WO2024106527A1 - 多孔質セルロース粒子 - Google Patents

多孔質セルロース粒子 Download PDF

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Publication number
WO2024106527A1
WO2024106527A1 PCT/JP2023/041400 JP2023041400W WO2024106527A1 WO 2024106527 A1 WO2024106527 A1 WO 2024106527A1 JP 2023041400 W JP2023041400 W JP 2023041400W WO 2024106527 A1 WO2024106527 A1 WO 2024106527A1
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Prior art keywords
cellulose
less
cellulose particles
particles
mass
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English (en)
French (fr)
Japanese (ja)
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祐輝 林
和聡 佐藤
翔午 石山
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Kao Corp
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Kao Corp
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Priority to CN202380072817.7A priority Critical patent/CN120019105A/zh
Priority to JP2024558951A priority patent/JPWO2024106527A1/ja
Priority to EP23891672.0A priority patent/EP4620997A1/en
Priority to KR1020257010335A priority patent/KR20250111094A/ko
Publication of WO2024106527A1 publication Critical patent/WO2024106527A1/ja
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/12—Powdering or granulating
    • C08J3/16—Powdering or granulating by coagulating dispersions
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K8/00—Cosmetics or similar toiletry preparations
    • A61K8/02—Cosmetics or similar toiletry preparations characterised by special physical form
    • A61K8/0241—Containing particulates characterized by their shape and/or structure
    • A61K8/0279—Porous; Hollow
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K8/00—Cosmetics or similar toiletry preparations
    • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
    • A61K8/72—Cosmetics or similar toiletry preparations characterised by the composition containing organic macromolecular compounds
    • A61K8/73—Polysaccharides
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K8/00—Cosmetics or similar toiletry preparations
    • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
    • A61K8/72—Cosmetics or similar toiletry preparations characterised by the composition containing organic macromolecular compounds
    • A61K8/73—Polysaccharides
    • A61K8/731—Cellulose; Quaternized cellulose derivatives
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
    • A61Q1/00—Make-up preparations; Body powders; Preparations for removing make-up
    • A61Q1/02—Preparations containing skin colorants, e.g. pigments
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
    • A61Q17/00—Barrier preparations; Preparations brought into direct contact with the skin for affording protection against external influences, e.g. sunlight, X-rays or other harmful rays, corrosive materials, bacteria or insect stings
    • A61Q17/04—Topical preparations for affording protection against sunlight or other radiation; Topical sun tanning preparations
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
    • A61Q19/00—Preparations for care of the skin
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B1/00—Preparatory treatment of cellulose for making derivatives thereof, e.g. pre-treatment, pre-soaking, activation
    • C08B1/08—Alkali cellulose
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
    • C08B15/08—Fractionation of cellulose, e.g. separation of cellulose crystallites
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K2800/00—Properties of cosmetic compositions or active ingredients thereof or formulation aids used therein and process related aspects
    • A61K2800/10—General cosmetic use
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K2800/00—Properties of cosmetic compositions or active ingredients thereof or formulation aids used therein and process related aspects
    • A61K2800/40—Chemical, physico-chemical or functional or structural properties of particular ingredients
    • A61K2800/41—Particular ingredients further characterized by their size
    • A61K2800/412—Microsized, i.e. having sizes between 0.1 and 100 microns
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
    • C08J2301/02—Cellulose; Modified cellulose
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
    • C08L1/02—Cellulose; Modified cellulose

Definitions

  • the present invention relates to porous cellulose particles.
  • biodegradable polymer particles made from natural polymeric materials have been attracting attention as particles that do not fall under the category of plastic microbeads.
  • One type of such polymer particle is cellulose particles that have not been chemically modified.
  • Porous cellulose particles are known as functional cellulose particles used in cosmetics. If the cellulose particles are porous, it is preferable that the functional substances in the cosmetics can be encapsulated inside the particles.
  • Patent Document 1 discloses porous cellulose microparticles for use as cosmetic additives, which have a crystal form of Type I, a specific surface area of 20 m2 /g or more, a porous structure in which pores with diameters of 0.01 ⁇ m or more have a volume of 0.3 cm3 /g or more, and an average particle size of at most 100 ⁇ m.
  • Patent Document 2 discloses porous cellulose particles formed by the aggregation of crystalline cellulose of type I crystal form, the porous cellulose particles having an average particle diameter d1 of 0.5 to less than 50 ⁇ m, a specific surface area of 25 to 1000 m 2 /g, and a sphericity of 0.85 or more, and describes that cosmetics containing the porous cellulose particles have excellent tactile properties.
  • Patent Document 3 describes that the method for producing porous cellulose particles includes dissolving cellulose diacetate in a solvent to prepare a cellulose diacetate solution, dispersing the cellulose diacetate solution in a medium that is not miscible with the cellulose diacetate solution to obtain a dispersion system, cooling the dispersion system, adding a poor solvent to the cooled dispersion system to precipitate cellulose diacetate particles, and saponifying the cellulose diacetate particles, which makes it possible to produce porous cellulose particles more easily without using harmful solvents.
  • Patent Document 4 discloses a method for producing porous cellulose beads, which is characterized by contacting a cellulose dispersion prepared by mixing an alkaline aqueous solution in a specified temperature range with cellulose with a coagulation solvent, and describes that it is possible to produce porous cellulose beads with high mechanical strength without using highly toxic and corrosive auxiliary materials and without going through complicated processes that are industrially disadvantageous.
  • Patent Document 5 discloses that cellulose is dissolved in an alkali-containing aqueous solution within a specified temperature range to prepare a cellulose solution, which is then heated under specified conditions to prepare an emulsion and precipitate cellulose beads, which are then crosslinked, thereby enabling the production of porous crosslinked cellulose beads having a pore structure suitable for antibody adsorption in a simple and efficient manner, without using highly toxic or corrosive auxiliary materials and without going through complicated processes that are industrially disadvantageous.
  • Patent Document 6 discloses cellulose microparticles having a particle size of 1 to 2500 ⁇ m, an average pore size of 200 to 1000 ⁇ m, a specific surface area of 500 to 800 m 2 /g, a water content of 86 to 93%, a pore volume of 1.00 to 5.00 ml/g, and a porosity of 90 to 95%, and a method for producing the same.
  • Functional particles incorporated into cosmetics are required to provide excellent texture, such as a soft feel and minimal roughness when applied. Furthermore, if the particles are porous, they should be able to encapsulate functional substances, and when the cosmetic is applied to an object, it is desirable for the particles to break down during application, allowing the functional substances to be gradually released onto the object.
  • the porous cellulose particles described in Patent Document 1 are crystalline cellulose of type I crystal form, and therefore are hard particles, and it is believed that a squeaking sensation occurs when the particles are broken down during application.
  • the pore volumes of the porous cellulose particles disclosed in the examples are all 1 mL/g or less, and it is believed that the encapsulation of functional substances is insufficient.
  • the porous cellulose particles described in Patent Document 2 are also aggregates of crystalline cellulose of type I crystal form. It is described that the porous cellulose particles have good tactile properties, but there is no description or suggestion about the inclusion and sustained release of functional substances.
  • the pore volumes of the porous cellulose particles disclosed in the examples of Patent Document 2 are all 1 mL/g or less, and it is considered that the inclusion of functional substances is insufficient.
  • the porous cellulose particles described in Patent Document 3 and the porous cellulose beads described in Patent Document 4 are both used as chromatography packings, etc., and since they have a large average particle size, they are considered to have poor texture when used in cosmetics. Furthermore, since particles used as chromatography packings are preferably strong, these documents do not suggest porous cellulose particles that collapse during application.
  • the porous cross-linked cellulose beads described in Patent Document 5 are hard particles due to the cross-linking treatment.
  • the cellulose beads are also described as being suitable for use as an adsorbent for chromatography, an affinity adsorbent, etc., and have a lower porosity than particles for cosmetic applications that are assumed to disintegrate during application.
  • the cellulose fine particles described in Patent Document 6 have a large specific surface area and a high moisture content.
  • the present invention relates to the provision of porous cellulose particles that can impart a soft feel when incorporated into cosmetics, are less rough when applied, and have excellent encapsulation properties for functional substances and excellent particle disintegration properties.
  • porous cellulose particles having a compressive modulus, specific surface area, and pore volume within specific ranges relate to the following.
  • a cosmetic preparation comprising the porous cellulose particles described in [1] above.
  • Step (I) A step of mixing raw cellulose with an aqueous alkali solution to prepare an aqueous cellulose solution.
