Soap composite particles, method for producing same, and cosmetic

Abstract

The problem addressed by the present invention is to provide soap composite particles that can both improve the texture of the skin and sustain the functionality of an inorganic oxide, a method for producing the soap composite particles, and a cosmetic containing the soap composite particles. The soap composite particles of the present invention have a core particle containing a saturated higher fatty acid salt and an inorganic oxide and an inorganic oxide externally attached to the core particle and are characterized in that the content of the inorganic oxide in the soap composite particles is 5 to 80 wt% and the shape of the core particle is spherical with a circularity of 0.80 to 1.00.

Description

Soap composite particles, their manufacturing method, and cosmetics

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

[0002] Patent Document 1 discloses a metal soap and a method for producing the same that can impart high dispersibility or coating properties to powder and improve the powder's anti-caking properties, fluidity, or feel. The metal soap described in Patent Document 1 is characterized by an internal incorporation ratio A, defined as the proportion of inorganic crystal nucleating agent incorporated into the interior of the metal soap particle, of 30% or more. The internal incorporation ratio A defined in Patent Document 1 is expressed by the following formula (1): Internal incorporation ratio A=100-(X / X')×100 (1)

[0003] In formula (1), X is the content of inorganic nucleating agent in the metal soap, X' is the content of inorganic nucleating agent in the ground metal soap that has passed through a 325-mesh filter, and X and X' are average values ​​obtained by elemental analysis under specified conditions using a scanning electron microscope / energy dispersive X-ray spectroscopy (SEM / EDX). The higher the content of inorganic nucleating agent that would not be observed without grinding, the smaller the value of X relative to X' and the larger the internal uptake rate A.

[0004] Patent No. 6729546

[0005] Patent Document 1 suggests that when an inorganic crystal nucleating agent is incorporated inside metal soap particles, the metal soap particles have a uniform shape and a sharp particle size distribution, and that the solid powder cosmetic preparations in the examples have a good feel to the touch. However, Patent Document 1 does not state or suggest how to achieve both an improvement in skin feel and the sustainability of the inorganic oxide's functions.

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide soap composite particles that can achieve both improved skin feel and sustained functionality of inorganic oxides, a method for producing the same, and cosmetics containing the soap composite particles.

[0007] A first aspect of the present invention is a soap composite particle having a core particle containing a saturated higher fatty acid salt and an inorganic oxide, and an inorganic oxide externally added to the core particle, wherein the content of the inorganic oxide in the soap composite particle is 5 to 80 wt %, and the core particle has a spherical shape with a circularity of 0.80 to 1.00.

[0008] A second aspect is the soap composite particle of the first aspect, characterized in that the number of carbon atoms in the saturated higher fatty acid salt is in the range of 10 to 20. A third aspect is the soap composite particle of the first or second aspect, characterized in that the metal forming the saturated higher fatty acid salt is one or more of Li, Na, Al, Mg, Ca, Zn, and Ba.

[0009] A fourth aspect is the soap composite particle of any one of aspects 1 to 3, characterized in that the content of the inorganic oxide in the core particle is 5 to 75 wt %, and the amount of the inorganic oxide added externally is 0.01 to 5.0 parts by weight per 100 parts by weight of the core particle. A fifth aspect is the soap composite particle of any one of aspects 1 to 4, characterized in that the inorganic oxide is one or more of zinc oxide, magnesium oxide, titanium dioxide, mica, talc, kaolin, sericite, silica, iron oxide, alumina, zirconia, chromium oxide, and zeolite.

[0010] A sixth aspect is the soap composite particle of any one of the first to fifth aspects, characterized in that the volume-based median diameter of the core particles is greater than 3 μm and less than 20 μm. A seventh aspect is the soap composite particle of any one of the first to sixth aspects, characterized in that the inorganic oxide has been hydrophobized. An eighth aspect is the soap composite particle of the seventh aspect, characterized in that the hydrophobization treatment is any one of silane coupling treatment, silicone oil treatment, and fatty acid salt treatment. A ninth aspect is the soap composite particle of any one of the first to eighth aspects, characterized in that the inorganic oxide has an average particle size of 0.01 to 0.8 μm.

[0011] The tenth aspect is a method for producing soap composite particles according to any one of the first to ninth aspects, characterized in that it comprises a kneading step of melting and kneading a mixed powder of a saturated higher fatty acid salt and an inorganic oxide, a pulverizing step of pulverizing the solid kneaded product obtained in the kneading step, a spheronizing step of heating the particles obtained in the pulverizing step to make them spherical, and an external addition step of externally adding an inorganic oxide to the core particles obtained in the spheronizing step.

