Composite cellulose particle

Abstract

A composite cellulose particle containing cellulose and a functional substance, the composite cellulose particle having a compressive elastic modulus of 50 MPa or less and an elastic recovery rate of 5% or more.

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] 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 5% or more. [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 impregnating 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 used in the step (4-1) 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) to obtain composite cellulose particles containing the functional substance. Detailed Description of the Invention

[0006] Such functional polymer particles contain functional substances to impart specific functions. However, when such functional polymer particles are incorporated into cosmetics and the like, particles that have a soft feel yet a sense of elasticity (hereinafter also referred to as "softness" in this specification) are desired, such as during the application process when applying the cosmetics and the like to a target object. However, the porous cellulose particles described in Patent Document 1 have a large maximum surface pore size of 1 / 10 to 1 / 3 of the particle size, so that they can support functional substances with poor wettability. Furthermore, the pore volumes of the porous cellulose particles disclosed in the examples are all 1 mL / g or less, which is considered to result in an insufficient softness. Furthermore, the cellulose particles described in Patent Document 2 are considered to be essentially solid particles, and are also considered to result in an insufficient softness.

[0007] The present invention relates to composite cellulose particles that, when incorporated into cosmetics, etc., can provide an excellent feeling of softness during application of the cosmetics, etc. to a target object. The present inventors have found that the above-mentioned problems can be solved by using composite cellulose particles having a compressive modulus and elastic recovery rate within predetermined ranges.

[0008] According to the present invention, it is possible to provide composite cellulose particles that, when blended into cosmetics or the like, can provide an excellent feeling of softness during the application action, etc., when the cosmetics or the like is applied to an object, and a method for producing the same.

[0009] [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 5% or more. Due to the above-described configuration, the composite cellulose particles of the present invention, when incorporated into cosmetics and the like, can provide an excellent feeling of softness during application, etc., of the cosmetic and the like. 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, when incorporated into cosmetics and the like, the composite cellulose particles can be easily deformed due to the pressure applied during application, etc., of the cosmetic and the like, resulting in a soft feeling on the skin and the like. This ease of deformation is due to the structure of the cellulose that constitutes the composite cellulose particles and the physical properties of the functional substance present in the gaps between the cellulose. Such composite cellulose particles retain a functional substance in the gaps between the cellulose particles, and this functional substance serves as a material that increases the elastic recovery rate of composite cellulose particles containing cellulose, which generally has a low elastic recovery rate. That is, the composite cellulose particles of the present invention are easily deformed in the early stages of pressure application due to the properties of the cellulose and functional substance. As the deformation progresses and the composite cellulose particles are sufficiently crushed (thinned), a force that restores them to their original shape is exerted due to the properties of the functional substance. When composite cellulose particles having such properties are incorporated into cosmetics, etc., it is believed that the application of the cosmetics, etc. to the target object, as described above, will result in a characteristic feel (softness) that is soft yet elastic to the skin.

[0010] <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 polymerization of 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 softness of cosmetics and the like containing the composite cellulose particles, it is preferable that the cellulose contained in the composite cellulose particles does not have a crosslinked structure intentionally introduced by the composite.

[0011] From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, 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.

[0012] From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, it is preferable that part or all of the cellulose contained in the composite cellulose particles is particulate cellulose. Here, the particulate cellulose may be formed by a plurality of particulate celluloses via a functional substance, or a single particulate cellulose may form a single composite cellulose particle. In the present invention, in the case of a composite cellulose particle formed by one or a plurality of particulate celluloses containing a functional substance, 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, the cellulose contained in the composite cellulose particles preferably forms a single composite cellulose particle by itself, from the viewpoint of increasing the elastic recovery rate of the composite cellulose particles and providing a soft feel and elasticity to the skin, i.e., improving the softness. When one particulate cellulose alone forms one composite cellulose particle, the composite cellulose particle of the present invention includes those in a form in which a functional substance is contained in the particulate cellulose (inside the carrier cellulose particle). That is, the composite cellulose particle of the present invention is preferably a composite cellulose particle in which at least a portion of the functional substance is contained in the carrier cellulose particle, and more preferably a composite cellulose particle in which the carrier cellulose particle is a porous cellulose particle and at least a portion of the functional substance is contained in the porous cellulose particle. The composite cellulose particle of the present invention may have all of the functional substance contained in the carrier cellulose particle, or may have only a portion of the functional substance contained in the carrier cellulose particle, with the remainder attached to the outer surface of the carrier cellulose particle. Here, in the present invention, from the viewpoint of increasing the elastic recovery rate of the composite cellulose particle and improving the softness, it is preferable that the composite cellulose particle of the present invention has a form in which all of the functional substance contained in the composite cellulose particle is contained inside the carrier cellulose particle.

[0013] In the present invention, the formation of a composite cellulose particle by one particulate cellulose 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 within 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 within 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 within 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 1 or more and 2 or less, more preferably 1 or more and 1.8 or less, even more preferably 1 or more and 1.6 or less, and even more preferably 1 or more and 1.5 or less, from the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles. When part 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 functional substances to be stably retained in the voids, but also enables the compressive modulus of the composite cellulose particle to be a predetermined value or less. In the present invention, the particulate cellulose is preferably a porous cellulose particle having a large number of pores therein, from the viewpoint of encapsulating a functional substance and improving the softness of cosmetics and the like containing the composite cellulose particles, and more preferably, one porous cellulose particle forms one composite cellulose particle by itself. Porous cellulose particles having a large number of pores therein are preferred because they can retain a functional substance within the pores, and the retention of this functional substance makes it easy to adjust the softness of the composite cellulose particles.

[0014] <Functional Substance> The functional substance constituting the composite cellulose particles of the present invention is a substance used for adjusting the compressive modulus and elastic recovery of the composite cellulose particles to the above-mentioned ranges. More specifically, when the functional substance is composited with a particulate carrier cellulose having an elastic recovery of less than 5% in a state in which the functional substance is not contained to form composite cellulose particles, the functional substance is a material that improves the elastic recovery of the composite cellulose particles to 5% or more while maintaining a low compressive modulus of the composite cellulose particles.

[0015] <Elastomer> Such functional substances include elastomers, which are materials having rubber elasticity. By compounding an elastomer with cellulose, composite cellulose particles having a compressive modulus and elastic recovery rate within a desired range can be obtained. From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, the functional substance preferably includes a material that becomes an elastomer at room temperature (25°C). By using a material that becomes an elastomer at room temperature (25°C), the properties of the elastomer can be effectively exhibited in cosmetics and the like containing the composite cellulose particles, and the cosmetics and the like can be sufficiently softly felt when used.

[0016] The elastomer is not particularly limited and can be selected from known elastomers. Specific examples include natural rubber and synthetic rubber. Examples of synthetic rubber include silicone elastomers, fluorine elastomers, urethane elastomers, styrene elastomers, olefin elastomers, vinyl chloride elastomers, ester elastomers, and amide elastomers. To improve softness, the elastomer preferably includes at least one elastomer selected from the group consisting of silicone elastomers, urethane elastomers, and natural rubber, and more preferably a silicone elastomer. Examples of silicone elastomers include dimethylpolysiloxane, polymethylsilsesquioxane, methylphenylpolysiloxane, polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone. Of these, preferred are at least one elastomers selected from the group consisting of polyethersilicone, amino-modified silicone, and oxazoline-modified silicone, and more preferably oxazoline-modified silicone.

[0017] From the viewpoint of improving the softness of cosmetics and the like blended with the composite cellulose particles, the tensile modulus of the elastomer used here is preferably 50 MPa or less, more preferably 30 MPa or less, even more preferably 10 MPa or less, still more preferably 0.1 MPa or less, and also preferably 0.005 MPa or more, more preferably 0.01 MPa or more. The tensile modulus of the elastomer is preferably 0.005 MPa or more and 50 MPa or less, more preferably 0.005 MPa or more and 30 MPa or less, even more preferably 0.01 MPa or more and 10 MPa or less, and still more preferably 0.01 MPa or more and 0.1 MPa or less.

[0018] The tensile modulus is a modulus of tensile elasticity measured by a tensile tester, and specifically can be measured by the method described in the examples.

