Microcapsule manufacturing method

Abstract

The present invention uses a production method according to a more efficient and reliable interfacial polymerization method to easily provide a microcapsule, even when microcapsule production according to an interfacial polymerization method is difficult in terms of the addition of a film-forming substance solution. Specifically, the present invention provides a microcapsule production method which is a method for producing a microcapsule using two varieties of different sized particles and is characterized by comprising: an emulsion-forming step in which two types of emulsion (1) and (2) with the same continuous phase are formed separately, and one of two types of monomers that form a film in reaction to one another is included in emulsion particles (1) of the emulsion (1), and the other monomer is included in emulsion particles (2) of the emulsion (2); and a microcapsule-forming step in which the emulsion (1) and emulsion (2) are mixed and interfacially polymerized, the average particle size (R) of the emulsion particles (1) of the emulsion (1) being 0.1-300 μm, the average particle size (r) of the emulsion particles (2) of the emulsion (2) being 0.01-30 μm, and r / R being ≦0.1.

Description

[Technical Field]

[0001] The present invention relates to a method for producing microcapsules using emulsion particles of two different sizes. [Background technology]

[0002] Microcapsules with a core agent covered with a shell are used in a variety of fields. For example, hydrous microcapsules with water as the core material are used in heat exchangers and the like as a cold storage medium, utilizing the latent heat of water. Thermally expandable microcapsules with a hydrocarbon or other core material are used in a wide range of applications as design-imparting agents and weight-reducing agents. Thermally expandable microcapsules are also incorporated into materials such as wallpaper for use in lightweight paints and the like. Meanwhile, in epoxy resin compositions used in adhesives, sealants, coatings, and the like, microcapsules are used in which the curing agent or curing accelerator serving as the core agent is covered with a shell to impart latency, in order to form a stable one-component mixture of the epoxy resin and the curing agent or curing accelerator for promoting the curing of the epoxy resin.

[0003] However, compared with microcapsules in which the core agent is hydrophobic, microcapsules in which the core agent is a water-soluble substance such as water or a method for producing the same have been relatively slow to develop, and even when the core agent is hydrophobic, there is a problem that microcapsules that can react with the aqueous phase and stably retain the contents cannot be obtained.

[0004] A known method for producing microcapsules with a water-soluble core agent is to use hexane, an organic solvent, as the core agent to form an O / W emulsion, then add an aqueous solution containing hexamethylenediamine to form a film, and heat to volatilize the hexane and form a film on the particle surface, thereby obtaining microcapsules with a high moisture content, as described in JP 2-258052 A (Patent Document 1). This is because storage stability cannot be maintained if a water-soluble substance is used as the core agent from the beginning, and the production process requires unsafe and complicated operations, such as the need for a step to volatilize the organic solvent.

[0005] In contrast, Japanese Patent Laid-Open No. 2012-140600 (Patent Document 2) discloses that a water-soluble substance containing a water-soluble radical polymerization initiator is used as a core agent, and after forming a core by radical polymerization, a coating is further formed on the surface of the core by interfacial polymerization to obtain microcapsules. However, this manufacturing process requires two reactions to obtain the desired microcapsules, and therefore, it is not necessarily a simple manufacturing process.

[0006] Furthermore, Japanese Patent Publication No. 6-018636 (Patent Document 3) describes a method for preparing microcapsules by mixing a first O / W organic emulsion in water, in which a solution containing a polyisocyanate (a first oil-soluble reactant) serves as the oil phase and a solution containing a surfactant serves as the aqueous phase, with a second O / W organic emulsion in water, in which a solution containing an amine (a second oil-soluble reactant) serves as the oil phase and a solution containing a surfactant serves as the aqueous phase. However, this method raises concerns that the reaction between water and isocyanate during the preparation of the emulsion of polyisocyanate and the aqueous phase may result in side reactions other than film formation. Furthermore, it is unclear how the reaction components are able to be exchanged by droplet collision. Furthermore, the reaction time required is 4 to 24 hours, and a manufacturing method that can easily obtain high-quality microcapsules is needed.

[0007] It is desirable to efficiently obtain strong, leak-resistant, dense microcapsules capable of encapsulating various beneficial substances, and it is also desirable to obtain strong, storage-stable microcapsules capable of encapsulating epoxy resin curing agents. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2-258052 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-140600 [Patent Document 3] Special Publication No. 6-018636 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to easily provide microcapsules using a more efficient and reliable interfacial polymerization method, even when it is difficult to produce microcapsules by interfacial polymerization using a solution of a film-forming substance. [Means for solving the problem]

[0010] The present invention provides the following aspects: [1] A method for producing microcapsules using two types of emulsion particles of different sizes, an emulsion-forming step of separately forming two types of emulsions (1) and (2) having a common continuous phase, and incorporating one of two types of monomers that react with each other to form a film into emulsion particles (1) of emulsion (1) and the other monomer into emulsion particles (2) of emulsion (2); a microcapsule formation step of mixing emulsion (1) and emulsion (2) and subjecting them to interfacial polymerization; It consists of A method for producing microcapsules, characterized in that the emulsion particles (1) of the emulsion (1) have an average particle size (R) of 0.1 to 300 μm, the emulsion particles (2) have an average particle size (r) of 0.01 to 30 μm, and r / R≦0.1. [2] The method for producing microcapsules according to [1], wherein the emulsion particles (1) have an average particle size (R) of 0.1 to 100 μm, the emulsion particles (2) have an average particle size (r) of 0.01 to 10 μm, and r / R≦0.1. [3] The method for producing microcapsules according to [1] or [2], wherein after the emulsion formation step, the average particle size (R) of the emulsion particles (1) or the average particle size (r) of the emulsion particles (2) is adjusted to fall within a predetermined range. [4] The method for producing microcapsules according to any one of [1] to [3], wherein the rate of increase in the average particle size (R) during the microcapsule formation step is less than 1.3 times. [5] The method for producing microcapsules according to any one of [1] to [4], wherein the continuous phase is liquid paraffin or silicone oil. [6] A method for producing microcapsules according to any one of [1] to [5], wherein one of two types of monomers that react with each other to form a coating is an isocyanate compound having two or more functional isocyanate groups in one molecule, and the other monomer is a monomer selected from the group consisting of a polyamine compound having two or more functional amino groups in one molecule, a polyhydroxy compound having two or more functional hydroxyl groups in one molecule, and combinations thereof. [7] The method for producing microcapsules according to any one of [1] to [6], wherein the core agent of the microcapsules is water, a water-soluble heat storage material, a thermally expandable hydrocarbon or its fluoride, an epoxy resin curing agent, or an epoxy resin curing accelerator. [8] The method for producing microcapsules according to any one of [1] to [7], wherein the curing agent for epoxy resin contains polyisocyanate, bisphenol A type epoxy resin, and an imidazole compound. [9] The method for producing microcapsules according to any one of [1] to [8], wherein the curing agent for epoxy resin is a liquid mixture obtained by mixing polyisocyanate, bisphenol A type epoxy resin, and imidazole compound in advance, and then heating and stirring the mixture.