  • Step (II) A step of mixing the aqueous cellulose solution with an organic solvent to prepare a cellulose emulsion.
  • Step (III) A step of mixing the cellulose emulsion with a cellulose non-solvent to precipitate crude cellulose particles and obtain a suspension containing the crude cellulose particles.
  • Step (IV) A step of subjecting the suspension containing the crude cellulose particles to solid-liquid separation, and then washing the obtained crude cellulose wet particles to obtain refined cellulose wet particles.
  • Step (V) A step of drying the refined cellulose wet particles to obtain porous cellulose particles.
  • the present invention provides porous cellulose particles that, when incorporated into cosmetics, can impart a soft feel, are less rough when applied, and have excellent encapsulation properties for functional substances and excellent particle disintegration properties.
  • 1 is an X-ray diffraction profile of raw cellulose (cellulose type I crystals) used in the examples. 1 is an X-ray diffraction profile of the porous cellulose particles (cellulose II type crystals) obtained in Example 1. 1 is an X-ray diffraction profile of the porous cellulose particles (amorphous) obtained in Example 4.
  • porous cellulose particles have a compressive modulus of elasticity of 50 MPa or less, a specific surface area of 100 m 2 /g or more and less than 500 m 2 /g, and a pore volume of 1.5 mL/g or more.
  • the porous cellulose particles of the present invention having the above-mentioned constitution, can impart a soft feel to a cosmetic preparation when blended therewith, have less roughness when applied, and are excellent in the inclusion of functional substances and in the disintegration of the particles. The reason for this is unclear, but is thought to be as follows.
  • the compressive elastic modulus of the porous cellulose particles it is possible to impart a soft feel, reduce roughness when applied to an object, and facilitate disintegration by the action of applying the particles to the object. It is also believed that by making the specific surface area and pore volume of the porous cellulose particles equal to or more than a predetermined value, it is possible to improve the inclusion ability of the functional substance.
  • the compressive elastic modulus of the porous 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, still more preferably 5.0 MPa or less, from the viewpoint of soft touch, less roughness when applied to an object, and improved disintegration by the application operation to an object.
  • the porous cellulose particles it is preferably 1.0 MPa or more, more preferably 2.0 MPa or more, still more preferably 3.0 MPa or more, still more preferably 4.0 MPa or more, still more preferably 4.9 MPa or more.
  • the compressive elastic modulus of the porous cellulose particles is 50 MPa or less, 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 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 3.0 MPa or more and 6.0 MPa or less, even more preferably 4.0 MPa or more and 5.3 MPa or less, even more preferably 4.0 MPa or more and 5.2 MPa or less, and even more preferably 4.9 MPa or more and 5.0 MPa or less.
  • the above-mentioned compressive elastic modulus is an apparent compressive elastic modulus of a single particle measured by a microcompression tester, and specifically, it can be measured by the method described in the Examples.
  • the compressive modulus of the porous cellulose particles can be adjusted, for example, by changing the degree of polymerization of the raw cellulose used in step (I) and the cellulose concentration in the aqueous solution prepared in step (I) in the manufacturing method of porous cellulose particles described later. Specifically, the compressive modulus of the obtained porous cellulose particles is increased by using a raw cellulose having a high degree of polymerization in step (I) or by increasing the cellulose concentration in the aqueous solution.
  • porous cellulose particles having a low compressive modulus can be obtained by using a raw cellulose having a low degree of polymerization in step (I) or by decreasing the cellulose concentration in the aqueous solution.
  • the median diameter ( D50 ) of the porous cellulose particles measured by a dry method is preferably 75 ⁇ m or less, more preferably 70 ⁇ m or less, even more preferably 65 ⁇ m or less, even more preferably 55 ⁇ m or less, even more preferably 40 ⁇ m or less, and even more preferably 30 ⁇ m or less, from the viewpoint of suppressing roughness when applied to an object. Also, from the viewpoint of improving the disintegration property by the application operation to an object, it is preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, and even more preferably 15 ⁇ m or more.
  • the median diameter of the porous cellulose particles measured by a dry method is preferably 5 ⁇ m or more and 75 ⁇ m or less, more preferably 5 ⁇ m or more and 70 ⁇ m or less, even more preferably 5 ⁇ m or more and 65 ⁇ m or less, even more preferably 5 ⁇ m or more and 55 ⁇ m or less, even more preferably 10 ⁇ m or more and 40 ⁇ m or less, and even more preferably 15 ⁇ m or more and 30 ⁇ m or less.
  • the median diameter of porous cellulose particles measured by a dry method is the 50% median diameter measured by using dried particles as a measurement sample and a particle size distribution measuring device using a laser diffraction/scattering method, and specifically, it can be measured by the method described in the examples.
  • the median diameter of the porous cellulose particles can be adjusted, for example, by changing the stirring speed when mixing the cellulose aqueous solution and the organic solvent in step (II) in the manufacturing method of the porous cellulose particles described later.
  • step (II) by increasing the stirring speed when mixing the cellulose aqueous solution and the organic solvent in step (II), the emulsion droplet diameter of the obtained cellulose emulsion becomes small, and as a result, porous cellulose particles with a small median diameter can be obtained.
  • step (II) by decreasing the stirring speed, the emulsion droplet diameter of the obtained cellulose emulsion becomes large, and as a result, porous cellulose particles with a large median diameter can be obtained.
  • the specific surface area of the porous cellulose particles is 100 m 2 /g or more, preferably 110 m 2 /g or more, more preferably 120 m 2 /g or more, even more preferably 130 m 2 /g or more, still more preferably 135 m 2 /g or more, still more preferably 140 m 2 /g or more, and even more preferably 144 m 2 /g or more.
  • the specific surface area is less than 500 m 2 /g, preferably 200 m 2 /g or less, more preferably 180 m 2 /g or less, and even more preferably 150 m 2 /g or less.
  • the specific surface area of the porous cellulose particles is 100 m 2 /g or more and less than 500 m 2 /g, preferably 100 m 2 /g or more and 200 m 2 /g or less, more preferably 110 m 2 /g or more and 180 m 2 /g or less, even more preferably 120 m 2 /g or more and 180 m 2 /g or less, even more preferably 130 m 2 /g or more and 150 m 2 /g or less, even more preferably 135 m 2 /g or more and 150 m 2 /g or less, even more preferably 140 m 2 /g or more and 150 m 2 /g or less, and even more preferably 144 m 2 /g or more and 150 m 2 /g or less.
  • the specific surface area is a value obtained by standardizing the sum of the surface areas of the fine surfaces inside the porous cellulose particles and the particle surfaces, measured by mercury intrusion porosimetry, by dividing it by the mass of the particles, and specifically, can be measured by the method described in the examples.
  • the specific surface area of the porous cellulose particles can be controlled, for example, by selecting the surface tension of the dispersion medium (organic solvent) used for the dispersion medium replacement performed as necessary in step (IV) and the drying method in step (V) in the manufacturing method of the porous cellulose particles described later.
  • step (IV) when the surface tension of the organic solvent used for the dispersion medium replacement in step (IV) is small, the capillary force accompanying the evaporation of the organic solvent is small, and the shrinkage of the cellulose particles during drying can be suppressed, and porous cellulose particles with a large specific surface area can be obtained.
  • step (V) even if a drying method such as freeze-drying in which the capillary force caused by the surface tension of the organic solvent does not work, the shrinkage of the cellulose particles during drying can be suppressed, and porous cellulose particles with a large specific surface area can be obtained.
  • the pore volume of the porous cellulose particles is 1.5 mL/g or more, preferably 2.0 mL/g or more, more preferably 2.5 mL/g or more, even more preferably 3.0 mL/g or more, even more preferably 3.5 mL/g or more, and even more preferably 4.0 mL/g or more, from the viewpoint of improving the encapsulation of the functional substance. Also, from the viewpoint of suppressing the collapse during the production process of the porous cellulose particles, it is preferably 8.0 mL/g or less, more preferably 7.0 mL/g or less, even more preferably 6.0 mL/g or less, and even more preferably 5.0 mL/g or less.
  • the pore volume of the porous cellulose particles is 1.5 mL/g or more, 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 2.5 mL/g or more and 6.0 mL/g or less, even more preferably 3.0 mL/g or more and 5.0 mL/g or less, even more preferably 3.5 mL/g or more and 5.0 mL/g or less, and even more preferably 4.0 mL/g or more and 5.0 mL/g or less.
  • the pore volume is a value obtained by standardizing the total volume of mercury that has invaded the pores inside the porous cellulose particles and the gaps between the particles, measured by mercury intrusion porosimetry, by dividing it by the mass of the particles, and specifically, can be measured by the method described in the examples.
