Composite cellulose particles

Abstract

The composite cellulose particles contain cellulose and a functional substance. The composite cellulose particles have a compressive elastic modulus of 50 MPa or less and an elastic recovery rate of less than 5%.

Description

Composite cellulose particles

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

[0002] It is known that functional polymer particles are used as additives in cosmetics to impart a soft feel (elasticity), a smooth feel, or sebum-trapping functionality. Many of these polymer particles contain synthetic polymers (microplastic beads) with a particle size of several micrometers. However, due to environmental considerations, the use of microplastic beads is expected to be restricted in the future.

[0003] Therefore, as particles that do not fall under the category of microplastic beads, polymer particles made of biodegradable natural polymer materials have attracted attention. One type of such polymer particles is cellulose particles. These cellulose particles are known to be incorporated into cosmetics to improve the skin feel due to their softness when the cosmetics are used, and to carry various functional substances to enable the functions of the functional substances to be exerted.

[0004] For example, Japanese Patent Laid-Open Publication No. 2001-323095 (Patent Document 1) discloses porous cellulose particles capable of carrying a functional substance, the particles having a particle size of 0.1 to 1.0 mm, a plurality of surface openings formed on a part or the entire outer surface, the maximum opening diameter of which is 1 / 10 to 1 / 3 of the particle size, and the surface openings being separated from adjacent surface openings by partitions having a thickness of 20 μm or less. It is described that the particles are easily deformed when swollen, can cause only moderate skin irritation, and that the presence of surface openings makes it easy to carry a functional substance. Japanese Patent Laid-Open Publication No. 2023-2552 (Patent Document 2) discloses a cellulose composite powder having an average particle size of 1 to 100 μm and a shear test value within a specified range, and that the powder has a good skin feel.

[0005] Japanese Patent Laid-Open No. 2007-56086 (Patent Document 3) discloses a pigment-containing cellulose powder in which a pigment is contained on the surface and inside of a cellulose powder in an amount ranging from 1 to 200% by mass of its own weight, and describes that the powder has light scattering properties, can exhibit a hiding effect, and can impart transparency and a soft feel to a coating film, creating a luxurious feel. Japanese Patent Laid-Open No. 2018-172578 (Patent Document 4) describes spherical organic-inorganic composite particles containing a silica component and a biodegradable plastic, which have an average particle diameter (d １ ) is 0.5 to 25 μm, and the true specific gravity is more than 1.0 to 2.0 g / cm ３ The document discloses organic-inorganic composite particles having a contact angle with water of 90° or less, which do not float on water even if released into the environment, are less likely to adsorb water-insoluble harmful chemical substances, and have good biodegradability, so there is no concern that they will cause environmental problems.

[0006] The present invention relates to the following: [1] Composite cellulose particles containing cellulose and a functional substance, wherein the composite cellulose particles have a compressive modulus of elasticity of 50 MPa or less and an elastic recovery rate of less than 5%. [2] A cosmetic preparation containing the composite cellulose particles described in [1] above. [3] A method for producing the composite cellulose particles described in [1] above, which comprises the following steps (1) to (4) in this order:Step (1): A step of mixing a water-in-oil cellulose emulsion containing cellulose, water, and an organic solvent with a cellulose non-solvent to precipitate coarse cellulose particles and obtain a suspension containing the coarse cellulose particles. Step (2): A step of subjecting the suspension containing the coarse cellulose particles obtained in step (1) to solid-liquid separation, and then washing the obtained coarse cellulose wet particles to obtain purified cellulose wet particles. Step (3): A step of obtaining carrier cellulose particles or a carrier cellulose particle dispersion by the following step (3-1) or step (3-2). Step (3-1): A step of drying the purified cellulose wet particles obtained in step (2) to obtain dried cellulose particles as carrier cellulose particles. Step (3-2): A step of mixing the purified cellulose wet particles obtained in step (2) with an azeotropic solvent having an azeotropic point with water, and distilling off the water contained in the purified cellulose wet particles by azeotropy to obtain a dehydrated cellulose particle dispersion in which dehydrated cellulose particles are dispersed in the azeotropic solvent as a carrier cellulose particle dispersion. Step (4): A step of obtaining composite cellulose particles by the following step (4-1) or step (4-2). Step (4-1): A step of mixing the carrier cellulose particles obtained in the step (3-1) with a functional substance dispersion liquid in which a functional substance is dispersed in an organic solvent or a functional substance solution in which a functional substance is dissolved in an organic solvent, and then removing the organic solvent to obtain composite cellulose particles containing the functional substance. Step (4-2): A step of obtaining composite cellulose particles by step (4-2a) or step (4-2b). Step (4-2a): A step of mixing the carrier cellulose particle dispersion liquid obtained in the step (3-2) with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2) to obtain composite cellulose particles containing the functional substance. Step (4-2b): A step of obtaining composite cellulose particles containing the functional substance by subjecting the carrier cellulose particle dispersion obtained in the step (3-2) to solid-liquid separation to obtain a cake, mixing the cake with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2) to obtain composite cellulose particles containing the functional substance. Detailed Description of the Invention

[0007] Such functional polymer particles contain functional substances to add specific functions. However, in order to effectively exhibit the functions of the functional substances, it is desirable that the functional polymer particles can sufficiently retain and encapsulate the functional substances and be stable without agglomeration. Furthermore, when the functional polymer particles are applied to an object, such as when a cosmetic containing the functional polymer particles is applied to the skin, it is desirable that a sufficient amount (appropriate amount) of the functional substance is released onto the object, such as the skin.

[0008] However, the porous cellulose particles described in Patent Document 1 have large surface pores with a maximum pore size of 1 / 10 to 1 / 3 of the particle size so that they can support functional substances with poor wettability, and the pore volumes of the porous cellulose particles disclosed in the examples are all 1 mL / g or less, which suggests that the encapsulation ability and encapsulation stability of functional substances are insufficient.Furthermore, the cellulose particles described in Patent Documents 2 to 4 are basically solid particles, which make it difficult to encapsulate functional substances, and further improvements are required in terms of the encapsulation stability and release ability of functional substances.

[0009] The present invention relates to composite cellulose particles that have good encapsulation stability of a functional substance and excellent release properties of the functional substance. The inventors have found that the above-mentioned problems can be solved by using composite cellulose particles that have a compressive modulus and elastic recovery rate within a predetermined range.

[0010] According to the present invention, it is possible to provide composite cellulose particles having good stability in encapsulating a functional substance and excellent release properties of the functional substance, and a method for producing the same.

[0011] [Composite Cellulose Particles] The composite cellulose particles of the present invention are composite cellulose particles containing cellulose and a functional substance, and the composite cellulose particles have a compressive modulus of 50 MPa or less and an elastic recovery rate of less than 5%. By having the above-described configuration, the composite cellulose particles of the present invention have good encapsulation stability of the functional substance in the composite cellulose particles and excellent release properties of the functional substance. The reason for this is unclear, but is thought to be as follows: By setting the compressive modulus of the composite cellulose particles to a predetermined value or less, the composite cellulose particles are easily deformed when pressure is applied to the composite cellulose particles. This ease of deformation is due to the structure of the cellulose constituting the composite cellulose particles and the physical properties of the functional substance present in the gaps between the cellulose. Furthermore, such composite cellulose particles are capable of stably retaining a relatively large amount of functional substance in the gaps between the cellulose, resulting in good encapsulation stability of the functional substance. Furthermore, as described above, the composite cellulose particles are easily deformed, and during this deformation, the functional substance held within the composite cellulose particles is efficiently released to the outside of the composite cellulose particles, which is thought to result in good release properties. Furthermore, by setting the elastic recovery rate of the composite cellulose particles to a predetermined value or less, the composite cellulose particles are less likely to recover to their original shape from the deformed shape after being deformed by pressure. Therefore, once the functional substance is released from the composite cellulose particles, the functional substance is prevented from returning to the inside of the composite cellulose particles, which is thought to result in good release properties of the functional substance.

[0012] <Cellulose> The cellulose contained in the composite cellulose particles of the present invention is not particularly limited as long as it is a known cellulose. The cellulose has the molecular formula (C ６ H １０ O ５ ) ｎand is a polymer formed by polymerizing β-glucose. From the viewpoint of environmental consideration, it is preferable that the cellulose contained in the composite cellulose particles has a small amount of substituents substituted on the hydroxy groups of the cellulose. The amount of substituents introduced to the hydroxy groups of the cellulose is preferably 0.5 mol % or less, more preferably 0.1 mol % or less, and even more preferably substantially 0 mol %, relative to the total hydroxy groups (the total of hydroxy groups and substituents introduced to the hydroxy groups). From the viewpoint of improving the content and release of functional substances, it is preferable that the cellulose contained in the composite cellulose particles does not have a crosslinked structure intentionally introduced by the composite.

[0013] From the viewpoint of improving the encapsulation stability and release of functional substances, the cellulose contained in the composite cellulose particles is preferably not cellulose I type crystalline cellulose but cellulose II type crystalline cellulose or amorphous cellulose. The crystalline form of the cellulose contained in the composite cellulose particles can be identified from the diffraction angle and diffraction intensity by X-ray diffraction. Cellulose II type crystalline cellulose exhibits a diffraction peak derived from the (110) plane at a diffraction angle 2θ = 12.5° and a diffraction peak derived from the (110) plane at 2θ = 20.0°, and can be easily distinguished from cellulose I type crystalline cellulose. Cellulose II type crystallinity is defined by the following formula, but the value is not particularly limited. Cellulose II type crystallinity (%) = [(I ２０．０ -I １５．０ ) / I ２０．０ ]×100 (where I ２０．０ is the diffraction intensity of the lattice plane (110 plane) (diffraction angle 2θ = 20.0°) in X-ray diffraction, and I １５．０ is the diffraction intensity of the amorphous portion (diffraction angle 2θ = 15.0°). The cellulose type II crystallinity can be measured by the X-ray diffraction method as described below. The X-ray diffraction intensity is measured using an X-ray diffractometer ("MiniFlex-II" manufactured by Rigaku Corporation) under the following conditions: X-ray source: Cu / Kα-radiation Measurement range: 2θ = 5 to 50° The measurement sample has an area of ​​320 mm ２The resulting mixture is compressed into pellets measuring 1 mm in diameter and 1 mm thick. The X-ray scan speed is 5° / min. The cellulose II type crystallinity of the cellulose contained in the composite cellulose particles can be adjusted, for example, by the type of solvent contained in the purified wet cellulose particles when the drying treatment in step (3-1) or the azeotropic solvent removal treatment in step (3-2) is carried out in the method for producing composite cellulose particles described below. Although the reason is unclear, the crystallinity increases when the drying treatment or the azeotropic solvent removal treatment is carried out when the purified wet cellulose particles contain an aqueous solvent, whereas the crystallinity decreases when the drying treatment or the azeotropic solvent removal treatment is carried out when the purified wet cellulose particles contain a non-aqueous solvent.

[0014] From the viewpoint of improving the encapsulation stability and release of the functional substance, it is preferable that the cellulose contained in the composite cellulose particles is particulate cellulose, preferably in part or in whole. Here, the particulate cellulose may be formed by a plurality of particulate celluloses via a functional substance, or may be formed by a single particulate cellulose alone. In the present invention, in the case of a composite cellulose particle formed by one or a plurality of particulate celluloses, in which a functional substance is contained in the particulate cellulose, the cellulose particles capable of carrying the functional substance are referred to as carrier cellulose particles. This carrier cellulose particle means one that is made of cellulose and does not contain a functional substance as a constituent. Furthermore, in the present invention, from the viewpoint of improving the release of the functional substance in cosmetics and the like containing the composite cellulose particles, it is preferable that the cellulose contained in the composite cellulose particles is formed by a single particulate cellulose alone. When a single particulate cellulose alone forms a composite cellulose particle, the composite cellulose particle of the present invention includes a form in which a functional substance is contained in the particulate cellulose (inside the carrier cellulose particle). That is, the composite cellulose particles of the present invention are preferably composite cellulose particles in which at least a portion of the functional substance is contained in carrier cellulose particles, and more preferably composite cellulose particles in which the carrier cellulose particles are porous cellulose particles and at least a portion of the functional substance is contained in the porous cellulose particles. The composite cellulose particles of the present invention may have all of the functional substance contained in the carrier cellulose particles, or may have a portion of the functional substance contained in the carrier cellulose particles with the remainder attached to the outer surface of the carrier cellulose particles. Here, in the present invention, from the viewpoint of improving the release of the functional substance in cosmetics and the like containing the composite cellulose particles, it is preferable that the composite cellulose particles of the present invention have a form in which all of the functional substance contained therein is contained inside the carrier cellulose particles.

[0015] Furthermore, in the present invention, when one particulate cellulose forms a composite cellulose particle, it is also referred to as the particulate cellulose forming a composite cellulose mother particle. In the present invention, when particulate cellulose forms a composite cellulose mother particle, it is preferable that the diameter of the particulate cellulose in the range of its existence is approximately equal to the particle diameter of the composite cellulose particle. In the present invention, the phrase "the diameter of the particulate cellulose in the range of its existence is approximately equal to the particle diameter of the composite cellulose particle" specifically means that the diameter of the particulate cellulose in the range of its existence, i.e., the ratio of the median diameter of the composite cellulose particle to the median diameter of the particulate cellulose, is preferably 0.5 or more and 2 or less, more preferably 0.6 or more and 1.9 or less, and even more preferably 0.65 or more and 1.8 or less, from the viewpoint of improving the encapsulation stability and release of the functional substance. More specifically, when the functional substance contained in the composite cellulose particles is an organic liquid or solid, the diameter of the range in which the particulate cellulose exists, i.e., the ratio of the median diameter of the composite cellulose particles to the median diameter of the particulate cellulose, is preferably 0.5 to 2, more preferably 0.6 to 1.9, and even more preferably 0.65 to 1.8, from the viewpoint of improving the encapsulation stability and release of the functional substance. When some or all of the cellulose contained in the composite cellulose particles of the present invention is particulate cellulose, the presence of many voids between or within the particulate cellulose not only enables the functional substance to be stably retained in the voids, but also allows the compressive modulus of the composite cellulose particles to be set to a predetermined value or less, thereby improving the release of the functional substance. In the present invention, from the viewpoint of enabling the functional substance to be stably retained and from the viewpoint of good release of the functional substance, the particulate cellulose is preferably a porous cellulose particle having many pores within the particulate cellulose, and more preferably, one porous cellulose particle alone forms one composite cellulose particle.Porous cellulose particles having a large number of pores inside the particulate cellulose are preferred because they can retain functional substances within the pores, and when external pressure, frictional force, etc. are applied to the composite cellulose particles, at least a portion of the functional substances retained in the pores can be released to the outside of the particles through openings on the surface of the composite cellulose particles that are connected to the pores. Furthermore, when the particulate cellulose particles are porous cellulose particles and a single particulate cellulose forms a composite cellulose particle by itself, when external pressure, frictional force, etc. are repeatedly applied to the composite cellulose particles, the functional substances retained near the surface of the composite cellulose particles can be released by the initial application of pressure or frictional force, and the functional substances retained further inside can be released by the later application of pressure or frictional force. In this case, the composite cellulose particles of the present invention also have sustained release properties, which gradually release the functional substances, and are therefore preferred.

[0016] <Functional Substance> The functional substance constituting the composite cellulose particles of the present invention is not particularly limited as long as it is a known functional substance. The functional substance may be, for example, incorporated into cosmetics or the like, and released to the outside of the composite cellulose particles by the application operation when applied to an object, and be able to exert its function. Either organic or inorganic substances can be used as the functional substance, and can be appropriately selected depending on the function to be imparted. Specific examples of functional substances include oils such as moisturizers, fragrances, fragrance precursors, light scattering agents, ultraviolet absorbers, pigments, dyes, coloring agents, fluorescent brighteners, antioxidants, antibacterial agents, preservatives, cooling agents, warming agents, fertilizers, insecticides, insect repellents, etc.

[0017] When the functional substance is an organic substance, from the viewpoint of ease of incorporation, the functional substance is preferably one or more selected from the group consisting of silicone, fatty acid, ester oil, alcohol, nonionic polymer, organic acid having 8 or less carbon atoms, and chroman derivative, more preferably one or more selected from the group consisting of silicone, fatty acid, ester oil, alcohol, and chroman derivative, and even more preferably one or more selected from the group consisting of silicone, fatty acid, and chroman derivative. In the present invention, silicone as a functional substance is considered to be an organic substance.

[0018] Silicones are water-insoluble compounds whose main chain consists of a repeating structure of silicon and oxygen atoms, and when they are incorporated into cosmetics and applied to the skin, they provide a sustained smooth feel and form a film on the skin surface, reducing irritation from the external environment. Examples of silicones used here include polydimethylsiloxane, polysiloxane, and modified polysiloxane.

[0019] Fatty acids have a carboxy group at the end of a hydrocarbon structure and are incorporated as oily components into cosmetics and the like. Fatty acids may be saturated or unsaturated. The number of carbon atoms in the fatty acids used here is preferably 6 or more, more preferably 8 or more, even more preferably 10 or more, and even more preferably 12 or more, and is preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less. Specific examples of fatty acids include palm kernel oil fatty acid, lauric acid, palmitic acid, stearic acid, myristic acid, oleic acid, behenic acid, eicosapentaenoic acid, docosahexaenoic acid, and isostearic acid.

[0020] Ester oils are esterified products made from fatty acids and alcohols, and are used in cosmetics and the like as low-viscosity oily bases or emollients that suppress moisture evaporation from the skin, maintain moisture, and soften the skin. Examples of ester oils include synthetic ester oils and natural fats and oils. The number of carbon atoms in the fatty acid used as a raw material is preferably 4 or more, more preferably 8 or more, even more preferably 10 or more, and even more preferably 12 or more, and is preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less. The number of carbon atoms in the fatty acid is preferably 4 or more and 22 or less, more preferably 8 or more and 20 or less, even more preferably 10 or more and 18 or less, and even more preferably 12 or more and 18 or less. The number of carbon atoms in the alcohol used as a raw material is preferably 1 or more, more preferably 3 or more, and is preferably 22 or less, more preferably 20 or less, even more preferably 18 or less, even more preferably 14 or less, even more preferably 10 or less, and even more preferably 6 or less. Specific examples of ester oils include isopropyl myristate, octyldodecyl myristate, myristyl myristate, isopropyl palmitate, 2-ethylhexyl stearate, butyl stearate, stearyl stearate, cholesteryl isostearate, cetyl 2-ethylhexanoate, glyceryl tri-2-ethylhexanoate, and isotridecyl isononanoate.

[0021] The alcohol is a compound having a hydroxyl group, and either a monohydric alcohol or a polyhydric alcohol can be used. The monohydric alcohol is a component that forms a lamellar liquid crystal structure outside the oil droplets together with a nonionic surfactant in an oil-in-water emulsion, stabilizing the emulsion. The number of carbon atoms in the monohydric alcohol is preferably 6 or more, more preferably 8 or more, even more preferably 10 or more, and preferably 24 or less, more preferably 22 or less, even more preferably 20 or less. Specific examples of the monohydric alcohol include behenyl alcohol, cetearyl alcohol, stearyl alcohol, isostearyl alcohol, cholesterol, jojoba alcohol, and L-menthol.

