Cellulose particles and method for producing the same

Abstract

To provide a production method in which a cellulose particle having a high degree of sphericity can easily be produced, and to provide a cellulose particle having high sphericity and small pore volume.SOLUTION: Provided are [1] a method for producing cellulose particle that includes a step in which a water-in-oil type emulsion containing cellulose and an alcohol having an octanol / water distribution coefficient ClogP of 0.5 or more are mixed and the cellulose is precipitated to yield a cellulose particle, and [2] a cellulose particle in which the sphericity is 0.80 or more and the pore volume is 0.3 mL / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to cellulose particles and a method for producing the same. [Background technology]

[0002] Spherical particles are used in cosmetics and the like to improve slipperiness, for example.

[0003] Here, methods for producing spherical particles of cellulose are known. Patent Document 1 describes a method for producing regenerated cellulose spherical particles, which includes the steps of supplying a cellulose solution into a current of inert gas to atomize the cellulose solution and converting it into minute droplets in the gas phase; and contacting the droplets with a coagulation liquid to form regenerated cellulose spherical particles. Patent Document 2 describes a method for producing porous cellulose beads, which comprises a step of cooling a cellulose dope prepared by mixing an alkaline aqueous solution with raw cellulose powder to a temperature lower than -12°C, and a step of adjusting the temperature of the cellulose dope to a temperature higher than 15°C after the cooling step. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-133355 [Patent Document 2] International Publication No. 2018 / 186222 Summary of the Invention [Problem to be solved by the invention]

[0005] The method of Patent Document 1 has a problem in terms of simplicity, and the method of Patent Document 2 cannot be said to have been sufficiently considered from the viewpoint of spherical shapes. One embodiment of the present invention relates to providing a method for easily producing cellulose particles with high sphericity. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by bringing a specific alcohol into contact with a water-in-oil emulsion of cellulose to precipitate the cellulose.

[0007] That is, one embodiment of the present invention relates to the following [1] and [2]. [1] A method for producing cellulose particles, comprising the steps of mixing a water-in-oil emulsion containing cellulose with an alcohol having an octanol / water partition coefficient ClogP of 0.5 or more, and precipitating the cellulose to obtain cellulose particles. [2] Cellulose particles having a sphericity of 0.80 or more and a pore volume of 0.3 mL / g or less. [Effects of the Invention]

[0008] According to one embodiment of the present invention, a production method that can easily produce cellulose particles with high sphericity can be provided, and cellulose particles with high sphericity and small pore volume can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows the appearance of the cellulose particles obtained in Example 1 and an SEM image of the cut surface. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Method of manufacturing cellulose particles] A method for producing cellulose particles according to one embodiment of the present invention includes the steps of mixing a water-in-oil emulsion containing cellulose with an alcohol having an octanol / water partition coefficient ClogP of 0.5 or more, and precipitating the cellulose to obtain cellulose particles. A method for producing cellulose particles according to one embodiment of the present invention includes the steps of mixing a water-in-oil emulsion containing cellulose and an organic solvent with an alcohol having an octanol / water partition coefficient ClogP of 0.5 or greater, and precipitating the cellulose to obtain cellulose particles. A method for producing cellulose particles according to one embodiment of the present invention preferably includes the following steps (A) to (C) in this order. Step (A): A step of mixing an alkaline aqueous solution with cellulose to obtain a cellulose aqueous solution in which the cellulose is dissolved in the alkaline aqueous solution. Step (B): A step of mixing an aqueous cellulose solution with an organic solvent to obtain a water-in-oil emulsion of cellulose. Step (C): A step of mixing the water-in-oil emulsion with an alcohol having an octanol / water partition coefficient ClogP of 0.5 or more to precipitate cellulose and obtain cellulose particles. According to the method for producing cellulose particles according to this embodiment, cellulose particles with high sphericity can be produced easily. In this embodiment, the octanol / water partition coefficient ClogP is a measure of the partitioning of a substance between an octanol phase and an aqueous phase, and serves as an index of the hydrophobicity of a chemical substance. ClogP represents the calculated value of the octanol-water partition coefficient (logP) defined by the following formula, calculated according to Perkin Elmer's ChemDraw Professional 19.1: logP = log([substance]octanol / [substance]water) In the above formula, [substance] octanol indicates the molar concentration of the substance in the 1-octanol phase, and [substance] water indicates the molar concentration of the substance in the aqueous phase.

