Method for manufacturing silica microcapsules

Abstract

The present invention relates to: [1] a method for manufacturing silica microcapsules, the silica microcapsules having a shell containing silica as a constituent component and a core containing one or more organic compounds, the manufacturing method comprising the following steps: in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions and sulfonic acid ions, an emulsion is supplied to a sol-gel reaction to form silica microcapsules, wherein the emulsion is obtained by emulsifying an aqueous phase component containing a cationic surfactant and an oil phase component containing one or more organic compounds and a silica source; [2] an aqueous dispersion containing silica microcapsules, the silica microcapsules having a shell containing silica as a constituent component and a core containing one or more organic compounds, the total content of sulfate ions, sulfite ions and sulfonic acid ions in the aqueous dispersion being 10 to 500 ppm.

Description

Technical Field

[0001] This invention relates to a method for manufacturing silica microcapsules and an aqueous dispersion of silica microcapsules. Background Technology

[0002] Microcapsules containing fragrances or bioactive agents have been developed and utilized in a wide range of industries, including cosmetics, pharmaceuticals, household goods, and printing. For example, amino plastic resins such as melamine resin or polyurea / polyurethane resin are used as the shell of these microcapsules. However, microcapsules cannot avoid being released into the environment, and in recent years, this has become a cause for concern as microplastics. Therefore, there is a desire to develop a more environmentally friendly microcapsule to replace amino plastic resins.

[0003] Among them, silica microcapsules (hereinafter also referred to as "silica capsules") with a shell composed of silica have attracted much attention as a material that can be expected to be environmentally friendly.

[0004] Silica capsules are typically produced by forming silica on the surface of emulsion droplets using a sol-gel method. However, because silica capsules consist of extremely small particles, their shells are also very thin and brittle. Therefore, sometimes due to shell disintegration, the encapsulated components diffuse through the micropores of the shell, resulting in the release of some of these components into the external environment. Consequently, research continues on various methods for manufacturing silica capsules using the sol-gel method.

[0005] For example, Japanese Patent Application Publication No. 2013-255915 (Patent Document 1) discloses a method for manufacturing microcapsules having a core material containing active ingredients such as sunscreens. The method for manufacturing microcapsules includes the following steps: emulsifying an oily phase composed of a water-insoluble precursor and a core material in an aqueous phase composed of an aqueous solution having a specified pH to produce an oil-in-water droplet emulsion, wherein the aqueous phase used in this step contains a cationic surfactant.

[0006] In Japanese Patent Application Publication No. 2015-128762 (Patent Document 2), the object is to provide a method for manufacturing microcapsules that can retain active ingredients such as fragrances, i.e., organic compounds, for a long time. The method describes the following: In the method for manufacturing microcapsules having a core composed of organic compounds such as fragrances, a first shell enclosing the core, and a second shell enclosing the first shell, a first-stage sol-gel reaction is carried out in an aqueous phase containing a surfactant, with an organic phase containing organic compounds and tetraalkoxysilane being emulsified. Then, tetraalkoxysilane is added, and a second-stage sol-gel reaction is carried out while maintaining a pH lower than that of the first-stage sol-gel reaction. Summary of the Invention

[0007] This invention provides a method for manufacturing silica microcapsules, wherein,

[0008] The silica microcapsules have: a shell containing silica as a constituent component; and a core containing one or more organic compounds inside the shell.

[0009] The method for manufacturing the silica microcapsules includes the following steps: supplying an emulsion to a sol-gel reaction to form silica microcapsules in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions.

[0010] The emulsion is obtained by emulsifying an aqueous phase component containing a cationic surfactant and an oil phase component containing one or more organic compounds and a silica source. Detailed Implementation

[0011] It has been confirmed that in the technologies of Patent Documents 1 and 2, sometimes due to the different oils contained within, the target silica capsules that suppress the leakage of nuclear components cannot be obtained, and the fragrances and other organic compounds cannot be adequately preserved with a high encapsulation rate.

[0012] This invention relates to a method for manufacturing silica microcapsules and an aqueous dispersion containing silica microcapsules. The silica microcapsules of this invention stably encapsulate active ingredients such as fragrances, i.e., organic compounds, with a high encapsulation rate.

[0013] The inventors have discovered that by supplying an emulsion containing anions such as sulfate ions, sulfite ions, or sulfonic acid ions in the system to a sol-gel reaction, silica microcapsules can be obtained that stably encapsulate effective ingredients such as fragrances, i.e., organic compounds, with a high encapsulation rate.

[0014] That is, the present invention relates to the following [1] and [2].

[0015] [1] A method for manufacturing silica microcapsules, wherein the silica microcapsules have: a shell containing silica as a constituent component; and a core containing one or more organic compounds inside the shell.

[0016] The method for manufacturing the aforementioned silica microcapsules includes the following steps: supplying an emulsion to a sol-gel reaction to form silica microcapsules in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions.

[0017] The emulsion described above is obtained by emulsifying an aqueous phase component containing a cationic surfactant and an oil phase component containing one or more organic compounds and a silica source.

[0018] [2] An aqueous dispersion comprising silica microcapsules having: a shell containing silica as a constituent component; and a core containing one or more organic compounds inside the shell.

[0019] The total content of sulfate ions, sulfite ions, and sulfonic acid ions in the aqueous dispersion is between 10 ppm and 500 ppm.

[0020] According to the present invention, a method for manufacturing silica microcapsules and an aqueous dispersion containing silica microcapsules can be provided. The silica microcapsules of the present invention stably encapsulate effective ingredients such as fragrances, i.e., organic compounds, with a high encapsulation rate.

[0021] [Manufacturing method of silica microcapsules]

[0022] The method for manufacturing silica microcapsules (silica capsules) of the present invention is a method for manufacturing silica capsules having a shell containing silica as a constituent component and a core containing one or more organic compounds inside the shell, comprising the following steps (hereinafter also referred to as "step I"): a step of supplying an emulsion to a sol-gel reaction to form silica microcapsules in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions, wherein the emulsion is obtained by emulsifying an aqueous phase component containing a cationic surfactant and an oil phase component containing one or more organic compounds and a silica source.

[0023] In this invention, "silicon dioxide source" refers to a substance that can form the shell of a silicon dioxide capsule, such as tetraalkoxysilane, which can be hydrolyzed to generate silanol compounds.

[0024] The "sol-gel reaction" in this invention refers to the reaction in which a silica source forms silica, a component of the shell, through hydrolysis and condensation reactions, via sol and gel states. Examples of sol-gel reactions include: a tetraalkoxysilane, used as a silica source, is hydrolyzed; a silanol compound undergoes dehydration condensation and dealcohydride condensation reactions to generate a siloxane oligomer; further dehydration condensation reactions then occur, thereby generating silica.