[0022] Polyhydric alcohols are alcohols (polyols) having two or more hydroxyl groups, and are components that maintain the viscosity of cosmetics and the like, while adjusting the moisturizing properties on the skin and the feel when used. The number of carbon atoms in the polyhydric alcohol is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, still more preferably 6 or more, and even more preferably 8 or more, and is preferably 12 or less, more preferably 10 or less. Specific examples of polyhydric alcohols include sugar alcohols such as polyethylene glycol, polypropylene glycol, dipropylene glycol, 1,3-butylene glycol, glycerin, xylitol, and sorbitol.

[0023] Nonionic polymers are components that adjust the moisturizing properties and usability of the skin. They are incorporated as emulsifiers into cosmetics and the like to improve the water vapor barrier properties and usability in low-humidity environments, and examples of such components include cellulose derivatives such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, and hydroxypropylmethyl cellulose. These cellulose derivatives differ from the celluloses described above, and the degree of substitution of the cellulose derivatives (i.e., the ratio of the amount of substituents introduced into hydroxy groups to the total hydroxy groups of the original cellulose (the sum of hydroxy groups and substituents introduced into hydroxy groups)) is preferably greater than 0.5 mol%, more preferably 1 mol% or greater, from the viewpoint of solubility in solvents.

[0024] Organic acids having 8 or less carbon atoms are components that have the effects of increasing the moisture retention capacity of the skin, increasing flexibility, promoting the adhesion and detachment of stratum corneum cells, and expelling unnecessary stratum corneum. The number of carbon atoms in these organic acids is 8 or less, preferably 7 or less, more preferably 6 or less, even more preferably 5 or less, and also preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. Specific examples of organic acids having 8 or less carbon atoms include butyric acid, lactic acid, citric acid, malic acid, succinic acid, malonic acid, tartaric acid, salicylic acid, etc. Note that organic acids having 8 or less carbon atoms do not include the aforementioned fatty acids.

[0025] The chroman derivative has the molecular formula C ９ H １０It is a compound having a heterocyclic structure (chroman structure) of O, and is a component having antioxidant activity, etc. Examples of chroman derivatives include tocopherol acetate, etc. Tocopherol acetate has vitamin E-like activity.

[0026] The functional substance may also be one or more selected from the group consisting of vitamins and vitamin derivatives. The vitamin or vitamin derivative may be any known compound without any particular limitation, and is preferably vitamin A, vitamin C, vitamin E, or derivatives thereof.

[0027] In addition, when the functional substance is an organic substance, dissolving it and complexing it with cellulose as described below can preferably increase the content of the functional substance in the complexed cellulose particles. The solubility parameter (SP value) of the functional substance can be used as an indicator of solubility in an organic solvent. In this specification, the solubility parameter (SP value) is a value calculated by inputting the SMILES of the functional substance using the Hansen Solubility Parameter software "Hansen Solubility Parameter in Practice (HSPiP 4th Edition 4.1.07)." The SP value of multiple organic substances is calculated as a weighted average of the SP values ​​of each organic substance, with the volume of each organic substance being used as a weight when each organic substance dissolves. The solubility parameter (SP value) of the functional substance used in the present invention is preferably 10 MPa or less from the viewpoints of solubility in an organic solvent, improving the encapsulation stability and release of the functional substance, and the deformability of the complexed cellulose particles. １／２ and preferably 40 MPa or more. １／２ or less, more preferably 38 MPa １／２ More preferably, 36 MPa or less １／２ From the same viewpoint, the solubility parameter (SP value) of the functional substance is preferably 10 MPa or less. １／２ More than 40 MPa １／２ Less than 10 MPa, more preferably １／２ 38MPa or more １／２ More preferably, 10 MPa or less １／２ Over 36 MPa １／２The following is the result.

[0028] When the functional substance is an inorganic substance, the functional substance is preferably one or more selected from the group consisting of zinc oxide, titanium oxide, barium sulfate, calcium carbonate, talc, mica, and titanium oxide-coated mica from the viewpoint of ease of incorporation. Furthermore, the functional substance is preferably one or more selected from the group consisting of zinc oxide and titanium oxide, more preferably zinc oxide, from the viewpoint of improving the feel of the composition.

[0029] Zinc oxide and titanium oxide are used as white pigments with high covering power. Furthermore, zinc oxide has a sebum-absorbing effect, which prevents shine and makeup from coming off due to sebum. Talc and mica are used as extender pigments to adjust the feel of the skin, such as spreadability and lubricity, and to improve physical properties such as adhesion and gloss. Titanium oxide-coated mica is also used as a pearlescent pigment, which produces various interference colors and imparts a glossy appearance.

[0030] When the functional substance contained in the composite cellulose particles of the present invention is insoluble in an organic solvent or an azeotropic solvent and is particulate, the average particle size (average dispersion diameter) of the particulate functional substance is preferably less than 400 nm, more preferably 350 nm or less, even more preferably 250 nm or less, and even more preferably 200 nm or less from the viewpoint of improving the encapsulation stability and release properties of the functional substance, and is preferably 20 nm or more, more preferably 50 nm or more, even more preferably 80 nm or more, and even more preferably 100 nm or more from the viewpoint of ease of handling.The average particle size of the particulate functional substance is, from the same viewpoint, preferably 20 nm or more but less than 400 nm, more preferably 50 nm or more but 350 nm, even more preferably 80 nm or more but 350 nm, even more preferably 100 nm or more but 350 nm, even more preferably 100 nm or more but 250 nm, and even more preferably 100 nm or more but 200 nm. The average particle size (average dispersion diameter) of this particulate functional material is a hydrodynamic diameter measured by a dynamic light scattering measuring device and is expressed as a volume average diameter. Specifically, it can be measured by the method described in the Examples.

[0031] <Characteristics of composite cellulose particles> From the viewpoint of improving the encapsulation stability and release property of the functional substance, the compressive modulus of the composite cellulose particles is 50 MPa or less, preferably 40 MPa or less, more preferably 30 MPa or less, even more preferably 20 MPa or less, still more preferably 10 MPa or less, still more preferably 8.0 MPa or less, still more preferably 7.5 MPa or less, still more preferably 7.1 MPa or less, still more preferably 6.5 MPa or less, and still more preferably 6.0 MPa or less. Furthermore, from the viewpoint of suppressing disintegration during the production process of the composite cellulose particles, the compressive modulus of the composite cellulose particles is preferably 0.9 MPa or more, more preferably 1.5 MPa or more, even more preferably 1.9 MPa or more, still more preferably 2.1 MPa or more, and still more preferably 2.3 MPa or more. From the same viewpoint, the compressive modulus of the composite cellulose particles is preferably 0.9 MPa to 50 MPa, more preferably 0.9 MPa to 40 MPa, even more preferably 0.9 MPa to 30 MPa, still more preferably 0.9 MPa to 20 MPa, still more preferably 1.5 MPa to 10 MPa, still more preferably 1.5 MPa to 8.0 MPa, still more preferably 1.9 MPa to 7.5 MPa, still more preferably 2.1 MPa to 7.1 MPa, still more preferably 2.1 MPa to 6.5 MPa, and still more preferably 2.3 MPa to 6.0 MPa. When the functional substance is an organic substance, the compressive modulus of the composite cellulose particles is more preferably in the above range. When the functional substance is an inorganic substance, the compressive modulus of the composite cellulose particles is 50 MPa or less, preferably 48 MPa or less, and more preferably 46 MPa or less, from the viewpoint of improving the encapsulation stability and release property of the functional substance, and is preferably 5 MPa or more, more preferably 10 MPa or more, and even more preferably 14 MPa or more, from the viewpoint of suppressing disintegration during the manufacturing process of the composite cellulose particles.

[0032] The compressive modulus is the apparent compressive modulus of a single particle measured using a microcompression tester, and can be measured specifically by the method described in the Examples. The compressive modulus of the composite cellulose particles can be adjusted, for example, in the method for producing composite cellulose particles described below, by changing the type of carrier cellulose particles used for composite formation (the dried cellulose particles used in step (4-1) or the dehydrated cellulose particles used in step (4-2)) and the type and / or content of the functional substance.

[0033] From the viewpoint of improving the release of the functional substance, the elastic recovery of the composite cellulose particles is less than 5%, preferably 4.8% or less, more preferably 4.6% or less, and from the same viewpoint, 0% or more, preferably 0.2% or more, more preferably 0.4% or more, even more preferably 0.6% or more, and even more preferably 0.8% or more. From the same viewpoint, the elastic recovery of the composite cellulose particles is 0% or more but less than 5%, preferably 0.2% or more and 4.8% or less, more preferably 0.4% or more and 4.8% or less, even more preferably 0.6% or more and 4.8% or less, and even more preferably 0.8% or more and 4.8% or less. When the functional substance is an organic substance, the elastic recovery of the composite cellulose particles is more preferably within the above range. When the functional substance is an inorganic substance, the elastic recovery of the composite cellulose particles is, from the viewpoint of improving the release of the functional substance, less than 5%, preferably 4.8% or less, more preferably 4.6% or less, and from the same viewpoint, preferably 0.4% or more, more preferably 0.6% or more, even more preferably 0.8% or more, and even more preferably 1.0% or more. From the same viewpoint, the elastic recovery of the composite cellulose particles is, from the same viewpoint, 0.4% or more but less than 5%, preferably 0.6% or more and 4.8% or less, more preferably 0.8% or more and 4.6% or less, and even more preferably 1.0% or more and 4.6% or less.

[0034] The elastic recovery rate is the elastic recovery rate measured using a microcompression tester, and specifically can be measured by the method described in the Examples. The elastic recovery rate of the composite cellulose particles can be adjusted, for example, by changing the type and / or content of the functional substance in step (4) of the method for producing composite cellulose particles described below.

[0035] The median diameter of the composite cellulose particles (D ５０ From the viewpoint of improving the encapsulation stability and release of the functional substance, the diameter of the composite cellulose particles is preferably 2000 μm or less, more preferably 400 μm or less, even more preferably 250 μm or less, still more preferably 200 μm or less, still more preferably 150 μm or less, still more preferably 120 μm or less, still more preferably 110 μm or less, still more preferably 100 μm or less, and still more preferably less than 100 μm. From the viewpoint of improving the release of the functional substance, the median diameter of the composite cellulose particles is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 15 μm or more. From the same viewpoint, the median diameter of the composite cellulose particles is preferably 5 μm or more and 2000 μm or less, more preferably 5 μm or more and 400 μm or less, even more preferably 5 μm or more and 250 μm or less, still more preferably 5 μm or more and 200 μm or less, still more preferably 5 μm or more and 150 μm or less, still more preferably 5 μm or more and 120 μm or less, still more preferably 10 μm or more and 110 μm or less, still more preferably 15 μm or more and 100 μm or less, and still more preferably 15 μm or more and less than 100 μm.

[0036] When the functional substance contained in the composite cellulose particles is an organic substance, the median diameter (D ５０) is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, even more preferably 120 μm or less, even more preferably 110 μm or less, even more preferably 100 μm or less, and even more preferably less than 100 μm, from the viewpoint of improving the encapsulation stability and release of the functional substance. Furthermore, the median diameter of the composite cellulose particles is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, from the viewpoint of improving the release of the functional substance. Furthermore, from the same viewpoint, the median diameter of the composite cellulose particles is preferably 5 μm or more and 250 μm or less, more preferably 5 μm or more and 200 μm or less, even more preferably 5 μm or more and 150 μm or less, even more preferably 5 μm or more and 120 μm or less, even more preferably 10 μm or more and 110 μm or less, even more preferably 15 μm or more and 100 μm or less, and even more preferably 15 μm or more and 100 μm or less. When the functional substance contained in the composite cellulose particles is an inorganic substance, the median diameter (D ５０ ) is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, even more preferably 120 μm or less, even more preferably 110 μm or less, even more preferably 100 μm or less, and even more preferably less than 100 μm, from the viewpoint of improving the encapsulation stability and release of the functional substance. Furthermore, the median diameter of the composite cellulose particles is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, from the viewpoint of improving the release of the functional substance. Furthermore, from the same viewpoint, the median diameter of the composite cellulose particles is preferably 5 μm or more and 250 μm or less, more preferably 5 μm or more and 200 μm or less, even more preferably 5 μm or more and 150 μm or less, even more preferably 5 μm or more and 120 μm or less, even more preferably 10 μm or more and 110 μm or less, even more preferably 15 μm or more and 100 μm or less, and even more preferably 15 μm or more and 100 μm or less.

[0037] Here, the median diameter (D ５０) is the median diameter measured using a dynamic image analyzer, and can be measured specifically by the method described in the Examples. The median diameter of the composite cellulose particles can be adjusted, for example, by changing the stirring speed when mixing the aqueous cellulose solution with the organic solvent when preparing the cellulose emulsion used in step (1) in the method for producing composite cellulose particles described below. Specifically, by increasing the stirring speed when mixing the aqueous cellulose solution with the organic solvent in step (1), the emulsion droplet diameter of the resulting cellulose emulsion becomes smaller, resulting in cellulose particles with a small median diameter. Furthermore, by decreasing the stirring speed, the emulsion droplet diameter of the resulting cellulose emulsion becomes larger, resulting in cellulose particles with a large median diameter. Furthermore, the median diameter can be adjusted by changing the content of the functional substance in step (4) of the method for producing composite cellulose particles described below. Specifically, by increasing the content of the functional substance, the voids in the carrier cellulose particles are filled and the particles are less likely to shrink when the organic solvent or azeotropic solvent dries, making it easier for the median diameter of the resulting composite cellulose particles to maintain the median diameter of the carrier cellulose particles; by reducing the content of the functional substance, the voids in the carrier cellulose particles are not filled and the particles are more likely to shrink when the organic solvent or azeotropic solvent dries, making it easier for the median diameter of the resulting composite cellulose particles to decrease.

[0038] The content of the functional substance in the composite cellulose particles is, from the viewpoint of improving the release properties of the functional substance and improving the deformability of the composite cellulose particles, preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, even more preferably 70 parts by mass or more, even more preferably 100 parts by mass or more, even more preferably 150 parts by mass or more, even more preferably 200 parts by mass or more, and even more preferably 250 parts by mass or more, per 100 parts by mass of cellulose; and, from the viewpoint of improving the encapsulation stability of the functional substance, is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 450 parts by mass or less, and even more preferably 400 parts by mass or less. From the same viewpoint, the content of the functional substance is preferably 10 to 600 parts by mass, more preferably 30 to 500 parts by mass, even more preferably 50 to 450 parts by mass, still more preferably 70 to 400 parts by mass, still more preferably 100 to 400 parts by mass, still more preferably 150 to 400 parts by mass, still more preferably 200 to 400 parts by mass, and still more preferably 250 to 400 parts by mass. When the cellulose includes particulate cellulose, the preferred aspects of the content of the functional substance in the composite cellulose particles are the same as those described above.

[0039] In the method for producing composite cellulose particles described below, when the functional substance is composited in step (4), the upper limit of the amount of functional substance that can be contained in the composite cellulose particles varies depending on whether the functional substance is dissolved in an organic solvent or an azeotropic solvent and then composited, or whether the functional substance is dispersed in an organic solvent or an azeotropic solvent and then composited.

[0040] In the method for producing composite cellulose particles described below, when a functional substance is dissolved in the composite treatment in step (4), the solution in which the functional substance is dissolved easily penetrates into the interior of the carrier cellulose particles, making it possible to incorporate a relatively large amount of functional substance into the carrier cellulose particles. In this case, the content of the functional substance is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, even more preferably 200 parts by mass or more, and even more preferably 250 parts by mass or more, relative to 100 parts by mass of cellulose, from the viewpoint of improving the release of the functional substance and the deformability of the composite cellulose particles; and from the viewpoint of improving the encapsulation stability of the functional substance, it is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 450 parts by mass or less, and even more preferably 400 parts by mass or less. From the same viewpoint, the content of the functional substance is preferably 100 parts by mass or more and 600 parts by mass or less, more preferably 100 parts by mass or more and 500 parts by mass or less, even more preferably 150 parts by mass or more and 500 parts by mass or less, even more preferably 200 parts by mass or more and 450 parts by mass or less, and even more preferably 250 parts by mass or more and 400 parts by mass or less, per 100 parts by mass of cellulose.

[0041] On the other hand, in the method for producing composite cellulose particles described below, when a functional substance is dispersed and composited in step (4), the particulate functional substance is passed through the surface pores of the carrier cellulose particles and diffused into the interior of the cellulose particles, resulting in a smaller amount of functional substance contained in the carrier cellulose particles than in the case of dissolution. In this case, the content of the functional substance is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, relative to 100 parts by mass of cellulose, from the viewpoint of improving the release of the functional substance and the deformability of the composite cellulose particles; and from the viewpoint of improving the deformability of the composite cellulose particles and the encapsulation stability of the functional substance, it is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less. From the same viewpoint, the content of the functional substance is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 80 parts by mass or less, even more preferably 20 parts by mass or more and 60 parts by mass or less, and even more preferably 25 parts by mass or more and 50 parts by mass or less, per 100 parts by mass of cellulose.

[0042] <Carrier Cellulose Particles> When the composite cellulose particles of the present invention contain a functional substance and particulate cellulose, the particulate cellulose particles, i.e., the carrier cellulose particles, are preferably not coated with a surface treatment agent from the viewpoint of environmental consideration. The carrier cellulose particles can be produced, for example, by carrying out steps (1) to (3) in the method for producing composite cellulose particles described below.

[0043] These carrier cellulose particles can be formed into porous particles, for example, by selecting a cellulose non-solvent to be used when precipitating crude cellulose in step (1) in the method for producing composite cellulose particles described below, and the desired pores can be obtained by selecting this cellulose non-solvent.

[0044] The surface pore diameter of the carrier cellulose particles is not particularly limited, but from the viewpoint of improving the encapsulation stability and release property of the functional substance, the surface pore diameter is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more. From the viewpoint of maintaining the particle shape of the composite cellulose particles, the surface pore diameter is preferably 800 nm or less, more preferably 700 nm or less, and even more preferably 600 nm or less. From the same viewpoint, the surface pore diameter of the carrier cellulose particles is preferably 50 nm or more and 800 nm or less, more preferably 100 nm or more and 700 nm or less, even more preferably 200 nm or more and 700 nm or less, and even more preferably 200 nm or more and 600 nm or less. The surface pore diameter can be determined by mercury intrusion porosimetry, and specifically can be measured by the method described in the Examples.

[0045] The pore volume of the carrier cellulose particles is preferably 1.5 mL / g or more, more preferably 2.0 mL / g or more, even more preferably 2.3 mL / g or more, and even more preferably 2.4 mL / g or more from the viewpoint of improving the encapsulation stability and release of the functional substance. Also, from the viewpoint of suppressing disintegration during the production process of the composite cellulose particles, it is preferably 8.0 mL / g or less, more preferably 7.0 mL / g or less, even more preferably 6.0 mL / g or less, still more preferably 5.0 mL / g or less, and even more preferably 4.0 mL / g. From the same viewpoint, the pore volume of the carrier cellulose particles is preferably 1.5 mL / g to 8.0 mL / g, more preferably 1.5 mL / g to 7.0 mL / g, even more preferably 1.5 mL / g to 6.0 mL / g, still more preferably 2.0 mL / g to 5.0 mL / g, even more preferably 2.0 mL / g to 4.0 mL / g, still more preferably 2.3 mL / g to 4.0 mL / g, and even more preferably 2.4 mL / g to 4.0 mL / g. The pore volume is determined by dividing the total volume of mercury that has penetrated into the pores and interparticle gaps of the carrier cellulose particles by the mass of the particles and normalizing the result. Specifically, it can be measured by the method described in the Examples. The pore volume of the carrier cellulose particles can be adjusted, for example, by the surface tension of the dispersion medium (organic solvent) used in the dispersion medium substitution performed as necessary in step (3-1) or the azeotropic solvent used in step (3-2) in the method for producing composite cellulose particles described below, the drying method in step (3-1), and the emulsion droplet size of the cellulose emulsion used in step (1). Specifically, if the emulsion droplet size of the cellulose emulsion is small, the median diameter and pore volume of the obtained carrier cellulose particles will also be small.