[0011] The reason why the cellulose particles according to this embodiment have a high degree of sphericity is not clear, but is thought to be as follows. Alcohols with an octanol / water partition coefficient ClogP within the above range have good compatibility with the organic solvent that serves as the dispersant for a water-in-oil emulsion of cellulose, but poor compatibility with water, the dispersoid. Therefore, when a water-in-oil emulsion of cellulose is contacted with the alcohol, the water in the emulsion is gradually replaced with alcohol, slowing the cellulose precipitation rate and resulting in phase separation of the cellulose while maintaining a high level of sphericity. Even if the emulsion aggregates after contact with the alcohol, the slow cellulose precipitation rate is likely to result in cellulose particles with a similarly high degree of sphericity. Furthermore, the slow cellulose precipitation rate is likely to result in a decrease in particle porosity, resulting in cellulose particles that are nearly solid. For the above reasons, it is believed that the method for producing cellulose particles according to this embodiment makes it possible to obtain cellulose particles with high sphericity. Each component and each step used in the production method of the present invention will be explained below in order.

[0012] <Process (A)> In step (A), an aqueous cellulose solution is obtained by mixing an alkaline aqueous solution with cellulose. Here, the "cellulose dissolved" state refers to a state in which the aqueous cellulose solution is transparent to the naked eye, and the cellulose may be partially dispersed.

[0013] The cellulose used as the raw material for the cellulose particles according to this embodiment (hereinafter also referred to as "raw cellulose") can be chemically pure cellulose. Examples of raw cellulose include wood such as various wood chips, pruned branches of various trees, thinned wood, branches, construction waste, and industrial waste; wood pulp produced from wood, pulp such as cotton linter pulp obtained from fibers surrounding cotton seeds; paper such as newspaper, cardboard, magazines, and fine paper; plant stems and leaves such as rice straw and corn stalks; and plant shells such as rice husks, palm shells, and coconut shells. Among these, from the viewpoints of cellulose purity in the raw material, degree of polymerization of cellulose, and ease of availability, pulp such as various wood chips, pruned branches of various trees, thinned wood, branches, construction waste, and industrial waste; wood pulp produced from wood, and cotton linter pulp obtained from fibers surrounding cotton seeds are preferred. The raw material cellulose may be in the form of, for example, powder, sheet, cotton, etc. Among these, the powder form is preferred from the viewpoint of excellent solubility in an alkaline aqueous solution.

[0014] The degree of polymerization of the starting cellulose is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less, from the viewpoint of improving solubility in an alkaline aqueous solution, and is preferably 10 or more, more preferably 50 or more, even more preferably 100 or more, and even more preferably 150 or more, from the viewpoint of further improving the mechanical strength and sphericity of the resulting cellulose particles.

[0015] Furthermore, when the starting cellulose is in a powdered form, the average ellipsoidal diameter of the starting cellulose is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 5 μm or more, and even more preferably 10 μm or more, from the viewpoints of handleability and productivity, and is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less, from the viewpoint of improving solubility in an alkaline aqueous solution. Here, the equivalent circumferential diameter in this embodiment refers to the diameter of a circle having the same circumferential length as the circumferential length of the particle. The average equivalent circumferential diameter in this embodiment is the number average of the equivalent circumferential diameters of 50 randomly selected particles. The equivalent circumferential diameter of a particle can be calculated from an electron microscope (SEM) image using, for example, image analysis particle size distribution measurement software Mac-View ver. 4.

[0016] The alkaline aqueous solution according to the present embodiment is not particularly limited as long as it is alkaline and can dissolve cellulose. Here, "being able to dissolve cellulose" means, for example, that cellulose is mixed with the alkaline aqueous solution in an amount that results in a 4% by mass solution, and dissolution can be confirmed visually. Examples of basic compounds in the alkaline aqueous solution according to this embodiment include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; and tertiary amines such as trimethylamine and triethylamine. Among these, alkali metal hydroxides are preferred, and at least one selected from sodium hydroxide and potassium hydroxide is more preferred, with sodium hydroxide being even more preferred from the viewpoint of availability. The above basic compounds can be used alone or in combination of two or more kinds.

[0017] From the viewpoint of improving the solubility of cellulose, the concentration of the basic compound in the alkaline aqueous solution is preferably 5% by mass or more, more preferably 6% by mass or more, even more preferably 7% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 12% by mass or less, even more preferably 10% by mass or less. The concentration of the basic compound in the aqueous alkaline solution may be adjusted by adding aqueous alkaline solutions of different concentrations separately so that the final concentration falls within the above range.

[0018] The dissolution of cellulose in the alkaline aqueous solution is preferably carried out, for example, by adding cellulose to the alkaline aqueous solution and stirring and mixing. The temperature at which cellulose is dissolved in the alkaline aqueous solution is preferably −20° C. or higher, more preferably −10° C. or higher, even more preferably −5° C. or higher, and is preferably 10° C. or lower, more preferably 5° C. or lower, even more preferably 0° C. or lower, from the viewpoint of improving the solubility of cellulose without freezing. The stirring time is not particularly limited as it depends on the scale of production, the concentration of the alkaline aqueous solution, the amount added, and the temperature, and is set appropriately, and is usually continued until the cellulose is visually dissolved.