[0019] From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, the elastic recovery of the elastomer used here is preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, and is preferably 100% or less, more preferably 70% or less, and even more preferably 50% or less. The elastic recovery of the elastomer is preferably 10% or more and 100% or less, more preferably 10% or more and 70% or less, even more preferably 10% or more and 50% or less, still more preferably 20% or more and 50% or less, and even more preferably 30% or more and 50% or less.

[0020] The elongation percentage of the elastomer used here is preferably 100% or more, more preferably 300% or more, from the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, and is preferably 3000% or less, more preferably 1500% or less, and even more preferably 500% or less, from the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles and from the viewpoint of ease of handling.

[0021] The elastic recovery rate and elongation rate are measured by a micro-compression tester, and specifically, can be measured by the method described in the examples.

[0022] From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, the compressive modulus of the elastomer used here is preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 11 MPa or less, and the lower limit is not particularly limited, but is, for example, preferably 0.01 MPa or more, more preferably 0.1 MPa or more. The compressive modulus is the compressive modulus measured by a microcompression tester, and specifically can be measured by the method described in the examples.

[0023] In the method for producing composite cellulose particles described below, when composited in step (4), dried cellulose particles and a functional substance are mixed in step (4-1), and dehydrated cellulose particles and a functional substance are mixed in step (4-2). In this case, if the functional substance contained in the composite cellulose particles of the present invention is insoluble in an organic solvent or an azeotropic solvent, the functional substance is preferably dispersed in the organic solvent or azeotropic solvent. The particulate functional substance dispersed in the organic solvent or azeotropic solvent (hereinafter, when the functional substance is insoluble in the organic solvent or azeotropic solvent, the dispersion of the functional substance in the organic solvent or azeotropic solvent is also referred to as a functional substance dispersion) is preferably composited by passing through the surface pores of the cellulose particles and diffusing into the interior of the cellulose particles. Therefore, it is preferable that the particle size (dispersion diameter) of such a functional substance in the functional substance dispersion during composite formation is smaller than the surface pore diameter of the carrier cellulose particles. The average particle size (average dispersion diameter) of this particulate functional substance is preferably less than 400 nm, more preferably 300 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 of the functional substance, and from the viewpoint of ease of handling, 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. The average particle size (average dispersion diameter) of the functional substance is preferably 20 nm or more but less than 400 nm, more preferably 50 nm or more but 300 nm, even more preferably 80 nm or more but 250 nm, and even more preferably 100 nm or more but 200 nm.

[0024] The average particle size (average dispersion diameter) of this particulate functional material is a hydrodynamic diameter measured using a dynamic light scattering measuring instrument and is expressed as a volume average diameter. Specifically, the average particle size (average dispersion diameter) of the functional material in the dispersion is measured using a Zetasizer measuring instrument ("Zetasizer Nano ZS" manufactured by Malvern) according to the following procedure. 1. 0.5 g of functional material is mixed with 49.5 g of dispersion medium to prepare a functional material dispersion. 2. The functional material dispersion is placed in the measuring vessel of the aforementioned measuring instrument and measured using dynamic light scattering (DLS) to obtain the volume distribution of particle sizes. 3. The particle size at 50% of the volume distribution of the obtained particle sizes (nm) is taken as the measurement result of the average particle size (average dispersion diameter) (nm) of the functional material in the dispersion.

[0025] <Characteristics of Composite Cellulose Particles> From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, the compressive modulus of the composite cellulose particles is 50 MPa or less, preferably 40 MPa or less, more preferably 35 MPa or less, even more preferably 20 MPa or less, and even more preferably 15 MPa or less. Furthermore, from the viewpoint of imparting a softness to the composite cellulose particles, the lower limit is not limited, and may be, for example, preferably 0.01 MPa or more, more preferably 0.1 MPa or more. Furthermore, from the viewpoint of suppressing a decrease in the elastic recovery rate of the composite cellulose particles, the compressive modulus is preferably 1.0 MPa or more, even more preferably 7.5 MPa or more, and even more preferably 11 MPa or more. The compressive modulus of the composite cellulose particles is preferably 1.0 MPa or more and 50 MPa or less, more preferably 1.0 MPa or more and 40 MPa or less, even more preferably 7.5 MPa or more and 35 MPa or less, even more preferably 11 MPa or more and 20 MPa or less, and even more preferably 11 MPa or more and 15 MPa or less. The pressure may also be 0.01 MPa or more and 50 MPa or less, or 0.1 MPa or more and 50 MPa or less.

[0026] 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.

[0027] The elastic recovery of the composite cellulose particles is 5% or more, preferably 10% or more, more preferably 25% or more, even more preferably 27.5% or more, and ideally 100%, from the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles. Furthermore, from the viewpoint of improving adhesion to the skin, it is preferably 40% or less, more preferably 37% or less, even more preferably 34% or less, and even more preferably 31% or less. The elastic recovery of the composite cellulose particles is preferably 5% or more and 40% or less, more preferably 10% or more and 37% or less, even more preferably 25% or more and 34% or less, and even more preferably 27.5% or more and 31% or less.

[0028] 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.

[0029] The median diameter of the composite cellulose particles (D ５０From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, the average particle diameter is preferably 2,000 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, still more preferably less than 100 μm, and still more preferably 50 μm or less. From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, 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. 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, still more preferably 15 μm or more and less than 100 μm, and still more preferably 15 μm or more and 50 μm or less. Furthermore, the median diameter of the composite cellulose particles treated with treating agent A described below is preferably 250 μm or less, preferably 20 μm or more, more preferably 35 μm or more, from the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles.

[0030] 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 particulate cellulose are filled and the particulate cellulose is 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 particulate cellulose used. By decreasing the content of the functional substance, the voids in the particulate cellulose used are not filled and the particulate cellulose is more likely to shrink when the organic solvent or azeotropic solvent dries, making the median diameter of the resulting composite cellulose particles smaller. Furthermore, the median diameter of the composite cellulose particles can be adjusted by treating with treating agent A in step (5) of the method for producing composite cellulose particles described below. Specifically, treatment with treating agent A increases the median diameter of the resulting composite cellulose particles.

[0031] From the viewpoint of improving the softness of cosmetics and the like incorporating the composite cellulose particles, the content of the functional substance in the composite cellulose particles is, relative to 100 parts by mass of cellulose, preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, still more preferably 130 parts by mass or more, still more preferably 150 parts by mass or more, still more preferably 180 parts by mass or more, still more preferably 200 parts by mass or more, and is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, still more preferably 400 parts by mass or less, still more preferably 300 parts by mass or less, still more preferably 270 parts by mass or less, and still more preferably 250 parts by mass or less. The content of the functional substance is preferably 40 to 600 parts by mass, more preferably 50 to 500 parts by mass, even more preferably 50 to 400 parts by mass, even more preferably 50 to 300 parts by mass, even more preferably 100 to 300 parts by mass, even more preferably 130 to 270 parts by mass, even more preferably 150 to 270 parts by mass, even more preferably 180 to 270 parts by mass, and even more preferably 200 to 250 parts by mass, relative to 100 parts by mass of cellulose.

[0032] <Carrier Cellulose Particles> When the composite cellulose particles of the present invention contain a functional substance and particulate cellulose, it is preferable that the surfaces of the particulate cellulose, i.e., the carrier cellulose particles, are 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.

[0033] 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 pore size can be obtained by selecting this cellulose non-solvent.

[0034] The surface pore diameter of the carrier cellulose particles is not particularly limited, but from the viewpoint of containing a functional substance and improving the softness of cosmetics and the like incorporating the composite cellulose particles, 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, even more preferably 600 nm or less, and even more preferably 400 nm or less. 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 600 nm or less, and even more preferably 200 nm or more and 400 nm or less. The surface pore diameter can be determined by mercury intrusion porosimetry, specifically, by the method described in the Examples.

[0035] 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 of functional substances and the softness of cosmetics and the like containing the composite cellulose particles. Furthermore, the pore volume of the carrier cellulose particles 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 or less, from the viewpoint of suppressing disintegration during the production process of the composite cellulose particles. The pore volume of the carrier cellulose particles is preferably 1.5 mL / g or more and 8.0 mL / g or less, more preferably 2.0 mL / g or more and 7.0 mL / g or less, even more preferably 2.3 mL / g or more and 6.0 mL / g or less, still more preferably 2.3 mL / g or more and 5.0 mL / g or less, still more preferably 2.3 mL / g or more and 4.0 mL / g or less, and even more preferably 2.4 mL / g or more and 4.0 mL / g or less. The pore volume is a value determined by mercury intrusion porosimetry, where the total volume of mercury that has penetrated into the pores inside the carrier cellulose particles and the gaps between the particles is divided by the mass of the particles and normalized. 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.

