Continuous production method of silica capsule particles including oil

Abstract

To provide a continuous production method of silica capsule particles including an oil, where the capsule particles show a high inclusion rate of the oil even when producing the silica capsule particles including an oil in the same reaction vessel.SOLUTION: A method for producing silica capsule particles including an oil, the particle comprising a core including the oil and a shell including silica as a constitutional component, comprises repeating the following steps 1-3 continuously in the same reaction vessel, wherein the content of silica solid particles in an emulsion obtained in step 1 is 0.5 mass% or less: step 1 of emulsifying an aqueous phase comprising a dispersant and water and an oil phase comprising an oil and a silica precursor to obtain an emulsion: step 2 of forming silica capsule particles including an oil and having a first shell by using the emulsion obtained in step 1; and step 3 of taking out the silica capsule particles including an oil, formed in step 2, from the reaction vessel.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for continuously producing silica capsule particles containing an oil agent.

Background Art

[0002] Conventionally, attempts have been made to sustain the effects by incorporating silica capsule particles containing an oil agent, which is obtained by encapsulating an oil agent such as a fragrance or a medicinal ingredient, into a product. In particular, fiber treatment products, cosmetics, detergents, etc. are required to have a high-performance product with a long-lasting fragrance because imparting a fragrance to clothing and the body is one of the important performances. Under such circumstances, the synthesis of silica capsule particles containing an oil agent by the sol-gel method has been studied.

[0003] For example, Patent Document 1 discloses a method for producing microcapsules having a first shell and a second shell containing silica as a constituent component and a core containing one or more organic compounds inside the first shell, with the problem of retaining an organic compound, which is an active ingredient such as an encapsulated fragrance, for a long period of time.

[0004] Patent Document 2 discloses a method for producing capsules containing a substantially inorganic shell surrounding an oily core, the method including a step of mixing an oil phase containing a beneficial agent and a precursor with an aqueous phase containing water and inorganic nanoparticles, a step of emulsifying the mixture of the oil phase and the aqueous phase under conditions sufficient to disperse droplets of the oil phase in the aqueous phase, and a step in which the nanoparticles self-assemble around the oil droplets, intervene at the interface between the aqueous phase and the oil phase, and the precursor from the oil phase undergoes hydrolysis and condensation at the interface between the oil phase and the aqueous phase.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, it has been found that when oil-containing silica capsule particles are continuously produced in the same reaction tank, the oil cannot be sufficiently encapsulated, and the encapsulation rate of the oil may decrease. From the perspective of continuously producing oil-containing silica capsule particles in the same reaction tank, there was room for improvement in Patent Documents 1 and 2. Therefore, an object of the present invention is to provide a method for continuously producing oil-containing silica capsule particles with a high encapsulation rate of the oil even when the oil-containing silica capsule particles are continuously and repeatedly produced in the same reaction tank.

Means for Solving the Problems

[0007] The present inventors have found that, in a method for continuously producing oil-containing silica capsule particles in the same reaction tank, the above problems can be solved by setting the content of silica solid particles in the emulsion obtained by emulsifying the aqueous phase and the oil phase within a specific range. That is, the present invention is a method for producing oil-containing silica capsule particles having a core containing an oil agent and a shell containing silica as a constituent component, wherein the following steps 1 to 3 are continuously and repeatedly performed in the same reaction tank to produce oil-containing silica capsule particles, and the content of silica solid particles in the emulsion obtained in step 1 is 0.5% by mass or less. A method for continuously producing oil-containing silica capsule particles. Step 1: A step of emulsifying an aqueous phase containing a dispersant and water and an oil phase containing an oil agent and a silica precursor to obtain an emulsion Step 2: A step of forming oil-containing silica capsule particles having a first shell using the emulsion obtained in Step 1 Step 3: A step of taking out the oil-containing silica capsule particles formed in Step 2 from the reaction tank Here, the "silica solid particles" refer to those formed when the silica component deposited on the tank wall or stirring blades in the reaction tank exfoliates into the emulsion obtained in Step 1 during the continuous and repeated production process of the silica capsule particles containing an oil agent, and becomes silica solid particles by stirring or the like.

Advantages of the Invention

[0008] According to the present invention, even when continuously and repeatedly producing the silica capsule particles containing an oil agent in the same reaction tank, a continuous production method of silica capsule particles containing an oil agent with a high inclusion rate of the oil agent can be provided.

Embodiments for Carrying Out the Invention

[0009] [Definitions] In this specification, the "inclusion rate of the oil agent" means the ratio of the amount of the oil agent encapsulated in the silica capsule particles to the blending amount of the oil agent, and is specifically measured and calculated by the method described in the examples.

[0010] [Continuous Production Method of Silica Capsule Particles Containing an Oil Agent] The production method of the present invention is a method for producing silica capsule particles containing an oil agent (hereinafter, also simply referred to as "silica capsule particles") having a core containing an oil agent and a shell containing silica as a constituent component, and continuously repeats the following Steps 1 to 3 in the same reaction tank to produce silica capsule particles containing an oil agent, and the content of silica solid particles in the emulsion obtained in Step 1 is 0.5% by mass or less. A continuous production method of silica capsule particles containing an oil agent. Step 1: A step of emulsifying an aqueous phase containing a dispersant and water and an oil phase containing an oil agent and a silica precursor to obtain an emulsion Step 2: A step of forming silica capsule particles containing an oil agent having a first shell using the emulsion obtained in Step 1 Step 3: A step of taking out the silica capsule particles containing an oil agent formed in Step 2 from the reaction tank

[0011] According to the present invention, even if oil agent-containing silica capsule particles are continuously and repeatedly produced in the same reaction tank, a method for continuously producing oil agent-containing silica capsule particles with a high encapsulation rate of the oil agent can be provided. The reason is not necessarily clear, but it is considered as follows. In the present invention, in Step 1, an aqueous phase and an oil phase containing an oil agent and a silica precursor are emulsified to obtain an emulsion, and then, in Step 2, using the emulsion obtained in Step 1, oil agent-containing silica capsule particles having a first shell are formed, and in Step 3, the oil agent-containing silica capsule particles are taken out from the reaction tank. A series of treatment steps of Steps 1 to 3 are continuously repeated in the same reaction tank. When such a series of treatment steps of Steps 1 to 3 are continuously repeated in the same reaction tank, as the number of a series of treatment steps increases, a silica component accumulates on the tank wall and stirring blades in the reaction tank, and the silica component exfoliates into the emulsion obtained in Step 1 and is considered to become silica solid particles and be mixed in the emulsion by stirring or the like. Then, when the emulsion in which the silica solid particles are mixed is supplied to Step 2, the silica solid particles come into contact with and react with the silica precursor, so that the amount of the silica precursor that would originally be a raw material for forming the first shell decreases, and it becomes difficult to form a desired dense and strong shell, and it is considered that the encapsulation rate of the oil agent in the oil agent-containing silica capsule particles decreases. Thus, it is considered that when silica solid particles derived from the silica component deposited on the tank wall and stirring blades in the reaction tank are mixed in the emulsion obtained in Step 1, the formation of a desired shell is inhibited. Therefore, in the present invention, by setting the content of silica solid particles in the emulsion obtained in Step 1 to be equal to or less than a specific amount (0.5% by mass or less), even if oil agent-containing silica capsule particles are continuously and repeatedly produced in the same reaction tank, it is considered that oil agent-containing silica capsule particles with a high encapsulation rate of the oil agent can be obtained.

[0012] <Step 1> Step 1 is a step of emulsifying an aqueous phase containing a dispersant and water and an oil phase containing an oil agent and a silica precursor to obtain an emulsion.

[0013] In the present invention, a series of treatment steps of Steps 1 to 3 are continuously repeated in the same reaction tank. In the reaction vessel used in the present invention, it is preferable to be provided with a stirring device having a stirring blade. As the stirring blade, one or more selected from paddle blades, turbine blades, anchor blades, ribbon blades, and propellers are preferable.

[0014] In the present invention, from the viewpoint of increasing the encapsulation rate of the oil agent, the content of the silica solid particles in the emulsion obtained in Step 1 is 0.5% by mass or less, preferably 0.4% by mass or less, more preferably 0.3% by mass or less, still more preferably 0.2% by mass or less, and even more preferably 0.15% by mass or less. From the viewpoint of productivity, it is preferably 0.001% by mass or more. When the silica solid particles are mixed in the emulsion in an amount exceeding 0.5% by mass, the silica solid particles come into contact with the silica precursor and react, so that the amount of the silica precursor that would originally be a raw material for shell formation decreases, and it may be difficult to form a desired dense and strong shell. The content of the silica solid particles in the emulsion obtained in Step 1 can be measured by the method described in the examples.

