Decorative aqueous composition and method for producing the same

Abstract

To provide a decorative aqueous composition capable of exhibiting a structural color with little turbidity based on colloidal crystals, having little influence on addition of an electrolyte, having good dispersion of colloidal crystals, and being favorably used as a cosmetic; and to provide a method of producing the same.SOLUTION: In a decorative aqueous composition, an aqueous dispersion medium contains 3-10 wt.% colloidal particles having an average particle diameter of 10 nm or more and 1000 nm or less, and 1-20 wt.% polyols. The colloidal particles form colloidal crystals and exhibit a glittering structural color due interference of light by the colloidal crystals.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a decorative aqueous composition in which opal-type or hard-sphere colloidal crystals are dispersed in an aqueous dispersion medium and which exhibits a structural color, and to a method for producing the same. [Background technology]

[0002] Colloidal crystals are particles of uniform diameter arranged in a regular, periodic pattern to form an ordered structure. Like ordinary crystals, colloidal crystals Bragg diffract electromagnetic waves according to the lattice spacing. The diffracted wavelength can be set in the visible light range by selecting the manufacturing conditions (particle concentration, particle diameter, refractive index of the particles or medium, etc.). For this reason, technology has been developed to disperse colloidal crystals in aqueous dispersion media to produce decorative aqueous compositions. Dispersions of these colloidal crystals become liquids with sparkling structural colors due to the interference of visible light, and their application in cosmetics such as lotions has been proposed.

[0003] For example, Patent Document 1 proposes the preparation of a microparticle dispersion exhibiting opal-like structural colors by forming charged colloidal crystals in a dispersion medium, and its application in cosmetics. Charged colloidal crystals are colloidal crystals formed by electrostatic repulsion between particles in a dispersion system (charged colloidal system) of colloidal particles charged by surface charges. When the electrostatic repulsion in a charged colloidal system is weak, colloidal particles move freely due to Brownian motion and assume random positions (see "When interactions between particles are weak" in Figure 1). However, when the electrostatic repulsion becomes strong, particles attempt to move as far away from other particles as possible, resulting in the formation of colloidal crystals arranged at a predetermined lattice spacing (see "When interactions between particles are sufficiently strong" in Figure 1). Because the electrostatic repulsion extends over a long distance, crystals form where the particle concentration is low (i.e., where the distance between particles is long).

[0004] However, in this dispersion of charged colloidal crystals, as the salt concentration increases, electrostatic interactions are blocked, causing particles to approach each other more easily, resulting in van der Waals forces prevailing and making it difficult to maintain a constant distance between the colloidal particles. For example, when the colloidal particles are dilute, charged colloidal crystals do not form at salt concentrations above several tens of μM. Furthermore, when the colloidal particle concentration is 10 vol% or higher, charged colloidal crystals do not form at salt concentrations above approximately 0.1 mM. Therefore, stable charged colloids cannot be formed at salt concentrations above 0.1 mM. Because cosmetics such as lotions contain ionic additives and pH buffers, it has been virtually impossible to use charged colloidal crystals for cosmetic decoration.

[0005] To solve this problem, the present inventors have developed a liquid in which opal-type colloidal crystals are dispersed in an aqueous dispersion medium and have proposed using this as a decorative aqueous composition in cosmetics (Patent Document 2). Opal-type colloidal crystals have a crystalline structure in which particles are in contact with each other and packed together (see the right-hand diagram in Figure 2). The volume fraction of opal-type colloidal crystals, in which colloidal microparticles are crystallized in a close-packed state, varies depending on the crystal structure, being approximately 0.68 for a body-centered cubic lattice and 0.74 for a face-centered cubic lattice.

[0006] In opal-type colloidal crystals, the distance between colloidal particles is maintained by the steric repulsion between them, not by the repulsive forces between their surface charges. This allows the colloidal crystal state to be maintained even at high salt concentrations. This makes it possible to use them for decorating cosmetics that contain ionic additives or pH buffers.