[0012] An eleventh aspect is a cosmetic comprising the soap composite particles of any one of the first to ninth aspects.

[0013] According to the present invention, it is possible to provide soap composite particles that can achieve both improved skin feel and sustained functionality of inorganic oxides, and a method for producing the same. Furthermore, according to the present invention, it is possible to provide cosmetics containing the soap composite particles, and it is expected that such cosmetics will have a good skin feel while maintaining the sustained functionality of soap.

[0014] The present invention will be described below using embodiments, but these embodiments are specifically described to provide a better understanding of the gist of the invention and do not limit the present invention unless otherwise specified. Other embodiments in which those skilled in the art appropriately replace the configuration of the following embodiments are also included in the scope of the present invention.

[0015] The present invention relates to a soap composite particle, which has a core particle containing a saturated higher fatty acid salt and an inorganic oxide, and an inorganic oxide externally added to the core particle.

[0016] <Saturated Higher Fatty Acid Salts> The saturated higher fatty acid salts may be salts of alkali metals such as sodium and potassium, or metal salts other than alkali metal salts. The saturated higher fatty acid salts may be produced by conventional methods using saturated higher fatty acids or their alkali metal salts and inorganic metal salts as raw materials, or commercially available salts may be used. The saturated higher fatty acid salts may be one type or a mixture of two or more types. Suitable saturated higher fatty acids used in the saturated higher fatty acid salts include hexanoic acid, caproic acid (n-hexanoic acid), heptanoic acid, octanoic acid, caprylic acid (n-octanoic acid), nonanoic acid, decanoic acid, capric acid (n-decanoic acid), lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, behenic acid, and montanic acid.

[0017] Because saturated higher fatty acids do not have double bonds (unsaturated bonds) in the hydrocarbon chain, they are highly chemically stable, resistant to deterioration by oxygen and ultraviolet rays, and tend to maintain excellent quality. The saturated higher fatty acid salt may be branched, but the number of carbon atoms contained in the branched side chain is preferably 2 or less, and more preferably 1 or less. Linear saturated higher fatty acid salts are particularly preferred. By using linear saturated higher fatty acid salts, the hydrocarbon chain does not have double bonds (unsaturated bonds) or side chains, so the structure is stable and the methyl groups at the molecular ends are neatly arranged on the surface of the soap composite particles. Furthermore, because the melting point is high, they are less likely to become liquid at room temperature (5 to 35°C), and tend to maintain excellent quality.

[0018] The number of carbon atoms in the saturated higher fatty acid salt is not particularly limited, but may be, for example, within the range of 8 to 30, preferably within the range of 10 to 20, more preferably within the range of 10 to 18, and particularly preferably within the range of 12 to 18. When the number of carbon atoms is equal to or greater than the lower limit, the saturated higher fatty acid salt exhibits hydrophobicity and is less susceptible to the effects of moisture. When the number of carbon atoms is equal to or less than the upper limit, the molecules are more likely to align, the structure is stable, the melting point is higher, and the durability is improved.

[0019] The metal salt used for the saturated higher fatty acid salt is not particularly limited, but examples thereof include alkali metal salts, alkaline earth metal salts, and transition metal salts. Metals forming the saturated higher fatty acid salt include one or more of Li, Na, Al, Mg, Ca, Zn, and Ba, preferably one or more of Zn, Mg, Ca, and Al, and more preferably one or more of Zn, Mg, and Ca. These compounds form a stable structure in the soap itself. Among these, it is preferable to select a compound that has little effect on the human body and is insoluble in water.

[0020] In particular, when a composition containing soap composite particles is applied to the skin, the molecular ends form a uniform hydrophobic surface when a saturated higher fatty acid salt is used, which makes the composition less susceptible to the effects of moisture in the air and moisture in body fluids such as sweat, improving the feel on the skin. Examples of uses of compositions applied to the skin include cosmetics, pharmaceuticals, and other drugs.

[0021] The saturated higher fatty acid salt has a carboxylate ion group (-COO) at one end. － It is preferable that the saturated higher fatty acid salt does not contain polar functional groups such as hydroxyl groups and epoxy groups, except for the general formula (C). This improves hydrophobicity. ｎ－１ H ２ｎ－１ COO) ｍ Acyclic compounds represented by the general formula [CH ３ (CH ２ ) ｎ－２ COO] ｍ More preferred are straight-chain compounds represented by M. In these general formulas, n represents the number of carbon atoms, and M represents a metal.

