Aqueous dispersions and cosmetics

Abstract

To provide an aqueous dispersion of organosilicon surface-coated zinc oxide particles having a low viscosity, a high concentration and a smaller amount of dispersant than the conventional one.SOLUTION: There is provided an aqueous dispersion which contains organosilicon surface-coated zinc oxide particles (A), a non-ionic surfactant (B), a polyhydric alcohol (C) and water (D), wherein the organosilicon surface-coated zinc oxide particles (A) have a primary particle diameter of 0.1 μm or less as measured from transmission electron micrographs, the content of the organosilicon surface-coated zinc oxide particles (A) is 60 mass% or more based on the total amount of the aqueous dispersion, the ratio of (the parallel light transmittance of the coating film after drying) / (the parallel light transmittance of the coating film immediately after coating) at a wavelength of 600 nm is 0.8 or more, the coating film after drying is obtained by coating an aqueous dispersion containing 60 mass% of the organosilicon surface-coated zinc oxide particles (A) at room temperature followed by drying at 50°C for two hours and the coating film immediately after coating is obtained within five minutes after the aqueous dispersion containing 60 mass% of the organosilicon surface-coated zinc oxide particles (A) is coated at room temperature.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to aqueous dispersions and cosmetic compositions. [Background technology]

[0002] Because of its high UV-blocking properties and transparency, zinc oxide particles have been used as UV scattering agents in sunscreens and other cosmetics. While zinc oxide particles with a particle size of 100 nm or less are commonly used as UV scattering agents, surface treatments such as water-repellent treatments are often applied to the particle surface to suppress surface activity, reduce friction, and prevent aggregation.

[0003] However, these surface-treated zinc oxide microparticles also aggregate to a considerable extent, and unless some kind of dispersion treatment is applied or a dispersant is used in combination when manufacturing the dispersion, the particles cannot exhibit their inherent properties (see, for example, Patent Documents 1 and 2). Furthermore, for particulate dispersions, a high-concentration, low-viscosity dispersion with a small amount of dispersant is desirable in terms of ease of incorporation into formulations and improvement of the formulation's feel. However, because particulate zinc oxide has a high specific surface area, it has been difficult to increase the powder concentration with a small amount of dispersant. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6536561 [Patent Document 2] Japanese Patent Publication No. 2019-081803 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide an aqueous dispersion of organosilicon-coated zinc oxide particles that has low viscosity and high concentration, and requires less dispersant than conventional methods. [Means for solving the problem]

[0006] The present invention relates to an aqueous dispersion comprising organosilicon-coated zinc oxide particles (A), a nonionic surfactant (B), a polyhydric alcohol (C), and water (D), The above organosilicon-coated zinc oxide particles (A) have a primary particle diameter of 0.1 μm or less, as measured from transmission electron microscope images. The content of the above organosilicon-coated zinc oxide particles (A) is 60% by mass or more relative to the total amount of the aqueous dispersion. The ratio of (parallel light transmittance of the coating film after drying) / (parallel light transmittance of the coating film immediately after application) at a wavelength of 600 nm is 0.8 or higher. The above-mentioned dried coating film is obtained by applying an aqueous dispersion containing 60% by mass of the organosilicon surface-coated zinc oxide particles (A) at room temperature and then drying it at 50°C for 2 hours. The above-mentioned coating immediately after application is formed within 5 minutes after application at room temperature of an aqueous dispersion containing 60% by mass of the organosilicon-coated zinc oxide particles (A). This invention relates to an aqueous dispersion characterized by the following features.

[0007] Preferably, the above organosilicon-coated zinc oxide particles (A) are placed in isopropyl alcohol and dispersed by irradiating them with ultrasonic waves at a rated output of 600 W and vibration amplitude of 100% using an ultrasonic homogenizer for 30 seconds at room temperature. The median diameter of the dispersion obtained by laser diffraction scattering is 0.15 μm or less on a volume basis. The content of the above-mentioned nonionic surfactant (B) is preferably 8.5% by mass or less relative to 100% by mass of organosilicon-coated zinc oxide particles (A). The above organosilicon-coated zinc oxide particles (A) preferably have a median diameter of 0.15 μm or less in an aqueous dispersion. The above aqueous dispersion preferably has a viscosity of 4,000 mPa·s or less at 25°C. When the above-mentioned dried coating film is observed with an interference microscope, it is preferable that there are 30 or fewer aggregates of 2 μm or larger in a 100 μm × 100 μm field of view, and that the gloss (20° gloss) is 80 or higher.

[0008] The above nonionic surfactant (B) is preferably an organopolysiloxane-based nonionic surfactant. The polyhydric alcohol (C) is preferably one or more polyhydric alcohols selected from the group consisting of propylene glycol, butylene glycol, pentanediol, dipropylene glycol, hexanediol, heptanediol, and glycerin. The present invention is also a cosmetic composition characterized by containing the above-mentioned aqueous dispersion. [Effects of the Invention]

[0009] The present invention makes it possible to obtain an aqueous dispersion of fine-particle zinc oxide with a reduced amount of dispersant. Furthermore, because the aqueous dispersion of the present invention has low viscosity and high concentration, it can be suitably incorporated into cosmetics, heat-dissipating compositions, and the like. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram illustrating a method for measuring the primary particle size of organosilicon-coated zinc oxide particles used in the present invention. [Modes for carrying out the invention]

[0011] The present invention will be described in detail below. The aqueous dispersion of the present invention contains organosilicon-coated zinc oxide particles (A) that have excellent dispersibility. That is, because organosilicon-coated zinc oxide particles (A) with very high dispersibility are used, an aqueous dispersion in which fine zinc oxide particles are stably dispersed at a high concentration can be obtained even with a small amount of dispersant. Such aqueous dispersions are preferable because they allow for the incorporation of the desired amount of finely particulated zinc oxide in small quantities, making them easy to incorporate into pharmaceutical formulations.

[0012] The above organosilicon-coated zinc oxide particles (A) exhibit excellent dispersibility and are expected to disperse in a solvent to a state close to that of primary particles. Such organosilicon surface-coated zinc oxide particles (A) have a primary particle diameter of 0.1 μm or less as measured from a transmission electron microscope photograph.

[0013] Specifically, the primary particle diameter in the present invention is the fixed-direction diameter (the distance between two parallel lines in a certain direction sandwiching the particle; measured in a certain direction for any shaped particles on the image) in the field of view at 2000 - 50000 times the magnification of the photograph taken with a transmission electron microscope JEM-1200EX II (manufactured by JEOL Ltd.), and is the particle diameter (μm) defined by measuring the fixed-direction diameters of 250 primary particles in the TEM photograph and obtaining the average value of the cumulative distribution. Regarding the method for measuring the above primary particle diameter, FIG. 1 is attached. More preferably, the above primary particle diameter is 0.005 μm or more and less than 0.08 μm.

[0014] The aqueous dispersion of the present invention has a ratio of (parallel light transmittance of the dried coating film) / (parallel light transmittance of the coating film immediately after coating) at a wavelength of 600 nm in an aqueous dispersion containing 60% by mass of organosilicon surface-coated zinc oxide particles (A) of 0.8 or more. Those satisfying such a value have suppressed dry aggregation, and thus the zinc oxide particles are well dispersed in the aqueous dispersion of the present invention. Hereinafter, the parallel light transmittance in the said parameter will be described in detail.

[0015] (Parallel light transmittance) An aqueous dispersion containing 60% by mass of the above organosilicon surface-coated zinc oxide particles (A) was applied at room temperature. Immediately after application (in the present invention, within 5 minutes after application), it was designated as coating film 1, and the coating film 1 dried at 50 °C for 2 hours was designated as coating film 2. The parallel light transmittance 1 (%) and parallel light transmittance 2 (%) at a wavelength of 600 nm for each were measured. The preparation of the above coating film, drying conditions, measurement of parallel light transmittance, etc., can be carried out by the method described in the examples. For aqueous dispersions containing more than 60% by mass of organosilicon-coated zinc oxide particles (A), a portion of the aqueous dispersion is taken out and diluted with water so that the content of organosilicon-coated zinc oxide particles (A) becomes 60% by mass before being used to prepare the coating film. The means of stirring during dilution are not particularly limited and can be used with commonly used stirrers such as stirring blades or homodispersers.