[0007] However, in the decorative aqueous composition of Patent Document 2 consisting of a dispersion of opal-type colloidal crystals, a soluble polymer is added to the dispersion medium, and when colloidal particles approach each other, a narrow region (hereinafter referred to as a "depletion region") is generated into which the dissolved polymer cannot enter (see FIG. 3), thereby generating an osmotic pressure difference and forming opal-type colloidal crystals (see FIG. 3). As a result, as shown in FIG. 4, fine opal-type colloidal crystals 3 are suspended in a dispersion medium 2 dissolving a water-soluble polymer 1 (see FIG. 4), which causes the problem of cloudiness due to light scattering by the opal-type colloidal crystals 3. Furthermore, because the dispersed fine opal-type colloidal crystals 3 are prone to settling, there is a problem of poor dispersion stability when a dispersion medium with low viscosity is used. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 6-100432 [Patent Document 2] WO2019 / 160132 Summary of the Invention [Problem to be solved by the invention]

[0009] The present disclosure has been made in consideration of the above-mentioned conventional circumstances, and an object to be achieved is to provide a decorative aqueous composition that exhibits a structural color with little turbidity based on colloidal crystals, is little affected by the addition of electrolytes, has good dispersibility of colloidal crystals, and can be suitably used as a cosmetic, and a method for producing the same. [Means for solving the problem]

[0010] The decorative aqueous composition of the present disclosure is characterized in that it contains, in an aqueous dispersion medium, 3 to 10 wt % of colloidal particles having an average particle size of 10 nm or more and 1000 nm or less, and 1 to 20 wt % of polyols, and the colloidal particles form colloidal crystals.

[0011] In the decorative aqueous composition of the present disclosure, colloidal crystals are formed in an aqueous dispersion medium (herein, an aqueous dispersion medium is defined as a homogeneous medium containing 50% or more by mass of water, and is a concept that includes, for example, pure water as well as water-alcohol mixtures). Furthermore, because the colloidal particles forming the colloidal crystals are added at a high ratio of 3 to 10% by mass, contact between the densely packed colloidal crystals restricts their freedom of movement, making them less likely to settle, and providing excellent dispersion stability. Furthermore, because of the high colloidal particle content, the colloidal crystals are dispersed throughout the system, reducing light scattering and resulting in less turbidity and a highly transparent composition. Furthermore, because the colloidal crystals are opal-type (or hard sphere-type) colloidal crystals rather than charged colloidal crystals (see Figure 2), they are less susceptible to the effects of adding electrolytes. Furthermore, because the average particle diameter of the colloidal particles forming the colloidal crystals is between 10 nm and 1000 nm, they diffract visible light and exhibit structural colors. Furthermore, since the composition contains 1 to 20% by weight of polyols, the "sticky feeling" caused by the inclusion of a large amount of colloidal particles is alleviated, making it suitable for use as a cosmetic composition.

[0012] From the viewpoint of preventing the sedimentation of the colloidal crystals, the specific gravity of the colloidal particles is preferably 0.9 to 1.1 times the specific gravity of the aqueous dispersion medium.

[0013] Furthermore, the colloidal particles are preferably polymers in which at least one of N-isopropylacrylamide, acrylamide, butyl acrylate, and polyethylene glycol dimethacrylate (n=18) is used as a constituent monomer and crosslinked with a crosslinking agent. Because such colloidal particles form a network structure with the crosslinking agent, 1) the particle size is larger than that of solid particles, and they tend to become opal-type (or hard sphere-type) colloidal crystals. 2) The apparent specific gravity approaches that of an aqueous dispersion medium, making the colloidal crystals less likely to precipitate and resulting in excellent dispersion stability.

[0014] The polyols refer to alcohols having two or more hydroxyl groups in one molecule, such as at least one of 1,3-butylene glycol, 1,2-hexanediol, hexanediol, 1,5-pentanediol, pentylene glycol, isopentyldiol, propanediol, 1,2-propylene glycol, and dipropylene glycol.

[0015] The decorative aqueous composition of the present disclosure preferably further contains 0.01 to 2 wt % of a water-soluble thickener, because increasing the viscosity with the water-soluble thickener makes it difficult for colloidal crystals to settle, thereby improving dispersion stability.

