Method for manufacturing fiber-reinforced cellulose resin

Abstract

Provided is a production method for producing, in a simple manner, a fiber-reinforced cellulose-based resin in which cellulose nanofibers are highly dispersed in a cellulose-based resin. One aspect of the present disclosure relates to a method for producing a fiber-reinforced cellulose resin, the method including: a step for synthesizing a cellulose derivative in an organic solvent and obtaining a reaction liquid containing the cellulose derivative; and a step for mixing a first dispersion liquid, in which cellulose nanofibers are dispersed in a poor solvent for the cellulose derivative, with the reaction liquid and precipitating the cellulose derivative.

Description

[Technical Field]

[0001] This invention relates to a method for producing a fiber-reinforced cellulose resin in which cellulose nanofibers are dispersed in a cellulose derivative. [Background technology]

[0002] Bioplastics made from plant-based materials can contribute to measures against petroleum depletion and global warming, and are therefore being used not only in general products such as packaging, containers, and textiles, but also in durable products such as electronic devices and automobiles.

[0003] However, conventional bioplastics are made from edible components such as starch, and concerns about future food shortages have led to a demand for the development of new bioplastics made from non-edible plant components.

[0004] A typical example of a non-edible plant component is cellulose, the main component of wood and plants. Bioplastics utilizing this cellulose have been developed and some products have been commercialized.

[0005] Cellulose can be obtained by removing lignin and hemicellulose contained in wood, etc., using chemicals. Alternatively, cotton can be used as is, as it is almost entirely composed of cellulose. Cellulose is a polymer formed by the polymerization of β-1,4 glucose, but it is not thermoplastic because it has strong intermolecular forces due to hydrogen bonds derived from hydroxyl groups. In addition, it has low solvent solubility except for special solvents. Furthermore, because it has many hydrophilic hydroxyl groups, it has high water absorption and low water resistance.

[0006] For this reason, cellulose derivatives are known in which the intermolecular forces of cellulose are reduced by substituting the hydrogen atoms of the hydroxyl groups of cellulose with short-chain acyl groups such as acetyl groups, and further thermoplasticity is imparted by adding plasticizers. Furthermore, in cases where thermoplasticity and water resistance are insufficient with short-chain organic groups such as acetyl groups alone, long-chain organic groups with more carbon atoms are sometimes introduced into cellulose in addition to the short-chain organic groups. The introduced long-chain organic groups function as hydrophobic internal plasticizers, improving the thermoplasticity and water resistance of the cellulose derivative (Patent Document 1).

[0007] To impart strength to such cellulose derivatives, fiber-reinforced cellulose resins with added cellulose nanofibers as a reinforcing material are being investigated. In the production of fiber-reinforced cellulose resins, one method for mixing cellulose derivatives and cellulose nanofibers is to dry-mix them by melting and kneading. Another method involves separately preparing a solution in which the cellulose derivative is dissolved in a solvent and a dispersion in which cellulose nanofibers are dispersed in a solvent, and then mixing the two (for example, Patent Document 2). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2018 / 221663 [Patent Document 2] Japanese Patent Publication No. 2008-209595 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] However, in the method of melt-kneading a cellulose derivative and cellulose nanofibers in a dry process, the cellulose nanofibers tend to aggregate and there is a problem with dispersibility. Further, although the production method described in Patent Document 2 improves the dispersibility of cellulose nanofibers compared to the dry process, there has been a demand for the development of a method that can more easily disperse cellulose nanofibers at a high concentration in a cellulose derivative.

[0010] An object of the invention of the present disclosure is to provide a method for easily producing a fiber-reinforced cellulose-based resin in which cellulose nanofibers are highly dispersed.

Means for Solving the Problems

[0011] One aspect of the present disclosure is a step of synthesizing a cellulose derivative in an organic solvent to obtain a reaction solution containing the cellulose derivative, and a step of mixing a first dispersion liquid in which cellulose nanofibers are dispersed in a poor solvent for the cellulose derivative and the reaction solution to precipitate the cellulose derivative, and relates to a method for producing a fiber-reinforced cellulose-based resin including

[0012] Another aspect of the present disclosure is a step of synthesizing a cellulose derivative in an organic solvent to obtain a reaction solution containing the cellulose derivative, and a step of dispersing cellulose nanofibers in the reaction solution to prepare a second dispersion liquid, a step of mixing a poor solvent for the cellulose derivative and the second dispersion liquid to precipitate the cellulose derivative, and relates to a method for producing a fiber-reinforced cellulose-based resin including

Effects of the Invention

[0013] According to the present disclosure, it is possible to provide a method for producing a fiber-reinforced cellulose-based resin in which cellulose nanofibers can be highly dispersed in a cellulose-based resin by a simple method.

Modes for Carrying Out the Invention

[0014] One embodiment of a method for producing a fiber-reinforced cellulose resin according to the present disclosure is: The process involves synthesizing a cellulose derivative in an organic solvent and obtaining a reaction solution containing the cellulose derivative (cellulose derivative synthesis step), A first dispersion in which cellulose nanofibers are dispersed in a poor solvent for the cellulose derivative is mixed with the reaction solution to precipitate the cellulose derivative (precipitation step), Includes.

[0015] Another embodiment of the method for producing fiber-reinforced cellulose resins in this disclosure is: The process involves synthesizing a cellulose derivative in an organic solvent and obtaining a reaction solution containing the cellulose derivative (cellulose derivative synthesis step), A step of dispersing cellulose nanofibers in the reaction solution to prepare a second dispersion, A step of mixing the poor solvent for the cellulose derivative with the second dispersion to precipitate the cellulose derivative (precipitation step), Includes.

[0016] In the production of cellulosic resins, the process typically includes a step of precipitating the cellulose derivative by adding a poor solvent for the cellulose derivative to the reaction solution after producing a cellulose derivative from cellulose or the like (precipitation step). For example, in the production of acylated cellulose, the hydroxyl groups of cellulose are typically acylated, and then the acylated cellulose is precipitated by adding a poor solvent for the acylated cellulose to the reaction solution. In the embodiments of this disclosure, by using a dispersion of cellulose nanofibers (a dispersion in which cellulose nanofibers are dispersed in a poor solvent for acylated cellulose) in this precipitation step, a cellulosic resin with highly dispersed cellulose nanofibers can be recovered. Furthermore, in the production process of the fiber-reinforced cellulosic resin of this embodiment, the formation of a composite of the cellulose derivative and cellulose nanofibers and the precipitation of the cellulose derivative are performed simultaneously, so a fiber-reinforced cellulosic resin can be easily obtained with fewer production steps compared to production methods that perform these steps separately.

[0017] The following describes each step.

