Low-substituted cellulose ether spherical fine particles, cosmetic composition using the same, and method for producing low-substituted cellulose spherical fine particles

Abstract

To provide low-substituted cellulose ether spherical fine particles capable of contributing to improvement of a sensory feel of a cosmetic composition to be used, regardless of use or nonuse of carbon disulfide.SOLUTION: The foregoing problem is solved by low-substituted cellulose ether spherical fine particles having a volume-based average particle diameter (D50) of 1 μm to 30 μm as measured by a dry laser diffraction method for primary particles, a sphericity of 0.75 to 1.0, and a surface smoothness of 75% to 100%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to spherical microparticles of low-substituted cellulose ether, a cosmetic composition using the spherical microparticles of low-substituted cellulose ether, and a method for producing the spherical microparticles of low-substituted cellulose ether. [Background technology]

[0002] Due to their particle properties, spherical microparticles are used in a variety of fields as formulations for matting agents, slip agents, antiblocking agents, etc. Spherical microparticles are also used in makeup cosmetics to improve properties such as spreadability. However, in recent years, due to environmental issues such as marine pollution by microplastics, the constituent materials of spherical microparticles incorporated into cosmetics are shifting from petroleum-derived synthetic materials to natural materials.

[0003] As for spherical microparticles made from natural materials, Japanese Patent Laid-Open No. 5-200286 (Patent Document 1) and Japanese Patent Laid-Open No. 11-181147 (Patent Document 2) disclose methods for producing spherical microparticles by coagulating and regenerating a viscose liquid made from natural cellulose as a raw material. Furthermore, Japanese Patent Laid-Open No. 2003-252902 (Patent Document 3) discloses a method for obtaining spherical microparticles by spray-drying a dispersion liquid made from a low-substituted cellulose ether. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-200286 [Patent Document 2] Japanese Patent Application Publication No. 11-181147 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-252902 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the methods described in Patent Documents 1 and 2 are undesirable from the viewpoint of environmental impact because carbon disulfide, which is a potential environmental pollutant, is used to produce the viscose liquid.

[0006] Furthermore, the method described in Patent Document 3 involves rapid evaporation of water in a low-substituted cellulose ether dispersion by spray drying, which leads to particle shrinkage, making it difficult to obtain spherical microparticles with high sphericity and surface smoothness. As a result, a cosmetic composition containing spherical microparticles obtained by the method described in Patent Document 3 has an insufficient feel to the touch and spreadability on the skin when applied to the skin, resulting in a poor feel in use.

[0007] In view of the above circumstances, an object of the present invention is to provide low-substituted cellulose ether spherical microparticles that can contribute to improving the usability of cosmetic compositions, regardless of whether carbon disulfide is used or not. [Means for solving the problem]

[0008] In the course of intensive research to solve the above problems, the present inventors have repeatedly conducted trial and error to find a method for obtaining spherical microparticles of low-substituted cellulose ether using raw materials with low environmental impact. As a result, the present inventors have obtained a W / O type emulsion of low-substituted cellulose ether composed of raw materials with low environmental impact, and have succeeded in obtaining spherical microparticles of low-substituted cellulose ether by subjecting the emulsion to a precipitation and coagulation treatment.

[0009] Surprisingly, the low-substituted cellulose ether spherical microparticles thus obtained had a small average primary particle size and high sphericity and surface smoothness. Due to these properties, a cosmetic composition obtained using the low-substituted cellulose ether spherical microparticles had excellent skin application properties, moisturizing properties, and a pleasant feel when used. Even more surprisingly, the pleasant feel of the cosmetic composition was obtained even when the amount of low-substituted cellulose ether spherical microparticles added was small.

[0010] As a result, the present inventors have finally succeeded in creating low-substituted cellulose ether spherical fine particles, etc., which solve the problems of the present invention and have primary particle average particle size, sphericity, and surface smoothness within predetermined ranges. The present invention has been completed based on the findings and successful examples first discovered by the present inventors.

[0011] Therefore, according to each aspect of the present invention, there are provided the following low-substituted cellulose ether spherical microparticles, cosmetic compositions using the same, and methods for producing low-substituted cellulose spherical microparticles. [1] Volume-based mean particle size (D 50 ) is 1 μm to 30 μm, the sphericity is 0.75 to 1.0, and the surface smoothness is 75% to 100%. [2] The spherical microparticles of low-substituted cellulose ether according to item [1], wherein the molar substitution number of the low-substituted cellulose ether is 0.05 to 1.0. [3] A cosmetic composition comprising the low-substituted cellulose ether spherical microparticles according to item [1] or [2] and an oil. [4] The cosmetic composition according to item [3], further comprising water. [5] A method for producing low-substituted cellulose ether spherical microparticles according to item [1] or [2], comprising: (1) a step of mixing an alkaline aqueous solution of a low-substituted cellulose ether as a raw material with a non-aqueous solvent in a volume ratio of 1:99 to 40:60 to obtain a W / O type low-substituted cellulose ether emulsion; (2) mixing raw materials, that is, an aqueous acid solution and a non-aqueous solvent, at a volume ratio of 1:99 to 40:60 to obtain a W / O type aqueous acid solution emulsion; (3) A step of mixing a W / O type low-substituted cellulose ether emulsion liquid with a W / O type acidic aqueous solution emulsion liquid to obtain the low-substituted cellulose ether spherical microparticles described in item [1] or [2]. The method comprising: [6] The method for producing low-substituted cellulose ether spherical microparticles according to item [5], wherein the raw material for step (1) further comprises a surfactant, and / or the raw material for step (2) further comprises a surfactant. [7] The method for producing low-substituted cellulose ether spherical microparticles according to item [5], wherein the non-water-soluble solvents are independently at least one non-water-soluble solvent selected from the group consisting of silicone oils and hydrocarbon solvents having 5 to 10 carbon atoms. [Effects of the Invention]

[0012] According to the present invention, by using low-substituted cellulose ether spherical microparticles having physical properties such as the average particle size of the primary particles, sphericity, and surface smoothness within predetermined ranges, it is possible to obtain a cosmetic composition having an excellent feel in use. In particular, the cosmetic composition using the spherical microparticles has excellent applicability to the skin and excellent moisturizing properties. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below, but the present invention can take various forms as long as it achieves its object.

[0014] Unless otherwise specified, each term in this specification is used in the meaning commonly used by those skilled in the art of cosmetics, chemistry, etc., and should not be construed as having an unduly restrictive meaning. Furthermore, the speculations and theories made in this specification are based on the inventors' knowledge and experience to date, and therefore the present invention is not limited solely to such speculations and theories.