[0025] According to the present invention, a method for manufacturing silica capsules that stably encapsulate active ingredients such as fragrances (i.e., organic compounds) with a high encapsulation rate, and an aqueous dispersion containing silica capsules, are provided. The reasons for this are not yet clear, but are believed to be as follows.

[0026] In the manufacturing method of the present invention, because a cationic surfactant is used as an emulsifier for the emulsion supplied to the sol-gel reaction, the surface of the emulsion droplet forming the silica capsule becomes positively charged. Furthermore, it is believed that when this emulsion with the emulsion droplets formed is supplied to the sol-gel reaction in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions, the sulfate ions, sulfite ions, or sulfonic acid ions present in the system achieve a resonance structure through the non-local presence of electrons between at least two oxygen atoms and one sulfur atom. Therefore, at least two oxygen atoms of these ions are negatively charged. Through the mutual electrostatic interaction between these negatively charged oxygen atoms and the positively charged nitrogen atoms of the cationic surfactant on the surface of the emulsion droplet forming the silica capsule, the filling of the cationic surfactant on the surface of the emulsion droplet becomes dense, and the charge density on the surface of the emulsion droplet increases. In this state, the formation of the shell at the emulsion droplet interface is accelerated, forming a dense and robust shell. It is believed that the result can suppress the leakage of nuclear components and provide silica capsules that stably encapsulate organic compounds with a high encapsulation rate.

[0027] <Emulsion>

[0028] The emulsion used in the manufacturing method of the present invention is obtained by emulsifying an aqueous phase component containing a cationic surfactant and an oil phase component containing one or more organic compounds and a silica source.

[0029] [Catonic surfactants]

[0030] The aqueous phase of the emulsion contains cationic surfactants.

[0031] Examples of cationic surfactants include alkylamine salts and alkyl quaternary ammonium salts. The alkyl group of the alkylamine salt and alkyl quaternary ammonium salt preferably has 10 or more carbon atoms, more preferably 12 or more, even more preferably 14 or more, and more preferably 22 or less, more preferably 20 or less, and even more preferably 18 or less.

[0032] Examples of alkylamine salts include laurylamine acetate and stearylamine acetate.

[0033] Examples of alkyl quaternary ammonium salts include alkyl trimethylammonium salts, dialkyl dimethylammonium salts, and alkyl benzyl dimethylammonium salts.

[0034] The balancing ion of the cationic group of the above-mentioned cationic surfactant is preferably a halide ion such as chloride ion or bromide ion, and more preferably a chloride ion.

[0035] It is believed that when the equilibrium ion of the cationic group of the aforementioned cationic surfactant is a chloride ion, an exchange reaction is effectively induced on the surface of the emulsion droplet from chloride ions to sulfate ions, sulfite ions, or sulfonic acid ions originating from compound (A). This results in a denser filling of the cationic surfactant on the surface of the emulsion droplet, increasing the charge density on the surface and accelerating the formation of a shell at the emulsion droplet interface, leading to the formation of a dense and robust shell. Consequently, it is believed that this increases the encapsulation rate of the organic compound, resulting in stably encapsulated silica capsules.

[0036] Examples of the above-mentioned alkyltrimethylammonium salts include: lauryltrimethylammonium chloride, hexadecyltrimethylammonium chloride, stearyltrimethylammonium chloride, and other alkyltrimethylammonium chlorides; lauryltrimethylammonium bromide, hexadecyltrimethylammonium bromide, stearyltrimethylammonium bromide, and other alkyltrimethylammonium bromide.

[0037] Examples of the above-mentioned dialkyl dimethyl ammonium salts include: dialkyl dimethyl ammonium chloride such as distearate dimethyl ammonium chloride; and dialkyl dimethyl ammonium bromide such as distearate dimethyl ammonium bromide.

[0038] Examples of alkylbenzyl dimethyl ammonium salts include alkylbenzyl dimethyl ammonium chloride and alkylbenzyl dimethyl ammonium bromide.

[0039] Regarding the aforementioned cationic surfactants, one or more can be used alone.

[0040] Among these substances, the aforementioned cationic surfactant is preferably a quaternary ammonium salt, more preferably an alkyltrimethylammonium salt having an alkyl group having 10 to 22 carbon atoms, even more preferably an alkyltrimethylammonium halide having an alkyl group having 10 to 22 carbon atoms, even more preferably an alkyltrimethylammonium chloride having an alkyl group having 10 to 22 carbon atoms, even more preferably one or more selected from lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, and hexadecyltrimethylammonium chloride, and even more preferably hexadecyltrimethylammonium chloride.

[0041] From the viewpoint of obtaining a stable emulsion that stably encapsulates organic compounds with a high encapsulation rate, the amount of cationic surfactant used in the manufacturing method of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.7% by mass or less.

[0042] Here, the amount of cationic surfactant is the proportion when the amount of the above-mentioned organic compound is set to 100% by mass.

[0043] It should be noted that, from the viewpoint of obtaining a stable emulsion and effectively encapsulating organic compounds, the content of cationic surfactants in the above-mentioned aqueous phase components is preferably less than 0.5% by mass.

[0044] [Organic compounds]

[0045] The oil phase component of the above emulsion contains one or more organic compounds.

[0046] The aforementioned organic compound is preferably selected from one or more of fragrances, fragrance precursors, oils (humectants), antioxidants, antibacterial agents, fertilizers, fibers, skin, and hair surface modifiers, cooling agents, dyes, pigments, silicones, solvents, and oil-soluble polymers; more preferably selected from one or more of fragrances, fragrance precursors, oils (humectants), antioxidants, antibacterial agents, fertilizers, surface modifiers, and solvents; even more preferably selected from one or more of fragrances, fragrance precursors, humectants, antioxidants, and solvents; even more preferably selected from one or more of fragrances, fragrance precursors, and oils; and even more preferably selected from one or more of fragrances and fragrance precursors.

[0047] Regarding the aforementioned organic compounds, one or more can be used alone.

[0048] Examples of fragrance precursors include compounds that release fragrance components by reacting with water and compounds that release fragrance components by reacting with light.

[0049] Examples of compounds that release fragrance components upon reaction with water include: silicate ester compounds having alkoxy groups derived from fragrance alcohols; fatty acid ester compounds having alkoxy groups derived from fragrance alcohols; acetal or hemiacetal compounds obtained by reacting a carbonyl group derived from a fragrance aldehyde or ketone with an alcohol compound; Schiff base compounds obtained by reacting a carbonyl group derived from a fragrance aldehyde or ketone with a primary amine compound; and hemiamine acetal or hydrazone compounds obtained by reacting a carbonyl group derived from a fragrance aldehyde or ketone with a hydrazine compound.

[0050] Examples of compounds that release fragrance components upon photoreaction include: 2-nitrobenzyl ether compounds having an alkoxy group derived from a fragrance alcohol; α-keto ester compounds having a carbonyl group derived from a fragrance aldehyde or ketone; and coumarate ester compounds having an alkoxy group derived from a fragrance alcohol. These fragrance precursors can, for example, be used as polymers of the reaction product of a portion of the carboxyl group of polyacrylic acid and a fragrance alcohol.