[0016] Furthermore, it is preferable that the coefficient of variation of the particle size of the colloidal particles is 40% or less, which reduces the lattice disorder of the colloidal crystal, facilitating colloidal crystallization and producing a vivid color close to that of monochromatic light.

[0017] The decorative aqueous composition of the present disclosure can be produced by mixing an aqueous dispersion medium, 3 to 10 wt % of colloidal particles having an average particle size of 10 nm or more and 1000 nm or less, and 1 to 20 wt % of polyols. The composition thus obtained is an aqueous dispersion of colloidal crystals composed of colloidal particles.

[0018] A crosslinked hydrophilic polymer can be suitably used as the colloidal particles. Such colloidal particles are easily dispersed in an aqueous dispersion medium due to their hydrophilicity, and have a network structure that makes their apparent specific gravity closer to that of an aqueous dispersion, making it difficult for the colloidal crystals to settle. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing the formation of charged colloidal crystals. [Figure 2] 1 is a schematic diagram showing a phase transition in a colloidal system. [Figure 3] FIG. 1 is a schematic diagram illustrating the depletion effect of polymer dissolution in a colloidal system. [Figure 4] FIG. 1 is a schematic enlarged view of the decorative aqueous composition of Patent Document 2. [Figure 5] FIG. 1 is a schematic enlarged view of a decorative aqueous composition according to the present disclosure. [Figure 6] 1A to 1C are a process diagram and a schematic diagram illustrating a method for producing a decorative aqueous composition according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments embodying the present disclosure will be described with reference to the drawings. A schematic diagram of a decorative aqueous composition according to an embodiment is shown in Figure 5. This decorative aqueous composition has opal-type colloidal crystals 5 dispersed in an aqueous dispersion medium 4. The colloidal crystals 5 are formed from regularly arranged colloidal particles 6, and the colloidal particles 6 are contained in a large amount of 3 to 10% by weight. As a result, the colloidal crystals 5 come into contact with each other, restricting their freedom of movement and making them less likely to settle. From the viewpoint of preventing sedimentation of the colloidal crystals 5, the specific gravity of the colloidal particles 6 is preferably 0.9 to 1.1 times the specific gravity of the aqueous dispersion medium 4. It is more preferably 0.99 to 1.01 times, and most preferably 0.995 to 1.005 times. In particular, when the colloidal particles are crosslinked polymers that form a network structure, the volume percentage of colloidal particles 6 relative to the volume of the entire system becomes large, and the degree of crowding of colloidal particles 6 becomes extremely large, making it even more difficult for colloidal crystals 5 to settle. Furthermore, because colloidal crystals 5 are in a dense state, they spread throughout the system, making it difficult for light scattering to occur, resulting in less turbidity and a more transparent solution. Furthermore, because the average particle diameter of the colloidal particles 6 is set to 10 nm or more and 1000 nm or less, diffraction of visible light occurs, resulting in structural color. A more preferable range is 20 nm or more and 830 nm or less, and a most preferable range is 100 nm or more and 500 nm or less. While the lower limit of the wavelength range of visible light is said to be 360 ​​to 400 nm, colloidal particles may undergo secondary aggregation, so even colloidal particles with an average particle diameter below this lower limit can still diffract visible light. Furthermore, if the coefficient of variation of the particle size of the colloidal particles 6 is 40% or less, there will be little disorder within the colloidal crystal, and a vivid color close to monochromatic light will be exhibited. The coefficient of variation is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less.

[0021] In addition, the decorative aqueous composition of the present embodiment contains 1 to 20 wt % of polyols to eliminate the "stickiness" caused by the large amount of colloidal particles (3 to 10 wt %). This makes it suitable for use as a cosmetic. Examples of polyols that can be used include at least one of 1,3-butylene glycol, 1,2-hexanediol, hexanediol, 1,5-pentanediol, pentylene glycol, isopentyldiol, propanediol, 1,2-propylene glycol, and dipropylene glycol.

[0022] The decorative aqueous composition of the present disclosure preferably further contains 0.01 to 2 wt % of a water-soluble thickener. By increasing the viscosity with the water-soluble thickener, the colloidal crystals become less likely to settle, thereby enhancing dispersion stability. The water-soluble thickener is not particularly limited, but when used as a cosmetic, for example, carboxyvinyl polymers are preferred from the viewpoint of their refreshing feel. Only one type of water-soluble thickener may be used, or multiple types may be used in combination.