[0015] The term "composition" is not particularly limited to the commonly used meaning, but may refer to, for example, a substance obtained by combining two or more components (raw materials). Each component may be a single component or a combination of two or more components. The term "and / or" means any one or any or all combinations of two or more of the associated listed items. "Content" is synonymous with concentration and amount used (added amount), and refers to the ratio of the amount of a component to the total amount of the composition. The total amount of the components does not exceed 100%. The use of "to" in a numerical range includes both the preceding and following numerical values, and also includes ranges excluding one of the included limits. For example, "0% to 100%" means 0% or more, 100% or less, or 0% or more and 100% or less. "More than" and "less than" refer to the lower and upper limits, respectively, without including the preceding numerical value. For example, "more than 1" means a number greater than 1, and "less than 100" means a number less than 100. "About" refers to an amount within ±10% of the quantity following the term. For example, "about 100" means 100±10%, i.e., 90 to 110. "Comprising" means that elements other than those explicitly stated as being included can be added (same meaning as "comprising at least"), but also encompasses "consisting of" and "consisting essentially of." That is, "comprising" can mean including the explicitly stated elements and any one or more elements, consisting of the explicitly stated elements, or consisting essentially of the explicitly stated elements. Elements include limitations such as ingredients, steps, conditions, and parameters. The number of digits in an integer value matches the number of significant digits. For example, 1 has one significant digit, and 10 has two significant digits. Also, the number of digits after the decimal point in a decimal value matches the number of significant digits. For example, 0.1 has one significant digit, and 0.10 has two significant digits.

[0016] The "feel" of a cosmetic composition refers to the fact that when the cosmetic composition is applied and spread on the skin, it does not feel sticky or otherwise uncomfortable to the skin. The "spreadability on skin" of a cosmetic composition means that when the cosmetic composition is applied and spread on the skin, it can be spread smoothly without applying a large amount of force. The "moisturizing property" of a cosmetic composition refers to the moisturizing feeling of the skin 5 minutes after the cosmetic composition is applied to the skin.

[0017] [Low-substituted cellulose ether spherical particles] One aspect of the present invention is spherical fine particles of a low-substituted cellulose ether. In one embodiment of the spherical fine particles of a low-substituted cellulose ether, the volume-based average particle diameter (D 50 ), sphericity and surface smoothness are characterized within a predetermined range.

[0018] Low-substituted cellulose ethers have the property of being insoluble in water but soluble in alkaline solutions. Generally, cellulose is insoluble in water. In contrast, cellulose ethers in which the hydrogen atoms of the hydroxyl groups on the glucose rings constituting cellulose are substituted with functional groups such as alkyl groups or hydroxyalkyl groups become water-soluble depending on the degree of substitution of the functional groups. However, low-substituted cellulose ethers with a low degree of substitution tend to be insoluble in water but soluble in alkaline solutions. Furthermore, low-substituted cellulose ethers can be regenerated from alkaline solutions by adding an acid to an alkaline solution of the low-substituted cellulose ether and neutralizing and coagulating it. Although such low-substituted cellulose ethers are insoluble in water, they have the property of absorbing water and swelling.

[0019] In summary, low-substituted cellulose ether has the following properties (1) to (4): (1) it is insoluble in water, (2) it absorbs water and swells, (3) it dissolves in an alkaline solution, and (4) it can be regenerated from the alkaline solution by neutralizing and coagulating it with an acid.

[0020] The low-substituted cellulose ether spherical particles according to one embodiment of the present invention have a volume-based average particle diameter (D 50 ) is 1 μm to 30 μm, the sphericity is 0.75 to 1.0, and the surface smoothness is 75% to 100%. In this specification, primary particles whose average particle size, sphericity, and surface smoothness are within the above ranges are called "spherical fine particles." In other words, primary particles whose average particle size, sphericity, and surface smoothness are not within the above ranges are not called spherical fine particles.

[0021] Examples of low-substituted cellulose ethers constituting the low-substituted cellulose ether spherical microparticles include low-substituted cellulose ethers such as low-substituted hydroxypropyl cellulose, low-substituted hydroxyethyl cellulose, low-substituted methyl cellulose, and low-substituted hydroxypropyl methyl cellulose. From the viewpoint of good alkali solubility and water absorption swelling properties, low-substituted hydroxypropyl cellulose is preferred.

[0022] The low-substituted cellulose ether spherical fine particles according to one embodiment of the present invention have an average particle size of primary particles, which is a volume-based average particle size (D 50 ) may be 1 μm to 30 μm, but from the viewpoint of excellent skin application and moisturizing properties when used in a cosmetic composition, it is preferably 1 μm to 25 μm, more preferably 1 μm to 22 μm, even more preferably 1 μm to 20 μm, and even more preferably 7 μm to 15 μm. The average particle size of the primary particles is measured as the volume-converted average particle size based on the diffraction intensity of a laser beam irradiated onto a powder sample ejected with compressed air, according to the method described in the section <Average particle size of primary particles> in the Examples below.

[0023] The low-substituted cellulose ether spherical microparticles of one embodiment of the present invention may have a sphericity of 0.75 to 1.00, but from the viewpoint of excellent application to the skin and moisturizing properties when used in a cosmetic composition, for example, the sphericity is preferably 0.78 to 1.00, more preferably 0.80 to 1.00, even more preferably 0.82 to 1.00, and still more preferably 0.85 to 1.00. The sphericity is measured by the method described in the section <Sphericity> in the Examples below.

[0024] The low-substituted cellulose ether spherical microparticles of one embodiment of the present invention may have a surface smoothness of 75% to 100%, but from the viewpoint of excellent skin application and moisturizing properties when used in a cosmetic composition, for example, the surface smoothness is preferably 78% to 100%, more preferably 80% to 100%, even more preferably 82% to 100%, and still more preferably 85% to 100%. The surface smoothness is measured by the method described in the section <Surface smoothness> in the Examples below.

[0025] The low-substituted cellulose ether spherical microparticles according to one embodiment of the present invention may have other physical properties in addition to the average particle size, sphericity, and surface smoothness of the primary particles, as long as the problem to be solved by the present invention is not hindered. The other physical properties are not particularly limited, and examples thereof include the aspect ratio, the content of the substituent, and the molar substitution number.

[0026] In relation to high sphericity, the low-substituted cellulose ether spherical microparticles according to one embodiment of the present invention preferably have an aspect ratio of 1.00 to 1.30, more preferably 1.00 to 1.20, and even more preferably 1.00 to 1.15. The aspect ratio is measured by the method described in the section <Aspect Ratio> in the Examples below.

[0027] In one embodiment of the present invention, the low-substituted cellulose ether spherical microparticles have a molar substitution number of preferably 0.05 to 1.0, more preferably 0.05 to 0.8, and even more preferably 0.1 to 0.6, 0.1 to 0.5, or 0.1 to 0.4, from the viewpoint of water insolubility and alkali solubility. The molar substitution number refers to the average total number of moles of hydroxyalkoxy groups and alkyl groups per mole of anhydroglucose. For example, the molar substitution number of low-substituted hydroxypropyl cellulose spherical microparticles can be determined by converting the value measured by the quantitative method described in the "Low-substituted Hydroxypropyl Cellulose" section of the Eighteenth Edition of the Japanese Pharmacopoeia. The molar substitution number of low-substituted cellulose ether spherical microparticles corresponds to the molar substitution number of the starting low-substituted cellulose ether.