[0019] The cellulose concentration of the cellulose aqueous solution may be determined appropriately taking into consideration the solubility of cellulose, the handleability of the cellulose aqueous solution, the particle size of the desired cellulose particles, etc., but is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 12% by mass or less, even more preferably 10% by mass or less, even more preferably 8% by mass or less, and even more preferably 6% by mass or less.

[0020] <Process (B)> In step (B), the aqueous cellulose solution obtained in step (A) is mixed with an organic solvent to obtain a water-in-oil emulsion of cellulose. The organic solvent is preferably an alcohol having an octanol / water partition coefficient ClogP of 0.5 or more. In this step, the aqueous cellulose solution obtained in step (A) is mixed with an organic solvent to prepare a water-in-oil emulsion in which the aqueous cellulose solution is emulsified in the organic solvent. The organic solvent is not particularly limited as long as it can prepare a water-in-oil emulsion of the aqueous cellulose solution and can keep the emulsion stable.

[0021] The octanol / water partition coefficient ClogP of the organic solvent is preferably 0.70 or more, more preferably 0.90 or more, even more preferably 1.0 or more, even more preferably 1.2 or more, even more preferably 2.0 or more, and even more preferably 3.0 or more, from the viewpoint of obtaining a water-in-oil emulsion in step (B) and further increasing the sphericity of the obtained cellulose particles. The upper limit of the octanol / water partition coefficient ClogP of the organic solvent is not particularly limited, but, for example, from the viewpoint of solubility in alcohol in step (C), it is preferably 6.0 or less, more preferably 5.0 or less, even more preferably 4.5 or less, and even more preferably 4.0 or less. In this embodiment, when the organic solvent is a mixed solvent, the octanol / water partition coefficient ClogP of the organic solvent can be a weighted average value of the ClogP of each solvent constituting the mixed solvent.

[0022] Examples of organic solvents include aliphatic hydrocarbons such as n-hexane, n-heptane, dichloromethane, dichloroethane, and chloroform; alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, cycloheptane, and methylcycloheptane; aromatic hydrocarbons such as toluene, xylene, and dichlorobenzene; and esters such as ethyl acetate and fatty acid glycerin esters. These organic solvents may be used alone or in combination of two or more. In this embodiment, the aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and esters also include partially halogenated halides. From these perspectives, preferred organic solvents are one or more selected from hydrocarbons and esters, each of which may have a halogen atom. The carbon number of the hydrocarbon and ester is preferably 4 or more, more preferably 6 or more, and preferably 22 or less, more preferably 12 or less. Among these, at least one selected from aliphatic hydrocarbons having 6 to 10 carbon atoms, alicyclic hydrocarbons having 6 to 10 carbon atoms, aromatic hydrocarbons having 6 to 10 carbon atoms, and esters having 4 to 10 carbon atoms is preferred, at least one selected from ethyl acetate, dichloromethane, chloroform, toluene, dichlorobenzene, and n-hexane is more preferred, at least one selected from dichloromethane, chloroform, toluene, dichlorobenzene, and n-hexane is even more preferred, at least one selected from dichlorobenzene and n-hexane is even more preferred, and n-hexane is even more preferred.

[0023] The amount of organic solvent to be mixed should be an amount that is sufficient to sufficiently emulsify the cellulose aqueous solution and can be determined appropriately taking into consideration the particle size of the desired cellulose particles, etc., but from the viewpoint of improving the emulsion stability of the water-in-oil emulsion, the amount is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, even more preferably 300 parts by mass or more, even more preferably 400 parts by mass or more, per 100 parts by mass of the cellulose aqueous solution, and preferably 1000 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 600 parts by mass or less.

[0024] In step (B), from the viewpoint of improving the emulsion stability of the water-in-oil emulsion, it is preferable to further mix a surfactant together with the aqueous cellulose solution and the organic solvent. Examples of surfactants include nonionic surfactants, anionic surfactants, and cationic surfactants. Among these, nonionic surfactants are preferred from the viewpoint of further improving the emulsion stability of the water-in-oil emulsion.

[0025] Examples of nonionic surfactants include sorbitan fatty acid esters such as sorbitan monooleate, sorbitan monostearate, sorbitan sesquioleate, coconut oil sorbitan, sorbitan monopalmitate, sorbitan tristearate, and sorbitan trioleate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate; polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether; polyoxyethylene glycerin fatty acid esters such as polyoxyethylene glyceryl monooleate; polyoxyethylene sorbitol fatty acid esters such as polyoxyethylene sorbit tetraoleate; polyoxyethylene hydrogenated castor oil; polyglycerin fatty acid esters; sucrose fatty acid esters; and polyether-modified silicones. Among these, from the viewpoint of further improving the emulsion stability of the water-in-oil emulsion, at least one selected from polyoxyethylene alkyl ether, sorbitan fatty acid ester, sucrose fatty acid ester, and polyether-modified silicone is preferred, and at least one selected from polyoxyethylene lauryl ether and sorbitan monooleate is more preferred.