[10] The method for producing microcapsules according to any one of [1] to [9], wherein the reaction time in the microcapsule formation step is 6 hours or less. [Effects of the Invention]

[0011] According to the present invention, even if it is difficult to produce stable microcapsules by interfacial polymerization methods that involve the addition of solutions of substances containing film-forming materials or polymerization reactants, microcapsules of any particle size can be easily obtained with high efficiency by interfacial polymerization methods using the emulsions of the present invention. Furthermore, microcapsules in which an aqueous substance is encapsulated in the core substance can maintain a high water content, while capsules in which a hydrophobic substance is encapsulated in the core substance can provide capsules with excellent pressure resistance. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Terminology> In this specification, the phrase "having a common continuous phase" means that "the continuous phases that form the emulsion are the same or can dissolve each other," and includes cases where the exact same continuous phase is used, as well as cases where the continuous phases are different in composition but can dissolve each other.

[0013] The present invention provides a method for producing microcapsules using two types of emulsion particles with different sizes, which comprises the steps of: an emulsion-forming step of separately forming two types of emulsions (1) and (2) having a common continuous phase, and incorporating one of two types of monomers that react with each other to form a film into emulsion particles (1) of emulsion (1) and the other monomer into emulsion particles (2) of emulsion (2); a microcapsule formation step of mixing emulsion (1) and emulsion (2) and subjecting them to interfacial polymerization; It consists of The present invention provides a method for producing microcapsules, characterized in that the average particle size (R) of emulsion particles (1) in emulsion (1) is 0.1 to 300 μm, the average particle size (r) of emulsion particles (2) in emulsion (2) is 0.01 to 30 μm, and r / R≦0.1. In this invention, microcapsules are produced using two types of emulsion particles of different sizes. The two types of emulsions are formed separately, and the average particle size (R) of emulsion particles (dispersed phase) (1) in emulsion (1) must be 0.1 to 300 μm, the average particle size (r) of emulsion particles (dispersed phase) (2) in emulsion (2) must be 0.01 to 20 μm, and r / R≦0.1 is required. That is, the average particle size (R) of emulsion particles (1) in emulsion (1) must be larger, and the average particle size (r) of emulsion particles (2) in emulsion (2) must be 1 / 10 times smaller. In the microcapsule formation process, the two emulsions are mixed and subjected to interfacial polymerization, i.e., a polymerization reaction, to form the capsules. It is thought that the small emulsion particles (2) adhere to the large emulsion particles (1), and a polymerization reaction occurs at the interface to form a membrane, forming the microcapsules.

[0014] Since emulsion (1) contains a core agent for the microcapsules, the core agent is water when water is to be encapsulated, or a water-soluble heat storage material that stores or releases heat by phase change when microcapsules are to be produced for heat storage applications. Specifically, the water-soluble heat storage material is one or more selected from the group consisting of sugars, sugar alcohols, inorganic salts, and inorganic salt hydrates.

[0015] When the core agent is aqueous, additives for effectively emulsifying the core agent include gelling agents that dissolve in an aqueous solvent and gel, and dispersion stabilizers that stabilize the core agent. Examples of gelling agents include polyvinyl alcohol, polyvinylphenol, polyvinylpyrrolidone, polyacrylamide, polyacrylic acid, polymethacrylic acid, polyethylene glycol, methylcellulose, hydroxypropyl cellulose, agar, gelatin, and sodium alginate. These may be used alone or in combination of two or more. Examples of dispersion stabilizers include silica, calcium phosphate, magnesium hydroxide, aluminum hydroxide, ferric hydroxide, barium sulfate, calcium sulfate, sodium sulfate, calcium oxalate, calcium carbonate, barium carbonate, and magnesium carbonate.

[0016] Furthermore, when producing microcapsules for use as thermal expansion agents, core agents include linear aliphatic hydrocarbons having 3 to 8 carbon atoms, branched aliphatic hydrocarbons having 3 to 8 carbon atoms, cyclic aliphatic hydrocarbons having 3 to 8 carbon atoms, ether compounds having a hydrocarbon group having 2 to 8 carbon atoms, and fluorides in which some of the hydrogen atoms in the hydrocarbon group have been substituted with fluorine atoms. More specific examples include propane, cyclopropane, butane, cyclobutane, isobutane, pentane, cyclopentane, neopentane, isopentane, hexane, cyclohexane, 2-methylpentane, 2,2-dimethylbutane, heptane, cycloheptane, octane, cyclooctane, methylheptanes, trimethylpentanes, and hydrofluoroethers such as C3F7OCH3, C4F9OCH3, and C4F9OC2H5. These may be used alone or in combination. Additionally, peroxides such as dialkyl peroxides, diacyl peroxides, peroxy acid esters, peroxydicarbonates and azo compounds may also be selected as the expanding agent.

[0017] As the core agent of the microcapsules of the present invention, a curing agent or curing accelerator for promoting the curing of the epoxy resin can also be used. Specific examples of the curing agent or curing accelerator for the epoxy resin include imidazole compounds and amine compounds. Examples of imidazole compounds include 2-methylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-undecylimidazole, 2-heptadecylimidazole, and 1-cyanoethylimidazole. Examples of amine compounds include ethylenediamine, butanediamine, hexamethylenediamine, octanediamine, diethylenetriamine, triethylenediamine, triethylenetriamine, malonic acid dihydrazide, 1,3-bis(hydrazinocarbonoethyl)-5-isopropylhydantoin, 1,8-diazabicyclo[5.4.0]undec-7-ene, 2,4,6-tris(dimethylamino)phenol, 2-dimethylaminophenol, etc. These imidazole compounds and amine compounds may be used alone or in combination of two or more.

[0018] The imidazole compound or amine compound can also be used as an imidazole adduct of an epoxy resin or an amine adduct of an epoxy resin. Examples of adducts include compounds obtained by reacting an epoxy resin with an imidazole compound or an amine compound. An imidazole adduct of an epoxy resin consisting of an imidazole compound and an epoxy resin is preferred. The solvent used as needed in the production of the imidazole adduct is not particularly limited, but examples include hydrocarbons such as benzene, toluene, xylene, cyclohexane, mineral spirits, and naphtha; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and esters such as ethyl acetate, n-butyl acetate, and propylene glycol monomethyl ether acetate. These solvents may be used in combination. The ratio of the epoxy resin to the imidazole compound is preferably in the range of 1:0.2 to 1:5, based on the active hydrogen equivalent (amine value) of the imidazole compound. If the equivalent ratio is less than 1:0.2, i.e., if the amount of epoxy resin added is small, the fluidity of the imidazole compound increases, making it unsuitable for long-term storage stability. On the other hand, if the equivalent ratio is greater than 1:5, i.e., if the amount of epoxy resin added is large, the viscosity increases, making it difficult to form small droplets in the following emulsification process, making it difficult to obtain small-sized microcapsules. Therefore, the amount of epoxy resin added to the imidazole compound is preferably 1:0.3 to 1:1 relative to the active hydrogen equivalent (amine value) of the imidazole compound.

[0019] The shell (membrane) of the microcapsules produced in the present invention is formed from two types of monomers that react with each other to form a membrane. In the present invention, preferred examples include polyisocyanate and a polyhydroxy compound (forming a polyurethane membrane) or a polyamine compound (forming a polyamide membrane) that reacts with it to form a membrane.

[0020] Polyisocyanates include aliphatic polyisocyanates and aromatic polyisocyanates. Examples of aliphatic polyisocyanates include trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,4-bis(isocyanatemethyl)cyclohexane, 1,3-bis(isocyanatemethyl)cyclohexane, isophorone diisocyanate, lysine diisocyanate, and hydrogenated xylylene diisocyanate. Examples of aromatic polyisocyanates include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, 3,3'-dimethoxy-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, 4-chloroxylylene-1,3-diisocyanate, 2-methylxylylene-1,3-diisocyanate, 4,4'-diphenylpropane diisocyanate, and 2,2-bis(4-isocyanatophenyl)hexafluoropropane. Although bifunctional diisocyanate compounds have been exemplified above, trifunctional triisocyanate compounds and tetrafunctional tetraisocyanate compounds may also be used, which can be inferred from these compounds.