[0028] [Method for producing spherical microparticles of low-substituted cellulose ether] The spherical cellulose ether microparticles of one embodiment of the present invention can be produced, for example, by mixing an alkaline aqueous solution of a low-substituted cellulose ether with a non-aqueous solvent in a volume ratio of 1:99 to 40:60 to obtain a water-in-oil (W / O) low-substituted cellulose ether emulsion, and by mixing an acidic aqueous solution with a non-aqueous solvent in a volume ratio of 1:99 to 40:60 to obtain a W / O acidic aqueous emulsion, and then mixing these two emulsions.

[0029] Another aspect of the present invention is a method for producing the cellulose ether spherical microparticles of one aspect of the present invention. The production method of one aspect of the present invention includes the following steps (1) to (3): (1) a step of mixing an alkaline aqueous solution of a low-substituted cellulose ether as a raw material with a non-aqueous solvent in a volume ratio of 1:99 to 40:60 to obtain a W / O type low-substituted cellulose ether emulsion; (2) mixing the raw materials, an aqueous acid solution and a non-aqueous solvent, in a volume ratio of 1:99 to 40:60 to obtain a W / O type aqueous acid solution emulsion; and (3) A step of mixing a W / O type low-substituted cellulose ether emulsion with a W / O type acidic aqueous solution emulsion to obtain spherical microparticles of a low-substituted cellulose ether according to one embodiment of the present invention.

[0030] In the production method of one aspect of the present invention, step (2) may be performed after step (1), step (1) may be performed after step (2), or step (1) and step (2) may be performed in parallel. Step (3) is performed after step (1) and step (2).

[0031] [Step (1): Preparation of W / O-type low-substituted cellulose ether emulsion] The main raw materials in step (1) are an aqueous alkaline solution of a low-substituted cellulose ether and a non-aqueous solvent.

[0032] The aqueous alkaline solution of the low-substituted cellulose ether can be obtained by uniformly dissolving the low-substituted cellulose ether in an aqueous alkaline solution.

[0033] Examples of the alkali in the alkaline aqueous solution include hydroxide salts such as sodium hydroxide, potassium hydroxide, and ammonium hydroxide, and organic amine bases such as monoethanolamine, aminomethylpropanol, aminomethylpropanediol, tromethamine, and tetrahydroxypropylethylenediamine. From the viewpoint of the solubility of the low-substituted cellulose ether, sodium hydroxide is preferred.

[0034] The alkali concentration of the alkaline aqueous solution is, for example, preferably 0.1% by mass to 30% by mass, more preferably 0.3% by mass to 25% by mass, even more preferably 0.5% by mass to 20% by mass, and still more preferably 1% by mass to 15% by mass, from the viewpoint of the solubility of the low-substituted cellulose ether.

[0035] The content of the low-substituted cellulose ether in the alkaline aqueous solution of the low-substituted cellulose ether is, for example, preferably 0.1% by mass to 20% by mass, more preferably 0.5% by mass to 17% by mass, even more preferably 1% by mass to 15% by mass, and still more preferably 1% by mass to 10% by mass or 3% by mass to 7% by mass, from the viewpoint of the viscosity of the alkaline aqueous solution.

[0036] The non-water-soluble solvent may be any oily solvent that has very low or substantially no compatibility with water, and examples thereof include silicone oil and hydrocarbon solvents having 5 to 10 carbon atoms.

[0037] Examples of silicone oils include linear or branched organopolysiloxanes with low to high viscosity, such as dimethylpolysiloxane, tristrimethylsiloxymethylsilane, caprylyl methicone, phenyl trimethicone, tetrakistrimethylsiloxysilane, methylphenylpolysiloxane, methylhexylpolysiloxane, methylhydrogenpolysiloxane, and dimethylsiloxane-methylphenylsiloxane copolymer; octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclopentasiloxane; Examples of the organic organopolysiloxane include cyclic organopolysiloxanes such as tetramethyltetrahydrogencyclotetrasiloxane, tetramethyltetraphenylcyclotetrasiloxane, and the like; higher alkoxy-modified silicones such as amino-modified organopolysiloxanes, pyrrolidone-modified organopolysiloxanes, pyrrolidonecarboxylic acid-modified organopolysiloxanes, and stearoxysilicone; higher fatty acid-modified silicones, alkyl-modified silicones, long-chain alkyl-modified silicones, amino acid-modified silicones, and fluorine-modified silicones.

[0038] Examples of hydrocarbon solvents having 5 to 10 carbon atoms include pentane, isopentane, neopentane, hexane, cyclohexane, isohexane, heptane, octane, nonane, and decane.

[0039] The alkaline aqueous solution of the low-substituted cellulose ether and the non-aqueous solvent are mixed in a ratio that allows the formation of a W / O type emulsion. The volume ratio of these ([aqueous alkaline solution of the low-substituted cellulose ether]:[non-aqueous solvent]) is, for example, preferably 1:99 to 40:60, more preferably 3:97 to 38:62, even more preferably 5:95 to 36:64, and still more preferably 10:90 to 35:65, from the viewpoint of the ability to form a fine emulsion.

[0040] In step (1), it is preferable to use a surfactant as another raw material for the purpose of stabilizing the emulsion.

[0041] The surfactant is not particularly limited as long as it is a surfactant that is normally used as a component of cosmetic compositions, and examples thereof include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0042] Examples of nonionic surfactants include polyether-modified silicones, polyglycerin-modified silicones, acrylic silicone types, sorbitan fatty acid esters such as polyoxyethylene sorbitan monostearate, sorbitan oleate, and sorbitan sesquiisostearate, and hydrogenated castor oil derivatives.

[0043] Examples of anionic surfactants include fatty acid salts such as sodium laurate, higher alkyl sulfate salts such as sodium lauryl sulfate, alkyl ether sulfate salts such as POE lauryl sulfate triethanolamine, N-acyl sarcosine salts, sulfosuccinate salts, and N-acyl amino acid salts.

[0044] Examples of cationic surfactants include alkyltrimethylammonium salts such as stearyltrimethylammonium chloride, benzalkonium chloride, and benzethonium chloride.

[0045] Examples of amphoteric surfactants include betaine surfactants such as alkylbetaine and amidobetaine.

[0046] From the viewpoint of emulsion stabilization, the amount of surfactant used is, for example, preferably 0.01 vol% to 10 vol%, more preferably 0.01 vol% to 9 vol%, even more preferably 0.01 vol% to 8 vol%, and still more preferably 0.05 vol% to 0.5 vol%, as an external addition amount relative to the total amount of the alkaline aqueous solution of the low-substituted cellulose ether and the water-insoluble solvent used.

