Modified cellulose nanofiber composition

Abstract

To provide a modified cellulose nanofiber composition that comprises cellulose nanofiber having excellent dispersibility, capable of easily widening a range of application of cellulose, also allowing excellent hydrophobicity to be imparted to the cellulose nanofiber, resulting in excellent affinity with hydrophobic substance.SOLUTION: A modified cellulose nanofiber composition comprises: modified cellulose nanofiber in which at least some of hydroxy groups of cellulose are modified with an epoxy group-bearing silane coupling agent; a cellulose derivative; and a dispersion medium for the modified cellulose nanofiber. Per 1.0 mol of a β-glucose unit of the cellulose, 0.005 mol or more and 6.0 mol or less of the silane coupling agent is used for the modification. Relative to 100 pts.mass of the modified cellulose nanofiber, 10 pts.mass or more and 2000 pts.mass or less of the cellulose derivative is contained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a composition of modified nanocellulose modified with a silane coupling agent, and in particular to a composition of modified cellulose nanofibers that also exhibits affinity for hydrophobic substances. [Background technology]

[0002] Nanocellulose is a cellulose fiber with a thickness on the order of nanometers that is obtained by defibrating plant fibers such as pulp in an aqueous medium. Nanocellulose is classified into cellulose nanofibers, cellulose crystals, cellulose whiskers, bacterial cellulose, etc., depending on the structure of the cellulose. Because cellulose nanofibers are lightweight and strong, they have attracted attention for use as a reinforcing material for thermoplastic resins and the like (see, for example, Patent Document 1).

[0003] On the other hand, because cellulose nanofibers are hydrophilic, it is difficult to uniformly disperse them in organic solvents or mix them uniformly with hydrophobic materials such as resins, limiting the scope of their application. Therefore, for example, a technique has been proposed in the past to impart hydrophobic properties to cellulose nanofibers by reacting hydrated cellulose nanofibers with a vinyl organic acid and then recovering the product (see, for example, Patent Document 2). Hereinafter, cellulose nanofibers obtained by imparting desired properties such as hydrophobicity to naturally derived cellulose nanofibers obtained from plant fibers, etc., may be referred to as "modified cellulose nanofibers."

[0004] However, the modified cellulose nanofibers disclosed in Patent Document 2 have problems in that the reaction conditions between the cellulose nanofibers and the vinyl organic acid are strict and the production process is complicated. Furthermore, when cellulose nanofibers are modified with vinyl organic acids, the molecular structure of the cellulose nanofiber itself can change depending on the degree of modification, which not only can change the properties of the cellulose nanofiber, but there is also room for improvement in terms of improving the hydrophobicity of the cellulose nanofibers and, ultimately, improving their dispersibility in dispersion media such as organic solvents. Therefore, the modified cellulose nanofibers disclosed in Patent Document 2 require improvement in terms of obtaining a dispersion with excellent dispersibility of cellulose nanofibers, and there remains the problem that the range of application of cellulose nanofibers is still limited.

[0005] Another proposed technique for imparting hydrophobic properties to cellulose nanofibers is to attach two types of modifying groups to the surface of cellulose nanofibers: one selected for wettability (e.g., aromatic groups) and the other selected for steric repulsion and hydrophobicity (e.g., polyalkylene glycol groups). This allows for the modification of cellulose nanofibers to hydrophobicity with a small mass of modifying groups. However, modified cellulose nanofibers using two types of modifying groups (e.g., aromatic groups and polyalkylene glycol groups) have complex chemical structures, and there is a need for improvement in obtaining dispersions with excellent dispersibility of cellulose nanofibers. Furthermore, modified cellulose nanofibers using two types of modifying groups (e.g., aromatic groups and polyalkylene glycol groups) lack highly reactive functional groups, making it difficult to expand their application fields. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-11392 [Patent Document 2] International Publication No. 2016 / 010016 Summary of the Invention [Problem to be solved by the invention]

[0007] In view of the above circumstances, an object of the present invention is to provide a modified cellulose nanofiber composition that has excellent dispersibility of cellulose nanofibers, can easily expand the range of applications of cellulose, and imparts excellent hydrophobicity to the cellulose nanofibers, giving them excellent affinity with hydrophobic substances. [Means for solving the problem]

[0008] The gist of the configuration of the present invention is as follows. [1] A modified cellulose nanofiber in which at least a portion of the hydroxyl groups of cellulose are modified with a silane coupling agent having an epoxy group, a cellulose derivative, and a dispersion medium for the modified cellulose nanofiber, the modified cellulose nanofibers are modified with the silane coupling agent at a loading ratio of 0.005 mol or more and 6.0 mol or less per 1.0 mol of β-glucose unit of the cellulose, A modified cellulose nanofiber composition comprising 10 parts by mass or more and 2000 parts by mass or less of the cellulose derivative per 100 parts by mass of the modified cellulose nanofiber. [2] A modified cellulose nanofiber in which at least a portion of the hydroxyl groups of cellulose is modified with a silane coupling agent having an epoxy group, and a dispersion medium for the modified cellulose nanofiber, A modified cellulose nanofiber composition in which the modified cellulose nanofibers are modified with the silane coupling agent at a loading ratio of 5.0 mol to 6.0 mol per 1.0 mol of β-glucose unit of the cellulose. [3] The modified cellulose nanofiber composition according to [1] or [2], wherein the silane coupling agent has at least an epoxy group and an alkoxy group. [4] The modified cellulose nanofiber composition according to any one of [1] to [3], wherein the silane coupling agent has an epoxy group, an alkoxy group, and an alkyl group. [5] The silane coupling agent is represented by the following general formula (1): [ka] (In the general formula (1), X represents an organic functional group containing an epoxy group, and R 1 , R 2 , R 3 and each independently represent chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. [6] R 1 , the R 2 , the R 3 The modified cellulose nanofiber composition according to [5], wherein at least one of the groups is an alkoxy group having 1 to 5 carbon atoms and at least one of the groups is an alkyl group having 1 to 5 carbon atoms. [7] The modified cellulose nanofiber composition according to any one of [1] to [6], wherein the silane coupling agent comprises 3-glycidoxypropyl(dimethoxy)methylsilane. [8] The modified cellulose nanofiber composition according to [1], wherein the cellulose derivative comprises at least one selected from the group consisting of hydroxyalkyl cellulose and alkyl cellulose. [9] The modified cellulose nanofiber composition according to [1], wherein the cellulose derivative is hydroxyalkyl cellulose.

[10] The modified cellulose nanofiber composition according to [8] or [9], wherein the hydroxyalkyl cellulose is hydroxypropyl cellulose.

[11] The modified cellulose nanofiber composition according to [1], wherein the cellulose derivative is contained in an amount of 0.5 parts by mass or more and 120 parts by mass or less per 100 parts by mass of the dispersion medium.