[0016] A higher value for parallel light transmittance of 1 (%) and 2 (%) indicates higher visible light transparency. A higher ratio of parallel light transmittance of 2 to parallel light transmittance of 1 indicates less drying aggregation and suppression of white cast. The above parallel light transmittance of 1 (%) is preferably 35% or more, and more preferably 45% or more. Furthermore, the above-mentioned parallel light transmittance 2 (%) is preferably 30% or more, and more preferably 40% or more.

[0017] In the present invention, the ratio of parallel light transmittance 2 to parallel light transmittance 1, i.e., (parallel light transmittance of coating film 2 2) / (parallel light transmittance of coating film 1 1), is 0.8 or more. When the above ratio is 0.8 or more, it means that whiteness is sufficiently suppressed. Preferably, the above (parallel light transmittance of coating film 2 2) / (parallel light transmittance of coating film 1 1) is 0.9 or more.

[0018] The aqueous dispersion of the present invention is further preferably such that, when a coating film 1, 2 is formed, the coating film has the following properties.

[0019] (paint film unevenness) When the surface of the coating film 2 is observed with an interference microscope, it is preferable that the number of aggregates 2 μm or larger observed within a 100 μm × 100 μm area be 30 or less, and more preferably 20 or less. It is preferable that the number of aggregates be 30 or less, as this means that drying aggregation of fine zinc oxide particles is less likely to occur and the surface is less uneven. The aggregates described above can be observed by the method described in the examples.

[0020] (Glossy (20° gloss)) The gloss of the above coating film 2 is preferably 80 or higher. A higher gloss (20° gloss) value indicates that the dispersion of fine zinc oxide particles within the created coating film is high, making drying aggregation less likely and resulting in less surface irregularity of the coating film. The gloss is more preferably 100 or higher. The gloss (20° gloss) described above can be measured by the method described in the examples.

[0021] The organosilicon-coated zinc oxide particles used in this invention are zinc oxide particles that have been surface-treated with an organosilicon compound. The above organosilicon compounds are not particularly limited as long as they are compounds that generate a silanol hydroxyl group by hydrolysis, for example, methyltriethoxysilane, methyltrimethoxysilane, methyltrichlorosilane, dimethyldiethoxysilane, dimethyldimethoxysilane, dimethyldichlorosilane, phenyltriethoxysilane, phenyltrimethoxysilane, phenyltrichlorosilane, hexyltriethoxysilane, hexyltrimethoxysilane, hexyltrichlorosilane, octyltriethoxysilane, octyl Examples of organosilicon compounds include trimethoxysilane, octyltrichlorosilane, decyltriethoxysilane, decyltrimethoxysilane, decyltrichlorosilane, tetraethoxysilane, trimethylchlorosilane, hexamethyldisilazane, hexamethyldisiloxane, and perfluoroalkyltrimethoxysilane, as well as organopolysiloxanes such as methylhydrogenpolysiloxane and dimethylpolysiloxane, and silane coupling agents such as triethoxyvinylsilane and diphenyldimethoxysilane. One or more of the above organosilicon compounds may be used in combination.

[0022] The amount of organosilicon coating is preferably 0.1% by mass or more and 0.6% by mass or less, in terms of silicon. If it is less than 0.1% by mass, it may not exhibit sufficient water-repellent effect. If it is more than 0.6% by mass, the purity of zinc oxide may decrease, and the performance may deteriorate.

[0023] The above organosilicon coating amount is the silicon value measured by semi-quantitative analysis using the fission product (FP) method on organosilicon-coated zinc oxide particles formed by a press machine. In this invention, the silicon value obtained by the measurement method described above includes the silicon in the organosilicon compound coated on the surface of the zinc oxide particles and the silicon in the uncoated, free organosilicon compound. However, since the uncoated, free organosilicon compound is almost entirely washed away during processes such as washing and heating, and the amount of silicon in the uncoated, free organosilicon compound is considered to be trace amounts, it is not a problem to consider that the value obtained by the measurement method described above is approximately the same amount as the silicon in the organosilicon compound coated on the zinc oxide particles.

[0024] A dispersion having the above-mentioned ratio of (parallel light transmittance of the coating film after drying) / (parallel light transmittance of the coating film immediately after application) at a wavelength of 600 nm can be obtained by using organosilicon surface-treated zinc oxide particles as a raw material, which have particularly excellent dispersibility and whose primary particle size, as measured from transmission electron microscope images, is 0.1 μm or less.

[0025] More specifically, examples of organosilicon-coated zinc oxide particles (A) that have desirable properties for use as a raw material for a dispersion include those having the following properties:

[0026] The organosilicon-coated zinc oxide particles (A) used as raw materials for dispersion production preferably have a median diameter of 0.15 μm or less, as determined by the following method. Note that the median diameter here corresponds to median diameter 2 described later. 0.4 g of the above organosilicon-coated zinc oxide particles were placed in 200 ml of isopropyl alcohol, and a slurry was prepared by irradiating it with ultrasonic waves at 100% vibration amplitude at room temperature for 30 seconds using an ultrasonic homogenizer US-600E (manufactured by Nippon Seiki Seisakusho, rated output 600 W), and the median diameter on a volume basis was measured using a laser diffraction / scattering particle size distribution analyzer LA-960S (manufactured by Horiba, Ltd.). Furthermore, one of the characteristics of the above organosilicon-coated zinc oxide particles (A) is that they have very high dispersibility, meaning they can be sufficiently dispersed by simply applying a weak ultrasonic shock. The above median diameter is more preferably 0.13 μm or less.

[0027] In the organosilicon-coated zinc oxide particles used as a raw material for dispersion production, the ratio of the median diameter to the primary particle diameter (median diameter / primary particle diameter) is preferably 4 or less. The ratio of the median diameter to the primary particle diameter is an indicator of the degree of independence of the primary particles constituting the powder; the closer this value is to 1, the more the primary particles exist independently rather than as aggregated particles. A ratio of 3 or less is more preferable. Note that the median diameter here corresponds to median diameter 2 described later.

[0028] The organosilicon-coated zinc oxide particles used as raw materials for dispersion production are easily dispersible, but it is preferable that they exist in a moderately aggregated state when no dispersion treatment is performed. Specifically, it is preferable that the median diameter by volume of the slurry obtained by laser diffraction scattering of a slurry obtained by adding the powder to isopropyl alcohol and stirring with a homodisperser at 500 rpm for 5 seconds is 10 μm or more. That is, unless dispersion treatment is performed with a stirrer or ultrasonic waves, loosely aggregated particles are formed, and when impact is applied, the aggregated state is dissolved and the particles are dispersed to a state close to primary particles. More preferably, the diameter is 13 μm or more. In this specification, the median diameter when the material is stirred at 500 rpm for 5 seconds in the homodisperser described above is referred to as median diameter 1, and the median diameter when the material is ultrasonically dispersed for 30 seconds described above is referred to as median diameter 2.

[0029] The organosilicon-coated zinc oxide particles used as raw materials for dispersion production have a BET specific surface area of ​​25 m². 2 It is preferable that the BET specific surface area is 25 m² or less. 2 When the amount exceeds [amount] / g, the particle size decreases, making aggregation more likely. The BET specific surface area described above can be measured by the method described in the examples.

[0030] The above-mentioned organosilicon-coated zinc oxide particles (A) are not particularly limited in their manufacturing method, but examples of manufacturing methods include a step (1) of repulping the raw zinc oxide particles in a solvent containing water and an organic solvent to prepare a slurry, a step (2) of hydrolyzing an organosilicon compound in a solvent containing water and an organic solvent, and a step (3) of surface-treating the zinc oxide particles with the silane compound after hydrolysis.

[0031] Step (1) described above is a step of preparing a slurry by repulping zinc oxide particles, which are the raw material, in a solvent containing water and an organic solvent. In the manufacturing method of the present invention, preparing a slurry of zinc oxide particles in step (1) is an important step. That is, the organosilicon coating is formed in a dispersed slurry state, rather than in a dry state in which the zinc oxide particles are aggregated.

[0032] In step (1), it is preferable that the zinc oxide particles used as raw materials are synthesized in an aqueous medium and then used directly to prepare the slurry without a drying step. In other words, it is preferable that there is no drying step for the particles between the particle manufacturing step and the organosilicon coating treatment step. By doing so, aggregation between particles is suppressed, and surface treatment is not required for aggregated particles, thereby obtaining the excellent dispersion performance described above.