[0047] The raw materials are preferably mixed by stirring. Stirring may be performed manually or mechanically, but mechanical stirring using a stirring mixer is preferred in order to form a stable emulsion.

[0048] Examples of stirring and mixing devices include homomixers (e.g., "Homomixer MARK II 2.5 type", manufactured by Primix Corporation), homodispers (e.g., "Homodisper 2.5 type", manufactured by Primix Corporation), homogenizers (e.g., "Ace Homogenizer", manufactured by Nippon Seiki Seisakusho Co., Ltd.), Ajihomomomixers (e.g., "2M-03 type", manufactured by Primix Corporation), multi-axis dispersion kneaders (e.g., "Combimix", manufactured by Primix Corporation), and colloid mills (e.g., "Colloid Mill MM-2", manufactured by Nippon Seiki Seisakusho Co., Ltd.).

[0049] The stirring using a stirring mixer may be carried out under conditions that allow a W / O type low-substituted cellulose ether emulsion to be obtained. For example, when a homomixer is used, from the viewpoint of forming a fine emulsion, the rotor rotation speed during mixing is preferably 1,000 rpm to 10,000 rpm, more preferably 5,000 rpm to 10,000 rpm; and the mixing time is preferably 3 minutes to 60 minutes, more preferably 10 minutes to 30 minutes.

[0050] In step (1), other raw materials may be used in addition to the aqueous alkali solution of the low-substituted cellulose ether, the non-aqueous solvent, and the surfactant. However, it is preferable not to use environmental pollutants as the other raw materials, and it is more preferable not to use carbon disulfide.

[0051] [Step (2): Preparation of W / O-type aqueous acid emulsion] The main raw materials in step (2) are an aqueous acid solution and a non-aqueous solvent.

[0052] Examples of the acid in the aqueous acid solution include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as citric acid, oxalic acid and malic acid, with hydrochloric acid being preferred.

[0053] The acid concentration in the aqueous acid solution is preferably 1% by mass to 50% by mass, more preferably 3% by mass to 30% by mass, and even more preferably 5% by mass to 20% by mass, for example, to stably coagulate and precipitate spherical microparticles of low-substituted cellulose ether by mixing a W / O type emulsion of an alkaline aqueous solution of low-substituted cellulose ether with a W / O type emulsion of an aqueous acid solution.

[0054] From the viewpoint of promoting the formation of spherical microparticles of low-substituted cellulose ether, it is preferable that the salt concentration of the aqueous acid solution is set to fall within a predetermined range. For example, when hydrochloric acid is used as the acid, it is preferable that sodium chloride is added to the aqueous acid solution. In this case, it is preferable that sodium chloride is added to the aqueous acid solution so that the final concentration is preferably 1% by mass to 20% by mass, more preferably 5% by mass to 15% by mass.

[0055] The non-aqueous solvent can be the same as that used in step (1), but it is preferable that the non-aqueous solvent be the same as that used in step (1) in order to stably form spherical microparticles of low-substituted cellulose ether.

[0056] The aqueous acid solution and the non-aqueous solvent are mixed in a ratio that will form a W / O emulsion. The volume ratio ([aqueous acid solution]:[non-aqueous solvent]) is, for example, preferably 1:99 to 40:60, more preferably 3:97 to 38:62, even more preferably 5:95 to 36:64, and even more preferably 10:90 to 35:65, from the viewpoint of forming a fine emulsion.

[0057] In step (2), similarly to step (1), a surfactant is preferably used as another raw material for the purpose of stabilizing the emulsion. The surfactant can refer to the surfactant described in step (1). The surfactant may be the same as or different from that used in step (1), but it is preferably the same surfactant in order to stably form low-substituted cellulose ether spherical microparticles.

[0058] From the viewpoint of stabilizing the emulsion, the amount of surfactant used is, for example, preferably 0.01 vol% to 10 vol%, more preferably 0.01 vol% to 9 vol%, even more preferably 0.01 vol% to 8 vol%, and still more preferably 0.05 vol% to 0.5 vol%, as an external addition amount relative to the total amount of the aqueous acid solution and the non-aqueous solvent used.

[0059] The raw materials are preferably mixed by stirring. Stirring may be manual or mechanical, but mechanical stirring using a stirring mixer is preferred to form a stable emulsion. The type and use conditions of the stirring mixer can be found in the type and use conditions of the stirring mixer described in step (1).

[0060] In step (2), other raw materials may be used in addition to the aqueous acid solution, the non-aqueous solvent, and the surfactant. However, it is preferable not to use environmental pollutants as other raw materials, and it is more preferable not to use carbon disulfide.

[0061] [Step (3): Step of forming spherical microparticles of low-substituted cellulose ether] The main raw materials in step (3) are the W / O type low-substituted cellulose ether emulsion liquid, which is the product of step (1), and the W / O type acidic aqueous solution emulsion liquid, which is the product of step (2).

[0062] The W / O type low-substituted cellulose ether emulsion and the W / O type acidic aqueous solution emulsion are mixed at a ratio that allows the formation of spherical microparticles of the low-substituted cellulose ether. The volume ratio of these mixtures ([W / O type low-substituted cellulose ether emulsion]:[W / O type acidic aqueous solution emulsion]) is, for example, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40, from the viewpoint of the formation of fine spherical particles.

[0063] The W / O type low-substituted cellulose ether emulsion and the W / O type acidic aqueous solution emulsion are mixed so as to form spherical microparticles of the low-substituted cellulose ether. From the viewpoint of obtaining fine spherical particles, the W / O type low-substituted cellulose ether emulsion and the W / O type acidic aqueous solution emulsion are preferably mixed by gradually adding the W / O type low-substituted cellulose ether emulsion to the W / O type acidic aqueous solution emulsion while mechanically stirring the W / O type acidic aqueous solution emulsion using a stirring mixer.

[0064] For the stirring and mixing device, the stirring and mixing device described in step (1) can be referred to.

[0065] The stirring using a stirring mixer may be carried out under conditions that allow for the production of spherical microparticles of low-substituted cellulose ether. For example, when a homomixer is used, the rotor rotation speed during mixing is preferably 1,000 rpm to 10,000 rpm, more preferably 2,000 rpm to 4,000 rpm, from the viewpoint of obtaining fine spherical particles.

[0066] The time for adding the W / O type low-substituted cellulose ether emulsion to the W / O type acidic aqueous solution emulsion is, for example, preferably 3 minutes to 60 minutes, more preferably 10 minutes to 30 minutes, from the viewpoint of the formation of fine spherical particles.

[0067] In step (3), it is preferable to add the W / O type low-substituted cellulose ether emulsion to the W / O type acidic aqueous emulsion, and then further stir the resulting mixture. The stirring conditions for the mixture of the W / O type acidic aqueous emulsion and the W / O type low-substituted cellulose ether emulsion may be any conditions that allow sufficient coagulation and precipitation of low-substituted cellulose ether spherical microparticles. For example, when using the above-mentioned stirring mixer or other equipment such as a magnetic stirrer, the rotation speed is preferably 500 to 3,000 rpm, and the stirring time is preferably 30 minutes to 5 hours, more preferably 2 to 5 hours.