[0036] The specific surface area of ​​the carrier cellulose particles is 85 m from the viewpoint of improving the encapsulation stability of the functional substance and from the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles. ２ / g or more, preferably 90m ２ / g or more, more preferably 95m ２ / g or more, more preferably 100m２ / g or more, and even more preferably 103m ２ In addition, the specific surface area of ​​the cellulose carrier particles is 500 m / g or more from the viewpoint of preventing the cellulose carrier particles from collapsing 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 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 103m ２ / g or more 150m 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.

[0037] From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, 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, the compressive modulus of the carrier cellulose particles is preferably 0.9 MPa or more, more preferably 1.0 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. The compressive modulus of the carrier cellulose particles is preferably 0.9 MPa or more and 50 MPa or less, more preferably 0.9 MPa or more and 40 MPa or less, even more preferably 1.0 MPa or more and 30 MPa or less, even more preferably 1.0 MPa or more and 20 MPa or less, even more preferably 2.0 MPa or more and 10 MPa or less, even more preferably 2.0 MPa or more and 7.0 MPa or less, even more preferably 2.5 MPa or more and 6.0 MPa or less, even more preferably 2.8 MPa or more and 5.3 MPa or less, even more preferably 2.8 MPa or more and 5.2 MPa or less, and even more preferably 3.0 MPa or more and 5.0 MPa or less.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The composite cellulose particles of the present invention may further contain one or more selected from the group consisting of silicone (c1) that is liquid at 25°C and gel-like substance (c2) consisting of organopolysiloxane and silicone that is liquid at 25°C (hereinafter also referred to as treatment agent A). Here, the composite cellulose particles of the present invention preferably contain this treatment agent A from the viewpoint of reducing the compressive modulus. However, from the viewpoint of the composite cellulose particles of the present invention having an elastic recovery rate of 5% or more, treatment agent A is an optional component. By incorporating this treatment agent A into the composite cellulose particles, the compressive modulus of the composite cellulose particles can be further reduced and the softness can be improved when the composite cellulose particles are incorporated into cosmetics. The silicone (c1) that is liquid at 25°C can be used without any particular limitation as long as it is liquid at 25°C. This silicone (c1) that is liquid at 25°C is preferably a non-volatile silicone oil such as a linear silicone. Examples of such nonvolatile silicone oils include dimethylpolysiloxane, methylphenylpolysiloxane, polyether-modified silicone, and amino-modified silicone.

[0042] The viscosity of the component (c1) at 25°C is preferably 50 mm from the viewpoint of improving the softness of the composite cellulose particles. ２ / s or less, more preferably 30 mm ２ / s or less, more preferably 20 mm ２ / s or less, and even more preferably 10 mm ２ / s or less, and preferably 1 mm ２ / s or more, more preferably 3 mm ２ / s or more, more preferably 5 mm ２ The viscosity of component (c1) at 25°C is preferably 1 mm ２ / s or more 50mm ２ / s or less, more preferably 3 mm ２ / s or more 30mm ２ / s or less, more preferably 5 mm ２ / s or more 20mm ２ / s or less, and even more preferably 5 mm ２ / s or more 10mm ２Commercially available products of this component (c1) include "KF-96A-6CS" (viscosity at 25°C: 6 mm ２ / s), "KF-96A-10CS" (viscosity at 25 ° C.: 10 mm ２ / s), "KF-96A-20CS" (viscosity at 25 ° C.: 20 mm ２ / s), "KF-96A-30CS" (viscosity at 25 ° C.: 30 mm ２ / s), "KF-96A-50CS" (viscosity at 25 ° C.: 50 mm ２ / s), and the like, and these can be used alone or in combination of two or more.

[0043] The gel-like substance (c2) is a gel-like substance composed of an organopolysiloxane and a silicone that is liquid at 25°C. The organopolysiloxane used here is an organopolysiloxane that is solid at 25°C, and any organopolysiloxane that can be mixed with a silicone that is liquid at 25°C to form a gel-like substance can be used without particular limitation. From the viewpoint of improving the softness of the composite cellulose particles, this organopolysiloxane is preferably at least one selected from the group consisting of dimethylpolysiloxane, polymethylsilsesquioxane, methylphenylpolysiloxane, polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone, more preferably at least one selected from the group consisting of polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone, even more preferably oxazoline-modified silicone. As the organopolysiloxane, the silicone-based elastomers listed above as functional substances can also be used. By mixing this silicone-based elastomer with a silicone that is liquid at 25°C, a gel-like substance can be formed, which can be used as treatment agent A. In this case, the functional substance and the gel-like substance (c2) are prepared separately as components constituting the composite cellulose particles. The silicone that is liquid at 25°C and used to obtain the gel-like substance (c2) can be the liquid silicone described above for component (c1).

[0044] From the viewpoint of improving the softness of cosmetics and the like containing the composite cellulose particles, the content of the optional component treating agent A is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, relative to 100 parts by mass of the composite cellulose particles. The content of treating agent A is preferably 10 parts by mass or more and 80 parts by mass or less, more preferably 20 parts by mass or more and 70 parts by mass or less, and even more preferably 30 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the composite cellulose particles.

[0045] [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 used in the step (4-1) 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.

[0046] 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).

[0047] <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.

[0048] <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.

[0049] 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. 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 is obtained by extending the acid hydrolysis time.

[0050] 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.

[0051] 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.

[0052] (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.

[0053] From the viewpoint of improving the solubility of the starting cellulose and the stability of the resulting aqueous cellulose 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 viewpoints, 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. Furthermore, 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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). 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.

[0058] 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, from the viewpoint of improving the solubility of the starting cellulose and the stability of the resulting aqueous cellulose solution, and from the same viewpoint, is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. 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.

[0059] <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.

[0060] 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 (B) 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 cellulose nonsolvents 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 calculated by taking the weighted average of the ClogP values ​​of the individual organic solvents constituting the mixed solvent, with the volume of each solvent being used as a weight.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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 100 parts by mass or more, even more preferably 120 parts by mass or more, relative to 100 parts by mass of the aqueous cellulose solution, 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 viewpoint of improving the emulsion stability of the water-in-oil cellulose emulsion, preferably 80 parts by mass or more, more preferably 100 parts by mass or more, more preferably 800 parts by mass or less, even more preferably 120 parts by mass or more, even more preferably 120 parts by mass or more, even more preferably 200 parts by mass or less.

[0066] 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.

[0067] 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).

[0068] 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.

[0069] 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.

[0070] 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, 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, still more preferably one or more selected from the group consisting of sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate, and sucrose behenate, and even more preferably one or more selected from the group consisting of sucrose erucate and sucrose behenate.

[0071] In step (1-2), when an emulsifier is further mixed, the amount of emulsifier mixed is, from the viewpoint of further improving the emulsion stability of the water-in-oil cellulose emulsion, preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, even more preferably 0.03 parts by mass or more, still more preferably 0.1 parts by mass or more, still more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the organic solvent, from the viewpoint of ease of washing (productivity) and economic efficiency, preferably 2.5 parts by mass or less, more preferably 2.0 parts by mass or less, even more preferably 1.5 parts by mass or less. And, the amount of emulsifier mixed is, relative to 100 parts by mass of the organic solvent, preferably 0.01 parts by mass or more and 2.5 parts by mass or less, more preferably 0.02 parts by mass or more and 2.0 parts by mass or less, even more preferably 0.03 parts by mass or more and 1.5 parts by mass or less, still more preferably 0.1 parts by mass or more and 1.5 parts by mass or less, still more preferably 0.5 parts by mass or more and 1.5 parts by mass or less.

[0072] 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.

[0073] 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. The temperature during mixing of the aqueous cellulose solution and the organic solvent is 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.