[0033] This process (1) ensures that each individual zinc oxide particle is surface-treated, thus efficiently imparting water repellency without the need for excessive organosilicon coating. In step (1) described above, the zinc oxide particle slurry is not limited, but preferably contains zinc oxide particles in the range of 10 to 1000 g / L.

[0034] The method for preparing the slurry is not particularly limited. For example, after filtering the zinc oxide particles obtained by the zinc oxide particle manufacturing process, they can be added to water without drying and dispersed at 5-30°C for 10-30 minutes to obtain a uniform slurry with a zinc oxide particle concentration of 10-1000 g / L.

[0035] The above-mentioned organic solvents are not particularly limited, but those described below can be used.

[0036] The above step (2) is a step (2) in which an organosilicon compound is hydrolyzed in a solvent containing water and an organic solvent.

[0037] The organic solvent used in step (2) is not particularly limited as long as it can hydrolyze the organosilicon compound, but it is preferable to use at least one selected from the group consisting of methanol, ethanol, and propanol. Using such a lower alcohol facilitates hydrolysis. More preferably, it is ethanol.

[0038] Step (2) described above is preferably carried out under conditions where the pH is 3.5 to 4.5. By carrying out the procedure under conditions where the pH is 3.5 to 4.5, the hydrolysis of the organosilicon compound can be carried out in a short time, and the self-condensation of the silane compound obtained by hydrolysis can be effectively suppressed. The pH is more preferably 3.8 to 4.2. The pH can be adjusted as appropriate using an acid or alkali.

[0039] Step (2) described above is preferably carried out with stirring. Stirring allows for more thorough hydrolysis of the organosilicon compound. The duration of the hydrolysis process is not particularly limited, but it is preferably 30 minutes or longer. Similarly, the temperature for hydrolysis is not particularly limited, but it is preferably 40°C or higher. These conditions allow for sufficient hydrolysis of the organosilicon compound while suppressing the self-condensation of the silane compound.

[0040] The stirring means in step (2) above is not particularly limited, but examples include stirring with stirring blades, shaking stirring, stirring with a mixer, stirring with a stirrer, etc.

[0041] Step (3) described above is a step in which zinc oxide particles are surface-treated with the silane compound after hydrolysis. In the surface treatment step, it is preferable to add the hydrolyzed silane compound to the slurry of zinc oxide particles obtained in step (1) and then stir it. Stirring allows the reaction of the silanol group of the hydrolyzed silane compound to proceed sufficiently, making the surface treatment more efficient. There are no particular restrictions on the stirring time, but it is preferable to stir for 60 minutes or more. Means of stirring include blenders and bead mills. There are no particular restrictions on the temperature at which the surface treatment process is performed, but it is preferable to perform it at 30 to 100°C.

[0042] Step (3) above is a step in which the silane compound solution after hydrolysis is added, and it is preferable that the amount of silane compound added is 1.0% by mass or more relative to the zinc oxide particles. If the amount added is less than 1.0% by mass, the water repellency may be insufficient. More preferably it is 1.5% by mass or more. Furthermore, it is preferable that the amount added is 10% by mass or less. If the amount added exceeds 10% by mass, the purity of the zinc oxide may decrease, and performance such as UV shielding may deteriorate. More preferably it is 8% by mass or less.

[0043] After performing the above surface treatment step, the resulting slurry is allowed to mature for 0.5 to several hours while continuing to stir, to form an organosilicon coating on the surface of the zinc oxide particles. During the aging process described above, small amounts of other components may be added, provided that they do not impair the effects of the present invention. For example, dispersants may be added.

[0044] The maturation process is preferably carried out at a temperature of 45 to 110°C. In particular, the maturation time can be 0.5 to 24 hours. Since the particle size can be adjusted by controlling conditions such as maturation temperature, maturation time, and concentration of fine zinc oxide particles, it is preferable to set these conditions appropriately according to the desired zinc oxide particles.

[0045] The organosilicon-coated zinc oxide particles obtained in this way may be subjected to post-treatment such as filtration, washing, and drying, if necessary. For example, the slurry of organosilicon-coated zinc oxide particles can be filtered to separate the organosilicon-coated zinc oxide particles, washed with water, and then dried by heating to a temperature typically in the range of 80 to 150°C to obtain the organosilicon-coated zinc oxide particles as a dried powder. It is preferable that the above-mentioned organosilicon-coated zinc oxide particles do not undergo a calcination process such as heating to 300°C or higher after surface coating. By doing so, the effects of the present invention described above can be particularly favorably obtained.

[0046] The zinc oxide particles used as the raw material are not particularly limited, but it is preferable to use those with high dispersibility, as this will also improve the dispersibility of the resulting organosilicon-coated zinc oxide particles. For example, it is preferable that the primary particle diameter is less than 0.1 μm, the aspect ratio is less than 2.5, and the oil absorption / BET specific surface area is 1.5 ml / 100 m². 2 The following are preferred: Oil absorption capacity / BET specific surface area (ml / 100m²). 2 ) is the value of oil absorption (ml / 100g), BET specific surface area (m²). 2This value is obtained by dividing by the value of ( / g), and the smaller this value, the lower the amount of oil absorbed per unit area of ​​the particle surface, meaning that there is less aggregation between particles and that the independence and dispersibility of the particles are high. Examples of such raw zinc oxide particles include those obtained by a manufacturing method that includes a step of maturing fine zinc oxide particles with a primary particle diameter of 0.005 μm or more and 0.05 μm or less in water in which a zinc salt has been dissolved. Specifically, it is preferable to use, for example, the zinc oxide particles disclosed in International Publication 2012 / 147888.

[0047] International Publication 2012 / 147888 discloses a method for obtaining zinc oxide particles with excellent dispersibility by a manufacturing method that includes a step of maturing fine-particle zinc oxide in water in which a zinc salt is dissolved. After producing zinc oxide particles in water by such a method, it is preferable to filter them and perform surface treatment by the method described above without drying. This allows surface treatment to be performed on zinc oxide particles that are in a state with little aggregation, and thus the objective of the present invention can be suitably achieved.

[0048] According to the manufacturing method described in International Publication 2012 / 147888, the primary particle size is less than 0.1 μm, the aspect ratio is less than 2.5, and the oil absorption / BET specific surface area is 1.5 ml / 100 m². 2 Zinc oxide particles can be obtained that are characterized as follows. It is particularly preferable to use such zinc oxide particles as a raw material.

[0049] The aqueous dispersion of the present invention contains a high concentration of the organosilicon-coated zinc oxide particles (A), the content of which is 60% by mass or more, and preferably 70% by mass or more, relative to the total amount of the aqueous dispersion. There is no particular upper limit, but 75% by mass is preferred.

[0050] Furthermore, although the aqueous dispersion of the present invention contains a nonionic surfactant (B) as a dispersant, the organosilicon-coated zinc oxide particles (A) have excellent dispersibility, so the content of the nonionic surfactant (B) can be 10% by mass or less relative to the organosilicon-coated zinc oxide particles (A). Since the content of the nonionic surfactant (B) is less than that of conventional products, an aqueous dispersion with a good feel can be obtained. The content of the above-mentioned nonionic surfactant (B) is more preferably 8.5% by mass or less relative to the above-mentioned organosilicon-coated zinc oxide particles (A). The lower limit is not particularly limited, but is preferably 5% by mass.

[0051] The above-mentioned nonionic surfactant (B) is not particularly limited as long as it acts as a dispersant, but examples include polyoxyalkylene alkyl ethers, polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylene castor oil, polyoxyalkylene hydrogenated castor oil, polyoxyalkylene sorbitol tetra fatty acid esters, glycerin fatty acid esters, sorbitan fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, organopolysiloxanes having polyoxyalkylene groups, organopolysiloxanes having polyglycerin groups, and organopolysiloxanes having sugar chains. The above-mentioned nonionic surfactant (B) may be used alone or in combination of two or more types.

[0052] In particular, polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan fatty acid esters, and organopolysiloxanes having polyoxyalkylene groups are preferred as nonionic surfactants (B).

[0053] Furthermore, organopolysiloxane-based nonionic surfactants as described above are most preferred. When organopolysiloxane-based nonionic surfactants are used, particularly excellent effects can be obtained in terms of the stability of the aqueous dispersion and the feel when used in cosmetics.