[0015] (aqueous phase component) 〔Dispersant〕 Examples of the dispersant include surfactants and polymer dispersants. 〔Surfactant〕 From the viewpoint of increasing the encapsulation rate of the oil agent, the surfactant used as the aqueous phase component in Step 1 is preferably a cationic surfactant. Examples of the cationic surfactant include alkylamine salts and alkyl quaternary ammonium salts. The carbon number of the alkyl group of the alkylamine salt and the alkyl quaternary ammonium salt is preferably 10 or more, more preferably 12 or more, still more preferably 14 or more, and preferably 22 or less, more preferably 20 or less, still more preferably 18 or less. Examples of the alkylamine salt include alkylamine acetates such as laurylamine acetate and stearylamine acetate. Examples of the alkyl quaternary ammonium salt include alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkylbenzyldimethylammonium salts and the like.

[0016] Examples of the alkyltrimethylammonium salt include alkyltrimethylammonium chlorides such as lauryltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride; alkyltrimethylammonium bromides such as lauryltrimethylammonium bromide, cetyltrimethylammonium bromide, stearyltrimethylammonium bromide and the like. Examples of the dialkyldimethylammonium salt include dialkyldimethylammonium chlorides such as distearyldimethylammonium chloride; dialkyldimethylammonium bromides such as distearyldimethylammonium bromide and the like. Examples of the alkylbenzyldimethylammonium salt include alkylbenzyldimethylammonium chloride, alkylbenzyldimethylammonium bromide and the like. The cationic surfactant may be used alone or in combination of two or more.

[0017] Among these, the cationic surfactant is preferably a quaternary ammonium salt, more preferably an alkyltrimethylammonium salt having an alkyl group with 10 to 22 carbon atoms, still more preferably at least one selected from lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, and cetyltrimethylammonium chloride, and even more preferably cetyltrimethylammonium chloride.

[0018] [Polymeric dispersant] From the viewpoint of increasing the encapsulation rate of the oil agent, the polymeric dispersant used as the aqueous phase component in Step 1 is preferably a cationic polymer compound. Examples of the cationic polymer compound include, in addition to the quaternary ammonium base-containing polymer compound, a polymer compound having a nitrogen-based cation group, and a polymer compound that may become cationic by pH adjustment.

[0019] The cation group equivalent of the cationic polymer compound is preferably 1 meq / g or more, more preferably 3 meq / g or more, still more preferably 4.5 meq / g or more, and preferably 10 meq / g or less, more preferably 8 meq / g or less. The cationic polymer compound may contain an anion group. In that case, the anion group equivalent contained in the cationic polymer compound is preferably 3.5 meq / g or less, more preferably 2 meq / g or less, still more preferably 1 meq / g or less. In the present invention, the cation group equivalent of the cationic polymer compound is calculated based on the monomer composition.

[0020] Specific examples of the cationic polymer compound include polydiallyldimethylammonium chloride such as poly(diallyldimethylammonium chloride), poly(acrylic acid-co-diallyldimethylammonium chloride), poly(acrylamide-co-diallyldimethylammonium chloride), poly(acrylamide-co-acrylic acid-co-diallyldimethylammonium chloride) and its copolymers, poly(2-(methacryloyloxy)ethyltrimethylammonium chloride), polyethyleneimine, polyallylamine, cationized cellulose, cationized guar gum, cationized tara gum, cationized fenugreek gum, cationized locust bean gum, and the like. Among these, polydiallyldimethylammonium chloride and its copolymers are preferred, one or more selected from poly(diallyldimethylammonium chloride), poly(acrylic acid-co-diallyldimethylammonium chloride), and poly(acrylamide-co-acrylic acid-co-diallyldimethylammonium chloride) are more preferred, and poly(diallyldimethylammonium chloride) is still more preferred.

[0021] From the viewpoint of obtaining a stable emulsion, the amount of the dispersant used as the aqueous phase component in Step 1 is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, still more preferably 0.3 part by mass or more, and preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, and even more preferably 0.7 part by mass or less, based on 100 parts by mass of the oil agent used in Step 1.

[0022] [Water] As the water used as the aqueous phase component in Step 1, for example, one or more selected from ion-exchanged water and distilled water are preferably used.

[0023] From the viewpoint of obtaining a stable emulsion, the amount of the water used as the aqueous phase component in Step 1 is preferably 100 parts by mass or more, more preferably 130 parts by mass or more, still more preferably 150 parts by mass or more, and preferably 300 parts by mass or less, more preferably 250 parts by mass or less, still more preferably 200 parts by mass or less, based on 100 parts by mass of the oil agent used in Step 1.

[0024] (Oil phase component) [Oil agent] The oil agent used as the oil phase component in Step 1 becomes the encapsulated component of the obtained silica capsule particles. The oil agent is preferably one or more selected from fragrances, fragrance precursors, humectants, antioxidants, antibacterial agents, fertilizers, surface modifiers for fibers, skin, and hair, cooling agents, dyes, pigments, silicones, and oil-soluble polymers; more preferably one or more selected from fragrances, fragrance precursors, humectants, antioxidants, antibacterial agents, fertilizers, and surface modifiers; still more preferably one or more selected from fragrances, fragrance precursors, humectants, and antioxidants; even more preferably one or more selected from fragrances, fragrance precursors, and humectants; and even more preferably one or more selected from fragrances and fragrance precursors. The oil agent can be used alone or in combination of two or more.

[0025] Examples of the fragrance precursor include compounds that release fragrance components by reacting with water, compounds that release fragrance components by reacting with light, and the like. Examples of compounds that react with water to release fragrance components include silicate ester compounds having an alkoxy component derived from a fragrance alcohol, fatty acid ester compounds having an alkoxy component derived from a fragrance alcohol, acetal compounds or hemiacetal compounds obtained by the reaction of a carbonyl component derived from a fragrance aldehyde or a fragrance ketone with an alcohol compound, Schiff base compounds obtained by the reaction of a carbonyl component derived from a fragrance aldehyde or a fragrance ketone with a primary amine compound, hemiaminal compounds or hydrazone compounds obtained by the reaction of a carbonyl component derived from a fragrance aldehyde or a fragrance ketone with a hydrazine compound. Examples of compounds that react with light to release fragrance components include 2-nitrobenzyl ether compounds having an alkoxy component derived from a fragrance alcohol, α-ketoester compounds having a carbonyl component derived from a fragrance aldehyde or a fragrance ketone, and coumaric acid ester compounds having an alkoxy component derived from a fragrance alcohol. These fragrance precursors may be used as polymers such as reaction products of a part of the carboxy groups of polyacrylic acid and a fragrance alcohol.

[0026] The calculated value of the common logarithm "LogP" of the partition coefficient P(n-octanol / water) between n-octanol and water of the oil agent (hereinafter also referred to as "cLogP value") is preferably 1 or more, more preferably 2 or more, still more preferably 3 or more, and preferably 30 or less, more preferably 20 or less, still more preferably 10 or less, even more preferably 8 or less, even more preferably 6 or less, from the viewpoint of obtaining a stable emulsion. When the oil agent is composed of a plurality of constituent components, the cLogP value of the oil agent can be obtained by multiplying the cLogP value of each constituent component by the volume ratio of each constituent component and taking the sum thereof. When the cLogP value of the oil agent is 1 or more, the encapsulation rate of the oil agent into the obtained silica capsule particles can be increased in the sol-gel reaction of the silica precursor. Similarly, even when the oil agent is a fragrance composition composed of a plurality of fragrance components, the encapsulation rate of the fragrance composition into the obtained silica capsule particles can be increased by the cLogP value of the fragrance composition being 1 or more. Here, the cLogP value is "LogP (cLogP)" calculated by 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 the cLogP value calculated by the program CLOGP v4.01 can be used.

[0027] 〔Silica precursor〕 The silica precursor used as the oil-phase component in Step 1 preferably contains tetraalkoxysilane, more preferably tetraalkoxysilane having an alkoxy group with 1 to 4 carbon atoms, still more 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, from the viewpoint of suppressing the reaction of the silica precursor in Step 1, allowing emulsification to proceed rapidly, and increasing the encapsulation rate of the oil agent. When the silica precursor contains tetraalkoxysilane, it may contain trialkoxysilane such as triethoxysilane and trimethoxysilane, but the content of tetraalkoxysilane in the silica precursor is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and preferably 100% by mass or less.