[0026] Examples of the anionic surfactant include alkylbenzene sulfonates such as sodium alkylbenzene sulfonate; alkyl sulfates such as sodium alkyl sulfate; and alkyl ether sulfates such as sodium alkyl ether sulfate. Examples of the cationic surfactant include alkyltrimethylammonium chloride and dialkyldimethylammonium chloride.

[0027] The surfactant may be added to at least one of the aqueous cellulose solution and the organic solvent before mixing, or may be added to the liquid after mixing the aqueous cellulose solution and the organic solvent, but it is preferable to dissolve the surfactant in the organic solvent before mixing.

[0028] When a surfactant is further mixed, the amount of surfactant added is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 1.0 part by mass or more, per 100 parts by mass of the organic solvent, from the viewpoint of improving the emulsion stability of the water-in-oil emulsion, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less.

[0029] The water-in-oil emulsion of cellulose is preferably prepared, for example, by adding an aqueous cellulose solution to an organic solvent in which a nonionic surfactant has been dissolved, and mixing the mixture with stirring. For example, a method of mixing and stirring the mixture using a mixer such as a high-speed emulsifying disperser at a temperature in the range of -20°C to 60°C can be mentioned. The higher the rotation speed during stirring, the smaller the diameter of the droplets formed. Therefore, the rotation speed of the mixer can be adjusted appropriately depending on the target particle size of cellulose.

[0030] <Process (C)> Step (C) is a step of mixing the water-in-oil emulsion with an alcohol having an octanol / water partition coefficient ClogP of 0.5 or more to precipitate cellulose and obtain cellulose particles. In this step, alcohol is mixed with a water-in-oil emulsion, and the water in the emulsion is replaced with the solvent, causing cellulose to precipitate and giving cellulose particles.

[0031] From the viewpoint of further increasing the sphericity of the resulting cellulose particles, the octanol / water partition coefficient ClogP of the alcohol is 0.5 or more, preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.8 or more; from the same viewpoint, it is preferably 4.0 or less, more preferably 3.5 or less, even more preferably 3.0 or less, even more preferably 2.5 or less, and even more preferably 2.3 or less. In this embodiment, when the alcohol is a mixed alcohol containing two or more kinds of alcohol, the octanol / water partition coefficient ClogP of the alcohol can be a weighted average value of the ClogP of each alcohol constituting the mixed alcohol. Furthermore, from the viewpoint of further increasing the sphericity of the resulting cellulose particles, the octanol / water partition coefficient ClogP of the organic solvent is preferably larger than the octanol / water partition coefficient ClogP of the alcohol, and [octanol / water partition coefficient ClogP of the organic solvent] - [octanol / water partition coefficient ClogP of the alcohol] is preferably 0.5 or more, more preferably 1.0 or more, and even more preferably 1.5 or more, and from the same viewpoint, it is preferably 4.5 or less, more preferably 4.0 or less, even more preferably 3.5 or less, and even more preferably 3.4 or less.

[0032] The solubility of the alcohol in water at 25°C is preferably 0.1 g / 100 mL or more, more preferably 0.3 g / 100 mL or more, and even more preferably 0.5 g / 100 mL or more, from the viewpoint of productivity of cellulose particles, and is preferably 100 g / 100 mL or less, more preferably 50 g / 100 mL or less, even more preferably 30 g / 100 mL or less, and even more preferably 20 g / 100 mL or less, from the viewpoint of further increasing the sphericity of the obtained cellulose particles.

[0033] The number of carbon atoms in the alcohol is preferably 4 or more, and preferably 8 or less, more preferably 7 or less, and even more preferably 6 or less, from the viewpoint of further increasing the sphericity of the resulting cellulose particles. Specifically, the alcohol preferably contains at least one selected from 1-butanol, 2-butanol, 2-methyl-1-propanol, 1-hexanol, and 1-pentanol.

[0034] In order to suppress aggregation of the resulting cellulose particles and further increase the sphericity, the amount of alcohol mixed is preferably 500 parts by mass or more, more preferably 700 parts by mass or more, even more preferably 900 parts by mass or more, and preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, even more preferably 1200 parts by mass or less, per 100 parts by mass of the water-in-oil emulsion.