[0054] The HLB of such surfactants is preferably between 6 and 12. When an aqueous dispersion is prepared using only nonionic surfactants with an HLB greater than 12, if it is incorporated into an O / W formulation, the high solubility of the nonionic surfactants in water leads to poor adsorption to the powder, which can easily increase the viscosity of the formulation and impair its water resistance. Furthermore, if the HLB of the nonionic surfactant is less than 6, it becomes difficult to prepare an aqueous dispersion. In this specification, HLB is determined by the following formula defined by WCGrifinn. N HLB =(E+P) / 5 (N HLB :HLB value, E:mass % of the total dispersant molecules in the polyoxyethylene portion. P: Mass of the polyhydric alcohol portion relative to the total mass of the dispersant molecules)

[0055] The aqueous dispersion of the present invention further contains a polyhydric alcohol (C). The polyhydric alcohol (C) is preferably one or more selected from propylene glycol, butylene glycol, pentanediol, dipropylene glycol, hexanediol, heptanediol, and glycerin, with butylene glycol, pentanediol, dipropylene glycol, and hexanediol being particularly preferred. The polyhydric alcohol (C) is preferably present in the aqueous dispersion at a concentration of 5 to 25% by mass. It is believed that the inclusion of such a polyhydric alcohol (C) allows the nonionic surfactant (B) to be more uniformly oriented on the powder surface, thereby stabilizing the dispersion. More preferably, the concentration is 8 to 20% by mass.

[0056] The aqueous dispersion of the present invention contains water, and the water content is preferably 20 to 30% by mass relative to the total amount of the composition. By keeping the water content within this range, the effects described above can be suitably obtained.

[0057] The method for producing the aqueous dispersion of the present invention is not particularly limited and can be produced by mixing the above-mentioned components. The mixing method is also not limited and can be any conventional method that can uniformly disperse the components. For example, a bead mill, a jet mill, or a high-pressure homogenizer. While dispersers and devices such as the above may be used, the aqueous dispersion of the present invention does not require these expensive dispersers and devices. Because it can be easily produced with a simple agitator without the need for expensive equipment such as bead mills, It also has the advantage of eliminating the need for distributed machines.

[0058] The aqueous dispersion of the present invention may contain, as needed, antimicrobial and antiseptic agents such as alkyl parahydroxybenzoate, benzoic acid, sodium benzoate, sorbic acid, potassium sorbate, phenoxyethanol, salicylic acid, carbolic acid, sorbic acid, parachlormethacresol, hexachlorophene, benzalkonium chloride, chlorhexidine chloride, photosensitizer, and phenoxyethanol, provided that the performance of the dispersion is not impaired.

[0059] The aqueous dispersion obtained in this manner is useful as an ingredient for creating cosmetics that have an ultraviolet-blocking effect. In this case, the aqueous dispersion of the present invention may be used alone as the ultraviolet-blocking ingredient, but it may also be used in combination with an oil-based dispersion of fine inorganic powders or an organic ultraviolet absorber.

[0060] Next, the physical properties of the aqueous dispersion of the present invention will be described in detail. (viscosity) The aqueous dispersion of the present invention contains fine-particle zinc oxide at a high concentration, but exhibits low viscosity due to the inclusion of organosilicon-coated zinc oxide particles (A) which have excellent dispersibility. Specifically, the viscosity at 25°C is preferably 4,000 mPa.s or less, more preferably 1,000 mPa.s or less, and particularly preferably 100 mPa.s or less. A viscosity of 4,000 mPa.s or less is preferable because it facilitates incorporation into pharmaceutical formulations. The above viscosity can be measured by the method described in the examples.

[0061] (Median diameter) The median diameter of the organosilicon-coated zinc oxide particles (A) in the aqueous dispersion is preferably 0.15 μm or less, more preferably 0.12 μm or less, and preferably 0.01 μm or more. A median diameter of 0.15 μm or less is preferable because it provides high visible light transparency and a suitable ultraviolet shielding region. In this specification, the median diameter of the organosilicon-coated zinc oxide particles (A) in the aqueous dispersion is denoted as median diameter 3. The median diameter 3 can be measured by the method described in the examples.

[0062] The aqueous dispersion of the present invention is not particularly limited in its use, but can be suitably used in applications such as cosmetics and paints. Such cosmetics are also one example of the present invention.

[0063] Cosmetics containing the aqueous dispersion of the present invention exhibit excellent dispersibility and stability, as well as good handling properties.

[0064] Examples of cosmetics of the present invention include foundations, makeup bases, eyeshadows, blushes, mascaras, lipsticks, sunscreens, skincare products, and hair products. Among these, it is particularly suitable for use in sunscreens. Furthermore, the cosmetic composition of the present invention can be in any form of oil-based cosmetic composition, aqueous cosmetic composition, O / W type cosmetic composition, or W / O type cosmetic composition, but the O / W type cosmetic composition is particularly preferred. Furthermore, there are no particular limitations on the product form, but it can be applied to liquid, emulsion, cream, solid, paste, gel, multilayer, mousse, spray, etc.

[0065] The cosmetic composition of the present invention may contain, in addition to the components constituting the above mixture, any aqueous and oily components that can be used in the field of cosmetics. The above aqueous and oily components are not particularly limited and may contain, for example, oils, surfactants, humectants, higher alcohols, metal ion chelating agents, natural and synthetic polymers, water-soluble and oil-soluble polymers, UV shielding agents, various extracts, inorganic and organic pigments, various powders such as inorganic and organic clay minerals or inorganic and organic pigments treated with metal soap or silicone, colorants such as organic dyes, preservatives, antioxidants, dyes, pH adjusters, fragrances, cooling agents, antiperspirants, bactericides, skin activators, and other components. Specifically, it is possible to manufacture the desired cosmetic composition by conventional methods by arbitrarily blending one or more of the following listed components. The amount of these components blended is not particularly limited as long as it does not impair the effects of the present invention.

[0066] The above oils are not particularly limited and include, for example, avocado oil, camellia oil, turtle oil, macadamia nut oil, corn oil, mink oil, olive oil, rapeseed oil, egg yolk oil, sesame oil, peach kernel oil, wheat germ oil, sasanqua oil, castor oil, linseed oil, safflower oil, cottonseed oil, henbit oil, soybean oil, peanut oil, tea seed oil, kaya oil, rice bran oil, cinnamon oil, Japanese tung oil, jojoba oil, wheat germ oil, triglycerin, glyceryl trioctanoate, glyceryl triisopalmitate, cocoa butter, coconut oil, horse fat, hydrogenated coconut oil, palm oil, beef tallow, sheep fat, hydrogenated beef tallow, palm kernel oil, pork fat, beef bone fat, Japanese wax kernel oil, hydrogenated oil, beef tallow, Japanese wax, hydrogenated castor oil, beeswax, candelilla oil Examples of waxes include cotton wax, carnauba wax, bayberry wax, privet wax, whale wax, montane wax, rice bran wax, lanolin, kapok wax, lanolin acetate, liquid lanolin, sugarcane wax, isopropyl lanolin fatty acid, hexyl laurate, reduced lanolin, jojoba wax, hard lanolin, shellac wax, POE lanolin alcohol ether, POE lanolin alcohol acetate, POE cholesterol ether, lanolin fatty acid polyethylene glycol, POE hydrogenated lanolin alcohol ether, liquid paraffin, ozokerite, pristane, paraffin, ceresin, squalene, petrolatum, and microcrystalline wax.

[0067] The above-mentioned lipophilic nonionic surfactants are not particularly limited, and examples include sorbitan fatty acid esters such as sorbitan monooleate, sorbitan monoisostearate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan sesquioleate, sorbitan trioleate, sorbitan diglycerol sorbitan penta-2-ethylhexylate, and sorbitan diglycerol sorbitan tetra-2-ethylhexylate; glycerin polyglycerin fatty acids such as monocottonseed oil fatty acid glycerin, monoerucate glycerin, sesquioleate glycerin, monostearate glycerin, α,α'-oleate pyroglutamate glycerin, and monostearate glycerin malic acid; propylene glycol fatty acid esters such as monostearate propylene glycol; hydrogenated castor oil derivatives; and glycerin alkyl ethers.