[0051] From the viewpoint of obtaining a stable emulsion that stably encapsulates an organic compound with a high encapsulation rate, the aforementioned organic compound preferably has appropriate hydrophobicity.

[0052] As an indicator of the hydrophilicity or hydrophobicity of the aforementioned organic compounds, the commonly used logarithm LogP, i.e., the cLogP value, can be calculated using the partition coefficient P (octanol / water) between n-octanol and water. The cLogP value is calculated using the method described in A. Leo Comprehensive Medicinal Chemistry, Vol. 4, C. Hansch, P. G. Sammens, J.B. Taylor and C.A. Ramsden, Eds., P. 295, Pergamon Press, 1990, and is a value calculated by the program CLOGP v4.01.

[0053] When the above-mentioned organic compound is composed of multiple components, the cLogP value of the organic compound can be obtained by multiplying the cLogP value of each component by the volume ratio of each component and summing them.

[0054] The cLogP value of the above-mentioned organic compound is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and preferably 30 or less, more preferably 20 or less, and even more preferably 10 or less.

[0055] [Silica source]

[0056] The oil phase component of the above emulsion contains a silica source.

[0057] From the viewpoint of forming a dense and robust shell and stably encapsulating organic compounds with a high encapsulation rate, the aforementioned silica source preferably contains tetraalkoxysilane as the main component, more preferably tetraalkoxysilane having alkoxy groups having 1 to 4 carbon atoms, further preferably one or more selected from tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane, even more preferably one or more selected from tetramethoxysilane and tetraethoxysilane, and even more preferably tetraethoxysilane.

[0058] When the aforementioned silica source contains tetraalkoxysilane, it may also contain triethoxysilane, trimethoxysilane, or other trialkoxysilanes. However, the content of tetraalkoxysilane in the aforementioned silica source is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less.

[0059] From the viewpoint of forming a shell surrounding the oil-phase emulsion droplets containing the organic compound, the amount of silica source used in the manufacturing method of the present invention is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, relative to the amount of the organic compound. Moreover, from the viewpoint of suppressing the residue of silica source inside the oil-phase droplets and effectively converting the silica source to the shell, it is preferably 100% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and even more preferably 30% by mass or less.

[0060] Here, the amount of silica source is the proportion when the amount of the above-mentioned organic compound is set to 100% by mass.

[0061] From the viewpoint of manufacturing efficiency, the amount of oil phase component in the total amount of the above-mentioned emulsion is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more. Moreover, from the viewpoint of obtaining a stable emulsion, it is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less, and even more preferably 30% by mass or less.

[0062] (Preparation of emulsion)

[0063] In this invention, the emulsion is preferably prepared by a method comprising steps 1 to 3 described below.

[0064] Step 1: The process of preparing an aqueous phase component containing a cationic surfactant.

[0065] Step 2: A step of preparing the oil phase by mixing one or more organic compounds and a silica source.

[0066] Step 3: The process of mixing and emulsifying the aqueous phase component obtained in Step 1 and the oil phase component obtained in Step 2 to obtain an emulsion.

[0067] From a productivity point of view, the stirring device used in mixing the organic compound and the silica source in step 2 is preferably the same as the stirring device used in mixing and emulsifying the aqueous and oil phase components in step 3.

[0068] There are no particular limitations on the mixing equipment used in steps 2 and 3; homogenizers, high-pressure dispersers, ultrasonic dispersers, etc., which have strong shearing force can be used. In addition, homogenizers, "Disper" (trade name, manufactured by Primix Co., Ltd.), "CLEARMIX" (trade name, manufactured by M-Technique Co., Ltd.), "CAVITRON" (trade name, manufactured by Taihei Kiko Co., Ltd.), etc., can also be used.

[0069] From the perspective of reducing the specific surface area of ​​silica capsules relative to the external environment and increasing the encapsulation rate of organic compounds, the median particle size D of the emulsion droplets of the above-mentioned emulsion is... 50 Preferably, the micrometer is 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. Furthermore, from the viewpoint of improving the physical strength of the silica capsule and stably encapsulating organic compounds with a high encapsulation rate, it is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, even more preferably 5 μm or less, even more preferably 3 μm or less, and even more preferably 2 μm or less.

[0070] The above median particle size D 50 It can be determined by the methods described in the examples.

[0071] [Compound (A)]

[0072] The manufacturing method of the present invention involves subjecting the above-mentioned emulsion to a sol-gel reaction in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions, as described later.

[0073] From the viewpoint of forming a dense and robust shell and stably encapsulating organic compounds with a high encapsulation rate, the sulfur-containing ion is preferably selected from one or more of sulfate ions, sulfite ions, aromatic sulfonic acid ions, and aliphatic sulfonic acid ions, more preferably selected from one or more of sulfate ions, sulfite ions, and p-toluenesulfonate anions, further preferably selected from one or more of sulfate ions and sulfite ions, and even more preferably sulfate ions.

[0074] In step I, as a method for carrying out a sol-gel reaction in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions, it is preferable to add one or more compounds (A) selected from sulfuric acid, sulfite, sulfonic acid compounds, and their salts to the emulsion and then carry out the sol-gel reaction. As a result, the presence of sulfate ions, sulfite ions, or sulfonic acid ions anions in the emulsion system leads to a denser filling of the cationic surfactant on the surface of the emulsion droplets, increasing the charge density on the surface of the emulsion droplets. Under these conditions, the formation of the shell at the emulsion droplet interface is accelerated, forming a dense and robust shell that can suppress the leakage of the core component. Consequently, a silica capsule with a high encapsulation rate stably encapsulating organic compounds is obtained.

[0075] In the manufacturing method of the present invention, other anions besides sulfate ions, sulfite ions, and sulfonic acid ions may coexist in the emulsion system without hindering the effect of the present invention.

[0076] Compound (A) is selected from one or more of sulfuric acid, sulfurous acid, sulfonic acid compounds, and their salts.

[0077] Sulfonic acid compounds are organic compounds that have one or more sulfonic acid groups in their molecules. Specifically, examples include aromatic sulfonic acid compounds such as p-toluenesulfonic acid and benzenesulfonic acid, and aliphatic sulfonic acid compounds of methanesulfonic acid.

[0078] As a salt of compound (A), an inorganic salt is preferred. Examples include salts of alkali metals such as sodium and potassium, and salts of alkaline earth metals such as calcium and magnesium.