[0068] The coagulated and precipitated spherical microparticles of low-substituted cellulose ether can be recovered, for example, by subjecting them to solid-liquid separation treatment such as filtration, etc. The recovered spherical microparticles of low-substituted cellulose ether may be subjected to other processing treatments such as drying, as appropriate.

[0069] [Cosmetic composition] Another aspect of the present invention is a cosmetic composition. The cosmetic composition of one aspect of the present invention is characterized by comprising, as constituent components, the low-substituted cellulose ether spherical microparticles of one aspect of the present invention and an oily agent.

[0070] The cosmetic composition of one embodiment of the present invention contains the low-substituted cellulose ether spherical microparticles of one embodiment of the present invention, and therefore has excellent texture, spreadability on the skin, and moisturizing properties, and can have an overall excellent feel when used.

[0071] The content of the low-substituted cellulose ether spherical microparticles is not particularly limited, but from the viewpoint of the ease of application of the cosmetic composition to the skin, it is preferably 0.01% by mass to 20% by mass, more preferably 0.1% by mass to 15% by mass, even more preferably 0.5% by mass to 10% by mass, and even more preferably 1% by mass to 7% by mass relative to the total amount of the cosmetic composition.

[0072] The oil may be any oil that is generally used in producing cosmetic compositions, and examples thereof include hydrocarbon oils, ester oils, animal and vegetable oils, and silicone oils.

[0073] Examples of hydrocarbon oils include liquid paraffin, stearic acid, hydrogenated polyisobutene, hydrogenated polydecene, squalane, squalene, pristane, light isoparaffin, light liquid isoparaffin, heavy liquid isoparaffin, liquid isoparaffin, tetradecene, isohexadecane, isododecane, and α-olefin oligomers.

[0074] Examples of ester oils include glyceryl stearate, ethyl oleate, ethyl linoleate, isopropyl myristate, isopropyl palmitate, isopropyl isostearate, cetyl 2-ethylhexanoate, isocetyl 2-ethylhexanoate, stearyl 2-ethylhexanoate, isostearyl 2-ethylhexanoate, cetyl palmitate, 2-ethylhexyl palmitate, 2-hexyldecyl isostearate, isostearyl isostearate, trimethylolpropane triisostearate, myristyl myristate, cetyl myristate, octyldodecyl myristate, isostearyl myristate, isocetyl myristate, hexyl laurate, decyl oleate, octyldodecyl oleate, isostearyl pivalate, isopropyl isostearate, isononyl isononanoate, and 2-ethyl isononanoate. Hexyl, isodecyl isononanoate, isotridecyl isononanoate, octyldodecyl erucate, neopentyl glycol didecanoate, pentaerythrityl tetraethylhexanoate, diisostearyl malate, trimethylolpropane triethylhexanoate, didecyl adipate, cholesteryl isostearate, batyl isostearate, hydrogenated castor oil monohydroxystearate, isostearyl lanolinate, isopropyl lanolinate, octyldodecyl lanolinate, cetyl ricinoleate, dioctyl succinate, cetyl lactate, propylene glycol dicaprylate, propylene glycol dicaprate, propylene glycol dinonanoate, propylene glycol dicaprylate-caprate, propylene glycol diisostearate, propylene glycol dioleate, triglycerides, animal and vegetable oils, etc. Examples of triglycerides include glycerin and triglycerides of caproic acid, caprylic acid, capric acid, 2-ethylhexanoic acid, isotridecanoic acid, isopalmitic acid, isostearic acid, eicosanoic acid, and oleic acid.

[0075] Examples of animal and vegetable oils include liquid lanolin, olive oil, sunflower oil, safflower oil, castor oil, and camellia oil.

[0076] Examples of silicone oils include low-viscosity to high-viscosity linear or branched organopolysiloxanes such as dimethylpolysiloxane, tristrimethylsiloxymethylsilane, caprylyl methicone, phenyl trimethicone, tetraquistrimethylsiloxysilane, methylphenylpolysiloxane, methylhexylpolysiloxane, methylhydrogenpolysiloxane, and dimethylsiloxane-methylphenylsiloxane copolymers, as well as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclopentasiloxane. Examples of the organic solvent include cyclic organopolysiloxanes such as hexasiloxane, tetramethyltetrahydrogencyclotetrasiloxane, and tetramethyltetraphenylcyclotetrasiloxane; amino-modified organopolysiloxanes; pyrrolidone-modified organopolysiloxanes; pyrrolidonecarboxylic acid-modified organopolysiloxanes; higher alkoxy-modified silicones such as stearoxysilicone; higher fatty acid-modified silicones; alkyl-modified silicones; long-chain alkyl-modified silicones; amino acid-modified silicones; and fluorine-modified silicones.

[0077] The content of the oil is not particularly limited, but from the viewpoint of the moisturizing properties of the cosmetic composition, for example, it is preferably 0.1% by mass to 50% by mass, more preferably 0.3% by mass to 45% by mass, even more preferably 0.5% by mass to 40% by mass, and even more preferably 1% by mass to 35% by mass relative to the total amount of the cosmetic composition.

[0078] The cosmetic composition of the present invention may further contain water.

[0079] The water is not particularly limited as long as it is water that is normally used in the production of cosmetic compositions, and examples thereof include tap water and purified water, but purified water is preferred from the viewpoint of not containing impurities.

[0080] The water content is not particularly limited as long as it is the amount typically used in cosmetic compositions, depending on the formulation of the cosmetic composition. For example, from the viewpoint of the ease of application of the cosmetic composition to the skin, the water content is preferably 90% by mass or less, more preferably 85% by mass or less, even more preferably 80% by mass or less, and even more preferably 75% by mass or less, relative to the total amount of the cosmetic composition. The lower limit of the water content is typically 0% by mass. Taking these factors into consideration, the water content is preferably 0% by mass to 90% by mass, more preferably 10% by mass to 85% by mass, 20% by mass to 80% by mass, and even more preferably 30% by mass to 75% by mass.

[0081] In order to provide the cosmetic composition with desired properties, it may further contain other components in addition to the low-substituted cellulose ether spherical particles, oil, and water. Examples of other components include additives such as solvents, surfactants, pH adjusters, clay minerals, colorants, thickeners, antioxidants, preservatives, moisturizers, pearlizing agents, astringents, whitening agents, and fragrances. Specific examples of each additive are listed below.

[0082] Specific examples of the solvent include polyhydric alcohols such as glycerin, diglycerin, butylene glycol, propylene glycol, and dipropylene glycol, and alcohols such as ethanol.

[0083] The surfactant is not particularly limited as long as it is a surfactant that is normally used as a component of cosmetic compositions, and for example, the surfactants described in step (1) can be referred to.