[0068] The hydrophilic nonionic surfactant is not particularly limited, and examples include POE sorbitan fatty acid esters such as POE sorbitan monostearate, POE sorbitan monooleate, POE sorbitan tetraoleate, etc., POE sorbitan fatty acid esters such as POE sorbitan monolaurate, POE sorbitan monooleate, POE sorbitan pentaoleate, POE sorbitan monostearate, etc., POE glycerin monostearate, POE glycerin monoisostearate, POE glycerin triisostearate, etc. POE fatty acid esters such as ricerin fatty acid esters, POE monooleate, POE distearate, POE monodioleate, ethylene glycol distearate, POE alkyl ethers such as POE lauryl ether, POE oleyl ether, POE stearyl ether, POE behenyl ether, POE 2-octyldodecyl ether, POE cholestanol ether, POE alkylphenyl ethers such as POE octylphenyl ether, POE nonylphenyl ether, POE dinonylphenyl ether, and brulonine POE-POP alkyl ethers such as POE-POP cetyl ether, POE-POP 2-decyltetradecyl ether, POE-POP monobutyl ether, POE-POP hydrogenated lanolin, POE-POP glycerin ether, tetra-POE-tetraPOP ethylenediamine condensates such as TETRON, POE castor oil, POE hydrogenated castor oil, POE hydrogenated castor oil monoisostearate, POE hydrogenated castor oil triisostearate, POE hydrogenated castor oil monopyroglutamic acid monoisostearate Examples include sterols, POE hydrogenated castor oil derivatives such as POE hydrogenated castor oil maleic acid, POE beeswax / lanolin derivatives such as POE sorbitan beeswax, alkanolamides such as coconut oil fatty acid diethanolamide, lauric acid monoethanolamide, and fatty acid isopropanolamide, POE propylene glycol fatty acid esters, POE alkylamines, POE fatty acid amides, sucrose fatty acid esters, POE nonylphenylformaldehyde condensate, alkylethoxydimethylamine oxide, and trioleyl phosphate.

[0069] Other surfactants may be included, for example, anionic surfactants such as fatty acid soaps, higher alkyl sulfate esters, POE lauryl sulfate triethanolamine, and alkyl ether sulfate esters; cationic surfactants such as alkyltrimethylammonium salts, alkylpyridinium salts, alkylquaternary ammonium salts, alkyldimethylbenzylammonium salts, POE alkylamines, alkylamine salts, and polyamine fatty acid derivatives; and amphoteric surfactants such as imidazoline-based amphoteric surfactants and betaine-based surfactants, within a range that does not pose problems in terms of stability and skin irritation.

[0070] The above-mentioned moisturizers are not particularly limited and include, for example, xylitol, sorbitol, maltitol, chondroitin sulfate, hyaluronic acid, mucoitin sulfate, carotenoid acid, atelocollagen, cholesteryl-12-hydroxystearate, sodium lactate, bile salts, dl-pyrrolidone carboxylate, short-chain soluble collagen, diglycerin (EO)PO adduct, rose extract, quince extract, sweet clover extract, and the like.

[0071] The above-mentioned higher alcohols are not particularly limited, and examples include linear alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, myristyl alcohol, oleyl alcohol, and cetostearyl alcohol, as well as branched alcohols such as monostearyl glycerol ether (batyl alcohol), 2-decyltetradecinol, lanolin alcohol, cholesterol, phytosterol, hexyldodecanol, isostearyl alcohol, and octyldodecanol.

[0072] The metal ion chelating agent is not particularly limited, and examples include 1-hydroxyethane-1,1-diphosphonic acid, tetrasodium 1-hydroxyethane-1,1-diphosphonic acid, sodium citrate, sodium polyphosphate, sodium metaphosphate, gluconic acid, phosphoric acid, citric acid, ascorbic acid, succinic acid, EDTA, and the like.

[0073] The above-mentioned natural water-soluble polymers are not particularly limited and include, for example, plant-derived polymers such as Arabia gum, Tragacanth gum, Galactan, Guar gum, Carob gum, Karaya gum, Carrageenan, Pectin, Agar, Quince seed (Quince), Algae colloid (Cassia extract), Starch (Rice, Corn, Potato, Wheat), and Glycyrrhizic acid; microbial polymers such as Xanthan gum, Dextran, Succinoglucan, and Pullulan; and animal-derived polymers such as Collagen, Casein, Albumin, and Gelatin.

[0074] The semi-synthetic water-soluble polymers are not particularly limited and include, for example, starch-based polymers such as carboxymethyl starch and methylhydroxypropyl starch; cellulose-based polymers such as methylcellulose, nitrocellulose, ethylcellulose, methylhydroxypropylcellulose, hydroxyethylcellulose, sodium cellulose sulfate, hydroxypropylcellulose, sodium carboxymethylcellulose (CMC), crystalline cellulose, and cellulose powder; and alginate-based polymers such as sodium alginate and propylene glycol alginate ester.

[0075] The water-soluble polymers used in synthesis are not particularly limited and include, for example, vinyl polymers such as polyvinyl alcohol, polyvinyl methyl ether, and polyvinylpyrrolidone; polyoxyethylene polymers such as polyethylene glycol 20,000, 40,000, and 60,000; polyoxyethylene polyoxypropylene copolymer polymers; acrylic polymers such as sodium polyacrylate, polyethyl acrylate, and polyacrylamide; polyethyleneimine; and cationic polymers.

[0076] The inorganic water-soluble polymer is not particularly limited, and examples include bentonite, magnesium aluminum silicate (bee gum), laponite, hectorite, and anhydrous silicic acid.

[0077] The oil-soluble polymer is not particularly limited, and examples include disteardimonium hectorite, dextrin palmitate, dextrin myristate, (palmitic acid / ethylhexanoic acid) dextrin, (palmitic acid / hexyldecanoic acid) dextrin, and inulin stearate.

[0078] The UV shielding agent is not particularly limited and includes, for example, benzoic acid-based UV shielding agents such as para-aminobenzoic acid (hereinafter abbreviated as PABA), PABA monoglycerol ester, N,N-dipropoxy PABA ethyl ester, N,N-diethoxy PABA ethyl ester, N,N-dimethyl PABA ethyl ester, N,N-dimethyl PABA butyl ester, etc.; anthranilic acid-based UV shielding agents such as homomenthyl-N-acetylanthranilate; amyl salicylate, menthyl salicylate, Salicylic acid-based UV shielding agents such as homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, p-isopropanolphenyl salicylate; octyl cinnamate, ethyl-4-isopropyl cinnamate, methyl-2,5-diisopropyl cinnamate, ethyl-2,4-diisopropyl cinnamate, methyl-2,4-diisopropyl cinnamate, propyl-p-methoxy cinnamate, isopropyl-p-methoxy cinnamate, Cinnamic acid-based UV shielding agents such as isoamyl-p-methoxycinnamate, 2-ethoxyethyl-p-methoxycinnamate, cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenylcinnamate, 2-ethylhexyl-α-cyano-β-phenylcinnamate, glyceryl mono-2-ethylhexanoyl-diparamethoxycinnamate; 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydro Benzophenone-based UV shielding agents such as xy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-4'-methylbenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonate, 4-phenylbenzophenone, 2-ethylhexyl-4'-phenylbenzophenone-2-carboxylate, 2-hydroxy-4-n-octoxybenzophenone, and 4-hydroxy-3-carboxybenzophenone;Examples include 3-(4'-methylbenzylidene)-d,l-camphor, 3-benzylidene-d,l-camphor, urocanic acid, ethyl urocanic acid, 2-phenyl-5-methylbenzoxazole, 2,2'-hydroxy-5-methylphenylbenzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenylbenzotriazole), dibenzarazine, dianisioylmethane, 4-methoxy-4'-t-butyldibenzoylmethane, 5-(3,3-dimethyl-2-norbornylidene)-3-pentan-2-one, etc.

[0079] Other drug components are not particularly limited and may include, for example, vitamins such as vitamin A oil, retinol, retinyl palmitate, inositol, pyridoxine hydrochloride, benzyl nicotinate, nicotinamide, DL-α-tocopherol nicotinate, magnesium ascorbate phosphate, 2-O-α-D-glucopyranosyl-L-ascorbic acid, vitamin D2 (ergocasciferol), dl-α-tocopherol, dl-α-tocopherol acetate, pantothenic acid, and biotin; hormones such as estradiol and ethinylestradiol; amino acids such as arginine, aspartic acid, cystine, cysteine, methionine, serine, leucine, and tryptophan; anti-inflammatory agents such as allantoin and azulene, whitening agents such as arbutin; astringents such as tannic acid; cooling agents such as L-menthol and camphor, as well as sulfur, lysozyme chloride, and pyridoxine chloride.