[0079] From the viewpoint of forming a dense and robust shell and stably encapsulating organic compounds with a high encapsulation rate, compound (A) is preferably selected from one or more of sulfuric acid, sulfurous acid, sulfonic acid compounds, and their inorganic salts, more preferably selected from one or more of sulfuric acid, sulfurous acid, p-toluenesulfonic acid, and their inorganic salts, even more preferably selected from one or more of sulfuric acid, sulfurous acid, and their inorganic salts, even more preferably selected from one or more of sulfuric acid and their inorganic salts, even more preferably selected from one or more of sulfuric acid, sodium sulfate, and magnesium sulfate, even more preferably selected from one or more of sulfuric acid and sodium sulfate, and even more preferably containing sulfuric acid or its salts.

[0080] Furthermore, it is believed that when compound (A) is selected from one or more of sulfuric acid, sulfurous acid, and sulfonic acid compounds, it can also function as an acid catalyst for the sol-gel reaction, accelerating the formation of the shell on the interface of the emulsion droplets, forming a dense and strong shell that can suppress the leakage of the core component, and obtaining a silica capsule that stably encapsulates organic compounds with a high encapsulation rate.

[0081] Regarding compound (A), one type can be used alone or in combination of two or more types.

[0082] Regarding the amount of compound (A) used in the manufacturing method of the present invention, from the viewpoint of forming a dense and robust shell and stably encapsulating organic compounds with a high encapsulation rate, the molar ratio of the total molar amount of sulfur-containing ions to the molar amount of the balance ions of the cationic groups of the cationic surfactant [sulfur-containing ions / balance ions of cationic groups] is preferably 0.01 or more, more preferably 0.03 or more, even more preferably 0.05 or more, and preferably 2 or less, more preferably 1.5 or less, even more preferably 1.0 or less, even more preferably 0.7 or less, even more preferably 0.5 or less, even more preferably 0.3 or less, even more preferably 0.2 or less, even more preferably 0.1 or less, and even more preferably 0.07 or less.

[0083] It should be noted that when calculating the above molar ratio [sulfide ion / equilibrium ion of cationic group], if there are two or more sulfur-containing ions, the molar amount of sulfur-containing ions is their total molar amount. In addition, if there are two or more equilibrium ions of cationic groups, the molar amount of equilibrium ions of cationic groups is their total molar amount.

[0084] Furthermore, when compound (A) functions as an acid catalyst, from the viewpoint of forming a dense and robust shell and stably encapsulating organic compounds with a high encapsulation rate, the amount of compound (A) used in the manufacturing method of the present invention is preferably added in a manner that corresponds to the initial pH range of the sol-gel reaction described later.

[0085] In this invention, from the viewpoint of forming a dense and robust shell and stably encapsulating organic compounds with a high encapsulation rate, the molar ratio of the total molar amount of sulfur-containing ions to the molar amount of halide ions in the system [sulfur-containing ions / halide ions] is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and preferably 0.3 or less, more preferably 0.15 or less, even more preferably 0.1 or less, and even more preferably 0.07 or less.

[0086] The halide ions here include chloride ions, bromide ions, iodide ions, etc.

[0087] It should be noted that when calculating the above molar ratio [sulfide ion / halide ion], if there are two or more sulfur-containing ions, the molar amount of sulfur-containing ions is their total molar amount. In addition, if there are two or more halide ions, the molar amount of halide ions is their total molar amount.

[0088] (sol-gel reaction)

[0089] In this invention, an emulsion is subjected to a sol-gel reaction in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions to form a silica capsule having a shell composed of silica and a core containing the aforementioned organic compound inside the shell, thereby obtaining an aqueous dispersion containing the silica capsule.

[0090] The above sol-gel reaction is preferably carried out under acidic conditions.

[0091] From the viewpoint of maintaining the balance between the hydrolysis and condensation reactions of the shell source, and from the viewpoint of suppressing the formation of highly hydrophilic sols and promoting encapsulation, the initial pH of the above-mentioned sol-gel reaction is preferably 3.0 or higher, more preferably 3.3 or higher, and even more preferably 3.5 or higher. Moreover, from the viewpoint of suppressing the simultaneous formation of the shell and the coagulation of emulsion droplets to obtain silica capsules with a dense and firm shell, it is preferably 4.5 or lower, more preferably 4.3 or lower, and even more preferably 4.1 or lower.

[0092] In order to adjust the initial pH of the above sol-gel reaction to the desired range, it is preferable to add any acidic or alkaline pH adjuster to the emulsion according to the pH shown by the emulsion corresponding to the strength of acidity and alkalinity of the oil phase component containing the above organic compounds.

[0093] If the pH of the emulsion is below the desired value, it is preferable to use an alkaline pH adjuster for adjustment.

[0094] When the pH of the emulsion is above the desired value, it is preferable to use an acidic pH adjuster for adjustment.

[0095] Compound (A) can be added as a pH adjuster, but acidic pH adjusters other than compound (A) can also be used. Examples of such pH adjusters include: inorganic acids such as hydrochloric acid and nitric acid; organic acids such as citric acid; and liquids in which cation exchange resins have been added to water or ethanol.

[0096] Examples of alkaline pH adjusters include: hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide; bicarbonates of alkali metals such as sodium bicarbonate; ammonia; ammonium hydroxide; and organic amines such as diethanolamine, triethanolamine, and tris(hydroxymethyl)aminomethane. Preferably, one or more of sodium hydroxide and ammonium hydroxide are selected.

[0097] Regarding the pH adjusters mentioned above, one or more can be used alone.

[0098] In this invention, from the viewpoint of ease of manufacture, it is preferable to use compound (A) as an acidic pH adjuster. In this case, compound (A) is more preferably selected from sulfuric acid, sulfurous acid, and p-toluenesulfonic acid, further preferably selected from sulfuric acid and sulfurous acid, and even more preferably sulfuric acid.

[0099] It should be noted that in this invention, even when inorganic salts such as hydrochloric acid and nitric acid, or organic acids such as citric acid, other than compound (A) are used as acidic pH adjusters, by adding sodium sulfate, magnesium sulfate, or the like as compound (A), it is possible to prepare the same suitable sol-gel reaction conditions as when a substance with the function of a pH adjuster, such as sulfuric acid, is used as compound (A).

[0100] Regarding the reaction temperature of the sol-gel reaction described above, any value can be selected as long as it is above the melting point and below the boiling point of the water contained as the dispersion medium. From the viewpoint of controlling the balance between hydrolysis and condensation reactions in the sol-gel reaction, forming a dense and firm shell, and stably encapsulating organic compounds with a high encapsulation rate, it is preferable to be 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and preferably 60°C or lower, more preferably 50°C or lower, and even more preferably adjusted to 40°C or lower.

[0101] In this invention, the silica capsules obtained through step I described above are in the form of an aqueous dispersion containing silica capsules dispersed in water. The silica capsules obtained through step I are silica capsules with a single-shell structure.