  • the pore volume of the porous cellulose particles can be adjusted, for example, by the surface tension of the dispersion medium (organic solvent) used in the dispersion medium replacement performed as necessary in step (IV) in the manufacturing method of the porous cellulose particles described later, the selection of the drying method in step (V), and also by the emulsion droplet size of the cellulose emulsion obtained in step (II). Specifically, if the emulsion droplet size of the cellulose emulsion is small, the median diameter and pore volume of the obtained porous cellulose particles are also small.
  • the porous cellulose particles of the present invention are preferably not chemically modified porous cellulose particles from the viewpoint of environmental consideration.
  • “not chemically modified” means that (1) no substituent is substantially introduced to the hydroxyl group in the cellulose constituting the porous cellulose particles, and (2) the surface of the porous cellulose particles is not covered with a surface treatment agent.
  • the amount of the substituent introduced to the hydroxyl group in the cellulose constituting the porous cellulose particles is preferably 0.5 mol% or less, more preferably 0.1 mol% or less, and even more preferably 0 mol% in the total hydroxyl groups.
  • porous cellulose particles are preferably non-crosslinked particles from the viewpoints of imparting a soft feel, improving the encapsulation of functional substances, and improving disintegration properties when applied to an object.
  • Non-crosslinked particles refer to particles that are produced without intentional crosslinking reaction and have substantially no crosslinked structure.
  • the surface pore diameter of the porous cellulose particles is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more from the viewpoint of improving the inclusion of functional substances, and is preferably 800 nm or less, more preferably 600 nm or less, and even more preferably 500 nm or less from the viewpoint of having high particle strength and maintaining the particle shape.
  • the surface pore diameter of the porous cellulose particles is preferably 50 nm or more and 800 nm or less, more preferably 100 nm or more and 600 nm or less, and even more preferably 200 nm or more and 500 nm or less.
  • the surface pore size can be determined by mercury intrusion porosimetry, specifically, by the method described in the Examples.
  • the sphericity of the porous cellulose particles is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more, from the viewpoint of improving the feel when applied to an object and from the viewpoint of imparting appropriate particle disintegration.
  • the upper limit of the sphericity is 100%, and may be 90% or less.
  • the sphericity of the porous cellulose particles is a value defined by the following formula, and can be determined by measurement using a dynamic image analyzer CAMSIZER X2 (manufactured by MICROTRAC MRB). Specifically, the sphericity can be measured by the method described in the Examples.
  • Sphericity (%) 4 ⁇ ⁇ particle area (m 2 ) / (particle circumference (m)) 2 ⁇ 100
  • the cellulose constituting the porous cellulose particles is preferably made of cellulose II type crystalline cellulose or amorphous cellulose, rather than cellulose I type crystalline cellulose, from the viewpoint of imparting a soft feel and improving disintegratability when applied to a target object.
  • the crystalline form of the cellulose constituting the porous cellulose particles can be identified from the diffraction angle and diffraction intensity by X-ray diffraction.
  • the degree of crystallinity of cellulose type II is defined by the following formula, but the value is not particularly limited.
  • Cellulose type II crystallinity (%) [(I 20.0 ⁇ I 15.0 )/I 20.0 ] ⁇ 100
  • the cellulose type II crystallinity can be measured by X-ray diffraction, specifically by the method described in the Examples.
  • the crystal form of the porous cellulose particles (cellulose type II crystallinity) can be adjusted, for example, by the type of solvent contained in the purified wet cellulose particles when the drying treatment is carried out in step (V) in the manufacturing method of the porous cellulose particles described below. Although the reason is unclear, the crystallinity becomes high when the purified wet cellulose particles contain an aqueous solvent and the crystallinity becomes low when the purified wet cellulose particles contain a non-aqueous solvent and the drying treatment is carried out in step (V).
  • the physical properties of the porous cellulose particles can be adjusted, for example, by selecting suitable manufacturing conditions for the cellulose particles, the type of raw cellulose used to manufacture the cellulose particles, etc., as specifically described above.
  • the porous cellulose particles preferably have a low content of compounds other than cellulose, such as impurities contained in the raw cellulose, solvents used during production, and additives.
  • the cellulose content in the porous cellulose particles is preferably 95% by mass or more, more preferably 99% by mass or more, and even more preferably substantially 100% by mass.
  • the porous cellulose particles of the present invention can be produced preferably by a production method having the following steps (I) to (V) in this order.
  • Step (I) Mixing raw cellulose with an alkaline aqueous solution to prepare a cellulose aqueous solution.
  • Step (II) Mixing the cellulose aqueous solution with an organic solvent to prepare a cellulose emulsion.
  • Step (III) Mixing the cellulose emulsion with a cellulose non-solvent to precipitate coarse cellulose particles and obtain a suspension containing the coarse cellulose particles.
  • Step (V) Drying the purified cellulose wet particles to obtain porous cellulose particles.By using the above manufacturing method, porous cellulose particles having the above physical properties can be easily manufactured.
  • step (I) raw cellulose and an aqueous alkali solution are mixed to prepare an aqueous cellulose solution.
  • the aqueous cellulose solution prepared in step (I) is different from a suspension of cellulose and is a solution in which cellulose is dissolved in an aqueous alkali solution.
  • the state in which "cellulose is dissolved” means that the aqueous cellulose solution is transparent to the naked eye. Note that a part of the cellulose may be in a dispersed state.
  • step (I) it becomes easier to control the morphology inside the cellulose particles, and porous cellulose particles having the desired physical properties can be easily produced.
  • the raw cellulose used in step (I) is preferably chemically pure cellulose that is not chemically modified, from the viewpoint of environmental consideration.
  • various cellulose-containing raw materials can be used, such as wood such as various wood chips, pruned branches of various trees, thinned wood, branches, building waste, and factory waste; wood pulp produced from wood, pulp such as cotton linter pulp obtained from the fibers around cotton seeds; paper such as newspapers, cardboard, magazines, and high-quality paper; plant stems and leaves such as rice straw and corn stalks; and plant shells such as rice husks, palm shells, and coconut shells.
  • pulp such as various wood chips, pruned branches of various trees, thinned wood, branches, building 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.
  • the form of the raw material cellulose include powder, sheet, cotton, etc.
  • the raw material cellulose is preferably in the form of powder from the viewpoint of excellent solubility in an alkaline aqueous solution.
  • 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 still more preferably 150 or more, and from the viewpoint of improving the 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 still more preferably 150 or more and 300 or less.
  • the degree of polymerization of raw cellulose is generally controlled by the conditions of acid hydrolysis of raw pulp. For example, a longer acid hydrolysis time will give raw cellulose with a lower degree of polymerization.
  • either crystalline cellulose or amorphous cellulose can be used, but from the viewpoint of obtaining porous cellulose particles with 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.
  • the median diameter of the starting cellulose is preferably 10 ⁇ m or more, and more preferably 20 ⁇ m or more, from the viewpoint of improving handleability, and is preferably 500 ⁇ m or less, more preferably 300 ⁇ m or less, even more preferably 200 ⁇ m or less, and still more preferably 150 ⁇ m or less, from the viewpoint of improving solubility in an aqueous alkaline solution.
  • the median diameter of the starting cellulose can be measured in the same manner as described above.
  • the alkaline aqueous solution used in step (I) is not particularly limited as long as it is alkaline and can dissolve cellulose.
  • “capable of dissolving cellulose” refers to, for example, mixing cellulose in an alkaline aqueous solution in an amount that results in a 4% by mass solution, and visually confirming dissolution.
  • the alkali compound used in the alkaline aqueous solution may be either an inorganic alkali compound or an organic alkali compound, and examples thereof include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, lithium hydroxide, etc., ammonia, and tertiary amines such as trimethylamine, triethylamine, etc.
  • alkali metal hydroxides are preferred, one or more selected from the group consisting of sodium hydroxide and potassium hydroxide are more preferred, and sodium hydroxide is even more preferred.
  • the above alkaline compounds may be used alone or in combination of two or more kinds.
  • the concentration of the alkaline compound in the alkaline aqueous solution is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less.
  • the concentration of the alkaline compound in the alkaline aqueous 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.
  • aqueous alkaline solutions of different concentrations may be mixed with the starting cellulose in multiple batches.
  • the concentration of the alkaline compound in the aqueous alkaline solution A is more preferably from 2% by mass to 8% by mass, and further preferably from 2% by mass to 5% by mass.
  • the concentration of the alkaline compound in the alkaline aqueous solution B is more preferably 15% by mass or more and 30% by mass or less, and further preferably 20% by mass or more and 25% by mass or less.