[0022] When the metal M is polyvalent, that is, when m is 2 or greater, the carbon number n of the m saturated higher fatty acids may be the same or different. When the carbon numbers n of the m saturated higher fatty acids are different from one another, the difference between the maximum carbon number and the minimum carbon number is preferably 4 or less, and more preferably 2 or less. In order for the molecular ends of the saturated higher fatty acid salt to form a more uniform hydrophobic surface, it is preferable that the carbon numbers of the saturated higher fatty acids constituting the saturated higher fatty acid salt are the same.

[0023] <Inorganic Oxide> The soap composite particle of the embodiment has an inorganic oxide internally added to a core particle and an inorganic oxide externally added to the core particle. The core particle is formed by internally adding an inorganic oxide to a saturated higher fatty acid salt. The inorganic oxide internally added to the core particle may be embedded within the core particle. It is preferable that the inorganic oxide externally added to the core particle covers at least a portion of the outer surface of the core particle.

[0024] Examples of inorganic oxides include inorganic particles of metal oxides, metal nitrides, silicates, sulfates, carbonates, phosphates, etc. Specific examples of inorganic oxides are preferably one or more of zinc oxide, magnesium oxide, titanium dioxide, mica, talc, kaolin, sericite, silica, iron oxide, alumina, zirconia, chromium oxide, and zeolite.

[0025] The inorganic oxide particles are preferably functional particles. The functionality is preferably such that, when the soap composite particles are used, the inorganic oxide particles act on an object together with the saturated higher fatty acid salt. Specific examples of the functionality include, but are not limited to, UV reflectivity, sunscreen, hiding power as a pigment, anti-inflammatory properties, X-ray absorption, solid lubricity, releasability, antibacterial properties, and electrical insulation.

[0026] The content of inorganic oxide in the soap composite particles is preferably 5 to 80 wt%, more preferably 20 to 55 wt%. The content of inorganic oxide in the core particles is preferably 5 to 75 wt%, more preferably 20 to 50 wt%. When the content of inorganic oxide is equal to or greater than the lower limit, the exposed area of ​​the inorganic oxide added to the core particles increases, improving the durability of the inorganic oxide's function. When the content of inorganic oxide is equal to or less than the upper limit, kneading of the saturated higher fatty acid salt and the inorganic oxide becomes easier, improving the uniformity of the core particles.

[0027] The amount of inorganic oxide added externally per 100 parts by weight of core particles is preferably 0.01 to 5.0 parts by weight, more preferably 0.05 to 2.0 parts by weight. When the amount of inorganic oxide added externally is equal to or greater than the lower limit, the amount of inorganic oxide present on the surface of the core particles increases, improving the durability of the inorganic oxide function. When the amount of inorganic oxide added externally is equal to or less than the upper limit, the lubricity and feel characteristic of saturated higher fatty acid salts become more prominent.

[0028] The inorganic oxide externally added to the core particles may be the same type of inorganic oxide as the inorganic oxide internally added to the core particles, or may be a different inorganic oxide. One type of inorganic oxide may be internally added to the core particles, or two or more types may be internally added to the core particles. When two or more types of inorganic oxides are internally added to the core particles, the content may be the total amount of two or more types. One type of inorganic oxide may be externally added to the core particles, or two or more types may be externally added. When two or more types of inorganic oxides are externally added to the core particles, the external addition amount may be the total amount of two or more types.

[0029] The inorganic oxide externally added to the core particles may function as a fluidity imparting agent. In this case, the fluidity imparting agent exerts a bearing effect, increasing the fluidity of the soap composite particles and improving the feel on the skin. As the inorganic oxide externally added to the core particles, particles that function as a fluidity imparting agent may be used in combination with particles having other functions.

[0030] The inorganic oxide may be coated, for example, may be subjected to a hydrophobic treatment. Examples of the hydrophobic treatment include a silane coupling treatment using a silane coupling agent, a silicone oil treatment using a silicone oil such as a long-chain alkylsilane, and a fatty acid salt treatment using a fatty acid salt. In the silicone oil treatment, a modified silicone oil may be used.

[0031] In the case of silane coupling treatment or silicone oil treatment, siloxane bonds are formed and fixed on the surface of the inorganic oxide by hydrolysis and dehydration condensation reaction of the silane coupling agent or silicone oil, and the inorganic oxide is made hydrophobic. Therefore, the inorganic oxide has high dispersibility even when kneaded into soap made of hydrophobic higher saturated fatty acid salt at high temperature.