[0028] From the perspective of forming a shell that can surround the emulsion droplets containing the oil agent, the amount of the silica precursor used as the oil phase component in Step 1 is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more, based on 100 parts by mass of the oil agent used in Step 1. And from the perspective of suppressing the residue of the silica precursor inside the emulsion droplets and promoting the conversion to the shell efficiently in the sol-gel reaction, it is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0029] As the oil phase components other than the oil agent and the silica precursor used in Step 1, an emulsification aid, a particle size stabilizer, etc. may be included.

[0030] 〔Emulsification Aid〕 As the emulsification aid, one or more selected from higher aliphatic alcohols having 6 or more carbon atoms, higher fatty acids having 6 or more carbon atoms, monoalkyl glyceryl ethers having an alkyl group having 6 or more carbon atoms, and amide compounds having an alkyl group having 8 or more carbon atoms are preferably mentioned. Since these emulsification aids have a long-chain aliphatic hydrocarbon group and a polar group, it is considered that they can rapidly promote emulsification while suppressing the reaction of the silica precursor during the emulsification of the aqueous phase component and the oil phase component in Step 1, and can increase the encapsulation rate of the oil agent. The emulsification aid can be used alone or in combination of two or more. From the perspective of suppressing the reaction of the silica precursor, rapidly promoting emulsification, and increasing the encapsulation rate of the oil agent, the molecular weight of the emulsification aid is preferably 500 or less, more preferably 450 or less, still more preferably 400 or less, even more preferably 350 or less, and preferably 150 or more.

[0031] From the viewpoint of suppressing the reaction of the silica precursor, promoting emulsification promptly, and increasing the encapsulation rate of the oil agent, the number of carbon atoms of the higher aliphatic alcohol is preferably 8 or more, more preferably 10 or more, still more preferably 12 or more, even more preferably 14 or more, and preferably 22 or less, more preferably 20 or less, still more preferably 18 or less. From the same viewpoint as above, the higher aliphatic alcohol is preferably a linear or branched higher aliphatic alcohol, more preferably a linear higher aliphatic primary alcohol. From the viewpoint of ease of handling, the higher aliphatic alcohol is preferably solid at normal temperature and normal pressure (for example, having a melting point of 30°C or higher). The melting point of the higher aliphatic alcohol is preferably 30°C or higher, more preferably 35°C or higher, still more preferably 40°C or higher, even more preferably 45°C or higher. Examples of the higher aliphatic primary alcohol include 2-ethylhexyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, oleyl alcohol, etc. Among them, it is preferably at least one selected from 2-ethylhexyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol, more preferably at least one selected from cetyl alcohol and stearyl alcohol, and still more preferably cetyl alcohol.

[0032] From the viewpoint of suppressing the reaction of the silica precursor, promoting emulsification promptly, and increasing the encapsulation rate of the oil agent, the number of carbon atoms of the higher fatty acid is preferably 8 or more, more preferably 10 or more, still more preferably 12 or more, even more preferably 14 or more, even more preferably 16 or more, and preferably 26 or less, more preferably 22 or less, still more preferably 20 or less. Examples of the higher fatty acid include 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, lanolinic acid, isostearic acid, etc. Among them, it is preferably a branched-chain saturated fatty acid, more preferably isostearic acid.

[0033] From the viewpoint of suppressing the reaction of the silica precursor, rapidly promoting emulsification, and increasing the encapsulation rate of the oil agent, the number of carbon atoms of the alkyl group of the monoalkyl glyceryl ether is preferably 10 or more, more preferably 12 or more, still more preferably 14 or more, even more preferably 16 or more, and preferably 24 or less, more preferably 22 or less, still more preferably 20 or less. Examples of the monoalkyl glyceryl ether include monoisohexyl glyceryl ether, monodecyl glyceryl ether, monolauryl glyceryl ether, monomyristyl glyceryl ether, monocetyl glyceryl ether, monostearyl glyceryl ether, and monobehenyl glyceryl ether. Among them, preferably one or more selected from monocetyl glyceryl ether, monostearyl glyceryl ether, and monobehenyl glyceryl ether, and more preferably monostearyl glyceryl ether. The monoalkyl glyceryl ether is usually in the α form.

[0034] From the viewpoint of suppressing the reaction of the silica precursor, rapidly promoting emulsification, and increasing the encapsulation rate of the oil agent, the number of carbon atoms of the alkyl group of the amide compound is preferably 10 or more, more preferably 12 or more, still more preferably 14 or more, and preferably 22 or less, more preferably 20 or less, still more preferably 18 or less. As the amide compound, an amide compound having an alkyl group derived from a saturated or unsaturated fatty acid is preferred. Specifically, examples include lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, and oleic acid amide.

[0035] From the viewpoint of suppressing the reaction of the silica precursor, rapidly promoting emulsification, and increasing the encapsulation rate of the oil agent, the cLogP value of the emulsification aid is preferably 4 or more, more preferably 5 or more, still more preferably 6 or more, and preferably 10 or less, more preferably 9 or less.

[0036] In addition, it is considered that the higher fatty acid and the higher aliphatic alcohol have a function as a particle size stabilizer that stabilizes the particle size of the emulsion droplets in addition to the function as an emulsification aid. From this perspective, as the oil phase components other than the oil agent and the silica precursor used in Step 1, preferably, it contains one or more selected from higher fatty acids having 6 or more carbon atoms and higher aliphatic alcohols having 6 or more carbon atoms, and more preferably contains a higher fatty acid having 6 or more carbon atoms.

[0037] When the oil phase component used in Step 1 further contains the emulsification aid, from the perspective of suppressing the reaction of the silica precursor, allowing the emulsification to proceed promptly, and increasing the encapsulation rate of the oil agent, the amount of the emulsification aid is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, still more preferably 0.5 part by mass or more, and preferably 10 parts by mass or less, more preferably 7 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the oil agent used in Step 1.

[0038] 〔Particle Size Stabilizer〕 Examples of the particle size stabilizer include fatty acid esters having a total carbon number of 6 or more. The particle size stabilizer contributes to suppressing the destabilization of the emulsion droplets due to Ostwald ripening in which relatively hydrophilic components as the oil phase components in the emulsion droplets diffuse into the aqueous phase which is the continuous phase, suppresses the coarsening of the emulsion droplets over time, and is considered to be able to stabilize the particle size of the emulsion droplets. Therefore, by using the particle size stabilizer in combination with the emulsification aid, it is considered that while suppressing the reaction of the silica precursor, the emulsification can proceed promptly, an appropriate shell formation field can be provided as a template for the silica capsule particles, and the encapsulation rate of the oil agent can be increased. From this perspective, the clogP value of the particle size stabilizer is preferably 4 or more, more preferably 5 or more, still more preferably 6 or more, even more preferably 7 or more, and preferably 10 or less, more preferably 9 or less.

[0039] From the perspective of suppressing the reaction of the silica precursor while allowing emulsification to proceed rapidly and increasing the encapsulation rate of the oil agent, the total number of carbon atoms of the fatty acid ester is preferably 10 or more, more preferably 14 or more, still more preferably 18 or more, and preferably 50 or less. Examples of the fatty acid ester include fatty acid monoesters of fatty acids and monohydric alcohols, fatty acid diesters of fatty acids and dihydric alcohols, dicarboxylic acid diesters of dicarboxylic acids and monohydric alcohols, tricarboxylic acid triesters of tricarboxylic acids and monohydric alcohols, glycerin fatty acid triesters, and the like. Among them, from the perspective of suppressing the reaction of the silica precursor while allowing emulsification to proceed rapidly and increasing the encapsulation rate of the oil agent, fatty acid monoesters are preferred. The fatty acid monoesters preferably consist of a fatty acid having 8 to 22 carbon atoms and a monohydric alcohol having 1 to 24 carbon atoms. Examples of the fatty acid constituting the fatty acid monoesters include saturated or unsaturated fatty acids having 8 to 22 carbon atoms such as 2-ethylhexanoic acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, palmitoleic acid, margaric acid, stearic acid, oleic acid, linoleic acid, erucic acid, arachidic acid, behenic acid, and the like. Examples of the monohydric alcohol constituting the fatty acid monoesters include aliphatic monohydric alcohols having 1 to 24 carbon atoms such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, n-pentyl alcohol, isopentyl alcohol, neopentyl alcohol, hexanol, heptanol, octanol, 2-ethylhexyl alcohol, nonanol, isononyl alcohol, decanol, isodecyl alcohol, dodecanol, lauryl alcohol, tridecanol, myristyl alcohol, pentadecanol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, behenyl alcohol, 2-octyldodecanol, and the like. Examples of the fatty acid monoester include cetyl 2-ethylhexanoate, butyl stearate, isopropyl myristate, hexadecyl myristate, 2-octyldodecyl myristate, isopropyl palmitate, hexadecyl palmitate, 2-ethylhexyl stearate, etc. Among them, isopropyl palmitate is preferable.