[0018] <Cellulose derivative synthesis process> In the cellulose derivative synthesis step, a cellulose derivative is synthesized in an organic solvent to obtain a reaction solution containing the cellulose derivative. The "reaction solution" obtained in the cellulose derivative synthesis step refers to the reaction solution obtained by synthesizing a cellulose derivative from cellulose or the like in an organic solvent, before the generated cellulose derivative is precipitated. The reaction solution contains an organic solvent and a cellulose derivative, and preferably the cellulose derivative is dissolved in the organic solvent. The organic solvent is preferably a good solvent for the target cellulose derivative. In this specification, a good solvent refers to a solvent in which the solubility of the solute (cellulose derivative) at 25°C is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.

[0019] The organic solvent should preferably be selected from among good solvents for the target cellulose derivative, such as acetic acid, dioxane, pyridine, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide. Nitrogen-containing basic solvents such as pyridine, N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide are particularly preferred.

[0020] In one embodiment of the cellulose derivative synthesis process, it is preferable to use cellulose as a raw material and carry out a reaction to substitute the hydroxyl groups of cellulose to synthesize acylated cellulose or alkylcellulose, etc. In another embodiment, a compound in which some of the hydroxyl groups of cellulose have already been substituted (first cellulose derivative) may be used as a raw material, and a substituent may be introduced to the hydroxyl groups of the first cellulose derivative to synthesize a second cellulose derivative. For example, cellulose acetate may be used as a raw material and reacted (acylated) to synthesize cellulose propionate acetate.

[0021] The following describes cellulose and cellulose derivatives (cellulose-based resins).

[0022] (cellulose) Cellulose is a linear polymer formed by the polymerization of β-D-glucose molecules (β-D-glucopyranose) represented by the following formula (A) via β(1→4) glycosidic bonds. Each glucose unit constituting cellulose has three hydroxyl groups (where n is a natural number). In embodiments of this disclosure, short-chain organic groups and / or long-chain organic groups can be introduced into such cellulose using these hydroxyl groups.

[0023] [ka]

[0024] Cellulose is the main component of plants and is obtained by separating other components such as lignin from plants. In addition to the cellulose obtained in this way, cotton (e.g., cotton linters) or pulp (e.g., wood pulp) with a high cellulose content can be used, either by refining them or as is. Regarding the shape, size, and form of the cellulose or its derivative used as a raw material, it is preferable to use a powder form with an appropriate particle size and shape from the viewpoint of reactivity, solid-liquid separation, and handling. For example, fibrous or powdered materials with a diameter of 1 to 100 μm (preferably 10 to 50 μm) and a length of 10 μm to 100 mm (preferably 100 μm to 10 mm) can be used.

[0025] The degree of polymerization of cellulose is preferably in the range of 300 to 700 as the glucose degree of polymerization (average degree of polymerization), more preferably 350 to 650, and even more preferably 400 to 600. If the degree of polymerization is too low, the impact resistance of the manufactured resin may not be sufficient. Conversely, if the degree of polymerization is too high, the fluidity of the manufactured resin may become too low, which may hinder molding.

[0026] Cellulose may be mixed with similar structures, such as chitin, chitosan, hemicellulose, xylan, glucomannan, curdlan, etc. If mixed, the amount is preferably 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and may even be 0% by mass.

[0027] Although the above description applies to cellulose, the present invention is also applicable to its analogues, namely, ordinary non-edible polysaccharides such as chitin, chitosan, hemicellulose, xylan, glucomannan, and curdlan.

[0028] (Cellulose derivatives (cellulose-based resins)) Cellulose derivatives (also referred to as "cellulose-based resins") are obtained by substituting the hydroxyl groups of the above-mentioned cellulose, and are not limited to, but include, for example, acylated cellulose and alkylcellulose, and in one embodiment, acylated cellulose is preferred.

[0029] While acylated cellulose is described as one preferred embodiment of a cellulose derivative, this disclosure is not limited thereto.

[0030] The acylated cellulose is not particularly limited, as long as the hydroxyl groups of the cellulose described above are acylated. The manufacturing method of this embodiment can be applied to any acylated cellulose obtained by acylating the hydroxyl groups of cellulose in an organic solvent, and then mixing the reaction solution with a poor solvent for the acylated cellulose to precipitate it.

[0031] In one embodiment, the acylated cellulose may be known acetylcellulose. In a typical method for producing acetylcellulose, pulp containing cellulose (preferably pre-treated pulp obtained by dissociating and crushing pulp raw material and then spraying and mixing it with acetic acid) is reacted with a mixed acid containing acetic anhydride as an acetic acid agent, acetic acid as a solvent, and sulfuric acid as a catalyst. Subsequently, the acetylcellulose is hydrolyzed to obtain acetylcellulose of the desired degree of acetic acidity. After that, the acetylcellulose can be precipitated and recovered by adding water or the like, which is a poor solvent for acetylcellulose.

[0032] In another embodiment, acylated cellulose is preferably a cellulose derivative (acylated cellulose) in which the hydrogen atoms of the hydroxyl groups of cellulose are replaced by a long-chain component which is a linear saturated aliphatic acyl group having 4 or more carbon atoms, preferably 8 or more, more preferably 12 or more, and even more preferably 14 or more carbon atoms, and / or a short-chain component which is an acyl group having 3 or fewer carbon atoms (acetyl group and / or propionyl group). The long-chain component and the short-chain component will be described below.

[0033] (Long-chain component) The acylated cellulose obtained by the manufacturing method of this disclosure may have a long-chain component, which is a linear saturated aliphatic acyl group having 4 or more carbon atoms, preferably 8 or more, more preferably 12 or more, and even more preferably 14 or more carbon atoms, introduced using the hydroxyl groups of cellulose. In one embodiment, it is preferable that a long-chain component is introduced in addition to a short-chain component, which is an acyl group having 3 or fewer carbon atoms.

[0034] Such long-chain components can be introduced by reacting hydroxyl groups in cellulose with a long-chain reagent. These long-chain components correspond to acyl groups introduced in place of hydrogen atoms in the hydroxyl groups of cellulose. The long-chain organic groups of the long-chain components and the pyranose rings of cellulose can be bonded via ester bonds. The introduced acyl groups are linear saturated aliphatic acyl groups having 4 or more carbon atoms, preferably 8 or more, more preferably 12 or more, and even more preferably 14 or more. In one embodiment, the introduced acyl groups include linear saturated aliphatic acyl groups having 4 or more carbon atoms, with linear saturated aliphatic acyl groups having 12 to 30 carbon atoms being preferred, and linear saturated aliphatic acyl groups having 12 to 22 carbon atoms being more preferred. As for the acyl group, for example, groups obtained by removing the OH from the carboxyl group of myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid (tetradecanoyl group, hexadecanoyl group, octadecanoyl group, eicosanoyl group, docosanoyl group) are preferred.

[0035] The long-chain reagent is a compound having at least one functional group that can react with the hydroxyl groups in cellulose. For example, compounds having a carboxyl group, a carboxylic acid halide group, or a carboxylic acid anhydride group can be used.