[0021] Examples of condensates, polymers, or adducts using an isocyanate compound include biurets or isocyanurates, which are trimers of the above-mentioned bifunctional isocyanate compounds; polyfunctional compounds obtained by adducts of polyols such as trimethylolpropane and bifunctional isocyanate compounds; formalin condensates of benzene isocyanate; polymers of isocyanate compounds having a polymerizable group, such as methacryloyloxyethyl isocyanate; and lysine triisocyanate.

[0022] Polyisocyanate compounds are described in "Polyurethane Resin Handbook" (edited by Iwata Keiji, published by Nikkan Kogyo Shimbun, Ltd. (1987)).

[0023] Among the above, a preferred embodiment is one in which the shell of the microcapsule contains a polymer of a trifunctional or higher isocyanate. Examples of trifunctional or higher isocyanates include trifunctional or higher aromatic isocyanate compounds and trifunctional or higher aliphatic isocyanate compounds. Examples of trifunctional or higher isocyanate compounds include adducts (addition products) of a bifunctional isocyanate compound (a compound having two isocyanate groups in the molecule) with a compound having three or more active hydrogen groups in the molecule (such as a trifunctional or higher compound such as a polyol, polyamine, or polythiol), which are trifunctional or higher isocyanate compounds (adduct type), and trimers (biuret type or isocyanurate type) of bifunctional isocyanate compounds. Specific examples of trifunctional or higher isocyanate compounds include adducts of 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, or hexamethylene diisocyanate with trimethylolpropane, biuret types, isocyanurates, etc.

[0024] The adduct-type tri- or higher functional isocyanate compound may be a commercially available product on the market. Examples of commercially available products include Takenate (registered trademark) D-102, D-103, D-103H, D-103M2, P49-75S, D-110N, D-120N, D-140N, and D-160N (all manufactured by Mitsui Chemicals, Inc.), Desmodur (registered trademark) L75 and UL57SP (manufactured by Sumika Bayer Urethane Co., Ltd.), Coronate (registered trademark) HL, HX, and L (manufactured by Nippon Polyurethane Co., Ltd.), P301-75E (manufactured by Asahi Kasei Corporation), and Burnock (registered trademark) D-750 (manufactured by DIC Corporation). The isocyanurate-type trifunctional or higher isocyanate compound may be a commercially available product on the market, for example, Takenate (registered trademark) D-127N, D-131N, D-132N, D-170N, D-170HN, D-172N, D-177N, D-204, D-262, Stabio (registered trademark) D-370N (manufactured by Mitsui Chemicals, Inc.), Sumidur N3300, Desmodur (registered trademark) N3600, N3900, Z4470BA (Sumika Bayer Urethane), Coronate (registered trademark) HX, HK (manufactured by Nippon Polyurethane Co., Ltd.), Duranate (registered trademark) TPA-100, TKA-100, TSA-100, TSS-100, TLA-100, TSE-100 (manufactured by Asahi Kasei Corporation), and the like. The biuret-type tri- or higher functional isocyanate compound may be a commercially available product, such as Takenate (registered trademark) D-165N, NP1100 (manufactured by Mitsui Chemicals, Inc.), Desmodur (registered trademark) N3200 (manufactured by Sumika Bayer Urethane), or Duranate (registered trademark) 24A-100 (manufactured by Asahi Kasei Corporation).

[0025] The polyisocyanates in the present invention may be used alone or in combination of two or more.

[0026] The polyhydroxy compound preferably has no isocyanate group or amino group, and more preferably has no isocyanate group or amino group. The number of hydroxyl groups that the hydroxy compound has in one molecule is not particularly limited as long as it is 2 or more, but is preferably 2 to 6, more preferably 2 to 5, even more preferably 2 to 4, and particularly preferably 2 or 3.

[0027] Examples of the polyhydroxy compound include organic polyhydroxy compounds, and examples of the organic polyhydroxy compound include alkylene glycols such as ethylene glycol, propylene glycol, and 1,4-butanediol. The hydroxy compound used in forming the polyurethane by polycondensation may be one type or two or more types, and when two or more types are used, the combination and ratio thereof can be selected arbitrarily.

[0028] A catalyst can be added to accelerate the reaction during polyurethane formation. For example, catalysts such as 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), and 1,4-diazabicyclo[2.2.2]octane (DABCO) can be used alone or in combination.

[0029] Examples of polyamine compounds include substances containing two or more amino groups, such as ethylenediamine, propylenediamine, 1,4-diaminobutane, 1,5-diaminopentane, hexamethylenediamine, 1,8-diaminooctane, bis(2-aminoethyl)amine, tris(2-aminoethyl)amine, tris(3-aminopropyl)amine, bis(hexamethylene)triamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N,N'-bis(2-aminoethyl)-1,3-propanediamine, N,N'-bis(3-aminopropyl)ethylenediamine, 1,2-bis(2-aminoethoxy)ethane, 1,4-butanediol bis(3-aminopropyl)ether, and diethylene glycol bis(3-aminopropyl)ether. Among these, at least one selected from tris(2-aminoethyl)amine, bis(2-aminoethyl)amine, bis(hexamethylene)triamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, and hexamethylenediamine is more preferred. The polyamine compounds may be used alone or in combination of two or more.

[0030] When the continuous phase of the emulsion of the present invention is an aqueous phase, the emulsion may contain an aqueous medium and an emulsifier. The aqueous medium is preferably water. The aqueous medium accounts for preferably 20% to 80% by mass, more preferably 30% to 70% by mass, and even more preferably 40% to 60% by mass of the total mass of the emulsion, which is a mixture of an oil phase and an aqueous phase.

[0031] The emulsifier includes a dispersant, a surfactant, or a combination thereof. Examples of the dispersant include polyvinyl alcohol and its modified products (e.g., anion-modified polyvinyl alcohol), polyacrylic acid amide and its derivatives, ethylene-vinyl acetate copolymer, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyvinylpyrrolidone, ethylene-acrylic acid copolymer, vinyl acetate-acrylic acid copolymer, carboxymethyl cellulose, methyl cellulose, casein, gelatin, starch derivatives, gum arabic, and sodium alginate.

[0032] Examples of surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, etc. The surfactants may be used alone or in combination of two or more.

[0033] The nonionic surfactant is not particularly limited, and conventionally known surfactants can be used.For example, polyoxyethylene alkyl ether compounds, polyoxyethylene alkylphenyl ether compounds, polyoxyethylene polystyrylphenyl ether compounds, polyoxyethylene polyoxypropylene alkyl ether compounds, glycerin fatty acid partial ester compounds, sorbitan fatty acid partial ester compounds, pentaerythritol fatty acid partial ester compounds, propylene glycol mono-fatty acid ester compounds, sucrose fatty acid partial ester compounds, polyoxyethylene sorbitan fatty acid partial ester compounds, polyoxyethylene sorbitol fatty acid partial ester compounds, polyethylene glycol fatty acid ester compounds, polyglycerin fatty acid partial ester compounds, polyoxyethylene castor oil compounds, polyoxyethylene glycerin fatty acid partial ester compounds, fatty acid diethanolamide compounds, N,N-bis(2-hydroxyethyl) alkylamine compounds, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides, polyethylene glycol, copolymers of polyethylene glycol and polypropylene glycol.