[0102] Furthermore, this invention may also include the following step (hereinafter also referred to as "Step II"): further adding a silica source to the aqueous dispersion containing silica capsules obtained in Step I, performing a sol-gel reaction, and forming a silica capsule having a shell that further encapsulates the silica capsule. It is considered that: through Step II, a shell is further formed on the silica capsule with a single-shell structure formed in Step I, and the silica capsule obtained in Step II becomes a silica capsule with a single-shell structure whose shell thickness is increased. Furthermore, it is also considered that: through Step II, a silica capsule with a double-shell structure is formed, wherein the shell formed in Step I is the inner shell, and the shell formed in Step II is the outer shell.

[0103] The temperature of the sol-gel reaction in step II can also be the same as that in step I.

[0104] The amount of silica source in step II is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to the amount of the organic compound. Moreover, from the viewpoint of suppressing the residue of silica source inside the oil phase droplets and effectively converting silica source to shell, it is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less.

[0105] From the viewpoint of reducing the number of manufacturing steps and efficiently manufacturing silica capsules that stably encapsulate organic compounds with a high encapsulation rate, the manufacturing method of the present invention preferably forms silica capsules only through step I.

[0106] Furthermore, from the viewpoint of improving the physical strength of the silica capsule and stably encapsulating organic compounds with a high encapsulation rate, the manufacturing method of the present invention preferably forms the silica capsule by performing steps I and II.

[0107] [Aqueous dispersion containing silica microcapsules]

[0108] The silica microcapsules (silica capsules) of the present invention have a shell containing silica as a constituent component and a core containing one or more organic compounds inside the shell. The silica microcapsules are obtained in the form of an aqueous dispersion containing silica capsules dispersed in water.

[0109] In this invention, depending on the intended use of the silica capsules, they can be used directly as an aqueous dispersion. However, depending on the intended use of the silica capsules, they can also be used after being separated from the aqueous dispersion. Separation methods include filtration and centrifugation.

[0110] From the viewpoint of stably encapsulating organic compounds with a high encapsulation rate, the total content of sulfate ions, sulfite ions, and sulfonic acid ions (total content of sulfur ions) in the aqueous dispersion containing the silica microcapsules of the present invention is preferably 10 ppm or more, more preferably 13 ppm or more, even more preferably 15 ppm or more, and preferably 500 ppm or less, more preferably 450 ppm or less, even more preferably 400 ppm or less, even more preferably 200 ppm or less, even more preferably 100 ppm or less, even more preferably 70 ppm or less, even more preferably 50 ppm or less, and even more preferably 30 ppm or less.

[0111] The total content of sulfur ions in the aqueous dispersion of silica microcapsules can be determined quantitatively using ion chromatography. Alternatively, it can be calculated based on the proportions of each component.

[0112] From the viewpoint of stably encapsulating organic compounds with a high encapsulation rate, the average thickness of the shell of the silica capsule of the present invention is preferably 5 nm or more, more preferably 10 nm or more, and preferably 100 nm or less, more preferably 70 nm or less, even more preferably 50 nm or less, even more preferably 30 nm or less, and even more preferably 20 nm or less.

[0113] The average thickness of the aforementioned shell can be determined by observation using a transmission electron microscope (TEM). Specifically, the shell thickness is measured on a photograph under TEM observation. This operation is performed by changing the field of view. The distribution of the average shell thickness is obtained based on the obtained data. The magnification of the TEM is typically between 10,000 and 100,000 times, but is appropriately adjusted according to the size of the silica capsule. Here, for example, the TEM can be the trade name "JEM-2100" (manufactured by Nippon Electronics Co., Ltd.).

[0114] From the viewpoint of improving the dispersion stability of silica capsules and stably encapsulating organic compounds with a high encapsulation rate, the median particle size D of the silica capsules of the present invention is... 50 Preferably, the micrometer is 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. Furthermore, from the viewpoint of improving the physical strength of the silica capsule and stably encapsulating organic compounds with a high encapsulation rate, it is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, even more preferably 5 μm or less, and even more preferably 3 μm or less.

[0115] The median particle size D of the above-mentioned silica capsules 50 It can be determined by the methods described in the examples.

[0116] The silica capsules and aqueous dispersions containing silica capsules of the present invention can be used for various purposes, such as emulsions, lotions, toners, beauty serums, creams, gels, hair treatment agents, quasi-pharmaceuticals and other cosmetics, cleansers, softeners, anti-wrinkle sprays and other fiber treatment agents, diapers and other hygiene products, fragrances and other uses.

[0117] Regarding the above-described embodiments, the present invention also discloses the following method for manufacturing silica microcapsules and an aqueous dispersion containing silica microcapsules.

[0118] <1> A method for manufacturing silica microcapsules, wherein,

[0119] The silica microcapsules have: a shell containing silica as a constituent component; and a core containing one or more organic compounds inside the shell.

[0120] The method for manufacturing the silica microcapsules includes the following steps: in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions, an emulsion is fed into a sol-gel reaction to form silica microcapsules, wherein the emulsion is obtained by emulsifying an aqueous phase component containing a cationic surfactant and an oil phase component containing one or more organic compounds and a silica source.

[0121] <2> According to the method for manufacturing silica microcapsules described in <1> above, the sulfur-containing ion is preferably selected from one or more of sulfate ions, sulfite ions, aromatic sulfonic acid ions, and aliphatic sulfonic acid ions, more preferably selected from one or more of sulfate ions, sulfite ions, and p-toluenesulfonate anions, further preferably selected from one or more of sulfate ions and sulfite ions, and even more preferably sulfate ions.

[0122] <3> According to the method for manufacturing silica microcapsules described in <1> or <2> above, in the step of forming silica microcapsules, after adding one or more compounds (A) selected from sulfuric acid, sulfurous acid, sulfonic acid compounds and their salts to the emulsion, it is subjected to a sol-gel reaction.

[0123] <4> According to the method for manufacturing silica microcapsules described in <3> above, the compound (A) is preferably selected from one or more of sulfuric acid, sulfurous acid, sulfonic acid compounds and their inorganic salts, more preferably selected from one or more of sulfuric acid, sulfurous acid, p-toluenesulfonic acid and their inorganic salts, even more preferably selected from one or more of sulfuric acid, sulfurous acid and their inorganic salts, even more preferably selected from one or more of sulfuric acid and its inorganic salts, even more preferably selected from one or more of sulfuric acid, sodium sulfate and magnesium sulfate, even more preferably selected from one or more of sulfuric acid and sodium sulfate, and even more preferably containing sulfuric acid or its salts.

[0124] <5> According to the method for manufacturing silica microcapsules described in <3> or <4> above, the amount of the compound (A) is preferably 0.01 or more, more preferably 0.03 or more, further preferably 0.05 or more, and preferably 2 or less, more preferably 1.5 or less, further preferably 1.0 or less, even more preferably 0.7 or less, even more preferably 0.5 or less, even more preferably 0.3 or less, even more preferably 0.2 or less, even more preferably 0.1 or less, and even more preferably 0.07 or less.