[12] The modified cellulose nanofiber composition according to any one of [1] to

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

[13] A modified cellulose nanofiber composition according to

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

[14] A modified cellulose nanofiber composition according to

[12] or

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

[15] A modified cellulose nanofiber composition according to any one of [1] to

[14] , wherein the modified cellulose nanofibers have an average fiber length of 20 μm or more and 200 μm or less and an average fiber diameter of 4 nm or more and 100 nm or less.

[0009] The modified cellulose nanofibers contained in the modified cellulose nanofiber composition [1] are modified with a silane coupling agent by chemically bonding the silanol groups of the silane coupling agent to the hydroxyl groups of the cellulose. In other words, the modified cellulose nanofibers have a structure in which the silane coupling agent is chemically bonded to the hydroxyl groups of the cellulose. Note that "cellulose nanofiber" refers to cellulose fibers with an average fiber diameter of less than 1.0 μm, i.e., an average fiber diameter on the nanometer order.

[0010] Furthermore, the cellulose derivative blended in the modified cellulose nanofiber composition [1] is dissolved in the dispersion medium in the modified cellulose nanofiber composition. It is believed that the cellulose derivative being dissolved in the dispersion medium in the modified cellulose nanofiber composition causes an interaction between the hydroxyl groups of the cellulose derivative and the hydroxyl groups of the modified cellulose nanofibers in the modified cellulose nanofiber composition, resulting in the cellulose derivative being coordinated to the modified cellulose nanofibers.

[0011] The term "transmittance of a modified cellulose nanofiber dispersion at a wavelength of 400 nm when the stirring means is rotated at 1000 rpm" refers to the transmittance of light at a wavelength of 400 nm with an optical path length of 1 cm measured at the center of the height of the modified cellulose nanofiber dispersion when 2.0 ml of the modified cellulose nanofiber dispersion, prepared by adding a predetermined amount of cellulose derivative to 0.1 g of modified cellulose nanofiber in 20 ml of dispersion medium, was placed in a 4.5 ml container and stirred at 1000 rpm using a stirrer (stirring bar) with a diameter of 9 mm and a height of 6.5 mm at 25°C. The transmittance measured in one measurement was calculated as the average transmittance measured every 2 seconds over a 180-second period starting from the start of stirring. The "average transmittance" is the average of three average transmittance measurements. Furthermore, the "standard deviation of transmittance" refers to the average value of the standard deviations obtained from three measurements of average transmittance, calculated from one measurement of average transmittance, i.e., transmittance measured every two seconds for 180 seconds. [Effects of the Invention]

[0012] The modified cellulose nanofiber composition of the present invention includes modified cellulose nanofibers in which at least a portion of the hydroxyl groups of cellulose have been modified with a silane coupling agent having epoxy groups, a cellulose derivative, and a dispersion medium for the modified cellulose nanofibers. The cellulose is modified at a loading ratio of 0.005 to 6.0 moles of the silane coupling agent per 1.0 mole of β-glucose unit of the cellulose. The cellulose derivative is contained in an amount of 10 to 2,000 parts by mass per 100 parts by mass of the modified cellulose nanofibers. This provides excellent dispersibility of the cellulose nanofibers in the modified cellulose nanofiber composition, making it easy to expand the range of applications for cellulose. Furthermore, the modified cellulose nanofiber composition of the present invention imparts excellent hydrophobicity to the cellulose nanofibers, thereby providing the cellulose nanofibers in the modified cellulose nanofiber composition with excellent affinity for hydrophobic substances. Therefore, the modified cellulose nanofiber composition of the present invention allows for uniform dispersion of the cellulose nanofibers in the hydrophobic substances to which it is applied, and also ensures that the properties of the cellulose nanofibers are imparted to the intended target.

[0013] The modified cellulose nanofiber composition of the present invention comprises modified cellulose nanofibers in which at least a portion of the hydroxyl groups of the cellulose have been modified with a silane coupling agent having an epoxy group, and a dispersant for the modified cellulose nanofibers. The cellulose is modified at a loading ratio of 5.0 to 6.0 moles of the silane coupling agent per 1.0 mole of β-glucose unit of the cellulose, resulting in excellent dispersibility of the cellulose nanofibers in the modified cellulose nanofiber composition, making it easy to expand the range of applications for cellulose. Furthermore, because the cellulose nanofibers have been imparted with excellent hydrophobicity, the cellulose nanofibers in the modified cellulose nanofiber composition have excellent affinity for hydrophobic substances.

[0014] Furthermore, the modified cellulose nanofiber composition of the present invention contains highly reactive epoxy groups as functional groups, which allow the modified cellulose nanofibers to be further modified via the epoxy groups, thereby making it possible to easily expand the range of hydrophobic substances to which the modified cellulose nanofiber composition of the present invention can be applied.

[0015] According to the modified cellulose nanofiber composition of the present invention, the silane coupling agent has at least an epoxy group and an alkoxy group, which reliably modifies cellulose and reliably imparts excellent hydrophobicity to the modified cellulose nanofiber.

[0016] According to the modified cellulose nanofiber composition of the present invention, the silane coupling agent contains an epoxy group, an alkoxy group, and an alkyl group, which reliably modifies the cellulose and imparts excellent hydrophobicity, while reliably preventing the modified cellulose nanofibers from aggregating together, thereby enabling more reliably uniform dispersion in hydrophobic substances such as organic solvents and resins.

[0017] According to the modified cellulose nanofiber composition of the present invention, the silane coupling agent is a compound represented by the following general formula (1): [ka] (In the general formula (1), X represents an organic functional group containing an epoxy group, and R 1 , R 2 , R 3 and each independently represent chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. By using a compound represented by the formula (I), the hydrophobicity of the modified cellulose nanofibers is reliably improved.

[0018] According to the modified cellulose nanofiber composition of the present invention, the silane coupling agent contains 3-glycidoxypropyl(dimethoxy)methylsilane, which reliably imparts superior hydrophobicity while more reliably preventing the modified cellulose nanofibers from aggregating together.

[0019] According to the modified cellulose nanofiber composition of the present invention, the cellulose derivative contains at least one selected from the group consisting of hydroxyalkyl cellulose and alkyl cellulose, thereby ensuring excellent dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition.

[0020] According to the modified cellulose nanofiber composition of the present invention, the cellulose derivative is hydroxyalkyl cellulose, which more reliably improves the dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition.

[0021] According to the modified cellulose nanofiber composition of the present invention, the hydroxyalkyl cellulose is hydroxypropyl cellulose, which further improves the dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition. DETAILED DESCRIPTION OF THE INVENTION

[0022] First modified cellulose nanofiber composition The modified cellulose nanofiber composition of the present invention will be described below. First, the first modified cellulose nanofiber composition of the present invention will be described below.