[0032] In the case of fatty acid salt treatment, the composition of the fatty acid salt is similar to that of the higher saturated fatty acid salt used in soap. Therefore, inorganic oxides surface-treated with fatty acid salts have high dispersibility in the soap into which they are kneaded and high adhesion to the soap. Note that when the fatty acid salt used in the fatty acid salt treatment corresponds to the above-mentioned higher saturated fatty acid salt, its mass may be excluded from the mass of the inorganic oxide and added to the mass of the higher saturated fatty acid salt.

[0033] The average particle size of the inorganic oxide is, for example, in the range of 0.01 to 0.8 μm, preferably in the range of 0.01 to 0.5 μm. When the average particle size of the inorganic oxide is equal to or greater than the lower limit, the inorganic oxide particles are less likely to aggregate and are more likely to disperse. When the average particle size of the inorganic oxide is equal to or less than the upper limit, the inorganic oxide is more likely to be internally added to the core particles, and even when externally added, it is less likely to fall off from the soap composite particles.

[0034] <Core Particles> The core particles are preferably spherical with a circularity of 0.80 to 1.00, and more preferably have a circularity of 0.90 to 1.00. The saturated higher fatty acid salt of the core particles acts as a lubricant, allowing them to roll easily without resistance. When the circularity of the core particles is equal to or greater than the lower limit, the particles roll easily and slide smoothly without resistance. For example, when a composition containing soap composite particles is applied to the skin using the pads of the fingers, the particles roll easily, allowing for a favorable effect on the skin. The theoretical maximum circularity is 1, which corresponds to the case where the particle image is a perfect circle.

[0035] The circularity can be calculated by analyzing a particle image, measuring the area A and the perimeter C of the particle image, and using the following formula, where D is the diameter of a circle (equivalent circle diameter) equal to the area A of the particle image and π is the ratio of the circumference of a particle to its circumference: (Circularity) = πD / C

[0036] As a method for measuring the circularity of particles, for example, a flow particle image analyzer that measures particle shape, particle size distribution, particle number, etc. by two-dimensional image analysis of a particle group may be used. Alternatively, the circularity may be calculated by observing the particle surface from multiple fields of view using an electron microscope and performing three-dimensional image analysis.

[0037] The volumetric median diameter of the core particles is preferably more than 3 μm and less than 20 μm, more preferably more than 5 μm and less than 15 μm, and even more preferably more than 7 μm and less than 10 μm. If the volumetric median diameter of the core particles is above the lower limit, the particles have a low cohesive force and are less likely to form clumps. If the volumetric median diameter of the core particles is below the upper limit, the surface area per unit weight increases, increasing the exposed area of ​​the inorganic oxide added to the core particles and improving the durability of the inorganic oxide's function.

[0038] In applications where a composition containing soap composite particles is applied to the skin, if the volume-based median diameter of the core particles is above the lower limit, the core particles spread easily on the skin and provide a uniform feel when spread. On the other hand, if the volume-based median diameter of the core particles is below the upper limit, the roughness caused by the particle size is less felt by the fingertips, improving the feel on the skin.

[0039] <Method for producing soap composite particles> The present invention relates to a method for producing soap composite particles, which includes, for example, a kneading step of melting and kneading a mixed powder of a saturated higher fatty acid salt and an inorganic oxide, a crushing step of crushing the solid kneaded product, a spheronization step of heating the particles to make them spherical, and an external addition step of externally adding an inorganic oxide to core particles.

[0040] Prior to the kneading step, the method may include a measuring step of measuring the saturated higher fatty acid salt and inorganic oxide to be used in preparing the core particles, and a mixing step of stirring and mixing the measured saturated higher fatty acid salt and inorganic oxide. For mixing the particles, a mixing device such as a double-cone mixer, a V-type mixer, a drum mixer, a super mixer, a Henschel mixer, or a Nauta mixer may be used, although there are no particular limitations thereon.

[0041] Although it is possible to mix some of the raw materials during the kneading step, it is preferable to premix at least some of the raw materials before the kneading step. Premixing is advantageous in controlling the composition of the saturated higher fatty acid salt and inorganic oxide, the particle size, shape, etc.

[0042] The kneading step is preferably carried out under conditions in which the saturated higher fatty acid salt is melted or softened by heating. As a result, the inorganic oxide mixed with the saturated higher fatty acid salt is internally added to the saturated higher fatty acid salt. The kneading machine may be a batch kneader or a continuous kneader. The kneading machine is not particularly limited, but examples thereof include an open roll, a kneader, a pressure kneader, a Banbury mixer, a single-screw extruder, and a twin-screw extruder. The heating temperature in the kneading step can be appropriately set depending on the melting point of the saturated higher fatty acid salt, and may be, for example, about 80 to 250°C, or about 100 to 200°C.