[0080] The types of extracts are not particularly limited, and examples include Houttuynia cordata extract, Phellodendron amurense extract, Melilotus extract, Lamium album extract, Licorice extract, Peony extract, Soapwort extract, Luffa gourd extract, Cinchona extract, Saxifraga stolonifera extract, Sophora flavescens extract, Nuphar japonica extract, Fennel extract, Primrose extract, Rose extract, Rehmannia glutinosa extract, Lemon extract, Lithospermum erythrorhizon extract, Aloe vera extract, Calamus root extract, Eucalyptus extract, Horsetail extract, Sage extract, Thyme extract, Tea extract, Seaweed extract, Cucumber extract, Clove extract, Raspberry extract, Melissa extract, Carrot extract, Horse chestnut extract, Peach extract, Peach leaf extract, Mulberry extract, Cornflower extract, Witch hazel extract, Placenta extract, Thymus extract, Silk extract, Licorice extract, etc.

[0081] Examples of the various powders mentioned above include lustrous coloring pigments such as red iron oxide, yellow iron oxide, black iron oxide, titanium mica, iron oxide-coated titanium mica, and titanium oxide-coated glass flakes; inorganic powders such as mica, talc, kaolin, sericite, titanium dioxide, and silica; and organic powders such as polyethylene powder, nylon powder, cross-linked polystyrene, cellulose powder, and silicone powder. Preferably, in order to improve functional properties and cosmetic durability, some or all of the powder components are hydrophobized using known methods with substances such as silicones, fluorine compounds, metal soaps, oils, and acyl glutamates. Alternatively, other zinc oxide particles not applicable to the present invention may be mixed and used.

[0082] In addition to the cosmetics described above, the aqueous dispersion of the present invention can also be used in fields such as heat dissipation compositions, rubber vulcanization accelerators, pigments for paints and inks, electronic components such as ferrites and varistors, and pharmaceuticals. [Examples]

[0083] The present invention will be described below with reference to examples, but the present invention is not limited in any way by these examples. In the examples, "%" in the blending ratios means "mass%" unless otherwise specified.

[0084] (Example of manufacturing raw zinc oxide cake) 80g of FINEX-50 (manufactured by Sakai Chemical Industry Co., Ltd., primary particle size 0.020μm) was repulped into 1200ml of zinc acetate aqueous solution with a zinc acetate concentration of 0.135mol / l to obtain a slurry. The slurry was then heated to 70°C for 42 minutes while stirring, and aged at 70°C for 2 hours while stirring. After aging, it was filtered and washed with water. The resulting solid was then repulped into 3 liters of water to obtain a slurry, heated to 95°C while stirring, and heated and washed at 95°C for 60 minutes while stirring. After heating and washing, it was filtered and washed with water to obtain a zinc oxide cake.

[0085] (Manufacturing Example 1) The cake obtained in the production example was repulped into an ethanol aqueous solution prepared by mixing 200 ml of ethanol and 65 ml of pure water to obtain a 44% ethanol concentration slurry. 20 ml of the 44% ethanol aqueous solution was adjusted to pH 4 with acetic acid, and 2.0 g of octyltriethoxysilane (Shin-Etsu Chemical Co., Ltd. KBE-3083) (2.5% relative to zinc oxide) was added. The mixture was stirred at 80°C for 2 hours to obtain octyltriethoxysilane hydrolysate. The 44% ethanol aqueous solution slurry was heated to 50°C, the octyltriethoxysilane hydrolysate was added, and the mixture was aged at 50°C for 2 hours. After aging, the mixture was filtered, washed with water, and dried at 120°C for 16 hours to obtain octyltriethoxysilane-coated zinc oxide particles with a primary particle size of 0.061 μm.

[0086] (Manufacturing example 2) As in Production Example 1, heating, filtration, and water washing were performed, and the resulting solid was dried in a dryer at 120°C for 16 hours to obtain dried zinc oxide. The obtained dried material was ground in a coffee mill to obtain zinc oxide powder. The obtained zinc oxide powder was placed in a plastic bag, 2.4 g of octyltriethoxysilane (3% relative to zinc oxide) was added and mixed, and the mixture was heat-treated in a dryer at 120°C for 16 hours to obtain octyltriethoxysilane-coated zinc oxide particles.

[0087] The size and morphology of octyltriethoxysilane-coated zinc oxide particles and organosilicon-surface-coated zinc oxide particles A-C obtained in Production Example 1 and Production Example 2 were observed using a transmission electron microscope (TEM, JEM-1200EX II, JEOL Ltd.). The physical properties of the obtained particles are shown in Table 1.

[0088] (Examples 1-3) Aqueous dispersions with the compositions shown in Table 2 were prepared by the following manufacturing method. The physical properties of the obtained aqueous dispersions and the coating films were evaluated, and the results are shown in Table 2. The raw materials used in Table 2 are as follows: PEG-9 Dimethicone: KF-6013 (manufactured by Shin-Etsu Chemical Co., Ltd.) PEG-10 Dimethicone: KF-6943 (manufactured by Shin-Etsu Chemical Co., Ltd.)

[0089] (Manufacturing method) Components 6 and 7, components 8 and 9, components 1 through 5, and component 10 were added to the beaker in that order, mixing with a metal spatula each time. The mixture was then stirred with a stirrer at 500 rpm for 15 minutes to obtain an aqueous dispersion of zinc oxide fine particles with an organosilicon compound surface treatment.

[0090] (Comparative Example 1) An aqueous dispersion was prepared in the same manner as in Example 1, except that component (A) was changed to organosilicon-coated zinc oxide particles obtained in Production Example 2.

[0091] (Comparative Example 2) An aqueous dispersion was prepared in the same manner as in Example 1, except that component (A) was changed to organosilicon-coated zinc oxide particles A.

[0092] (Comparative Example 3) An aqueous dispersion was prepared in the same manner as in Example 1, except that component (A) was changed to organosilicon-coated zinc oxide particles B.

[0093] (Comparative Example 4) An aqueous dispersion was prepared in the same manner as in Example 1, except that component (A) was changed to organosilicon-coated zinc oxide particles C.

[0094] The physical properties of component (A) were measured by the following method. (Evaluation method 1) Primary particle size For the particles of component (A), the particle size (μm) defined by the fixed-direction diameter (the distance between two parallel lines in a fixed direction sandwiching the particle; measured in a fixed direction for any shaped particles in the image) in the field of view 2000 - 50000 times that of the photo taken with a transmission electron microscope JEM-1200EX II (manufactured by JEOL Ltd., rated output 600W) was measured. The fixed-direction diameters of 250 primary particles in the TEM photo were measured, and the average value of their cumulative distribution was obtained.

[0095] (Evaluation method 2) BET specific surface area The BET specific surface area (m 2 / g) was measured by a fully automatic BET specific surface area measuring device Macsorb Model HM-1200 (manufactured by Mountech Co., Ltd.).

[0096] (Evaluation method 3) Silicon content The powder formed by a press machine was measured by semi-quantitative analysis by the FP method using a fluorescent X-ray analyzer (PRIMUSII manufactured by Rigaku Corporation).

[0097] (Evaluation method 4) Median diameter 1, Median diameter 2 Median diameter 1 and Median diameter 2 were measured by a laser diffraction / scattering particle size distribution measuring device LA-960S (manufactured by Horiba, Ltd.). 0.4 g of zinc oxide particles in the examples and comparative examples were put into 200 ml of isopropyl alcohol. For Median diameter 1, the slurry kneaded with a medicine spoon was measured, and for Median diameter 2, the slurry ultrasonically dispersed for 30 seconds using an ultrasonic homogenizer US-600E (manufactured by Nihon Seiki Seisakusho Co., Ltd.) was measured. The refractive index of zinc oxide in the examples and comparative examples was set to 2.00, and the refractive index of isopropyl alcohol was set to 1.378, and the measurement was made on a volume basis. Median diameter 1 represents the size of the particles as they are, and Median diameter 2 represents the size of the particles during weak dispersion.

[0098]

Table 1

[0099] The physical properties of the obtained aqueous dispersion and the coating film were evaluated using the following methods. (Evaluation method 5) Initial viscosity After dispersion, the dispersion was placed in a 9 ml screw-top bottle, and the viscosity (at 25°C) was measured 60 seconds after the start of rotation at 12 rpm using a Type B viscometer (Tokyo Keiki Co., Ltd.) with rotor No. 4.

[0100] (Evaluation method 6) Viscosity over time at 40°C The dispersion was placed in a 9 ml screw-top bottle and stored in a 40°C constant temperature bath for 7 days. The viscosity was measured 60 seconds after the start of rotation at 12 rpm using a Type B viscometer (Tokyo Keiki Co., Ltd.) with rotor No. 4.

