preparation process involves preparing the dispersion medium, A modified cellulose nanofiber addition step is performed to prepare a modified cellulose nanofiber-containing dispersion medium by adding the modified cellulose nanofiber to the prepared dispersion medium, A cellulose derivative addition step is to add a cellulose derivative to the modified cellulose nanofiber-containing dispersion medium in an amount of 100 parts by mass of the modified cellulose nanofiber and 10 to 2000 parts by mass of the cellulose derivative. Includes, The silane coupling agent is defined by the following general formula (1) 【Chemistry 1】 (In general formula (1), X represents an organic functional group containing an epoxy group, and R1, R2, and R3 each independently represent a chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms.) This is a compound represented by this formula. Of the aforementioned R1, R2, and R3, at least one is an alkoxy group having 1 to 5 carbon atoms, and at least one is an alkyl group having 1 to 5 carbon atoms. The aforementioned X is given by the following general formula (2) E-R 4 -O-R 5 - (2) (In general formula (2), E represents an epoxy group, and R4 and R5 each independently represent an aliphatic hydrocarbon group having 1 to 5 carbon atoms.) This is an organic functional group represented by this formula. The cellulose derivative is at least one selected from the group consisting of hydroxyalkylcellulose and alkylcellulose. A method for producing a modified cellulose nanofiber composition, wherein the dispersion medium is selected from the group consisting of tetrahydrofuran, acetone, an alcohol having 1 to 5 carbon atoms, cyclohexanol, propylene glycol, cyclohexanone, dioxane, cellosolve, butyl cellosolve, glacial acetic acid, formic acid, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, methylene chloride, chloroform, a mixture of benzene and methanol (1:1 by volume), a mixture of toluene and ethanol (3:2 by volume), a mixture of glycerin and water (3:7 by volume), and mixtures of two or more of these.

3. The process involves preparing a cellulose nanofiber dispersion by dispersing cellulose nanofibers in water, and A silane coupling agent-containing dispersion preparation step is performed by adding a silane coupling agent having an epoxy group to the cellulose nanofiber dispersion in an amount of 0.005 moles to 6.0 moles per 1.0 mole of β-glucose units of the cellulose nanofiber to obtain a silane coupling agent-containing dispersion. A drying step in which the silane coupling agent-containing dispersion is subjected to a drying treatment to modify the cellulose nanofiber with the silane coupling agent, A process for producing modified cellulose nanofibers in a process having the following: The dispersion medium preparation process involves preparing the dispersion medium, A cellulose component addition step is to add a cellulose derivative and the modified cellulose nanofiber as cellulose components to the prepared dispersion medium in an amount range of 100 parts by mass of the modified cellulose nanofiber and 10 to 2000 parts by mass of the cellulose derivative. Includes, The silane coupling agent is defined by the following general formula (1) 【Chemistry 1】 (In general formula (1), X represents an organic functional group containing an epoxy group, and R1, R2, and R3 each independently represent a chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms.) This is a compound represented by this formula. Of the aforementioned R1, R2, and R3, at least one is an alkoxy group having 1 to 5 carbon atoms, and at least one is an alkyl group having 1 to 5 carbon atoms. The aforementioned X is given by the following general formula (2) E-R 4 -O-R 5 - (2) (In general formula (2), E represents an epoxy group, and R4 and R5 each independently represent an aliphatic hydrocarbon group having 1 to 5 carbon atoms.) This is an organic functional group represented by this formula. The cellulose derivative is at least one selected from the group consisting of hydroxyalkylcellulose and alkylcellulose. A method for producing a modified cellulose nanofiber composition, wherein the dispersion medium is selected from the group consisting of tetrahydrofuran, acetone, an alcohol having 1 to 5 carbon atoms, cyclohexanol, propylene glycol, cyclohexanone, dioxane, cellosolve, butyl cellosolve, glacial acetic acid, formic acid, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), pyridine, methylene chloride, chloroform, a mixture of benzene and methanol (1:1 by volume), a mixture of toluene and ethanol (3:2 by volume), a mixture of glycerin and water (3:7 by volume), and mixtures of two or more of these.

4. A method for producing a modified cellulose nanofiber composition according to any one of claims 1 to 3, wherein the drying treatment is a drying treatment using freeze-drying.

5. A method for producing a modified cellulose nanofiber composition according to any one of claims 1 to 4, further comprising a dialysis step of dialyzing the silane coupling agent-containing dispersion using a dialysis membrane between the silane coupling agent-containing dispersion preparation step and the drying step.

6. A method for producing a modified cellulose nanofiber composition according to any one of claims 1 to 5, wherein the silane coupling agent comprises 3-glycidoxypropyl (dimethoxy)methylsilane.

7. A method for producing a modified cellulose nanofiber composition according to any one of claims 1 to 6, wherein the cellulose derivative is hydroxyalkylcellulose.

8. A method for producing a modified cellulose nanofiber composition according to any one of claims 1 to 7, wherein the hydroxyalkyl cellulose is hydroxypropyl cellulose.

9. A method for producing a modified cellulose nanofiber composition according to any one of claims 1 to 8, wherein 0.5 parts by mass or more and 120 parts by mass or less of the cellulose derivative are added to 100 parts by mass of the dispersion medium.

10. A method for producing the modified cellulose nanofiber composition according to any one of claims 1 to 9, wherein the modified cellulose nanofiber is a dispersion of the modified cellulose nanofiber.

11. A method for producing a modified cellulose nanofiber composition according to claim 10, wherein the average value of the transmittance of light at a wavelength of 400 nm at a stirring speed of 1000 rpm of the dispersion of the modified cellulose nanofiber is less than 5.

0.

12. A method for producing a modified cellulose nanofiber composition according to claim 10 or 11, wherein the standard deviation of the transmittance of the dispersion of the modified cellulose nanofibers at a wavelength of 400 nm at a rotation speed of 1000 rpm of the stirring means is less than 1.0.

Images