[0084] Specific examples of pH adjusters include ethanolamine, diethanolamine, triethanolamine, citric acid, sodium citrate, gluconic acid, succinic acid, sodium hydroxide, and potassium hydroxide.

[0085] Specific examples of clay minerals include talc, mica, sericite, kaolin, montmorillonite, saponite, hectorite, and smectite.

[0086] Specific examples of colorants include inorganic brown pigments such as red iron oxide, yellow iron oxide, black iron oxide, titanium oxide, ultramarine, ferric iron oxide, manganese violet, cobalt violet, chromium hydroxide, chromium oxide, cobalt oxide, cobalt titanate, iron oxide-doped titanium oxide, iron titanate, (titanium / titanium oxide) baked product, (Li / cobalt) titanate, cobalt titanate, titanium nitride, iron hydroxide, γ-iron oxide, inorganic yellow pigments such as yellow ochre, and colored pigments such as lakes of tar-based pigments and lakes of natural pigments. The shape of the pigment may be any shape, such as spherical, approximately spherical, rod-shaped, spindle-shaped, petal-shaped, strip-shaped, or irregular, and there is no particular limitation on its geometric form as long as it is capable of imparting color to the formulation.

[0087] Specific examples of thickeners include water-soluble polymers such as xanthan gum, guar gum, gellan gum, locust bean gum, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, hydrophobized hydroxypropyl methyl cellulose, methyl cellulose, cationized hydroxyethyl cellulose, carboxyvinyl polymer, and polyvinyl alcohol.

[0088] Specific examples of antioxidants include tocopherol, tocopherol acetate, butylhydroxyanisole, and dibutylhydroxytoluene.

[0089] Specific examples of preservatives include methylparaben, ethylparaben, propylparaben, butylparaben, and phenoxyethanol.

[0090] Specific examples of moisturizing agents include propylene glycol, hyaluronic acid, sodium hyaluronate, polyethylene glycol, mucopolysaccharides, urea, sorbitol, chondroitin sulfate, pyrrolidonecarboxylic acid, sodium lactate, and polyaspartic acid.

[0091] Specific examples of pearlizing agents include ethylene glycol monostearate, ethylene glycol monobehenate, ethylene glycol distearate, and ethylene glycol dibehenate.

[0092] Specific examples of astringents include zinc oxide, zinc paraphenolsulfonate, aluminum hydroxychloride, allantoin dihydroxyaluminum, peppermint extract, aloe extract, witch hazel extract, rosemary extract, lavender extract, and eucalyptus extract.

[0093] Specific examples of whitening agents include arbutin, α-arbutin, ascorbic acid, ascorbic acid fatty acid esters such as sodium ascorbyl phosphate, magnesium ascorbyl phosphate, and ascorbyl tetraisopalmitate, kojic acid, ellagic acid, tranexamic acid, and derivatives thereof.

[0094] Specific examples of the fragrance include natural fragrances and synthetic fragrances.

[0095] Specific examples of natural fragrances include rose oil, jasmine oil, lavender oil, ylang-ylang oil, peppermint oil, geranium oil, patchouli oil, sandalwood oil, cinnamon oil, lemon oil, orange oil, and bergamot oil.

[0096] Specific examples of synthetic fragrances include limonene, β-caryophyllene, cis-3-hexenol, linalool, farnesol, β-phenylethyl alcohol, 2,6-nonadienal, citral, α-hexyl cinnamic aldehyde, ι-carvone, cyclopentadecanone, linalyl acetate, γ-undecalactone, aurantiol, and l-menthol.

[0097] The content of the additive is not particularly limited, but from the viewpoint of the feel on the skin, spreadability on the skin, and moisturizing properties imparted to the cosmetic composition, it is preferably 0.1% by mass to 95% by mass, more preferably 0.5% by mass to 50% by mass, and even more preferably 10% by mass to 40% by mass.

[0098] The method for producing the cosmetic composition is not particularly limited. The cosmetic composition can be obtained, for example, by adding a water-soluble component to water and mixing to obtain an aqueous solution, then adding a solid component containing low-substituted cellulose ether spherical microparticles to the obtained aqueous solution and mixing to obtain a mixture, then adding an oil to the obtained mixture and mixing, and then subjecting the obtained mixture to additional processing such as drying, as necessary.

[0099] The cosmetic composition of one embodiment of the present invention is not particularly limited in its mode of use or formulation, and can be used, for example, in makeup cosmetics, skin care cosmetics, fragrance cosmetics, and body care cosmetics, specifically creams, emulsions, foundations, lotions, serums, sunscreen milks, masks, facial cleansers, hand creams, makeup cleansers, makeup bases, concealers, blushers, eye shadows, eyeliners, eyebrow creams, lipsticks, sunscreen creams, hair removal creams, and all-in-one cosmetics. Furthermore, the cosmetic composition of one embodiment of the present invention can be impregnated into sheets or sprayed. Therefore, the cosmetic composition of one embodiment of the present invention is expected to be in the form of an impregnated sheet, an impregnated mask, or a spray using a pump or the like. [Example]

[0100] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, all operations were carried out at 25°C.

[0101] The low-substituted cellulose ether (CE), which is granular low-substituted hydroxypropyl cellulose used in the examples and comparative examples, is shown in Table 1.

[0102]

Table 1

[0103] The number of moles of substitution of the low-degree substitution cellulose ether was determined by converting the value measured by the quantification method of the item "low-degree substitution hydroxypropyl cellulose" described in the 18th revised Japanese Pharmacopoeia.

[0104] The average particle diameter and aspect ratio of the low-degree substitution cellulose ether were measured by the methods described in the items <average particle diameter of primary particles> and <aspect ratio> described below.

[0105] [Example 1] <Preparation of an alkaline aqueous solution of low-degree substitution cellulose ether> 190 g of a 5% by mass aqueous sodium hydroxide solution was added to a 500 ml beaker and cooled in a water bath until it reached 5°C. Then, while stirring the 5% by mass aqueous sodium hydroxide solution, 10 g of CE-1 as a low-degree substitution cellulose ether was added thereto, and stirring was carried out until CE-1 was uniformly dissolved to prepare an alkaline aqueous solution of a low-degree substitution cellulose ether having a CE-1 content of 5% by mass.

[0106] <Preparation of a W / O type low-degree substitution cellulose ether emulsion liquid> 90 ml of silicone oil KF-96L-1.5cs (manufactured by Shin-Etsu Chemical Co., Ltd.), 10 ml of an alkaline aqueous solution of a low-degree substitution cellulose ether having a CE-1 content of 5% by mass, and 0.1 ml of polyether-modified silicone KF-6017 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a surfactant were added to a 500 ml beaker. Then, these raw materials were stirred at 8,000 rpm for 15 minutes using a homomixer ("Homomixer MARKII2.5 type", manufactured by Primix Co., Ltd., rotor diameter 30.0 mm) to prepare a W / O type low-degree substitution cellulose ether emulsion liquid.