[0040] When the oil phase component used in Step 1 further contains the particle size stabilizer, from the viewpoint of suppressing the reaction of the silica precursor, accelerating emulsification, and increasing the encapsulation rate of the oil agent, the amount of the particle size stabilizer is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, still more preferably 0.5 part by mass or more, and preferably 10 parts by mass or less, more preferably 7 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the oil agent used in Step 1.

[0041] (Emulsification of the oil-water mixture) The mass ratio (aqueous phase component / oil phase component) of the aqueous phase component containing a dispersant and water used in Step 1 and the oil phase component containing an oil agent and a silica precursor is preferably 50 / 50 or more, more preferably 55 / 45 or more, still more preferably 60 / 40 or more, from the viewpoint of obtaining a stable emulsion, and preferably 99 / 1 or less, more preferably 95 / 5 or less, still more preferably 90 / 10 or less, even more preferably 80 / 20 or less, even more preferably 70 / 30 or less, from the viewpoint of production efficiency. From these viewpoints, it is preferably 50 / 50 or more and 99 / 1 or less, more preferably 55 / 45 or more and 95 / 5 or less, still more preferably 60 / 40 or more and 90 / 10 or less, even more preferably 60 / 40 or more and 80 / 20 or less, even more preferably 60 / 40 or more and 70 / 30 or less.

[0042] As an emulsification method in Process 1, a method is preferably adopted in which a previously prepared aqueous phase component and an oil phase component are mixed in a reaction tank to prepare an oil-water mixture, and then the oil-water mixture is supplied to an in-line emulsification disperser provided outside the reaction tank for emulsification. In the preparation of the oil-water mixture in this method, the charging order of the aqueous phase component and the oil phase component into the reaction tank is not particularly limited. However, from the viewpoint of ease of production, it is preferable to prepare the aqueous phase component in the reaction tank and then add the separately prepared oil phase component. Preferably, the reaction tank is provided with a stirring device having a stirring blade. Examples of the stirring blade include paddle blades, turbine blades, anchor blades, ribbon blades, propellers, and the like.

[0043] The liquid temperature during stirring in the preparation of the aqueous phase component using the stirring device is preferably 0°C or higher, and preferably 40°C or lower, more preferably 35°C or lower. The stirring time in the preparation of the aqueous phase component using the stirring device depends on the production scale, stirring speed, temperature conditions, etc., but is preferably 60 minutes or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less.

[0044] When preparing the oil-water mixture in the reaction tank, in Process 1, the oil-water mixture in the reaction tank is preferably supplied to the in-line emulsification disperser while being mixed with the aforementioned stirring blade.

[0045] Also, when preparing the oil-water mixture in the reaction tank, the oil-water mixture used in Process 1 may be pre-emulsified with the aforementioned stirring blade before being supplied to the in-line emulsification disperser. The preferable range of the stirring rotation speed at this time is the same as the preferable range of the stirring rotation speed during the above-mentioned circulation mixing. The liquid temperature of the oil-water mixture to be subjected to pre-emulsification is preferably 0°C or higher, and preferably 40°C or lower, more preferably 35°C or lower. The stirring time in pre-emulsification depends on the production scale, stirring speed, temperature conditions, etc., but is preferably 60 minutes or less, more preferably 30 minutes or less, and even more preferably 20 minutes or less.

[0046] For the emulsification in Step 1, from the viewpoint of suppressing the reaction of the silica precursor, allowing the emulsification to proceed rapidly, and increasing the encapsulation rate of the oil agent, it is preferable to use an in-line emulsification disperser. The emulsification in Step 1 may be a "one-pass type" in which the oil-water mixture is passed through the in-line emulsification disperser only once, or may be a "multi-pass type" in which at least a part or all of the emulsion obtained by passing the oil-water mixture through the in-line emulsification disperser is passed through the in-line emulsification disperser again for multiple operations. As a one-pass type method, an in-line type can be mentioned. As a multi-pass type method, an "external circulation type", a "catch ball type", a "liquid return type", or an "in-line type" can be mentioned.

[0047] The external circulation type is a method in which the oil-water mixture is discharged from a reaction tank equipped with an external circulation line provided with an in-line emulsification disperser to the external circulation line, emulsified by the in-line emulsification disperser, and then the emulsion is returned from the external circulation line to the reaction tank to circulate the emulsion between the in-line emulsification disperser and the reaction tank. The catch ball type is a method in which a line provided with an in-line emulsification disperser is provided between two reaction tanks, and the emulsion is reciprocated between the reaction tanks through the line. The liquid return type is a method in which the line is connected so that the liquid circulates between two reaction tanks and the in-line emulsification disperser, and after the entire amount of the liquid has passed through the in-line emulsification disperser, the operation of returning the liquid to the original reaction tank is repeated. As the in-line type, a method in which a dispersant, water, an oil agent, and a silica precursor are mixed in-line to prepare an oil-water mixture, and then the oil-water mixture is supplied to an in-line emulsification disperser and emulsified by the in-line emulsification disperser is preferably mentioned.

[0048] Among these methods, from the viewpoints of suppressing the reaction of the silica precursor, allowing the emulsification to proceed rapidly, increasing the encapsulation rate of the oil agent, and the ease of equipment design, the emulsification in Step 1 is preferably carried out in an external circulation type or an in-line type using an in-line emulsification disperser. In the case of an external circulation type, from the viewpoints of suppressing the reaction of the silica precursor, promptly advancing emulsification, increasing the encapsulation rate of the oil agent, and ease of equipment design, it is preferable to circulate the emulsion between the in-line emulsifying and dispersing machine and the reaction tank through an external circulation line. In the case of an in-line type, it is preferable to attach an in-line emulsifying and dispersing machine to the line from the in-line mixing section that mixes the dispersant, water, oil agent, and silica precursor in-line and perform emulsification with the in-line emulsifying and dispersing machine. In the case of an in-line type, the in-line mixed oil-water mixture may be passed through the in-line emulsifying and dispersing machine one or more times. That is, in the case of an in-line type, the number of passes may be one (one-pass type) or a plurality of times (multi-pass type). In the in-line type, when the oil-water mixture is passed through the in-line emulsifying and dispersing machine a plurality of times, the emulsion obtained by passing the oil-water mixture discharged from the in-line mixing section through the in-line emulsifying and dispersing machine is stored in the reaction tank, and the line between the reaction tank and the in-line emulsifying and dispersing machine is connected so that the liquid circulates, and it is preferable to perform an operation of passing at least a part or all of the emulsion through the in-line emulsifying and dispersing machine again. In any of the above methods, two or more in-line emulsifying and dispersing machines may be connected.

[0049] From the viewpoint of efficiently applying a shearing force to the oil-water mixture, suppressing the reaction of the silica precursor, promptly advancing emulsification, and increasing the encapsulation rate of the oil agent, the in-line emulsifying and dispersing machine preferably has a rotor and a stator. An emulsifying and dispersing machine having a rotor and a stator is any dispersing machine that utilizes the shearing field generated between the rotor (rotating part) and the stator (non-rotating part) in the emulsifying and dispersing chamber. That is, by variously changing the clearance between the rotor and the stator and the rotational speed of the rotor, the shearing rate can be adjusted, and by passing the oil-water mixture between the rotor and the stator that rotates in the emulsifying and dispersing chamber, a shearing force can be applied to the oil-water mixture to perform emulsification.