[0035] In step (C), an acid may be further mixed. By further mixing an acid, the amount of alcohol used can be reduced. This is thought to be because mixing an acid can promote the expulsion of water from the emulsion. The acid may be an inorganic acid or an organic acid, and more specifically, it is preferable to include an organic acid, and it is preferable to include at least one selected from acetic acid, citric acid, malic acid, lactic acid, and succinic acid. In this case, it is desirable that the acid used is compatible with the alcohol. The amount of acid used is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 30 parts by mass or more, and preferably 70 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, relative to 100 parts by mass of alcohol. In the step (C), when an acid is further mixed, the alcohol and the acid may be mixed into the water-in-oil emulsion simultaneously or sequentially, but it is preferable to mix the alcohol and the acid simultaneously.

[0036] The alcohol and the water-in-oil emulsion are preferably mixed by, for example, adding the water-in-oil emulsion to the alcohol and stirring to mix. When adding the water-in-oil emulsion to the alcohol, it is preferable to add the water-in-oil emulsion while stirring the alcohol to prevent the droplets from bonding together. The temperature when mixing the alcohol and the water-in-oil emulsion is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 15°C or higher, and from the viewpoint of further increasing the sphericity, is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower.

[0037] The obtained cellulose particles can be separated and recovered using known methods such as centrifugation, filtration, decantation, drying, etc. The recovered cellulose particles may also be washed with water, alcohol, or the like. The resulting cellulose particles may be classified using a sieve or the like to adjust the particle size.

[0038] [Cellulose particles] The method for producing cellulose particles according to the present embodiment can produce cellulose particles with high sphericality. Furthermore, the method for producing cellulose particles according to the present embodiment does not require chemical modification of cellulose with acetyl groups or the like, and therefore can produce cellulose particles that do not have chemically modified groups. From the viewpoint of improving lubricity, the sphericity of the cellulose particles according to this embodiment is preferably 0.80 or more, more preferably 0.85 or more, even more preferably 0.88 or more, and even more preferably 0.90 or more. Since the higher the sphericity of the cellulose particles according to this embodiment, the better, the upper limit thereof is not particularly limited, but is, for example, 1.0 or less. In this embodiment, the sphericity of cellulose particles is the number-average value of the circularity of 50 randomly selected cellulose particles. The circularity of cellulose particles can be calculated from scanning electron microscope (SEM) images using, for example, image analysis particle size distribution measurement software Mac-View ver. 4.

[0039] The spheroid-equivalent mean diameter of the cellulose particles according to this embodiment is not particularly limited, as an appropriate range is selected depending on the application, but from the viewpoints of handleability and productivity, it is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 5 μm or more, and preferably 300 μm or less, more preferably 200 μm or less, even more preferably 100 μm or less, even more preferably 50 μm or less, even more preferably 30 μm or less, even more preferably 20 μm or less. The method for calculating the spheroid-equivalent mean diameter is as described above.

[0040] The pore volume of the cellulose particles according to this embodiment can be determined by mercury porosimetry as described in the Examples. From the viewpoint of preventing deformation due to compression and improving slipperiness, the pore volume of the cellulose particles according to this embodiment is preferably 0.3 mL / g or less, more preferably 0.2 mL / g or less, even more preferably 0.1 mL / g or less, and even more preferably 0.05 mL / g or less. Since the lower the pore volume of the cellulose particles according to this embodiment, the better, the lower limit is not particularly limited, but may be, for example, 0.0001 mL / g or more.

[0041] The cellulose particles according to this embodiment can be incorporated into or used in, for example, cosmetics, toiletries, oral care products, quasi-drugs, pharmaceuticals, household products, agricultural products, and the like. Furthermore, the cellulose particles according to this embodiment have high sphericity and excellent slipperiness, and therefore can be suitably used in cosmetics, toiletries, oral care products, quasi-drugs, and the like. Furthermore, since the cellulose particles according to this embodiment have a high degree of sphericity, they can be suitably used, for example, as fillers for various types of chromatography, polymer carriers, carriers for bioreactors, carriers for diagnostic reagents, carriers for purifying body fluids, etc. Furthermore, the cellulose particles according to this embodiment are made from cellulose derived from natural plants, and are therefore environmentally friendly and can be suitably used as an alternative material to microplastics.