[0043] The pulverization step is a step of granulating the solid kneaded material obtained by cooling the kneaded material obtained in the kneading step. Therefore, it is preferable to carry out a cooling step between the kneading step and the pulverization step. The molten kneaded material may be passed through a cooling roll, for example, to allow a cooling member in contact with the kneaded material to absorb residual heat. The cooling member, such as a cooling roll, may have a refrigerant, such as cooling water, inside. In the cooling step, heat can also be dissipated from the kneaded material by air cooling, blowing air, or the like.

[0044] The pulverization step may be carried out in multiple stages, such as a coarse pulverization step and a fine pulverization step. The device used for coarse pulverization of particles is not particularly limited, but a crusher, hammer mill, feather mill, cutter mill, etc. can be used. The device used for fine pulverization of particles is not particularly limited, but a jet mill, counter jet mill, high-speed rotor rotary mill, etc. can be used.

[0045] When the solid kneaded product is pulverized to a desired particle size, the particle size may be adjusted by a classification step as necessary. For example, an elbow jet classifier using an inertial classification method, a microplex using a centrifugal classification method, or an airflow classifier may be used for the classification step. Particles coarser than the desired particle size may be returned to the pulverization step for further pulverization. Particles finer than the desired particle size may be returned to the kneading step and reused depending on the composition.

[0046] The spheronization step is a step of spheronizing the particles obtained in the pulverization step by heating. The spheronization device is not particularly limited, but examples include a device that mechanically adjusts particle shape, such as an impact spheronization device; a device that adjusts particle shape by dissolving a binder and removing the solvent, such as a spray dryer; and a device that adjusts particle shape by heating in a medium or using hot air. The spheronization step yields spherical core particles in which an inorganic oxide is internally added to a saturated higher fatty acid salt. If necessary, a classification step can be carried out after the spheronization step of the core particles.

[0047] In the external addition step, the inorganic oxide is externally added to the core particles by mixing the inorganic oxide with the core particles. For the external addition step of the inorganic oxide, a mixing device such as a Super Mixer or a Henschel Mixer may be used, or a powder processing device such as a Mechano Mill may be used.

[0048] <Soap composite particles> The soap composite particles of the present invention have the functionality of the saturated higher fatty acid salt as well as the functionality of the internally or externally added inorganic oxide, and therefore can be used as a variety of functional materials. The uses of the soap composite particles are not particularly limited, but examples thereof include a feel improver, a lubricant, a release agent, an anti-caking agent, a cosmetic raw material, a colorant, a processing aid, a dispersant, and an additive.

[0049] <Method for analyzing soap composite particles> As described above, the soap composite particles of the present invention have an inorganic oxide internally added to the core particle and an inorganic oxide externally added to the core particle. Since the core particle is mainly composed of a saturated higher fatty acid salt, it is possible to separate the saturated higher fatty acid salt from the inorganic oxide. This makes it possible to evaluate the amount of internal addition and the amount of external addition even if the inorganic oxide internally added to the core particle and the inorganic oxide externally added to the core particle are the same substance.

[0050] A specific example of a method for separating the core particles from the external additives (externally added inorganic oxides) is to add a pre-weighed amount of soap composite particle powder to a dispersion medium, insert the probe of an ultrasonic homogenizer into the resulting dispersion, and irradiate it with ultrasonic waves. This allows the external additives that have fallen off the core particles to suspend in the dispersion medium. After allowing the core particles to settle by standing or centrifuging, the supernatant liquid in which the external additives are suspended can be extracted and separated by a liquid separation operation, etc.

[0051] The dispersion medium is preferably an aqueous solution prepared by dissolving a surfactant in water to prevent the powder from agglomerating. Because the saturated higher fatty acid salt is insoluble in water, the added inorganic oxide can be maintained in a state of being enclosed in the core particles.

[0052] The amount of core particles from which the external additives have been separated can be determined by repeatedly washing the sediment with a solvent and filtering it using filter paper capable of capturing the core particles, then drying and weighing the sediment. The filter paper's collection performance is preferably such that it can retain particles of, for example, 1 μm or larger. The amount of external additives may be calculated by subtracting the mass of the core particles obtained by weighing from the mass of the soap composite particles.

[0053] The components and composition of the external additives contained in the supernatant can be analyzed, for example, by X-ray fluorescence analysis (XRF) of the supernatant.The components and composition of the inorganic oxides internally added to the core particles can be analyzed, for example, by X-ray fluorescence analysis (XRF) of the core particles obtained as precipitates.