[0036] For example, long-chain carboxylic acids having 4 or more carbon atoms, preferably 8 or more, more preferably 12 or more, and even more preferably 14 or more, and acid halides or acid anhydrides of the long-chain carboxylic acids can be used as long-chain reagents. It is desirable that the saturation of these carboxylic acids or carboxylic acid derivatives be as high as possible, and linear saturated fatty acids, their acid halides or anhydrides are preferred. Specific examples of long-chain carboxylic acids include linear saturated fatty acids such as myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, and melisic acid, with myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid being preferred. Furthermore, from the viewpoint of environmental compatibility, it is preferable that the long-chain carboxylic acids are carboxylic acids obtained from natural products.

[0037] The long-chain component preferably has 4 or more carbon atoms, more preferably 8 or more, even more preferably 12 or more, even more preferably 14 or more, and particularly preferably 16 or more. From the viewpoint of reaction efficiency when introducing the long-chain component, it is preferable that it has 48 or fewer carbon atoms, more preferably 36 or fewer, and particularly preferably 24 or fewer. This long-chain component may be a single type or may contain two or more types.

[0038] By introducing the aforementioned long-chain components into cellulose or its derivatives, its properties can be modified, for example, improving water resistance, thermoplasticity, and mechanical properties.

[0039] (Short-chain component) The acylated cellulose obtained by the manufacturing method of this embodiment may have short-chain components introduced in addition to long-chain components by utilizing the hydroxyl groups of cellulose, or it may have only short-chain components introduced. Examples of short-chain components include acetyl groups and propionyl groups, and in one embodiment, propionyl groups are preferred.

[0040] Such short-chain components can be introduced by the reaction of hydroxyl groups in cellulose with short-chain reagents. These short-chain components correspond to the acyl group portion introduced in place of the hydrogen atoms in the hydroxyl groups of cellulose. Furthermore, the short-chain organic group (methyl group or ethyl group) of the short-chain component and the pyranose ring of cellulose can be bonded via ester bonds.

[0041] This short-chain reagent is a compound having at least one functional group that can react with hydroxyl groups in cellulose, such as compounds having a carboxyl group, a carboxylic acid halide group, or a carboxylic acid anhydride group. Specifically, examples include aliphatic monocarboxylic acids, their acid halides, and their acid anhydrides.

[0042] This short-chain component more preferably has 2 to 3 carbon atoms, and more preferably the hydrogen atoms of the hydroxyl group of cellulose are replaced by acyl groups (acetyl group, propionyl group) with 2 or 3 carbon atoms. By introducing the short-chain component into cellulose or its derivatives, the intermolecular forces (intermolecular bonds) of cellulose can be reduced, and the mechanical properties such as elastic modulus, as well as the chemical resistance and surface hardness, can be improved.

[0043] In one embodiment of this present invention, the acylated cellulose is, but is not limited to, a hydroxyl group hydrogen atom of cellulose that is substituted with the long-chain component and the short-chain component, and the degree of substitution by the long-chain component (DS Lo ) and degree of substitution by short-chain components (DS Sh It is preferable that the following conditions (1) and (2) are met. DS Lo +DS Sh ≥ 2.1 (1) 4 ≤ DS Sh / DS Lo ≤ 12 (2)

[0044] In one embodiment of this model, the average number of introduced long-chain components per glucose unit of cellulose (DS Lo)(Ratio of long-chain component introduction), that is, the average number of hydroxy groups substituted with long-chain components (linear saturated aliphatic acyl groups having 4 or more carbon atoms, preferably 8 or more carbon atoms, more preferably 12 or more carbon atoms, and even more preferably 14 or more carbon atoms) per glucose unit (degree of hydroxyl group substitution) preferably satisfies the conditions of the above formulas (1) and (2). Also, DS Lo can be set, for example, in the range of 0.2 to 0.6 according to the structure and introduction amount of the short-chain component, the structure of the long-chain component, the physical properties required for the target product, and the efficiency during production. From the point of obtaining a more sufficient introduction effect of the long-chain component, DS Lo is preferably 0.2 or more, more preferably 0.3 or more, even more preferably 0.35 or more, and from the viewpoints of production efficiency and durability (strength, heat resistance, etc.), it is preferably 0.6 or less, more preferably 0.5 or less, and even more preferably 0.45 or less.

[0045] In one aspect of this embodiment, the average number of introduced short-chain components per glucose unit of cellulose (DS Sh )(Ratio of short-chain component introduction), that is, the average number of hydroxy groups substituted with short-chain components (acetyl group, propionyl group) per glucose unit (degree of hydroxyl group substitution) preferably satisfies the conditions of the above formulas (1) and (2) (note that 3 ≥ DS Lo + DS Sh ). Also, DS Sh can be set, for example, in the range of 1.7 to 2.8. From the point of sufficiently obtaining the introduction effect of the short-chain component, DS Sh is preferably 1.7 or more, and particularly from the viewpoints of water resistance, fluidity, etc., DS Sh is preferably 1.9 or more, more preferably 2.0 or more. From the viewpoint of sufficiently obtaining the effect of the long-chain component while obtaining the introduction effect of the short-chain component, DS Sh is preferably 2.6 or less, more preferably 2.3 or less, and even more preferably 2.2 or less.

[0046] The ratio of the ratio of the short-chain component to the ratio of the long-chain component (DS Sh / DS Lo) is not particularly limited, but is preferably between 4 and 12. If this ratio is too small, the material tends to become too flexible, reducing its strength and heat resistance, and if it is too large, it may lack thermoplasticity and become unsuitable for molding applications, etc. From these points of view, in one embodiment, DS Sh / DS Lo It is more preferable that the value be 4.5 or higher, more preferably 10 or lower, and even more preferably 7.5 or lower.

[0047] The sum of the ratio of long-chain components and the ratio of short-chain components (DS) Lo +DS Sh While not particularly limited, from the viewpoint of obtaining sufficient introduction effects of long-chain and short-chain components, a value of 2.1 or higher is preferred, 2.2 or higher is more preferred, and 2.25 or higher is even more preferred. Furthermore, from the viewpoint of mechanical properties, a value of 2.6 or lower is preferred, and 2.55 or lower is even more preferred.

[0048] (Amount of hydroxyl groups remaining in acylated cellulose) The greater the amount of residual hydroxyl groups, the greater the maximum strength and heat resistance of acylated cellulose, but also the greater the water absorption. Conversely, the higher the conversion rate (degree of substitution) of hydroxyl groups, the lower the water absorption, the greater the plasticity and fracture strain, but also the lower the maximum strength and heat resistance. Considering these trends, the conversion rate of hydroxyl groups can be set appropriately.