[0050] The liquid temperature of the oil-water mixture used for emulsification in Step 1 is preferably 50°C or lower, more preferably 40°C or lower, still more preferably 35°C or lower, and even more preferably 30°C or lower, from the viewpoint of suppressing the reaction of the silica precursor. Also, from the viewpoint of production efficiency, the liquid temperature of the oil-water mixture used for emulsification in Step 1 may preferably be 0°C or higher. The emulsification time in Step 1 can be appropriately adjusted according to the production scale and the like, but is preferably 12 hours or less, more preferably 10 hours or less, still more preferably 8 hours or less, even more preferably 6.5 hours or less, even more preferably 6 hours or less, even more preferably 5 hours or less, and even more preferably 4 hours or less. By shortening the emulsification time in Step 1, the oil-water contact time can be shortened, and the reaction of the silica precursor can be suppressed.

[0051] The median diameter D of the emulsion droplets of the emulsion obtained in Step 1 50 is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more, and even more preferably 0.7 μm or more, from the viewpoint of reducing the specific surface area of the obtained silica capsule particles with respect to the external environment and improving the retention of the oil agent. And, from the viewpoint of the dispersion stability of the obtained silica capsule particles, it is preferably 10 μm or less, more preferably 7 μm or less, still more preferably 5 μm or less, even more preferably 3 μm or less, even more preferably 2 μm or less, and even more preferably 1.5 μm or less. From these viewpoints, it is preferably 0.1 μm or more and 10 μm or less, more preferably 0.3 μm or more and 7 μm or less, still more preferably 0.5 μm or more and 5 μm or less, even more preferably 0.7 μm or more and 3 μm or less, even more preferably 0.7 μm or more and 2 μm or less, and even more preferably 0.7 μm or more and 1.5 μm or less. The median diameter D of the emulsion droplets 50 can be measured by the method described in the examples.

[0052] <Step 2> Step 2 is a step of forming oil agent-containing silica capsule particles having a first shell (also referred to as "oil agent-containing silica capsule particles (1)") using the emulsion obtained in Step 1. The oil agent-containing silica capsule particles (1) formed in Step 2 are preferably obtained by a sol-gel reaction, and it is preferable to obtain them as an aqueous dispersion in which the oil agent-containing silica capsule particles (1) are dispersed in water.

[0053] In Step 2, after adding and diluting water to the emulsion obtained in Step 1, it is preferable to form the oil agent-containing silica capsule particles (1). By including this dilution operation, the amount of the oil-water mixture to be subjected to the emulsification treatment in Step 1 can be reduced, shear force can be efficiently applied to the oil-water mixture, the emulsification time can be shortened, partial or total destruction of the emulsion droplets formed in Step 1 can be suppressed, and the encapsulation rate of the oil agent can be increased. The dilution in Step 2 is such that the total amount of the oil agent and the silica precursor used in Step 1 is preferably 35 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 27 parts by mass or less, based on 100 parts by mass of the total amount of the diluted emulsion, and from the viewpoint of production efficiency, it is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, still more preferably 20 parts by mass or more. The dilution ratio is preferably 1.3 times or more, more preferably 1.4 times or more, still more preferably 1.5 times or more, from the viewpoint of increasing the encapsulation rate of the oil agent, and from the viewpoint of production efficiency, it is preferably 3 times or less, more preferably 2 times or less, still more preferably 1.8 times or less. In the present invention, the "dilution ratio" is the mass ratio of the total amount of the diluted emulsion to the total amount of the emulsion obtained in Step 1 before dilution to be subjected to Step 2 [(total amount of the diluted emulsion) / (total amount of the emulsion obtained in Step 1 before dilution to be subjected to Step 2)].

[0054] In Step 2, from the perspective of maintaining the balance between the hydrolysis reaction and polycondensation reaction of the silica precursor, and suppressing the formation of highly hydrophilic sols, promoting the encapsulation of the oil agent, and increasing the encapsulation rate of the oil agent, the pH of the emulsion used for forming the silica capsule particles (1) containing the oil agent is preferably 3.0 or higher, more preferably 3.3 or higher, still more preferably 3.5 or higher. From the perspective of suppressing the concurrence of the formation of the silica shell and the aggregation of emulsion droplets and increasing the encapsulation rate of the oil agent, it is preferably 4.5 or lower, more preferably 4.3 or lower, still more preferably 4.0 or lower.

[0055] In Step 2, from the perspective of adjusting the emulsion to a desired pH, according to the pH of the emulsion obtained in Step 1, a pH adjuster may be added to the emulsion obtained in Step 1 to adjust the pH of the emulsion, and then silica capsule particles (1) containing the oil agent may be formed. The pH adjuster can be appropriately selected from acidic pH adjusters and alkaline pH adjusters according to the pH of the emulsion obtained in Step 1. Examples of the acidic pH adjuster include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, organic acids such as acetic acid and citric acid, and solutions obtained by adding cation exchange resins, etc. to water, ethanol, etc. Preferably, it is at least one selected from hydrochloric acid, sulfuric acid, nitric acid, and citric acid. Examples of the alkaline pH adjuster include sodium hydroxide, sodium bicarbonate, potassium hydroxide, ammonium hydroxide, diethanolamine, triethanolamine, tris(hydroxymethyl)aminomethane, etc. Preferably, it is at least one selected from sodium hydroxide and ammonium hydroxide. Also, depending on the type of the oil agent, the pH of the emulsion obtained in Step 1 may be below the desired value. In that case, it is preferable to adjust it using the above-mentioned alkaline pH adjuster.

[0056] The stirring speed in Step 2 is preferably 400 r / min or less, more preferably 350 r / min or less, still more preferably 300 r / min or less in terms of the tip peripheral speed, from the viewpoint of suppressing partial or total destruction of the emulsion droplets formed in Step 1 and increasing the encapsulation rate of the oil agent. From the viewpoint of obtaining silica capsule particles with a narrow particle size distribution, it is preferably 10 r / min or more, more preferably 15 r / min or more, still more preferably 20 r / min or more. The liquid temperature (reaction temperature) in Step 2 is preferably 0°C or higher and preferably 40°C or lower, more preferably 35°C or lower. The stirring time in Step 2 depends on the production scale, stirring speed, temperature conditions, etc., but is preferably 6 hours or more, more preferably 12 hours or more, still more preferably 18 hours or more, and preferably 48 hours or less, more preferably 36 hours or less, still more preferably 30 hours or less.

[0057] <Step 2'> In the present invention, from the viewpoint of increasing the encapsulation rate of the oil agent, the following Step 2' may be included after Step 2 and before Step 3. Step 2' is a step of adding a silica precursor to an aqueous dispersion containing the oil agent-containing silica capsule particles (1) formed in Step 2 to form oil agent-containing silica capsule particles (also referred to as "oil agent-containing silica capsule particles (2)"). By Step 2', a second shell that encloses the first shell of the oil agent-containing silica capsule particles (1) is formed, and the shell of the resulting oil agent-containing silica capsule particles (2) can be made denser and stronger. The oil agent-containing silica capsule particles (2) formed in Step 2' are preferably obtained by a sol-gel reaction, similar to the oil agent-containing silica capsule particles (1), and are preferably obtained as an aqueous dispersion in which the oil agent-containing silica capsule particles (2) are dispersed in water.

[0058] The silica precursor used in Step 2' preferably contains tetraalkoxysilane, more preferably tetraalkoxysilane having an alkoxy group with 1 to 4 carbon atoms, and still more preferably one or more selected from tetramethoxysilane, tetraethoxysilane, and tetraisopropoxysilane, and even more preferably one or more selected from tetramethoxysilane and tetraethoxysilane, and even more preferably tetraethoxysilane, from the viewpoint of promoting the sol-gel reaction and increasing the encapsulation rate of the oil agent, similar to the aforementioned silica precursor. When the silica precursor contains tetraalkoxysilane, the content of tetraalkoxysilane in the silica precursor is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90% by mass or more, and preferably 100% by mass or less.

[0059] From the viewpoint of increasing the encapsulation rate of the oil agent, the amount of the silica precursor used in Step 2' is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, based on 100 parts by mass of the oil agent used in Step 1.

[0060] The preferable ranges of the stirring speed, liquid temperature, and stirring time in the formation of the second shell in Step 2' are the same as the preferable ranges of the stirring speed, liquid temperature, and stirring time in the formation of the first shell in Step 2 described above.

[0061] <Step 3> Step 3 is a step of taking out the oil agent-containing silica capsule particles (1) formed in Step 2 from the reaction tank. After Step 2 and before Step 3, when Step 2' is included, it is a step of taking out the oil agent-containing silica capsule particles (2) formed in Step 2' from the reaction tank.