[0034] The anionic surfactant is not particularly limited, and conventionally known surfactants can be used. For example, fatty acid salts, abietic acid salts, hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinate salts, linear alkylbenzenesulfonates, branched alkylbenzenesulfonates, alkylnaphthalenesulfonates, alkylphenoxypolyoxyethylenepropylsulfonates, polyoxyethylene alkylsulfophenyl ether salts, N-methyl-N-oleyl taurine sodium salt, N-alkylsulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated beef tallow oil, sulfate ester salts of fatty acid alkyl esters, alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate esters. Examples of the alkyl ester include ester salts, fatty acid monoglyceride sulfate salts, polyoxyethylene alkylphenyl ether sulfate salts, polyoxyethylene styrylphenyl ether sulfate salts, alkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, polyoxyethylene alkylphenyl ether phosphate salts, partially saponified products of styrene-maleic anhydride copolymers, partially saponified products of olefin-maleic anhydride copolymers, naphthalenesulfonate formalin condensates, salts of alkyl polyoxyalkylene sulfoalkyl ethers, and salts of alkenyl polyoxyalkylene sulfoalkyl ethers.

[0035] The cationic surfactant is not particularly limited, and conventionally known surfactants can be used, such as alkylamine salts, quaternary ammonium salts (e.g., hexadecyltrimethylammonium chloride), polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.

[0036] The amphoteric surfactant is not particularly limited, and conventionally known surfactants can be used, such as carboxybetaine, aminocarboxylic acid, sulfobetaine, aminosulfuric acid ester, and imitazoline.

[0037] The concentration of the emulsifier is preferably more than 0% by mass and not more than 20% by mass, more preferably 0.005% by mass to 15% by mass, even more preferably 0.01% by mass to 12% by mass, and most preferably 1% by mass to 10% by mass, relative to the total mass of the emulsion, which is a mixture of an oil phase and an aqueous phase.

[0038] The aqueous phase may contain other ingredients such as ultraviolet absorbers, antioxidants, preservatives, etc., as needed.

[0039] When the continuous phase of the present invention is an oil phase, it may further contain components such as a solvent and / or an additive.

[0040] Examples of solvents include fatty acid ester compounds such as caprylic / capric triglyceride and isopropyl myristate, alkylnaphthalene compounds such as diisopropylnaphthalene, diarylalkane compounds such as 1-phenyl-1-xylylethane, alkylbiphenyl compounds such as isopropylbiphenyl, triarylmethane compounds, alkylbenzene compounds, benzylnaphthalene compounds, diarylalkylene compounds, and arylindane compounds; aromatic hydrocarbons such as dibutyl phthalate, paraffin, and isoparaffin; natural animal and vegetable oils such as silicone oil, camellia oil, soybean oil, corn oil, cottonseed oil, rapeseed oil, olive oil, palm oil, castor oil, and fish oil; and high-boiling fractions of natural products such as mineral oil.

[0041] The solvent may contain the surfactants described above.Additives such as ultraviolet absorbers, light stabilizers, antioxidants, waxes, and odor suppressants may also be encapsulated in the microcapsules as needed.

[0042] The additives can be contained in an amount of, for example, 0 to 20% by mass, preferably 1 to 15% by mass, and more preferably 5 to 10% by mass, relative to the total mass of the core material.

[0043] <Emulsion formation process> The formation of an emulsion refers to dispersing a liquid phase (dispersed phase) that is insoluble in the solvent of the continuous phase of the present invention as emulsion particles in the continuous phase of the present invention. Emulsification can be carried out using means commonly used for dispersing a dispersed phase and a continuous phase, such as a general-purpose stirrer, homogenizer, Manton-Gauley, ultrasonic disperser, dissolver, Kady mill, or other known dispersing devices. In forming emulsion (1), the dispersed phase material that will become emulsion particles (1) is dispersed in the continuous phase to form emulsion (1). The above emulsion formation process can also be applied to emulsion (2) of the present invention, which contains a compound (film-forming substance) that can polymerize at the interface with emulsion particles (1) in emulsion (1).

[0044] The emulsion (2) of the present invention may be prepared by emulsifying film-forming monomers, which react with each other to form a film, as a dispersed phase (emulsion particles (2)) in a continuous phase, or by using a co-solvent as a dispersed phase that is insoluble in the continuous phase solvent but is capable of dissolving the film-forming monomers. Examples of co-solvents include ketone compounds such as methyl ethyl ketone, ester compounds such as ethyl acetate, and alcohol compounds such as isopropyl alcohol.

[0045] The emulsion particles (2) in the emulsion (2) preferably have a solubility of 5% by weight or more relative to the emulsion particles (1) in the emulsion (1). The solubility is the degree to which the emulsion particles (2) dissolve in the emulsion particles (1). High solubility facilitates the formation of a membrane (a microcapsule shell) during the subsequent polymerization reaction (interfacial polymerization reaction). The solubility should be 12% by weight or more, preferably 10% by weight or more, and more preferably 5% by weight or more, with the upper limit being 88% by weight, preferably 90% by weight, and more preferably 95% by weight.

[0046] As a specific example, when ethylenediamine is used as the dispersed phase, polyvinylpyrrolidone is used as a dispersion stabilizer, and an emulsion is formed by dispersing it in a continuous phase consisting of a paraffin-based solvent at a predetermined stirring speed. This results in emulsion (1). Meanwhile, the corresponding emulsion (2) is formed by dispersing it in the same paraffin-based solvent as the polyisocyanate at a predetermined stirring speed. The particle size of the dispersed phase can be controlled by changing the stirring speed or the stirring blade used. In another example, emulsion (1) is formed by blending a hydrophobic substance, imidazole, with polyisocyanate as the dispersed phase and dispersing it in a paraffin-based solvent at a predetermined stirring speed. Meanwhile, emulsion (2) is formed by dispersing hexamethylenediamine as the dispersed phase and a paraffin-based solvent as the continuous phase at a predetermined stirring speed. For example, when an adduct of bisphenol A epoxy resin (curing agent or curing accelerator for epoxy resin) is used as the core agent of emulsion particles (1) of emulsion (1), first, imidazole and methyl ethyl ketone are mixed with bisphenol A epoxy resin to form an adduct, which can be used as emulsion (1) by dispersing it in a paraffin solvent at a predetermined stirring speed. When this is used in place of imidazole in emulsion (1) using the above polyisocyanate and imidazole, and combined with emulsion (2) formed from hexamethylenediamine, microcapsules can be formed in which the epoxy resin curing agent or curing accelerator is encapsulated in the core of the microcapsule.

[0047] <Microcapsule formation process> The microcapsule formation process involves mixing the emulsions (1) and (2) formed above and polymerizing them (interfacial polymerization) to form the shells (films) of the microcapsules. The polymerization reaction is initiated by the collision of emulsion particles (1) in emulsion (1) with emulsion particles (2) containing a film-forming substance in emulsion (2), which coalesce at their interface, thereby forming the shells (films) of the microcapsules. The polymerization reaction is preferably carried out under heating. The polymerization temperature is typically 40°C to 100°C, more preferably 50°C to 80°C. The higher the polymerization temperature, the shorter the polymerization time, but a faster reaction may lead to increased aggregation. In this case, it is desirable to initiate the reaction at a relatively low temperature and then raise the temperature.