[0023] Other water-soluble thickeners that can be used include, for example, at least one of water-soluble polymers such as guar gum, xanthan gum, and polyvinyl alcohol; taurate-based polymer thickeners such as polymers and / or copolymers (including crosslinked polymers) having 2-acrylamido-2-propanesulfonic acid (acryloyldimethyltaurate) or its salts (AMPS) as a constituent unit; and acrylate-based synthetic polymer thickeners.

[0024] Examples of taurate-based polymer thickeners include (ammonium acryloyldimethyltaurate / beheneth-25 methacrylate) crosspolymer (Aristoflex® HMB, Clariant Japan), (ammonium acryloyldimethyltaurate / vinylpyrrolidone) copolymer (Aristoflex® AVC, Clariant Japan), (ammonium acryloyldimethyltaurate / carboxyethyl acrylate) crosspolymer (Aristoflex® TAC, Clariant Japan), polyacrylate crosspolymer-11 (Aristoflex® Velvet, Clariant Japan), (dimethylacrylamide / sodium acryloyldimethyltaurate) crosspolymer, (hydroxyethyl acrylate / sodium acryloyldimethyltaurate) copolymer (SEPINOV EMT10, Pinobu, SEPPIC), (sodium acrylate / acryloyldimethyltaurate / dimethylacrylamide) crosspolymer (SEPINOV P88, SEPPIC), (sodium acrylate / sodium acryloyldimethyltaurate) copolymer (SIMULGEL EG, SEPPIC), (sodium acryloyldimethyltaurate / methacrylamidolaurate) copolymer (AMO-51, Daito Kasei Kogyo Co., Ltd.), and (acrylamide / sodium acryloyldimethyltaurate / acrylic acid) copolymer (Acudyne SCP, Dow Chemical Co., Ltd.) can be used.

[0025] Examples of acrylate-based synthetic polymer thickeners that can be used include (acrylates / steareth-20 methacrylate) copolymer (ACULYN (registered trademark) 22, Dow Chemical Company), (acrylates / C10-30 alkyl acrylate) crosspolymer (PEMULEN (registered trademark) TR-1, PEMULEN (registered trademark) TR-2, Lubrizol), and the like.

[0026] Other water-soluble thickeners that can be used include, for example, gum arabic, carrageenan, karaya gum, tragacanth gum, carob gum, quince seed, casein, dextrin, gelatin, sodium pectinate, sodium allaginate, methylcellulose, ethylcellulose, carboxymethylcellulose (CMC), hydroxyethylcellulose, hydroxypropylcellulose, polyvinyl alcohol (PVA), polyvinyl methyl ether (PVM), PVP (polyvinylpyrrolidone), sodium polyacrylate, carboxyvinyl polymer, locust bean gum, guar gum, tamarind gum, dialkyldimethylammonium cellulose sulfate, xanthan gum, aluminum magnesium silicate, bentonite, hectorite, aluminum magnesium silicate (Bee Gum), Laponite, and silicic anhydride.

[0027] The preferred content of the water-soluble thickener in the cosmetic may be selected as appropriate depending on the type of water-soluble thickener used, but when a carboxyvinyl polymer is used, for example, the content is preferably 0.05 to 0.3% by mass.

[0028] Furthermore, the colloidal particles that form colloidal crystals are preferably particles made of hydrophilic polymers. This facilitates stable dispersion of colloidal crystal particles in an aqueous dispersion medium. Examples of polymers that constitute such colloidal particles include poly(N-isopropylacrylamide), polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyether, and polyvinylpyrrolidone. Examples of water-soluble ionic polymers include cationic polymers such as polyvinylpyridine, polyvinylbenzylammonium, and polypeptides, as well as polyacrylic acid, polyacrylamide, polypeptides, and hyaluronic acid. Natural anionic polymers made of polysaccharides such as chondroitin sulfate and alginic acid can also be used. For example, when using alginic acid as colloidal particles, the colloidal particles can be prepared by adding calcium ions to an aqueous solution of a water-soluble alginate (e.g., sodium alginate) to form a poorly water-soluble salt. More preferred are hydrophilic colloidal particles made of crosslinked polymers, which allow the dispersion medium to pass freely through the crosslinked network structure, making the apparent specific gravity of the colloidal particles very close to that of the dispersion medium, and allowing the colloidal crystals to be stably dispersed in the dispersion medium without settling. On the other hand, hydrophobic particles made of hydrophobic polymers such as polystyrene can also be used if they are modified with dissociative groups, since they are dispersible in aqueous dispersion media. Examples of such polymers include copolymers of styrene and styrene sulfonic acid.