[0046] The specific surface area of ​​the carrier cellulose particles is set to 85 m from the viewpoint of improving the stability of the inclusion of functional substances. ２ / g or more, preferably 90m ２ / g or more, more preferably 95m ２ / g or more, more preferably 100m ２ / g or more, and even more preferably 103m ２ / g or more. In addition, from the viewpoint of suppressing the collapse of the carrier cellulose particles during the manufacturing process, ２ / g, preferably less than 200m ２ / g or less, more preferably 180m ２ / g or less, more preferably 150m ２ / g or less, and even more preferably 140m ２ / g or less, and even more preferably 135m ２ From the same viewpoint, the specific surface area of ​​the carrier cellulose particles is 85 m ２ / g or more 500m ２ / g, preferably less than 90m ２ / g or more 200m ２ / g or less, more preferably 95m ２ / g or more 180m ２ / g or less, more preferably 100m ２ / g or more 150m ２ / g or less, and even more preferably 100m ２ / g or more 140m ２ / g or less, and even more preferably 103m ２ / g or more 135m ２ / g or less. The specific surface area is determined by dividing the sum of the surface areas of the internal microsurfaces and particle surfaces of the cellulose carrier particles, as measured by mercury intrusion porosimetry, by the mass of the particles and then normalizing the result. Specifically, it can be measured by the method described in the Examples. The specific surface area of ​​the cellulose carrier particles can be controlled, for example, in the method for producing composite cellulose particles described below, by selecting the surface tension of the dispersion medium (organic solvent) used for the dispersion medium substitution, which is performed as necessary in step (3-1), or the azeotropic solvent used in the azeotropic distillation in step (3-2), and the drying method in step (3-1). Specifically, if the surface tension of the dispersion medium used in step (3-1) or the azeotropic solvent used in step (3-2) is low, the capillary force associated with their evaporation is small, and shrinkage of the cellulose particles during drying can be suppressed, thereby obtaining cellulose carrier particles with a large specific surface area. Furthermore, in step (3-1), even by a drying method that does not involve capillary force due to the surface tension of the organic solvent, such as freeze-drying, shrinkage of the cellulose particles during drying can be suppressed, and cellulose carrier particles with a large specific surface area can be obtained.

[0047] From the viewpoint of improving the encapsulation stability and release of the functional substance, the compressive modulus of the carrier cellulose particles is 50 MPa or less, preferably 40 MPa or less, more preferably 30 MPa or less, even more preferably 20 MPa or less, still more preferably 10 MPa or less, still more preferably 7.0 MPa or less, still more preferably 6.0 MPa or less, still more preferably 5.3 MPa or less, still more preferably 5.2 MPa or less, and still more preferably 5.0 MPa or less. Furthermore, from the viewpoint of suppressing disintegration during the production process of the carrier cellulose particles, it is preferably 0.5 MPa or more, more preferably 0.9 MPa or more, still more preferably 2.0 MPa or more, still more preferably 2.5 MPa or more, still more preferably 2.8 MPa or more, and still more preferably 3.0 MPa or more. From the same viewpoint, the compressive modulus of the composite cellulose particles is preferably 0.5 MPa or more and 50 MPa or less, more preferably 0.5 MPa or more and 40 MPa or less, even more preferably 0.5 MPa or more and 30 MPa or less, even more preferably 0.5 MPa or more and 20 MPa or less, even more preferably 0.5 MPa or more and 10 MPa or less, even more preferably 0.5 MPa or more and 7.0 MPa or less, even more preferably 0.5 MPa or more and 5.0 MPa or less, even more preferably 0.9 MPa or more and 5.0 MPa or less, even more preferably 2.0 MPa or more and 5.0 MPa or less, even more preferably 2.5 MPa or more and 5.0 MPa or less, even more preferably 2.8 MPa or more and 5.0 MPa or less, and even more preferably 3.0 MPa or more and 5.0 MPa or less.

[0048] The compressive modulus is the apparent compressive modulus of a single particle measured using a microcompression tester, and can be measured specifically by the method described in the Examples. The compressive modulus of the carrier cellulose particles can be adjusted, for example, in step (1) of the method for producing composite cellulose particles described below, by changing the degree of polymerization of the raw cellulose used, the cellulose concentration in the aqueous solution prepared for forming the cellulose emulsion, the type of cellulose non-solvent used, etc. Specifically, the compressive modulus of the carrier cellulose particles can be increased by using a raw cellulose with a high degree of polymerization or by increasing the cellulose concentration in the aqueous solution. In addition, the compressive modulus of the carrier cellulose particles can be decreased by using a raw cellulose with a low degree of polymerization or by decreasing the cellulose concentration in the aqueous solution.

[0049] The physical properties of the carrier cellulose particles can be adjusted, for example, by selecting suitable production conditions for the cellulose particles, the type of raw cellulose used to produce the cellulose particles, etc., as specifically described above.

[0050] The cellulose carrier particles preferably have a low content of compounds other than cellulose, such as impurities contained in the raw cellulose, solvents used during production, additives, etc. That is, the cellulose content in the cellulose carrier particles is preferably 95% by mass or more, more preferably 99% by mass or more, and even more preferably substantially 100% by mass.

[0051] [Method for Producing Composite Cellulose Particles] The composite cellulose particles of the present invention can be produced by a production method preferably comprising the following steps (1) to (4) in this order.Step (1): A step of mixing a water-in-oil cellulose emulsion containing cellulose, water, and an organic solvent with a cellulose non-solvent to precipitate coarse cellulose particles and obtain a suspension containing the coarse cellulose particles. Step (2): A step of subjecting the suspension containing the coarse cellulose particles obtained in step (1) to solid-liquid separation, and then washing the obtained coarse cellulose wet particles to obtain purified cellulose wet particles. Step (3): A step of obtaining carrier cellulose particles or a carrier cellulose particle dispersion by the following step (3-1) or step (3-2). Step (3-1): A step of drying the purified cellulose wet particles obtained in step (2) to obtain dried cellulose particles as carrier cellulose particles. Step (3-2): A step of mixing the purified cellulose wet particles obtained in step (2) with an azeotropic solvent having an azeotropic point with water, and distilling off the water contained in the purified cellulose wet particles by azeotropy to obtain a dehydrated cellulose particle dispersion in which dehydrated cellulose particles are dispersed in the azeotropic solvent as a carrier cellulose particle dispersion. Step (4): A step of obtaining composite cellulose particles by the following step (4-1) or step (4-2). Step (4-1): A step of mixing the carrier cellulose particles obtained in the step (3-1) with a functional substance dispersion liquid in which a functional substance is dispersed in an organic solvent or a functional substance solution in which a functional substance is dissolved in an organic solvent, and then removing the organic solvent to obtain composite cellulose particles containing the functional substance. Step (4-2): A step of obtaining composite cellulose particles by the following step (4-2a) or step (4-2b). Step (4-2a): A step of mixing the carrier cellulose particle dispersion liquid obtained in the step (3-2) with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2) to obtain composite cellulose particles containing the functional substance. Step (4-2b): A step of obtaining composite cellulose particles containing the functional substance by subjecting the carrier cellulose particle dispersion obtained in the step (3-2) to solid-liquid separation to obtain a cake, mixing the cake with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2).By using the above production method, composite cellulose particles having the above physical properties can be easily produced.

[0052] In the method for producing composite cellulose particles of the present invention, in step (4-2), the functional substance to be mixed with the carrier cellulose particle dispersion obtained in step (3-2) or the cake obtained by solid-liquid separation of the carrier cellulose particle dispersion obtained in step (3-2) may be used without pretreatment, or may be used as a functional substance dispersion in which the functional substance is dispersed in an organic solvent or as a functional substance solution in which the functional substance is dissolved in an organic solvent. When the functional substance is used as a functional substance dispersion or functional substance solution, the solvent containing the azeotropic solvent to be removed in step (4-2) is the azeotropic solvent used in step (3-2) and the organic solvent used in step (4-2).

[0053] <Step (1)> Step (1) is a step of mixing a water-in-oil cellulose emulsion containing cellulose, water, and an organic solvent with a cellulose non-solvent to precipitate coarse cellulose particles and obtain a suspension containing the coarse cellulose particles. In the method for producing composite cellulose particles of the present invention, the cellulose used to obtain the water-in-oil cellulose emulsion, i.e., the cellulose used in step (1), is also referred to as raw material cellulose. The suspension containing coarse cellulose particles can be obtained by the following steps (1-1), (1-2), and (1-3). Step (1-1): A step of mixing raw cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution. Step (1-2): A step of mixing the cellulose aqueous solution obtained in step (1-1) with an organic solvent to prepare a cellulose emulsion. Step (1-3): A step of mixing the cellulose emulsion obtained in step (1-2) with a cellulose non-solvent to precipitate coarse cellulose particles and obtain a suspension containing the coarse cellulose particles. Note that the cellulose aqueous solution prepared in step (1-1) is different from a cellulose suspension and is a solution in which cellulose is dissolved in an alkaline aqueous solution. Here, the state in which the cellulose is "dissolved" means that the cellulose aqueous solution is transparent to the naked eye. Note that the cellulose may be partially dispersed. It is believed that by preparing a cellulose aqueous solution in step (1-1) and subjecting the aqueous solution to step (1-2) and thereafter, it becomes easy to control the morphology inside the cellulose particles, and carrier cellulose particles having desired physical properties can be easily produced.

[0054] <Step (1-1)> Step (1-1) is a step of mixing raw cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution. (Raw Cellulose) From the viewpoint of environmental consideration, the raw cellulose used in step (1-1) is preferably chemically unmodified and chemically pure cellulose. Examples of the raw cellulose include wood such as various wood chips, pruned branches of various trees, thinned wood, branches, construction waste, and factory waste; pulp such as wood pulp produced from wood and cotton linter pulp obtained from the 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. Various cellulose-containing raw materials can be used. Among these, from the viewpoints of cellulose purity in the raw cellulose, degree of polymerization of cellulose, and ease of availability, wood such as various wood chips, pruned branches of various trees, thinned wood, branches, construction waste, and factory waste; wood pulp produced from wood; and pulp such as cotton linter pulp obtained from the fibers around cotton seeds are preferred. Examples of the form of the raw cellulose include powder, sheet, and cotton. Among these, from the viewpoint of excellent solubility in an alkaline aqueous solution, the raw cellulose is preferably in powder form.

[0055] From the viewpoint of improving the production efficiency of composite cellulose particles, the degree of polymerization of the starting cellulose 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 improving solubility in an alkaline aqueous solution, it is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less. From the same viewpoint, the degree of polymerization of the starting cellulose is preferably 10 or more and 1000 or less, more preferably 50 or more and 500 or less, even more preferably 100 or more and 500 or less, and even more preferably 150 or more and 300 or less. The degree of polymerization of the starting cellulose is generally controlled by the conditions for acid hydrolysis of the starting pulp. For example, a starting cellulose with a low degree of polymerization can be obtained by extending the acid hydrolysis time.

[0056] Either crystalline cellulose or amorphous cellulose can be used as the raw material cellulose. However, from the viewpoint of obtaining composite cellulose particles having the desired physical properties and from the viewpoint of ease of availability, crystalline cellulose is preferred, and cellulose type I crystalline cellulose is more preferred.

[0057] When the starting cellulose is in a powder form, the median diameter of the starting cellulose is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, still more preferably 20 μm or more, and even more preferably 30 μm or more from the viewpoint of improving handleability, and is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, still more preferably 150 μm or less, still more preferably 100 μm or less, and even more preferably 70 μm or less from the viewpoint of improving solubility in an alkaline aqueous solution. ５０ ) can be measured in the same manner as above.

[0058] (Alkaline aqueous solution) The alkaline aqueous solution used in step (1-1) is not particularly limited as long as it is alkaline and can dissolve cellulose. The alkaline compound used in the alkaline aqueous solution can be either an inorganic alkaline compound or an organic alkaline compound, and examples thereof include alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; ammonia; and tertiary amines such as trimethylamine and triethylamine. Among these, the alkaline compound is preferably an alkali metal hydroxide from the viewpoint of availability and economy, and more preferably one or more compounds selected from the group consisting of sodium hydroxide and lithium hydroxide, and even more preferably sodium hydroxide, from the viewpoint of improving the solubility of cellulose. The alkaline compounds can be used alone or in combination of two or more compounds.

[0059] From the viewpoint of improving the solubility of the starting cellulose and the stability of the resulting cellulose aqueous solution, the concentration of the alkali compound in the aqueous alkali solution is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and still more preferably 4% by mass or more, and from the same viewpoint, it is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and still more preferably 20% by mass or less. From the same viewpoint, the concentration of the alkali compound in the aqueous alkali solution is preferably 1% by mass or more and 40% by mass or less, more preferably 2% by mass or more and 30% by mass or less, even more preferably 3% by mass or more and 25% by mass or less, and still more preferably 4% by mass or more and 20% by mass or less.

[0060] In step (1-1), from the viewpoint of improving production efficiency, the solubility of the starting cellulose, and the stability of the resulting cellulose aqueous solution, alkaline aqueous solutions of different concentrations may be mixed with the starting cellulose in multiple batches. Specifically, in step (1-1), the starting cellulose is preferably mixed with alkaline aqueous solution A, in which the alkaline compound concentration in the alkaline aqueous solution is 1% by mass or more and 10% by mass or less, and then alkaline aqueous solution B, in which the alkaline compound concentration in the alkaline aqueous solution is more than 10% by mass and 40% by mass or less, is added and mixed to prepare the cellulose aqueous solution. The alkaline compound concentration in alkaline aqueous solution A is more preferably 2% by mass or more and 8% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less. The alkaline compound concentration in alkaline aqueous solution B is more preferably 15% by mass or more and 30% by mass or less, and even more preferably 20% by mass or more and 25% by mass or less. When the alkaline aqueous solution A and the alkaline aqueous solution B are used in the step (1-1), their ratio is not particularly limited. However, from the viewpoint of improving production efficiency and improving the stability of the resulting cellulose aqueous solution, the mass ratio of the alkaline aqueous solution A to the alkaline aqueous solution B (A / B) is preferably in the range of 1 or more and 10 or less, more preferably 2 or more and 8 or less, and even more preferably 3 or more and 6 or less.

[0061] The mixing of the starting cellulose and the aqueous alkali solution in step (1-1) can be carried out by adding the starting cellulose to the aqueous alkali solution and stirring using a known device. The temperature during mixing of the starting cellulose and the aqueous alkali solution is preferably 10°C or lower, more preferably 5°C or lower, and even more preferably 0°C or lower, from the viewpoint of uniformly dispersing the starting cellulose and efficiently dissolving it. Furthermore, from the viewpoint of improving the solubility of cellulose without freezing, the temperature is preferably −20°C or higher, more preferably −10°C or higher, and even more preferably −5°C or higher. The temperature during mixing of the starting cellulose and the aqueous alkali solution is preferably −20°C or higher and 10°C or lower, more preferably −10°C or higher and 5°C or lower, and even more preferably −5°C or higher and 0°C or lower. When aqueous alkali solution A and aqueous alkali solution B are used, it is preferable to add the starting cellulose to aqueous alkali solution A and stir and mix them, then adjust the temperature of the mixture to the above-mentioned range, and then add aqueous alkali solution B and mix.

[0062] The stirring time is not particularly limited as it depends on the production scale, the concentration of the alkaline compound in the alkaline aqueous solution, and the temperature, and is set appropriately. Usually, stirring is continued until the starting cellulose is dissolved as can be seen visually.

[0063] The cellulose concentration in the cellulose aqueous solution obtained in step (1-1) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, from the viewpoint of the production efficiency of the resulting composite cellulose particles. Furthermore, the cellulose concentration in the cellulose aqueous solution is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 9% by mass or less, and even more preferably 8% by mass or less, from the viewpoint of achieving a viscosity that facilitates the preparation of a cellulose emulsion when the cellulose aqueous solution is subjected to step (1-2). From the same viewpoint, the cellulose concentration in the cellulose aqueous solution obtained in step (1-1) is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass or less, even more preferably 1% by mass or more and 9% by mass or less, and even more preferably 2% by mass or more and 8% by mass or less.

[0064] From the viewpoint of improving the solubility of the starting cellulose and the stability of the resulting cellulose aqueous solution, the alkali compound concentration in the aqueous cellulose solution obtained in step (1-1) is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, still more preferably 3% by mass or more, and even more preferably 5% by mass or more, and from the same viewpoint, it is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. From the same viewpoint, the alkali compound concentration in the aqueous cellulose solution obtained in step (1-1) is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 15% by mass or less, even more preferably 2% by mass or more and 12% by mass or less, still more preferably 3% by mass or more and 10% by mass or less, and even more preferably 5% by mass or more and 10% by mass or less.

[0065] <Step (1-2)> Step (1-2) is a step of preparing a cellulose emulsion by mixing the cellulose aqueous solution obtained in step (1-1) with an organic solvent. Step (1-2) makes it possible to prepare a water-in-oil cellulose emulsion that can produce cellulose particles having a desired median diameter for use in composite formation.

[0066] The organic solvent used in step (1-2) is not particularly limited as long as it is a water-immiscible organic solvent that can be mixed with the aqueous cellulose solution to prepare a cellulose emulsion. The octanol / water partition coefficient ClogP of the organic solvent used here is preferably 0.5 or more, more preferably 1.0 or more, even more preferably 2.0 or more, and even more preferably 2.8 or more, from the viewpoint of obtaining a water-in-oil emulsion in step (1-2). The upper limit of the octanol / water partition coefficient ClogP of the organic solvent used in step (1-2) is not particularly limited, but is preferably 10.0 or less, more preferably 8.5 or less, and even more preferably 7.0 or less, from the viewpoint of solubility in a cellulose non-solvent, as described below. In the method for producing composite cellulose particles of the present invention, when the organic solvent used in step (1-2) is a mixed solvent, the octanol / water partition coefficient ClogP of the organic solvent can be a weighted average of the ClogP values ​​of the individual organic solvents, with the volume of each solvent constituting the mixed solvent being used as a weight.

[0067] In this specification, the octanol / water partition coefficient ClogP refers to a measure that indicates the partition 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 calculation formula for the octanol-water partition coefficient (logP) determined in accordance with EPIWEB4.1 (US EPA) and defined by the following formula: logP = log ([substance] octanol / [substance] water) In the 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.