[0023] The first modified cellulose nanofiber composition of the present invention comprises modified cellulose nanofibers in which at least a portion of the hydroxyl groups of cellulose have been modified with a silane coupling agent having epoxy groups, a cellulose derivative, and a dispersion medium for the modified cellulose nanofibers, wherein the silane coupling agent is added in an amount of 0.005 to 6.0 moles per 1.0 mole of β-glucose unit of the cellulose, and the cellulose derivative is contained in an amount of 10 to 2,000 parts by mass per 100 parts by mass of the modified cellulose nanofibers. In the first 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.

[0024] The first modified cellulose nanofiber composition of the present invention exhibits excellent dispersibility of cellulose nanofibers in the modified cellulose nanofiber composition, allowing for a wide range of applications for cellulose. Furthermore, the first modified cellulose nanofiber composition of the present invention imparts excellent hydrophobicity to the cellulose nanofibers, resulting in the cellulose nanofibers in the modified cellulose nanofiber composition having excellent affinity for hydrophobic substances. Therefore, the first modified cellulose nanofiber composition of the present invention allows for uniform dispersion of the cellulose nanofibers in the hydrophobic substance to which it is applied, and also ensures that the properties of the cellulose nanofibers are imparted to the target substance. Furthermore, the modified cellulose nanofibers contained in the modified cellulose nanofiber composition contain highly reactive epoxy groups as functional groups, allowing for further modification via the epoxy groups. Therefore, the first modified cellulose nanofiber composition of the present invention allows for a wide range of target hydrophobic substances to be applied.

[0025] <Modified cellulose nanofiber> The modified cellulose nanofibers contained in the first modified cellulose nanofiber composition of the present invention have at least some of the hydroxyl groups of the cellulose modified with a silane coupling agent having an epoxy group, i.e., the modified cellulose nanofibers are cellulose nanofibers modified with a silane coupling agent.

[0026] The cellulose that forms the skeleton of modified cellulose nanofibers is described below. The size of the cellulose in modified cellulose nanofibers is not particularly limited, as long as the cellulose nanofibers have an average fiber diameter of less than 1.0 μm. However, from the viewpoints of uniforming the cellulose modification sites with the silane coupling agent and expanding the range of applications of 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 cellulose is not particularly limited, but from the viewpoints of uniforming the cellulose modification sites with the silane coupling agent and expanding the range of applications of modified cellulose nanofibers, the average fiber length is preferably 20 μm to 200 μm, and particularly preferably 50 μm to 150 μm. The average fiber diameter and average fiber length of cellulose can be measured, for example, by scanning probe microscopy or nitrogen adsorption method for the average fiber diameter, and by electron microscope (transmission electron microscope (TEM), scanning electron microscope (SEM)) or scanning probe microscope for the average fiber length.

[0027] Examples of cellulose nanofibers include cellulose derived from natural products. Specifically, examples of cellulose nanofibers include nanofibers obtained by subjecting natural product-derived cellulose precursors, which serve as raw materials, to defibration treatment. Examples of cellulose precursors, which are raw materials for cellulose nanofibers, include plant fibers such as pulp.

[0028] Next, silane coupling agents will be described below. A silane coupling agent is a compound having a functional group and a hydrolyzable silyl group in one molecule, and upon reaction with water, the hydrolyzable silyl group becomes a silanol group. The silane coupling agent has a substituent for modifying the hydroxyl groups of the cellulose that constitutes the cellulose nanofiber. In the modified cellulose nanofibers blended in the first modified cellulose nanofiber composition of the present invention, the silane coupling agent has an epoxy group as a functional group. The silanol groups of the silane coupling agent chemically bond with the hydroxyl groups of the cellulose that constitutes the cellulose nanofiber, thereby modifying the hydroxyl groups of the cellulose. The silanol groups generated by hydrolysis of the hydrolyzable silyl groups of the silane coupling agent chemically bond to the hydroxyl groups of the cellulose, thereby modifying the cellulose with the silane coupling agent.

[0029] The silane coupling agent preferably has an alkoxy group, since this can reliably modify cellulose and impart excellent hydrophobicity to the modified cellulose nanofibers. In other words, the silane coupling agent is preferably an organosilicon compound having at least an epoxy group and an alkoxy group.

[0030] Furthermore, the silane coupling agent preferably contains an alkoxy group and an alkyl group, since it can reliably modify cellulose to impart excellent hydrophobicity while reliably preventing aggregation of the modified cellulose nanofibers. In other words, the silane coupling agent is preferably an organosilicon compound containing at least an epoxy group, an alkoxy group, and an alkyl group. Reliably preventing aggregation of the modified cellulose nanofibers allows for more uniform dispersion in hydrophobic substances such as organic solvents and resins.

[0031] Furthermore, as the silane coupling agent, for example, a silane coupling agent represented by the following general formula (1) can be used in order to reliably improve the hydrophobicity of the modified cellulose nanofibers: [ka] (In the general formula (1), X represents an organic functional group containing an epoxy group, and R 1 , R 2 , R 3 are each independently a chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. In the compound of general formula (1), R 1 , R 2 , R 3 The chemical bond between and Si forms a hydrolyzable silyl group.

[0032] R in the compound of general formula (1) 1 , R 2 , R 3 As for R in the compound of general formula (1), from the viewpoint of being able to more reliably modify the cellulose nanofibers, it is more preferable that they are each independently an alkoxy group having 1 to 3 carbon atoms or an alkyl group having 1 to 3 carbon atoms, and it is particularly preferable that they are an alkoxy group having 1 to 2 carbon atoms or an alkyl group having 1 to 2 carbon atoms. Furthermore, from the viewpoint of being able to more reliably modify the cellulose nanofibers and reliably impart excellent hydrophobicity while more reliably suppressing aggregation of the modified cellulose nanofibers, it is preferable that R 1 , R 2 , R 3 Among these, it is preferred that 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.

[0033] The chemical structure of X in the compound of general formula (1) is not particularly limited as long as it is an organic functional group containing an epoxy group. However, in order to reliably impart excellent hydrophobicity, the functional group of X- is preferably a group represented by the following general formula (2): ER 4 -OR 5 - (2) (In the general formula (2), E represents an epoxy group, R 4 , R 5 and each independently represent an aliphatic hydrocarbon group having 1 to 5 carbon atoms, preferably an aliphatic hydrocarbon group having 1 to 3 carbon atoms. An organic functional group represented by the following formula is preferred.

[0034] Specific 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 reliably impart superior hydrophobicity while more reliably inhibiting aggregation of modified cellulose nanofibers. These silane coupling agents may be used alone or in combination of two or more.