[0048] According to the inventors' investigations, it was found that when the solubility of emulsion particles (2) in emulsion particles (1) is 5% by weight or more, emulsion particles (2) contained in emulsion (2) tend to collide with emulsion particles (1) contained in emulsion (1) during the production of microcapsules, and coalesce, thereby promoting the formation of a shell (film). The combination is not particularly limited as long as the solubility is 5% by weight or more. For example, when the core agent is water-soluble and a cosolvent is used in emulsion (2), diethyl ether, which has a solubility of 6.9% in water, ethyl acetate, which has a solubility of 8.3%, or methyl ethyl ketone, acetone, or tetrahydrofuran, which has a solubility of 27.5%, can be used. When emulsion particles (1) are an imidazole compound, amines highly soluble in imidazole, such as ethylenediamine or hexamethylenediamine, can be used alone in emulsion (2).

[0049] In order to stably maintain the performance of the capsules of the present invention, it is desirable that the capsules have a uniform size. To this end, it is preferable that the average particle size of emulsion particles (1) in emulsion (1) before and after the addition of emulsion (2) of the present invention is uniform, and it is preferable that the distribution of the average particle size is less than 1.3 times the average particle size.

[0050] As a means for making the average particle size of the microcapsules of the present invention uniform, after emulsification of emulsion (1), the size of emulsion particles (1) of emulsion (1) can be grown to a desired size, and then emulsion (2) can be added. Growing the average particle size of emulsion particles to a desired size means increasing the droplet size by coalescence of emulsion particles (1) of emulsion (1), and the desired size of emulsion particles (1) can be obtained by adjusting the shear force and shear time in conjunction with changes in the viscosity of the continuous phase and the stirring speed.

[0051] The inventors discovered that by maintaining a constant stirring speed after forming emulsion (1), the variance (standard deviation) in the average particle size distribution of emulsion particles (1) does not expand beyond a certain level, even as the average droplet size grows. As a result, it was found that even after the emulsion particles consisting of emulsion (2) and emulsion (1) coalesce, their diameter remains less than 1.3 times larger. In other words, the rate of increase in the average particle size (R) during the microcapsule formation process is less than 1.3 times larger.

[0052] The timing of adding emulsion (2) is preferably such that emulsion (2) is added at the point when the increase in the dispersion value of the average particle size of the emulsion particles due to stirring of emulsion (1) reaches a plateau, and coalescence begins, since this reduces the difference in particle size before and after the addition.

[0053] The average particle size (R) of emulsion particles (1) made of emulsion (1) of the present invention is preferably 0.1 to 300 μm. If the average particle size of emulsion particles (1) is less than 0.1 μm, the emulsion particles (1) may aggregate, inhibiting the reaction. If the average particle size of emulsion particles (1) exceeds 300 μm, it may be impossible to produce microcapsules with a small particle size. The upper limit of the average particle size of emulsion particles (1) is preferably 100 μm, and more preferably 50 μm. The average particle size of emulsion particles of emulsions (1) and (2) refers to the average particle size of droplets measured using a microscope or the like. However, if the average particle size of emulsion particles is less than 1 μm, the average particle size of droplets is determined using a particle size distribution measuring device or the like.

[0054] The average particle size (r) of the emulsion particles (2) made from the emulsion (2) is preferably 10% or less of the average particle size (R) of the emulsion particles (1) made from the emulsion (1) (i.e., r / R≦0.1), specifically 0.01 to 30 μm, and preferably 0.01 to 10 μm. If the average particle size ratio (r / R) exceeds 0.1, the polymerization reaction caused by coalescence of the emulsion particles (2) with the emulsion particles (1) is not prioritized, and the emulsion particles (1) or the emulsion particles (2) coalesce with each other, which undesirably affects the performance of the microcapsules themselves.

[0055] The emulsion particles (2) of the emulsion (2) of the present invention can be produced by a general inkjet method. For example, the emulsion particles (2) of the present invention can be ejected from a piezoelectric inkjet nozzle and combined with the emulsion particles (1).

[0056] The emulsion formation step of the present invention is suitable for both O / W and W / O emulsions, but O / O' is preferred to maintain the stability of emulsion particles (2) in emulsion (2), and it is desirable that O' has a higher viscosity than water. High viscosity can suppress coalescence of emulsion particles (2) and promote coalescence with emulsion particles (1). Furthermore, the higher the interfacial tension of emulsion (2), the less susceptible to deformation and the more promoted the coalescence of emulsion (1) with emulsion particles (1), which is preferable.

[0057] When an aliphatic hydrocarbon solvent is used for the oil phase, the larger the carbon number, the more stable the droplets will be, which is preferable.

[0058] The shell of the microcapsules in the present invention preferably contains polyurethane or polyurea derived from a polyisocyanate structure.

[0059] The average shell (film) thickness of the microcapsules of the present invention preferably has a lower limit of 0.01 μm and an upper limit of 5.0 μm. If the average shell thickness is less than 0.01 μm, the retention of the core agent may decrease. If the average shell thickness is more than 5.0 μm, the release of the water-soluble core agent may decrease. A more preferred lower limit of the average shell thickness is 0.08 μm, and a more preferred upper limit is 1.0 μm.

[0060] The average shell thickness is the average value obtained by averaging the wall thicknesses (μm) of 10 microcapsules measured using a scanning electron microscope (SEM). Specifically, the microcapsule liquid is applied to a substrate and dried to form a coating film. A cross-section of the resulting coating film is prepared and observed using an SEM. Ten randomly selected microcapsules are then observed, their cross-sections are measured, and the average wall thickness is calculated.

[0061] The polymerization reaction time for producing the microcapsules of the present invention is usually preferably about 0.5 to 10 hours, and more preferably about 1 to 6 hours. By reducing r / R as described above, the reaction time can be reduced to 4 hours or less, which is preferable from the viewpoint of productivity. The polymerization reaction time here refers to the time from the addition of emulsion (2) to emulsion (1) until the start of the washing process described below.

[0062] Furthermore, a polymerization reaction time that is too short means that unreacted components remain or the reaction ends before sufficient film strength is achieved, whereas a reaction time that is too long can result in unnecessary reactions occurring outside the interface, sometimes leading to non-uniformity between microcapsules or aggregation of microcapsules.

[0063] The resulting microcapsules may be coated, if necessary. The method for coating the microcapsules is not particularly limited, and examples include interfacial polymerization using a substance that reacts with the capsule's film-forming substance. When the film-forming substance is localized on the particle surface, the substance that reacts with the film-forming substance can be added to the particle surface by emulsifying the continuous phase and the film-forming substance, as in the case of adding emulsion (2) of the present invention, and then adding the resulting emulsion, consisting of droplets containing the film-forming substance, to the reaction solution, thereby coating the capsule surface. Coating the microcapsules is preferable from the viewpoint of preventing leakage of the core agent of the microcapsules. The amount of the substance that reacts with the film-forming substance is equal to or less than the equivalent of the film-forming substance contained in emulsion (2), preferably 1 / 10 or less. For example, an epoxy compound can be used as a substance that reacts with the amine film-forming substance, in an amount equal to or less than the hydrogen equivalent of the amine, preferably 1 / 10 or less, and more preferably 1 / 50 or less. The above-mentioned epoxy compounds may be used alone or in combination of two or more. The emulsion comprising droplets containing a substance reactive with the film-forming material may be added to the reaction solution at any time between the end of the addition of emulsion (2) of the present invention and the end of the reaction. The preferred addition time is 1 hour, more preferably 30 minutes, before the end of the reaction, from the viewpoint of film formation.

[0064] The obtained microcapsules may be washed repeatedly with a solvent such as water, hexane, toluene, or ethyl acetate, and then dried by vacuum drying or the like.