[0101] (Evaluation method 7) Median diameter 3 After diluting the obtained aqueous dispersion with water, the median diameter D50 based on volume was measured using a laser diffraction / scattering particle size distribution analyzer LA-960S (manufactured by Horiba, Ltd.).

[0102] (Creation of coating film) A small amount of the aqueous dispersion was dropped onto a glass slide (length x width x thickness = 76 mm x 26 mm x 0.8-1.0 mm, manufactured by Matsunami Glass Industry Co., Ltd.) at room temperature, and a coating film 1 with a wet film thickness of 22.90 μm was prepared using a bar coater (No. 579 ROD No. 10, manufactured by Yasuda Seiki Seisakusho Co., Ltd.). Furthermore, coating film 1 was dried at 50°C for 2 hours to obtain coating film 2. The prepared coating film 1 was used to measure parallel light transmittance 1, and coating film 2 was used to measure parallel light transmittance 2, whiteness, unevenness, and gloss (20° gloss).

[0103] (Evaluation Method 8) Parallel Light Transmittance The parallel light transmittance values ​​1 (%) and 2 (%) are the values ​​obtained by measuring the prepared coating films 1 and 2 with a spectrophotometer V-770 (manufactured by JASCO Corporation). Note that the values ​​for parallel light transmittance 1 (%) and 2 (%) are the parallel light transmittance values ​​at a wavelength of 600 nm. A higher value for parallel light transmittance 1 (%) and 2 (%) (%) indicates higher visible light transparency, and a higher ratio of parallel light transmittance 2 to parallel light transmittance 1 indicates less drying aggregation and suppression of whitening.

[0104] (Evaluation method 9) White cast The change in whiteness between coating film 1 and coating film 2 was observed visually and evaluated according to the following criteria. ○: Coating 1 is whiter than coating 2, or coating 1 and coating 2 are approximately the same whiteness. △: Coating 2 is slightly whiter than coating 1. ×: Coating 2 is whiter than coating 1.

[0105] (Evaluation method 10) Unevenness of the coating film after drying When coating film 2 was observed using an industrial microscope ECLIPSE LV100ND (manufactured by Nikon), aggregates larger than 2 μm observed within a 100 μm × 100 μm area were evaluated according to the following criteria. 〇: 30 pieces or less ×: More than 30

[0106] (Evaluation Method 11) Gloss (20° Gloss) In this specification, the gloss (20° gloss) of the coating film is the value measured by coating film 2 using a GLOSS METER VG7000 (manufactured by Murakami Color Technology Laboratory Co., Ltd.), and is the gloss value at an incident angle of 20°. A higher gloss (20° gloss) value means that there is less aggregation of zinc oxide particles inside the created coating film and that the dispersion is high, resulting in less drying aggregation and fewer irregularities.

[0107] [Table 2]

[0108] The aqueous dispersion in the example demonstrated high concentration and low viscosity, and showed no significant change in viscosity even after storage at 40°C for one week, indicating excellent stability. Furthermore, the ratio of parallel light transmittance 2 to parallel light transmittance 1 was higher than in the comparative example, demonstrating suppression of white cast. The surface texture and gloss of the coating after drying are excellent, clearly indicating that adhesion after drying is suppressed.

[0109] (Example 4, Comparative Examples 5, 6, 7) Using the zinc oxide aqueous dispersions obtained from Example 1 and Comparative Examples 1, 2, and 3, sunscreen O / W creams with the compositions shown below were prepared for Example 4 and Comparative Examples 5, 6, and 7, and their quality was evaluated.

[0110] [Table 3] (Note 4) (Sodium acrylate / sodium acryloyldimethyl taurate) copolymer: SIMULGEL EG (manufactured by SEPPIC) (Note 5) Plant-derived cellulose: RHEOCRYSTA C-2SP (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

[0111] (Manufacturing method) A: Mix ingredients 1-6 and heat. B: Mix and dissolve ingredients 7-12 until uniform. C:A was added to B and emulsified, and after cooling, component 13 was added to obtain the respective sunscreen O / W creams (Example 4, Comparative Examples 5-7).

[0112] (Evaluation method) (in vitro SPF, in vitro UVAPF) Each sample was coated onto a glass slide (length x width x thickness = 76 mm x 26 mm x 0.8-1.0 mm, manufactured by Matsunami Glass Industry Co., Ltd.) using a bar coater (No. 579 ROD No. 6, manufactured by Yasuda Seiki Seisakusho Co., Ltd.), and the transmittance was measured using a spectrophotometer V-770 (manufactured by JASCO Corporation) to obtain in vitro SPF values ​​and in vitro UVAPF values.

[0113] (stickiness) A user test was conducted by a panel of 20 experts. The oil-in-water emulsion sunscreen cosmetic of the example was applied to the skin, and its non-greasy feel was evaluated. The evaluation was based on the following criteria. [Evaluation Criteria] Very good: 5 points Good: 4 points Average: 3 points Slightly poor: 2 points Defective: 1 point [judgement ] Average score 4.5 or higher:◎ Average score of 3.5 or higher but less than 4.5: ○ Average score between 2.5 and 3.5 points: △ Average score below 2.5 points: ×

[0114] (creak) A user test was conducted by a panel of 20 experts. The oil-in-water emulsion sunscreen cosmetic of the example was applied to the skin, and the lack of stickiness was evaluated. The evaluation was based on the following criteria. [Evaluation Criteria] Very good: 5 points Good: 4 points Average: 3 points Slightly poor: 2 points Defective: 1 point [judgement ] Average score 4.5 or higher:◎ Average score of 3.5 or higher but less than 4.5: ○ Average score between 2.5 and 3.5 points: △ Average score below 2.5 points: ×

[0115] [Table 4]

[0116] The O / W cream obtained in Example 4 was stable and did not change over time, did not leave a white cast, and in terms of usability, it spread more easily and smoothly on the skin when applied compared to Comparative Examples 5 and 6, and did not feel powdery or sticky when applied compared to Comparative Example 7, making it an O / W cream with a superior feel. Furthermore, the O / W cream obtained in Example 4 showed superior in vitro SPF and in vitro UVAPF values ​​compared to the comparative example.

[0117] Example 5 (Sunscreen O / W Cream) Using the ingredients shown in Table 5 below, an O / W sunscreen cream was obtained by the following manufacturing method. (Manufacturing method) A: Mix ingredients 1-6 uniformly and heat until dissolved. B: Mix ingredients 7-15 uniformly and heat. A was added to C:B and emulsified, then cooled to obtain an O / W sunscreen cream.

[0118] [Table 5] (Note 6) Silicone tertiary crosslinked material: 9040 Silicone Elastomer Blend (manufactured by Dow-Toray) (Note 7) Hydroxyethyl acrylate / sodium acryloyldimethyl taurate copolymer: SIMULGEL NS (manufactured by SEPPIC) (Note 8) Alkyl acrylate copolymer: DERMACRYL AQF (manufactured by Nurion Japan Co., Ltd.) (Note 9) Water-repellent titanium dioxide aqueous dispersion of fine particles: DIS-AB-10W (manufactured by Sakai Chemical Industry Co., Ltd.)

[0119] The sunscreen O / W cream of Example 5 obtained as described above was stable without undergoing changes over time despite being a mixed dispersion of zinc oxide and titanium dioxide. Furthermore, in terms of usability, it spread smoothly on the skin upon application, without any stickiness or tightness after application, was highly transparent, did not leave a white cast, and was an organic UV absorber-free sunscreen O / W cream with excellent long-lasting sunscreen effect.

[0120] Example 6 (Sunscreen O / W Cream) Using the ingredients shown in Table 6 below, an O / W sunscreen cream was obtained by the following manufacturing method. (Manufacturing method) A: Mix ingredients 1-7 uniformly and heat until dissolved. B: Mix ingredients 8-16 uniformly and heat. C:B was emulsified by adding A and then cooled to obtain sunscreen O / W cream.

[0121] [Table 6] (Note 10) Hydrophilic fine particle titanium dioxide aqueous dispersion: GT-10W2 (manufactured by Sakai Chemical Industry Co., Ltd.)

[0122] The sunscreen O / W cream of Example 6 obtained as described above was stable without undergoing changes over time, and in terms of usability, it spread smoothly on the skin when applied, without any stickiness or tightness after application, was highly transparent, did not leave a white cast, and was an organic UV absorber-free sunscreen O / W cream with excellent long-lasting sunscreen effect.