[0042] In relation to the above-described embodiment, the present invention further discloses the following aspects. [1] A method for producing cellulose particles, comprising the steps of mixing a water-in-oil emulsion containing cellulose and preferably an organic solvent with an alcohol having an octanol / water partition coefficient ClogP of 0.5 or more, and precipitating the cellulose to obtain cellulose particles. [2] The method according to [1], wherein the octanol / water partition coefficient ClogP is 0.6 or more and 4.0 or less. [3] The method according to [1] or [2], wherein the octanol / water partition coefficient ClogP is 0.6 or more and 3.0 or less. [4] The method according to any one of [1] to [3], wherein the octanol / water partition coefficient ClogP is 0.7 or more and 2.5 or less. [5] The method according to any one of [1] to [4], wherein the octanol / water partition coefficient ClogP is 0.8 or more and 2.3 or less. [6] The manufacturing method according to any one of [1] to [5], comprising the following steps (A) to (C) in this order: Step (A): A step of mixing an alkaline aqueous solution with cellulose to obtain an aqueous cellulose solution in which the cellulose is dissolved in the alkaline aqueous solution. Step (B): A step of mixing the aqueous cellulose solution with an organic solvent to obtain the water-in-oil emulsion. Step (C): A step of mixing the water-in-oil emulsion with the alcohol to precipitate the cellulose and obtain the cellulose particles. [7] The method according to any one of [1] to [6], wherein [the octanol / water partition coefficient ClogP of the organic solvent] - [the octanol / water partition coefficient ClogP of the alcohol] is 4.5 or less. [8] The method according to any one of [1] to [7], wherein [the octanol / water partition coefficient ClogP of the organic solvent] - [the octanol / water partition coefficient ClogP of the alcohol] is 0.5 or more and 4.5 or less. [9] The method according to any one of [1] to [8], wherein [the octanol / water partition coefficient ClogP of the organic solvent] - [the octanol / water partition coefficient ClogP of the alcohol] is 1.0 or more and 4.0 or less.

[10] The method according to any one of [1] to [9], wherein [the octanol / water partition coefficient ClogP of the organic solvent] - [the octanol / water partition coefficient ClogP of the alcohol] is 1.5 or more and 3.4 or less.

[11] The method according to any one of [1] to

[10] , wherein the solubility of the alcohol in water at 25°C is 0.1 g / 100 mL or more and 100 g / 100 mL or less.

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

[11] , wherein the solubility of the alcohol in water at 25°C is 0.3 g / 100 mL or more and 30 g / 100 mL or less.

[13] The method according to any one of [1] to

[12] , wherein the solubility of the alcohol in water at 25°C is 0.5 g / 100 mL or more and 20 g / 100 mL or less.

[14] The method according to any one of [1] to

[13] , wherein the alcohol has 4 or more and 8 or less carbon atoms.

[15] The method according to any one of [1] to

[14] , wherein the alcohol has 4 or more and 7 or less carbon atoms.

[16] The method according to any one of [1] to

[15] , wherein the alcohol has 4 or more and 6 or less carbon atoms.

[17] The production method according to any one of [1] to

[16] , wherein the alcohol includes at least one selected from 1-butanol, 2-butanol, 2-methyl-1-propanol, 1-hexanol, and 1-pentanol.

[18] The method according to any one of [1] to

[17] , wherein the organic solvent has an octanol / water partition coefficient ClogP of 0.70 or more.

[19] The method according to any one of [1] to

[18] , wherein the organic solvent has an octanol / water partition coefficient ClogP of 1.0 or more and 6.0 or less.

[20] The method according to any one of [1] to

[19] , wherein the organic solvent has an octanol / water partition coefficient ClogP of 2.0 or more and 5.0 or less. [twenty one] The method according to any one of [1] to

[20] , wherein the organic solvent has an octanol / water partition coefficient ClogP of 3.0 or more and 4.5 or less. [twenty two] The method according to any one of [1] to

[21] , wherein the organic solvent contains at least one selected from hydrocarbons and esters, each of which may have a halogen atom. [twenty three] The method according to any one of [1] to

[22] , wherein the amount of the alcohol mixed is preferably 500 parts by mass or more and 2000 parts by mass or less relative to 100 parts by mass of the water-in-oil emulsion. [twenty four] The method according to any one of [1] to

[23] , wherein the amount of the alcohol mixed is preferably 700 parts by mass or more and 1500 parts by mass or less relative to 100 parts by mass of the water-in-oil emulsion. [twenty five] The method according to any one of [1] to

[24] , wherein the amount of the alcohol mixed is preferably 900 parts by mass or more and 1200 parts by mass or less relative to 100 parts by mass of the water-in-oil emulsion.

[26] The method according to any one of [1] to

[25] , wherein the sphericity of the cellulose particles is 0.80 or more.

[27] The method according to any one of [1] to

[26] , wherein the sphericity of the cellulose particles is 0.85 or more.

[28] The method according to any one of [1] to

[27] , wherein the sphericity of the cellulose particles is 0.90 or more.

[29] 8. The method for producing cellulose particles according to claim 1, wherein an acid is further mixed in the step (C).

[30] The method according to any one of [1] to

[29] , wherein the cellulose particles have a pore volume of 0.3 mL / g or less.

[31] The method according to any one of [1] to

[30] , wherein the cellulose particles have a pore volume of 0.1 mL / g or less.

[32] The method according to any one of [1] to

[31] , wherein the cellulose particles have a pore volume of 0.05 mL / g or less.

[33] Cellulose particles having a sphericity of 0.80 or more and a pore volume of 0.3 mL / g or less.