[0035] The proportion of silane coupling agent used in modified cellulose nanofibers is not particularly limited as long as it is in the range of 0.005 to 6.0 moles per 1.0 mole of β-glucose unit of cellulose, but the lower limit is preferably 0.01 mole of silane coupling agent per 1.0 mole of β-glucose unit of cellulose in order to ensure excellent hydrophobicity of the modified cellulose nanofibers, more preferably 0.05 moles, and particularly preferably 0.20 moles. On the other hand, the upper limit of the proportion of silane coupling agent used in modified cellulose nanofibers is preferably 5.0 moles per 1.0 mole of β-glucose unit of cellulose in order to prevent a loss of high strength by maintaining the crystalline structure of the cellulose nanofibers, and particularly preferably 3.0 moles per 1.0 mole of β-glucose unit of cellulose in order to more reliably maintain the crystalline structure of the cellulose nanofibers. The above-mentioned ratio of the silane coupling agent to be added means the ratio of the number of silane coupling agents per β-glucose unit, which is a structural unit of the cellulose nanofiber.

[0036] The modification of at least some of the hydroxyl groups of cellulose nanofibers with a silane coupling agent having an epoxy group can be confirmed by Fourier transform infrared spectroscopy (FT-IR). That is, by comparing the infrared absorption spectrum of untreated cellulose nanofibers that have not been modified with a silane coupling agent with the infrared absorption spectrum of modified cellulose nanofibers, it can be confirmed that at least some of the hydroxyl groups of cellulose have been modified with a silane coupling agent having an epoxy group.

[0037] Specifically, when the silane coupling agent has an alkyl group, the 1260 cm -1 , 798cm -1 , 763cm -1 In contrast, for untreated cellulose nanofibers, an absorption peak due to Si-C bonds appears in the region of 1260 cm -1 , 798cm -1 , 763cm -1 Therefore, no absorption peak appears in the region of 1260 cm in the infrared absorption spectrum. -1 , 798cm -1 , 763cm -1 By checking whether or not there is an absorption peak in this region, it can be confirmed whether or not the cellulose has been modified with a silane coupling agent.

[0038] In addition, even when the silane coupling agent does not have an alkyl group, the 900 cm -1 An absorption peak due to epoxy groups appears in the region around 900 cm in the infrared absorption spectrum of untreated cellulose nanofibers. -1 In the modified cellulose nanofibers, an absorption peak appears in the region around 900 cm -1 In the region around 900 cm, the absorption peak derived from the epoxy group and the absorption peak derived from the cellulose nanofiber overlap, resulting in a stronger peak intensity. -1By checking the intensity of the peak in the surrounding region, it is possible to confirm whether the cellulose has been modified with a silane coupling agent.

[0039] The size of the modified cellulose nanofibers incorporated in the first modified cellulose nanofiber composition of the present invention is not particularly limited, but examples include an average fiber diameter of less than 1.0 μm, corresponding to the average fiber diameter of the cellulose forming the skeleton being less than 1.0 μm. From the viewpoints of uniformity of the cellulose modification sites with the silane coupling agent and expanding the range of applications of modified cellulose nanofibers, the average fiber diameter of the modified cellulose nanofibers is preferably 4 nm or more and 100 nm or less, and particularly preferably 10 nm or more and 50 nm or less. Furthermore, from the viewpoints of uniformity of the cellulose modification sites with the silane coupling agent and expanding the range of applications of modified cellulose nanofibers, the average fiber length of the modified cellulose nanofibers is preferably 20 μm or more and 200 μm or less, and particularly preferably 50 μm or more and 150 μm or less.

[0040] The modified cellulose nanofibers incorporated in the first modified cellulose nanofiber composition of the present invention are endowed with excellent hydrophobicity and have excellent affinity with hydrophobic substances, resulting in excellent mixing and dispersibility in hydrophobic substances such as resins. Furthermore, even though the modified cellulose nanofibers incorporated in the first modified cellulose nanofiber composition of the present invention are modified, the molecular structure of the cellulose nanofibers themselves is inhibited from changing, so the original properties of the cellulose nanofibers are maintained. Therefore, the modified cellulose nanofibers incorporated in the first modified cellulose nanofiber composition of the present invention have high strength and therefore exhibit excellent functionality, for example, as a reinforcing material for hydrophobic substances.

[0041] Next, a method for producing modified cellulose nanofibers will be described below. Modified cellulose nanofibers can be produced, for example, by a cellulose preparation step of preparing an aqueous cellulose dispersion in which cellulose (cellulose nanofibers), which forms the skeleton of the modified cellulose nanofibers, is dispersed in water, a reaction solution preparation step of mixing the prepared aqueous cellulose dispersion with a silane coupling agent having an epoxy group to obtain a reaction solution, and a drying step of drying the obtained reaction solution to obtain modified cellulose nanofibers in which the hydroxyl groups of the cellulose (cellulose nanofibers) have been modified with the silane coupling agent having an epoxy group.

[0042] An example of the cellulose preparation step is a method in which a cellulose precursor derived from a natural product is defibrated to convert the cellulose precursor into nanofibers to obtain cellulose nanofibers. The method for defibrating the cellulose precursor is not particularly limited, and examples include defibration treatments using a mixer, high-speed homomixer, ultrasonic homogenizer, low-pressure homogenizer, high-pressure homogenizer, high-speed rotary mixer, grinder, freeze-pulverizer, media mill, ball mill, etc.

[0043] An example of the reaction solution preparation step is a method in which a silane coupling agent having 0.005 to 6.0 moles of epoxy groups per 1.0 mole of β-glucose unit of cellulose is added to an aqueous cellulose dispersion in which cellulose nanofibers are dispersed in water. An example of the drying step is a method in which the prepared reaction solution is subjected to a drying treatment to remove water from the reaction solution.

[0044] <Cellulose derivatives> The cellulose derivative blended in the first modified cellulose nanofiber composition of the present invention is a component different 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 in the modified cellulose nanofiber composition. For example, the cellulose derivative has hydroxyl groups, and when the cellulose derivative is dissolved in the dispersion medium in the modified cellulose nanofiber composition, the hydroxyl groups of the cellulose derivative and the hydroxyl groups of the modified cellulose nanofiber in the modified cellulose nanofiber composition interact with each other, resulting in the cellulose derivative being coordinated to the modified cellulose nanofiber. Furthermore, since both modified cellulose nanofibers and cellulose derivatives have a cellulose backbone, their molecular structures are similar. Therefore, modified cellulose nanofibers have a high affinity with cellulose derivatives, and it is believed that the cellulose derivative is likely to be coordinated to the modified cellulose nanofiber. Furthermore, when the cellulose derivative is coordinated to the modified cellulose nanofiber, the surfactant properties of the cellulose derivative are exerted, resulting in the modified cellulose nanofiber having excellent dispersibility in the modified cellulose nanofiber composition.

[0045] Furthermore, the first modified cellulose nanofiber composition of the present invention uses a cellulose derivative, which is a biocompatible material, and therefore reduces the environmental impact and is also excellent in safety.