[0074] 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, for example, when using the homomixer used in the examples, it is preferably 1000 rpm or more, more preferably 3000 rpm or more, even more preferably 3500 rpm or more, even more preferably 4000 rpm or more, and preferably 15000 rpm or less, more preferably 14000 rpm or less, even more preferably 13000 rpm or less, and even more preferably 12000 rpm or less. The stirring speed when mixing the aqueous cellulose solution with the organic solvent is preferably 1000 rpm or more and 15000 rpm or less, more preferably 3000 rpm or more and 14000 rpm or less, even more preferably 3500 rpm or more and 13000 rpm or less, and even more preferably 4000 rpm or more and 12000 rpm or less.

[0075] 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.

[0076] <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).

[0077] 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.

[0078] 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.

[0079] 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).

[0080] 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, controlling the internal morphology of the cellulose particles to obtain carrier cellulose particles with the desired physical properties, and maintaining emulsion stability. Also, 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. 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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, 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. 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.

[0086] <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.

[0087] 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 that can be easily dried, 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.

[0088] <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).

[0089] <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.

[0090] 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.

[0091] 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).

[0092] 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.

[0093] 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 viewpoints of productivity and economy (output relative to the batch size), and is preferably 2,000 parts by mass or less, more preferably 1,000 parts by mass or less, and even more preferably 600 parts by mass or less, from the viewpoints of suppressing particle shrinkage and obtaining particles with a desired structure. The amount of the replacement dispersion medium used for the dispersion medium replacement is preferably 100 parts by mass or more and 2,000 parts by mass or less, more preferably 200 parts by mass or more and 1,000 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.

[0094] 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.

[0095] 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. 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.

[0096] 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.

[0097] <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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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 the group consisting of 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] <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.

[0106] 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. A solvent having an octanol / water partition coefficient ClogP of less than 0.5 is preferably an alcohol, from the same viewpoint as above. As the alcohol, it is preferable to use the same alcohol as exemplified in step (1) above, 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). Specifically, the alcohol preferably contains one or more selected from the group consisting of methanol, ethanol, 1-propanol, and 2-propanol, and more preferably contains one or more selected from the group consisting of methanol, ethanol, and 2-propanol.

[0107] 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.

[0108] <Step (4)> Step (4) is a step of obtaining composite cellulose particles by the following step (4-1) or step (4-2).

[0109] <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 used in step (4-1) to obtain composite cellulose particles containing the functional substance.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] The content of the functional substance in the composite cellulose particles can be within the range described above for the content of the functional substance in the composite cellulose particles. That is, from the viewpoint of improving the softness of the composite cellulose particles, the content of the functional substance in the composite cellulose particles is, relative to 100 parts by mass of cellulose, preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 100 parts by mass or more, still more preferably 130 parts by mass or more, still more preferably 150 parts by mass or more, still more preferably 180 parts by mass or more, still more preferably 200 parts by mass or more, and is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, still more preferably 400 parts by mass or less, still more preferably 300 parts by mass or less, still more preferably 270 parts by mass or less, and more preferably 250 parts by mass or less. The content of the functional substance is preferably 40 parts by mass or more and 600 parts by mass or less, more preferably 50 parts by mass or more and 500 parts by mass or less, even more preferably 50 parts by mass or more and 400 parts by mass or less, even more preferably 50 parts by mass or more and 300 parts by mass or less, even more preferably 100 parts by mass or more and 300 parts by mass or less, even more preferably 130 parts by mass or more and 270 parts by mass or less, even more preferably 150 parts by mass or more and 270 parts by mass or less, even more preferably 180 parts by mass or more and 270 parts by mass or less, and even more preferably 200 parts by mass or more and 250 parts by mass or less, relative to 100 parts by mass of the carrier cellulose particles.

[0115] 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 1000 parts by mass or more, even more preferably 1500 parts by mass or more, relative to 100 parts by mass of the functional substance, and from the viewpoint of economy and productivity, preferably 10,000 parts by mass or less, more preferably 9,500 parts by mass or less, even more preferably 9,000 parts by mass or less. And, from the same viewpoint as above, the amount of organic solvent used here is, relative to 100 parts by mass of the functional substance, preferably 300 parts by mass or more and 10,000 parts by mass or less, more preferably 1000 parts by mass or more and 9,500 parts by mass or less, even more preferably 1,500 parts by mass or more and 9,000 parts by mass or less.

[0116] Next, the carrier cellulose particles and the prepared functional substance dispersion or functional substance solution are mixed. From the viewpoint of efficiently incorporating the functional substance into the carrier cellulose particles to be mixed, 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, even more preferably 900 parts by mass or more, and preferably 2000 parts by mass or less, more preferably 1500 parts by mass or less, even more preferably 1200 parts by mass or less, relative to 100 parts by mass of the dry cellulose particles to be mixed. And, preferably 500 parts by mass or more to 2000 parts by mass or less, more preferably 700 parts by mass or more to 1500 parts by mass or less, even more preferably 700 parts by mass or more to 1200 parts by mass or less, even more preferably 900 parts by mass or more to 1200 parts by mass or less.

[0117] 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.

[0118] The stirring time of the carrier cellulose particles and the functional substance dispersion or functional substance solution is preferably 0.1 hour or more, more preferably 0.2 hour or more, from the viewpoint of fully incorporating the functional substance into the carrier cellulose, and from the same viewpoint, is preferably 12 hours or less, more preferably 6 hours or less, even more preferably 3 hours or less, and even more preferably 1 hour or less. From the same viewpoint, this stirring time is preferably 0.1 hours or more and 12 hours or less, more preferably 0.1 hours or more and 6 hours or less, even more preferably 0.1 hours or more and 3 hours or less, even more preferably 0.1 hours or more and 1 hour or less, and even more preferably 0.2 hours or more and 1 hour or less.

[0119] 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.

[0120] 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 preferably 30°C or higher, more preferably 40°C or higher, from the viewpoint of rapidly reducing the amount of remaining solvent, and are preferably 110°C or lower, more preferably 90°C or lower, even more preferably 70°C or lower, and even more preferably 60°C or lower, from the viewpoint of ease of temperature adjustment. The heating temperature in the drying treatment is preferably 30°C or higher and 110°C or lower, more preferably 30°C or higher and 90°C or lower, even more preferably 30°C or higher and 70°C or lower, and even more preferably 40°C or higher and 60°C or lower. The pressure in the drying treatment may be any pressure that promotes the volatilization 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, even more preferably 300 hPa or less, even more preferably 100 hPa or less, and even more preferably 70 hPa or less. The lower limit may be a vacuum (0 hPa). Considering the ease of adjusting the pressure, it is preferably 10 hPa or more, more preferably 20 hPa or more, and even more preferably 30 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.

[0121] <Step (4-2)> Step (4-2) is a step of obtaining composite cellulose particles by the following step (4-2a) or step (4-2b).

[0122] 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.

[0123] 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), since the dehydrated cellulose particle dispersion contains a sufficient amount of azeotropic solvent to disperse or dissolve the functional substance, 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 dehydrated 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).

[0124] 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.

[0125] 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).

[0126] 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 encapsulating 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.

[0127] 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, from the viewpoint of rapidly reducing the amount of remaining solvent, and are preferably 90°C or lower, more preferably 80°C or lower, even more preferably 70°C or lower, and even more preferably 60°C or lower, from the viewpoint of ease of temperature control. The heating temperature is preferably 30°C or higher and 90°C or lower, more preferably 30°C or higher and 80°C or lower, even more preferably 30°C or higher and 70°C or lower, and even more preferably 40°C or higher and 60°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, even more preferably 300 hPa or less, even more preferably 100 hPa or less, and even more preferably 70 hPa or less. The lower limit may be a vacuum (0 hPa). Considering the ease of adjusting the pressure, it is preferably 10 hPa or more, more preferably 20 hPa or more, and even more preferably 30 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.

[0128] 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.

[0129] 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).

[0130] 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.

[0131] 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 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.

[0132] <Step (5)> Step (5) is an optional step in which the composite cellulose particles obtained in step (4-1) or step (4-2) are further treated with treatment agent A. This treatment with treatment agent A makes it possible to adjust the compressive modulus and elastic recovery rate of the composite cellulose particles. This adjustment allows composite cellulose particles containing treatment agent A to improve the softness of cosmetics and the like when blended into cosmetics and the like, compared to untreated composite cellulose particles. Specifically, the softness can be improved by reducing the compressive modulus while maintaining the elastic recovery rate without a significant decrease.