[0068] Preferred organic solvents used in step (1-2) include hydrocarbon solvents, ester solvents, and halogenated solvents. Examples of hydrocarbon solvents include chain aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. The chain aliphatic hydrocarbons preferably have 6 or more carbon atoms, more preferably 8 or more carbon atoms, and preferably 18 or less, and more preferably 12 or less carbon atoms. The chain aliphatic hydrocarbons may be either linear aliphatic hydrocarbons or branched aliphatic hydrocarbons. The alicyclic hydrocarbons and aromatic hydrocarbons preferably have 6 or more and 18 or less carbon atoms, more preferably 6 or more and 12 or less carbon atoms. Specific examples of hydrocarbon solvents include n-pentane, n-hexane, n-heptane, n-octane, isooctane, n-decane, isodecane, n-dodecane, isododecane, tetradecane, hexadecane, octadecane, cyclohexane, methylcyclohexane, cycloheptane, methylcycloheptane, toluene, and xylene.

[0069] The ester solvent is preferably an ester having from 4 to 10 carbon atoms, such as ethyl acetate, butyl acetate, etc. The halogen-based solvent is, for example, dichloromethane, chloroform, dichloroethane, dichlorobenzene, etc.

[0070] The organic solvent may be used alone or in combination of two or more. From the viewpoint of facilitating the preparation of a water-in-oil cellulose emulsion, the organic solvent is preferably a hydrocarbon solvent, more preferably a chain aliphatic hydrocarbon, and from the viewpoint of production, is further preferably one or more selected from the group consisting of n-pentane, n-hexane, n-heptane, n-octane, isooctane, decane, isodecane, dodecane, isododecane, tetradecane, hexadecane, and octadecane, and still further preferably one or more selected from the group consisting of n-octane, isooctane, n-decane, isodecane, n-dodecane, and isododecane.

[0071] In step (1-2), the amount of organic solvent mixed with the aqueous cellulose solution is, from the viewpoint of improving the emulsion stability of the water-in-oil cellulose emulsion, preferably 80 parts by mass or more, more preferably 90 parts by mass, even more preferably 100 parts by mass or more, still more preferably 120 parts by mass or more, and from the viewpoint of easily obtaining carrier cellulose particles having the desired median diameter, preferably 1000 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 500 parts by mass or less, even more preferably 300 parts by mass or less, even more preferably 200 parts by mass or less. And, in step (1-2), the amount of organic solvent mixed with the aqueous cellulose solution is, from the same viewpoint, preferably 80 parts by mass or more to 1000 parts by mass or less, more preferably 90 parts by mass or more to 800 parts by mass or less, even more preferably 90 parts by mass or more to 500 parts by mass or less, still more preferably 100 parts by mass or more to 300 parts by mass or less, even more preferably 100 parts by mass or more to 200 parts by mass or less.

[0072] In step (1-2), from the viewpoint of improving the emulsion stability of the water-in-oil cellulose emulsion, it is preferable to further mix an emulsifier in addition to the aqueous cellulose solution and the organic solvent. Examples of the emulsifier include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Among these, from the viewpoint of improving the emulsion stability of the water-in-oil cellulose emulsion, nonionic surfactants are preferred.

[0073] From the viewpoint of improving the emulsion stability of water-in-oil cellulose emulsions, the HLB (Hydrophile-Lipophile Balance) of the nonionic surfactant used as an emulsifier is preferably 1 or more and 10 or less, more preferably 1 or more and 8 or less, even more preferably 1 or more and 6 or less, still more preferably 1 or more and 5 or less, still more preferably 1 or more and 4 or less, and still more preferably 1 or more and 3 or less. Here, HLB is an index representing the ratio of the relative affinity of a surfactant for both liquids in an oil-water system, and can be calculated from the following formula using the Griffin method (J. Soc. Cosm. Chem., 1954, 5:249-256): HLB = 20 × [(molecular weight of hydrophilic group contained in surfactant) / (molecular weight of surfactant)]. Examples of hydrophilic groups contained in surfactants include hydroxyl groups and ethyleneoxy groups. The HLB of two or more types of nonionic surfactants can be determined as a weighted average obtained by multiplying the HLB of each nonionic surfactant by the mass fraction of each nonionic surfactant (i.e., the value obtained by dividing the mass of each nonionic surfactant by the total mass of the nonionic surfactants).

[0074] Examples of nonionic surfactants used as emulsifiers include sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyoxyethylene hydrogenated castor oil, polyglycerin fatty acid esters, glycerin fatty acid esters, sucrose fatty acid esters, polyether-modified silicones, and alkyl alkanolamides. These can be used alone or in combination of two or more. The number of carbon atoms in the alkyl groups in the fatty acid units constituting these nonionic surfactants, such as sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyglycerin fatty acid esters, glycerin fatty acid esters, and sucrose fatty acid esters, and the polyoxyethylene alkyl ethers, is preferably 12 or more, more preferably 16 or more, even more preferably 18 or more, and preferably 24 or less, more preferably 22 or less, from the viewpoint of achieving an HLB within the above-mentioned range. When polyoxyethylene groups are present, those having an average added mole number of polyoxyethylene groups of 10 or less are preferred.

[0075] Examples of sorbitan fatty acid esters include sorbitan monooleate, sorbitan monostearate, sorbitan sesquioleate, sorbitan coconut oil fatty acid, sorbitan monopalmitate, sorbitan tristearate, and sorbitan trioleate. Examples of polyoxyethylene sorbitan fatty acid esters include polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate. Examples of polyoxyethylene alkyl ethers include polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether. Examples of polyoxyethylene glycerin fatty acid esters include polyoxyethylene glyceryl monooleate. Examples of polyoxyethylene sorbit fatty acid esters include polyoxyethylene sorbit tetraoleate. Examples of polyglycerin fatty acid esters include polyglyceryl trilaurate, polyglyceryl dimyristate, polyglyceryl dioleate, polyglyceryl distearate, and polyglyceryl diisostearate. Examples of glycerin fatty acid esters include lauric acid monoglyceride, oleic acid monoglyceride, and stearate monoglyceride. Examples of sucrose fatty acid esters include sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate, and sucrose behenate. Examples of alkyl alkanolamides include oleic acid diethanolamide, palm kernel oil fatty acid diethanolamide, coconut oil fatty acid diethanolamide, lauric acid diethanolamide, coconut oil fatty acid monoethanolamide, lauric acid isopropanolamide, lauric acid monoethanolamide, coconut oil fatty acid N-methylethanolamide, polyoxyethylene coconut oil fatty acid monoethanolamide, and polyoxypropylene coconut oil fatty acid monoisopropanolamide.

[0076] Among the above, from the viewpoint of further improving the emulsion stability of water-in-oil cellulose emulsions, the nonionic surfactant used as an emulsifier is preferably one or more selected from the group consisting of sorbitan fatty acid esters, polyoxyethylene alkyl ethers, polyglycerin fatty acid esters, glycerin fatty acid esters, sucrose fatty acid esters, alkyl alkanolamides, and polyether-modified silicones, more preferably one or more selected from the group consisting of sorbitan fatty acid esters, polyglycerin fatty acid esters, glycerin fatty acid esters, and sucrose fatty acid esters, even more preferably sucrose fatty acid esters, even more preferably one or more selected from the group consisting of sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate, and sucrose behenate, and still more preferably one or more selected from the group consisting of sucrose erucate and sucrose behenate.

[0077] In the step (1-2), when an emulsifier is further mixed, the amount of the emulsifier mixed is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the organic solvent, from the viewpoint of further improving the emulsion stability of the water-in-oil cellulose emulsion, and from the viewpoint of ease of washing (economic efficiency) and economic efficiency, it is preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.5 parts by mass or less. And, from the same viewpoint, the amount of the emulsifier mixed is preferably 0.01 parts by mass or more and 2.5 parts by mass or less, more preferably 0.1 parts by mass or more and 2.0 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.5 parts by mass or less, relative to 100 parts by mass of the organic solvent.

[0078] The emulsifier may be added to either the aqueous cellulose solution or the organic solvent before mixing, or may be added after mixing the aqueous cellulose solution and the organic solvent, or may be mixed with the aqueous cellulose solution and the organic solvent simultaneously.

[0079] The cellulose emulsion can be prepared, for example, by adding an organic solvent and an emulsifier to an aqueous cellulose solution and stirring the mixture using a known mixer such as a homomixer or a high-speed emulsifying disperser. The temperature during mixing of the aqueous cellulose solution and the organic solvent is preferably 40°C or lower, more preferably 30°C or lower, even more preferably 25°C or lower, and even more preferably 15°C or lower, from the viewpoint of further improving the emulsion stability of the water-in-oil cellulose emulsion. Furthermore, the temperature during mixing of the aqueous cellulose solution and the organic solvent is preferably -20°C or higher, more preferably -10°C or higher, and even more preferably -5°C or higher, from the viewpoint of preparing a water-in-oil cellulose emulsion without freezing. Furthermore, the temperature during mixing of the aqueous cellulose solution and the organic solvent is, from the same viewpoint, preferably -20°C or higher and 40°C or lower, more preferably -10°C or higher and 30°C or lower, even more preferably -5°C or higher and 25°C or lower, and even more preferably -5°C or higher and 15°C or lower.

[0080] The stirring speed when mixing the aqueous cellulose solution with the organic solvent is appropriately selected depending on the production scale, the equipment used, the viscosity of the cellulose emulsion, etc., but from the viewpoint of controlling the emulsion droplet size and obtaining carrier cellulose particles with the desired median size, when using, for example, the homomixer used in the examples, the stirring speed is preferably 1000 rpm or more, more preferably 3000 rpm or more, even more preferably 3500 rpm or more, still more preferably 4000 rpm or more, and is preferably 15000 rpm or less, more preferably 14000 rpm or less, even more preferably 13000 rpm or less, and still more preferably 12000 rpm or less. From the same viewpoint, the stirring speed when mixing the aqueous cellulose solution and the organic solvent is preferably 1,000 rpm or more and 15,000 rpm or less, more preferably 3,000 rpm or more and 14,000 rpm or less, even more preferably 3,500 rpm or more and 13,000 rpm or less, and still more preferably 4,000 rpm or more and 12,000 rpm or less.

[0081] The time for mixing the aqueous cellulose solution with the organic solvent is appropriately selected depending on the production scale, the equipment used, the viscosity of the cellulose emulsion, and the like.

[0082] <Step (1-3)> Next, the cellulose emulsion obtained in step (1-2) is mixed with a cellulose non-solvent to precipitate coarse cellulose particles, thereby obtaining a suspension containing the coarse cellulose particles. The cellulose non-solvent is a so-called cellulose non-solvent that does not have the ability to dissolve cellulose, and is a solvent that is compatible with the alkaline aqueous solution and the organic solvent. By mixing the solvent with the cellulose emulsion, the cellulose non-solvent flows into the interior of the cellulose, causing the organic solvent inside the cellulose to flow out, thereby forming a phase-separated structure. This allows the morphology inside the cellulose particles to be controlled, and the cellulose to be coagulated in a state where a desired porous structure is formed, and precipitated as particles (porous cellulose particles).

[0083] In the method for producing composite cellulose particles of the present invention, the cellulose nonsolvent preferably has an octanol / water partition coefficient ClogP of less than 0.5, more preferably 0.3 or less, even more preferably 0.1 or less, even more preferably −0.2 or less, and preferably −1.0 or more, from the viewpoints of easily precipitating crude cellulose particles and controlling the internal morphology of the cellulose particles to obtain carrier cellulose particles having desired physical properties. From the same viewpoints as above, the cellulose nonsolvent preferably has an octanol / water partition coefficient ClogP of −1.0 or more but less than 0.5, more preferably −1.0 or more but 0.3 or less, even more preferably −1.0 or more but 0.1 or less, even more preferably −1.0 or more but 0.2 or less. In the method for producing composite cellulose of the present invention, the cellulose nonsolvent may be used alone or in combination of two or more solvents. When two or more solvents are mixed and used, the octanol / water partition coefficient ClogP of the cellulose nonsolvent can be a weighted average of the ClogP of each solvent, where the volume of each solvent constituting the mixed cellulose nonsolvent is weighted. When the octanol / water partition coefficient of the cellulose nonsolvent is less than 0.5, separation of the water and the cellulose nonsolvent in a water-in-oil cellulose emulsion can be suppressed even with a small amount of cellulose nonsolvent, allowing cellulose to be precipitated efficiently and further improving the productivity of cellulose particles.

[0084] The cellulose non-solvent is preferably an alcohol solvent, more preferably an alcohol having 4 or less carbon atoms. Examples of alcohols that can be used as cellulose non-solvents include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and tert-butyl alcohol, and these can be used alone or in combination of two or more.

[0085] Among the above, from the same viewpoint as above, the cellulose non-solvent is preferably one or more selected from the group consisting of methanol, ethanol, 2-propanol, 1-butanol, 2-butanol, and 2-methyl-1-propanol, and more preferably one or more selected from the group consisting of methanol (ClogP −0.77) and ethanol (ClogP −0.31).

[0086] The amount of cellulose non-solvent mixed is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of cellulose emulsion, from the viewpoint of easily precipitating crude cellulose particles, and from the viewpoint of controlling the internal morphology of the cellulose particles to obtain carrier cellulose particles having the desired physical properties, and from the viewpoint of maintaining emulsion stability, and from the viewpoint of ease of washing (productivity) and economic efficiency, it is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and even more preferably 60 parts by mass or less. And, from the same viewpoint, the amount of cellulose non-solvent mixed is preferably 5 parts by mass or more and 200 parts by mass or less, more preferably 10 parts by mass or more and 150 parts by mass or less, even more preferably 15 parts by mass or more and 100 parts by mass or less, and even more preferably 20 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of cellulose emulsion.

[0087] In step (1), it is preferable to further mix an acid from the viewpoint of neutralizing the alkaline compound remaining in the crude cellulose particles. The acid may be either an inorganic acid or an organic acid, but from the viewpoint of solubility in the cellulose emulsion and the cellulose non-solvent, it is preferably an organic acid, more preferably a carboxylic acid having 4 or less carbon atoms. Examples of carboxylic acids having 4 or less carbon atoms include monocarboxylic acids, dicarboxylic acids, and hydroxycarboxylic acids having 4 or less carbon atoms, such as formic acid, acetic acid, propionic acid, butyric acid, lactic acid, citric acid, malic acid, and succinic acid. Among these, from the viewpoint of solubility in the cellulose emulsion and the cellulose non-solvent, it is preferably one or more selected from the group consisting of acetic acid, lactic acid, malic acid, and succinic acid, more preferably one or more selected from the group consisting of acetic acid and malic acid.

[0088] When an acid is used in step (1), the amount of acid mixed is preferably 1.0 equivalent or more, more preferably 1.2 equivalents or more, and even more preferably 1.4 equivalents or more, relative to the alkali compound used in step (1-1), from the viewpoint of neutralizing the alkali compound remaining in the crude cellulose particles; and from the viewpoint of economy, it is preferably 3.0 equivalents or less, more preferably 2.0 equivalents or less, and even more preferably 1.8 equivalents or less. The amount of acid mixed in step (1) is, from the same viewpoint, preferably 1.0 equivalents or more and 3.0 equivalents or less, more preferably 1.2 equivalents or more and 2.0 equivalents or less, and even more preferably 1.4 equivalents or more and 1.8 equivalents or less, relative to the alkali compound used in step (1-1). The pH after neutralization with the acid is preferably 6 or more and 8 or less, more preferably 6.5 or more and 7.5 or less.

[0089] The cellulose emulsion and the cellulose non-solvent can be mixed, for example, by adding the cellulose emulsion to the cellulose non-solvent and stirring using a known device. When adding the cellulose emulsion to the cellulose non-solvent, it is preferable to add the cellulose emulsion while stirring the cellulose non-solvent so as not to cause the emulsion droplets to bond together. The temperature when mixing the cellulose emulsion and the cellulose non-solvent is preferably 0°C or higher, more preferably 5°C or higher, even more preferably 15°C or higher, and preferably 50°C or lower, more preferably 40°C or lower, even more preferably 30°C or lower. The temperature when mixing the cellulose emulsion and the cellulose non-solvent is preferably 0°C or higher and 50°C or lower, more preferably 5°C or higher and 40°C or lower, even more preferably 15°C or higher and 30°C or lower.

[0090] When an acid is mixed in step (1), the acid may be mixed simultaneously with the cellulose emulsion and the cellulose non-solvent, or may be mixed after the cellulose emulsion and the cellulose non-solvent are mixed. From the viewpoint of efficiently neutralizing the alkaline compounds remaining in the crude cellulose particles (containing the neutralization salt and the emulsifier as impurities), it is preferable to mix the acid after the cellulose emulsion and the cellulose non-solvent are mixed.

[0091] The stirring speed during mixing of the cellulose emulsion and the cellulose non-solvent depends on the production scale and temperature and is set appropriately, but from the viewpoint of sufficiently precipitating the coarse cellulose particles and controlling the internal morphology of the cellulose particles to obtain carrier cellulose particles with the desired physical properties, for example, when using the stirring blades of the Examples, it is preferably 100 rpm or more, more preferably 200 rpm or more, and also preferably 2000 rpm or less, more preferably 1500 rpm or less, even more preferably 1000 rpm or less, and even more preferably 800 rpm or less. From the same viewpoint, the stirring speed during mixing of the cellulose emulsion and the cellulose non-solvent is preferably 100 rpm or more and 2000 rpm or less, more preferably 200 rpm or more and 1500 rpm or less, even more preferably 200 rpm or more and 1000 rpm or less, and even more preferably 200 rpm or more and 800 rpm or less. The stirring time when mixing the cellulose emulsion and the cellulose non-solvent depends on the production scale and temperature and is set appropriately, but from the viewpoint of sufficiently precipitating the coarse cellulose particles and controlling the internal morphology of the cellulose particles to obtain carrier cellulose particles with the desired physical properties, it is usually 0.2 hours or more and 12 hours or less, preferably 0.5 hours or more and 6 hours or less, and more preferably 0.5 hours or more and 3 hours or less.

[0092] <Step (2)> Step (2) is a step in which the suspension containing the coarse cellulose particles obtained in step (1) is subjected to solid-liquid separation, and the resulting coarse cellulose wet particles are then washed to obtain purified cellulose wet particles. Solid-liquid separation of the suspension containing coarse cellulose particles can be carried out by centrifugation, filtration, decantation, or a combination thereof. Next, the coarse cellulose wet particles obtained after solid-liquid separation are washed to remove impurities such as the organic solvent and emulsifier used in step (1-2) and the neutralized salt generated in step (1). The washing treatment of the coarse cellulose wet particles can be carried out using water, an organic solvent, or a combination thereof. An organic solvent is preferably used to remove hydrophobic impurities such as the organic solvent and emulsifier used in step (1-2), and water is preferably used to remove water-soluble impurities such as the neutralized salt.

[0093] The organic solvent used in the washing treatment of the wet crude cellulose particles in step (2) is preferably a solvent that can dissolve the organic solvent and emulsifier used in step (1-2) and can be easily removed by distillation, and examples thereof include ketone solvents having 6 or less carbon atoms, such as acetone and methyl isobutyl ketone, and alcohol solvents having 6 or less carbon atoms, such as ethanol and 2-propanol.

[0094] <Step (3)> Step (3) is a step of obtaining dried cellulose particles as carrier cellulose particles or a dehydrated cellulose particle dispersion in which dehydrated cellulose particles are dispersed as a carrier cellulose particle dispersion by the following step (3-1) or step (3-2).