  • the mass ratio of the alkaline aqueous solution A to the alkaline aqueous solution 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.
  • the mixing of the starting cellulose with the aqueous alkaline solution in step (I) can be carried out by adding the starting cellulose to the aqueous alkaline solution and stirring the mixture 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.
  • 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.
  • the stirring time depends on the production scale, the concentration of the alkaline compound in the alkaline aqueous solution, and the temperature, and is set appropriately, so there are no particular limitations. Usually, stirring is continued until the raw cellulose is dissolved as can be seen by visual inspection.
  • the cellulose concentration in the cellulose aqueous solution obtained in step (I) 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 improving the strength of the resulting porous cellulose particles. Also, from the viewpoint of making the viscosity of the cellulose aqueous solution easy to prepare a cellulose emulsion when it is subjected to step (II), it is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and even more preferably 6% by mass or less.
  • the cellulose concentration in the cellulose aqueous solution obtained in step (I) 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 8% by mass or less, and even more preferably 2% by mass or more and 6% by mass or less.
  • the alkali compound concentration in the cellulose aqueous solution obtained in step (I) is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 2% by mass or more, even more preferably 3% by mass or more, even more preferably 5% by mass or more, and 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 cellulose aqueous solution obtained in step (I) 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, even 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.
  • step (II) the aqueous cellulose solution obtained in step (I) is mixed with an organic solvent to prepare a cellulose emulsion.
  • step (II) a water-in-oil cellulose emulsion capable of producing porous cellulose particles having a desired median size can be prepared.
  • the organic solvent is not particularly limited as long as it is an organic solvent that can be mixed with the aqueous cellulose solution to prepare a cellulose emulsion and is immiscible with water.
  • Preferred organic solvents for use in step (II) include hydrocarbon solvents, ester solvents, halogenated solvents, etc.
  • hydrocarbon solvent examples include chain aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons.
  • the number of carbon atoms in the chain aliphatic hydrocarbon is preferably 6 or more, more preferably 8 or more, and is preferably 18 or less, more preferably 12 or less.
  • the chain aliphatic hydrocarbon may be either a linear aliphatic hydrocarbon or a branched aliphatic hydrocarbon.
  • the alicyclic hydrocarbons and aromatic hydrocarbons preferably have 6 or more and 18 or less carbon atoms, and more preferably 6 or more and 12 or less carbon atoms.
  • 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.
  • ester-based solvent an ester having 4 to 10 carbon atoms is preferable, and examples thereof include ethyl acetate and butyl acetate.
  • halogen-based solvents include dichloromethane, dichloroethane, and dichlorobenzene.
  • the organic solvents may be used alone or in combination of two or more.
  • the organic solvent is preferably a hydrocarbon solvent, more preferably a chain aliphatic hydrocarbon, even more 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 even more preferably one or more selected from the group consisting of n-octane, isooctane, n-decane, isodecane, n-dodecane, and isododecane.
  • the amount of the organic solvent mixed with the cellulose aqueous solution is preferably 80 parts by mass or more, more preferably 100 parts by mass or more, and even more preferably 120 parts by mass or more, relative to 100 parts by mass of the cellulose aqueous solution, from the viewpoint of improving the emulsion stability of the water-in-oil cellulose emulsion, and is preferably 1000 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 500 parts by mass or less, and even more preferably 300 parts by mass or less, from the viewpoint of easily obtaining porous cellulose particles having a desired median diameter.
  • the amount of the organic solvent mixed with the cellulose aqueous solution is preferably 80 parts by mass or more and 1000 parts by mass or less, more preferably 100 parts by mass or more and 800 parts by mass or less, even more preferably 120 parts by mass or more and 500 parts by mass or less, and even more preferably 120 parts by mass or more and 300 parts by mass or less, relative to 100 parts by mass of the cellulose aqueous solution.
  • step (II) from the viewpoint of improving the emulsion stability of the water-in-oil type cellulose emulsion, it is preferable to further mix an emulsifier in addition to the aqueous cellulose solution and the organic solvent.
  • the emulsifier include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, etc.
  • nonionic surfactants are preferred from the viewpoint of improving the emulsifiability of the water-in-oil type cellulose emulsion.
  • 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.
  • HLB is an index representing the ratio of the relative affinity of a surfactant to both liquids in an oil-water system, and can be calculated from the following formula using the Griffin method (J. Soc. Cosm.
  • HLB 20 x [(molecular weight of hydrophilic group contained in surfactant)/(molecular weight of surfactant)]
  • hydrophilic group contained in the surfactant include a hydroxy group and an ethyleneoxy group.
  • 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 mass of each nonionic surfactant divided by the total mass of the nonionic surfactants).
  • 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, sucrose fatty acid esters, polyether-modified silicones, and the like. These can be used alone or in combination of two or more.
  • the number of carbon atoms in the fatty acids in the sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitol fatty acid esters, polyglycerin fatty acid esters, and sucrose fatty acid esters, and in the alkyl groups in the polyoxyethylene alkyl ethers, is preferably 12 or more, more preferably 16 or more, even more preferably 18 or more, from the viewpoint of setting the HLB in the above-mentioned range, and is preferably 24 or less, more preferably 22 or less.
  • sorbitan fatty acid esters examples include sorbitan monooleate, sorbitan monostearate, sorbitan sesquioleate, sorbitan coconut oil fatty acid, sorbitan monopalmitate, sorbitan tristearate, and sorbitan trioleate.
  • polyoxyethylene sorbitan fatty acid esters examples include polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate.
  • polyoxyethylene alkyl ethers examples include polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether.
  • polyoxyethylene glycerin fatty acid esters examples include polyoxyethylene glyceryl monooleate.
  • polyoxyethylene sorbitol fatty acid esters examples include polyoxyethylene sorbitol tetraoleate.
  • sucrose fatty acid esters examples include sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate, and sucrose behenate.
  • the nonionic surfactant used as the emulsifier is preferably one or more selected from the group consisting of sorbitan fatty acid esters, polyoxyethylene alkyl ethers, sucrose fatty acid esters, and polyether-modified silicones, more preferably sucrose fatty acid esters, even more preferably one or more selected from the group consisting of sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate, and sucrose behenate, and even more preferably one or more selected from the group consisting of sucrose erucate and sucrose behenate.
  • the amount of the emulsifier mixed is, from the viewpoint of further improving the emulsion stability of the water-in-oil cellulose emulsion, preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1.0 parts by mass or more, and preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5.0 parts by mass or less, relative to 100 parts by mass of the organic solvent.
  • the amount of the emulsifier mixed is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, even more preferably 1.0 parts by mass or more and 5.0 parts by mass or less, relative to 100 parts by mass of the organic solvent.
  • the emulsifier may be added to either the aqueous cellulose solution or the organic solvent before mixing, or it may be added after the aqueous cellulose solution and the organic solvent are mixed.
  • 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 with a known mixer such as a homomixer or a high-speed emulsifying disperser.
  • the temperature at which the aqueous cellulose solution and the organic solvent are mixed is preferably 20° C. or lower, more preferably 10° C. or lower, and even more preferably 5° C. or lower, from the viewpoint of further improving the emulsion stability of the water-in-oil cellulose emulsion.
  • the temperature is preferably ⁇ 20° C.
  • the temperature at which the aqueous cellulose solution and the organic solvent are mixed is preferably ⁇ 20° C. or higher and 20° C. or lower, more preferably ⁇ 10° C. or higher and 10° C. or lower, and even more preferably ⁇ 5° C. or higher and 5° C. or lower.
  • 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 porous cellulose particles having the desired median size, it is preferably 1000 rpm or more, more preferably 3000 rpm or more, even more preferably 5000 rpm or more, even more preferably 5500 rpm or more, and preferably 15000 rpm or less, more preferably 12000 rpm or less, even more preferably 10000 rpm or less, even more preferably 8500 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 12000 rpm or less, even more preferably 5000 rpm or more and 10000 rpm or less, even more preferably 5500 rpm or more and 8500 rpm or less.
  • the mixing time of the cellulose aqueous solution and the organic solvent is appropriately selected depending on the production scale, the equipment used, the viscosity of the cellulose emulsion, etc.
  • step (III) the cellulose emulsion obtained in step (II) is mixed with a cellulose non-solvent to precipitate crude cellulose particles, thereby obtaining a suspension containing crude cellulose particles.
  • the cellulose non-solvent is a so-called cellulose non-solvent that does not dissolve cellulose, and is a solvent that is compatible with the alkaline aqueous solution and the organic solvent.