[0049] Average number of remaining hydroxyl groups per glucose unit in the final acylated cellulose product (hydroxyl group retention rate, DS) OH ) is not particularly limited, but can be set in the range of 0 to 0.9 (Note DS Lo +DS Sh +DS OH (=3). DS Lo +DS Sh If it is in the range of 2.1 to 2.6, DS OHThis can be set in the range of 0.4 to 0.9. Hydroxyl groups may remain from the viewpoint of mechanical properties such as maximum strength and durability such as heat resistance. For example, the hydroxyl group retention rate can be set to 0.01 or higher, and can be further set to 0.1 or higher. In particular, from the viewpoint of fluidity, the hydroxyl group retention rate of the final acylated cellulose is preferably 0.1 or higher, more preferably 0.2 or higher, preferably 0.9 or lower from the viewpoint of water resistance in addition to fluidity, and more preferably 0.6 or lower, and more preferably 0.5 or lower from the viewpoint of impact resistance.

[0050] (Synthesis of acylated cellulose) In the manufacturing method of this embodiment, a cellulose activation step (pretreatment step) may be included before the step of acylating the hydroxyl groups of cellulose. This will be explained below.

[0051] (Cellulose activation process) Before the acylation of the hydroxyl groups of cellulose (for example, a reaction step to introduce long-chain and short-chain components), an activation treatment (pretreatment step) can be performed to increase the reactivity of the cellulose. This activation treatment can be the same as the activation treatments that are normally performed before cellulose acylation (acetylation, etc.).

[0052] The activation treatment involves bringing the cellulose into contact with the solvent by a wet method, such as spraying an activating solvent compatible with cellulose onto the cellulose, or immersing the cellulose in the activating solvent (immersion method), thereby causing the cellulose to swell. This makes it easier for the reactant to penetrate between the cellulose molecular chains (and, if a solvent or catalyst is used, to penetrate along with them), thus improving the reactivity of the cellulose. Examples of activating solvents include water; carboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, and stearic acid; alcohols such as methanol, ethanol, propanol, and isopropanol; nitrogen-containing compounds such as dimethylformamide, formamide, ethanolamine, pyridine, and N-methylpyrrolidone; and sulfoxide compounds such as dimethyl sulfoxide. Two or more of these can be used in combination. Particularly preferred are water, acetic acid, pyridine, N-methylpyrrolidone, and dimethyl sulfoxide.

[0053] Activation can also be performed by adding cellulose to long-chain fatty acids. If the melting point of the long-chain fatty acids is above room temperature, they can also be heated above that melting point.

[0054] The amount of activating solvent used can be set to, for example, 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 30 parts by mass or more, per 100 parts by mass of cellulose. When immersing cellulose in the activating solvent, the amount can be set to, for example, 1 time or more, preferably 5 times or more, and more preferably 10 times or more, relative to the mass of cellulose. From the viewpoint of reducing the burden of removing the activating solvent after pretreatment and reducing material costs, a ratio of 300 times or less is preferred, 100 times or less is more preferred, and 50 times or less is even more preferred.

[0055] The activation temperature can be set appropriately within a range of, for example, 0 to 100°C. From the viewpoint of activation efficiency and reduction of energy costs, 10 to 40°C is preferred, and 15 to 35°C is more preferred.

[0056] When cellulose is added to a mixture of molten long-chain fatty acids, the mixture can be heated to a temperature above the melting point of the long-chain fatty acids.

[0057] The activation treatment time can be appropriately set within a range of, for example, 0.1 hours to 72 hours. From the viewpoint of ensuring sufficient activation while minimizing treatment time, 0.1 hours to 24 hours is preferred, and 0.5 hours to 3 hours is more preferred.

[0058] After the activation treatment, excess activation solvent can be removed by solid-liquid separation methods such as suction filtration, filter pressing, or compression.

[0059] After the activation treatment, the activation solvent contained in the cellulose can be replaced with the solvent used in the acylation reaction. For example, the activation solvent can be replaced with the solvent used in the reaction, and the replacement treatment can be carried out according to the immersion method of the activation treatment described above.

[0060] (The process of acylating the hydroxyl groups of cellulose) In the acylation process, the hydroxyl groups of cellulose dispersed in an organic solvent are acylated. For example, when producing acetylcellulose, the hydroxyl groups of cellulose dispersed in acetic acid can be acylated with acetic anhydride in the presence of sulfuric acid.

[0061] As one embodiment, a method for introducing long-chain and short-chain components by acylation of the hydroxyl groups of cellulose will be described.

[0062] (Process for introducing long-chain and short-chain components) The introduction step of the long-chain and short-chain components involves reacting cellulose (preferably cellulose with a degree of polymerization of 300 to 700) dispersed in an organic solvent, in the presence of an acid-scavenging component, and under heating, with a short-chain reagent (short-chain acylating agent) and a long-chain reagent (long-chain acylating agent) to acylate the hydroxyl groups of cellulose. It is preferable that the short-chain reagent (short-chain acylating agent) and the long-chain reagent (long-chain acylating agent) are dissolved in the solvent. The acid-scavenging component can also be used as the solvent. Below, as an example of the acylation step, a method is described in which the hydrogen atoms of the hydroxyl groups of cellulose are replaced by both the long-chain and short-chain components, but the present invention is not limited thereto. When replacing the hydrogen atoms of the hydroxyl groups of cellulose with only the short-chain component, the same method can be applied using only the short-chain reagent without using the long-chain reagent. When replacing the hydrogen atoms of the hydroxyl groups of cellulose with only the long-chain component, the same method can be applied using only the long-chain reagent without using the short-chain reagent.

[0063] As a long-chain reagent for introducing long-chain components into cellulose, acid chlorides of the linear saturated fatty acids mentioned above (e.g., stearoyl chloride) are preferred, and one may be used alone or two or more may be used in combination. As a short-chain reagent for introducing short-chain components into cellulose, acetyl chloride and / or propionyl chloride are preferred, and propionyl chloride is more preferred.

[0064] The amounts of long-chain and short-chain reagents added depend on the degree of substitution by the long-chain component of the target cellulose derivative (DS). Lo ) and degree of substitution by short-chain components (DS Sh ) can be set according to the following. If there is too much short-chain reagent, the amount of long-chain component bound will decrease, and the degree of substitution by the long-chain component (DS) will decrease. Lo ) tends to decrease.

[0065] The organic solvent should preferably be a good solvent for the target acylated cellulose. The solvent can be determined by the target acylated cellulose, but examples include acetic acid, dioxane, pyridine, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide. Nitrogen-containing basic solvents such as pyridine, N-methylpyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide are particularly preferred. When producing acetylcellulose, it is also preferable to use acetic acid as the solvent. The organic solvent may be used alone or as a mixture of two or more.

[0066] The acid-scavenging component is not particularly limited as long as it is a base that neutralizes the by-product acid (hydrochloric acid, acetic acid, propionic acid, etc.), and examples include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and barium hydroxide; metal alkoxides such as sodium methoxide and sodium ethoxide; and nitrogen-containing nucleophilic compounds such as diazabicycloundecene, diazabicyclononene, triethylamine, and pyridine. Among these, triethylamine and pyridine are preferred, and pyridine is particularly preferred because it can also be used as a solvent. When the acid-scavenging component is added separately from the solvent, it is preferable that the acid-scavenging component is present in the reaction system from the start of the reaction. If the acid-scavenging component is present in the reaction system at the start of the reaction, it may be added before or after the acylation agent is added.