[0029] <Manufacturing method> The decorative aqueous composition of the present disclosure can be produced according to the steps shown in FIG. (Colloid particle preparation step S1) First, in the colloid particle preparation step S1, hydrophilic colloid particles made of crosslinked polymers are prepared. That is, the raw materials for the polymer, a monomer, a crosslinking agent, a polymerization initiator, and a surfactant, are dispersed and mixed in purified water, and then emulsion polymerization is carried out by heating. This results in a liquid in which colloid particles made of crosslinked polymers are dispersed in a dispersion medium.

[0030] (Colloidal particle purification step S2) Furthermore, salt water is added to the resulting dispersion of colloidal particles, and after stirring, the liquid is heated to a temperature of 50°C or higher and allowed to stand to allow the colloidal particles to settle. The supernatant is then removed by decantation, and distilled water is added. By repeating these steps, the surfactant and polymerization initiator added during emulsion polymerization are removed. Note that dialysis or membrane separation may also be used as a method for purifying the colloidal particles instead of decantation.

[0031] (Colloid particle drying process S3) The supernatant is removed and the colloid particles that have settled in the lower layer are dried to obtain a colloid particle powder. Note that the colloid particles may be dispersed in an aqueous dispersion medium and then transferred to the next colloid crystallization step S4 without undergoing the colloid particle drying step S3.

[0032] (Colloidal crystallization step S4) The colloid particle powder obtained in the colloid particle drying step S3 is dispersed in an aqueous solution of polyols, and then allowed to stand to produce a decorative aqueous composition in which colloidal crystals made of the colloid particle powder are dispersed (see Figure 5). When the decorative aqueous composition thus obtained is irradiated with light, the colloidal crystals interfere with the light, causing it to exhibit a sparkling structural color. [Example]

[0033] Examples that further embody the present disclosure will be described below in comparison with comparative examples. Preparation of colloidal particles A colloidal particle dispersion was prepared by emulsion polymerization using N-isopropylacrylamide (NIPAM, Fujifilm Wako Pure Chemical Industries, Ltd.) and acrylamide (AAm, Fujifilm Wako Pure Chemical Industries, Ltd.) as monomers and N,N'-methylenebisacrylamide (BIS, Fujifilm Wako Pure Chemical Industries, Ltd.) as a crosslinker. The process is described in detail below. A monomer solution was prepared by dissolving NIPAM (31.2 g), AAm (2.34 g), and BIS (2.50 g) in Milli-Q water (356.0 g). A polymerization initiator solution was also prepared by dissolving potassium peroxodisulfate (KPS, Fujifilm Wako Pure Chemical Industries, Ltd.) (0.2 g) in deionized water (70.0 g). A 25% aqueous solution of sodium laureth-4 carboxylate (2.68 g) and deionized water (224.40 g) were added to a 1 L four-necked, separable round-bottom flask as an emulsifier, mixed, and heated to 85°C. The monomer solution was then added dropwise over 3.5 hours under a nitrogen stream. During the dropwise addition of the monomer solution, 7.0 mL of the polymerization initiator solution was added every 30 minutes. The mixture was then stirred at 150 rpm for 4 hours at 85°C for emulsion polymerization, yielding a dispersion of colloidal particles in which N-isopropylacrylamide and acrylamide copolymers were crosslinked with BIS. The particle size of the particles in this dispersion was measured using dynamic light scattering. The coefficient of variation (%) of particle size was calculated by (standard deviation of particle size / average particle size) × 100 (same applies below). The 4-5 wt% colloidal particle dispersion was passed through a 5 μm filter to remove aggregates and dust. 20 μL of this sample was added to 5 mL of 0.1 mM NaCl aqueous solution, and the number-frequency particle size distribution was determined using a Nikkiso Nanotrac particle size analyzer (UPA-EX150) with a refractive index of 1.48 and a medium of 1.33 for water. The resulting average particle size was 211 nm, with a coefficient of variation of 25%.