[0062] From the viewpoint of the ease of taking out the oil agent-containing silica capsule particles (1) or (2), a reaction tank equipped with a discharge valve at the bottom is preferable. By opening the discharge valve provided at the bottom of the reaction tank, the oil agent-containing silica capsule particles (1) or (2) can be taken out. When the oil agent-containing silica capsule particles (1) or (2) are obtained as an aqueous dispersion in which they are dispersed in water, the oil agent-containing silica capsule particles (1) or (2) can be separated from the aqueous medium and taken out. As the separation method, a filtration method, a centrifugation method, or the like can be adopted.

[0063] <Step 4> As described above, in the present invention, the series of treatment steps of Steps 1 to 3 are continuously repeated in the same reaction tank. In the present invention, after Step 3 and before Step 1, from the viewpoint of increasing the encapsulation rate of the oil agent, the following Step 4 is included, and it is preferable to control the content of silica solid particles in the emulsion obtained in Step 1 to 0.5% by mass or less. Step 4 is a step of cleaning the inside of the reaction tank that has undergone Step 3.

[0064] The step of cleaning the inside of the reaction tank that has undergone Step 3 in Step 4 is to remove the silica component deposited on the tank wall and stirring blades inside the reaction tank, and to control the content of silica solid particles in the emulsion obtained in Step 1 to 0.5% by mass or less. From the viewpoint of increasing the encapsulation rate of the oil agent, the content of silica solid particles in the emulsion obtained in Step 1 after Step 4 is preferably 0.5% by mass or less, more preferably 0.4% by mass or less, still more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, and even more preferably 0.15% by mass or less. From the viewpoint of productivity, it may be preferably controlled to 0.001% by mass or more. When the silica solid particles are mixed in the emulsion in an amount exceeding 0.5% by mass, the silica solid particles come into contact with the silica precursor and react, so that the amount of the silica precursor that would originally be a raw material for shell formation decreases, and it may be difficult to form a desired dense and strong shell.

[0065] By performing this step 4 after the series of processing steps of steps 1 to 3, even if the oil agent-containing silica capsule particles are continuously and repeatedly produced in the same reaction tank, the content of the silica solid particles in the emulsion obtained in step 1 can be reduced. Step 4 may be appropriately performed after step 3 and before step 1 so that the content of the silica solid particles in the emulsion obtained in step 1 can be controlled to 0.5% by mass or less, and it is not necessary to perform it every time. The present invention is a method for continuously producing oil agent-containing silica capsule particles in which steps 1 to 3 are continuously repeated in the same reaction tank. As an embodiment in which step 4 is performed after step 3 and before step 1, it may be an embodiment in which steps 1 to 4 are continuously repeated in the same reaction tank (Embodiment 1), or an embodiment including a step of continuously repeating steps 1 to 3 in the same reaction tank and a step of performing steps 1 to 4 in the same reaction tank (Embodiment 2). Here, "continuously repeating" means continuously performing a series of processes of steps 1 to 3 or a series of processes of steps 1 to 4 two or more times, and may include a temporary interruption during the repeating process. On the other hand, the "step of performing steps 1 to 4 in the same reaction tank" in Embodiment 2 does not include the meaning of continuously performing a series of processes of steps 1 to 4 two or more times.

[0066] In the present invention, the number of times of continuously repeating steps 1 to 3 in the same reaction tank is preferably 50 times or less, more preferably 40 times or less, still more preferably 30 times or less, even more preferably 20 times or less, even more preferably 15 times or less, and even more preferably 12 times or less from the viewpoint of increasing the encapsulation rate of the oil agent, and preferably 2 times or more, more preferably 3 times or more, and still more preferably 4 times or more from the viewpoint of productivity.

[0067] Examples of the liquid used for washing include water, warm water, the aqueous phase used as a raw material in step 1, an alkaline aqueous solution, and a mixture thereof. The means for washing the inside of the reaction tank is preferably installed at the upper part of the reaction tank, preferably in a form of spraying downward, and preferably the washing means operates up and down and sprays perpendicularly to the tank wall surface. In addition, as for the means for cleaning the reaction vessel, it is also preferable to introduce the liquid used in the previous cleaning in an amount that contacts the silica solid particles derived from the silica component deposited on the vessel wall and stirring blades in the reaction vessel, and remove the silica solid particles while stirring.

[0068] The median diameter D of the oil agent-containing silica capsule particles according to the present invention 50 is preferably 0.1 μm or more, more preferably 0.3 μm or more, still more preferably 0.5 μm or more, even more preferably 0.7 μm or more, even more preferably 1.0 μm or more from the viewpoint of reducing the specific surface area with respect to the external environment of the silica capsule particles and improving the retention of the oil agent, and is preferably 10 μm or less, more preferably 7 μm or less, still more preferably 5 μm or less, even more preferably 3 μm or less from the viewpoint of the dispersion stability of the silica capsule particles. The median diameter D of the oil agent-containing silica capsule particles 50 can be measured by the method described in the examples.

[0069] The oil agent-containing silica capsule particles according to the present invention can be used in various applications. The oil agent-containing silica capsule particles according to the present invention can be suitably used, for example, in cosmetics such as emulsions, lotions, toners, beauty essences, creams, gel preparations, hair treatment agents, quasi-drugs; fiber treatment agents such as detergents, softeners, anti-wrinkle sprays; hygiene products such as paper diapers; and various applications such as fragrances. The oil agent-containing silica capsule particles according to the present invention can be used by being blended in compositions such as detergent compositions, fiber treatment agent compositions, cosmetic compositions, fragrance compositions, deodorant compositions. The composition is preferably at least one selected from detergent compositions such as powder detergent compositions and liquid detergent compositions; fiber treatment agent compositions such as softener compositions, more preferably a fiber treatment agent composition, still more preferably a softener composition.

[0070] The present invention includes the following aspects. [1] A method for producing oil agent-containing silica capsule particles having a core containing an oil agent and a shell containing silica as a constituent component, A method for continuously producing oil agent-containing silica capsule particles by continuously repeating the following steps 1 to 3 in the same reaction tank, wherein the content of silica solid particles in the emulsion obtained in step 1 is 0.5% by mass or less. Step 1: A step of emulsifying an aqueous phase containing a dispersant and water and an oil phase containing an oil agent and a silica precursor to obtain an emulsion Step 2: A step of forming oil agent-containing silica capsule particles having a first shell using the emulsion obtained in step 1 Step 3: A step of taking out the oil agent-containing silica capsule particles formed in step 2 from the reaction tank [2] The continuous production method of oil agent-containing silica capsule particles according to [1], which includes the following step 4 after step 3 and before step 1, and controls the content of silica solid particles in the emulsion obtained in step 1 to 0.5% by mass or less. Step 4: A step of cleaning the inside of the reaction tank that has gone through step 3 [3] A method for producing oil agent-containing silica capsule particles having a core containing an oil agent and a shell containing silica as a constituent component, A method for continuously producing oil agent-containing silica capsule particles by continuously repeating the following steps 1 to 4 in the same reaction tank, and controlling the content of silica solid particles in the emulsion obtained in step 1 to 0.5% by mass or less, as described in [2]. Step 1: A step of emulsifying an aqueous phase containing a dispersant and water and an oil phase containing an oil agent and a silica precursor to obtain an emulsion Step 2: A step of forming oil agent-containing silica capsule particles having a first shell using the emulsion obtained in step 1 Step 3: A step of taking out the oil agent-containing silica capsule particles formed in step 2 from the reaction tank Step 4: A step of cleaning the inside of the reaction tank that has gone through step 3 [4] A method for producing oil agent-containing silica capsule particles having a core containing an oil agent and a shell containing silica as a constituent component, A method for producing oil agent-containing silica capsule particles, comprising a step of continuously repeating the following steps 1 to 3 and a step of performing the following steps 1 to 4 in the same reaction vessel, and controlling the content of silica solid particles in the emulsion obtained in step 1 to 0.5% by mass or less. The continuous production method of oil agent-containing silica capsule particles according to [2]. Step 1: A step of emulsifying an aqueous phase containing a dispersant and water and an oil phase containing an oil agent and a silica precursor to obtain an emulsion Step 2: A step of forming oil agent-containing silica capsule particles having a first shell using the emulsion obtained in step 1 Step 3: A step of taking out the oil agent-containing silica capsule particles formed in step 2 from the reaction vessel Step 4: A step of cleaning the inside of the reaction vessel that has passed through step 3 [5] The mass ratio (aqueous phase component / oil phase component) of the aqueous phase component to the oil phase component in the emulsion of step 1 is preferably 50 / 50 or more and 99 / 1 or less, more preferably 55 / 45 or more and 95 / 5 or less, and still more preferably 60 / 40 or more and 90 / 10 or less. The continuous production method of oil agent-containing silica capsule particles according to any one of [1] to [4]. [6] The median diameter D of the emulsion droplets of the emulsion obtained in step 1 50 is preferably 0.1 μm or more and 10 μm or less, more preferably 0.3 μm or more and 7 μm or less, and still more preferably 0.5 μm or more and 5 μm or less. The continuous production method of oil agent-containing silica capsule particles according to any one of [1] to [5]. [7] After step 2 and before step 3, the continuous production method of oil agent-containing silica capsule particles according to any one of [1] to [6], including the following step 2'. Step 2': A step of adding a silica precursor to the aqueous dispersion containing the oil agent-containing silica capsule particles formed in step 2 to form oil agent-containing silica capsule particles having a second shell that encapsulates the first shell [8] The content of the silica solid particles in the emulsion obtained in Step 1 is preferably 0.4% by mass or less, more preferably 0.3% by mass or less, still more preferably 0.2% by mass or less, and even more preferably 0.15% by mass or less, which is the continuous production method of the oil agent-containing silica capsule particles described in any one of [1] to [7]. [9] The content of the silica solid particles in the emulsion obtained in Step 1 is preferably controlled to be 0.4% by mass or less, more preferably 0.3% by mass or less, still more preferably 0.2% by mass or less, and even more preferably 0.15% by mass or less, which is the continuous production method of the oil agent-containing silica capsule particles described in any one of [1] to [7].