[0046] The cellulose derivative is not particularly limited as long as it is a derivative obtained by chemically reacting at least a portion of the hydroxyl groups of cellulose with a compound other than a silane coupling agent having an epoxy group, and examples thereof include hydroxyalkyl cellulose, alkyl cellulose, carboxyalkyl cellulose, and hydroxyalkyl alkyl cellulose. These cellulose derivatives may be used alone or in combination of two or more. Of these, hydroxyalkyl cellulose and alkyl cellulose are preferred because they ensure excellent dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition, and hydroxyalkyl cellulose is particularly preferred because they further ensure improved dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition. Furthermore, as the cellulose derivative, for example, hydroxyalkyl cellulose and alkyl cellulose may be used in combination, or either may be used alone.

[0047] Examples of hydroxyalkyl cellulose include hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxybutyl cellulose, hydroxypentyl cellulose, and hydroxyhexyl cellulose. These compounds may be used alone or in combination of two or more. Of these, hydroxyethyl cellulose and hydroxypropyl cellulose are preferred, with hydroxypropyl cellulose being particularly preferred, as they further improve the dispersibility of modified cellulose nanofibers in the modified cellulose nanofiber composition.

[0048] Examples of alkyl cellulose include methyl cellulose, ethyl cellulose, propyl cellulose, butyl cellulose, pentyl cellulose, and hexyl cellulose. These compounds may be used alone or in combination of two or more. Of these, methyl cellulose and ethyl cellulose are preferred, with ethyl cellulose being particularly preferred, as they can more reliably achieve excellent dispersibility of the modified cellulose nanofibers in the modified cellulose nanofiber composition.

[0049] Examples of carboxyalkyl cellulose include carboxymethyl cellulose, carboxyethyl cellulose, carboxypropyl cellulose, carboxybutyl cellulose, carboxypentyl cellulose, carboxyhexyl cellulose, etc. These compounds may be used alone or in combination of two or more.

[0050] Hydroxyalkyl alkyl cellulose is a cellulose having a hydroxyalkyl and an alkyl. Examples of hydroxyalkyl alkyl cellulose include celluloses having a hydroxymethyl and an alkyl, such as hydroxymethyl methyl cellulose, hydroxymethyl ethyl cellulose, hydroxymethyl propyl cellulose, and hydroxymethyl butyl cellulose; celluloses having a hydroxyethyl and an alkyl, such as hydroxyethyl methyl cellulose, hydroxyethyl ethyl cellulose, hydroxyethyl propyl cellulose, and hydroxyethyl butyl cellulose; celluloses having a hydroxypropyl and an alkyl, such as hydroxypropyl methyl cellulose, hydroxypropyl ethyl cellulose, hydroxypropyl propyl cellulose, and hydroxypropyl butyl cellulose; and celluloses having a hydroxybutyl and an alkyl, such as hydroxybutyl methyl cellulose, hydroxybutyl ethyl cellulose, hydroxybutyl propyl cellulose, and hydroxybutyl butyl cellulose. These compounds may be used alone or in combination of two or more.

[0051] The amount of cellulose derivative to be blended with modified cellulose nanofiber is not particularly limited as long as it is in the range of 10 to 2000 parts by mass of cellulose derivative per 100 parts by mass of modified cellulose nanofiber, but the lower limit is preferably 30 parts by mass, more preferably 40 parts by mass, and particularly preferably 50 parts by mass per 100 parts by mass of modified cellulose nanofiber, in order to reliably obtain excellent dispersibility of the modified cellulose nanofiber in the modified cellulose nanofiber composition. On the other hand, the upper limit of the amount of cellulose derivative to be blended with 100 parts by mass of modified cellulose nanofiber is preferably 1800 parts by mass, more preferably 1600 parts by mass, and particularly preferably 1500 parts by mass, in order to reliably impart the properties of cellulose nanofiber to the target of application and to reliably obtain excellent dispersibility of the modified cellulose nanofiber.

[0052] The amount of cellulose derivative to be added to the dispersion medium described below is not particularly limited, but the lower limit is preferably 0.5 parts by mass, more preferably 2.0 parts by mass, and particularly preferably 3.0 parts by mass, per 100 parts by mass of dispersion medium, in order to ensure excellent dispersibility of the modified cellulose nanofibers.On the other hand, the upper limit of the amount of cellulose derivative to be added to the dispersion medium is preferably 120 parts by mass, more preferably 75 parts by mass, and particularly preferably 50 parts by mass, in order to ensure that the properties of the modified cellulose nanofibers are imparted to the target of application, per 100 parts by mass of dispersion medium.

[0053] <Dispersion medium> The dispersion medium disperses the modified cellulose nanofibers in the first modified cellulose nanofiber composition of the present invention and also functions as a medium in which the cellulose derivative dissolves. In the first 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. This results in a state in which the cellulose derivative is coordinated with the modified cellulose nanofibers, and the modified cellulose nanofibers have excellent dispersibility in the modified cellulose nanofiber composition.

[0054] Examples of the dispersion medium include organic solvents. Examples of the organic solvent include alcohols having 1 to 5 carbon atoms, such as tetrahydrofuran (THF), 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 and methanol (1:1 (volume ratio)), a mixture of toluene and ethanol (3:2 (volume ratio)), and a mixture of glycerin and water (3:7 (volume ratio)). Examples of the dispersion medium include water. These various dispersion media may be used alone or in combination of two or more. The dispersion liquid prepared in the dispersion medium preparation step may be a solution prepared by mixing organic solvents compatible with water in any ratio.

[0055] The amount of dispersion medium to be blended per 100 parts by mass of modified cellulose nanofibers is not particularly limited, and can be selected appropriately depending on the conditions of use of the cellulose nanofiber composition and the dispersion state of the cellulose nanofibers in the dispersion medium.

[0056] From the above, the first aspect of the modified cellulose nanofiber composition 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.

[0057] <Method for producing first modified cellulose nanofiber composition> The first modified cellulose nanofiber composition of the present invention can be produced by a modified cellulose nanofiber preparation step of preparing the modified cellulose nanofibers obtained as described above, a cellulose derivative addition step of adding a cellulose derivative to a dispersion medium, a modified cellulose nanofiber addition step of further adding the prepared modified cellulose nanofibers to the dispersion medium to which the cellulose derivative has been added, and a stirring step of stirring the dispersion medium to which the cellulose derivative and modified cellulose nanofibers have been added.

[0058] Second modified cellulose nanofiber composition Next, the second modified cellulose nanofiber composition of the present invention will be described below.

[0059] The second modified cellulose nanofiber composition of the present invention comprises modified cellulose nanofibers in which at least a portion of the hydroxyl groups of cellulose have been modified with a silane coupling agent having epoxy groups, and a dispersing medium for the modified cellulose nanofibers, and the cellulose is modified at a loading ratio of 5.0 to 6.0 moles of the silane coupling agent per 1.0 mole of β-glucose unit of the cellulose.

[0060] The second modified cellulose nanofiber composition of the present invention contains modified cellulose nanofibers that have been modified with a silane coupling agent in a ratio of 5.0 to 6.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber, and the modified cellulose nanofibers are dispersed in a dispersion medium. The second modified cellulose nanofiber composition of the present invention differs from the first modified cellulose nanofiber composition of the present invention in that it does not contain a cellulose derivative.