[0034] Colloidal particle purification To the colloid particle dispersion obtained as described above, an aqueous NaCl solution was added to a total concentration of 0.07 wt%, and after stirring, the mixture was left to stand at 50°C for 30 minutes to allow the colloid particles to settle. The upper layer was then removed, and an aqueous NaCl solution was added again to a total concentration of 0.07 wt%. This procedure was repeated several times to remove the surfactant, yielding an aqueous dispersion of colloid particles. -Powdering of colloidal particles The aqueous dispersion of the purified colloidal particles was placed on release paper and dried at 80-95°C under a nitrogen stream, and the dried product was pulverized to obtain a powder of colloidal particles. The particle size of this powder, when redissolved in water, was measured using dynamic light scattering, and the average particle size was 201 nm, with a coefficient of variation of 37%.

[0035] <Production of Decorative Water-Based Composition> The powder of colloidal particles obtained as described above was used to produce compositions of Examples 1 to 9 and Comparative Examples 1 to 8 according to the following procedure. A colloidal particle powder was dispersed in 1,3-butanediol using a disperser and then gradually added to water stirred with a propeller. Propeller stirring was continued at room temperature until the mixture was thoroughly dispersed, after which glycerin was added. A solution of methylparaben (methyl parahydroxybenzoate) dissolved in 1,3-butanediol by heating was then added. Furthermore, in Examples 6 to 9 and Comparative Examples 1 to 3, an aqueous solution of potassium hydroxide neutralized carbomer (crosslinked polyacrylic acid, Carbopole® 980, Lubrizol) was added and homogenized using a propeller to produce the decorative aqueous compositions of Examples 1 to 9 and Comparative Examples 1 to 3. Here, 1,3-butanediol was the polyol, and carbomer was the thickener. Note that carbomer was not added in Examples 1 to 5 and Comparative Examples 4 to 8; otherwise, compositions were obtained in the same manner. The charging ratios of each agent are shown in Table 1.

[0036] <Evaluation> The decorative aqueous compositions of Examples 1 to 9 and Comparative Examples 1 to 8 obtained as described above were evaluated for their decorative properties on appearance and their feel when applied to the skin by the following methods.

[0037] (Exterior decoration) The decorativeness of the appearance of the decorative aqueous composition was visually observed. The evaluation criteria are as follows: ◎: Structural color due to colloidal crystals is predominantly observed ○: Structural color based on colloidal crystals is observed △: Structural color due to colloidal crystals is slightly observed ×: No structural color based on colloidal crystals is observed

[0038] (Feeling of use) The decorative aqueous compositions were applied to the faces of five cosmetic expert panelists, and the feel of use in terms of stickiness and sliminess was scored on a five-point scale: bad: 1 point, slightly bad: 2 points, normal: 3 points, slightly good: 4 points, and good: 5 points. Evaluation was performed using the average score of the five panelists. The evaluation criteria are as follows: ◎: Average score is 4.5 or above, ○: Average score is 3.5 or more and less than 4.5, △: Average score is 2.5 or more but less than 3.5; ×: Average score is less than 2.5

[0039] [Table 1]