[10] The number of times of continuously repeating Steps 1 to 3 in the same reaction tank is preferably 50 times or less, more preferably 40 times or less, still more preferably 30 times or less, even more preferably 20 times or less, even more preferably 15 times or less, and even more preferably 12 times or less, and is preferably 2 times or more, more preferably 3 times or more, and still more preferably 4 times or more, which is the continuous production method of the oil agent-containing silica capsule particles described in any one of [1] to [7].

Examples

[0071] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the scope of the examples. In the examples, various measurements and evaluations were carried out by the following methods.

[0072] [Median diameter D 50 The median diameter D of the emulsion droplets 50 and the median diameter D of the oil agent-containing silica capsule particles 50 were measured using a laser diffraction / scattering particle size distribution measuring device "LA-960" (product name, manufactured by Horiba, Ltd.). The measurement was carried out using a flow cell, the medium was water, and the refractive index of the dispersed substance was set to 1.45 - 0i. An emulsion or an aqueous dispersion containing oil agent-containing silica capsule particles was added to the flow cell, and the measurement was carried out at a concentration showing a transmittance of around 90%, and the median diameter D 50 was determined on a volume basis.

[0073] ​Content of Silica Solid Particles in Emulsion 10 g of the emulsion was sampled and placed in a centrifuge tube, and centrifuged at 5,000 r / min for 10 minutes using a centrifuge "CR22G" (product name, manufactured by Hitachi Koki Co., Ltd.). After removing the supernatant in the centrifuge tube, 10 g of ion-exchanged water was added, mixed several times with a spatula, and then centrifuged again at 5,000 r / min for 10 minutes using the above centrifuge. The solid content (silica solid particles) after removing the supernatant was placed in a platinum crucible, a few drops of sulfuric acid were added, dried with a heater, and then subjected to ashing treatment in an electric furnace at 550 °C. Next, 1 g of an alkaline flux (sodium carbonate: boric acid = 1:0.4) was added and melted in an electric furnace at 950 °C. Then, 5 mL of ultrapure water and hydrochloric acid (6N) were added, heated and dissolved on a hot plate at 70 °C, and after cooling, it was made up to 50 mL with ultrapure water to obtain a sample measurement solution. The total silica amount in this sample measurement solution was quantified from the emission intensity at a wavelength of 251.611 nm by ICP emission spectrometry, and the content of silica solid particles in the emulsion was calculated by the following formula. Content of Silica Solid Particles in Emulsion (mass%) = {(Total Silica Amount Contained in 10 g of Emulsion) / (Emulsion Sampling Amount; 10 g)} × 100

[0074] <Model Flavor As the oil agent encapsulated in silica capsule particles, model flavor A (volume average cLogP: 3.7, specific gravity: 0.96) having the composition shown in Table 1 was used. The volume average cLogP value of the model flavor was calculated as the sum of multiplying the cLogP values of the flavor components contained in the model flavor by their volume ratios in the model flavor, respectively.

[0075]

Table 1

[0076] Reference Example 1 (Step 1) In a spherical bottom cylindrical stirring reaction tank (inner diameter 11.4 cm) with a bottom discharge valve and an internal volume of 1.5 L, equipped with a 45° inclined paddle blade (blade diameter 2.9 cm), 2.39 g of Cationamin 60W (trade name, manufactured by Kao Corporation; cetyltrimethylammonium chloride, active ingredient 30% by mass) and 298.09 g of ion-exchanged water were mixed at a temperature of 15°C and a stirring rotation speed of 280 r / min for 10 minutes to prepare an aqueous phase component. To this aqueous phase component, an oil phase component prepared by preliminarily mixing 159.62 g of model fragrance A as an oil agent and 39.90 g of tetraethoxysilane (hereinafter also referred to as "TEOS") as a silica precursor in a disposable cup was added to obtain an oil-water mixture. 500.00 g of the obtained oil-water mixture was mixed at a temperature of 15°C and a stirring rotation speed of 280 r / min using the paddle blade, and while mixing, it was circulated externally for 3 minutes using an in-line emulsifying disperser "IKA magicLAB" (product name, manufactured by IKA) with a rotor peripheral speed of 18 m / s and a clearance of 0.239 mm to obtain an emulsion. As a result of measuring the content of silica solid particles in the obtained emulsion by the above method, it was 0% by mass. (Step 2) 296.17 g of ion-exchanged water was added to and diluted with the emulsion obtained in Step 1, and a 1% by mass sulfuric acid aqueous solution was added as a pH adjuster to adjust the pH to 3.7. Then, while raising the liquid temperature to 30°C and maintaining it, stirring was carried out at a stirring rotation speed of 280 r / min for 24 hours using the paddle blade to obtain an aqueous dispersion containing oil agent-containing silica capsule particles (1) having a core containing an oil agent and a first shell composed of silica as constituent components. (Step 2') Next, while continuing to stir at a liquid temperature of 30°C, 23.94 g of TEOS was dropped using a syringe pump over 7 hours. After the dropping, stirring was continued for another 17 hours to obtain an aqueous dispersion containing oil agent-containing silica capsule particles (2) having a second shell enclosing the first shell. (Step 3) The discharge valve at the bottom of the stirring reaction tank was opened, and the oil agent-containing silica capsule particles (2) obtained in Step 2' were taken out from the stirring reaction tank.

[0077] Reference Example 2 (Step 1) After going through the series of processing steps of Steps 1 to 3 of Reference Example 1, next, in the reaction vessel used in Reference Example 1, that is, a spherical-bottom cylindrical stirring reaction vessel (inner diameter 11.4 cm) with an internal volume of 1.5 L equipped with 45° inclined paddle blades (blade diameter 2.9 cm), 2.39 g of cotamine 60W and 298.09 g of ion-exchanged water were mixed at a temperature of 15°C and a stirring rotation speed of 280 r / min for 10 minutes to prepare an aqueous phase component. To this aqueous phase component, an oil phase component prepared by preliminarily mixing 159.62 g of model fragrance A as an oil agent and 39.90 g of TEOS as a silica precursor in a disposable cup was added to obtain an oil-water mixture. 500.00 g of the obtained oil-water mixture was mixed at a temperature of 15°C using the paddle blades at a stirring rotation speed of 280 r / min, and while mixing, it was circulated externally for 4 minutes using an in-line emulsifying disperser "IKA magicLAB" (product name, manufactured by IKA) with a rotor peripheral speed of 18 m / s and a clearance of 0.239 mm set to obtain an emulsion. As a result of measuring the content of silica solid particles in the obtained emulsion by the above method, it was 0.0095 mass%.