[34]

[33] Cellulose particles having a sphericity of 0.85 or more.

[35] The cellulose particles according to

[33] or

[34] , having a sphericity of 0.90 or more.

[36] The cellulose particles according to any one of

[33] to

[35] , having a pore volume of 0.1 mL / g or less.

[37] The cellulose particles according to any one of

[33] to

[36] , having a pore volume of 0.05 mL / g or less.

[38] The cellulose particles according to any one of

[33] to

[37] , having an average diameter equivalent to a circumference of 1 μm or more and 300 μm or less.

[39] The cellulose particles according to any one of

[33] to

[38] , having an average diameter equivalent to a circumference of 2 μm or more and 100 μm or less.

[40] The cellulose particles according to any one of

[33] to

[39] , having an average equivalent circumference diameter of 5 μm or more and 20 μm or less.

[41] The cellulose particles according to any one of

[33] to

[40] , which do not have a chemically modified group.

[42] The cellulose particles according to any one of

[33] to

[41] , obtained by the production method according to any one of [1] to

[32] . [Example]

[0043] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples in any way. Various physical properties were measured and evaluated by the following methods.

[0044] [Measurement method] (1) Scanning electron microscope (SEM) observation The dried cellulose particles were observed using an electron microscope (Keyence Corporation, VE-9800) to obtain SEM images.

[0045] (2) Measurement of sphericity Using image analysis particle size distribution measurement software Mac-View ver. 4, 50 cellulose particles were randomly selected from the obtained SEM images and the circularity of each was measured. The number average of the circularities of the 50 particles obtained was taken as the sphericity. The circularity was calculated using the following formula: Circularity = 4πS / L 2 where S is the area of ​​one cellulose particle in the SEM image, and L is the perimeter of one cellulose particle.

[0046] (3) Measurement of the average diameter of the oval Using image analysis particle size distribution measurement software Mac-View ver. 4, 50 particles were randomly selected from the obtained SEM image and the equivalent circumferential diameter of each was measured. The number average of the equivalent circumferential diameters of the 50 particles obtained was taken as the average equivalent circumferential diameter.

[0047] (4) Measurement of pore volume Evaluation was carried out using the mercury intrusion method using a mercury porosimeter (Auto Pore IV 9500) manufactured by Shimadzu Corporation. Approximately 0.05 g of powder sample was placed in a cell, and measurements were carried out at a measurement pressure range of 0.01 MPa to 210 MPa. In mercury intrusion, the measurement pressure (intrusion pressure) corresponds to the pore size, and the pore size distribution can be measured from the relationship between the measurement pressure and the amount of mercury intrusion. To evaluate the volume of intraparticle pores, the volume of pores with a diameter of 1 μm or less was evaluated.

[0048] [Production of cellulose particles] Example 1 (1) Process (A) The starting cellulose was cellulose powder (CEOLUS (registered trademark) PH-101, manufactured by Asahi Kasei Corporation, degree of polymerization: 170, average diameter equivalent to circumference: 50 μm). 10.6 g of the cellulose powder was added to 189.4 g of an aqueous solution with a 4% NaOH concentration by mass, and the mixture was cooled to −2°C. Subsequently, while maintaining the temperature at −2°C, 50 g of an aqueous solution with a 22% NaOH concentration by mass was added, and the mixture was quickly stirred with a spatula to dissolve the cellulose. The resulting aqueous cellulose solution had a cellulose concentration of 4% by mass and an NaOH concentration of 7.6% by mass.

[0049] (2) Process (B) 2.52 g of a nonionic surfactant (Emulgen 102KG, polyoxyethylene lauryl ether, manufactured by Kao Corporation) was added to 180 g of an organic solvent (n-hexane) and pre-stirred with a spatula. Next, 40 g of the cellulose aqueous solution obtained in step (A) was added, and the mixture was emulsified by stirring for 10 minutes at 20°C and 4,000 rpm using a homomixer MARK II 2.5 (manufactured by Primix Corporation) to obtain a water-in-oil emulsion of cellulose.

[0050] (3) Process (C) The emulsion obtained in step (B) was added to alcohol (1-butanol) for precipitating cellulose particles, and the cellulose particles were precipitated. Precipitation was performed using 500 g of alcohol for 50 g of emulsion. When adding the emulsion to the alcohol, the alcohol was stirred at 500 rpm using a stirrer. The temperature of the alcohol was set to room temperature (20°C). After the cellulose particles were precipitated, the resulting liquid was filtered under reduced pressure (700 hPa) using filter paper (Millipore OMNIPORE DISC PTFE PHILIC 1.0UM 90MM WH PLN 25 / PK, 1 μm mesh size). The residue after filtration was then dispersed in 300 g of pure water and neutralized to approximately pH 7.0 using a 50% aqueous lactic acid solution. The neutralized liquid was again filtered under reduced pressure and washed with pure water. The recovered powder was dried in a dryer (Yamato Scientific Co., Ltd., ADP300) at 70°C to obtain cellulose particles. The appearance of the obtained cellulose particles and an SEM image of their cross section are shown in Figure 1. The pore volume of the obtained cellulose particles was 0.0011 mL / g. The obtained cellulose particles were evaluated by the above-mentioned method, and the results are shown in Table 1.