[0125] <6> According to any one of <1> to <5> above, in the method for manufacturing silica microcapsules, from the viewpoint of forming a dense and robust shell and stably encapsulating organic compounds with a high encapsulation rate, the molar ratio of the total molar amount of sulfur-containing ions to the molar amount of halide ions [sulfur-containing ions / halide ions] is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and preferably 0.3 or less, more preferably 0.15 or less, even more preferably 0.1 or less, and even more preferably 0.07 or less.

[0126] <7> The method for manufacturing silica microcapsules according to any one of <1> to <6> above, wherein the silica source comprises tetraalkoxysilane as the main component.

[0127] <8> The method for manufacturing silica microcapsules according to any one of <7> above, wherein the content of tetraalkoxysilane in the silica source is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less.

[0128] <9> The method for manufacturing silica microcapsules according to any one of <1> to <8> above, wherein the amount of the silica source relative to the amount of the organic compound is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and preferably 100% by mass or less, more preferably 70% by mass or less, even more preferably 50% by mass or less, and even more preferably 30% by mass or less.

[0129] <10> The method for manufacturing silica microcapsules according to any one of <1> to <9> above, wherein the cationic surfactant is preferably a quaternary ammonium salt, more preferably an alkyltrimethylammonium salt having an alkyl group having 10 to 22 carbon atoms, even more preferably an alkyltrimethylammonium halide having an alkyl group having 10 to 22 carbon atoms, even more preferably an alkyltrimethylammonium chloride having an alkyl group having 10 to 22 carbon atoms, even more preferably one or more selected from lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, and hexadecyltrimethylammonium chloride, and even more preferably hexadecyltrimethylammonium chloride.

[0130] <11> The method for manufacturing silica microcapsules according to any one of <1> to <10> above, wherein the amount of the cationic surfactant relative to the amount of the organic compound is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.7% by mass or less.

[0131] <12> According to the method for manufacturing silica microcapsules described in any one of <1> to <11> above, wherein the median particle size D of the emulsion droplets of the emulsion is... 50 Preferably, the micrometer is 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, even more preferably 0.5 μm or more, and preferably 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, even more preferably 5 μm or less, even more preferably 3 μm or less, and even more preferably 2 μm or less.

[0132] <13> The method for manufacturing silica microcapsules according to any one of <1> to <12> above, wherein the stirring device used in the emulsification of the aqueous phase component and the oil phase component is a homogenizer, a high-pressure disperser, or an ultrasonic disperser.

[0133] <14> The method for manufacturing silica microcapsules according to any one of <1> to <13> above, wherein the initial pH of the sol-gel reaction is preferably 3.0 or higher, more preferably 3.3 or higher, even more preferably 3.5 or higher, and preferably 4.5 or lower, more preferably 4.3 or lower, even more preferably 4.1 or lower.

[0134] <15> The method for manufacturing silica microcapsules according to any one of <1> to <14> above, wherein the reaction temperature of the sol-gel reaction is preferably 5°C or higher, more preferably 10°C or higher, even more preferably 15°C or higher, and preferably 60°C or lower, more preferably 50°C or lower, even more preferably 40°C or lower.

[0135] <16> The method for manufacturing silica microcapsules according to any one of <1> to <15> above, wherein the cLogP value of the organic compound is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and preferably 30 or less, more preferably 20 or less, even more preferably 10 or less.

[0136] <17> The method for manufacturing silica microcapsules according to any one of <1> to <16> above, wherein the organic compound is preferably selected from one or more of fragrances, fragrance precursors, oils (humectants), antioxidants, antibacterial agents, fertilizers, fibers, skin, and hair surface modifiers, cooling agents, dyes, pigments, silicones, solvents, and oil-soluble polymers; more preferably selected from one or more of fragrances, fragrance precursors, oils (humectants), antioxidants, antibacterial agents, fertilizers, surface modifiers, and solvents; even more preferably selected from one or more of fragrances, fragrance precursors, humectants, antioxidants, and solvents; even more preferably selected from one or more of fragrances, fragrance precursors, and oils; and even more preferably selected from one or more of fragrances and fragrance precursors.

[0137] <18> According to any one of <1> to <17> above, the method for manufacturing silica microcapsules, wherein the median particle size D of the silica microcapsules is... 50 Preferably, the micrometer is 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, and preferably 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, even more preferably 5 μm or less, and even more preferably 3 μm or less.

[0138] <19> A method for manufacturing silica microcapsules, wherein,

[0139] The silica microcapsule has: a shell containing silica as a constituent component; and a core containing one or more organic compounds inside the shell.

[0140] The method for manufacturing the aforementioned silica microcapsules includes the following steps: supplying an emulsion to a sol-gel reaction to form silica microcapsules in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions.

[0141] The emulsion described above is obtained by emulsifying an aqueous phase and an oil phase. The aqueous phase contains a quaternary ammonium salt as a cationic surfactant, and the oil phase contains one or more organic compounds and a silica source containing a tetraalkoxysilane as the main component.

[0142] The aforementioned organic compounds are selected from one or more of the fragrances and fragrance precursors.

[0143] <20> According to the method for manufacturing silica microcapsules described in <19> above, in the process of forming silica microcapsules, after adding one or more compounds (A) selected from sulfuric acid, sulfurous acid, sulfonic acid compounds and their salts to the emulsion, it is subjected to a sol-gel reaction.

[0144] <21> According to the method for manufacturing silica microcapsules described in <20> above, the amount of the compound (A) is preferably 0.01 or more, more preferably 0.03 or more, further preferably 0.05 or more, and preferably 2 or less, more preferably 1.5 or less, further preferably 1.0 or less, even more preferably 0.7 or less, even more preferably 0.5 or less, even more preferably 0.3 or less, even more preferably 0.2 or less, even more preferably 0.1 or less, and even more preferably 0.07 or less.

[0145] <22> The method for manufacturing silica microcapsules according to any one of <19> to <21> above, wherein the cLogP value of the organic compound is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, and preferably 30 or less, more preferably 20 or less, even more preferably 10 or less.

[0146] <23> According to the method for manufacturing silica microcapsules described in any one of <19> to <22> above, wherein the median particle size D of the emulsion droplets of the emulsion is... 50 Preferably, the micrometer is 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, even more preferably 0.5 μm or more, and preferably 50 μm or less, more preferably 30 μm or less, even more preferably 10 μm or less, even more preferably 5 μm or less, even more preferably 3 μm or less, and even more preferably 2 μm or less.

[0147] <24> The method for manufacturing silica microcapsules according to any one of <19> to <23> above, wherein the initial pH of the sol-gel reaction is preferably 3.0 or higher, more preferably 3.3 or higher, even more preferably 3.5 or higher, and preferably 4.5 or lower, more preferably 4.3 or lower, even more preferably 4.1 or lower.

[0148] <25> An aqueous dispersion, wherein,

[0149] The product contains silica microcapsules, which have a shell containing silica as a constituent component and a core containing one or more organic compounds inside the shell.