  • the cellulose non-solvent is preferably an alcohol-based solvent, more preferably an alcohol having 4 or less carbon atoms.
  • alcohols used as cellulose non-solvents include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and tert-butyl alcohol. These can be used alone or in combination of two or more.
  • the cellulose non-solvent is preferably at least one selected from the group consisting of ethanol, 2-propanol, 1-butanol, 2-butanol, and 2-methyl-1-propanol, more preferably ethanol, from the viewpoint of easily precipitating crude cellulose particles and controlling the internal morphology of the cellulose particles to obtain porous cellulose particles with the desired physical properties.
  • the amount of the cellulose non-solvent mixed is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, and even more preferably 200 parts by mass or more, relative to 100 parts by mass of the cellulose emulsion, from the viewpoint of easily precipitating crude cellulose particles, controlling the internal morphology of the cellulose particles to obtain porous cellulose particles having the desired physical properties, and maintaining the stability of the emulsion, and is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, and even more preferably 400 parts by mass or less.
  • the amount of the cellulose non-solvent mixed is preferably 50 parts by mass or more and 1000 parts by mass or less, more preferably 100 parts by mass or more and 500 parts by mass or less, and even more preferably 200 parts by mass or more and 400 parts by mass or less, relative to 100 parts by mass of the cellulose emulsion.
  • 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, an organic acid is preferred, and a carboxylic acid having 4 or less carbon atoms is more preferred.
  • 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.
  • a cellulose non-solvent preferably one or more selected from the group consisting of acetic acid, lactic acid, malic acid, and succinic acid, and more preferably acetic acid.
  • the amount of acid mixed is preferably 1.0 equivalent or more, more preferably 1.2 equivalent or more, and even more preferably 1.4 equivalent or more, relative to the alkali compound used in step (I) from the viewpoint of neutralizing the alkali compound remaining in the crude cellulose particles, and is preferably 3.0 equivalents or less, more preferably 2.0 equivalents or less, and even more preferably 1.8 equivalents or less, from the viewpoint of economy.
  • the amount of acid mixed in step (III) is preferably 1.0 equivalent 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 (I).
  • 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.
  • 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 combine the emulsion droplets together.
  • the temperature when the cellulose emulsion and the cellulose non-solvent are mixed is preferably 0° C. or higher, more preferably 5° C. or higher, and even more preferably 15° C. or higher, and is preferably 50° C. or lower, more preferably 40° C. or lower, and even more preferably 30° C. or lower.
  • the temperature when the cellulose emulsion and the cellulose non-solvent are mixed 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.
  • the acid When an acid is mixed in step (III), 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 mixing the cellulose emulsion and the cellulose non-solvent.
  • the stirring speed when mixing the cellulose emulsion and the cellulose non-solvent depends on the production scale and temperature and is appropriately set, but from the viewpoint of sufficiently precipitating the crude cellulose particles and controlling the morphology inside the cellulose particles to obtain porous cellulose particles having 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 when mixing 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 crude cellulose particles and controlling the internal morphology of the cellulose particles to obtain porous cellulose particles having 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.
  • step (IV) the suspension containing the crude cellulose particles obtained in step (III) is subjected to solid-liquid separation, and the obtained crude wet cellulose particles are then washed to obtain purified wet cellulose particles.
  • the solid-liquid separation of the suspension containing the crude cellulose particles can be carried out by centrifugation, filtration, decantation, or a combination of these.
  • the crude cellulose wet particles obtained after solid-liquid separation are washed to remove impurities such as the organic solvent and emulsifier used in step (II) and the neutralization salt generated in step (III).
  • the crude cellulose wet particles can be washed using water, an organic solvent, or a combination of these.
  • An organic solvent is preferably used to remove hydrophobic impurities such as the organic solvent and emulsifier used in step (II), and water is preferably used to remove water-soluble impurities such as the neutralization salt.
  • the organic solvent used in the washing treatment of the wet crude cellulose particles in step (IV) is preferably one that can dissolve the organic solvent and emulsifier used in step (II) and is easy to dry, such as ketone-based solvents with 6 or less carbon atoms, such as acetone and methyl isobutyl ketone, and alcohol-based solvents with 6 or less carbon atoms, such as ethanol and 2-propanol.
  • ketone-based solvents with 6 or less carbon atoms such as acetone and methyl isobutyl ketone
  • alcohol-based solvents with 6 or less carbon atoms such as ethanol and 2-propanol.
  • the dispersion medium used for dispersion medium replacement is preferably an organic solvent with low surface tension from the viewpoint of suppressing shrinkage of the resulting porous cellulose particles during drying, and is preferably an organic solvent having a surface tension of preferably 20 mN/m or less, more preferably 18 mN/m or less at 25°C.
  • the above surface tension is a surface tension value measured at 25° C. using an automatic surface tensiometer (K100 manufactured by KRUSS).
  • the above-mentioned low surface tension organic solvents include, for example, 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.
  • pentane is preferred from the viewpoint of suppressing shrinkage of the resulting porous cellulose particles during drying.
  • the amount of the dispersion medium used for the dispersion medium replacement is preferably 100 parts by mass or more, more preferably 200 parts by mass or more, and preferably 2000 parts by mass or less, more preferably 1000 parts by mass or less, and even more preferably 600 parts by mass or less, relative to 100 parts by mass of the cellulose particles after the above-mentioned washing treatment.
  • the amount of the dispersion medium used for the dispersion medium replacement is preferably 100 parts by mass or more and 2000 parts by mass or less, more preferably 200 parts by mass or more and 1000 parts by mass or less, and even more preferably 200 parts by mass or more and 600 parts by mass or less, relative to 100 parts by mass of the cellulose particles after the above-mentioned washing treatment.
  • the dispersion medium replacement can be carried out, for example, by adding the cellulose particles after the washing treatment to the dispersion medium and stirring using a known device.
  • the temperature when the cellulose particles after the washing treatment and the dispersion medium are mixed is preferably 0°C or higher, more preferably 5°C or higher, even more preferably 15°C or higher, and is preferably 50°C or lower, more preferably 40°C or lower, and even more preferably 30°C or lower.
  • the temperature when the cellulose particles after the washing treatment and the dispersion medium are mixed 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.
  • the stirring speed when mixing the cellulose particles and the dispersion medium after the washing treatment depends on the production scale and temperature and is appropriately set, but from the viewpoint of sufficiently dispersing the cellulose particles, it is preferably 100 rpm or more, more preferably 200 rpm or more, and 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 when mixing the cellulose particles and the dispersion medium after the washing treatment 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 for mixing the washed cellulose particles with the dispersion medium depends on the production scale and temperature and is appropriately set, but is usually from 0.2 hours to 12 hours, preferably from 0.5 hours to 6 hours.
  • a suspension containing purified cellulose particles is obtained.
  • the suspension can be subjected to solid-liquid separation in the same manner as above to recover the purified cellulose wet particles.
  • Step (V)> the purified wet cellulose particles obtained in the step (IV) are dried to obtain dry porous cellulose particles.
  • a method for drying the purified cellulose wet particles from the viewpoint of suppressing shrinkage of the particles during drying and maintaining the porous structure, it is preferable to use a freeze-drying method.
  • the drying treatment can also be performed by drying under reduced pressure, drying with supercritical carbon dioxide, etc.
  • the freeze-drying is preferably carried out by pre-freezing the purified cellulose wet particles and then carrying out primary and secondary drying.
  • Pre-freezing is preferably performed by rapid freezing at normal pressure at a temperature of ⁇ 200° C. to ⁇ 50° C. Then, it is preferable to perform primary drying in which ice in the pre-frozen product is sublimated under a vacuum of 0.1 Pa to 100 Pa and a temperature of ⁇ 20° C. to ⁇ 5° C., and then perform secondary drying by raising the temperature to a temperature of 20° C. to 40° C. under a vacuum of 0.1 Pa to 100 Pa.
  • the present invention further provides a cosmetic preparation comprising the porous cellulose particles.
  • the cosmetic of the present invention can provide a good feel by containing the porous cellulose particles. Furthermore, since the porous cellulose particles are excellent in the inclusion of functional substances and in the disintegration of particles, the cosmetic containing the porous cellulose particles can gradually release the functional substances to the target object by application. From the viewpoint of effectively exerting the above-mentioned effects, the cosmetic of the present invention is preferably a cosmetic for skin, and examples of the cosmetic for skin include foundation, makeup base, sunscreen, milky lotion, and the like.