[0061] The second modified cellulose nanofiber composition of the present invention also exhibits excellent dispersibility of cellulose nanofibers in the modified cellulose nanofiber composition, allowing for a wide range of applications for cellulose. Furthermore, the second modified cellulose nanofiber composition of the present invention also exhibits excellent hydrophobic properties, resulting in the cellulose nanofibers in the modified cellulose nanofiber composition having excellent affinity for hydrophobic substances. Therefore, the second modified cellulose nanofiber composition of the present invention also allows for uniform dispersion of the cellulose nanofibers in the hydrophobic substances to which it is applied, and also ensures that the properties of the cellulose nanofibers are imparted to the target substances. Furthermore, the modified cellulose nanofibers contained in the second modified cellulose nanofiber composition of the present invention contain highly reactive epoxy groups as functional groups, allowing for further modification via the epoxy groups. Therefore, the second modified cellulose nanofiber composition of the present invention also allows for a wide range of target hydrophobic substances to be easily applied.

[0062] A second embodiment of the modified cellulose nanofiber composition 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.

[0063] The second modified cellulose nanofiber composition of the present invention can be produced by a modified cellulose nanofiber preparation step of preparing the modified cellulose nanofibers obtained as described above, a modified cellulose nanofiber addition step of adding the prepared modified cellulose nanofibers to a dispersion medium, and a stirring step of stirring the dispersion medium to which the modified cellulose nanofibers have been added.

[0064] Light transmittance of modified cellulose nanofiber composition Next, the light transmittance of the modified cellulose nanofiber composition of the present invention will be described.

[0065] The dispersion state of modified cellulose nanofibers in a dispersion of modified cellulose nanofibers can be evaluated by measuring the transmittance of light with a wavelength of 400 nm for the dispersion. The lower the dispersibility of the modified cellulose nanofibers in the dispersion of modified cellulose nanofibers and the more aggregated the modified cellulose nanofibers are at the bottom of the dispersion, the higher the transmittance of light with a wavelength of 400 nm measured at the center in the height direction of the dispersion of the modified cellulose nanofibers. On the other hand, the higher the dispersibility of the modified cellulose nanofibers in the dispersion of modified cellulose nanofibers and the reduced state of aggregation of the modified cellulose nanofibers, i.e., the more uniformly dispersed the modified cellulose nanofibers are, the lower the transmittance of light with a wavelength of 400 nm measured at the center in the height direction of the dispersion of the modified cellulose nanofibers.

[0066] The average transmittance of light with a wavelength of 400 nm through 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, in order to ensure excellent dispersibility of the modified cellulose nanofibers, and particularly preferably less than 1.0, in order to further improve the dispersibility of the modified cellulose nanofibers. The lower limit of the average light transmittance is, for example, 0.02.

[0067] The dispersion state of modified cellulose nanofibers in a dispersion of modified cellulose nanofibers can be evaluated by measuring the standard deviation of the transmittance of light with a wavelength of 400 nm at a stirring speed of 1,000 rpm. The lower the dispersibility of the modified cellulose nanofibers in the dispersion of modified cellulose nanofibers 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 therefore the higher the standard deviation of the transmittance. On the other hand, the less the aggregated state of the modified cellulose nanofibers in the dispersion of 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 therefore the lower the standard deviation of the transmittance.

[0068] The standard deviation of the transmittance of light with a wavelength of 400 nm through the dispersion of modified cellulose nanofibers at a rotation speed of the stirring means of 1000 rpm is preferably less than 1.0, more preferably less than 0.80, in order to ensure excellent dispersibility of the modified cellulose nanofibers, and is even more preferably less than 0.60, particularly preferably less than 0.50, in order to further improve the dispersibility of the modified cellulose nanofibers.

[0069] Modified cellulose nanofiber film molded products After forming the modified cellulose nanofiber composition of the present invention into a predetermined shape, the dispersion medium can be removed from the modified cellulose nanofiber composition by drying or the like to obtain a modified cellulose nanofiber molded article of the predetermined shape. In the modified cellulose nanofiber composition of the present invention, the aggregation state of the modified cellulose nanofibers is reduced and the modified cellulose nanofibers are uniformly dispersed. Therefore, the modified cellulose nanofiber molded article obtained by removing the dispersion medium from the modified cellulose nanofiber composition of the present invention has a uniform distribution of the modified cellulose nanofibers and a smooth surface. Furthermore, the modified cellulose nanofiber composition of the present invention has not only excellent dispersibility of the modified cellulose nanofibers but also appropriate fluidity, making it easy to obtain a film-like molded article. [Example]

[0070] Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as they do not depart from the spirit of the present invention.

[0071] <Preparation of modified cellulose nanofiber composition> Example 1 A cellulose nanofiber dispersion was prepared by dispersing 1.0 g of cellulose nanofiber in water (average fiber length 100 μm, average fiber diameter 30–40 nm, Mori Machinery Corporation's "CellFim C-100 (water content approximately 95% by mass)") in 300 g of water. While stirring the prepared cellulose nanofiber dispersion with a stirrer at a stirring speed of 1350 rpm and room temperature, 3-glycidoxypropyl(dimethoxy)methylsilane (hereinafter sometimes referred to as "GOPDMS"; equivalent to a silane coupling agent with an epoxy group) was added at a ratio of 0.005 mol per 1.0 mol of β-glucose units of the cellulose nanofiber. The mixture was stirred for a predetermined period of time to prepare a reaction solution containing the cellulose nanofibers and silane coupling agent. The resulting reaction solution was dialyzed against pure water using a dialysis membrane. Dialysis using the dialysis membrane was carried out for 24 hours. The period from the addition of GOPDMS to the end of dialysis using the dialysis membrane was maintained at room temperature at 25°C. The dialyzed reaction solution was dried in a freeze dryer under conditions of a predetermined freezing temperature, reduced pressure (vacuum degree) of 10 Pa, and freeze-drying time of 72 hours to sublimate the water in the frozen reaction solution (drying step). In this way, modified cellulose nanofibers used in Example 1, in which cellulose nanofibers were modified with GOPDMS, were prepared.

[0072] The modified cellulose nanofibers were analyzed by FT-IR (PerkinElmer Co., Ltd., "Spectrum One (A)") to confirm that the cellulose nanofibers were modified with GOPDMS. The infrared absorption spectrum of the modified cellulose nanofibers was analyzed by FT-IR (PerkinElmer Co., Ltd., "Spectrum One (A)") at 1260 cm. -1 , 798cm -1 , 763cm -1 The absorption peak due to the Si-C bond appears in the region of 900 cm in the infrared absorption spectrum compared to the cellulose nanofiber before modification with GOPDMS. -1 This was confirmed by the strong peak intensity in the surrounding area.