[0150] The total content of sulfate ions, sulfite ions, and sulfonic acid ions (total content of sulfur ions) in the aqueous dispersion containing silica microcapsules is preferably 10 ppm or more, more preferably 13 ppm or more, even more preferably 15 ppm or more, and preferably 500 ppm or less, more preferably 450 ppm or less, even more preferably 400 ppm or less, even more preferably 200 ppm or less, even more preferably 100 ppm or less, even more preferably 70 ppm or less, even more preferably 50 ppm or less, and even more preferably 30 ppm or less. (10 ppm or more, 500 ppm or less)

[0151] [Example]

[0152] The various measurements used in the examples and comparative examples were performed by the following methods.

[0153] [Median particle size D] 50 ]

[0154] Regarding the median droplet size D of the emulsion... 50 and the median particle size D of silica capsules 50 The particle size distribution was measured using a laser diffraction / scattering particle size distribution measuring device, "LA-960" (trade name, manufactured by Horiba Manufacturing Co., Ltd.). During the measurement, a flow cell was used, with water as the medium and the refractive index set to 1.45-0i. An emulsion or an aqueous dispersion containing silica capsules was added to the flow cell, and the concentration was measured at approximately 90% transmittance. The median particle size D was determined on a volume basis. 50 .

[0155] <Model Spice A>

[0156] As the organic compound encapsulated in a silica capsule, model fragrance A (volume-average cLogP value: 4.3) with the composition shown in Table 1 was used. It should be noted that the volume-average cLogP value of the above-mentioned model fragrance is calculated by multiplying the cLogP values ​​of all the fragrance components contained in the model fragrance by the volume ratio of each component in the model fragrance, and then summing them.

[0157] [Table 1]

[0158] Table 1: Model Fragrance A

[0159] Flavor ingredient name Content (mass%) cLogP Linalool 22 3.3 Linaloyl acetate 16 4.4 Tetrahydrolinalool 16 3.6 other 46

[0160] Example 1

[0161] (Process I)

[0162] Aqueous phase was prepared by diluting 0.30 g of QUARTAMIN 60W (trade name: Kao Corporation; cetyltrimethylammonium chloride (hereinafter referred to as "CTAC"), active ingredient 30% by mass) with 74.70 g of ion-exchanged water. An oil phase was prepared by mixing 20 g of model fragrance A and 5 g of tetraethoxysilane (hereinafter referred to as "TEOS") with this aqueous phase. The mixture was emulsified using a homogenizer (manufactured by HsiangTai Co., Ltd., model: HM-310) set to 7,000 rpm to obtain emulsion (1). The median droplet diameter D of the emulsion at this time was... 50 It is 1.1 μm.

[0163] Next, 0.16 g of 1% sulfuric acid aqueous solution was added to the obtained emulsion (1) to obtain an emulsion (1') with pH adjusted to 3.8. This emulsion (1') was then transferred to a separating flask equipped with stirring blades, and the liquid temperature was maintained at 30°C while stirring at 200 rpm for 24 hours to obtain an aqueous dispersion (I) containing silica capsules (the silica capsules having a core composed of model fragrance A and a shell composed of silica). The median particle size D of the obtained silica capsules was... 50 It is 2.1 μm.

[0164] Example 2

[0165] (Process I)

[0166] The process was carried out in the same manner as in Example 1, resulting in an emulsion (1).

[0167] Next, 0.29 g of 1% sulfurous acid aqueous solution was added to the obtained emulsion (1) to obtain an emulsion (2') with pH adjusted to 3.8. This emulsion (2') was then transferred to a separating flask equipped with stirring blades, and the liquid temperature was maintained at 30°C while stirring at 200 rpm for 24 hours to obtain an aqueous dispersion (II) containing silica capsules (the silica capsules having a core composed of model fragrance A and a shell composed of silica). The median particle size D of the silica capsules... 50 It is 2.2 μm.

[0168] Example 3

[0169] (Process I)

[0170] The process was carried out in the same manner as in Example 1, resulting in an emulsion (1).

[0171] Next, 0.41 g of 1% p-toluenesulfonic acid aqueous solution was added to the obtained emulsion (1) to obtain an emulsion (3') with pH adjusted to 3.7. This emulsion (3') was then transferred to a separating flask equipped with a stirring blade, and the liquid temperature was maintained at 30°C while stirring at 200 rpm for 24 hours to obtain an aqueous dispersion (III) containing silica capsules (the silica capsules having a core composed of model fragrance A and a shell composed of silica). The median particle size D of the silica capsules... 50 It is 2.1 μm.

[0172] Example 4

[0173] (Process I)

[0174] The process was carried out in the same manner as in Example 1, resulting in an emulsion (1).

[0175] Next, 0.29 g of 1% sodium sulfate aqueous solution was added to the obtained emulsion (1), followed by 0.1 N hydrochloric acid aqueous solution to adjust the pH to 3.8, resulting in emulsion (4'). This emulsion (4') was then transferred to a separating flask equipped with stirring blades, and the liquid temperature was maintained at 30°C while stirring at 200 rpm for 24 hours to obtain an aqueous dispersion (IV) containing silica capsules (the silica capsules having a core composed of model fragrance A and a shell composed of silica). The median particle size D of the silica capsules... 50 It is 2.2 μm.

[0176] Example 5

[0177] (Process I)

[0178] The same procedure was performed as in Example 1 to obtain 100.16 g of an aqueous dispersion (I) containing silica capsules.

[0179] (Process II)

[0180] Next, for 13.00 g of the aqueous dispersion (I), 0.40 g of TEOS was added over 10 seconds, and the liquid temperature was maintained at 30°C while stirring for 24 hours. The mixture was then cooled to room temperature, thereby forming a second shell encapsulating the aforementioned silica capsules, resulting in an aqueous dispersion (V) containing silica capsules (in which model fragrance A is encapsulated by amorphous silica). The median particle size D of the silica capsules is... 50 It is 2.1 μm.

[0181] Example 6

[0182] (Process I)

[0183] The same procedure was performed as in Example 4, and 100.29 g of an aqueous dispersion (IV) containing silica capsules was obtained.

[0184] (Process II)

[0185] Next, for 13.00 g of the aqueous dispersion (IV), 0.39 g of TEOS was added over 10 seconds, and the liquid temperature was maintained at 30°C while stirring for 24 hours. The mixture was then cooled to room temperature, thereby forming a second shell encapsulating the aforementioned silica capsules, resulting in an aqueous dispersion (VI) containing silica capsules (in which model fragrance A is encapsulated by amorphous silica). The median particle size D of these silica capsules... 50 It is 2.2 μm.

[0186] Comparative Example 1

[0187] (Process I')

[0188] The process was carried out in the same manner as in Example 1, resulting in an emulsion (1).