[0067] The amount of acid scavenging component added is preferably 0.1 to 10 equivalents, and more preferably 0.5 to 5 equivalents, relative to the total amount of long-chain reagents (long-chain acylating agents) and short-chain reagents (short-chain acylating agents). However, this range is not limited when using nitrogen-containing nucleophilic compounds as solvents. If the amount of acid scavenging agent added is too small, the efficiency of the acylation reaction will decrease. Also, if the amount of acid scavenging agent added is too large, the cellulose may decompose and the molecular weight may decrease.

[0068] The reaction temperature in this acylation step is preferably 50 to 100°C, and more preferably 75 to 95°C. The reaction time can be set to 2 to 5 hours, and preferably to 3 to 4 hours. A sufficiently high reaction temperature allows for a high reaction rate, so the acylation reaction can be completed in a relatively short time, thereby increasing the reaction efficiency. In addition, if the reaction temperature is within the above range, the decrease in molecular weight due to heating can be suppressed.

[0069] The amount of organic solvent is not particularly limited, but it can be set to preferably 10 to 50 times the dry mass of cellulose, and more preferably 10 to 40 times (by mass ratio).

[0070] (ripening process) In one embodiment, after the introduction step of the long-chain and short-chain components described above, it is preferable to add an alkaline aqueous solution and maintain (age) the mixture while heating. The temperature during this aging process is preferably 25 to 75°C, more preferably 40 to 70°C, and the aging time can be set in the range of 1 to 5 hours, more preferably in the range of 1 to 3 hours.

[0071] The amount of alkaline aqueous solution added can be set to an amount equivalent to 3 to 30% by mass relative to the solvent used, with 5 to 20% by mass being preferred.

[0072] Examples of alkaline aqueous solutions include aqueous solutions of potassium hydroxide, sodium carbonate, and sodium bicarbonate, with aqueous solutions of sodium hydroxide being preferred. The concentration of the alkaline aqueous solution is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass.

[0073] Through this maturation process, the long-chain and short-chain components that have been bonded together undergo partial hydrolysis, restoring homogeneous hydroxyl groups. This improves mechanical properties such as strength and impact resistance, and also allows for the acquisition of a product with good properties (fine particles) in the subsequent precipitation process.

[0074] After the acylation step described above (preferably after the introduction step of the long-chain and / or short-chain components, or after the maturation step), alcohol may be added for quenching. The alcohol is not particularly limited, but examples include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, etc., with methanol being preferred. Two or more alcohols may be used in combination.

[0075] In one embodiment of this design, the cellulose derivative may be alkylcellulose. Alkylcellulose is a cellulose derivative in which cellulose has been partially O-alkylated. Examples of alkylcellulose include methylcellulose and ethylcellulose.

[0076] One method for synthesizing alkylcellulose involves mixing cellulose with an aqueous alkali metal hydroxide solution (e.g., sodium hydroxide, potassium hydroxide, lithium hydroxide) as a reaction catalyst in an organic solvent, and then reacting it with an etherifying agent such as methyl halide or ethyl halide (e.g., methyl chloride, ethyl chloride). The organic solvent is preferably a good solvent for the target alkylcellulose. The solvent can be determined by the target alkylcellulose, but examples include dioxane, pyridine, N-methylpyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, acetone, methyl ethyl ketone, and ethyl acetate. One organic solvent may be used alone, or two or more may be used in combination.

[0077] In one embodiment of this disclosure, in the cellulose derivative synthesis step, a compound in which some of the hydroxyl groups of cellulose are substituted (first cellulose derivative) may be used as a raw material, and a substituent may be introduced on some or all of the remaining hydroxyl groups to synthesize a second cellulose derivative. For example, cellulose acetate in which some of the hydrogen atoms of the hydroxyl groups of cellulose are substituted with acetyl groups may be used as a raw material, and cellulose propionate acetate may be synthesized by substituting the remaining some or all of the hydrogen atoms of the hydroxyl groups with propionyl groups. Acylation can be carried out by the same method as the step of acyling the hydroxyl groups of cellulose described above.

[0078] <Precipitation process> In one embodiment of the precipitation process, a first dispersion in which cellulose nanofibers are dispersed in a poor solvent for the synthesized cellulose derivative is mixed with a reaction solution containing the synthesized cellulose derivative to precipitate the cellulose derivative. In another embodiment, a second dispersion is prepared by dispersing cellulose nanofibers in a reaction solution containing the synthesized cellulose derivative, and the second dispersion is mixed with a poor solvent for the cellulose derivative to precipitate the cellulose derivative.

[0079] In this specification, a poor solvent for a cellulose derivative means a solvent that cannot dissolve the target cellulose derivative (or a solvent with low solute solubility), for example, a solvent in which the solubility of the solute (cellulose derivative) at 25°C is preferably less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less.

[0080] As one aspect of this embodiment, a precipitation step after the synthesis of acylated cellulose will be described. The reaction solution after the acylation step (a reaction solution containing the synthesized acylated cellulose) contains the product, acylated cellulose (for example, a cellulose derivative into which long-chain and / or short-chain components have been introduced, or acetylcellulose). The acylated cellulose may be one type or two or more types. In the precipitation step, the acylated cellulose is precipitated by mixing the reaction solution containing the synthesized acylated cellulose with a poor solvent (also simply referred to as "poor solvent") for the cellulose derivative (the product, acylated cellulose). By performing the precipitation step using a solution in which cellulose nanofibers are dispersed in a poor solvent, the cellulose derivative precipitates so as to adhere to the cellulose nanofibers, and as a result, fiber-reinforced acylated cellulose in which cellulose nanofibers are highly dispersed in the cellulose derivative is obtained. In the embodiments of this disclosure, since the mixing of the cellulose derivative and cellulose nanofibers and the precipitation of the cellulose derivative are performed simultaneously in the precipitation step of the cellulose derivative, a fiber-reinforced cellulose resin can be obtained with fewer steps compared to conventional manufacturing methods. Furthermore, since the reaction solution obtained from the synthesis of the cellulose derivative is used as is, there is the advantage of being able to reduce the amount of solvent required for mixing with cellulose nanofibers. According to the embodiments of this disclosure, a fiber-reinforced cellulose resin in which cellulose nanofibers are highly dispersed in the cellulose derivative can be easily obtained.

[0081] In the precipitation step, a first dispersion in which cellulose nanofibers are dispersed in a poor solvent (preferably an aqueous solvent) for acylated cellulose may be used (Embodiment 1), or a second dispersion in which cellulose nanofibers are dispersed in a reaction solution containing the synthesized acylated cellulose may be used (Embodiment 2). In one embodiment, both a dispersion in which cellulose nanofibers are dispersed in an aqueous solvent and a solution in which cellulose nanofibers are dispersed in the reaction solution after the synthesis of acylated cellulose may be used.