[0095] <Step (3-1)> Step (3-1) is a step of drying the purified wet cellulose particles obtained in step (2) to obtain dried cellulose particles (cellulose particles in a dry state) as carrier cellulose particles. Methods for drying the purified wet cellulose particles include freeze-drying, drying under reduced pressure, drying with supercritical carbon dioxide, etc. Particle shrinkage is suppressed during drying, and the porous structure of the particles is maintained, thereby obtaining dried porous cellulose particles as carrier cellulose particles.

[0096] From the viewpoint of suppressing particle shrinkage during drying and maintaining the porous structure, it is preferable to use a freeze-drying method. Freeze-drying preferably involves pre-freezing the purified wet cellulose particles, followed by primary and secondary drying. Pre-freezing is preferably performed by rapid freezing at a temperature of -200°C or higher and -50°C or lower under normal pressure. Primary drying is preferably performed under a vacuum of 0.1 Pa or higher and 100 Pa or lower and at a temperature of -20°C or higher and -5°C or lower, in which ice in the pre-frozen material is sublimated. It is more preferable to then perform secondary drying under a vacuum of 0.1 Pa or higher and 100 Pa or lower and at a temperature of 20°C or higher and 40°C or lower.

[0097] When drying is performed using reduced pressure drying, supercritical carbon dioxide, or the like, it is preferable to further disperse the purified wet cellulose particles after the washing treatment in a replacement dispersion medium to perform dispersion medium replacement, from the viewpoint of suppressing shrinkage of the resulting porous cellulose particles during drying. The replacement dispersion medium used for dispersion medium replacement is preferably an organic solvent with a low surface tension, from the viewpoint of suppressing shrinkage of the resulting porous cellulose particles during drying, and is preferably an organic solvent with a surface tension of preferably 20 mN / m or less, more preferably 18 mN / m or less at 25°C. The surface tension is the surface tension value measured at 25°C using an automatic surface tensiometer (K100 manufactured by KRUSS).

[0098] Examples of the low surface tension organic solvent include aliphatic hydrocarbons having 7 or less carbon atoms, such as pentane, hexane, and heptane, as well as ether compounds having 4 or less carbon atoms, such as ethyl methyl ether and diethyl ether, which can be used alone or in combination of two or more. Among these, pentane is preferred from the viewpoint of suppressing shrinkage of the resulting porous cellulose particles during drying.

[0099] The amount of the replacement dispersion medium used for the dispersion medium replacement is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, relative to 100 parts by mass of the purified cellulose wet particles, from the viewpoint of suppressing particle shrinkage and obtaining particles of the desired structure, and is preferably 2000 parts by mass or less, more preferably 1000 parts by mass or less, and even more preferably 600 parts by mass or less, from the viewpoints of productivity and economy (output relative to the batch size). The amount of the replacement dispersion medium used for the dispersion medium replacement is preferably 100 parts by mass or more and 2000 parts by mass or less, more preferably 200 parts by mass or more and 1000 parts by mass or less, and even more preferably 200 parts by mass or more and 600 parts by mass or less, relative to 100 parts by mass of the purified cellulose wet particles, from the same viewpoint.

[0100] The dispersion medium replacement can be carried out, for example, by adding the purified cellulose wet particles to a replacement dispersion medium and stirring using a known device. The temperature during mixing of the purified cellulose wet particles and the replacement dispersion medium is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 15°C or higher, from the viewpoint of obtaining an appropriate pore size for improving the encapsulation stability and release property of the functional substance, and from the same viewpoint, is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower. The temperature during mixing of the purified cellulose wet particles and the replacement dispersion medium is preferably 0°C or higher and 50°C or lower, more preferably 5°C or higher and 40°C or lower, and even more preferably 15°C or higher and 30°C or lower, from the same viewpoint.

[0101] The stirring speed during mixing of the purified wet cellulose particles with the replacement dispersion medium depends on the production scale and temperature and is set appropriately, but from the viewpoint of sufficiently dispersing the cellulose particles, it is preferably 100 rpm or more, more preferably 200 rpm or more, and from the viewpoints of economy and productivity, it is preferably 2000 rpm or less, more preferably 1500 rpm or less, even more preferably 1000 rpm or less, and still more preferably 800 rpm or less. From the same viewpoint, the stirring speed during mixing of the cellulose particles after the washing treatment with the replacement dispersion medium is preferably 100 rpm or more and 2000 rpm or less, more preferably 200 rpm or more and 1500 rpm or less, even more preferably 200 rpm or more and 1000 rpm or less, and still more preferably 200 rpm or more and 800 rpm or less. The stirring time for mixing the washed cellulose particles with the replacement dispersion medium depends on the production scale and temperature and is set appropriately, but is usually from 0.2 hours to 12 hours, preferably from 0.5 hours to 6 hours.

[0102] By carrying out the dispersion medium substitution, a suspension containing purified wet cellulose particles is obtained in which the water contained in the particles has been substituted with the substituting dispersion medium. The suspension is subjected to solid-liquid separation in the same manner as above to recover the purified wet cellulose particles, which are then subjected to the drying treatment described above to obtain dried cellulose particles, which can be used as the carrier cellulose particles of the present invention.

[0103] <Step (3-2)> Step (3-2) is a step of mixing the purified wet cellulose particles obtained in step (2) with an azeotropic solvent having an azeotropic point with water, and distilling off the water contained in the purified wet cellulose particles by azeotropy to obtain a dehydrated cellulose particle dispersion in which dehydrated cellulose particles are dispersed in the azeotropic solvent as a carrier cellulose particle dispersion. In step (3-2), by mixing the purified wet cellulose particles with an azeotropic solvent having an azeotropic point with water and performing azeotropic distillation, it is possible to efficiently and gradually remove the water present in the cellulose particles together with the azeotropic solvent, and it is possible to obtain dehydrated cellulose particles that retain the shape of the purified wet cellulose particles as carrier cellulose particles. The amount of the azeotropic solvent mixed is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 1 part by mass of the solid content of the cellulose particles, from the viewpoint of distilling off water; and from the viewpoint of production efficiency, it is preferably 1,000 parts by mass or less, more preferably 300 parts by mass or less, even more preferably 100 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less. From the same viewpoints as above, the amount of the azeotropic solvent mixed is preferably 1 part by mass or more and 1,000 parts by mass or less, more preferably 1 part by mass or more and 300 parts by mass or less, even more preferably 5 parts by mass or more and 100 parts by mass or less, even more preferably 5 parts by mass or more and 50 parts by mass or less, and even more preferably 10 parts by mass or more and 30 parts by mass or less. The amount of the azeotropic solvent mixed described here is the total amount, and it may be added and mixed all at once or in portions. The present invention, by including step (3-2), can distill off water contained in the purified wet cellulose particles. The cellulose carrier particle dispersion obtained in step (3-2) is a cellulose carrier particle dispersion containing an azeotropic solvent having an azeotropic point with water.

[0104] The azeotropic solvent used in step (3-2) is an azeotropic solvent having an azeotropic point with water, and this azeotropic solvent is preferably one or more selected from the group consisting of azeotropic solvent 1 and azeotropic solvent 2 below.

[0105] The azeotropic solvent 1 having an azeotropic point with water preferably has an octanol / water partition coefficient ClogP of 0.5 or more, more preferably 1.0 or more, and even more preferably 2.0 or more. When the octanol / water partition coefficient ClogP of the azeotropic solvent 1 is equal to or greater than the above-mentioned lower limit, water present within (near the surface of) and between the cellulose particles can be efficiently removed by azeotropy. Furthermore, since the solvent and water separate in the resulting fraction, water can be easily removed. That is, in step (3-2), the purified wet cellulose particles obtained in step (2) are mixed with the azeotropic solvent 1, and water and the azeotropic solvent 1 are distilled off by azeotropy, and then the azeotropic solvent 1 is refluxed, thereby continuously distilling off water. By refluxing the azeotropic solvent 1 and returning it to the system, water can be repeatedly distilled off by azeotropy. Therefore, water present within and between the purified wet cellulose particles can be removed in a short time, and ultimately, dehydrated cellulose particles that retain the shape of the purified wet cellulose particles can be obtained as carrier cellulose particles. The upper limit of the octanol / water partition coefficient ClogP of the azeotropic solvent 1 is not particularly limited as long as it can be separated from water, but from the viewpoint of handleability, it is preferably 10.0 or less, more preferably 7.0 or less, and even more preferably 5.0 or less.

[0106] As the azeotropic solvent 1, for example, the same organic solvents as those exemplified in step (1-2) can be used, and is preferably at least one selected from the group consisting of hydrocarbon solvents, ester solvents, and halogenated solvents, more preferably at least one selected from the group consisting of hydrocarbon solvents and halogenated solvents. Among these, from the viewpoint of efficiently removing water from within and between wet purified cellulose particles, preferably, the solvent contains at least one selected from the group consisting of aliphatic hydrocarbons having from 5 to 12 carbon atoms, alicyclic hydrocarbons having from 5 to 12 carbon atoms, aromatic hydrocarbons having from 6 to 12 carbon atoms, and esters having from 4 to 12 carbon atoms, more preferably, an alicyclic hydrocarbon, even more preferably, at least one selected from the group consisting of cyclohexane, methylcyclohexane, cycloheptane, and methylcycloheptane, and even more preferably, cyclohexane. That is, preferably, the cellulose non-solvent in step (1) contains one or more solvents selected from the group consisting of methanol and ethanol, and the azeotropic solvent 1 in step (3-2) contains one or more solvents selected from the group consisting of aliphatic hydrocarbons having from 5 to 12 carbon atoms, alicyclic hydrocarbons having from 5 to 12 carbon atoms, aromatic hydrocarbons having from 6 to 12 carbon atoms, and esters having from 4 to 12 carbon atoms.

[0107] The octanol / water partition coefficient ClogP of the azeotropic solvent 2, which has an azeotropic point with water, is preferably less than 0.5. When the azeotropic solvent 2 is used in step (3-2), the purified wet cellulose particles obtained in step (2) are mixed with the azeotropic solvent 2 and azeotropically distilled to remove both the azeotropic solvent 2 and water. Since the azeotropic solvent 2 does not separate from the water, if water still remains in the cellulose particles, fresh azeotropic solvent 2 is added and mixed, and the azeotropic solvent 2 and water are distilled off again by azeotropic distillation. By repeating this step, dehydrated cellulose particles from which water has been distilled can be obtained as carrier cellulose particles. The azeotropic solvent 2 preferably includes one or more solvents selected from the group consisting of 1-propanol and 2-propanol, and more preferably includes 2-propanol. That is, preferably, the cellulose non-solvent in step (1) contains one or more selected from methanol and ethanol, and the azeotropic solvent 2 in step (3-2) contains one or more selected from the group consisting of 1-propanol and 2-propanol.

[0108] The boiling point (1 atm) of the azeotropic solvent used in step (3-2) is preferably 100° C. or lower, more preferably 90° C. or lower, and also preferably 30° C. or higher, more preferably 40° C. or higher. From the viewpoint of efficiently removing water from within and between cellulose particles, this azeotropic solvent has an azeotropic point with water (azeotropic point of an azeotropic mixture with water) of preferably 100° C. or lower, more preferably 95° C. or lower, even more preferably 90° C. or lower, still more preferably 85° C. or lower, and also preferably 30° C. or higher, more preferably 40° C. or higher, even more preferably 50° C. or higher, and still more preferably 60° C. or higher.

[0109] In the step (3-2), the heating temperature when water is distilled off by azeotropy is the azeotropic temperature or higher, specifically, preferably 30°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, still more preferably 60°C or higher, and preferably 100°C or lower.

[0110] In step (3-2), water contained in the purified wet cellulose particles is distilled off to obtain dehydrated cellulose particles. In step (3-2), the dehydrated cellulose particles are obtained as a dispersion of carrier cellulose particles dispersed in an azeotropic solvent.

[0111] <Substitution Step> In the method for producing composite cellulose of the present invention, a substitution step may be included after step (2) and before step (3-2), in which water contained in the purified wet cellulose particles obtained in step (2) is substituted with a solvent having an octanol / water partition coefficient ClogP of less than 0.5. This substitution step allows water present within (near the surface) and between particles of the purified wet cellulose particles obtained in step (2) to be removed by solvent substitution. This substitution step can suppress aggregation of cellulose particles when mixed with an azeotropic solvent having an azeotropic point with water in step (3-2), and also makes it easier to remove water present within the purified wet cellulose particles, allowing for more efficient dehydration. That is, the primary purpose of this substitution step is to remove water present on the particle surface and between particles of the purified wet cellulose particles, and it can facilitate the removal of water remaining inside the purified wet cellulose particles in step (3-2), thereby enabling dehydrated cellulose particles with a reduced water content to be obtained.

[0112] The octanol / water partition coefficient ClogP of the solvent used in the substitution step (hereinafter also referred to as the "substitution solvent") is preferably less than 0.5, more preferably 0.3 or less, even more preferably 0.1 or less, and preferably -1.0 or greater, from the viewpoint of reducing the water content of the resulting cellulose particles. For the same reasons as above, a solvent having an octanol / water partition coefficient ClogP of less than 0.5 is preferably an alcohol. From the viewpoint of efficiently substituting the substitution solvent for the water present within and between the purified wet cellulose particles obtained in step (2), it is preferable to use the same alcohol as exemplified as the azeotropic solvent 2 in steps (1) and (3-2) described above. Specifically, it is preferable for the alcohol to contain one or more selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol, and more preferably one or more selected from the group consisting of methanol, ethanol, and 2-propanol. Furthermore, it is also preferable to use the same alcohol as the azeotropic solvent in step (3-2) as the substitution solvent.

[0113] From the viewpoint of efficiently displacing and removing water present within and between the purified cellulose wet particles, the amount of the substitution solvent used is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and preferably 100 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, per part by mass of the solid content of the purified cellulose wet particles obtained in step (2). This substitution method involves mixing and stirring the purified cellulose wet particles with the substitution solvent, and then separating the substitution solvent by solid-liquid separation to obtain purified cellulose wet particles that have been subjected to the substitution treatment. The solid-liquid separation performed here can be performed by centrifugation, filtration, decantation, or a combination thereof. The obtained purified cellulose wet particles are subjected to the above-described step (3-2) to obtain a dehydrated cellulose particle dispersion.

[0114] <Step (4)> Step (4) is a step of obtaining composite cellulose particles by the following step (4-1) or step (4-2).

[0115] <Step (4-1)> Step (4-1) is a step of mixing the carrier cellulose particles obtained in step (3-1) with a functional substance dispersion liquid in which a functional substance is dispersed in an organic solvent or a functional substance solution in which a functional substance is dissolved in an organic solvent, and then removing the organic solvent to obtain composite cellulose particles containing the functional substance.

[0116] In step (4-1), first, a functional substance and an organic solvent are mixed to prepare a functional substance dispersion in which the functional substance is dispersed in an organic solvent, or a functional substance solution in which the functional substance is dissolved in an organic solvent. The functional substance used is the functional substance described above for the composite cellulose particles. The organic solvent is preferably one that can be removed by a drying treatment, preferably by heat drying, vacuum drying, or a combination of these, namely, heat and vacuum drying. Suitable examples of the organic solvent include ketone-based solvents having 6 or less carbon atoms, such as acetone and methyl isobutyl ketone, alcohol-based solvents having 6 or less carbon atoms, such as ethanol and 2-propanol, and volatile silicone-based solvents, such as low-viscosity dimethicone. Examples of the volatile silicone-based solvent include those having a kinematic viscosity of 2.0 mm at 25°C. ２ The volatile silicone solvent preferably has a kinematic viscosity of 1.5 mm / s or less and a boiling point of 230° C. or less. ２ / s or less, more preferably 1.0 mm ２ / s or less, more preferably 0.65 mm ２ The boiling point of the volatile silicone solvent is preferably 195°C or less, more preferably 150°C or less, and even more preferably 100°C or less.

[0117] When a functional substance dispersion is used in step (4-1) by dispersing a functional substance in an organic solvent, a combination of a functional substance and an organic solvent incapable of dissolving the functional substance is selected. This functional substance dispersion is then mixed with the carrier cellulose particles obtained in step (3-1) to thoroughly impregnate the carrier cellulose with the functional substance dispersion. The organic solvent is then removed, leaving the functional substance in the pores of the carrier cellulose particles, yielding composite cellulose particles. When a functional substance dispersion is used in this manner, the functional substance is dispersed in the organic solvent and therefore penetrates into the pores of the carrier cellulose particles in a particulate state. That is, the particles pass through the surface pores of the carrier cellulose particles and enter the pores. Therefore, it is preferable that the particle size of the functional substance is smaller than the surface pore size, and the preferred range of its average particle size is as described above in the description of the preferred range of the particulate functional substance.

[0118] When a functional substance solution is used in step (4-1) by dissolving a functional substance in an organic solvent, a combination of a functional substance and an organic solvent capable of dissolving the functional substance is selected. This functional substance solution is then mixed with the carrier cellulose particles obtained in step (3-1) to thoroughly impregnate the carrier cellulose with the functional substance solution. The organic solvent is then removed, causing the functional substance to precipitate or remain in the pores of the carrier cellulose particles, thereby obtaining composite cellulose particles. When a functional substance solution is used in this manner, the functional substance is dissolved in the organic solvent, and therefore can easily penetrate into the pores of the carrier cellulose particles in a dissolved state. In other words, a relatively large amount of functional substance can be impregnated into the pores of the carrier cellulose particles, and the functional substance can be penetrated deeper, closer to the center of the particles.

[0119] In this step (4-1), the amount of functional substance used may be determined depending on the content of the functional substance to be contained in the composite cellulose particles and its content under the production conditions. That is, a functional substance dispersion or a functional substance solution is prepared by using at least the amount of functional substance desired to be contained in the composite cellulose particles. In the method for producing composite cellulose particles of the present invention, a relatively high proportion of the functional substance can be encapsulated in the composite cellulose particles. Therefore, the amount of functional substance used is preferably in the range from the same amount to an excess of about 10% by mass relative to the amount to be contained in the composite cellulose particles.

[0120] Here, the content of the functional substance contained in the composite cellulose particles can be within the range described for the content of the functional substance in the composite cellulose particles. That is, the content of the functional substance in the composite cellulose particles is, from the viewpoint of improving the release of the functional substance, preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, still more preferably 70 parts by mass or more, still more preferably 100 parts by mass or more, still more preferably 150 parts by mass or more, still more preferably 200 parts by mass or more, still more preferably 250 parts by mass or more, relative to 100 parts by mass of the carrier cellulose particles; and from the viewpoint of improving the encapsulation stability of the functional substance, it is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, still more preferably 450 parts by mass or more, still more preferably 400 parts by mass or less. From the same viewpoint, the content of the functional substance is preferably 10 to 600 parts by mass, more preferably 30 to 500 parts by mass, even more preferably 50 to 450 parts by mass, still more preferably 70 to 400 parts by mass, even more preferably 100 to 400 parts by mass, still more preferably 150 to 400 parts by mass, still more preferably 200 to 400 parts by mass, and still more preferably 250 to 400 parts by mass. The preferred content of the functional substance varies depending on whether the composite treatment is carried out by dissolving the functional substance or by dispersing the functional substance, but the range is as explained for the composite cellulose particles.