[0065] The final average particle size of the microcapsules of the present invention is 0.1 to 4000 μm, preferably 0.1 to 350 μm, and more preferably 0.1 to 310 μm. Producing capsules smaller than 0.1 μm results in a reduced amount of core material. Microcapsules larger than 400 μm can also be produced, but the benefits of using the manufacturing method of the present invention are reduced. The microcapsules of the present invention can be used with many core materials and can be used for a variety of purposes. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0067] <Preparation of microcapsules encapsulating aqueous solutions> Example 1 Two parts by weight of ethylenediamine (Fujifilm Wako Pure Chemical Industries, Ltd.) as a film-forming monomer and 30 parts by weight of a 10% aqueous solution of polyvinylpyrrolidone as a water-soluble core agent were mixed and dissolved to obtain solution (1). This solution (1) was added to 120 parts by weight of a paraffin-based solvent (Moresco White P-100, manufactured by MORESCO Corporation) (containing 5% by weight of Sunsoft 818R (manufactured by Taiyo Kagaku Co., Ltd.) as an emulsifier), and the mixture was stirred at 550 rpm using a stirrer to prepare emulsion (1) in which emulsion particles (1) were dispersed. The droplet diameter (average particle size) of emulsion particles (1) was measured using a microscope (Keyence VHX-6000) and found to be 101.5 μm.

[0068] Separately, 30 parts by weight of Stabio D-370N (Mitsui Chemicals), a polyisocyanate that reacts with ethylenediamine to form a film, was dissolved in 30 parts by weight of ethyl acetate, and the resulting solution was added to 600 parts by weight of a paraffinic solvent (Moresco White P-100, MORESCO) (containing 7% by weight of Sunsoft 818R (Taiyo Kagaku Co., Ltd.) as an emulsifier). The mixture was stirred at 10,000 rpm using a homomixer (PRIMIX MARK II) to prepare emulsion (2) in which emulsion particles (2) were dispersed. The droplet diameter (average particle size) of emulsion particles (2) was measured using a microscope (Keyence VHX-6000) and found to be 10.1 μm.

[0069] The resulting emulsion (1) was placed in a jacketed stirring reactor, and emulsion (2) was added while stirring at 250 rpm. After stirring at room temperature for 60 minutes, warm water was passed through the reaction solution to bring it to 50°C, and the reaction was carried out at 50°C for 240 minutes. After the reaction was completed, the reaction solution was poured into toluene in an amount twice the volume of the reaction solution, and microcapsules were obtained by suction filtration. The particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and found to be 103.8 μm.

[0070] The solubility of the emulsion particles (2) in the emulsion particles (1) was 8.3.

[0071] The moisture content of the microcapsules was measured using an infrared moisture meter (FD-720, manufactured by Kett Electric Laboratory Co., Ltd.) and found to be 62.0%.

[0072] Example 2 Emulsion (2) in which emulsion particles (2) were dispersed was prepared in the same manner as in Example 1, except that the rotation speed of a homomixer (MARKII manufactured by PRIMIX Corporation) was changed to 15,000 rpm. The droplet diameter (average particle diameter) of emulsion particles (2) was measured using a microscope (VHX-6000 manufactured by Keyence Corporation) and was found to be 4.8 μm.

[0073] Microcapsules were obtained in the same manner as in Example 1, except that emulsion (2) was added to emulsion (1) in the same manner as in Example 1, followed by stirring at room temperature for 60 minutes, warm water was passed through the reaction solution to bring the temperature to 50°C, and the reaction was carried out at 50°C for 150 minutes. The particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and found to be 102.8 μm.

[0074] The solubility of the emulsion particles (2) in the emulsion particles (1) was 8.3.

[0075] The moisture content of the microcapsules was measured using an infrared moisture meter (FD-720 manufactured by Kett Electric Laboratory Co., Ltd.) and found to be 63.0%.

[0076] Example 3 Emulsion (1) was prepared in the same manner as in Example 1, except that the stirring speed was changed to 250 rpm. The droplet diameter (average particle diameter) of emulsion particles (1) was measured using a microscope (Keyence VHX-6000) and found to be 200.7 μm.

[0077] As in Example 1, emulsion (1) was charged into a jacketed stirring reaction vessel, and then emulsion (2) from Example 1 was added while stirring at 150 rpm. After stirring at room temperature for 60 minutes, warm water was passed through the reaction solution to bring it to 50° C., and the reaction was carried out at 50° C. for 180 minutes, but microcapsules were obtained in the same manner as in Example 1. The particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and was found to be 205.3 μm.

[0078] The solubility of the emulsion particles (2) in the emulsion particles (1) was 8.3.

[0079] The moisture content of the microcapsules was measured using an infrared moisture meter (FD-720 manufactured by Kett Electric Laboratory Co., Ltd.) and found to be 61.0%.

[0080] Example 4 In the same manner as in Example 3, emulsion (2) in which emulsion particles (2) were dispersed was prepared by changing the rotation speed of a homomixer (MARK II manufactured by PRIMIX Corporation) to 5000 rpm. The droplet diameter (average particle diameter) of emulsion particles (2) was measured using a microscope (VHX-6000 manufactured by Keyence Corporation) and was found to be 20.0 μm.

[0081] Microcapsules were obtained in the same manner as in Example 3, except that emulsion (2) was added to emulsion (1) in the same manner as in Example 3, followed by stirring at room temperature for 60 minutes, warm water was passed through the reaction solution to bring it to 50°C, and the reaction was carried out at 50°C for 300 minutes. The particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and found to be 210.0 μm.

[0082] The solubility of the emulsion particles (2) in the emulsion particles (1) was 8.3.

[0083] The moisture content of the microcapsules was measured using an infrared moisture meter (FD-720 manufactured by Kett Electric Laboratory Co., Ltd.) and found to be 60.0%.

[0084] Example 5 Emulsion (2) was prepared in the same manner as in Example 1, except that in preparing solution (1), ethylenediamine was replaced with 2 parts by weight of 1,4-butanediol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and in preparing solution (2), 1.5 parts by weight of 1,4-diazabicyclo[2.2.2]octane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a catalyst to a solution of 30 parts by weight of Stabio D-370N (manufactured by Mitsui Chemicals, Inc.) and 30 parts by weight of ethyl acetate.

[0085] The droplet diameter (average droplet diameter) of droplets consisting of solution (1) was measured using a microscope (VHX-6000, manufactured by Keyence Corporation) and was found to be 103.0 μm. On the other hand, the droplet diameter (average droplet diameter) of droplets consisting of solution (2) was measured using a microscope (VHX-6000, manufactured by Keyence Corporation) and was found to be 10.2 μm. The particle diameter (average particle diameter) of the resulting microcapsules was measured using a microscope (VHX-6000, manufactured by Keyence Corporation) and was found to be 105.4 μm.

[0086] The moisture content of the microcapsules was measured using an infrared moisture meter (FD-720, manufactured by Kett Electric Laboratory Co., Ltd.) and found to be 65.0%.

[0087] (Comparative Example 1) In the preparation of emulsion (2) in the same manner as in Example 1, 30 parts by weight of Stabio D-370N (manufactured by Mitsui Chemicals, Inc.) was added directly to the jacketed stirred reactor containing emulsion (1). Although the mixture was allowed to react for a total of 8 hours with stirring at room temperature and at 50°C, emulsion (2) was not formed, and therefore no coating was formed, and microcapsules could not be obtained.