  • the content of the porous cellulose particles in the cosmetic may be any amount that can exhibit the desired performance and can be appropriately selected depending on the type and form 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.
  • porous cellulose particles of the present invention can also be incorporated or used in applications other than cosmetics, such as toiletries, oral care products, quasi-drugs, pharmaceuticals, household products, agricultural products, and the like. Furthermore, since the porous 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.
  • the compressive elastic modulus is 50 MPa or less
  • the specific surface area is 100 m 2 /g or more and less than 500 m 2 /g
  • ⁇ 3> The porous cellulose particles of ⁇ 1> or ⁇ 2>, wherein the compressive elastic modulus of the porous cellulose particles is preferably 1.0 MPa or more, more preferably 2.0 MPa or more, even more preferably 3.0 MPa or more, even more preferably 4.0 MPa or more, and even more preferably 4.9 MPa or more.
  • ⁇ 4> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 3>, wherein the porous cellulose particles have a median diameter of 75 ⁇ m or less as measured by a dry method.
  • the porous cellulose particles according to any one of ⁇ 1> to ⁇ 4>, wherein the median diameter ( D50 ) of the porous cellulose particles measured by a dry method is preferably 75 ⁇ m or less, more preferably 70 ⁇ m or less, even more preferably 65 ⁇ m or less, still more preferably 55 ⁇ m or less, still more preferably 40 ⁇ m or less, and still more preferably 30 ⁇ m or less.
  • porous cellulose particles according to any one of ⁇ 1> to ⁇ 6>, wherein the specific surface area of the porous cellulose particles is preferably 110 m 2 /g or more, more preferably 120 m 2 /g or more, even more preferably 130 m 2 /g or more, still more preferably 135 m 2 /g or more, even more preferably 140 m 2 /g or more, and still more preferably 144 m 2 /g or more.
  • porous cellulose particles according to any one of ⁇ 1> to ⁇ 7> wherein the specific surface area of the porous cellulose particles is preferably 200 m 2 /g or less, more preferably 180 m 2 /g or less, and even more preferably 150 m 2 /g or less.
  • pore volume of the porous cellulose particles is preferably 2.0 mL/g or more, more preferably 2.5 mL/g or more, even more preferably 3.0 mL/g or more, still more preferably 3.5 mL/g or more, and still more preferably 4.0 mL/g or more.
  • porous cellulose particles according to any one of ⁇ 1> to ⁇ 9>, wherein the pore volume of the porous 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, and still more preferably 5.0 mL/g or less.
  • ⁇ 11> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 10>, wherein the sphericity of the porous cellulose particles is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.
  • ⁇ 12> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 11>, wherein the surface pore size of the porous cellulose particles is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 200 nm or more.
  • ⁇ 13> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 12>, wherein the surface pore size of the porous cellulose particles is preferably 800 nm or less, more preferably 600 nm or less, and even more preferably 500 nm or less.
  • ⁇ 14> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 13>, wherein the porous cellulose particles are not chemically modified.
  • ⁇ 15> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 14>, wherein the porous cellulose particles are non-crosslinked particles.
  • ⁇ 16> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 15>, wherein the cellulose constituting the porous cellulose particles is made of cellulose II type crystalline cellulose or amorphous cellulose.
  • ⁇ 17> The porous cellulose particles according to any one of ⁇ 1> to ⁇ 16>, wherein the content of cellulose in the porous cellulose particles is preferably 95% by mass or more, more preferably 99% by mass or more, and even more preferably substantially 100% by mass.
  • a cosmetic preparation comprising the porous cellulose particles according to any one of ⁇ 1> to ⁇ 17>.
  • Step (I) A step of mixing a raw cellulose with an aqueous alkali solution to prepare an aqueous cellulose solution.
  • Step (II) A step of mixing the aqueous cellulose solution with an organic solvent to prepare a cellulose emulsion.
  • Step (III) A step of mixing the cellulose emulsion with a cellulose non-solvent to precipitate crude cellulose particles and obtain a suspension containing the crude cellulose particles.
  • Step (IV) A step of subjecting the suspension containing the crude cellulose particles to solid-liquid separation, and then washing the obtained crude cellulose wet particles to obtain refined cellulose wet particles.
  • ⁇ 21> The method for producing porous cellulose particles according to ⁇ 19> or ⁇ 20>, wherein the starting cellulose used in the step (I) is in the form of a powder, a sheet, or a cotton, and is preferably in the form of a powder.
  • ⁇ 22> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 21>, wherein the degree of polymerization of the starting cellulose used in the step (I) is preferably 10 or more, more preferably 50 or more, even more preferably 100 or more, still more preferably 150 or more, and is preferably 1,000 or less, more preferably 500 or less, and even more preferably 300 or less.
  • ⁇ 23> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 22>, wherein the starting cellulose used in the step (I) is preferably crystalline cellulose, more preferably cellulose I type crystalline cellulose.
  • the starting cellulose used in the step (I) is in a powdery form, and the starting cellulose has a median diameter of preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, and preferably 500 ⁇ m or less, more preferably 300 ⁇ m or less, even more preferably 200 ⁇ m or less, and still more preferably 150 ⁇ m or less.
  • the alkali compound used in the alkaline aqueous solution is preferably an alkali metal hydroxide, more preferably at least one selected from the group consisting of sodium hydroxide and potassium hydroxide, and even more preferably sodium hydroxide.
  • ⁇ 26> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 25>, wherein the concentration of the alkali compound in the alkaline aqueous solution used in the step (I) is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less.
  • ⁇ 27> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 26>, wherein in the step (I), aqueous alkaline solutions having different concentrations are mixed with the starting cellulose in a plurality of batches.
  • ⁇ 28> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 27>, wherein in the step (I), the starting cellulose is mixed with an aqueous alkali solution A having an alkali compound concentration of 1 mass% or more and 10 mass% or less, and then an aqueous alkali solution B having an alkali compound concentration of more than 10 mass% and 40 mass% or less is added and mixed to prepare an aqueous cellulose solution.
  • ⁇ 29> The method for producing porous cellulose particles according to ⁇ 28>, wherein the concentration of the alkali compound in the alkaline aqueous solution A is more preferably 2% by mass or more and 8% by mass or less, and further preferably 2% by mass or more and 5% by mass or less.
  • concentration of the alkali compound in the 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.
  • ⁇ 31> The method for producing porous cellulose particles according to any one of ⁇ 28> to ⁇ 30>, wherein a mass ratio (A/B) of the alkaline aqueous solution A to the alkaline aqueous solution B is preferably 1 or more and 10 or less, more preferably 2 or more and 8 or less, and further preferably 3 or more and 6 or less.
  • ⁇ 32> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 31>, wherein in the step (I), the temperature during mixing of the starting cellulose and the aqueous alkaline solution is preferably 10° C. or lower, more preferably 5° C. or lower, even more preferably 0° C. or lower, and is preferably ⁇ 20° C.
  • step (I) The method for producing porous cellulose particles according to any one of ⁇ 28> to ⁇ 30>, wherein in the step (I), the starting cellulose is added to the aqueous alkaline solution A and mixed by stirring, and then the temperature of the mixture is adjusted to preferably 10° C. or less, more preferably 5° C. or less, even more preferably 0° C. or less, and preferably ⁇ 20° C. or more, more preferably ⁇ 10° C. or more, even more preferably ⁇ 5° C. or more, and then the aqueous alkaline solution B is added and mixed.
  • ⁇ 34> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 33>, wherein the cellulose concentration of the aqueous cellulose solution obtained in the step (I) is 1% by mass or more and 8% by mass or less.
  • ⁇ 35> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 34>, wherein the concentration of the alkali compound in the aqueous cellulose solution obtained in the step (I) 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, still more preferably 5% by mass or more, and is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less.
  • ⁇ 36> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 35>, wherein the organic solvent used in the step (II) is a hydrocarbon solvent, more preferably a chain aliphatic hydrocarbon, 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.
  • the organic solvent used in the step (II) is a hydrocarbon solvent, more preferably a chain ali
  • ⁇ 37> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 36>, wherein an emulsifier is further mixed in the step (II).
  • the emulsifier is a nonionic surfactant, preferably one or more selected from the group consisting of sorbitan fatty acid esters, polyoxyethylene alkyl ethers, sucrose fatty acid esters, and polyether-modified silicones, more preferably one or more selected from the group consisting of sucrose fatty acid esters, even more preferably one or more selected from the group consisting of sucrose palmitate, sucrose oleate, sucrose stearate, sucrose erucate, and sucrose behenate, and still more preferably one or more selected from the group consisting of sucrose erucate and sucrose behenate.