[0073] 0.01 g of hydroxypropyl cellulose (cellulose derivative) was added to 20 ml of tetrahydrofuran (dispersion medium) and stirred. After confirming that the hydroxypropyl cellulose had dissolved in the tetrahydrofuran, 0.1 g of the modified cellulose nanofibers prepared as described above (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:0.1) was added to the solution containing the dissolved hydroxypropyl cellulose and stirred for 24 hours to prepare the modified cellulose nanofiber composition of Example 1, which is a dispersion of modified cellulose nanofibers.

[0074] Example 2 The modified cellulose nanofiber composition of Example 2 was prepared in the same manner as Example 1, except that 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:0.5) was added to a solution of 0.05 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium).

[0075] Example 3 The modified cellulose nanofiber composition of Example 3 was prepared in the same manner as Example 1, except that 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:1) was added to a solution of 0.1 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium).

[0076] 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 nanofibers (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:5) was added to a solution of 0.5 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium).

[0077] 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 nanofibers (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:10) was added to a solution of 1.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium).

[0078] 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 nanofibers (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:20) was added to a solution of 2.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium).

[0079] 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 loading ratio of 1.0 mol per 1.0 mol of β-glucose unit of the cellulose nanofiber.

[0080] Example 8 GOPDMS was added at a loading ratio of 1.0 mol per 1.0 mol of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:0.5) was added to a solution containing 0.05 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 8 was prepared in the same manner as in Example 1, except for the above.

[0081] Example 9 GOPDMS was added at a loading ratio of 1.0 mol per 1.0 mol of β-glucose units of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:1) was added to a solution containing 0.1 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 9 was prepared in the same manner as in Example 1, except for the above.

[0082] Example 10 GOPDMS was added at a loading ratio of 1.0 mol per 1.0 mol of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:5) was added to a solution of 0.5 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 10 was prepared in the same manner as in Example 1, except for the above.

[0083] Example 11 GOPDMS was added at a loading ratio of 1.0 mol per 1.0 mol of β-glucose units of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:10) was added to a solution of 1.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 11 was prepared in the same manner as in Example 1, except for the above.

[0084] Example 12 GOPDMS was added at a loading ratio of 1.0 mol per 1.0 mol of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:20) was added to a solution of 2.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 12 was prepared in the same manner as in Example 1, except for the above.

[0085] Example 13 GOPDMS was added at a ratio of 3.0 mol per 1.0 mol of β-glucose unit of the cellulose nanofiber. The modified cellulose nanofiber composition of Example 13 was prepared in the same manner as in Example 1, except for the above.

[0086] Example 14 GOPDMS was added at a loading ratio of 3.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:0.5) was added to a solution containing 0.05 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 14 was prepared in the same manner as in Example 1, except for the above.

[0087] Example 15 GOPDMS was added at a loading ratio of 3.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:1) was added to a solution containing 0.1 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 15 was prepared in the same manner as in Example 1, except for the above.

[0088] Example 16 GOPDMS was added at a loading ratio of 3.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (modified cellulose nanofiber:hydroxypropyl cellulose mass ratio = 1:5) was added to a solution containing 0.5 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 16 was prepared in the same manner as in Example 1, except for the above.

[0089] Example 17 GOPDMS was added at a loading ratio of 3.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:10) was added to a solution of 1.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 17 was prepared in the same manner as in Example 1, except for the above.

[0090] Example 18 GOPDMS was added at a loading ratio of 3.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:20) was added to a solution of 2.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 18 was prepared in the same manner as in Example 1, except for the above.

[0091] Example 19 GOPDMS was added at a ratio of 6.0 mol per 1.0 mol of β-glucose unit of the cellulose nanofiber. The modified cellulose nanofiber composition of Example 19 was prepared in the same manner as in Example 1, except for the above.

[0092] Example 20 GOPDMS was added at a loading ratio of 6.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:0.5) was added to a solution containing 0.05 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 20 was prepared in the same manner as in Example 1, except for the above.

[0093] Example 21 GOPDMS was added at a loading ratio of 6.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:1) was added to a solution containing 0.1 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 21 was prepared in the same manner as in Example 1, except for the above.

[0094] Example 22 GOPDMS was added at a loading ratio of 6.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofibers (mass ratio of modified cellulose nanofibers:hydroxypropyl cellulose = 1:5) was added to a solution of 0.5 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 22 was prepared in the same manner as in Example 1, except for the above.

[0095] Example 23 GOPDMS was added at a loading ratio of 6.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:10) was added to a solution of 1.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 23 was prepared in the same manner as in Example 1, except for the above.

[0096] Example 24 GOPDMS was added at a loading ratio of 6.0 moles per 1.0 mole of β-glucose unit of the cellulose nanofiber. 0.1 g of modified cellulose nanofiber (mass ratio of modified cellulose nanofiber:hydroxypropyl cellulose = 1:20) was added to a solution of 2.0 g of hydroxypropyl cellulose (cellulose derivative) in 20 ml of tetrahydrofuran (dispersion medium). The modified cellulose nanofiber composition of Example 24 was prepared in the same manner as in Example 1, except for the above.

[0097] 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 nanofibers was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0098] 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 nanofibers was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0099] Comparative Example 2 The modified cellulose nanofiber composition of Comparative Example 2 was prepared in the same manner as in Example 7, except that 0.1 g of modified cellulose nanofibers was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0100] Comparative Example 3 The modified cellulose nanofiber composition of Comparative Example 3 was prepared in the same manner as in Example 13, except that 0.1 g of modified cellulose nanofibers was added to 20 ml of tetrahydrofuran (dispersion medium) without adding hydroxypropyl cellulose (cellulose derivative).

[0101] <Evaluation items> (1) Transmittance of light with a wavelength of 400 nm For the modified cellulose nanofiber compositions of Examples 1 to 25 and Comparative Examples 1 to 3, 2.0 ml each was placed in a 4.5 ml container and stirred at 25°C using a stirrer with a diameter of 9 mm and a height of 6.5 mm at 1,000 rpm. During stirring, the center of the height direction of the modified cellulose nanofiber composition was irradiated with light of 400 nm wavelength over an optical path length of 1 cm. The transmittance of light of 400 nm wavelength was measured from the radiant intensity of the incident light (I0) and the radiant intensity of light transmitted through the cellulose nanofiber composition (I). The measured value of one transmittance was calculated as the average value (average transmittance) of the transmittance measured every 2 seconds over a 180-second period from the start of stirring. This was repeated three times, and the average value of the average transmittances (n = 3) obtained was used as the transmittance of light of 400 nm wavelength. The transmittance was evaluated as follows: ◎: The transmittance is less than 1.0, and the dispersion state of the modified cellulose nanofibers is very excellent. ○: The transmittance is 1.0 or more and less than 5.0, and although some aggregation of the modified cellulose nanofibers is observed, the dispersion is good. ×: The transmittance is 5.0 or more, most of the modified cellulose nanofibers are in an aggregated state, and the dispersibility of the modified cellulose nanofibers is not observed.