[0107] <W / O type acidic aqueous solution emulsion liquid>​A 500 ml beaker was charged with 90 ml of silicone oil KF-96L-1.5cs (Shin-Etsu Chemical Co., Ltd.), 10 ml of a 10% by mass aqueous solution of hydrochloric acid in which sodium chloride was dissolved to a final concentration of 10% by mass, and 0.1 ml of a surfactant, polyether-modified silicone KF-6017 (Shin-Etsu Chemical Co., Ltd.). These raw materials were then stirred at 8,000 rpm for 15 minutes using a homomixer ("Homomixer MARK II 2.5 Type," Primix Corporation, rotor diameter 30.0 mm) to prepare a W / O type acidic aqueous emulsion.

[0108] <Formation of low-substituted cellulose ether spherical particles> While stirring 100 ml of the W / O type acidic aqueous emulsion using a homomixer ("Homomixer MARK II 2.5 type," manufactured by Primix Corporation, rotor diameter 30.0 mm) at 3,000 rpm, 100 ml of the W / O type low-substituted cellulose ether emulsion was added thereto over 15 minutes. The resulting mixture was then stirred using a magnetic stirrer at 2,000 rpm for 3 hours to precipitate spherical microparticles of the low-substituted cellulose ether.

[0109] The resulting suspension containing the low-substituted cellulose ether spherical particles was placed in a 300 ml separatory funnel, and after standing, the lower aqueous layer containing the low-substituted cellulose ether spherical particles was collected. The resulting aqueous layer was filtered using a Kiriyama funnel equipped with No. 5A filter paper, and the filtrate was washed with water and ethanol. The ethanol was then air-dried to obtain low-substituted cellulose ether spherical particles (MB-1).

[0110] [Examples 2 to 5] Low-substituted cellulose ether spherical particles (MB-2 to 5) were prepared in the same manner as in Example 1, except that the low-substituted cellulose ether used was changed from CE-1 to CE-2 to CE-5, respectively.

[0111] [Example 6] In the preparation of the W / O type low-substituted cellulose ether emulsion, the amount of the alkaline aqueous solution of low-substituted cellulose ether was changed to 20 ml, and the amount of silicone oil KF-96L-1.5cs was changed to 80 ml; and in the preparation of the W / O type acidic aqueous solution emulsion, the amount of 10 mass% hydrochloric acid aqueous solution (dissolving 10 mass% sodium chloride) was changed to 20 ml, and the amount of silicone oil KF-96L-1.5cs was changed to 80 ml. Except for this, the same procedure as in Example 1 was carried out to prepare low-substituted cellulose ether spherical microparticles (MB-6).

[0112] [Example 7] In the preparation of W / O type low-substituted cellulose ether emulsion, the amount of alkaline aqueous solution of low-substituted cellulose ether is changed to 35ml, and the amount of silicone oil KF-96L-1.5cs is changed to 65ml; in the preparation of W / O type acidic aqueous solution emulsion, the amount of 10 mass% hydrochloric acid aqueous solution (dissolved 10 mass% sodium chloride) is changed to 35ml, and the amount of silicone oil KF-96L-1.5cs is changed to 65ml. Except for this, low-substituted cellulose ether spherical microparticles (MB-7) were prepared in the same manner as in Example 1.

[0113] [Comparative Example 1] In the preparation of W / O type low-substituted cellulose ether emulsion, the amount of alkaline aqueous solution of low-substituted cellulose ether is changed to 45ml, and the amount of silicone oil KF-96L-1.5cs is changed to 55ml; in the preparation of W / O type acidic aqueous solution emulsion, the amount of 10 mass% hydrochloric acid aqueous solution (dissolved 10 mass% sodium chloride) is changed to 45ml, and the amount of silicone oil KF-96L-1.5cs is changed to 55ml. Except for this, low-substituted cellulose ether spherical microparticles (MB-8) were prepared in the same manner as in Example 1.

[0114] Comparative Example 2 7.5 g of CE-1 was dissolved in 425 g of 6.3% by weight sodium hydroxide aqueous solution. The resulting solution was neutralized by adding 40.2 g of acetic acid dropwise through a small hole in the container over 5 minutes while shearing and grinding at 5,000 rpm using an Ace Homogenizer (Nihon Seiki Seisakusho Co., Ltd.). The neutralized solution was further subjected to shear and grinding at 10,000 rpm for 10 minutes. The resulting gel was centrifuged at 10,000 rpm for 10 minutes at 25°C using a refrigerated centrifuge (Himac CR22N, Eppendorf-Himac Technologies). After centrifugation, the supernatant was discarded and the resulting precipitate was redispersed in pure water to a solids concentration of 2% by weight. The resulting dispersion was spray-dried using a rotary atomizer ("Mobile Minor Closed Cycle" manufactured by GEA Niro) to prepare low-substituted cellulose ether spherical particles (MB-9). The operating conditions were: atomizer rotation speed 28,000 rpm, drying chamber inlet temperature 120°C, drying chamber outlet temperature 60°C, and intake air flow rate 100 kg / h.

[0115] Table 2 shows the compositions of the W / O type low-substituted cellulose ether emulsions and W / O type acidic aqueous solution emulsions prepared in the Examples and Comparative Examples.

[0116] [Table 2]

[0117] [Physical property measurements of low-substituted cellulose ether spherical particles] The average particle size, sphericity, surface smoothness, and aspect ratio of the primary particles were measured for the obtained low-substituted cellulose ether spherical microparticles and commercially available spherical microparticles (MB-10) made from cellulose. The results are shown in Table 3.

[0118] <Average particle size of primary particles> The average particle size of the primary particles of spherical microparticles is the volume-based average particle size (D 50) A laser diffraction particle size distribution analyzer (Mastersizer 3000, manufactured by Malvern) was used to measure the diameter corresponding to the 50% cumulative value of the volume-based cumulative particle size distribution curve according to the Fraunhofer diffraction theory using a dry method under conditions of a dispersion pressure of 1.5 bar and a scattering intensity of 2% to 10%.

[0119] <Sphericity> The sphericity of spherical particles was calculated by observing an image of the spherical particles taken with a scanning electron microscope (2,000x magnification) and dividing the equivalent circular perimeter (the perimeter of a circle with the same projected area as the particle image) by the perimeter (the perimeter of the particle's projected image). At least 30 particles were measured at a time, and this was repeated at least 10 times to determine the average sphericity of a total of 300 or more spherical particles.

[0120] <Surface smoothness> The surface smoothness of the spherical fine particles was calculated by observing an image of the spherical fine particles taken with a scanning electron microscope (2,000x magnification) and using the following formula. Surface smoothness = (1-(S1) / (S2))×100

[0121] In the above formula, S2 represents the area (projected area) of the spherical particle in the image, and S1 represents the sum of "the area outside the outline of the circle having the same projected area as S2 and inside the outline of the spherical particle in the image" and "the area inside the outline of the circle having the same projected area as S2 and outside the outline of the spherical particle in the image" when the spherical particle in the image is superimposed on a circle having the same projected area as S2.