[0123] Example 7 (Sunscreen O / W Cream) Using the ingredients shown in Table 7 below, an O / W sunscreen cream was obtained by the following manufacturing method. (Manufacturing method) A: Mix ingredients 1-8 uniformly and heat until dissolved. B: Mix ingredients 9-16 uniformly and heat. A was added to C:B and emulsified, then cooled to obtain an O / W sunscreen cream.

[0124] [Table 7] (Note 11) Water-repellent fine particle titanium dioxide oil dispersion: DIS-TL-10A (manufactured by Sakai Chemical Industry Co., Ltd.)

[0125] The sunscreen O / W cream of Example 7 obtained as described above was stable without undergoing changes over time, and in terms of usability, it spread smoothly on the skin when applied, without any stickiness or tightness after application, was highly transparent, did not leave a white cast, and was a sunscreen O / W cream with excellent sun protection duration and water resistance.

[0126] Example 8 (O / W Liquid Foundation) Using the ingredients shown in Table 8 below, an O / W liquid foundation was obtained by the following manufacturing method. (Manufacturing method) A: Mix ingredients 1-8 uniformly and heat until dissolved. B: Mix components 14-17 uniformly with a portion of component 19. C: Mix the remaining components 9-12, 18, and 19 uniformly and heat. A was added to D:C and emulsified, and after cooling, B and 13 were added and mixed uniformly to obtain an O / W liquid foundation.

[0127] [Table 8] (Note 12) Anionic polymer thickener (2% aq): Aristoflex AVC (manufactured by Clariant Japan Co., Ltd.) (Note 13) Water-repellent titanium dioxide liquid dispersion: DIP-T1(N) (manufactured by Sakai Chemical Industry Co., Ltd.) (Note 14) Water-repellent iron oxide (yellow) liquid dispersion: DIP-Y1(N) (manufactured by Sakai Chemical Industry Co., Ltd.) (Note 15) Water-repellent iron oxide (red) liquid dispersion: DIP-R1(N) (manufactured by Sakai Chemical Industry Co., Ltd.) (Note 16) Water-repellent iron oxide (black) liquid dispersion: DIP-K1(N) (manufactured by Sakai Chemical Industry Co., Ltd.) (Note 17) Plate-shaped barium sulfate: H-LFM (manufactured by Sakai Chemical Industry Co., Ltd.)

[0128] The O / W liquid foundation of Example 8 obtained as described above was stable without undergoing changes over time, and in terms of usability, it spread smoothly and evenly on the skin upon application, stayed put well, and did not leave any sticky or tight feeling on the skin afterward. It was an O / W liquid foundation with excellent UV protection and long-lasting wear.

[0129] Example 9 (Sunscreen with / with milk) Using the ingredients shown in Table 9 below, sunscreen W / O milk was obtained by the following manufacturing method. (Manufacturing method) A: Mix ingredients 1-9 uniformly. B: Mix ingredients 10-14 uniformly. C:B was added to A and emulsified to obtain sunscreen water-free milk.

[0130] [Table 9] (Note 18) PEG-10 Dimethicone: KF-6017 (manufactured by Shin-Etsu Chemical Co., Ltd.) (Note 19) Titanium dioxide silicone dispersion: DIS-11A (manufactured by Sakai Chemical Industry Co., Ltd.) (Note 20) Barium sulfate: Barimaru (manufactured by Sakai Chemical Industry Co., Ltd.)

[0131] The sunscreen W / O milk of Example 9 obtained as described above was stable without undergoing changes over time, and in terms of usability, it spread well and smoothly on the skin when applied, without any stickiness or tightness on the skin afterward, had a soft-focus effect without leaving a white cast, and was a sunscreen W / O milk with excellent sun protection duration and water resistance.

[0132] Example 10 (Sunscreen with O-Milk) Using the ingredients shown in Table 10 below, sunscreen W / O milk was obtained by the following manufacturing method. (Manufacturing method) A: Mix ingredients 1-10 uniformly. B: Mix ingredients 11-15 uniformly. C: Add B to A and emulsify to obtain sunscreen water-free milk.

[0133] [Table 10] (Note 21) Lauryl PEG-10 Tris(trimethylsiloxy)silylethyl dimethicone: ES-5300 (manufactured by Dow-Toray) (Note 22) Calcium carbonate: Karumaru SMS-M5 (manufactured by Sakai Chemical Industry Co., Ltd.)

[0134] The sunscreen W / O milk of Example 10 obtained as described above was stable without undergoing changes over time, and in terms of usability, it spread smoothly on the skin when applied, without any stickiness or tightness on the skin afterward, was highly transparent, did not leave a white cast, and was a sunscreen W / O milk with excellent sun protection duration and water resistance.

[0135] Example 11 (W / O liquid foundation) Using the ingredients shown in Table 11 below, a W / O liquid foundation was obtained by the following manufacturing method. (Manufacturing method) A: Mix ingredients 1-11 uniformly. B: Mix components 15-18 uniformly with a portion of component 20. C: Mix components 12-14, 19, 20 and B uniformly. D:A was emulsified with C to obtain a water-free liquid foundation.

[0136] [Table 11] (Note 23) Plate-shaped aggregated spherical zinc oxide: CANDY ZINC1000 (manufactured by Sakai Chemical Industry Co., Ltd.)

[0137] The W / O liquid foundation of Example 11 obtained as described above was stable without undergoing changes over time, and in terms of usability, it spread smoothly and evenly on the skin upon application, stayed put well, did not leave any stickiness or tightness on the skin afterward, had an oil-absorbing effect, and was a W / O liquid foundation with excellent makeup-holding effect and water resistance. [Industrial applicability]

[0138] The aqueous dispersion of the present invention can be suitably used as an ingredient in cosmetics.

Claims

1. An aqueous dispersion comprising organosilicon-coated zinc oxide particles (A), a nonionic surfactant (B), a polyhydric alcohol (C), and water (D), The organosilicon-coated zinc oxide particles (A) have a primary particle diameter of 0.1 μm or less as measured from transmission electron microscope images, and the median diameter by volume of the dispersion obtained by dispersing them in isopropyl alcohol and irradiating them with ultrasonic waves at a rated output of 600 W and vibration amplitude of 100% at room temperature for 30 seconds using an ultrasonic homogenizer is 0.15 μm or less as measured by laser diffraction scattering. The content of the organosilicon-coated zinc oxide particles (A) is 60% by mass or more relative to the total amount of the aqueous dispersion. The ratio of (parallel light transmittance of the coating film after drying) / (parallel light transmittance of the coating film immediately after application) at a wavelength of 600 nm is 0.8 or higher. The dried coating film is obtained by applying an aqueous dispersion containing 60% by mass of the organosilicon surface-coated zinc oxide particles (A) at room temperature and then drying it at 50°C for 2 hours. The coating immediately after application is formed within 5 minutes after application at room temperature of an aqueous dispersion containing 60% by mass of the organosilicon-coated zinc oxide particles (A). Aqueous dispersion characterized by the following features.

2. The aqueous dispersion according to claim 1, wherein the content of the nonionic surfactant (B) is 8.5% by mass or less based on 100% by mass of organosilicon-coated zinc oxide particles (A).

3. The aqueous dispersion according to claim 1 or 2, wherein the organosilicon-coated zinc oxide particles (A) have a median diameter of 0.15 μm or less in the aqueous dispersion.

4. The aqueous dispersion according to any one of claims 1 to 3, wherein the viscosity at 25°C is 4,000 mPa·s or less.

5. An aqueous dispersion according to any one of claims 1 to 4, wherein, when the dried coating film is observed with an interference microscope, there are 30 or fewer aggregates of 2 μm or more in a 100 μm × 100 μm field of view, and the gloss (20° gloss) is 80 or more.

6. The aqueous dispersion according to any one of claims 1 to 5, wherein the nonionic surfactant (B) is an organopolysiloxane-based nonionic surfactant.

7. The aqueous dispersion according to any one of claims 1 to 6, wherein the polyhydric alcohol (C) is one or more polyhydric alcohols selected from the group consisting of propylene glycol, butylene glycol, pentanediol, dipropylene glycol, hexanediol, heptanediol, and glycerin.

8. A cosmetic composition characterized by containing the aqueous dispersion described in any one of claims 1 to 7.

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