[0133] In step (5), the composite cellulose particles and treating agent A are mixed in an organic solvent, and the composite cellulose particles are impregnated with the mixture while mixing or dissolving treating agent A in the organic solvent. Treating agent A is the treating agent A described above for the composite cellulose particles. The organic solvent used is one that can be removed by drying after impregnation into the composite cellulose particles while leaving treating agent A inside the cellulose particles (encapsulated). This organic solvent is one that can be removed by drying, preferably by heat drying, vacuum drying, or a combination of these, heat and vacuum drying. Examples of the organic solvent include hydrocarbon solvents with 6 or fewer carbon atoms, such as pentane and hexane; ketone solvents with 6 or fewer carbon atoms, such as acetone and methyl isobutyl ketone; and alcohol solvents with 6 or fewer carbon atoms, such as ethanol and 2-propanol. Preferred are hydrocarbon solvents with 6 or fewer carbon atoms, such as pentane and hexane.

[0134] The organic solvent is then removed, leaving the treating agent A that has permeated the cellulose in the composite cellulose particles in the cellulose residue, and / or further precipitating or remaining within the pores and / or on the surface of the composite cellulose particles, yielding composite cellulose particles containing treating agent A. In this process, treating agent A plasticizes the cellulose (cellulose mother particles), thereby reducing the compressive modulus of the composite cellulose particles and, when these composite cellulose particles are incorporated into a cosmetic, presumably improving the softness of the cosmetic. When treating agent A is mixed or dissolved in an organic solvent and then mixed with the composite cellulose particles, the liquid treating agent A can easily penetrate the pores of the composite cellulose particles. In other words, the treating agent A can be impregnated into the pores of the composite cellulose particles, allowing for easy adjustment of their properties.

[0135] In this step (5), the amount of treating agent A used can be within the range explained for the content of treating agent A in the composite cellulose particles. That is, from the viewpoint of improving the softness of the composite cellulose particles, the amount of treating agent A in the composite cellulose particles is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less, relative to 100 parts by mass of the composite cellulose particles. The amount of treating agent A is preferably 10 parts by mass or more and 80 parts by mass or less, more preferably 20 parts by mass or more and 70 parts by mass or less, and even more preferably 30 parts by mass or less.

[0136] Furthermore, from the viewpoint of efficiently incorporating the treating agent A into the composite cellulose particles, the amount of the organic solvent used in step (5) is preferably 3,000 parts by mass or more, more preferably 4,000 parts by mass or more, even more preferably 5,000 parts by mass or more, and is preferably 24,000 parts by mass or less, more preferably 22,000 parts by mass or less, even more preferably 20,000 parts by mass or less, relative to 100 parts by mass of the treating agent A. From the same viewpoint as above, the amount of the organic solvent used here is preferably 3,000 parts by mass or more and 24,000 parts by mass or less, more preferably 4,000 parts by mass or more and 22,000 parts by mass or less, even more preferably 5,000 parts by mass or more and 20,000 parts by mass or less, relative to 100 parts by mass of the functional substance.

[0137] The composite cellulose particles and the treating agent A can be mixed under the same conditions as those for the device, stirring speed, and stirring time described in step (4-1).

[0138] The composite cellulose particles and the treating agent A are thoroughly mixed, the composite cellulose particles are treated with the treating agent A, and then the organic solvent is removed to obtain composite cellulose particles containing the treating agent A. The organic solvent is removed by a drying treatment, preferably by heat drying, vacuum drying, or a combination of these, namely, heat-vacuum drying. The organic solvent can be removed under the same conditions as the treatment method, temperature, and pressure used in the drying described in step (4-1).

[0139] [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.

[0140] <Cosmetics> The present invention further provides a cosmetic containing the composite cellulose particles. The cosmetic of the present invention can impart a pleasant feel by including the composite cellulose particles. That is, when applying the cosmetic containing the composite cellulose particles to a target object, the cosmetic can provide a soft feeling due to the presence of the composite cellulose particles. From the viewpoint of effectively exerting the above-mentioned effects, the cosmetic of the present invention is preferably a skin cosmetic, and examples of such skin cosmetic include foundation, makeup base, sunscreen, emulsion, lotion, etc. 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.