[0054] <Cosmetics Comprising Soap Composite Particles> The cosmetics of the present invention comprise the soap composite particles described above. Examples of cosmetics containing soap composite particles include makeup cosmetics such as foundation, liquid foundation, eye shadow, blush, face powder, concealer, blush, eyebrow powder, and highlighter; cleansing agents such as cleansers and facial washes; skin care cosmetics such as massage creams, moisturizing creams, and emulsions; body care cosmetics such as bath additives, sunscreens, sunscreen creams, and deodorant sprays; basic cosmetics such as makeup bases; and hair care cosmetics such as shampoos, conditioners, hair liquids, and hair colors. These cosmetics can be prepared by mixing and processing various raw materials in proportions appropriate for the intended use.

[0055] The cosmetic of the present invention can contain the above-mentioned soap composite particles in a range of 0.5% by mass to 60% by mass relative to the total amount of the cosmetic. Preferably, the soap composite particles can be contained in a range of 1% by mass to 40% by mass, and more preferably 2% by mass to 30% by mass relative to the total amount of the cosmetic. If the content of the soap composite particles is less than 0.5% by mass, it is difficult to feel the effect of improving the skin feel when using the cosmetic, and if it exceeds 60% by mass, it is not possible to expect an effect commensurate with the amount blended, and problems may arise in maintaining the quality and stability of the cosmetic.

[0056] In addition to the soap composite particles, the cosmetic of the present invention can contain various components conventionally used in cosmetics. Examples include pigments, surface-treated pigments, UV absorbers, physiologically active ingredients, oils, surfactants, fluorine compounds, resins, thickeners, preservatives, fragrances, moisturizers, salts, solvents, antioxidants, chelating agents, neutralizing agents, pH adjusters, and insect repellents. These components can be added in amounts that do not inhibit the effects of the cosmetic of the present invention.

[0057] The present invention has been described above based on preferred embodiments, but the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0058] Examples of the present invention will be described below, but the present invention is not limited to these examples.

[0059] <Production of Soap Composite Particles> Soap composite particles in which an inorganic oxide was externally added to core particles containing a saturated higher fatty acid salt and an inorganic oxide were produced by carrying out the following steps.

[0060] (Mixing Step) As shown in the "Saturated higher fatty acid salt" and "Amount of inorganic oxide added internally" in Tables 1 to 4, the saturated higher fatty acid salt and the inorganic oxide were each weighed, placed in a 20 L Henschel mixer (FM20 manufactured by Nippon Coke and Engineering Co., Ltd.), and mixed by stirring to obtain a mixed powder.

[0061] (Kneading step) The mixed powder obtained in the mixing step was melt-kneaded by heating to 120 to 140° C. in a twin-screw kneader (PCM-30 manufactured by Ikegai Corporation). The molten kneaded product discharged from the kneader was passed through a cooled rolling mill to obtain a plate-shaped solid kneaded product.

[0062] The plate-like solid kneaded product obtained in the mixing step was coarsely pulverized using a hammer mill to obtain a coarsely pulverized product of 0.5 to 3.0 mm. The coarsely pulverized product was then finely pulverized using a jet mill (Ultra Sonic Jet Mill I-2, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain a finely pulverized product having a volume-based average particle size of 3 to 20 μm.

[0063] (Classification Step) The finely pulverized material obtained in the pulverization step was subjected to an air classifier (DS2UR manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to remove particles of 3 μm or less.

[0064] (Spheronization Step) The classified powder obtained in the classification step was treated in a hot air spheronizing device (Meteor Rainbow MR, manufactured by Nippon Pneumatic Mfg. Co., Ltd.) heated to 360°C to be spheronized.

[0065] (External Addition Step) To the spherical core particles obtained in the spheronization step, inorganic oxides were externally added as shown in the "Amount of Externally Added Inorganic Oxide" in Tables 1 to 4, to obtain soap composite particles.

[0066] <Structure of Core Particles> The spherical core particles obtained in the spheronization step were used as samples to measure the structure of the core particles by the following method. Note that core particles separated from external additives using the above-mentioned method for analyzing soap composite particles can also be used as samples.

[0067] (Circularity) The circularity of the core particles was measured using a flow-type particle image analyzer.

[0068] (Volume-Based Median Diameter) The median diameter (D50) was determined by measuring the volume distribution using a Coulter counter, utilizing the electrical change that occurs when the core particles pass through an aperture tube.