[0040] The evaluation results are shown in Table 1. - Regarding exterior decoration In Examples 1 to 9, in which the colloidal particle concentration was 3 to 10% by mass, the decorativeness of the appearance was rated as ◯ or ⊚, and structural colors based on colloidal crystals were observed. In contrast, in Comparative Examples 2 and 5, in which the colloidal particle concentration was 1% by mass, the decorativeness of the appearance was rated as △, and structural colors based on colloidal crystals were only slightly observable. Furthermore, in Comparative Examples 3 and 6, in which the colloidal particle concentration was 11% by mass, the decorativeness of the appearance was also rated as △, and structural colors based on colloidal crystals were only slightly observable. From these results, it was found that the preferable range for observing structural colors based on colloidal crystals is 3 to 10% by mass. In Examples 1 to 5, the water-soluble polymer carbomer (crosslinked polyacrylic acid) was not included, and no other water-soluble polymers were included, so it is believed that no depletion attractive forces act between the colloidal particles. Nevertheless, structural colors based on colloidal crystals were observed because the colloidal particles were included at high concentrations of 3 to 10% by mass, resulting in the formation of opal-type (or hard sphere-type) colloidal crystals. Furthermore, in Examples 6 to 9, in which carbomer (crosslinked polyacrylic acid) was added, 0.05% by mass (8.91 mmol in molar terms) of potassium hydroxide was added to neutralize the carboxyl groups of the carbomer. This electrolyte concentration was too high to form charged colloidal crystals, and therefore the observed structural color was a structural color based on opal-type colloidal crystals or hard sphere-type colloidal crystals.

[0041] About the feel of use In Examples 1 to 9, in which 10 to 20% by mass of 1,3-butanediol was added as a polyol, the feel in use was rated as ◯ or ⊚, which was a good evaluation. In addition, in Comparative Examples 1 to 6, in which 10% by mass of 1,3-butanediol was added, the feel in use was also rated as ◯. In contrast, Comparative Example 7, in which no 1,3-butanediol was added, was rated as △, and Comparative Example 8, in which 25% by mass of 1,3-butanediol was added, was rated as ×, indicating that the feel in use deteriorates when no 1,3-butanediol is added or when more than 20% by mass of 1,3-butanediol is added.

[0042] The configurations and combinations thereof in each embodiment and example are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible as appropriate within the scope of the gist of this disclosure. The present disclosure is not limited to the embodiments and examples, but is limited only by the scope of the claims. [Industrial Applicability]

[0043] The decorative aqueous composition of the present disclosure contains opal-type (or hard sphere-type) colloidal crystals dispersed in an aqueous dispersion medium, and exhibits a sparkling, minimally cloudy structural color due to Bragg diffraction. Furthermore, the structural color does not change even at a salt concentration of approximately 0.1 mM, making it suitable for use in cosmetics such as lotions. [Explanation of symbols]

[0044] 1...aqueous dispersion medium, 2...polymer, 3...opal-type colloidal crystal, 4...aqueous dispersion medium, 5...colloidal crystal, 6...colloidal particle S1: Colloid particle preparation process, S2: Colloid particle purification process, S3: Colloid particle drying process, S4: Colloid crystallization process

Claims

1. The decorative aqueous composition contains, in an aqueous dispersion medium, 3 to 10% by weight of colloidal particles having an average particle size of 10 nm or more and 1,000 nm or less, and 1 to 20% by weight of polyols, the colloidal particles being composed of at least one of a poorly water-soluble salt of chondroitin sulfate and a poorly water-soluble salt of alginic acid, and forming colloidal crystals.

2. 2. The decorative aqueous composition according to claim 1, wherein the specific gravity of the colloidal particles is 0.9 to 1.1 times the specific gravity of the aqueous dispersion medium.

3. 3. The decorative aqueous composition according to claim 1, wherein the polyol is at least one of 1,3-butylene glycol, 1,2-hexanediol, hexanediol, 1,5-pentanediol, pentylene glycol, isopentyldiol, propanediol, 1,2-propylene glycol, and dipropylene glycol.

4. 4. The decorative aqueous composition according to claim 1, further comprising 0.01 to 2% by weight of a water-soluble thickener.

5. 5. The decorative aqueous composition according to claim 1, wherein the coefficient of variation of the particle diameter of the colloidal particles is 40% or less.

6. A method for producing a decorative aqueous composition, comprising mixing an aqueous dispersion medium with 3 to 10% by weight of colloidal particles having an average particle size of 10 nm or more and 1000 nm or less, and 1 to 20% by weight of a polyol, wherein the colloidal particles comprise at least one of a poorly water-soluble salt of chondroitin sulfate and a poorly water-soluble salt of alginic acid.

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