  • the amount of the emulsifier mixed in the step (II) is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, even more preferably 1.0 part by mass or more, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5.0 parts by mass or less, relative to 100 parts by mass of the organic solvent.
  • ⁇ 41> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 40>, wherein in the step (II), the temperature during mixing of the aqueous cellulose solution and the organic solvent is preferably 20° C. or lower, more preferably 10° C. or lower, even more preferably 5° C. or lower, and is preferably ⁇ 20° C. or higher, more preferably ⁇ 10° C. or higher, even more preferably ⁇ 5° C. or higher.
  • the stirring speed when mixing the aqueous cellulose solution and the organic solvent is preferably 1000 rpm or more, more preferably 3000 rpm or more, even more preferably 5000 rpm or more, still more preferably 5500 rpm or more, and is preferably 15000 rpm or less, more preferably 12000 rpm or less, even more preferably 10000 rpm or less, and still more preferably 8500 rpm or less.
  • ⁇ 43> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 42>, wherein the cellulose nonsolvent used in the step (III) is an alcohol having 4 or less carbon atoms.
  • the cellulose non-solvent used in the step (III) is preferably at least one selected from the group consisting of ethanol, 2-propanol, 1-butanol, 2-butanol, and 2-methyl-1-propanol, and more preferably ethanol.
  • ⁇ 45> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 44>, wherein the amount of the cellulose non-solvent used in the step (III) is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, even more preferably 200 parts by mass or more, and is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 400 parts by mass or less, relative to 100 parts by mass of the cellulose emulsion.
  • ⁇ 46> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 45>, wherein an acid is further mixed in the step (III).
  • ⁇ 47> The method for producing porous cellulose particles according to ⁇ 46>, wherein the acid mixed in the step (III) is preferably an organic acid, more preferably a carboxylic acid having 4 or less carbon atoms.
  • the amount of the acid mixed in the step (III) is preferably 1.0 equivalent or more, more preferably 1.2 equivalent or more, even more preferably 1.4 equivalent or more, and is preferably 3.0 equivalent or less, more preferably 2.0 equivalent or less, even more preferably 1.8 equivalent or less, relative to the amount of the alkali compound used in the step (I).
  • ⁇ 49> The method for producing porous cellulose particles according to any one of ⁇ 46> to ⁇ 48>, wherein in the step (III), the cellulose emulsion and the non-solvent for cellulose are mixed, and then the acid is mixed therewith.
  • ⁇ 50> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 49>, wherein in the step (III), the temperature during mixing of 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 is preferably 50° C. or lower, more preferably 40° C. or lower, even more preferably 30° C. or lower.
  • the stirring speed when mixing the cellulose emulsion and the cellulose non-solvent is preferably 100 rpm or more, more preferably 200 rpm or more, and is preferably 2000 rpm or less, more preferably 1500 rpm or less, even more preferably 1000 rpm or less, and further more preferably 800 rpm or less.
  • ⁇ 52> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 51>, wherein in the step (III), a stirring time during mixing of the cellulose emulsion and the cellulose non-solvent is from 0.2 hours to 12 hours, preferably from 0.5 hours to 6 hours.
  • step (III) a stirring time during mixing of the cellulose emulsion and the cellulose non-solvent is from 0.2 hours to 12 hours, preferably from 0.5 hours to 6 hours.
  • step (IV) solid-liquid separation of the suspension containing the crude cellulose particles obtained in the step (III) is carried out by centrifugation, filtration, decantation, or a combination thereof.
  • ⁇ 54> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 53>, wherein in the step (IV), the crude wet cellulose particles obtained after the solid-liquid separation are washed with water, an organic solvent, or a combination thereof.
  • the organic solvent is a ketone-based solvent having 6 or less carbon atoms or an alcohol-based solvent having 6 or less carbon atoms, and is preferably acetone, methyl isobutyl ketone, ethanol or 2-propanol.
  • ⁇ 56> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 55>, wherein in the step (IV), the cellulose particles obtained after the washing treatment are dispersed in a dispersion medium to replace the dispersion medium, and then dried under reduced pressure.
  • the dispersion medium used in the dispersion medium replacement is an organic solvent having a surface tension at 25° C. of preferably 20 mN/m or less, more preferably 18 mN/m or less, and is preferably pentane.
  • ⁇ 58> The method for producing porous cellulose particles according to ⁇ 56> or ⁇ 57>, wherein in the step (IV), the amount of the dispersion medium used in the dispersion medium replacement is preferably at least 100 parts by mass, more preferably at least 200 parts by mass, and is preferably at most 2,000 parts by mass, more preferably at most 1,000 parts by mass, and even more preferably at most 600 parts by mass, relative to 100 parts by mass of the cellulose particles after the washing treatment.
  • ⁇ 59> The method for producing porous cellulose particles according to any one of ⁇ 56> to ⁇ 58>, wherein in the step (IV), the temperature at the time of mixing the cellulose particles after the washing treatment with the dispersion medium is preferably 0° C.
  • the stirring speed when mixing the cellulose particles after the washing treatment with the dispersion medium is preferably 100 rpm or more, more preferably 200 rpm or more, and 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.
  • ⁇ 61> The method for producing porous cellulose particles according to any one of ⁇ 56> to ⁇ 60>, wherein in the step (IV), the suspension obtained by the dispersion medium replacement is subjected to solid-liquid separation to recover purified wet cellulose particles.
  • ⁇ 62> The method for producing porous cellulose particles according to any one of ⁇ 19> to ⁇ 61>, wherein in the step (V), the drying treatment is performed by freeze-drying.
  • the freeze-drying method is a method in which the purified wet cellulose particles are pre-frozen, and then primary and secondary drying are performed.
  • ⁇ 64> The method for producing porous cellulose particles according to ⁇ 63>, wherein in the pre-freezing, rapid freezing is performed under normal pressure at a temperature of -200°C or more and -50°C or less, and primary drying is performed by sublimating ice in the pre-frozen product preferably under a vacuum of 0.1 Pa or more and 100 Pa or less and at a temperature of -20°C or more and -5°C or less, and then secondary drying is performed by raising the temperature to a temperature of 20°C or more and 40°C or less under a vacuum of 0.1 Pa or more and 100 Pa or less.
  • the measurement conditions are as follows.
  • X-ray source: Cu/K ⁇ -radiation Measurement range: 2 ⁇ 5 to 50°
  • X [(I 20.0 - I 15.0 ) / I 20.0 ] x 100
  • the compressive modulus of the cellulose particles is measured using a microcompression tester ("MCT-510" manufactured by Shimadzu Corporation). Specifically, the cellulose particles are placed on a measurement stage attached to the above-mentioned device, and the diameter d is measured. The indenter ( ⁇ 50 ⁇ m) is lowered at a constant load rate (mN/sec) to compress the particles until a specified test force (0.98 mN) is reached. The compressive stress is calculated from the particle size d ( ⁇ m) and the test force P (mN) using the following formula.
  • Compressive stress (MPa) 2.48 ⁇ P (mN) / ( ⁇ ⁇ (d ( ⁇ m)) 2 )
  • the compressive strain is calculated from the displacement x ( ⁇ m) and the particle size d ( ⁇ m) using the following formula.
  • Compressive strain (%) x ( ⁇ m) / d ( ⁇ m) ⁇ 100
  • a stress-strain curve is created from the calculated compressive stress and compressive strain, and the compressive elastic modulus is calculated from the slope of the elastic region (0-10%). Measurements are carried out seven times, and the average of the five measurements excluding the maximum and minimum values is taken as the test result.
  • the median diameter ( D50 ) of the cellulose particles is measured using a laser scattering particle size distribution analyzer (LS 13 320, manufactured by Beckman Coulter, Inc.). Specifically, 50 mg of dried cellulose particles are weighed into a measurement cell and measured using a Tornado dry powder module to determine the particle diameter at 50% in the volume distribution of particle diameters. During the measurement, the actual refractive index of cellulose, 1.469, is input.
  • the specific surface area of cellulose particles is measured by the following method. Mercury is injected into the cellulose particles by mercury intrusion porosimetry using a mercury porosimeter (Shimadzu Corporation's "Auto Pore IV 9500"), and the total value X ( m2 ) of the surface area of the fine surfaces inside the cellulose particles and the particle surfaces is determined. Specifically, about 0.05 g of cellulose particles is placed in the cell of the mercury porosimeter, and measurement is performed by mercury intrusion porosimetry at measurement pressures ranging from 0.01 MPa to 210 MPa to determine the value of X ( m2 ). The mass of the cellulose particles used as the measurement sample is defined as Y (g), and the value of X ( m2 )/Y (g) is defined as the specific surface area of the cellulose particles.