[0102] (2) Standard deviation of transmittance The standard deviation was calculated for each average transmittance measurement taken every two seconds for 180 seconds, and the standard deviation of the transmittance was calculated from the average of the standard deviations obtained from the three average transmittance measurements. The standard deviation of the transmittance was evaluated as follows: ◎: Standard deviation of transmittance is less than 0.50 ○: Standard deviation of transmittance is 0.50 or more and less than 1.0 ×: Standard deviation of transmittance is 1.0 or more

[0103] The evaluation results are shown in Tables 1 to 4 below.

[0104] [Table 1]

[0105] [Table 2]

[0106] [Table 3]

[0107] [Table 4]

[0108] Tables 1 to 4 above show that the modified cellulose nanofiber compositions of Examples 1 to 24, which comprise modified cellulose nanofibers modified with a silane coupling agent in a ratio of 0.005 to 6.0 moles per 1.0 mole of β-glucose units of cellulose, a cellulose derivative, and a cellulose nanofiber dispersion medium, and in which the cellulose derivative was present in an amount of 10 to 2,000 parts by mass per 100 parts by mass of modified cellulose nanofibers, exhibited excellent transmittance and standard deviation of transmittance at a wavelength of 400 nm, demonstrating excellent dispersibility of the modified cellulose nanofibers. In particular, the examples containing 50 parts by mass or more of the cellulose derivative per 100 parts by mass of modified cellulose nanofibers tended to further improve the dispersibility of the modified cellulose nanofibers. Furthermore, the modified cellulose nanofiber compositions of the examples containing modified cellulose nanofibers modified with 1.0 mole of silane coupling agent per 1.0 mole of β-glucose units of cellulose exhibited even better transmittance and standard deviation of transmittance at a wavelength of 400 nm, demonstrating even improved dispersibility of the modified cellulose nanofibers.

[0109] Furthermore, as can be seen from Table 4 above, the modified cellulose nanofiber compositions of the examples, which contained modified cellulose nanofibers modified at a loading ratio of 6.0 moles of silane coupling agent per 1.0 mole of β-glucose unit of cellulose, even Example 25, which did not contain a cellulose derivative, had excellent transmittance and standard deviation of transmittance for light with a wavelength of 400 nm, and excellent dispersibility of the modified cellulose nanofibers.

[0110] On the other hand, as can be seen from Tables 1 to 3 above, the cellulose nanofiber compositions of Comparative Examples 1 to 3, which contained modified cellulose nanofibers modified at a loading ratio of 3.0 moles or less of silane coupling agent per 1.0 mole of β-glucose unit of cellulose and did not contain any cellulose derivative, were unable to achieve both excellent transmittance at a wavelength of 400 nm and excellent standard deviation of transmittance, and were unable to obtain dispersibility of the modified cellulose nanofibers. [Industrial Applicability]

[0111] The modified cellulose nanofiber composition of the present invention has excellent dispersibility of cellulose nanofibers and can easily expand the range of applications for cellulose, making it usable in a wide range of fields, including, for example, the field of resin compositions used as materials for molded products.

Claims

1. The present invention comprises a modified cellulose nanofiber in which at least a portion of the hydroxyl groups of cellulose are modified with a silane coupling agent having an epoxy group, a cellulose derivative, and a dispersion medium for the modified cellulose nanofiber, the modified cellulose nanofibers are modified with the silane coupling agent at a loading ratio of 0.005 mol or more and 6.0 mol or less per 1.0 mol of β-glucose unit of the cellulose, The cellulose derivative is contained in an amount of 10 parts by mass or more and 2000 parts by mass or less relative to 100 parts by mass of the modified cellulose nanofibers, A modified cellulose nanofiber composition, wherein the cellulose derivative comprises at least one selected from the group consisting of hydroxyalkyl cellulose, carboxyalkyl cellulose, and hydroxyalkyl alkyl cellulose.

2. The present invention comprises a modified cellulose nanofiber in which at least a portion of the hydroxyl groups of cellulose are modified with a silane coupling agent having an epoxy group, and a dispersion medium for the modified cellulose nanofiber, A modified cellulose nanofiber composition in which the modified cellulose nanofibers are modified with the silane coupling agent at a loading ratio of 5.0 mol to 6.0 mol per 1.0 mol of β-glucose unit of the cellulose.

3. The modified cellulose nanofiber composition according to claim 1 or 2, wherein the silane coupling agent has at least an epoxy group and an alkoxy group.

4. The modified cellulose nanofiber composition according to claim 1 , wherein the silane coupling agent has an epoxy group, an alkoxy group, and an alkyl group.

5. The silane coupling agent is represented by the following general formula (1): 【Chemistry 1】 (In the general formula (1), X represents an organic functional group containing an epoxy group, and R １ , R ２ , R ３ and each independently represent chloride, an alkoxy group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms.

6. The R １ , the R ２ , the R ３ The modified cellulose nanofiber composition according to claim 5, wherein at least one of the groups is an alkoxy group having 1 to 5 carbon atoms and at least one of the groups is an alkyl group having 1 to 5 carbon atoms.

7. The modified cellulose nanofiber composition according to any one of claims 1 to 6, wherein the silane coupling agent comprises 3-glycidoxypropyl(dimethoxy)methylsilane.

8. The modified cellulose nanofiber composition according to claim 1, wherein the cellulose derivative comprises at least one selected from hydroxyalkyl celluloses.

9. The modified cellulose nanofiber composition according to claim 1, wherein the cellulose derivative is a hydroxyalkyl cellulose.

10. The modified cellulose nanofiber composition according to claim 8 or 9, wherein the hydroxyalkyl cellulose is hydroxypropyl cellulose.

11. The modified cellulose nanofiber composition according to claim 1, comprising 0.5 parts by mass or more and 120 parts by mass or less of the cellulose derivative per 100 parts by mass of the dispersion medium.

12. The modified cellulose nanofiber composition according to any one of claims 1 to 11, which is a dispersion of the modified cellulose nanofibers.

13. The modified cellulose nanofiber composition according to claim 12, wherein the average transmittance of the dispersion of the modified cellulose nanofibers at a wavelength of 400 nm when the stirring means is rotated at a speed of 1000 rpm is less than 5.

0.

14. The modified cellulose nanofiber composition according to claim 12 or 13, wherein the standard deviation of the transmittance of the dispersion of the modified cellulose nanofibers at a wavelength of 400 nm when the rotation speed of the stirring means is 1000 rpm is less than 1.

0.

15. The modified cellulose nanofiber composition according to any one of claims 1 to 14, wherein the modified cellulose nanofibers have an average fiber length of 20 µm or more and 200 µm or less and an average fiber diameter of 4 nm or more and 100 nm or less.

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