[0051] Examples 2 to 9 and Comparative Examples 1 to 5 Cellulose particles were produced in the same manner as in Example 1, except that the conditions for steps (A) to (C) were changed to those shown in Table 1, and evaluated in the same manner as above. The results are shown in Table 1. In Table 1, SPAN80 is a surfactant (sorbitan monooleate) manufactured by Tokyo Chemical Industry Co., Ltd., Rheodor SP-O10V is a surfactant (sorbitan monooleate) manufactured by Kao Corporation, Modified Silicone KF-6048 is a surfactant (cetyl PEG / PPG-10 / 1 dimethicone, polyether-modified silicone surfactant) manufactured by Shin-Etsu Chemical Co., Ltd., and Sucrose Fatty Acid Ester ER-290 is a surfactant (sucrose erucate ester) manufactured by Mitsubishi Chemical Corporation. In Comparative Example 5, 1000 parts by mass of acetic acid was used instead of alcohol with respect to 100 parts by mass of the emulsion.

[0052] Example 10 In Example 10, cellulose particles were produced in the same manner as in Example 9, except that 40 parts by mass of acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used together with 1-butanol in step (C) per 100 parts by mass of 1-butanol, and evaluated by the above-mentioned method. The results are shown in Table 1.

[0053] [Table 1]

[0054] As can be seen from the results of the Examples and Comparative Examples, the production method of the present invention was able to produce cellulose granules with high sphericity. Furthermore, the production method of the present invention was simple and easy to use, as it allowed for large-scale processing in a liquid state.

Claims

1. A method for producing cellulose particles, comprising a step of mixing a water-in-oil emulsion containing cellulose with an alcohol having an octanol / water partition coefficient ClogP of 0.5 or more, and precipitating the cellulose to obtain cellulose particles, The method for producing cellulose particles, wherein the pore volume of the cellulose particles is 0.3 mL / g or less.

2. The method for producing cellulose particles according to claim 1, comprising the following steps (A) to (C) in this order: Step (A): A step of mixing an alkaline aqueous solution with cellulose to obtain an aqueous cellulose solution in which the cellulose is dissolved in the alkaline aqueous solution. Step (B): A step of mixing the aqueous cellulose solution with an organic solvent to obtain the water-in-oil emulsion. Step (C): A step of mixing the water-in-oil emulsion with the alcohol to precipitate the cellulose and obtain the cellulose particles.

3. [Octanol / water partition coefficient of organic solvent Clog P]-[Octanol / water partition coefficient of alcohol Clo The method for producing cellulose particles according to claim 2, wherein the [gP] is 4.5 or less.

4. The method for producing cellulose particles according to any one of claims 1 to 3, wherein the solubility of the alcohol in water at 25°C is 0.1 g / 100 mL or more and 100 g / 100 mL or less.

5. The method for producing cellulose particles according to any one of claims 1 to 4, wherein the alcohol has 4 to 8 carbon atoms.

6. The method for producing cellulose particles according to any one of claims 1 to 5, wherein the alcohol comprises at least one selected from the group consisting of 1-butanol, 2-butanol, 2-methyl-1-propanol, 1-hexanol, and 1-pentanol.

7. The method for producing cellulose particles according to claim 2, claim 3, or any one of claims 4 to 6 dependent on claim 2, wherein the organic solvent has an octanol / water partition coefficient ClogP of 0.70 or more.

8. The method for producing cellulose particles according to claim 2, claim 3, or any one of claims 4 to 7 dependent on claim 2, wherein the organic solvent contains at least one selected from hydrocarbons and esters, which may have a halogen atom.

9. The method for producing cellulose particles according to any one of claims 1 to 8, wherein the sphericity of the cellulose particles is 0.80 or more.

10. The method for producing cellulose particles according to any one of claims 1 to 9, wherein an acid is further mixed in the step (C).

11. Cellulose particles having a sphericity of 0.80 or more and a pore volume of 0.3 mL / g or less, Cellulose particles obtained by the method for producing cellulose particles according to any one of claims 1 to 10.

12. The cellulose particles according to claim 11, having an average equivalent circumference diameter of 1 μm or more and 300 μm or less.

13. 13. The cellulose particles according to claim 11 or 12, having a sphericity of 0.90 or more and a pore volume of 0.05 mL / g or less.

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