[0082] (Cellulose nanofiber) The fiber diameter of the cellulose nanofiber is not particularly limited, but for example, it is preferably an average fiber diameter of 3 to 200 nm. The cellulose nanofiber may consist of single fibers that are not aligned but are sufficiently spaced apart to intertwine with each other. In this case, the average fiber diameter is the average diameter of the single fibers. Furthermore, the fiber according to the present invention may consist of multiple single fibers bundled together to form a single thread, in which case the average fiber diameter is defined as the average value of the diameter of one thread.

[0083] The length of the cellulose nanofibers is not particularly limited, but an average length of, for example, 100 nm or more is preferred. If the average length of the fibers is too short, the reinforcing effect may be low, and the strength of the fiber-reinforced composite material may be insufficient. In one embodiment, the fibers may contain fibers with a length of less than 100 nm, but the proportion of such fibers is preferably 30% by mass or less. The average aspect ratio of the cellulose nanofibers is not particularly limited, but for example, it is between 20 and 350.

[0084] The average fiber diameter and aspect ratio of cellulose nanofibers are arithmetic mean values ​​measured over at least 50 cellulose nanofibers within the field of view of an electron microscope. Cellulose nanofibers obtained by various known methods can be used.

[0085] Known raw materials for cellulose nanofibers can be derived from plant materials such as wood. Cellulose nanofibers using plant-based raw materials can be manufactured by, for example, chemically treating the raw material to make it easily defibrillable, and then physically treating it with mechanical shear force to defibrillate it; or by physically defibrillating the raw material using known methods employing high mechanical shear force, such as high-pressure homogenizer methods, grinder grinding methods, freeze-drying methods, strong shear force kneading methods, and ball mill grinding methods.

[0086] Cellulose nanofibers may have anionic groups. Cellulose nanofibers having anionic groups can be obtained by introducing anionic groups into a raw material during chemical treatment or after physical defibration, and then further refining (defibration). In the refinement process, defibration is easily achieved due to the repulsive effect of the anionic groups. Examples of anionic groups include carboxylic acid groups, phosphate groups, sulfonic acid groups, sulfate groups, phosphite groups, and xantate groups (-OCSS). - ) and one or more of these salts are included. Examples of cellulose nanofibers having anionic groups include oxidized cellulose nanofibers having carboxyl groups or salts of carboxyl groups, phosphate-esterified cellulose nanofibers having phosphate groups or salts of phosphate groups, sulfate-esterified cellulose nanofibers having sulfate groups or salts of sulfate groups, phosphite-esterified cellulose nanofibers having phosphite groups or salts of phosphite groups, and xantate-treated cellulose nanofibers having xantate groups or salts of xantate groups. Examples of oxidized cellulose nanofibers include TEMPO-oxidized cellulose nanofibers and carboxymethylated cellulose nanofibers.

[0087] In this disclosure, the cellulose nanofibers used may be those isolated from plants or bacterial cellulose produced by bacterial cellulose. One type of cellulose nanofiber may be used alone, or two or more types may be used together.

[0088] (Poor solvent for acylated cellulose) A poor solvent for acylated cellulose is a solvent that cannot dissolve the target acylated cellulose, for example, a solvent that cannot dissolve 1% by mass or more of acylated cellulose at 25°C. Aqueous solvents are examples of poor solvents for acylated cellulose. Aqueous solvents are not particularly limited, but examples include water, lower alcohols with 1 to 3 carbon atoms, or mixtures thereof. Various types of water can be used, such as distilled water, purified water, tap water, industrial water, ion-exchanged water, deionized water, pure water, electrolyzed water, and physiological saline. The aqueous solvent preferably contains 90% by mass or more water, more preferably 99% by mass or more water, and may be 100% by mass water. In this specification, the term "aqueous solvent" may be used to refer to a poor solvent for acylated cellulose, but unless otherwise specified, it can also be applied to other poor solvents for acylated cellulose.

[0089] The mixing ratio of cellulose nanofibers to acylated cellulose in the precipitation step is not particularly limited, but it is preferable to mix cellulose nanofibers in an amount of 0.01 to 0.5 times, more preferably 0.02 to 0.3 times, relative to the mass of acylated cellulose produced in the acylation step. The same applies even if the cellulose derivative is something other than acylated cellulose.

[0090] The above describes the precipitation process of acylated cellulose as an example, but the same procedure applies to other cellulose derivatives such as alkylcellulose. The aqueous solvents listed above as poor solvents for acylated cellulose can be used as poor solvents for alkylcellulose.

[0091] Next, Embodiments 1 and 2 of the precipitation process will be described.

[0092] (Embodiment 1) In Embodiment 1, a dispersion in which cellulose nanofibers are dispersed in a poor solvent (preferably an aqueous solvent) for acylated cellulose (also referred to as the "first dispersion") is mixed with a reaction solution obtained by synthesizing acylated cellulose from cellulose (also simply referred to as the "reaction solution") to precipitate acylated cellulose. Because cellulose nanofibers are highly hydrophilic, they can be easily dispersed in an aqueous solvent.

[0093] In the first dispersion, the cellulose nanofibers are preferably dispersed in a poor solvent for acylated cellulose in an amount of 0.01% by mass or more, more preferably 0.1% by mass or more, and preferably 10% by mass or less, and more preferably 5% by mass or less, but are not limited to this amount. If the content of cellulose nanofibers in the first dispersion is too low, the acylated cellulose may not be sufficiently strengthened. Also, if the content of cellulose nanofibers in the dispersion is too high, aggregates of cellulose nanofibers may easily form.

[0094] The method for dispersing cellulose nanofibers in a poor solvent (preferably an aqueous solvent) relative to acylated cellulose is not particularly limited, but dispersers such as centrifugal dispersers (flow jet mixers, fine flow mills, etc.), media-type dispersers (ball mills, sand mills, etc.), ultrasonic dispersers, and homogenizers may be used.

[0095] The method for mixing the reaction solution after synthesizing acylated cellulose with the first dispersion is not particularly limited. For example, the first dispersion may be added to the reaction solution, or the reaction solution may be added to the first dispersion, or the reaction solution and the first dispersion may be mixed simultaneously. Preferably, the first dispersion is added to the reaction solution. The reaction solution may contain alcohol or the like used for quenching. The volume ratio of the first dispersion to the reaction solution is not particularly limited, but is preferably 10:1 to 1:10. In addition, an organic solvent (preferably a good solvent for acylated cellulose, which may be the same or different type of organic solvent used in the acylation step) may be added separately during mixing.