[0121] In addition, in step (4-1), the amount of organic solvent in the functional substance dispersion or functional substance solution used is, from the viewpoint of efficiently encapsulating the functional substance in the carrier cellulose particles, preferably 300 parts by mass or more, more preferably 500 parts by mass or more, and even more preferably 700 parts by mass or more, relative to 100 parts by mass of the functional substance, and from the viewpoint of economy and productivity, preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, and even more preferably 1200 parts by mass or less. And, from the same viewpoint as above, the amount of organic solvent used here is, from the same viewpoint, preferably 300 parts by mass or more and 2000 parts by mass or less, more preferably 500 parts by mass or more and 1500 parts by mass or less, and even more preferably 700 parts by mass or more and 1200 parts by mass or less, relative to 100 parts by mass of the functional substance.

[0122] Next, the carrier cellulose particles are mixed with the prepared functional substance dispersion or functional substance solution. The amount of functional substance dispersion or functional substance solution used in this mixing is preferably 500 parts by mass or more, more preferably 700 parts by mass or more, relative to 100 parts by mass of the carrier cellulose particles to be mixed, from the viewpoint of improving the release of the functional substance and the deformability of the composite cellulose particles. Also, from the viewpoint of improving the encapsulation stability of the functional substance, it is preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, even more preferably 1200 parts by mass or less. From the same viewpoint, the amount of functional substance dispersion or functional substance solution is preferably 500 parts by mass or more and 2000 parts by mass or less, more preferably 700 parts by mass or more and 1500 parts by mass or less, even more preferably 700 parts by mass or more and 1200 parts by mass or less. In the case of a functional substance solution, the above range is particularly preferable. Furthermore, when the functional substance is an inorganic substance or a functional substance dispersion, the amount of functional substance dispersion used in this mixing is preferably 80 parts by mass or more, more preferably 100 parts by mass or more, and even more preferably 200 parts by mass or more, per 100 parts by mass of the carrier cellulose particles to be mixed, from the viewpoint of improving the release property of the functional substance and the deformability of the composite cellulose particles, and from the viewpoint of improving the encapsulation stability of the functional substance, is preferably 700 parts by mass or less, more preferably 500 parts by mass or less, and even more preferably 400 parts by mass or less.

[0123] The mixing of the carrier cellulose particles and the functional substance dispersion or functional substance solution can be carried out, for example, by stirring using a known device. The stirring speed during this mixing is preferably 100 rpm or more, more preferably 200 rpm or more, from the viewpoint of fully incorporating the functional substance into the carrier cellulose, and from the viewpoint of economy and productivity, it is preferably 2000 rpm or less, more preferably 1500 rpm or less, even more preferably 1000 rpm or less, and even more preferably 800 rpm or less. The stirring speed during mixing is, from the same viewpoint as above, preferably 100 rpm or more and 2000 rpm or less, more preferably 200 rpm or more and 1500 rpm or less, even more preferably 200 rpm or more and 1000 rpm or less, and even more preferably 200 rpm or more and 800 rpm or less.

[0124] The stirring time of the carrier cellulose particles and the functional substance dispersion or functional substance solution is preferably 0.2 hours or more, more preferably 0.5 hours or more, and even more preferably 0.8 hours or more, from the viewpoint of fully incorporating the functional substance into the carrier cellulose, and is preferably 12 hours or less, more preferably 6 hours or less, and even more preferably 3 hours or less, from the viewpoints of economy and productivity. From the same viewpoints as above, this stirring time is preferably 0.2 hours or more and 12 hours or less, more preferably 0.5 hours or more and 6 hours or less, and even more preferably 0.8 hours or more and 3 hours or less.

[0125] The cellulose carrier particles are thoroughly mixed with a functional substance dispersion or a functional substance solution, the functional substance dispersion or the functional substance solution is impregnated into the cellulose carrier particles, and the organic solvent is then removed to obtain composite cellulose particles containing the functional substance. The organic solvent is then removed by a drying treatment, preferably by heat drying, vacuum drying, or a combination of these.

[0126] The heating temperature in the drying treatment may be a temperature equal to or higher than the boiling point of the organic solvent used. Specific temperature conditions are, from the viewpoint of rapidly reducing the remaining amount of solvent, preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, and even more preferably 70°C or higher; and, from the viewpoint of ease of temperature adjustment, preferably 110°C or lower, more preferably 100°C or lower, even more preferably 90°C or lower, and even more preferably 85°C or lower. From the same viewpoint, the heating temperature in the drying treatment is preferably 40°C or higher and 110°C or lower, more preferably 50°C or higher and 100°C or lower, even more preferably 60°C or higher and 90°C or lower, and even more preferably 70°C or higher and 85°C or lower. The pressure in the drying treatment may be any pressure that promotes the evaporation of the organic solvent used. Specific pressures are preferably 800 hPa or less, more preferably 700 hPa or less, even more preferably 600 hPa or less, even more preferably 500 hPa or less, and even more preferably 350 hPa or less. The lower limit may be a vacuum (0 hPa). Considering ease of pressure adjustment, it is preferably 10 hPa or more, more preferably 50 hPa or more, even more preferably 100 hPa or more, and even more preferably 150 hPa or more. When drying under reduced pressure, it can be performed at room temperature (25 ° C.), and the heating temperature and pressure may be combined to perform heating and reduced pressure drying.

[0127] <Step (4-2)> Step (4-2) is a step of obtaining composite cellulose particles by the following step (4-2a) or step (4-2b).

[0128] In step (4-2a), first, a carrier cellulose particle dispersion liquid in which carrier cellulose particles are dispersed is prepared. Here, the carrier cellulose particle dispersion liquid obtained in step (3-2) may be used as is, or the concentration may be appropriately adjusted. The content of solids (carrier cellulose particles) in the carrier cellulose particle dispersion liquid is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, from the viewpoint of enabling functional substances to be encapsulated by simple operations and efficiently encapsulating functional substances in the carrier cellulose particles. From the same viewpoint, it is preferably 6% by mass or less, more preferably 5% by mass or less, and even more preferably 4% by mass or less. From the same viewpoint, the content of solids in the carrier cellulose particle dispersion liquid is preferably 1% by mass or more and 6% by mass or less, more preferably 2% by mass or more and 5% by mass or less, and even more preferably 3% by mass or more and 4% by mass or less. From the same viewpoint, it is preferably 1% by mass or more and 6% by mass or less, more preferably 2% by mass or more and 5% by mass or less, and even more preferably 3% by mass or more and 4% by mass or less.

[0129] Next, in step (4-2a), the carrier cellulose particle dispersion and a functional substance are mixed. The functional substance used is the functional substance described above for the composite cellulose particles. In step (4-2a), the dehydrated cellulose particle dispersion contains a sufficient amount of azeotropic solvent to disperse or dissolve the functional substance. Therefore, mixing may be performed using the functional substance dispersion or functional substance solution from step (4-1), or the functional substance may be mixed directly into the carrier cellulose particle dispersion without using an organic solvent. That is, by this mixing, the functional substance is dispersed or dissolved in the carrier cellulose particle dispersion in which the carrier cellulose particles are dispersed. When a functional substance dispersion or functional substance solution is used in this step, it is preferable that the organic solvent be the same as the azeotropic solvent used in step (3-2).

[0130] In this step (4-2a), the amount of functional substance used may be determined depending on the content of the functional substance to be contained in the composite cellulose particles and its content under the production conditions. That is, at least the amount of functional substance desired to be contained in the composite cellulose particles is used and mixed with the carrier cellulose particle dispersion. In the method for producing composite cellulose particles of the present invention, the functional substance can be encapsulated in the composite cellulose particles at a relatively high ratio. Therefore, the amount of functional substance used is preferably in the range from the same amount to an excess of about 10% by mass relative to the amount desired to be contained in the composite cellulose particles.

[0131] The dispersion of carrier cellulose particles and the functional substance can be mixed under the same conditions as those for the device, stirring speed, and stirring time described in step (4-1).

[0132] The carrier cellulose particle dispersion and the functional substance are thoroughly mixed to impregnate the carrier cellulose particles with the functional substance, and then the solvent containing the azeotropic solvent used in step (3-2) is removed to obtain composite cellulose particles containing the functional substance. The solvent containing the azeotropic solvent is removed by a drying treatment, preferably by heat drying, vacuum drying, or a combination of these, namely, heat and vacuum drying.

[0133] That is, the heating temperature in the treatment for removing a solvent containing an azeotropic solvent may be a temperature equal to or higher than the azeotropic point of the azeotropic solvent used, or, if an organic solvent other than the azeotropic solvent is used, a temperature equal to or higher than the boiling point of the organic solvent. Specific temperature conditions are preferably 30°C or higher, more preferably 40°C or higher, even more preferably 50°C or higher, and even more preferably 60°C or higher, from the viewpoint of rapidly reducing the amount of remaining solvent. Furthermore, from the viewpoint of ease of temperature control, the heating temperature is preferably 30°C or higher and 90°C or lower, more preferably 40°C or higher and 90°C or lower, even more preferably 50°C or higher and 90°C or lower, and even more preferably 60°C or higher and 85°C or lower. From the same viewpoint, the heating temperature is preferably 30°C or higher and 90°C or lower, more preferably 40°C or higher and 90°C or lower, even more preferably 50°C or higher and 90°C or lower, and even more preferably 60°C or higher and 85°C or lower. The pressure in the drying treatment may be any pressure that promotes the evaporation of the solvent, including the azeotropic solvent used. Specific pressures are preferably 800 hPa or less, more preferably 700 hPa or less, even more preferably 600 hPa or less, even more preferably 500 hPa or less, and even more preferably 350 hPa or less. The lower limit may be a vacuum (0 hPa). Considering ease of pressure adjustment, it is preferably 10 hPa or more, more preferably 50 hPa or more, even more preferably 100 hPa or more, and even more preferably 150 hPa or more. When drying under reduced pressure, it can be performed at room temperature (25 ° C.), and the heating temperature and pressure may be combined to perform heating and reduced pressure drying.

[0134] In step (4-2b), a cake is first prepared by solid-liquid separation of the carrier cellulose particle dispersion in which carrier cellulose particles are dispersed. The cake obtained by solid-liquid separation of the dispersion may be obtained by a known solid-liquid separation method from the carrier cellulose particle dispersion obtained in step (3-2). The solid-liquid separation performed here may be performed, for example, by centrifugation, filtration, decantation, or a combination thereof. The cake obtained here contains the azeotropic solvent and carrier cellulose particles used in step (3-2). This cake contains a relatively large amount of azeotropic solvent so that the functional substance can be efficiently encapsulated in the carrier cellulose particles by subsequent mixing with the functional substance. That is, the content of the solid component (dehydrated cellulose particles) in the cake is preferably 5% by mass or more, more preferably 6% by mass or more, and even more preferably 7% by mass or more, from the viewpoint of efficiently encapsulating the functional substance in the carrier cellulose particles. From the same viewpoint, it is preferably 20% by mass or less, more preferably 18% by mass or less, and even more preferably 15% by mass or less. From the same viewpoint as above, the content of the solid component in the cake is preferably 5% by mass or more and 20% by mass or less, more preferably 6% by mass or more and 18% by mass or less, and even more preferably 7% by mass or more and 15% by mass or less.

[0135] Next, in step (4-2b), the cake is mixed with a functional substance. The functional substance used is the functional substance described in the description of the composite cellulose particles. In step (4-2b), since the cake contains a sufficient amount of azeotropic solvent to disperse or dissolve the functional substance, the functional substance dispersion or functional substance solution of step (4-1) may be used for mixing, or the functional substance may be mixed directly into the cake without using an organic solvent. In other words, the functional substance is dispersed or dissolved in the cake by this mixing. When a functional substance dispersion or functional substance solution is used in this step, it is preferable that the organic solvent be the same as the azeotropic solvent used in step (3-2).

[0136] In this step (4-2b), the amount of the functional substance used can be the same as that described in step (4-2a). In addition, the cake and the functional substance can be mixed under the same conditions as those described in step (4-2a), such as the apparatus, stirring speed, and stirring time.

[0137] The cake and the functional substance are thoroughly mixed to impregnate the carrier cellulose particles with the functional substance, and then the solvent containing the azeotropic solvent is removed to obtain composite cellulose particles containing the functional substance. The solvent containing the azeotropic solvent is removed by a drying treatment, preferably by heat drying, vacuum drying, or a combination of these.

[0138] [Uses] The composite cellulose particles of the present invention can be incorporated into or used in, for example, cosmetics, toiletries, oral care products, quasi-drugs, pharmaceuticals, household products, agricultural products, etc. Furthermore, since the composite cellulose particles of the present invention are made from cellulose derived from natural plants, they are environmentally friendly and can be suitably used as an alternative material to microplastics. Among these, use as cosmetics, which require a good feel to the touch, is preferred.

[0139] <Cosmetics> The present invention further provides a cosmetic comprising the composite cellulose particles. By including the composite cellulose particles, the cosmetic of the present invention can impart a pleasant feel to the skin. Furthermore, since the composite cellulose particles also have excellent encapsulation stability of functional substances and excellent release properties of functional substances, a cosmetic comprising the composite cellulose particles can effectively release functional substances to a target object by application. From the viewpoint of effectively achieving the above-described effects, the cosmetic of the present invention is preferably a skin cosmetic. Examples of such skin cosmetic include foundations, makeup bases, sunscreens, emulsions, lotions, and the like. The content of the composite cellulose particles in the cosmetic need only be an amount that can exhibit the desired performance and can be selected appropriately depending on the type, form, etc. of the cosmetic, but is typically in the range of 0.01% by mass or more and 80% by mass or less in the cosmetic.