[0189] Next, 0.1N hydrochloric acid aqueous solution was added to the obtained emulsion (1) to obtain an emulsion (C1') with pH adjusted to 3.8. This emulsion (C1') was then transferred to a separating flask equipped with a stirring blade, and the liquid temperature was maintained at 30°C while stirring at 200 rpm for 24 hours to obtain an aqueous dispersion (CI) containing silica capsules (the silica capsules having a core composed of model fragrance A and a shell composed of silica). The median particle size D of the silica capsules... 50 It is 2.1 μm.

[0190] Comparative Example 2

[0191] (Process I')

[0192] The process was carried out in the same manner as in Example 1, resulting in an emulsion (1).

[0193] Next, 1% by mass of nitric acid aqueous solution was added to the obtained emulsion (1) to obtain an emulsion (C2') with pH adjusted to 3.8. This emulsion (C2') was then transferred to a separating flask equipped with stirring blades, and the liquid temperature was maintained at 30°C while stirring at 200 rpm for 24 hours to obtain an aqueous dispersion (CII) containing silica capsules (the silica capsules having a core composed of model fragrance A and a shell composed of silica). The median particle size D of the silica capsules... 50 It is 2.2 μm.

[0194] Comparative Example 3

[0195] (Process I')

[0196] The process was carried out in the same manner as in Example 1, resulting in an emulsion (1).

[0197] Next, 10% by mass of citric acid aqueous solution was added to the obtained emulsion (1) to obtain an emulsion (C3') with pH adjusted to 3.8. This emulsion (C3') was then transferred to a separating flask equipped with a stirring blade, and the liquid temperature was maintained at 30°C while stirring at 200 rpm for 24 hours to obtain an aqueous dispersion (CIII) containing silica capsules (the silica capsules having a core composed of model fragrance A and a shell composed of silica). The median particle size D of the silica capsules... 50 It is 2.1 μm.

[0198] [Evaluation of silica capsules]

[0199] [Evaluation of the encapsulation rate of fragrance components]

[0200] Using a dropper, 30 mg of the aqueous dispersion containing silica capsules obtained in Examples 1-6 and Comparative Examples 1-3 was drawn up, diluted with 50 g of ion-exchanged water, and then passed through a membrane filter (Millipore, product name "Omnipore", model "JAWP04700"). Thus, the silica capsules were recovered on the membrane filter.

[0201] Furthermore, the silica capsules were rinsed with 10 mL of deionized water and then with 10 mL of hexane on a membrane filter. The silica capsules were then immersed in 10 mL of acetonitrile containing dodecane at a concentration of 20 μg / mL, serving as an internal standard. The solution was then irradiated with ultrasound for 60 minutes using a Branson ultrasonic irradiation device (model "5510") at an output of 180 W and an oscillation frequency of 42 kHz to dissolve the fragrance from the silica capsules. This solution was then passed through a membrane filter (manufactured by Toyo Filter Paper Co., Ltd., product name "DISMIC", model "13JP020AN"), and the amount of each fragrance component contained in the solution was determined by gas chromatography, and denoted as α, the amount of each fragrance component encapsulated in the silica capsules. The encapsulation rate of the fragrance components was then calculated using the following formula. The results are shown in Table 2 below.

[0202] Encapsulation rate of fragrance components (%) = {(Amount of each fragrance component encapsulated in the silica capsule α) / (Amount of each fragrance component contained in 30mg of the aqueous dispersion of the silica capsule β)} × 100

[0203] It should be noted that the amount β of the fragrance component in the above formula is calculated based on the composition of the model fragrance used and the content in the aqueous dispersion containing silica capsules.

[0204]

[0205] As shown in Table 2, the silica capsules obtained in the examples have a higher encapsulation rate of fragrance components compared to the comparative examples. Furthermore, it can be seen that the silica capsules obtained in the examples, despite undergoing filtration during the evaluation of encapsulation rate, maintain a high encapsulation rate and can stably encapsulate the fragrance components.

[0206] [Industry availability]

[0207] According to the present invention, silica capsules that stably encapsulate active ingredients such as fragrances, i.e., organic compounds, with a high encapsulation rate can be obtained. Therefore, the silica capsules and aqueous dispersions containing silica capsules can be well applied to the formulation of various products containing active ingredients such as fragrances.

Claims

1. A method for manufacturing silica microcapsules, wherein, The silica microcapsules have: a shell containing silica as a constituent component; and a core containing one or more organic compounds inside the shell. The method for manufacturing the silica microcapsules includes the following steps: supplying an emulsion to a sol-gel reaction to form silica microcapsules in the presence of one or more sulfur-containing ions selected from sulfate ions, sulfite ions, and sulfonic acid ions. The emulsion is obtained by emulsifying an aqueous phase component containing a cationic surfactant and an oil phase component containing one or more organic compounds and a silica source. The amount of sulfur-containing ions is defined as the molar ratio of the total molar amount of sulfur-containing ions to the molar amount of the balance ions of the cationic groups of the cationic surfactant, i.e., sulfur-containing ions / balance ions of cationic groups, which is 0.01 to 2.

2. The method for manufacturing silica microcapsules according to claim 1, wherein, In the process of forming silica microcapsules, one or more compounds (A) selected from sulfuric acid, sulfurous acid, sulfonic acid compounds and their salts are added to the emulsion and then subjected to a sol-gel reaction.

3. The method for manufacturing silica microcapsules according to claim 2, wherein, The compound (A) is selected from one or more of sulfuric acid, sulfurous acid, sulfonic acid compounds, and their inorganic salts.

4. The method for manufacturing silica microcapsules according to any one of claims 1 to 3, wherein, The amount of the silica source is more than 10% by mass and less than 100% by mass relative to the amount of the organic compound.

5. The method for manufacturing silica microcapsules according to any one of claims 1 to 3, wherein, The cationic surfactant is an alkyltrimethylammonium salt having an alkyl group having 10 to 22 carbon atoms.

6. The method for manufacturing silica microcapsules according to any one of claims 1 to 3, wherein, The median particle size D of the emulsion droplets of the emulsion. 50 The range is from 0.1μm to 10μm.

7. The method for manufacturing silica microcapsules according to any one of claims 1 to 3, wherein, The initial pH of the sol-gel reaction is above 3.0 and below 4.

5.

8. The method for manufacturing silica microcapsules according to any one of claims 1 to 3, wherein, The organic compound is selected from one or more of the following: fragrances, fragrance precursors, humectants, antioxidants, antibacterial agents, fertilizers, surface modifiers, and solvents.

9. The method for manufacturing silica microcapsules according to any one of claims 1 to 3, wherein, The silica source contains tetraalkoxysilane as the main component.

10. An aqueous dispersion, wherein, Containing silica microcapsules prepared by the method for manufacturing silica microcapsules according to any one of claims 1 to 9. The silica microcapsule has: a shell containing silica as a constituent component; and a core containing one or more organic compounds inside the shell. The total content of sulfate ions, sulfite ions, and sulfonic acid ions in the aqueous dispersion is between 10 ppm and 70 ppm.

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