[0096] When adding the first dispersion to the reaction solution, the first dispersion may be added intermittently or continuously within a predetermined time, or it may be added all at once in a short time (within about 1 minute). The time for mixing (contacting) the reaction solution and the first dispersion should be sufficient for the acylated cellulose to precipitate, for example, preferably 1 minute or more, more preferably 5 minutes or more, and preferably 200 minutes or less, more preferably 100 minutes or less. The temperature during mixing is not particularly limited, but is preferably 10°C to 50°C.

[0097] As a method for mixing the reaction solution and the first dispersion, known stirring methods may be used, such as liquid-phase stirring using a stirring blade.

[0098] (Embodiment 2) In Embodiment 2, a second dispersion is prepared by dispersing cellulose nanofibers in the reaction solution after synthesizing acylated cellulose. This second dispersion is then mixed with a poor solvent for acylated cellulose (preferably an aqueous solvent) to precipitate the acylated cellulose. In a preferred example, a poor solvent for acylated cellulose that does not contain cellulose nanofibers is mixed with a second dispersion in which cellulose nanofibers are dispersed in the reaction solution. The second dispersion may contain alcohol or the like used for quenching after the acylation step. The second dispersion may also contain solvents not used in the acylation step; for example, it may contain the same type of solvent as the organic solvent used in the acylation step.

[0099] In Embodiment 2, the cellulose nanofibers are preferably dispersed in the second dispersion in an amount that is not limited to 0.01% by mass or more, more preferably 0.1% by mass or more, and preferably 10% by mass or less, and more preferably 5% by mass or less.

[0100] In Embodiment 2, it is preferable to disperse the cellulose nanofibers in the reaction solution immediately before or immediately after adding the alcohol for quenching (preferably within 1 minute before or after adding the quenching alcohol). Dispersing the cellulose nanofibers in the reaction solution may cause the cellulose nanofibers to be acylated as well. On the other hand, if it is preferable to make the polarity of the cellulose nanofibers similar to that of acylated cellulose, the cellulose nanofibers may be dispersed at an earlier stage of the acylation process.

[0101] The method for dispersing cellulose nanofibers in the reaction solution after synthesizing acylated cellulose is not particularly limited, but dispersers such as centrifugal dispersers (flow jet mixers, fine flow mills, etc.), media-type dispersers (ball mills, sand mills, etc.), ultrasonic dispersers, and homogenizers may be used.

[0102] The method for mixing the poor solvent for acylated cellulose with the second dispersion can be as follows: adding the poor solvent to the second dispersion, adding the second dispersion to the poor solvent, or mixing the poor solvent and the second dispersion simultaneously. Preferably, the poor solvent is added to the second dispersion. The volume ratio of the poor solvent to the second dispersion with respect to the acylated cellulose during mixing is not particularly limited, but for example, it is preferably 10:1 to 1:10.

[0103] When adding a poor solvent for acylated cellulose to the second dispersion, the poor solvent may be added intermittently or continuously over a predetermined time, or it may be added all at once over a short period of time (within about 1 minute). The time for mixing (contacting) the second dispersion and the poor solvent should be sufficient for the acylated cellulose to precipitate, for example, preferably 1 minute or more, more preferably 5 minutes or more, and preferably 200 minutes or less, more preferably 100 minutes or less. The temperature during mixing is preferably 10°C to 50°C.

[0104] As a method for mixing the second dispersion with the poor solvent, known stirring methods can be used, such as liquid-phase stirring using a stirring blade.

[0105] When alkylcellulose is synthesized as a cellulose derivative, alkylcellulose can be precipitated in the same manner as in Embodiment 1 or Embodiment 2 of the acylated cellulose precipitation step described above. The same applies when precipitating cellulose derivatives other than acylated cellulose and alkylcellulose.

[0106] <Solid-liquid separation process> After the precipitation process described above, the precipitated fiber-reinforced cellulose resin can be recovered by solid-liquid separation. Methods for solid-liquid separation include filtration (natural filtration, reduced pressure filtration, pressure filtration, centrifugal filtration, and thermal filtration thereof), natural sedimentation / flotation, liquid-liquid separation, centrifugal separation, and compression, and these may be combined as appropriate. Suction filtration is particularly preferred. The filter used for filtration is not particularly limited; filter paper, glass filters, membrane filters, polypropylene filter cloth, polyester filter cloth, nylon filter cloth, etc., can be used.

[0107] After solid-liquid separation, the material can be washed with methanol or other solvents as needed and then dried.

[0108] The fiber-reinforced cellulose resin produced by the manufacturing method of this embodiment can be used, for example, as a base resin for molding materials. This molding material is suitable for molded articles such as electronic device casings, automobile bodies, and building materials. Because the fiber-reinforced cellulose resin produced by the manufacturing method of this embodiment has a high dispersion of cellulose nanofibers in the cellulose derivative, it can form molded articles with excellent appearance and high strength. [Examples]

[0109] The present invention will be described in more detail below with specific examples.

[0110] (Synthesis Example 1) Cellulose-based resins were obtained by activating cellulose (pulp) and then acyling it in a heterogeneous solid-liquid system. Specifically, cellulose-based resins (cellulose propionate stearate) were prepared according to the following procedure.

[0111] 6.0 g of cellulose 1 (dissolved pulp powder, moisture content 6.4%, DP (degree of polymerization) 560) (calculated by dry mass, 37 mmol / glucose units) was added to the reactor, dispersed in 90 ml of pyridine under a nitrogen atmosphere, and activated by stirring overnight at room temperature.

[0112] Subsequently, the cellulose dispersion was cooled to below 10°C, and a mixture of 7.85 g (26 mmol) of stearoyl chloride and 10.28 g (111 mmol) of propionyl chloride, which had been pre-mixed, was added to the reactor while maintaining the temperature below 10°C.

[0113] After heating and stirring at 100°C for 4.5 hours, the mixture was cooled to 50°C, and 125 ml of methanol was added dropwise, stirring for about 30 minutes to obtain reaction solution A.

[0114] Furthermore, 40 ml of water was added to precipitate the product, which was then collected by suction filtration. The obtained solid was washed with 100 ml of methanol until the filtrate was no longer colored (4 times).

[0115] The washed solids were vacuum-dried at 105°C for 5 hours to obtain 13.9 g of powdered cellulose acylate (cellulose propionate stearate) (yield 98%).

[0116] The obtained sample (cellulose propionate stearate) 1 Measurements were taken using 1H-NMR (Bruker, AV-400, 400MHz, solvent: CDCl3 (partially dissolved)) and DS Lo 0.42, DS Sh The value was 2.02.

[0117] <Example 1> Cellulose nanofibers (manufactured by Sugino Machine, BMa-10002, 2% by mass) were diluted with pure water to prepare 40 ml of an aqueous dispersion of cellulose nanofibers (1% by mass). Meanwhile, cellulose was acylated in the same manner as in Synthesis Example 1, and methanol was added dropwise and stirred to obtain reaction solution A. Subsequently, the aforementioned aqueous dispersion of cellulose nanofibers was added to reaction solution A and stirred to precipitate the product, which was then collected by suction filtration. The obtained solid was washed with 100 ml of methanol until the color of the filtrate disappeared (4 times).