[0078] Example 1 (Step 1) In a spherical-bottom cylindrical stirring reaction vessel (inner diameter 11.4 cm) with an internal volume of 1.5 L equipped with 45° inclined paddle blades (blade diameter 2.9 cm), 2.39 g of cotamine 60W, 298.09 g of ion-exchanged water, and 0.19 g of silica solid particles (silica solid particles obtained in Reference Example 2: solid content obtained from the emulsion of Reference Example 2 by the above method) (an amount that becomes 0.038 mass% in the resulting emulsion, equivalent to a 4-consecutive batch amount) were mixed at a temperature of 15°C and a stirring rotation speed of 280 r / min for 10 minutes to prepare an aqueous phase component. To this aqueous phase component, an oil phase component prepared by preliminarily mixing 159.62 g of model fragrance A as an oil agent and 39.90 g of TEOS as a silica precursor in a disposable cup was added to obtain an oil-water mixture. 500.19 g of the obtained oil-water mixture was mixed at a temperature of 15°C while stirring at a rotation speed of 280 r / min using the paddle blades, and emulsified by external circulation for 4 minutes using an in-line emulsifying disperser "IKA magicLAB" (product name, manufactured by IKA) with the outermost peripheral speed of the rotor set to 18 m / s and the clearance set to 0.239 mm to obtain an emulsion. (Step 2) 296.17 g of ion-exchanged water was added to and diluted with the emulsion obtained in Step 1, and a 1% by mass sulfuric acid aqueous solution was added as a pH adjuster to adjust the pH to 3.7. Then, while raising the liquid temperature to 30°C and maintaining it, stirring was carried out at a rotation speed of 280 r / min for 24 hours using the paddle blades to obtain an aqueous dispersion containing oil agent-containing silica capsule particles (1) having a core containing an oil agent and a first shell composed of silica as constituent components. (Step 2') Next, while continuing stirring at a liquid temperature of 30°C, 23.94 g of TEOS was dropped using a syringe pump over 7 hours. After the dropping, stirring was continued for another 17 hours to obtain an aqueous dispersion containing oil agent-containing silica capsule particles (2) having a second shell enclosing the first shell. (Step 3) The discharge valve at the bottom of the stirring reaction tank was opened, and the oil agent-containing silica capsule particles (2) obtained in Step 2' were taken out from the stirring reaction tank.

[0079] Example 2 In Step 1 of Example 1, except that the silica solid particles (silica solid particles obtained in Reference Example 2) added to the aqueous phase were changed to 0.57 g (0.114% by mass in the produced emulsion, equivalent to 12 consecutive batches), a series of treatment steps from Step 1 to Step 3 were carried out in the same manner as in Example 1, and the oil agent-containing silica capsule particles (2) were taken out from the stirring reaction tank.

[0080] Comparative Example 1 In Step 1 of Example 1, except that the silica solid particles (silica solid particles obtained in Reference Example 2) added to the aqueous phase were changed to 3.56 g (0.713% by mass in the resulting emulsion, equivalent to 75 continuous batches), a series of treatment steps from Step 1 to Step 3 were performed in the same manner as in Example 1, and the oil agent-containing silica capsule particles (2) were taken out from the stirring reaction tank.

[0081] Note that, in each example, the median diameter D of the emulsion droplets of the emulsion obtained in Step 1 50 , and the median diameter D of the oil agent-containing silica capsule particles (2) taken out in Step 3 50 were measured by the method described above, and the results are shown in Table 2. Also, in each example, the encapsulation rate of the oil agent encapsulated in the oil agent-containing silica capsule particles (2) taken out in Step 3 was calculated and evaluated by the following method, and the results are shown in Table 2.

[0082] [Encapsulation rate of oil agent] 100 mg of the aqueous dispersion containing the oil agent-containing silica capsule particles (2) taken out in Step 3 was diluted with 10 g of methanol containing dodecane at a concentration of 10 μg / mL as an internal standard, and then ultrasonic irradiation was performed using an ultrasonic irradiation device (model "5510", manufactured by Branson) under the conditions of an output of 180 W and an oscillation frequency of 42 kHz for 60 minutes to obtain a diluted solution in which the oil agent in the silica capsule particles was eluted. Subsequently, the methyldihydrojasmonate contained in this diluted solution was measured using gas chromatography, and the amount y of methyldihydrojasmonate in 100 mg of the aqueous dispersion containing the oil agent-containing silica capsule particles was measured as the blending amount of the oil agent. Separately, 100 mg of the aqueous dispersion containing the oil agent-containing silica capsule particles (2) taken out in Step 3 was diluted with 10 g of ion-exchanged water, and then passed through a membrane filter "Omnipore" (product name, model "JAWP04700", manufactured by Millipore) to recover the oil agent-containing silica capsule particles on the membrane filter. Furthermore, on a membrane filter, after washing the oil agent-containing silica capsule particles with 10 mL of ion-exchanged water and then 10 mL of hexane, the silica capsule particles were immersed in 2 mL of acetonitrile containing dodecane at a concentration of 10 μg / mL as an internal standard, and ultrasonic irradiation was performed for 60 minutes under the conditions of an output of 180 W and an oscillation frequency of 42 kHz using an ultrasonic irradiation device (model "5510", manufactured by Branson) to elute the oil agent in the silica capsule particles. This solution was passed through a membrane filter "Omnipore" (product name, model "JAWP04700", manufactured by Millipore) again, and methyl dihydrojasmonate contained in this solution was measured using gas chromatography, and the amount x of methyl dihydrojasmonate encapsulated in the silica capsule particles was determined. The encapsulation rate of the oil agent was calculated by the following formula. Encapsulation rate of oil agent (%) = {(amount x of methyl dihydrojasmonate encapsulated in the oil agent-containing silica capsule particles in 100 mg of the aqueous dispersion containing the oil agent-containing silica capsule particles) / (amount y of methyl dihydrojasmonate in 100 mg of the aqueous dispersion containing the oil agent-containing silica capsule particles)} × 100

[0083] [Table 2]

[0084] From the results shown in Table 2, the following was confirmed. In Examples 1 to 2 in which the content of silica solid particles in the emulsion obtained in Step 1 was 0.5% by mass or less, oil agent-containing silica capsule particles having a higher encapsulation rate of the oil agent were obtained than in Comparative Example 1 in which the content of silica solid particles in the emulsion obtained in Step 1 exceeded 0.5% by mass.

Industrial Applicability

[0085] According to the present invention, it is possible to provide a method for continuously producing oil agent-containing silica capsule particles having a high encapsulation rate of the oil agent even when the oil agent-containing silica capsule particles are continuously and repeatedly produced in the same reaction tank.

Claims

1. A method for producing oil agent-containing silica capsule particles having a core containing an oil agent and a shell containing silica as a constituent component, comprising: A method for continuously producing oil agent-containing silica capsule particles by continuously repeating the following steps 1 to 3 in the same reaction tank, wherein the content of silica solid particles in the emulsion obtained in step 1 is 0.5% by mass or less. Step 1: A step of emulsifying an aqueous phase containing a dispersant and water and an oil phase containing an oil agent and a silica precursor to obtain an emulsion Step 2: A step of forming oil agent-containing silica capsule particles having a first shell using the emulsion obtained in step 1 Step 3: A step of taking out the oil agent-containing silica capsule particles formed in step 2 from the reaction tank

2. The method for continuously producing oil agent-containing silica capsule particles according to claim 1, further comprising the following step 4 after step 3 and before step 1, and controlling the content of silica solid particles in the emulsion obtained in step 1 to 0.5% by mass or less. Step 4: A step of cleaning the inside of the reaction tank that has undergone step 3

3. The method for continuously producing oil agent-containing silica capsule particles according to claim 1 or 2, wherein the mass ratio (aqueous phase component / oil phase component) of the aqueous phase component to the oil phase component in the emulsion of step 1 is 50 / 50 or more and 99 / 1 or less.

4. The median diameter D of the emulsion droplets of the emulsion obtained in Step 1 50 The continuous production method of oil agent-containing silica capsule particles according to any one of claims 1 to 3, wherein the median diameter D is 10 μm or less.

5. The method for continuously producing oil agent-containing silica capsule particles according to any one of claims 1 to 4, further comprising the following step 2' after step 2 and before step 3. Step 2': A step of adding a silica precursor to the aqueous dispersion containing the oil agent-containing silica capsule particles formed in step 2 to form oil agent-containing silica capsule particles having a second shell that encloses the first shell

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