[0122] The spherical particle in the image was superimposed on a circle having the same projected area as S2 in the following manner: When the spherical particle in the image was superimposed on the circle having the same projected area as S2, the two images were superimposed so that the area of ​​the overlapping region (the area inside the outline of the circle having the same projected area as S2 and the area inside the outline of the spherical particle in the image) was maximized.

[0123] The number of particles measured at one time was 30 or more, and this was repeated 10 or more times to calculate the average surface smoothness of a total of 300 or more particles.

[0124] <Aspect ratio> The aspect ratio of the low-substituted cellulose ether spherical microparticles was measured by taking photographs of 50 randomly selected particles at a measurable magnification using a scanning electron microscope ("JSM-6010LA", manufactured by JEOL Ltd.) and measuring the long diameter (L) and short diameter (D) of each particle. The aspect ratio (L / D) was calculated from the obtained values, and the average value (average aspect ratio) was calculated from the calculated aspect ratio values ​​(n=50).

[0125] [Table 3]

[0126] As shown in Table 3, MB-1 to MB-7 in Examples 1 to 7 had a volume-based average particle diameter (D 50 The low-substituted cellulose ether spherical microparticles had a diameter of 1 μm to 30 μm, a sphericity of 0.75 to 1.0, and a surface smoothness of 75% to 100%. When the production method is emulsion coagulation and precipitation, fine water droplets are generated in the oil by applying mechanical shear to the emulsion. For MB-8 in Comparative Example 1, the amount of water was high relative to the oil, so it is presumed that the generated fine droplets coalesced to form larger droplets and that the particles could not be crushed into fine droplets, resulting in a large average particle size of the primary particles. Furthermore, when the production method is spray drying, it was found that only particles with low sphericity and surface smoothness were obtained, as in MB-9 in Comparative Example 2.

[0127] [Examples 8 to 16, Comparative Examples 3 and 4, and Reference Example 1] <Preparation of Cosmetic Composition> Cosmetic compositions simulating liquid foundations of Examples 8 to 16, Comparative Examples 3 and 4, and Reference Example 1 were prepared using the spherical microparticles MB-1 to MB-10 according to the formulations shown in Table 4 and the methods described below. MB-10 used spherical microparticles made from cellulose as a raw material.

[0128] A mixture of purified water, propylene glycol, polyoxyethylene sorbitan monostearate, and triethanolamine was stirred for 5 minutes using an Ace Homogenizer (manufactured by Nippon Seiki Seisakusho Co., Ltd.). Low-substituted cellulose ether spherical microparticles, talc, titanium oxide, red iron oxide, yellow iron oxide, and black iron oxide were added to the resulting treatment liquid, and the mixture was stirred for 5 minutes using the Ace Homogenizer at 5,000 rpm at 70°C. An oil solution prepared by heating and dissolving stearic acid, glyceryl stearate, liquid lanolin, and liquid paraffin at 70°C was added to the resulting treatment liquid. The resulting mixture was stirred for 5 minutes using the Ace Homogenizer at 5,000 rpm at 70°C to obtain a liquid cosmetic composition.

[0129] [Table 4]

[0130] <Sensory evaluation of cosmetic compositions> The resulting cosmetic compositions were subjected to a sensory evaluation of skin feel, spreadability, and moisturizing properties by five panelists who excel in evaluating the feel of cosmetics. Each was scored out of 5 according to the following evaluation criteria, and the average of the five panelists' scores was calculated. Furthermore, a score of 3.0 or higher for all of skin feel, spreadability, and moisturizing properties was evaluated as "+," and a score of less than 3.0 for any of these was evaluated as "-." The results are shown in Table 5. 5: Very good 4: Good 3: Normal 2: Bad 1: Very bad

[0131] [Table 5]

[0132] As shown in Table 5, the cosmetic compositions prepared using low-substituted cellulose ether spherical microparticles having an average primary particle size, sphericity, and surface smoothness within the specific ranges were excellent in terms of feel on the skin, spreadability on the skin, and moisturizing properties, and had an excellent feel when used.

[0133] In contrast, the cosmetic composition of Comparative Example 3, which was prepared using spherical microparticles of low-substituted cellulose ether with a large average primary particle size, and the cosmetic composition of Comparative Example 4, which was prepared using spherical microparticles of low-substituted cellulose ether with low sphericity and surface smoothness, were inferior in any of the feel on the skin, spreadability on the skin, and moisturizing properties, resulting in an inferior sensation in use.

[0134] Furthermore, the cosmetic composition of Reference Example 1, which was prepared using spherical cellulose microparticles, had a poor feel when used, which is presumably due to the fact that spherical cellulose microparticles have poorer water absorption and swelling properties than low-substituted cellulose ether spherical microparticles. [Industrial Applicability]

[0135] The low-substituted cellulose ether spherical microparticles according to one embodiment of the present invention can be used as a component of a cosmetic composition to impart an excellent feel to the cosmetic composition, and the cosmetic composition according to one embodiment of the present invention can be used as a makeup cosmetic, a skin care cosmetic, or the like.

Claims

1. The volume-based average particle diameter (D ５０ ) is 1 μm to 30 μm, the sphericity is 0.75 to 1.0, and the surface smoothness is 75% to 100%.

2. 2. The spherical fine particles of low-substituted cellulose ether according to claim 1, wherein the molar substitution number of the low-substituted cellulose ether is from 0.05 to 1.

0.

3. A cosmetic composition comprising the spherical microparticles of the low-substituted cellulose ether according to claim 1 or 2 and an oil.

4. The cosmetic composition according to claim 3, further comprising water.

5. A method for producing the low-substituted cellulose ether spherical microparticles according to claim 1 or 2, comprising the steps of: (1) a step of mixing an alkaline aqueous solution of a low-substituted cellulose ether as a raw material with a non-aqueous solvent at a volume ratio of 1:99 to 40:60 to obtain a W / O type low-substituted cellulose ether emulsion; (2) mixing raw materials, that is, an aqueous acid solution and a non-aqueous solvent, at a volume ratio of 1:99 to 40:60 to obtain a W / O type aqueous acid solution emulsion; (3) a step of mixing a W / O type low-substituted cellulose ether emulsion liquid with a W / O type acidic aqueous solution emulsion liquid to obtain the low-substituted cellulose ether spherical microparticles according to claim 1 or 2; The method comprising:

6. 6. The method for producing low-substituted cellulose ether spherical microparticles according to claim 5, wherein the raw material in step (1) further contains a surfactant, and / or the raw material in step (2) further contains a surfactant.

7. The method for producing low-substituted cellulose ether spherical microparticles according to claim 5, wherein the non-water-soluble solvents are each independently at least one non-water-soluble solvent selected from the group consisting of silicone oil and hydrocarbon solvents having 5 to 10 carbon atoms.

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