[0140] In addition to the above-described embodiments, the present invention discloses the following. <1> Composite cellulose particles containing cellulose and a functional substance, wherein the composite cellulose particles have a compressive modulus of 50 MPa or less and an elastic recovery rate of less than 5%. <2> The composite cellulose particles according to <1>, wherein some or all of the cellulose is particulate cellulose, and at least a portion of the functional substance is contained within the particulate cellulose. <3> The composite cellulose particles according to <1> or <2>, wherein the compressive modulus of the composite cellulose particles is 50 MPa or less, preferably 10 MPa or less, more preferably 6.0 MPa or less, preferably 0.9 MPa or more, more preferably 1.5 MPa or more, even more preferably 2.3 MPa or more, and preferably 0.9 MPa to 50 MPa, more preferably 1.5 MPa to 10 MPa, even more preferably 2.3 MPa to 6.0 MPa. <4> The composite cellulose particles according to any one of <1> to <3>, wherein the composite cellulose particles have an elastic recovery of less than 5%, preferably 4% or less, more preferably 1.7% or less, or 0% or more, preferably 0.2% or more, more preferably 0.8% or more, and 0% or more but less than 5%, preferably 0.2% or more and 4%, more preferably 0.8% or more and 1.7% or less. <5> The composite cellulose particles according to any one of <1> to <4>, wherein the composite cellulose particles have a compressive modulus of 0.9 MPa to 50 MPa and an elastic recovery of 0.2% to 4%. <6> The composite cellulose particles according to any one of <1> to <4>, wherein the composite cellulose particles have a compressive modulus of 1.5 MPa to 10 MPa and an elastic recovery of 0.4% to 3%. <7> The composite cellulose particles according to any one of <1> to <4>, having a compressive modulus of 1.9 MPa or more and 7.5 MPa or less, and an elastic recovery rate of 0.6% or more and 2% or less. <8> The composite cellulose particles according to any one of <1> to <4>, having a compressive modulus of 20 MPa or less, and an elastic recovery rate of less than 5%.<9> The composite cellulose particles according to any one of <1> to <8>, wherein the content of the functional substance is 10 parts by mass or more and 500 parts by mass or less relative to 100 parts by mass of the cellulose. <10> The composite cellulose particles according to any one of <1> to <9>, wherein the content of the functional substance is preferably 10 parts by mass or more, more preferably 100 parts by mass or more, even more preferably 200 parts by mass or more, and preferably 600 parts by mass or less, more preferably 500 parts by mass or less, and even more preferably 400 parts by mass or less, relative to 100 parts by mass of the cellulose. <11> The composite cellulose particles according to <10>, wherein the content of the functional substance is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 25 parts by mass or more, relative to 100 parts by mass of the cellulose, and is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 50 parts by mass or less, and is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 80 parts by mass or less, and even more preferably 25 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the cellulose. <12> The composite cellulose particles according to <10>, wherein the content of the functional substance is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, even more preferably 250 parts by mass or more, and preferably 600 parts by mass or less, more preferably 450 parts by mass or less, and even more preferably 400 parts by mass or less, relative to 100 parts by mass of the cellulose. <13> The composite cellulose particles according to any of <10> to <12>, wherein the content of the functional substance is 10 parts by mass or more and 600 parts by mass or less, more preferably 200 parts by mass or more and 450 parts by mass or less, and even more preferably 400 parts by mass or less, relative to 100 parts by mass of the cellulose. <13> The composite cellulose particles according to any of <10> to <12>, wherein the content of the functional substance is 10 parts by mass or more and 600 parts by mass or less, relative to 100 parts by mass of the cellulose.<14> The composite cellulose particles according to any one of <10> to <13>, wherein the composite cellulose particles have a compressive modulus of 1.5 MPa to 10 MPa, an elastic recovery of 0.4% to 3%, and a content of the functional substance of 30 parts by mass to 500 parts by mass per 100 parts by mass of the cellulose. <15> The composite cellulose particles according to any one of <10> to <14>, wherein the composite cellulose particles have a compressive modulus of 1.9 MPa to 7.5 MPa, an elastic recovery of 0.6% to 2%, and a content of the functional substance of 50 parts by mass to 450 parts by mass per 100 parts by mass of the cellulose. <16> The composite cellulose particles according to <10> or <12>, wherein the composite cellulose particles have a compressive modulus of 20 MPa or less, an elastic recovery of less than 5%, and a content of the functional substance of 100 parts by mass to 600 parts by mass. <17> The composite cellulose particle according to any one of <1> to <16>, wherein the functional substance comprises at least one selected from the group consisting of silicone, fatty acid, ester oil, alcohol, nonionic polymer, organic acid having 8 or less carbon atoms, and chroman derivative. <18> The composite cellulose particle according to <17>, wherein the functional substance is at least one selected from the group consisting of silicone, fatty acid, ester oil, alcohol, nonionic polymer, organic acid having 8 or less carbon atoms, and chroman derivative, and the composite cellulose particle has a compressive modulus of 0.9 MPa to 50 MPa and an elastic recovery rate of 0.2% to 4%, and the content of the functional substance is 10 parts by mass to 600 parts by mass per 100 parts by mass of the cellulose. <19> The composite cellulose particles according to <17> or <18>, wherein the functional substance is one or more selected from the group consisting of silicone, fatty acid, ester oil, alcohol, and chroman derivative, the composite cellulose particles have a compressive modulus of 1.5 MPa to 10 MPa and an elastic recovery rate of 0.4% to 3%, and the content of the functional substance is 30 parts by mass to 500 parts by mass relative to 100 parts by mass of the cellulose.<20> The composite cellulose particles according to any one of <17> to <19>, wherein the functional substance is one or more selected from the group consisting of silicone, fatty acid, and chroman derivative, and the composite cellulose particles have a compressive modulus of 1.9 MPa to 7.5 MPa and an elastic recovery of 0.6% to 2%, and the content of the functional substance is 50 parts by mass to 450 parts by mass per 100 parts by mass of the cellulose. <21> The composite cellulose particles according to <17>, wherein the functional substance is silicone, and the composite cellulose particles have a compressive modulus of 20 MPa or less and an elastic recovery of less than 5%, and the content of the functional substance is 100 parts by mass to 500 parts by mass. <22> The composite cellulose particles according to any one of <1> to <21>, wherein the median diameter of the composite cellulose particles is 5 μm to 2,000 μm. <23> The median diameter (D ５０) is preferably 2000 μm or less, more preferably 110 μm or less, even more preferably 100 μm or less, preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and is preferably 5 μm or more and 2000 μm or less, more preferably 10 μm or more and 110 μm or less, even more preferably 15 μm or more and 100 μm or less. <24> The composite cellulose particles according to <22> or <23>, wherein the functional substance is at least one selected from the group consisting of silicone, fatty acid, ester oil, alcohol, nonionic polymer, organic acid having 8 or less carbon atoms, and chroman derivative; the composite cellulose particles have a compressive modulus of 0.9 MPa to 50 MPa, an elastic recovery of 0.2% to 4%, and a median diameter of 5 μm to 250 μm; and the content of the functional substance is 10 parts by mass to 600 parts by mass relative to 100 parts by mass of the cellulose. <25> The composite cellulose particles according to any one of <22> to <24>, wherein the functional substance is at least one selected from the group consisting of silicone, fatty acid, ester oil, and chroman derivative; the composite cellulose particles have a compressive modulus of 1.5 MPa to 10 MPa, an elastic recovery of 0.4% to 3%, and a median diameter of 5 μm to 200 μm; and the content of the functional substance is 30 parts by mass to 500 parts by mass relative to 100 parts by mass of the cellulose. <26> The composite cellulose particles according to any one of <22> to <25>, wherein the functional substance is at least one selected from the group consisting of silicone, fatty acid, and chroman derivative, the composite cellulose particles have a compressive modulus of 1.9 MPa to 7.5 MPa, an elastic recovery of 0.6% to 2%, a median diameter of 5 μm to 150 μm, and a content of the functional substance of 50 parts by mass to 450 parts by mass per 100 parts by mass of the cellulose.<27> The composite cellulose particles according to <22> or <23>, wherein the functional substance is silicone, the composite cellulose particles have a compressive modulus of 20 MPa or less, an elastic recovery rate of less than 5%, a median diameter of 10 μm to 100 μm, and a content of the functional substance of 100 parts by mass to 500 parts by mass. <28> The composite cellulose particles according to any of <1> to <27>, wherein the functional substance comprises inorganic particles having an average particle size of less than 400 nm. <29> The composite cellulose particles according to <28>, wherein the average particle size is preferably less than 400 nm, more preferably 350 nm or less, even more preferably 200 nm or less, preferably 20 nm or more, more preferably 50 nm or more, even more preferably 100 nm or more, and preferably 20 nm or more but less than 400 nm, more preferably 50 nm or more but 350 nm, even more preferably 100 nm or more. <30> The composite cellulose particle according to <28> or <29>, wherein the functional substance is one or more selected from the group consisting of zinc oxide, titanium oxide, barium sulfate, calcium carbonate, talc, mica, and titanium oxide-coated mica. <31> The composite cellulose particle according to any one of <28> to <30>, wherein the functional substance is one or more selected from the group consisting of zinc oxide, titanium oxide, barium sulfate, calcium carbonate, talc, mica, and titanium oxide-coated mica, and wherein the average particle size is 20 nm or more and less than 400 nm. <32> The composite cellulose particle according to any one of <28> to <31>, wherein the functional substance is one or more selected from the group consisting of zinc oxide and titanium oxide, and wherein the average particle size is 50 nm or more and less than 300 nm. <33> The composite cellulose particle according to any one of <28> to <32>, wherein the functional substance is zinc oxide, and wherein the average particle size is 80 nm or more and less than 250 nm. <34> A cosmetic comprising the composite cellulose particles according to any one of <1> to <33>. <35> Use of the composite cellulose particles according to any one of <1> to <33> as a cosmetic. <36> A method for producing composite cellulose particles, comprising the following steps (1) to (4) in this order:Step (1): A step of mixing a water-in-oil cellulose emulsion containing cellulose, water, and an organic solvent with a cellulose non-solvent to precipitate coarse cellulose particles and obtain a suspension containing the coarse cellulose particles. Step (2): A step of subjecting the suspension containing the coarse cellulose particles obtained in step (1) to solid-liquid separation, and then washing the obtained coarse cellulose wet particles to obtain purified cellulose wet particles. Step (3): A step of obtaining carrier cellulose particles or a carrier cellulose particle dispersion by the following step (3-1) or step (3-2). Step (3-1): A step of drying the purified cellulose wet particles obtained in step (2) to obtain dried cellulose particles as carrier cellulose particles. Step (3-2): A step of mixing the purified cellulose wet particles obtained in step (2) with an azeotropic solvent having an azeotropic point with water, and distilling off the water contained in the purified cellulose wet particles by azeotropy to obtain a dehydrated cellulose particle dispersion in which dehydrated cellulose particles are dispersed in the azeotropic solvent as a carrier cellulose particle dispersion. Step (4): A step of obtaining composite cellulose particles by the following step (4-1) or step (4-2). Step (4-1): A step of mixing the carrier cellulose particles obtained in the step (3-1) with a functional substance dispersion liquid in which a functional substance is dispersed in an organic solvent or a functional substance solution in which a functional substance is dissolved in an organic solvent, and then removing the organic solvent to obtain composite cellulose particles containing the functional substance. Step (4-2): A step of obtaining composite cellulose particles by step (4-2a) or step (4-2b). Step (4-2a): A step of mixing the carrier cellulose particle dispersion liquid obtained in the step (3-2) with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2) to obtain composite cellulose particles containing the functional substance. Step (4-2b): A step of obtaining composite cellulose particles containing the functional substance by subjecting the carrier cellulose particle dispersion obtained in the step (3-2) to solid-liquid separation to obtain a cake, mixing the cake with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2) to obtain composite cellulose particles containing the functional substance. <37> The method for producing composite cellulose particles according to <36>, wherein the functional substance used in the step (4-2a) is a functional substance without being pretreated.<38> The method for producing composite cellulose particles according to <36>, wherein the functional substance used in the step (4-2a) is a functional substance dispersion obtained by dispersing a functional substance in an organic solvent, or a functional substance solution obtained by dissolving a functional substance in an organic solvent. <39> The method for producing composite cellulose particles according to <36>, wherein the functional substance used in the step (4-2b) is a functional substance without pretreatment. <40> The method for producing composite cellulose particles according to <36>, wherein the functional substance used in the step (4-2b) is a functional substance dispersion obtained by dispersing a functional substance in an organic solvent, or a functional substance solution obtained by dissolving a functional substance in an organic solvent. <41> The method for producing composite cellulose particles according to any of <36> to <40>, wherein the water-in-oil cellulose emulsion containing cellulose, water, and an organic solvent is obtained by carrying out the following steps (1-1) and (1-2): Step (1-1): A step of mixing a raw material cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution. Step (1-2): A step of mixing the cellulose aqueous solution obtained in the step (1-1) with an organic solvent to prepare a cellulose emulsion. <42> The method for producing composite cellulose particles according to any one of <36> to <41>, wherein the step (1) comprises the following steps (1-1) to (1-3) in this order: <44> The method for producing composite cellulose particles according to any one of <36> to <43>, further comprising, after the step (2) and before the step (3-2), a substitution step of bringing the purified wet cellulose particles obtained in the step (2) into contact with an azeotropic solvent having an azeotropic point with water for substitution, wherein the azeotropic point is 30°C or higher and 90°C or lower.<45> The method for producing composite cellulose particles according to any one of <36> to <44>, wherein an acid is added to the suspension containing the crude cellulose particles after the step (1) and before the step (2) to neutralize the suspension. <46> The method for producing composite cellulose particles according to any one of <36> to <45>, wherein in the step (4-2a), the content of the carrier cellulose particles in the carrier cellulose particle dispersion is 1% by mass or more and 6% by mass or less. <47> The method for producing composite cellulose particles according to any one of <36> to <45>, wherein in the step (4-2b), the content of the carrier cellulose particles in the cake is 5% by mass or more and 20% by mass or less. <48> The method for producing composite cellulose particles according to any one of <36> to <47>, wherein the functional substance used in the step (4) is an organic substance soluble in the azeotropic solvent used in the step (3), or an organic or inorganic substance dispersible in the azeotropic solvent. <49> The method for producing composite cellulose particles according to any one of <36> to <48>, wherein the carrier cellulose particles are porous cellulose particles. <50> The method for producing composite cellulose particles according to any one of <36> to <49>, wherein at least a part of the functional substance is contained in the carrier cellulose particles.

[0141] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Various measurement and evaluation methods are as follows. Unless otherwise specified, particle size refers to the diameter of the particle.

[0142] <Compressive Elastic Modulus of Particles> The compressive elastic modulus of particles is measured using a micro-compression tester ("MCT-510" manufactured by Shimadzu Corporation), and the average value is calculated as the measurement result according to the following procedure. 1. Particles are placed on a measurement stage attached to the device, and the particle size d (mm) is measured. 2. An indenter (Φ50 μm) is pressed against the particle at a constant loading speed (4.5 × 10 －６ N / sec), and the test force P (N) reaches the specified value (9.8 × 10 －４ The particles are compressed (displacement x (mm)) until the particle size d (mm) and test force P (N) are reached. 3. The compressive stress is calculated using the following formula from the particle size d (mm) and test force P (N): Compressive stress (MPa) = 2.48 x P (N) / (π x (d (mm))２ ) 4. Calculate the compressive strain from the displacement x (mm) and particle size d (mm) using the following formula: Compressive strain (%) = x (mm) / d (mm) x 100 5. Create a stress-strain curve from the calculated compressive stress and compressive strain, and calculate the compressive modulus (MPa) from the slope of the elastic region (0-10%). 6. Repeat steps 1 to 5 above seven times, and use the arithmetic average of the five obtained compressive modulus values ​​excluding the maximum and minimum values ​​as the measurement result of the compressive modulus of the particles.

[0143] <Elastic recovery rate of particles> The elastic recovery rate of particles is measured using a micro-compression tester ("MCT-510" manufactured by Shimadzu Corporation), and the average value is calculated as the measurement result according to the following procedure. 1. Particles are placed on the measurement stage attached to the device, and the particle size d (mm) is measured. 2. An indenter (Φ50 μm) is pressed against the surface at a constant loading speed (4.5 × 10 －６ N / sec) and the specified test force (9.8 × 10 －４ A load is applied to compress the particles (indenter displacement x (mm)) until the load reaches the minimum test force (0 N). Then, the load is released (indenter displacement y (mm)) until the load reaches the minimum test force (0 N). Note that the indenter displacements x and y represent positions based on the point where the indenter first contacts the particle. 3. The elastic recovery rate is calculated as the displacement x (mm) caused by the load and the displacement x recovered after the load is released. １ (mm) (x １ = x - y) and calculate using the following formula: Elastic recovery rate (%) = x １ (mm) / x (mm) x 100 4. Repeat steps 1 to 3 seven times, and use the arithmetic mean value of the five measurements excluding the maximum and minimum elastic recovery values ​​as the measurement result of the elastic recovery of the particles.

[0144] <Median diameter of particles> The median diameter of particles (D ５０ The particle size distribution and volume frequency distribution are determined using a dynamic image analyzer (CAMSIZER X2, manufactured by MICROTRAC MRB). Specifically, 20 mg of dried particles are fed into the device feeder, dispersed at an air dispersion pressure of 30 kPa, and 10,000 images are measured in the dynamic image analyzer to determine the cumulative particle size distribution and volume frequency distribution. The particle size at which the cumulative value reaches 50% is calculated as the median size.

[0145] <Particle Pore Volume> The particle pore volume is measured by the mercury intrusion method using a mercury porosimeter (Shimadzu Corporation, "Auto Pore IV 9500") as follows: 1. Approximately 0.05 g (Y (g)) of particles is placed in the cell of the mercury porosimeter. 2. Mercury is inject|pressurized into the particle, and the value of the volume Z (mL) of mercury which penetrates into the pores in the particle and the gaps between the particles is calculated in the measurement pressure range of 0.01 MPa to 210 MPa. 3. The value obtained by the following formula from the mass Y (g) of the particle and the volume Z (mL) of the penetrated mercury is regarded as the measurement result of the particle pore volume (mL). Pore volume (mL / g) = Z (mL) / Y (g)

[0146] <Specific Surface Area of ​​Carrier Cellulose Particles> The specific surface area of ​​the carrier cellulose particles is measured by the mercury intrusion method using a mercury porosimeter ("Auto Pore IV 9500" manufactured by Shimadzu Corporation) as follows. 1. Approximately 0.05 g (Y(g)) of particles is placed in the cell of the mercury porosimeter. 2. Mercury is inject|pressurized into the particle, and the total value X (m ２ 3. Determine the mass Y (g) of the particle and the total surface area X (m ２ ) and the value obtained by the following formula is used as the specific surface area (m ２ / g) is the measurement result. ２ / g) = X(m ２ ) / Y(g)

[0147] <Surface pore diameter of carrier cellulose particles> The surface pore diameter of carrier cellulose particles is measured by mercury intrusion porosimetry using a mercury porosimeter (Shimadzu Corporation, "Auto Pore IV 9500") according to the following method. 1. The pore volume of the particle is determined by the method described above, and the horizontal axis is plotted with the pore diameter (nm) and the vertical axis with the pore volume (mL / g) to obtain an integrated pore distribution curve. 2. The (integral) pore volume is differentiated by the pore diameter, i.e., the increase in pore volume at each pore diameter is taken as the differential pore volume (mL / g), and the horizontal axis is plotted with the pore diameter (nm) and the vertical axis is plotted with the differential pore volume (mL / g) to obtain a pore distribution curve. 3. In the obtained pore distribution curve, the mode of pore diameters in the pore diameter range of 1000 nm or less is taken as the surface pore diameter (nm) of the particle.

[0148] <Average particle size of functional substance in dispersion> The average particle size of the functional substance in the dispersion is measured using a Zetasizer measuring device ("Zetasizer Nano ZS" manufactured by Malvern) according to the following procedure. 1. 0.5 g of functional substance is mixed with 49.5 g of dispersion medium to prepare a functional substance dispersion. 2. The functional substance dispersion is placed in the measurement container of the aforementioned measuring device and measured by dynamic light scattering (DLS) to obtain the volume distribution of particle sizes. 3. The particle size at 50% of the volume distribution of particle sizes (nm) obtained is taken as the measurement result of the average particle size (nm) of the functional substance in the dispersion.

[0149] <Content> The content of the functional substance in the composite cellulose particles is evaluated by extraction using a solvent capable of dissolving the functional substance. Specifically, 1 g of composite cellulose particles is dispersed in 7.5 g of 2-propanol and shaken for 1 hour to dissolve the functional substance. The solution containing the functional substance is then filtered through a filter (Advantec "T100A090C") to separate it into a supernatant and an insoluble fraction. The amount of functional substance in the resulting supernatant is quantified by loss on drying. The content (%) is calculated from the ratio of the amount quantified by extraction of the functional substance to the amount charged during production.

[0150] <Encapsulation Stability> The encapsulation stability of composite cellulose particles is evaluated by the proportion of coarse aggregates with a particle size of 400% or more of the carrier cellulose particles before composite to the total volume of the powder after composite. The proportion of coarse aggregates is measured using a dynamic image analyzer (CAMSIZER X2 manufactured by MICROTRACK MRB). Specifically, approximately 20 mg of composite cellulose particles are fed into the device feeder, and the particles are dispersed at an air dispersion pressure of 30 kPa. The particle size distribution is calculated from the obtained 10,000 images, and the volume fraction (volume %) of fractions with particle sizes of 400% or more of the carrier cellulose particles before composite is taken as the amount of aggregates.

[0151] <Particle Deformability> Particle deformability is evaluated by the following procedure. 1. Approximately 20 mg of particles are weighed and placed on artificial leather (Laforet S2923, 5 cm x 4 cm). 2. Using a surface property tester ("Tribogear TYPE 14" manufactured by Shinto Scientific Co., Ltd.), a vertical load of 200 g, equivalent to a coating operation, is applied, and the particles are rubbed back and forth 20 times at a travel distance of 50 mm and a travel speed of 2000 mm / min. 3. The particles remaining on the artificial leather surface are observed using a scanning electron microscope ("SEM" manufactured by JEOL Ltd., "JSM-IT-500HR") at an acceleration voltage of 5.0 kV and an observation magnification of 500x. 4. Of the 20 composite cellulose particles in the observed image, the proportion of particles that have been flattened (deformed) by rubbing is calculated as the deformation rate, and the result is scored according to the following criteria to obtain the evaluation result. 5: 80% or more, 4: 60% or more but less than 80%, 3: 40% or more but less than 60%, 2: 20% or more but less than 40%, 1: Less than 20%

[0152] <Release of functional substance> The release of functional substances due to deformation of composite cellulose particles (also simply referred to as release) is confirmed by examining elements specific to the functional substance using energy dispersive X-ray spectroscopy (SEM-EDX). 1. Composite cellulose particles are applied to the surface of an artificial leather substrate and rubbed using the same procedure as for "particle deformability". 2. Using a scanning electron microscope (SEM, "JSM-IT-500HR" manufactured by JEOL Ltd.), elemental mapping or point analysis is performed on the artificial leather substrate surface by SEM-EDX at an acceleration voltage of 15 kV and an observation magnification of 500x. 3. It is confirmed whether elements specific to the functional substance are detected on the rubbed artificial leather substrate surface, and the following evaluation is given. Y: Element was detected, N: Element was not detected. This evaluation shows that when composite cellulose particles having a deformability of a compressive modulus of elasticity of 50 MPa or less are used, when a functional substance is transferred onto an artificial leather substrate through repeated deformation and rubbing of the particles, elements specific to the functional substance are detected on the substrate, confirming that the functional substance has been released.

[0153] <Average Degree of Polymerization of Raw Cellulose> The average degree of polymerization of raw cellulose is measured as follows. [Preparation of Measurement Solution] 0.1 g (dry mass) of cellulose to be measured is precisely weighed out and placed in a 50 mL volumetric flask, and 0.5 M cuprammonium solution is added to make up to 50 mL. This solution is stirred overnight until the cellulose is completely dissolved, to prepare a measurement solution. [Measurement of Average Degree of Polymerization] The measurement solution obtained above is placed in an Ubbelohde viscometer (TV-3SL, manufactured by Thomas Scientific Instruments Co., Ltd., viscosity coefficient = 0.03113), and allowed to stand in a thermostatic bath (20 ± 0.2°C) for 1 hour, after which the flow time of the liquid is measured. The flow time (t (seconds)) of cuprammonium solutions with various cellulose concentrations (g / dL) and the flow time (t ０ (sec)) and the relative viscosity η ｒ η ｒ = t / t ０ Next, the reduced viscosity (η ｓｐ / c) is calculated using the following formula: ｓｐ / c=(η ｒ−1) / c (c: cellulose concentration (g / dL)) Furthermore, the reduced viscosity is extrapolated to c=0 to determine the intrinsic viscosity [η] (dL / g), and the average degree of polymerization is calculated using the following formula: Average degree of polymerization=2000×[η]

[0154] <Production Example 1> (Production of Carrier Cellulose Particles 1) (Step (1)) <Step (1-1)> As the starting cellulose, cellulose type I crystalline cellulose powder ("CEOLUS FD-101" manufactured by Asahi Kasei Corporation, degree of polymerization: 170, median diameter: 50 μm, moisture content: 6%) was used. 17.5 g of the cellulose powder was added to 182.5 g of a dilute aqueous NaOH solution (NaOH concentration: 4.2% by mass) and cooled to -2°C. Thereafter, while maintaining the temperature at -2°C, 50 g of a concentrated aqueous NaOH solution (NaOH concentration: 22% by mass) was added and stirred for 1 hour to dissolve the starting cellulose, thereby obtaining an aqueous cellulose solution. The cellulose concentration in the obtained aqueous cellulose solution was 7% by mass, and the NaOH concentration was 7.6% by mass.