[0088] (Comparative Example 2) Emulsion (2) was prepared in the same manner as in Example 1. 30 parts by weight of STABIO D-370N (Mitsui Chemicals, Inc.) was added to 600 parts by weight of a paraffinic solvent (MORESCO White P-100, MORESCO) without dissolving it in ethyl acetate (containing 7% by weight of Sunsoft 818R (Taiyo Kagaku Co., Ltd.) as an emulsifier). The mixture was stirred at 10,000 rpm using a homomixer (PRIMIX MARK II) to prepare emulsion (2) in which emulsion particles (2) were dispersed. The droplet size (average particle size) of emulsion particles (2) was measured using a microscope (Keyence VHX-6000) and found to be 27.3 μm. The r / R ratio was 0.269.

[0089] The obtained emulsion (1) was placed in a jacketed stirred reaction vessel, and then emulsion (2) was added while stirring at 250 rpm. During the reaction, the particles aggregated and could not be dispersed, and microcapsules could not be obtained.

[0090] (Comparative Example 3) In the same manner as in Example 1, emulsion (2) was prepared by adding 30 parts by weight of STABIO D-370N (Mitsui Chemicals) without dissolving it in ethyl acetate to 600 parts by weight of a paraffinic solvent (MORESCO White P-100) (containing 7% by weight of Sunsoft 818R (Taiyo Kagaku Co., Ltd.) as an emulsifier), and stirring at 15,000 rpm using a homomixer (PRIMIX MARK II) to prepare emulsion (2) in which emulsion particles (2) were dispersed. The droplet diameter (average particle diameter) of emulsion particles (2) was measured using a microscope (Keyence VHX-6000) and found to be 9.8 μm.

[0091] The resulting emulsion (1) was placed in a jacketed stirring reaction vessel, and emulsion (2) was added while stirring at 250 rpm. After stirring at room temperature for 60 minutes, warm water was passed through the reaction solution to bring it to 50°C, and the reaction was carried out at 50°C. Sampling during the reaction showed a particle size of 101.5 μm, but the coating was weak, so the reaction was carried out for a total of 8 hours by stirring at room temperature and at 50°C. The reaction solution was placed in toluene in an amount twice the volume of the reaction solution, and the microcapsules were crushed during suction filtration, forming agglomerates, and no microcapsules were obtained.

[0092] Comparative Example 4 Emulsion (2) was prepared in the same manner as in Example 1. 30 parts by weight of STABIO D-370N (Mitsui Chemicals, Inc.) was dissolved in 30 parts by weight of ethyl acetate, and the resulting solution was added to 600 parts by weight of a paraffin-based solvent (MORESCO White P-100) containing 7% by weight of Sunsoft 818R (Taiyo Kagaku Co., Ltd.) as an emulsifier. The mixture was stirred at 5,000 rpm using a homomixer (PRIMIX MARK II) to prepare emulsion (2) containing dispersed emulsion particles (2). The droplet size (average particle size) of emulsion particles (2) was measured using a microscope (Keyence VHX-6000) and found to be 31.3 μm. The r / R value was 0.3084.

[0093] The resulting emulsion (1) was placed in a jacketed stirring reactor, and emulsion (2) was added while stirring at 250 rpm. After stirring for 60 minutes at room temperature, warm water was passed through the reaction solution to bring it to 50°C, and the reaction was continued at 50°C for 180 minutes. After the reaction was completed, the reaction solution was poured into toluene in an amount twice the volume of the reaction solution, and microcapsules were obtained by suction filtration. The particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and found to be 130.3 μm. However, water encapsulated in the microcapsules had leaked. The moisture content of the microcapsules was measured using an infrared moisture meter (Kett Electric Laboratory FD-720), and the moisture content of the microcapsules was found to be 25.0%.

[0094] <Preparation of microcapsules encapsulating hydrophobic substances> Example 6 10 parts by weight of polyisocyanate Stabio D-370N (Mitsui Chemicals, Inc.), 3 parts by weight of Takenate D-262 (Mitsui Chemicals, Inc.), and 32 parts by weight of hydrophobic substance 1-benzyl-2-methylimidazole were mixed and dissolved to obtain solution (1). This solution (1) was added to 300 parts by weight of a paraffinic solvent (Moresco White P-100, MORESCO Corporation) (containing 0.5 wt% of KF-6038 (Shin-Etsu Silicones Co., Ltd.) as an emulsifier), and the mixture was stirred at 4500 rpm using a homomixer (PRIMIX MARK II) to prepare emulsion (1) in which emulsion particles (1) were dispersed. The droplet size (average particle size) of emulsion particles (1) was measured using a microscope (Keyence VHX-6000) and found to be 15.1 μm.

[0095] Separately, 4 parts by weight of hexamethylenediamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to 300 parts by weight of a paraffinic solvent (MORESCO White P-100 manufactured by MORESCO) (containing 0.5% by weight of KF-6038 (manufactured by Shin-Etsu Silicones) as an emulsifier), and the mixture was stirred at 8000 rpm using a homomixer (MARK II manufactured by PRIMIX Corporation) to prepare emulsion (2) in which emulsion particles (2) were dispersed. The droplet diameter (average particle diameter) of emulsion particles (2) was measured using a microscope (VHX-6000 manufactured by Keyence Corporation) and found to be 1.5 μm.

[0096] The resulting emulsion (1) was placed in a jacketed stirring reactor, and emulsion (2) was quickly added while stirring at 250 rpm. After stirring at room temperature for 60 minutes, warm water was passed through the reaction solution to bring it to 50°C, and the reaction was continued at 50°C for 150 minutes. After the reaction was completed, the reaction solution was poured into hexane in an amount twice the volume of the reaction solution, and microcapsules were obtained by suction filtration. The particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and found to be 15.8 μm.

[0097] Example 7 Microcapsules were obtained by changing the following in Example 6. Microcapsules were obtained in the same manner as in Example 2, except that emulsion (1) was charged into a jacketed stirred reaction vessel, stirred at 250 rpm for 90 minutes, and then emulsion (2) was added. Note that, when emulsion (2) was added, the average particle size was measured every 10 minutes after emulsion (1) was charged into the jacketed stirred reaction vessel, and emulsion (2) was added after it was confirmed that the dispersion value (standard deviation) did not spread and the droplet diameter (average particle size) was 19.2 μm.

[0098] After the reaction was completed, the particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and found to be 19.8 μm.

[0099] Example 8 Microcapsules were obtained by changing the following in Example 6. In preparing emulsion (1), instead of stirring at 4500 rpm using a homomixer (MARK II manufactured by PRIMIX Corporation), the rotation speed was changed to 400 rpm using a Three-One motor, and emulsion (1) in which emulsion particles (1) were dispersed was prepared. The droplet diameter (average particle diameter) of emulsion particles (1) was measured using a microscope (VHX-6000 manufactured by Keyence Corporation) and was found to be 98.5 μm.

[0100] Next, in the preparation of emulsion (2) in Example 6, the rotation speed using a homomixer (MARKII manufactured by PRIMIX Corporation) was changed to 2000 rpm, and emulsion (2) in which emulsion particles (2) were dispersed was prepared. Except for this, microcapsules were obtained in the same manner as in Example 6. The droplet diameter (average particle diameter) of emulsion particles (2) was measured using a microscope (VHX-6000 manufactured by Keyence Corporation) and was found to be 7.8 μm.

[0101] After the reaction was completed, the particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and found to be 105.0 μm.