[0141] 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 5% or more. <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 median diameter of the composite cellulose particles is preferably 2000 μm or less, more preferably 110 μm or less, even more preferably 50 μm or less, and preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more. <4> The composite cellulose particles according to any one of <1> to <3>, wherein the median diameter of the composite cellulose particles is preferably 5 μm or more and 2,000 μm or less, more preferably 10 μm or more and 110 μm or less, and even more preferably 15 μm or more and 50 μm or less. <5> The composite cellulose particles according to any one of <1> to <4>, wherein the functional substance contains an elastomer. <6> The composite cellulose particles according to <5>, wherein the elastomer is natural rubber or synthetic rubber, and the synthetic rubber includes at least one selected from the group consisting of silicone-based elastomers, fluorine-based elastomers, urethane-based elastomers, styrene-based elastomers, olefin-based elastomers, vinyl chloride-based elastomers, ester-based elastomers, and amide-based elastomers, and preferably includes at least one selected from the group consisting of silicone-based elastomers, urethane-based elastomers, and natural rubber, and more preferably is a silicone-based elastomer.<7> The composite cellulose particles according to <6>, wherein the silicone elastomer comprises at least one selected from the group consisting of dimethylpolysiloxane, polymethylsilsesquioxane, methylphenylpolysiloxane, polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone, preferably at least one selected from the group consisting of polyethersilicone, amino-modified silicone, and oxazoline-modified silicone, more preferably oxazoline-modified silicone. <8> The composite cellulose particles according to any one of <1> to <4>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 400 μm or less, and the functional substance comprises an elastomer. <9> The composite cellulose particles according to any one of <1> to <4>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 250 μm or less, and the functional substance comprises at least one selected from the group consisting of polyethersilicone, amino-modified silicone, and oxazoline-modified silicone. <10> The composite cellulose particles according to any one of <1> to <4>, wherein the median diameter of the composite cellulose particles is from 5 μm to 200 μm, and the functional substance is an oxazoline-modified silicone. <11> The composite cellulose particles according to any one of <1> to <10>, wherein the content of the functional substance is preferably 40 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 300 parts by mass or less, and even more preferably 250 parts by mass or less, relative to 100 parts by mass of the cellulose. <12> The composite cellulose particles according to any one of <1> to <11>, wherein the content of the functional substance is preferably 40 parts by mass or more to 600 parts by mass or less, more preferably 100 parts by mass or more to 300 parts by mass or less, and even more preferably 200 parts by mass or more to 250 parts by mass, relative to 100 parts by mass of the cellulose. <13> The composite cellulose particles according to <12>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 400 μm or less, the functional substance contains an elastomer, and the content of the functional substance is 40 parts by mass or more and 600 parts by mass or less per 100 parts by mass of the cellulose.<14> The composite cellulose particles according to <12>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 250 μm or less, the functional substance comprises one or more selected from the group consisting of polyether silicone, amino-modified silicone, and oxazoline-modified silicone, and the content of the functional substance is 50 parts by mass or more and 500 parts by mass or less per 100 parts by mass of the cellulose. <15> The composite cellulose particles according to <12>, wherein the median diameter of the composite cellulose particles is preferably 5 μm or more and 200 μm or less, more preferably 15 μm or more and 100 μm or less, and even more preferably 15 μm or more and 50 μm or less, the functional substance is oxazoline-modified silicone, and the content of the functional substance is 100 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the cellulose. <16> The composite cellulose particles according to any one of <1> to <15>, further comprising one or more selected from the group consisting of silicone (c1) that is liquid at 25° C. and gel-like substance (c2) consisting of organopolysiloxane and silicone that is liquid at 25° C. <17> The composite cellulose particles according to <16>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 400 μm or less, the functional substance contains an elastomer, the content of the functional substance is 40 parts by mass or more and 600 parts by mass or less per 100 parts by mass of the cellulose, and further comprising silicone (c1) that is liquid at 25° C. <18> The composite cellulose particles according to <16>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 250 μm or less, the functional substance comprises one or more selected from the group consisting of polyether silicone, amino-modified silicone, and oxazoline-modified silicone, the content of the functional substance is 50 parts by mass or more and 500 parts by mass or less per 100 parts by mass of the cellulose, and further comprises silicone (c1) that is liquid at 25°C.<19> The composite cellulose particles according to <16>, wherein the median diameter of the composite cellulose particles is preferably 5 μm or more and 200 μm or less, more preferably 15 μm or more and 150 μm or less, the functional substance is an oxazoline-modified silicone, the content of the functional substance is 100 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a silicone (c1) that is liquid at 25° C. <20> The viscosity of the component (c1) at 25° C. is preferably 50 mm. ２ / s or less, more preferably 30 mm ２ / s or less, more preferably 20 mm ２ / s or less, and preferably 1 mm ２ / s or more, more preferably 3 mm ２ / s or more, more preferably 5 mm ２ <21> The composite cellulose particles according to <16>, wherein the viscosity of the component (c1) at 25°C is preferably 1 mm / s or more. ２ / s or more 50mm ２ / s or less, more preferably 3 mm ２ / s or more 30mm ２ / s or less, more preferably 5 mm ２ / s or more 20mm ２ <22> The composite cellulose particles according to <16>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 400 μm or less, the functional substance contains an elastomer, the content of the functional substance is 40 parts by mass or more and 600 parts by mass or less per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a silicone (c1) that is liquid at 25°C, and the viscosity of the component (c1) at 25°C is 1 mm or less. ２ / s or more 50mm ２<23> The composite cellulose particles according to <21>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 250 μm or less, the functional substance contains one or more selected from the group consisting of polyether silicone, amino-modified silicone, and oxazoline-modified silicone, the content of the functional substance is 50 parts by mass or more and 500 parts by mass or less per 100 parts by mass of the cellulose, and further contains silicone (c1) that is liquid at 25°C, and the viscosity of the component (c1) at 25°C is 3 mm or less. ２ / s or more 30mm ２ <24> The composite cellulose particles according to <21>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 200 μm or less, the functional substance is an oxazoline-modified silicone, the content of the functional substance is 100 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a silicone (c1) that is liquid at 25°C, and the viscosity of the component (c1) at 25°C is 5 mm ２ / s or more 20mm ２ / s or less. <25> The composite cellulose particles according to <16>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 400 μm or less, the functional substance contains an elastomer, the content of the functional substance is 40 parts by mass or more and 600 parts by mass or less per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a gel-like substance (c2) made of an organopolysiloxane and a silicone that is liquid at 25°C. <26> The composite cellulose particles according to <16>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 250 μm or less, the functional substance contains one or more selected from the group consisting of polyether silicone, amino-modified silicone, and oxazoline-modified silicone, the content of the functional substance is 50 parts by mass or more and 500 parts by mass or less per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a gel-like substance (c2) made of an organopolysiloxane and a silicone that is liquid at 25°C. <27> The composite cellulose particles according to <16>, wherein the median diameter of the composite cellulose particles is from 5 μm to 200 μm, the functional substance is an oxazoline-modified silicone, the content of the functional substance is from 100 parts by mass to 300 parts by mass per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a gel-like substance (c2) composed of an organopolysiloxane and a silicone that is liquid at 25° C. <28> The composite cellulose particles according to <16>, wherein the organopolysiloxane is preferably at least one selected from the group consisting of dimethylpolysiloxane, polymethylsilsesquioxane, methylphenylpolysiloxane, polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone, more preferably at least one selected from the group consisting of polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone, and even more preferably oxazoline-modified silicone.<29> The composite cellulose particles according to <28>, wherein the median diameter of the composite cellulose particles is 5 μm or more and 400 μm or less, the functional substance contains an elastomer, the content of the functional substance is 40 parts by mass or more and 600 parts by mass or less per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a gel-like substance (c2) made of an organopolysiloxane and a silicone that is liquid at 25°C, and the organopolysiloxane is one or more selected from the group consisting of dimethylpolysiloxane, polymethylsilsesquioxane, methylphenylpolysiloxane, polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone. <30> The composite cellulose particles according to <28>, wherein the median diameter of the composite cellulose particles is from 5 μm to 250 μm, the functional substance comprises one or more selected from the group consisting of polyether silicone, amino-modified silicone, and oxazoline-modified silicone, the content of the functional substance is from 50 parts by mass to 500 parts by mass per 100 parts by mass of the cellulose, and the composite cellulose particles further comprise a gel-like substance (c2) comprising an organopolysiloxane and a silicone that is liquid at 25°C, and the organopolysiloxane is one or more selected from the group consisting of polyether-modified silicone, amino-modified silicone, and oxazoline-modified silicone. <31> Composite cellulose particles according to <28>, wherein the composite cellulose particles have a median diameter of 5 μm or more and 200 μm or less, the functional substance is an oxazoline-modified silicone, the content of the functional substance is 100 parts by mass or more and 300 parts by mass or less per 100 parts by mass of the cellulose, and the composite cellulose particles further contain a gel-like substance (c2) composed of an organopolysiloxane and a silicone that is liquid at 25°C, and the organopolysiloxane is an oxazoline-modified silicone. <32> A cosmetic comprising the composite cellulose particles according to any one of <1> to <31>. <33> Use of the composite cellulose particles according to any one of <1> to <31> as a cosmetic. <34> A method for producing composite cellulose particles, the method 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 impregnating 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, thereby obtaining 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), thereby obtaining 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. <35> The method for producing composite cellulose particles according to <34>, wherein the functional substance used in the step (4-2a) is a functional substance without pretreatment.<36> The method for producing composite cellulose particles according to <34>, 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. <37> The method for producing composite cellulose particles according to <34>, wherein the functional substance used in the step (4-2b) is a functional substance without pretreatment. <38> The method for producing composite cellulose particles according to <34>, 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. <39> The method for producing composite cellulose particles according to any of <34> to <38>, 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. <40> The method for producing composite cellulose particles according to any one of <34> to <39>, wherein the step (1) comprises the following steps (1-1) to (1-3) in this order: <41> The method for producing composite cellulose particles according to any one of <34> to <40>, wherein the cellulose non-solvent used in the step (1) comprises one or more selected from the group consisting of methanol and ethanol. <42> The method for producing composite cellulose particles according to any one of <34> to <41>, 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.<43> A method for producing composite cellulose particles according to any one of <34> to <42>, 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. <44> A method for producing composite cellulose particles according to any one of <34> to <43>, 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. <45> A method for producing composite cellulose particles according to any one of <34> to <43>, 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. <46> A method for producing composite cellulose particles according to any one of <34> to <45>, wherein the functional substance used in the step (4) is soluble or dispersible in the azeotropic solvent used in the step (3). <47> A method for producing composite cellulose particles according to any one of <34> to <46>, wherein the carrier cellulose particles are porous cellulose particles. <48> The method for producing composite cellulose particles according to any one of <34> to <47>, wherein at least a part of the functional substance is contained in the carrier cellulose particles.

[0142] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Various measurement and evaluation methods are as follows.

[0143] <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 five times, and use the arithmetic average of the three obtained compressive modulus values ​​excluding the maximum and minimum values ​​as the measurement result of the compressive modulus of the particles.

[0144] <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 mN) (indenter displacement y (mm)). 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 unloading. 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 above five times, and use the arithmetic mean value of the three measurements excluding the maximum and minimum elastic recovery values ​​as the measurement result of the elastic recovery of the particles.

[0145] <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.

[0146] <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)

[0147] <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)

[0148] <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.

[0149] <Measurement of tensile modulus and elongation rate> The tensile modulus and elongation rate of the functional substance are measured by cutting a film-like elastomer formed from each functional substance into a JIS No. 7 dumbbell test piece and measuring the tensile modulus and elongation rate using a Tensilon universal testing machine (model: RTC-1210A, manufactured by Orientec Co., Ltd.). The pulling speed is 50 mm / sec, and the measurement is carried out five times for each test piece, and the average of three values ​​excluding the maximum and minimum values ​​is used as the test result. Elongation rate (%) = elongation of film due to test (mm) / length before test (= 12 mm) Tensile modulus = stress (MPa) / elongation rate (%) The film-like elastomer used in this measurement was prepared by adding 5.2 g of ethanol to 4.4 g of a 50 mass % ethanol solution of oxazoline-modified silicones 1 to 3 obtained in Production Examples 3-1 to 3-3 described below, dissolving the solution uniformly, adding this solution to a 7.5 cm diameter fluororesin petri dish, and leaving it to stand for 3 days under a nitrogen flow, to obtain a film (thickness: 0.5 mm).