  • ⁇ Pore volume> The pore volume of the cellulose particles is measured by the following method. Mercury is injected into the cellulose particles by mercury intrusion porosimetry using a mercury porosimeter (Shimadzu Corporation, "Auto Pore IV 9500"), and the total volume Z (mL) of the mercury that has invaded the pores in the cellulose particles and the gaps between the cellulose particles is determined. Specifically, about 0.05 g of cellulose particles is placed in the cell of the mercury porosimeter, and measurement is performed by mercury intrusion porosimetry at a measurement pressure range of 0.01 MPa to 210 MPa to determine the value of Z (mL). The mass of the cellulose particles used as the measurement sample is defined as Y (g), and the value of Z (mL)/Y (g) is defined as the pore volume of the cellulose particles.
  • the surface pore size of the cellulose particles is measured by the following method.
  • Mercury is injected into the cellulose particles by mercury intrusion porosimetry using a mercury porosimeter (Shimadzu Corporation "Auto Pore IV 9500"), and the pore distribution in the cellulose particles is obtained.
  • about 0.05 g of cellulose particles is first placed in the cell of the mercury porosimeter, and measurement is performed by mercury intrusion porosimetry at a measurement pressure ranging from 0.01 MPa to 210 MPa, and the pore volume of the cellulose particles: Z (mL) / Y (g) is obtained by the same method as above.
  • the horizontal axis is plotted as the pore diameter (nm) and the vertical axis is plotted as the pore volume (mL / g) to obtain an integrated pore distribution curve.
  • the above (integrated) pore volume is differentiated by the pore diameter, that is, the increase in the pore volume at each pore diameter is taken as the differential pore volume (mL / g).
  • the horizontal axis is plotted as the pore diameter (nm) and the vertical axis is plotted as the differential pore volume (mL / g) to obtain a pore distribution curve.
  • the most frequent pore size in the region of pore sizes of 1000 nm or less is regarded as the surface pore size of the particle.
  • ⁇ Texture> Approximately 5 mg of cellulose particles were applied to an area of 4 cm x 5 cm on the right forearm of an expert panelist to give a coverage of 0.25 mg/ cm2 , and the softness and lack of roughness were evaluated by sensory evaluation according to the following criteria. 5: Very soft and smooth, 4: Soft and smooth, 3: No hardness or roughness, 2: Hard and rough, 1: Very hard and rough
  • ⁇ Inclusion rate of functional substance (Nile Red)> Approximately 50 mg of cellulose particles are weighed out and mixed with a solution in which approximately 50 mg of the functional substance Nile Red (Tokyo Chemical Industry Co., Ltd.) is dissolved in 20 mL of ethanol. After stirring overnight, the mixture is vacuum dried at 60°C to remove the ethanol, and composite particles consisting of cellulose particles and Nile Red are obtained. The composite particles obtained are taken out, and the Nile Red encapsulated in the particles is extracted using 50 mL of o-xylene. The amount of Nile Red extracted is quantified by ultraviolet-visible absorption measurement, and the encapsulation rate is calculated using the following formula.
  • Encapsulation rate (%) (amount of Nile Red extracted (mg))/(amount of Nile Red used (mg)) ⁇ 100
  • the inclusion rate is scored according to the following criteria. 5: 80% or more, 4: 60% or more but less than 80%, 3: 40% or more but less than 60%, 2: 20% or more but less than 40%, 1: Less than 20%
  • ⁇ Disintegration due to abrasion> Approximately 20 mg of cellulose particles are weighed and placed on artificial leather (Laforet S2923, 5 cm x 4 cm). Using a surface property tester ("Tribogear TYPE14" manufactured by Shinto Scientific Co., Ltd.), a vertical load of 200 g equivalent to the application operation is applied, and the surface is rubbed back and forth 20 times at a moving distance of 50 mm and a moving speed of 2000 mm/min. The cellulose particles remaining on the artificial leather surface are observed under conditions of an acceleration voltage of 5.0 kV and an observation magnification of 500 times using a scanning electron microscope (SEM, "JSM-IT-500HR” manufactured by JEOL Ltd.).
  • SEM scanning electron microscope
  • the proportion of particles that have been flattened (disintegrated) by rubbing among 20 cellulose particles in the observed image is calculated as the disintegration rate, and scored according to the following criteria. 5: 80% or more, 4: 60% or more but less than 80%, 3: 40% or more but less than 60%, 2: 20% or more but less than 40%, 1: Less than 20%
  • Example 1 (Production and evaluation of porous cellulose particles)
  • cellulose I type crystalline cellulose powder As the raw material cellulose, cellulose I type crystalline cellulose powder (Avicel PH-101 manufactured by Asahi Kasei Corporation, polymerization degree: 170, median diameter: 50 ⁇ m, moisture content: 6%) was used. 10.6 g of the above cellulose powder was added to 189.4 g of a dilute NaOH aqueous solution (NaOH concentration: 4.2% by mass) and cooled to ⁇ 2° C.
  • aqueous cellulose solution had a cellulose concentration of 4 mass % and a NaOH concentration of 7.6 mass %.
  • Step (II) To the cellulose aqueous solution, 350 g of isododecane and 3.5 g of sucrose erucate ester (manufactured by Mitsubishi Chemical Corporation, "Ryoto Sugar Ester ER-290", HLB: 2, monoester content: about 2%) as an emulsifier were added. The mixture was emulsified by stirring at 5° C. and 7000 rpm for 5 minutes using a homomixer (manufactured by Primix Corporation, "MARK II 2.5 type”) to obtain a water-in-oil emulsion of cellulose.
  • sucrose erucate ester manufactured by Mitsubishi Chemical Corporation, "Ryoto Sugar Ester ER-290", HLB: 2, monoester content: about 2
  • the emulsion droplet size in the emulsion was 10 to 80 ⁇ m.
  • Step (III) The entire amount of the emulsion obtained in the step (II) was added to 1500 g of alcohol (ethanol) which is 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. Then, 42.8 g of acetic acid (1.5 equivalents relative to NaOH) was added to neutralize the mixture, and a suspension containing crude cellulose particles was obtained.
  • alcohol ethanol
  • acetic acid 1.5 equivalents relative to NaOH
  • Step (IV) The suspension obtained in the step (III) was filtered under reduced pressure (700 hPa) using filter paper (Millipore's "OMNIPORE DISC PTFE PHILIC 1.0 ⁇ M 90MM WH PLN 25/PK", mesh size 1 ⁇ m) to perform solid-liquid separation.
  • the recovered wet particles were added with acetone (300 parts by mass per 100 parts by mass of cellulose wet particles), stirred at room temperature for 1 hour, and then subjected to solid-liquid separation again. This operation was repeated twice.
  • water 300 parts by mass per 100 parts by mass of cellulose wet particles was added, stirred at room temperature for 1 hour, and then subjected to solid-liquid separation again. This operation was repeated twice.
  • the obtained suspension was subjected to solid-liquid separation again to recover the purified cellulose wet particles.
  • Example 4 The steps (I) to (IV) were carried out in the same manner as in Example 1, and then the following operations were carried out to produce porous cellulose particles, which were then evaluated.
  • the results are shown in Table 1.
  • Pentane 300 parts by mass relative to the cellulose wet particles
  • the mixture was stirred at 400 rpm for 1 hour at room temperature using a stirring blade, and then solid-liquid separation was performed again in the same manner as above. This operation was repeated twice.
  • the purified cellulose wet particles obtained were dried under reduced pressure overnight under a vacuum of 50 kPa or less to obtain purified dried porous cellulose particles.
  • the porous cellulose particles of this example have a good feel when applied to the skin, and are excellent in terms of the encapsulation of functional substances and the disintegration of the particles during application.
  • the cellulose particles of the comparative example were inferior in all of the above performances.
  • Figures 1 to 3 show the X-ray diffraction profiles of the raw cellulose (cellulose type I crystals) used in the examples, the porous cellulose particles obtained in Example 1 (cellulose type II crystals), and the porous cellulose particles (amorphous) obtained in Example 4, respectively.
  • the porous cellulose particles obtained in Example 1 can be attributed to cellulose type II crystals.
  • a broad peak is shown in Figure 3
  • the porous cellulose particles obtained in Example 4 can be attributed to amorphous cellulose.
  • porous cellulose particles which, when incorporated into cosmetics, can impart a soft feel, cause less of a squeaky feeling when applied, and have excellent capabilities for encapsulating functional substances and for disintegrating particles.

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