[0069] <Skin Texture Evaluation Method> An earpick-sized amount of soap composite particle powder was placed on the wrist of one arm, and the powder was gently rolled over the skin with the middle finger of the other hand in a 4-cm diameter circle for 15 seconds, and the texture was evaluated using the middle finger and wrist. Four evaluation panelists (two adult males and two adult females) classified the usability into each category and gave a score for each category for a sensory evaluation. The evaluation items and evaluation criteria are as follows: (Evaluation Items) Spreadability: Whether the powder spreads well on the skin when applied. Stickiness: Whether the powder fills pores well when applied. Smoothness: Whether the skin feels good when applied and after application. Lightness: Whether the powder feels light and heavy after application. Lasting: Whether the makeup lasts well when rubbed with fingers after application. Softness: Whether the powder feels soft when applied and after application. (Score for each item) 5: Excellent. 4: Excellent. 3: Average. 2: Poor. 1: Very poor. (Evaluation criteria) ◎: Total score is 24 or more and 30 or less. ○: Total score is 18 or more and less than 24. △: Total score is 12 or more and less than 18. ×: Total score is 6 or more and less than 12.

[0070] <Method for Evaluating the Durability of Titanium Dioxide Function> As a function of titanium dioxide, the SPF (Sun Protection Factor) value, which is an index of the ultraviolet protection function, indicating how well it can block UVB rays in ultraviolet rays, was measured. Specifically, a powder of soap composite particles was applied to a polymethyl methacrylate (PMMA) plate and dried, and the SPF value of the prepared sample was measured using an SPF analyzer. The evaluation value was the average of the measurements taken at five locations. A practically acceptable level of ultraviolet protection function is an SPF of 20 or higher.

[0071] (Evaluation criteria) ⊚: The average SPF value is 40 or more. ◯: The average SPF value is 30 or more and less than 40. Δ: The average SPF value is 20 or more and less than 30. ×: The average SPF value is less than 20.

[0072] <Method for evaluating the durability of zinc oxide function> As a function of zinc oxide, the UVAPF (Ultraviolet A Protection Factor) value, which is an index of the ultraviolet protection function of zinc oxide, indicating how much UVA in ultraviolet rays it can block, was measured. Specifically, a powder of soap composite particles was applied to a polymethyl methacrylate (PMMA) plate and dried, and the UVAPF value of the prepared sample was measured using an SPF analyzer. The evaluation value was the average of the measurements at five points.

[0073] (Evaluation criteria) ⊚: The average UVAPF value is 16 or more. ◯: The average UVAPF value is 8 or more and less than 16. Δ: The average UVAPF value is 4 or more and less than 8. ×: The average UVAPF value is 2 or more and less than 4.

[0074] <Method for Evaluating the Durability of Zeolite Function> The antibacterial effect of zeolite was evaluated as a function of the zeolite. The test strains used were Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus niger, and Candida, which are standard strains used in testing the preservative effectiveness of cosmetics, as well as Propionibacterium acnes and Malassezia, which are normal flora of human skin.

[0075] The evaluation sample was inoculated with 1.0 x 10 ５A test sample was prepared by adding 0.1 g of soap composite particles to 1 mL of a test bacterial solution containing CFU (Colony Forming Unit) / mL. A blank sample was prepared by adding 1 mL of the test bacterial solution alone. After 24 hours, the number of live bacteria was measured using a standard method, and the antibacterial properties were evaluated based on the survival rate of the bacteria according to the following evaluation criteria.

[0076] (Evaluation criteria) ⊚: The survival rate of bacteria is 0% or more and 20% or less. ○: The survival rate of bacteria is more than 20% and 70% or less. △: The survival rate of bacteria is more than 71% and 95% or less. ×: The survival rate of bacteria is more than 95% and 100% or less.

[0077] <Overall Evaluation> The overall evaluation was based on the evaluation of the feel on the skin and the evaluation of the durability of the function, and was evaluated according to the following evaluation criteria.

[0078] (Evaluation criteria) ◎: Both the evaluation of texture and the evaluation of durability of function are ◎. ○: At least one evaluation is ○, and no evaluations of △ or × are included. △: At least one evaluation is △, and no evaluations of × are included. ×: At least one evaluation is ×.

[0079] <Evaluation Results> The evaluation results are shown in Tables 1 to 4. In the "Saturated higher fatty acid salt" column, the fatty acid salt is displayed by combining the name of the fatty acid with the element symbol of the metal, for example, "Ca stearate" represents "calcium stearate." In some comparative examples, unsaturated fatty acid salts were used.