[0150] Sensory Evaluation Test (Softness) In an environment with a temperature of 20-25°C and a humidity of 25-40% RH, 0.2 g of the powder or powder composition of each of the Examples and Comparative Examples was applied to the back of the hand using a spatula. The "softness" was evaluated by rubbing the applied area with a finger and scored according to the following criteria. Two expert panelists evaluated the results in comparison with Example 2 (reference sample; score 4). A sample that was perceived as having a "softness" superior to the reference sample and very good was given a "5," a sample that was perceived as having a "softness" equivalent to the reference sample and good was given a "4," a sample that was perceived as having a "softness" slightly inferior to the reference sample but average was given a "3," a sample that was perceived as having a "softness" inferior to the reference sample was given a "2," and a sample that was perceived as having a "softness" significantly inferior to the reference sample and very poor was given a "1." Scores were given in increments of 0.5, including intermediate scores.

[0151] <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]

[0152] <Production Example 1-1> (Production and Evaluation of Carrier Cellulose Particles 1) (Step (1)) <Step (1-1)> As the starting cellulose, cellulose I type 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 4% by mass, and the NaOH concentration was 7.6% by mass.

[0153] <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.

[0154] <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.

[0155] (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.

[0156] (Step (3-1)) The purified wet cellulose particles recovered in step (2) were quickly frozen in a dry ice / ethyl alcohol bath at -72°C, and then primarily dried at -10°C under a vacuum of 100 Pa or less to remove most of the water. After that, secondary drying was carried out at 25°C while maintaining the reduced pressure to obtain dried cellulose particles (carrier cellulose particles 1). The surface pore size, pore volume, specific surface area, compressive modulus, and median diameter of the obtained dried cellulose particles (carrier cellulose particles 1) were evaluated by the methods described above, and the results are shown in Table 1.

[0157] <Production Example 1-2> (Production of Carrier Cellulose Particles 2) (Substitution Step) 170 g of purified wet cellulose particles (solid content: approximately 17 g) obtained by carrying out steps (2) in Production Example 1-1 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. At this time, the 2-propanol and the water remaining in the purified wet cellulose particles obtained by the substitution step were azeotropically mixed. The vapor generated by the azeotropy 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 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 (carrier cellulose particles 2) 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 (carrier cellulose particles 2) was 23.1 μm, as shown in Table 1.

[0158]

[0159] <Production Example 2-1> (Production and Evaluation of Oxazoline-Modified Silicone 1) A mixture obtained by mixing 93.8 g (0.95 mol) of 2-ethyl-2-oxazoline and 203.3 g of ethyl acetate was dehydrated for 15 hours at room temperature (25°C) using 14.8 g of molecular sieves (trade name: Zeorum A-4, manufactured by Tosoh Corporation). Also, a mixture obtained by mixing 100 g of side-chain primary aminopropyl-modified polydimethylsiloxane (AP3651, manufactured by Dow-Toray Industries, Inc., weight average molecular weight 30,000, amine equivalent 2,000) and 203 g of ethyl acetate was dehydrated for 15 hours at room temperature (25°C) using 15.2 g of molecular sieves. To the above-mentioned dehydrated ethyl acetate solution of 2-ethyl-2-oxazoline, 6.17 g (0.04 mol) of diethyl sulfate was added, and the mixture was heated under reflux at 80°C for 8 hours under a nitrogen atmosphere to synthesize terminally reactive poly(N-propionylethyleneimine). This terminally reactive poly(N-propionylethyleneimine) solution was added all at once to the above-mentioned dehydrated side-chain primary aminopropyl-modified polydimethylsiloxane solution, and the mixture was heated under reflux at 80°C for 10 hours. The reaction mixture was concentrated under reduced pressure to obtain an N-propionylethyleneimine-dimethylsiloxane copolymer (oxazoline-modified silicone 1) as a pale yellow solid (190 g, yield 95%). The mass ratio of the organopolysiloxane segment (a) in the final product was 0.50, the mass ratio of the poly(N-acylalkyleneimine) segment (b) was 0.50, and the weight-average molecular weight of the final product was 60,000. The obtained N-propionylethyleneimine-dimethylsiloxane copolymer (oxazoline-modified silicone 1) was dissolved in ethanol to a solids concentration of 50% by mass, thereby obtaining an ethanol solution of oxazoline-modified silicone 1.

[0160] <Production Example 2-2> (Production and Evaluation of Oxazoline-Modified Silicone 2) A mixture obtained by mixing 3.63 g (0.036 mol) of 2-ethyl-2-oxazoline and 8.46 g of ethyl acetate was subjected to a dehydration treatment using 0.6 g of molecular sieves (Zeorum A-4, manufactured by Tosoh Corporation) at 28° C. for 15 hours. Also, a mixture obtained by mixing 100 g of side-chain primary aminopropyl-modified polydimethylsiloxane (KF-8015, manufactured by Shin-Etsu Chemical Co., Ltd., weight average molecular weight 100,000, amine equivalent 20,000) and 203 g of ethyl acetate was subjected to a dehydration treatment using 15.2 g of molecular sieves at 28° C. for 15 hours. To the ethyl acetate solution of the dehydrated 2-ethyl-2-oxazoline, 0.54 g (0.0035 mol) of diethyl sulfate was added, and the mixture was heated under reflux at 80°C for 8 hours under a nitrogen atmosphere to synthesize terminally reactive poly(N-propionylethyleneimine). The number average molecular weight measured by gel permeation chromatography (GPC) was 1,200. This terminally reactive poly(N-propionylethyleneimine) solution was added all at once to the dehydrated side-chain primary aminopropyl-modified polydimethylsiloxane solution, and the mixture was heated under reflux at 80°C for 10 hours. The reaction mixture was concentrated under reduced pressure to obtain an N-propionylethyleneimine-dimethylsiloxane copolymer (oxazoline-modified silicone 2) as a white rubbery solid (102 g). In the final product, the mass ratio of the organopolysiloxane segment (a) constituting the main chain was 0.96, the mass ratio of the poly(N-acylalkyleneimine) segment (b) was 0.04, and the weight average molecular weight of the final product was 104000. The obtained N-propionylethyleneimine-dimethylsiloxane copolymer (oxazoline-modified silicone 2) was dissolved in ethanol to a solids concentration of 10 mass %, thereby obtaining an ethanol solution of oxazoline-modified silicone 2.

[0161] <Production Example 2-3> (Production and Evaluation of Oxazoline-Modified Silicone 3) 3.2 g (0.021 mol) of diethyl sulfate and 92.8 g (0.98 mol) of 2-ethyl-2-oxazoline were dissolved in 205 g of dehydrated ethyl acetate and heated under reflux at room temperature (80°C) for 8 hours under a nitrogen atmosphere to synthesize terminally reactive poly(N-propionylethyleneimine). The number average molecular weight was measured by GPC and found to be 5,200. Furthermore, 100 g of side-chain primary aminopropyl-modified polydimethylsiloxane (KF-864, manufactured by Shin-Etsu Chemical Co., Ltd., weight average molecular weight 50,000, amine equivalent 3,800) was mixed with ethyl acetate to give a 33% solution, yielding a mixed solution. The side-chain primary aminopropyl-modified polydimethylsiloxane solution was added all at once to the terminally reactive poly(N-propionylethyleneimine) solution, and the mixture was heated under reflux for 10 hours. The reaction mixture was concentrated under reduced pressure to obtain an N-propionylethyleneimine-dimethylsiloxane copolymer (oxazoline-modified silicone 3) as a pale yellow rubbery solid (188 g, yield 96%). The content ratio of organopolysiloxane segment (a) in the final product was 0.51, the mass ratio of poly(N-acylalkyleneimine) segment (b) was 0.49, and the weight average molecular weight was 98,000. The obtained N-propionylethyleneimine-dimethylsiloxane copolymer (oxazoline-modified silicone 3) was dissolved in ethanol to a solids concentration of 30 mass%, to obtain an ethanol solution of oxazoline-modified silicone 3.