[0155] <Step (1-2)> 350 g of isododecane and 3.5 g of an emulsifier, sucrose erucate ester (Ryoto Sugar Ester ER-290 manufactured by Mitsubishi Chemical Corporation, HLB: 2, monoester content: approximately 2%), were added to the aqueous cellulose solution. The mixture was emulsified by stirring at 5°C and 12,000 rpm for 5 minutes using a homomixer (MARK II 2.5 manufactured by Primix Corporation), to obtain a water-in-oil emulsion of cellulose. The emulsion droplet size was measured using a laser diffraction / scattering particle size distribution analyzer (LA-960V2 manufactured by Horiba, Ltd.) and found to be 25 μm.

[0156] <Step (1-3)> The entire amount of the obtained emulsion was added to 250 g of alcohol (methanol: ClogP -0.77), a non-solvent for cellulose, and the mixture was stirred at 400 rpm for 1 hour at room temperature (25°C) using a stirring blade to precipitate crude cellulose particles. Next, 42.8 g of acetic acid (1.5 equivalents relative to NaOH) was added to neutralize the mixture, yielding a suspension containing crude cellulose particles.

[0157] (Step (2)) The suspension obtained in step (1) was filtered under reduced pressure (700 hPa) using filter paper ("OMNIPORE DISC PTFE PHILIC 1.0 μM 90MM WH PLN 25 / PK" manufactured by Millipore, mesh size 1 μm) to perform solid-liquid separation. 2-Propanol (300 parts by mass relative to 100 parts by mass of wet cellulose particles) was added to the recovered wet particles, and the mixture was stirred at room temperature (25° C.) for 1 hour, followed by solid-liquid separation again. This operation was repeated twice. Next, water (300 parts by mass relative to 100 parts by mass of wet cellulose particles) was added to the recovered wet particles, and the mixture was stirred at room temperature (25° C.) for 1 hour, followed by solid-liquid separation again. This operation was repeated twice to obtain purified wet cellulose particles.

[0158] (Step (3-1)) The purified wet cellulose particles recovered in the step (2) were quickly frozen in a dry ice / ethyl alcohol bath at −72°C, and then subjected to primary drying at −10°C under a vacuum of 100 Pa or less to remove most of the water. After that, secondary drying was performed at 25°C while maintaining the reduced pressure to obtain dried cellulose particles (carrier cellulose particles 1).

[0159] <Production Example 2> (Production of carrier cellulose particles 2): Dried cellulose particles (carrier cellulose particles 2) were obtained in the same manner as in Production Example 1, except that in step (1), the homomixer rotation speed was changed to 5000 rpm and the emulsion droplet diameter was set to 84 μm.

[0160] <Production Example 3> (Production of carrier cellulose particles 3) Dried cellulose particles (carrier cellulose particles 3) were obtained in the same manner as in Production Example 1, except that in step (1), the homomixer rotation speed was changed to 4000 rpm and the emulsion droplet diameter of the emulsion was set to 105 μm.

[0161] The surface pore diameter, pore volume, specific surface area, compressive modulus, and median diameter of the dried cellulose particles (carrier cellulose particles 1 to 3) obtained in Production Examples 1 to 3 were evaluated by the methods described above, and the results are shown in Tables 1-1, 1-2, and 2.

[0162] <Production Example 4> (Production of Dehydrated Cellulose Particles) (Substitution Step) 170 g of purified wet cellulose particles (solid content: approximately 17 g) obtained by carrying out steps up to (2) in Production Example 1 were mixed with 350 g of 2-propanol and stirred for 5 minutes. Subsequently, solid-liquid separation was performed by filtration, and the water between and within the purified wet cellulose particles was substituted with 2-propanol. (Step (3-2)) Next, 170 g of purified wet cellulose particles (solid content: approximately 17 g) obtained by the substitution step were dispersed in 205 g of 2-propanol to obtain a 2-propanol dispersion. This 2-propanol dispersion was added to a 2-L stirring vessel and heated to 80°C in an oil bath. During this process, the 2-propanol and the water remaining in the purified wet cellulose particles obtained by the substitution step formed an azeotropic mixture. The vapor generated by the azeotropic mixture was cooled in a cooling tube and collected using a dropping funnel. After confirming that approximately 100 mL (100 cc) had accumulated in the dropping funnel, 2-propanol and water were removed from the dropping funnel. The same amount of 2-propanol as that removed was then added to the stirring tank. This procedure was repeated six times to remove the water from the cellulose, yielding a 2-propanol dispersion in which dehydrated cellulose particles were dispersed. Measurement using a laser diffraction / scattering particle size distribution analyzer ("LA-960" manufactured by Horiba, Ltd.) revealed that the median diameter of the dehydrated cellulose particles was 23.1 μm, as shown in Table 3.

[0163] Example 1-1 (Production and Evaluation of Composite Cellulose Particles) (Step (4-1)) Five grams of the dried cellulose particles (carrier cellulose particles 1) obtained in Production Example 1 were weighed and mixed with a solution prepared by dissolving approximately 5 grams of a functional substance, a modified polysiloxane represented by the following general formula (I) (manufactured by Kao Corporation), in 45 grams of ethanol. This mixture was stirred at room temperature for one hour and then dried under reduced pressure at 80°C and 250 hPa to remove the ethanol, yielding composite cellulose particles composed of 100 parts by mass of cellulose and 100 parts by mass of the modified polysiloxane. The compressive modulus, elastic recovery, and median diameter of the resulting composite cellulose particles, as well as the content, encapsulation stability, deformability, and release properties of the functional substance, were evaluated using the methods described above. The results are shown in Table 1-1. (In the formula, R １ and R ９are linear hydrocarbon groups having 16 to 18 carbon atoms, R ２ ~R ８ is a methyl group, R １０ and R １１ is a hydrogen atom, Q is a linear hydrocarbon group having 11 carbon atoms, p is the number of repeating units and has an average value of 25, and q is the number of repeating units and has an average value of 4.

[0164] Examples 1-2 to 1-38 Composite cellulose particles were produced in the same manner as in Example 1-1, except that the type and amount (charge amount) of the functional substance in Example 1-1 were changed as shown in Table 1-1. The compressive modulus, elastic recovery, and median diameter of the resulting composite cellulose particles, as well as the content, encapsulation stability, deformability, and release properties of the functional substance, were evaluated using the methods described above. The results are shown in Table 1-1.

[0165] Examples 1-39 to 1-44 Composite cellulose particles were produced in the same manner as in Example 1-1, except that the type of carrier cellulose particles and the amount (charge amount) of functional substance in Example 1-1 were changed as shown in Table 1-2. The compressive modulus, elastic recovery, and median diameter of the obtained composite cellulose particles, as well as the content, encapsulation stability, deformability, and release property of the functional substance, were evaluated by the methods described above, and the results are shown in Table 1-2.

[0166] Examples 1-45 to 1-50 In Example 1-1, the type and amount (charge amount) of the functional substance (medium-viscosity polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., "KF-96 20cs," "KF-96 1000cs," and "KF-96 12500cs")) were as shown in Table 1-2, a solution was prepared using low-viscosity polydimethylsiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., "KF-96 1cs") as the solvent, and the pressure during solvent removal was changed to 50 hPa. Except for this, composite cellulose particles were produced in the same manner as in Example 1-1. The compressive modulus, elastic recovery, and median diameter of the obtained composite cellulose particles, as well as the content, encapsulation stability, deformability, and releasability of the functional substance, were evaluated by the methods described above. The results are shown in Table 1-2.

[0167] Comparative Examples 1-1 to 1-4: Composite cellulose particles were produced in the same manner as in Example 1-1, except that commercially available cellulose particles listed in Table 1-2 were used as the carrier cellulose particles. The compressive modulus, elastic recovery, and median diameter of the resulting composite cellulose particles, as well as the content, encapsulation stability, deformability, and release properties of the functional substance, were measured and evaluated using the methods described above. The results are shown in Table 1-2. Comparative Example 1-5: 5 g of the dried cellulose particles (carrier cellulose particles 1) obtained in Production Example 1 were weighed and mixed with 45 g of ethanol. After stirring at room temperature for 1 hour, the mixture was dried under reduced pressure at 80°C and 250 hPa to remove the ethanol, yielding porous cellulose particles containing no functional substance. The compressive modulus, elastic recovery, median diameter, and deformability of the resulting composite cellulose particles were measured and evaluated using the methods described above. The results are shown in Table 1-2.

[0168]

[0169]

[0170] The functional substances used in Tables 1-1 and 1-2 are shown below. *1: Modified polysiloxane (SP value 13-14) *2: Oleic acid, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (SP value 17.7) *3: Tocopherol acetate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (SP value 18) *4: Isotridecyl isononanoate, "Salacos 913" manufactured by Nisshin Oillio Co., Ltd. (SP value 15.9) *5: Isopropyl palmitate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (SP value 18.7) *6: Polyethylene glycol 200, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (SP value 20) *7: Dipropylene glycol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (SP value 26) *8: 1,3-butylene glycol, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (SP value 29) * 9: Glycerin (SP value 35.7) * 10: Hydroxypropyl cellulose 1, Nippon Soda Co., Ltd. "HPC-SSL" (SP value 23.7) * 11: Hydroxypropyl cellulose 2, Nippon Soda Co., Ltd. "HPC-SL" (SP value 23.7) * 12: Hydroxypropyl cellulose 3, Nippon Soda Co., Ltd. "HPC-L" (SP value 23.7) * 13: L-Menthol, Fujifilm Wako Pure Chemical Industries, Ltd. (SP value 20) * 14: Malic acid, Fuso Chemical Co., Ltd. "Fuso Malate M" (SP value 36) * 15: Polydimethylsiloxane 1, Shin-Etsu Chemical Co., Ltd. "KF-96 20cs" (SP value 10) * 16: Polydimethylsiloxane 2, Shin-Etsu Chemical Co., Ltd. "KF-96 1000cs" (SP value 10) *17: Polydimethylsiloxane 3, Shin-Etsu Chemical Co., Ltd. "KF-96 12500cs" (SP value 10)

[0171] <Inorganic Substance Content> When the functional substance in the composite cellulose particles is an inorganic substance, the content is evaluated by elemental mapping of the particle cut surface. Specifically, composite cellulose particles containing an inorganic substance are cut using a cross-section sample preparation device (cross-section polisher, JEOL Ltd., "IB-19520CCP"), and the cross section of the cut particle is subjected to SEM-EDX measurement. It is confirmed whether elements specific to the functional substance are detected inside the particles, and the following evaluation is given: Y: Element can be detected (= inorganic substance is contained in the composite cellulose particles) N: Element cannot be detected (= inorganic substance is substantially not contained in the composite cellulose particles)

[0172] Examples 2-1 to 2-7 (Production and Evaluation of Composite Cellulose Particles) Composite cellulose particles were produced in the same manner as in Example 1-1, except that the type and amount (charge amount) of the functional substance in Example 1-1 was changed as shown in Table 2. The compressive modulus and elastic recovery rate, as well as the inorganic substance content, encapsulation stability, deformability, and release properties of the resulting composite cellulose particles were measured and evaluated using the methods described above. The results are shown in Table 2. The functional substance used here was an inorganic substance, and the composite cellulose particles were produced by dispersing it in ethanol (dispersion medium), so the average particle size in the dispersion medium is also shown in Table 2. The median diameter of the composite cellulose particles obtained in Example 2-1 was 23.7 μm.

[0173] Comparative Examples 2-1 to 2-3 Composite cellulose particles were produced in the same manner as in Example 2-3, except that commercially available cellulose particles listed in Table 2 were used as the carrier cellulose particles. The compressive modulus and elastic recovery rate, as well as the inorganic substance inclusion capacity, encapsulation stability, deformability, and release properties of the obtained composite cellulose particles were measured and evaluated using the methods described above. The results are shown in Table 2. Note that the inorganic substances used in Examples 2-1 to 2-7 and Comparative Examples 2-1 to 2-3 were all particulate substances that were not soluble in organic solvents or azeotropic solvents.

[0174]

[0175] The functional substances used in Table 2 are as follows: *18: Triethoxycaprylylsilane-treated zinc oxide, manufactured by Teika Corporation "MZX-304OTS" *19: Untreated zinc oxide, manufactured by Teika Corporation "MZ-500" *20: Isostearic acid-treated zinc oxide, manufactured by Teika Corporation "MZX-505EX"

[0176] Example 3-1 (Production and Evaluation of Composite Cellulose Particles) (Step (4-2a)) 50 g of the 2-propanol dispersion of the dehydrated cellulose particles obtained in Production Example 4 (liquid content: 90%, solids content: 5 g) was mixed with a solution prepared by dissolving approximately 5 g of the functional substance, a modified polysiloxane represented by the general formula (I) (manufacturer: Kao Corporation), in 45 g of 2-propanol. This mixture was stirred at room temperature for 1 hour and then dried under reduced pressure at 80°C and 250 hPa to remove the 2-propanol, producing composite cellulose particles composed of 100 parts by mass of cellulose and 100 parts by mass of the modified polysiloxane. The compressive modulus and elastic recovery, as well as the content, encapsulation stability, deformability, and release properties of the functional substance, of the resulting composite cellulose particles were evaluated using the methods described above. The results are shown in Table 3.

[0177] Examples 3-2 to 3-3 Composite cellulose particles were produced in the same manner as in Example 3-1, except that the amount of functional substance in Example 3-1 was changed as shown in Table 3. The compressive modulus and elastic recovery rate of the obtained composite cellulose particles, as well as the content, encapsulation stability, deformability, and release properties of the functional substance were evaluated using the methods described above. The results are shown in Table 3.

[0178]

[0179] Tables 1-1, 1-2, 2, and 3 show that the composite cellulose particles of this example have excellent encapsulation stability and release properties for functional substances. In contrast, the composite cellulose particles of Comparative Examples 1-1 to 1-4 had a low content of functional substance, produced many aggregates as composite cellulose particles, and had poor encapsulation stability. Furthermore, when the uncomplexed cellulose particles of Comparative Example 1-5 were subjected to the same procedure without encapsulating a functional substance, the particles themselves shrunk and the compressive modulus increased significantly. The composite cellulose particles of Comparative Examples 2-1 to 2-3 had poor encapsulation properties for functional substances, produced many aggregates as composite cellulose particles, and had poor encapsulation stability.

[0180] According to the present invention, it is possible to provide composite cellulose particles that have good stability in encapsulating a functional substance and are excellent in releasing the functional substance.

Claims

1. Composite cellulose particles containing cellulose and a functional substance, wherein the composite cellulose particles have a compressive modulus of elasticity of 50 MPa or less and an elastic recovery rate of less than 5%.

2. The composite cellulose particles according to claim 1, wherein part or all of the cellulose in the composite cellulose particles is particulate cellulose, and at least part of the functional substance is contained within the particulate cellulose.

3. The composite cellulose particles according to claim 1 or 2, wherein the content of the functional substance is 10 parts by mass or more and 600 parts by mass or less per 100 parts by mass of the cellulose.

4. Composite cellulose particles according to any one of claims 1 to 3, wherein the functional substance contains one or more selected from the group consisting of silicone, fatty acid, ester oil, alcohol, nonionic polymer, organic acid having 8 or less carbon atoms, and chroman derivative.

5. Composite cellulose particles according to any one of claims 1 to 3, wherein the functional substance comprises inorganic particles having an average particle size of less than 400 nm.

6. Composite cellulose particles according to any one of claims 1 to 5, wherein the median diameter of the composite cellulose particles is 5 μm or more and 2000 μm or less.

7. A cosmetic comprising the composite cellulose particles according to any one of claims 1 to 6.

8. A method for producing composite cellulose particles according to any one of claims 1 to 6, comprising the following steps (1) to (4) in this order: Step (1): A step of mixing a water-in-oil cellulose emulsion containing cellulose, water, and an organic solvent with a cellulose non-solvent to precipitate coarse cellulose particles and obtain a suspension containing the coarse cellulose particles. Step (2): A step of subjecting the suspension containing the coarse cellulose particles obtained in step (1) to solid-liquid separation, and then washing the obtained coarse cellulose wet particles to obtain purified cellulose wet particles. Step (3): A step of obtaining carrier cellulose particles or a carrier cellulose particle dispersion by the following step (3-1) or step (3-2). Step (3-1): A step of drying the purified cellulose wet particles obtained in step (2) to obtain dried cellulose particles as carrier cellulose particles. Step (3-2): A step of mixing the purified cellulose wet particles obtained in step (2) with an azeotropic solvent having an azeotropic point with water, and distilling off the water contained in the purified cellulose wet particles by azeotropy to obtain a dehydrated cellulose particle dispersion in which dehydrated cellulose particles are dispersed in the azeotropic solvent as a carrier cellulose particle dispersion. Step (4): A step of obtaining composite cellulose particles by the following step (4-1) or step (4-2). Step (4-1): A step of mixing the carrier cellulose particles obtained in the step (3-1) with a functional substance dispersion liquid in which a functional substance is dispersed in an organic solvent or a functional substance solution in which a functional substance is dissolved in an organic solvent, and then removing the organic solvent to obtain composite cellulose particles containing the functional substance. Step (4-2): A step of obtaining composite cellulose particles by step (4-2a) or step (4-2b). Step (4-2a): A step of mixing the carrier cellulose particle dispersion liquid obtained in the step (3-2) with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2) to obtain composite cellulose particles containing the functional substance. Step (4-2b): A step of obtaining composite cellulose particles containing the functional substance by subjecting the carrier cellulose particle dispersion obtained in the step (3-2) to solid-liquid separation to obtain a cake, mixing the cake with a functional substance, and then removing the solvent containing the azeotropic solvent used in the step (3-2) to obtain composite cellulose particles containing the functional substance.

9. The method for producing composite cellulose particles according to claim 8, wherein the carrier cellulose particles are porous cellulose particles.

10. A method for producing composite cellulose particles according to claim 8 or 9, wherein the surface pore diameter of the carrier cellulose particles is 50 nm or more and 800 nm or less.

11. A method for producing composite cellulose particles according to any one of claims 8 to 10, wherein the pore volume of the carrier cellulose particles is 1.5 mL / g or more and 8.0 mL / g or less.

12. The specific surface area of ​​the carrier cellulose particles is 85 m ２ / g or more 500m ２ The method for producing composite cellulose particles according to any one of claims 8 to 11, wherein the cellulose sieve has a molecular weight of 1 / g or less.

13. A method for producing composite cellulose particles according to any one of claims 8 to 12, wherein the compressive modulus of the carrier cellulose particles is 0.9 MPa or more and 50 MPa or less.

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