[0080] Stearic acid (18 carbon atoms), lauric acid (12 carbon atoms), palmitic acid (16 carbon atoms), caprylic acid (8 carbon atoms), and behenic acid (22 carbon atoms) are straight-chain saturated fatty acids. Oleic acid (18 carbon atoms, 1 double bond) and linoleic acid (18 carbon atoms, 2 double bonds) are straight-chain unsaturated fatty acids.

[0081] The weight parts in Tables 1 to 4 were set so that the total of the saturated higher fatty acid salt and the internally added amount of inorganic oxide was 100 parts by weight. Therefore, the value of the internally added amount of inorganic oxide (parts by weight) is equal to the value of the content (wt%) of inorganic oxide in the core particles.

[0082] In the "Total (wt%)" column of "Inorganic Oxides" in Tables 1 to 4, the ratio of the total amount of inorganic oxides (total of internally added amount and externally added amount) to the total amount of soap composite particles (total of saturated higher fatty acid salts and inorganic oxides) is calculated and displayed to one decimal place.

[0083] In the "Hydrophobic Treatment" column of Tables 1 to 4, the inorganic oxides that were not hydrophobicized are indicated as "None," those that were silane coupling treated are indicated as "SiCp," those that were silicone oil treated are indicated as "SiOi," and those that were fatty acid salt treated are indicated as "FAS."

[0084]

[0085]

[0086]

[0087]

[0088] In Examples 1 to 27, the content of inorganic oxide in the soap composite particles was 5 to 80% by weight, and the shape of the core particles was spherical with a circularity of 0.80 to 1.00. The overall evaluation of these was ⊚, ○, or △.

[0089] Comparative Examples 1 to 5 received an X in the overall evaluation. Comparative Example 1 had a circularity of less than 0.80 for the core particles, but received an X in the evaluation of skin feel. Comparative Example 2 had an inorganic oxide content of less than 5% by weight in the soap composite particles, but received an X in the evaluation of function durability. Comparative Examples 3 and 4 used unsaturated fatty acid salts instead of saturated higher fatty acid salts, but received an X in the evaluation of skin feel. Comparative Example 5 had an inorganic oxide content of more than 80% by weight in the soap composite particles, but received an X in the evaluation of skin feel.

[0090] The soap composite particles of the present invention can achieve both an improvement in skin feel and durability of the inorganic oxide function, and can be used in the production of cosmetics.

Claims

1. Soap composite particles having core particles containing a saturated higher fatty acid salt and an inorganic oxide, and an inorganic oxide externally added to the core particles, wherein the content of the inorganic oxide in the soap composite particles is 5 to 80% by weight, and the core particles are spherical with a circularity of 0.80 to 1.

00.

2. The soap composite particles according to claim 1, characterized in that the number of carbon atoms in the saturated higher fatty acid salt is in the range of 10 to 20.

3. The soap composite particles according to claim 1, wherein the metal forming the saturated higher fatty acid salt is one or more of Li, Na, Al, Mg, Ca, Zn, and Ba.

4. Soap composite particles as described in claim 1, characterized in that the content of the inorganic oxide in the core particles is 5 to 75 weight % and the amount of the inorganic oxide added externally per 100 weight parts of the core particles is 0.01 to 5.0 weight parts.

5. The soap composite particles according to claim 1, characterized in that the inorganic oxide is one or more of zinc oxide, magnesium oxide, titanium dioxide, mica, talc, kaolin, sericite, silica, iron oxide, alumina, zirconia, chromium oxide, and zeolite.

6. The soap composite particle according to claim 1, characterized in that the volume-based median diameter of the core particle is greater than 3 μm and less than 20 μm.

7. The soap composite particles according to claim 1, wherein the inorganic oxide has been subjected to a hydrophobic treatment.

8. The soap composite particles according to claim 7, characterized in that the hydrophobic treatment is any one of a silane coupling treatment, a silicone oil treatment, and a fatty acid salt treatment.

9. The soap composite particles according to claim 1, characterized in that the inorganic oxide has an average particle size of 0.01 to 0.8 μm.

10. A method for producing soap composite particles according to any one of claims 1 to 9, comprising: a kneading step of melting and kneading a mixed powder of a saturated higher fatty acid salt and an inorganic oxide; a grinding step of grinding the solid kneaded product obtained in the kneading step; a spheronization step of heating the particles obtained in the grinding step to make them spherical; and an external addition step of externally adding an inorganic oxide to the core particles obtained in the spheronization step.

11. A cosmetic comprising the soap composite particles according to any one of claims 1 to 9.