[0118] The washed solids were vacuum-dried at 105°C for 5 hours to obtain 14.3 g of powdered fiber-reinforced cellulose resin 1 (a composite of cellulose propionate stearate and cellulose nanofibers).

[0119] (Preparation of pellets by kneading) Pellet 1 was prepared by kneading the obtained fiber-reinforced cellulose resin 1 using a kneader (manufactured by Thermo Electron Corporation, product name: HAAKE MiniLab Rheomex CTW5). The kneader's kneading chamber temperature was set to 200°C and the rotation speed to 60 rpm.

[0120] (Preparation of sample for haze measurement: Evaluation sample 1) The pellet 1 obtained by kneading was dried again at 80°C for 5 hours immediately before molding, and a molded body (evaluation sample 1) with the following shape was produced using a hot press molding machine (manufactured by Tester Industries, product name: SA-303-II-S).

[0121] Molded body: A disc-shaped molded body with a diameter of 30 mm and a thickness of 100 μm. The molding conditions were set as follows: Set temperature: 200℃ Pressure: 10 MPa

[0122] (Measurement of haze) The haze (cloudiness value) of the obtained evaluation sample 1 was measured using a haze meter (manufactured by Murakami Color Technology Laboratory, product name: HM-65W, compliant with JIS K 7136). A D65 light source was used.

[0123] (Fabrication of injection-molded parts: Sample 2 for evaluation) Using injection molding (Thermo Electron Corporation, HAAKE MiniJet II), a molded body (evaluation sample 2) with the shape shown below was fabricated from pellet 1 obtained by kneading. The pellet was dried at 80°C for 5 hours immediately before molding.

[0124] Molded body size: Thickness 4.0mm, width 10.0mm, length 80mm At that time, the molding machine cylinder temperature was set to 210°C, the mold temperature to 60°C, the injection pressure to 1200 bar (120 MPa) for 5 seconds, and the holding pressure to 600 bar (60 MPa) for 20 seconds.

[0125] (Measurement of flexural modulus) The flexural modulus of the obtained evaluation sample 2 was measured in accordance with JIS K 7171.

[0126] <Comparative Example 1> Cellulose nanofibers (manufactured by Sugino Machine, BMa-10002, 2% by weight) were diluted with pure water to prepare 40 ml of an aqueous dispersion of cellulose nanofibers (1% by weight). 13.9 g of powdered cellulose acylate (cellulose propionate stearate) obtained in Synthesis Example 1 was added to this dispersion and stirred. The solid was recovered by suction filtration and compression. This solid was dried at 80°C for 5 hours and kneaded in the same manner as in Example 1 to prepare pellet c1. Evaluation samples c1 and c2 were prepared in the same manner as evaluation samples 1 and 2 in Example 1, except that pellet 1 was replaced with pellet c1. Haze and flexural modulus were measured using evaluation samples c1 and c2, respectively, in the same manner as in Example 1.

[0127] <Reference example 2> Pellet r2 was prepared by kneading the powdered cellulose acylate (cellulose propionate stearate) obtained in Synthesis Example 1 in the same manner as in Example 1. Pellet r2 does not contain cellulose nanofibers. Evaluation samples r1 and r2 were prepared in the same manner as evaluation samples 1 and 2 in Example 1, except that pellet 1 was replaced with pellet r2. Haze and flexural modulus were measured using evaluation samples r1 and r2, respectively, in the same manner as in Example 1.

[0128] The evaluation results are shown in Table 1.

[0129] [Table 1]

[0130] As shown in Table 1, in Example 1, a fiber-reinforced cellulose resin with lower haze and higher flexural modulus was obtained compared to Comparative Example 1. These results are presumed to be due to the fact that Example 1, produced by the manufacturing method of this embodiment, yielded a fiber-reinforced cellulose resin with a higher dispersion rate of cellulose nanofibers compared to Comparative Example 1.

[0131] Although the present invention has been described above with reference to embodiments and examples, the present invention is not limited to the above embodiments and examples. Various modifications to the configuration and details of the present invention can be made that can be understood by those skilled in the art within the scope of the present invention.

[0132] Some or all of the embodiments described above may also be described as follows, but the disclosures of this application are not limited to the following.

[0133] (Note 1) A step of synthesizing a cellulose derivative in an organic solvent to obtain a reaction solution containing the cellulose derivative, A step of precipitating the cellulose derivative by mixing a first dispersion in which cellulose nanofibers are dispersed in a poor solvent for the cellulose derivative with the reaction solution, A method for producing fiber-reinforced cellulose resins, including [the specified component].

[0134] (Note 2) A step of synthesizing a cellulose derivative in an organic solvent to obtain a reaction solution containing the cellulose derivative, A step of dispersing cellulose nanofibers in the reaction solution to prepare a second dispersion, A step of mixing the poor solvent for the cellulose derivative with the second dispersion to precipitate the cellulose derivative, A method for producing fiber-reinforced cellulose resins, including [the specified component].

[0135] (Note 3) A method for producing a fiber-reinforced cellulose resin according to Appendix 1 or 2, wherein the organic solvent is a good solvent for the cellulose derivative.

[0136] (Note 4) A method for producing a fiber-reinforced cellulose resin according to any one of the appendices 1 to 3, wherein the cellulose derivative is acylated cellulose and / or alkyl cellulose.

[0137] (Note 5) A method for producing a fiber-reinforced cellulose resin according to any one of the appendices 1 to 4, wherein the poor solvent for the cellulose derivative is an aqueous solvent.

[0138] This application claims priority based on Japanese Patent Application No. 2022-175695, filed on November 1, 2022, and incorporates all of its disclosures herein.

Claims

1. A step of synthesizing a cellulose derivative in an organic solvent to obtain a reaction solution containing the cellulose derivative, A step of precipitating the cellulose derivative by mixing a first dispersion in which cellulose nanofibers are dispersed in a poor solvent for the cellulose derivative with the reaction solution, A method for producing fiber-reinforced cellulose resins, including [the specified component].

2. A step of synthesizing a cellulose derivative in an organic solvent to obtain a reaction solution containing the cellulose derivative, A step of dispersing cellulose nanofibers in the reaction solution to prepare a second dispersion, A step of mixing the poor solvent for the cellulose derivative with the second dispersion to precipitate the cellulose derivative, A method for producing fiber-reinforced cellulose resins, including [the specified component].

3. A method for producing a fiber-reinforced cellulose resin according to claim 1 or 2, wherein the organic solvent is a good solvent for the cellulose derivative.

4. A method for producing a fiber-reinforced cellulose resin according to claim 1 or 2, wherein the cellulose derivative is acylated cellulose and / or alkyl cellulose.

5. A method for producing a fiber-reinforced cellulose resin according to claim 1 or 2, wherein the poor solvent for the cellulose derivative is an aqueous solvent.

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