[0162] The tensile modulus and elongation of the obtained Oxazoline-modified Silicones 1 to 3 were evaluated by the methods described above, and the results are shown in Table 2. The obtained Oxazoline-modified Silicones 1 to 3 are elastomers having rubber elasticity at 25°C.

[0163]

[0164] Production Example 3-1 (Preparation of Treatment Agent 1 as Treatment Agent A and Production of Treatment Agent 2) A silicone that is liquid at 25°C ("KF-96A-6cs" manufactured by Shin-Etsu Chemical Co., Ltd., treatment agent 1 as treatment agent A) was prepared. 1,824 parts by mass of this treatment agent 1 was treated under reduced pressure at 4 kPa, and 202.7 parts by mass of the oxazoline-modified silicone 2 obtained in Production Example 2-2 was added thereto, and the mixture was heated to 85°C to dissolve. The mixture was then cooled to 60°C to obtain 2,025 parts by mass of a gel-like substance composed of organopolysiloxane and silicone that is liquid at 25°C (treatment agent 2 as treatment agent A; concentration of oxazoline-modified silicone 2: 10% by mass).

[0165] Example 1 (Step (4-1)) 2 g of the dried cellulose particles (carrier cellulose particles 1) obtained in Production Example 1-1 were weighed and mixed with a solution prepared by dissolving approximately 2 g of an ethanol solution of the oxazoline-modified silicone 1 obtained in Production Example 2-1 as a functional substance in 16 g of ethanol. This mixture was stirred at room temperature (25°C) for 15 minutes and then dried under reduced pressure at 50°C and 50 hPa to remove the ethanol, yielding composite cellulose particles composed of 100 parts by mass of cellulose and 50 parts by mass of oxazoline-modified silicone. The resulting composite cellulose particles were crushed using a coffee mill or the like as necessary. The functional substance did not volatilize under the drying conditions described above, and the entire amount charged was contained in the composite cellulose particles. The same applies to the following Examples and Comparative Examples. The compressive modulus, elastic recovery, and median diameter of the resulting composite cellulose particles, as well as the content of the functional substance and softness, were evaluated using the methods described above. The results are shown in Table 3.

[0166] Examples 2 to 7, Comparative Examples 1 and 2 Using an ethanol solution of oxazoline-modified silicone 1, an ethanol solution of oxazoline-modified silicone 2, and an ethanol solution of oxazoline-modified silicone 3, composite cellulose particles were produced in the same manner as in Example 1, except that the amount of the ethanol solution used in Example 1 was changed so that the amount (charge amount) of the functional substance was as shown in Table 3 or Table 4. In Comparative Example 2, Salacos 913 (manufactured by The Nisshin Oillio Group, Ltd.; isotridecyl isononanoate), which is liquid at 25°C, was used as the functional substance. The compressive modulus, elastic recovery, and median diameter of the obtained composite cellulose particles, as well as the content of the functional substance and softness, were evaluated using the methods described above, and the results are shown in Tables 3 and 4.

[0167]

[0168]

[0169] Example 8 (Step (4-2)) 50 g (solids content 3.3% by mass) of the dehydrated cellulose particles (carrier cellulose particles 2) obtained in Production Example 1-2 was weighed, and approximately 3.3 g of an ethanol solution (50% by mass ethanol solution) of the oxazoline-modified silicone 1 obtained in Production Example 2-1 was added as a functional substance. This mixture was stirred at room temperature (25°C) for 15 minutes, and then dried under reduced pressure at 50°C and 50 hPa to distill off the ethanol, producing composite cellulose particles composed of 100 parts by mass of oxazoline-modified silicone per 100 parts by mass of cellulose. The compressive modulus, elastic recovery, and median diameter of the obtained composite cellulose particles, as well as the content and softness of the functional substance, were evaluated using the methods described above, and the results are shown in Table 5. Table 5 also shows Example 2 as an example in which the procedure for complexing the carrier cellulose particles and the functional substance was different but the content was the same.

[0170]

[0171] Example 9 (Step (5)) 14 g of the composite cellulose particles obtained in Example 4 were weighed and dispersed in 343 g of hexane. To this dispersion, a solution prepared by dissolving 7 g of silicone ("KF-96A-6cs" manufactured by Shin-Etsu Chemical Co., Ltd., treatment agent 1) that was liquid at 25°C in 343 g of hexane was added and mixed. This mixture was stirred at room temperature (25°C) for 60 minutes, and then dried under reduced pressure at 50°C and 50 hPa or less to distill off the hexane, thereby producing composite cellulose particles containing treatment agent A.

[0172] Example 10: 14 g of the composite cellulose particles obtained in Example 4 was weighed and dispersed in 420 g of hexane. To this dispersion was added a solution of 4.9 g of the gel-like substance obtained in Production Example 3-1 (treatment agent 2) dissolved in 490 g of hexane as treatment agent A, and the mixture was mixed. This mixture was stirred at room temperature (25°C) for 60 minutes and then dried under reduced pressure at 50°C and 50 hPa or less to remove the hexane, producing composite cellulose particles containing treatment agent A. The composite cellulose particles obtained in Examples 9 and 10 were evaluated for compressive modulus, elastic recovery, median diameter, functional substance content, and softness using the methods described above, and the results are shown in Table 6-1. Table 6-1 also includes Example 4, which was not treated with treatment agent A but had the same content.

[0173]

[0174] Example 11 Composite cellulose particles containing treating agent A were produced in the same manner as in Example 9, except that 3.5 g of treating agent 1 was used.

[0175] Example 12 Composite cellulose particles containing treating agent A were produced in the same manner as in Example 10, except that 9.8 g of treating agent 2 was used.

[0176] The composite cellulose particles obtained in Examples 11 and 12 were evaluated for compressive modulus, elastic recovery, median diameter, and content of functional substance by the above-described methods, and the results are shown in Table 6-2.

[0177]

[0178] Furthermore, 8.5 g of the composite cellulose particles obtained in Examples 2, 4, 6, 11, and 12 were blended with 100 g of powder foundation (containing composite cellulose particles), and a sensory evaluation of softness was performed. The composition of the powder foundation is shown in Table 7, and the evaluation results are shown in Table 8.

[0179]

[0180]

[0181] Tables 3 to 8 show that when the composite cellulose particles of this example are incorporated into cosmetics, they can provide an excellent feeling of softness during application, etc., of the cosmetics when applied to a target object. More specifically, in Examples 1 to 5, it can be seen that the softness can be improved by increasing the content of the functional substance. Furthermore, a comparison of Examples 2, 6, and 7 shows that the softness can be improved by using a functional substance with a lower tensile modulus. Furthermore, a comparison of Examples 2 and 8 shows that even when the same functional material is used, the compressive modulus and elastic recovery rate of the composite cellulose particles can be adjusted by the composite treatment method, while maintaining a good softness. Furthermore, a comparison of Examples 4, 9, 10, 11, and 12 shows that treating the composite cellulose particles with treatment agent A can improve the softness. Furthermore, it can be seen that the excellent softness characteristic of the composite cellulose particles can be provided even when the composite cellulose particles are incorporated as an ingredient in cosmetics, etc. In contrast, the composite cellulose particles of Comparative Example 1 had a low content of functional substance, resulting in a low elastic recovery rate and insufficient improvement in softness. Furthermore, in Comparative Example 2, even when liquid silicone oil at 25°C was compounded, the elastic recovery rate was extremely low and the softness was insufficient.

[0182] According to the present invention, it is possible to provide composite cellulose particles that, when blended in a cosmetic, can provide an excellent feeling of softness during the application action when applying the cosmetic to an object.

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 5% or more.

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 40 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 an elastomer.

5. Composite cellulose particles according to any one of claims 1 to 4, wherein the median diameter of the composite cellulose particles is 5 μm or more and 2000 μm or less.

6. The composite cellulose particles according to any one of claims 1 to 5, further comprising at least one member selected from the group consisting of silicone (c1) that is liquid at 25°C and gel-like substance (c2) that is composed of organopolysiloxane and silicone that is liquid at 25°C.

7. A cosmetic preparation containing 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 impregnating 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 used in the step (4-1) 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) 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 is 0.01g or less.

13. The 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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