[0102] (Comparative Example 5) In the preparation of emulsion (2) in Example 6, emulsion (2) in which emulsion particles (2) were dispersed was prepared by stirring at 4000 rpm using a homomixer (MARK II manufactured by PRIMIX Corporation). The droplet diameter (average particle diameter) of emulsion particles (2) was measured using a microscope (VHX-6000 manufactured by Keyence Corporation) and found to be 3.0 μm. The reaction was carried out in the same manner as in Example 6 to obtain microcapsules. The r / R value was 0.1987.

[0103] The particle size (average particle size) of the microcapsules was measured using a microscope (Keyence VHX-6000) and was found to be 22.0 μm.

[0104] <Evaluation> Hardness test (pressure resistance) The pressure resistance of the microcapsules obtained in Examples 6, 7, and 8 and Comparative Example 5 was evaluated using commercially available oil blotting paper as follows.

[0105] The microcapsules placed on top of the commercially available blotting paper were also placed on top of the blotting paper, and the pressure applied to the microcapsules was reduced from 45 N using the hardness mode of a small tabletop tester, Eztest (Shimadzu Corporation). The pressure at which the hydrophobic substance encapsulated in the microcapsules seeped out and was absorbed by the blotting paper (exudation was detected) was confirmed, and the pressure at which exudation was no longer detected (reported as pressure resistance) was determined. The results are shown in Table 1.

[0106] [Table 1]

[0107] It has been found that the microcapsules of the present invention have excellent resistance to pressure because the individual particles are uniformly aligned, making it difficult for the contents to leak when pressure is applied.

[0108] <Preparation of microcapsules encapsulating epoxy resin adducts> Example 9 Preparation of adduct A Adduct A was prepared by stirring 17.2 parts by weight of 1-benzyl-2-methylimidazole, 6.33 parts by weight of bisphenol A epoxy resin (jER828 manufactured by Mitsubishi Chemical Corporation) and 20 ml of methyl ethyl ketone at 30° C. for 1 hour or more.

[0109] Microcapsules were obtained in the same manner as in Example 6, except that the hydrophobic substance 1-benzyl-2-methylimidazole was replaced with 32 parts by weight of the above adduct. The particle size R of emulsion particles (1) was 15.1 μm, and the particle size r of emulsion particles (2) was 1.5 μm. Therefore, the value of r / R was 0.0993.

[0110] Example 10 <Creation of adduct B> 5.80 parts by weight of 2-methylimidazole, 4.47 parts by weight of bisphenol A type epoxy resin (jER828 manufactured by Mitsubishi Chemical Corporation), and 80 ml of methyl ethyl ketone were stirred at 30° C. for at least 1 hour and then cooled to room temperature to prepare adduct B.

[0111] Microcapsules were obtained in the same manner as in Example 6, except that the hydrophobic substance 1-benzyl-2-methylimidazole was replaced with 32 parts by weight of the above adduct B. The particle size R of emulsion particles (1) was 15.1 μm, and the particle size r of emulsion particles (2) was 1.3 μm. Therefore, the value of r / R was 0.0861.

[0112] Example 11 <Creation of adduct C> 10.2 parts by weight of 2-phenylimidazole, 4.47 parts by weight of bisphenol A type epoxy resin (jER828 manufactured by Mitsubishi Chemical Corporation), and 80 ml of methyl ethyl ketone were stirred at 30° C. for at least 1 hour and then cooled to room temperature to prepare adduct C.

[0113] Microcapsules were obtained in the same manner as in Example 6, except that the hydrophobic substance 1-benzyl-2-methylimidazole was replaced with 32 parts by weight of the above adduct C. The particle size R of emulsion particles (1) was 15.1 μm, and the particle size r of emulsion particles (2) was 1.4 μm. Therefore, the value of r / R was 0.0927.

[0114] It has been found that the microcapsules of the present invention have superior storage stability due to microencapsulation compared to when a curing agent is used alone, and furthermore, by making the encapsulated substance an epoxy resin adduct, the storage stability is significantly improved.

[0115] Table 2 below shows the particle size (R μm) of emulsion (1), particle size (r μm) of emulsion (2), value of r / R, solubility (%) of emulsion particle (2) in emulsion particle (1), particle size (μm) of the obtained microcapsules, and water content (%) of the obtained microcapsules for the examples and comparative examples. [Table 2]

Claims

1. A method for producing microcapsules using two types of emulsion particles with different sizes, comprising: an emulsion-forming step of separately forming two types of emulsions (1) and (2) having a common continuous phase, and incorporating one of two types of monomers that react with each other to form a film into emulsion particles (1) of emulsion (1) and the other monomer into emulsion particles (2) of emulsion (2); a microcapsule formation step of mixing the emulsion (1) and the emulsion (2) and subjecting them to interfacial polymerization; It consists of one of the two types of monomers that react with each other to form a coating contains an isocyanurate-type polyisocyanate compound having three or more isocyanate groups, and the other monomer contains at least one monomer selected from the group consisting of ethylenediamine, hexamethylenediamine, and 1,4-butanediol; The emulsion particles (1) of the emulsion (1) have an average particle size (R) of 15.1 to 300 μm, the emulsion particles (2) of the emulsion (2) have an average particle size (r) of 1.3 to 30 μm, and r / R≦0.1; and the emulsion particles (2) of the emulsion (2) have a solubility of 5% by weight or more relative to the emulsion particles (1) of the emulsion (1); the continuous phase is liquid paraffin or silicone oil; A method for producing microcapsules, characterized in that in the microcapsule formation step, the polymerization reaction temperature is 40°C to 100°C, and the polymerization reaction time is 0.5 hours to 10 hours.

2. A method for producing microcapsules according to claim 1, wherein the average particle size (R) of the emulsion particles (1) is 15.1 to 100 μm, the average particle size (r) of the emulsion particles (2) is 1.3 to 10 μm, and r / R≦0.

1.

3. 3. The method for producing microcapsules according to claim 1, wherein the average particle size (R) of the emulsion particles (1) or the average particle size (r) of the emulsion particles (2) is adjusted to fall within a predetermined range after the emulsion formation step.

4. A method for producing microcapsules described in any one of claims 1 to 3, wherein the rate of increase in average particle size (R) during the microcapsule formation process is less than 1.3 times.

5. A method for producing a microcapsule described in any one of claims 1 to 4, wherein the core agent of the microcapsule is water, a water-soluble heat storage material, a thermally expandable hydrocarbon or a fluoride of a thermally expandable hydrocarbon, an epoxy resin curing agent or an epoxy resin curing accelerator.

6. The method for producing microcapsules according to claim 5 , wherein the epoxy resin curing agent is an adduct containing an epoxy resin and an amine compound.

7. 7. The method for producing microcapsules according to claim 5, wherein the epoxy resin curing agent is an adduct, which is a liquid mixture obtained by mixing an epoxy resin and an amine compound in advance and then heating and stirring the mixture.

8. The method for producing microcapsules according to claim 5, wherein the epoxy resin curing agent is an adduct containing an epoxy resin and an imidazole compound.

9. 9. The method for producing microcapsules according to claim 5, wherein the epoxy resin curing agent is an adduct, which is a liquid mixture obtained by mixing an epoxy resin and an imidazole compound in advance and then heating and stirring the mixture.

10. The method for producing microcapsules according to any one of claims 6 to 9, wherein the epoxy resin is a bisphenol A type epoxy resin.

11. The method for producing microcapsules according to any one of claims 1 to 10, characterized in that the polymerization reaction time in the microcapsule formation step is 6 hours or less.

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