Microcapsule

Abstract

To provide a microcapsule that enables sufficient acquisition of a refreshing sensation.SOLUTION: A microcapsule encapsulates a refreshing component and a solvent having a vapor pressure at 25°C of 0.1 mmHg or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to microcapsules. [Background technology]

[0002] Microcapsules are constructed by encapsulating a target component as a core substance in a wall material, and can be made to have sustained release properties, gradually releasing the encapsulated oily component to the outside over time.

[0003] Furthermore, a technique of blending 1-menthol into a skin cosmetic for the purpose of providing a refreshing feeling to the skin when the skin cosmetic is applied has been known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-280533 Summary of the Invention [Problem to be solved by the invention]

[0005] However, microcapsules containing l-menthol as a cooling agent have a weak cooling sensation that cannot be felt sufficiently. Also, there are methods in which peppermint oil or eucalyptus oil is added in addition to l-menthol, but these also do not provide a sufficient cooling sensation (see Patent Document 1).

[0006] Cooling agents containing l-menthol do not actually lower the temperature, but rather act on the human nervous system, TRPM8, to create a feeling of coolness. However, TRPM8 is not activated at temperatures between 23 and 26 degrees Celsius. Therefore, l-menthol alone does not provide a sufficient cooling sensation.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide microcapsules that can provide a sufficient cooling sensation. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention employs the following configuration. [1] Microcapsules containing a cooling ingredient and a solvent with a vapor pressure of 0.1 mmHg or more at 25°C. [2] The microcapsules according to [1], wherein the cooling component is one or more selected from the group consisting of l-menthol, l-menthol derivatives, and 2-isopropyl-N,2,3-trimethylbutyramide. [3] The resin sheet according to [1] or [2], wherein the wall material of the microcapsules contains gelatin. [4] The resin sheet according to any one of [1] to [3], wherein the solvent is a cyclic siloxane. [Effects of the Invention]

[0009] According to the present invention, microcapsules that can provide a sufficient cooling sensation are provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] <<Microcapsules>> A microcapsule according to one embodiment of the present invention encapsulates a cooling component and a solvent having a vapor pressure of 0.1 mmHg or more at 25° C. as a core substance. In this specification, "a vapor pressure of 0.1 mmHg or more at 25°C" may be expressed as "a vapor pressure of 0.1 mmHg or more (25°C)."

[0011] <Refreshing ingredient> The cooling component is the core material in the microcapsules of this embodiment. The cooling component constituting the microcapsules (in other words, encapsulated in the wall material) may be one type or two or more types, and if there are two or more types, the combination and ratio thereof can be selected arbitrarily.

[0012] The refreshing ingredient is preferably hydrophobic, which can further improve the ability of the microcapsules to stably encapsulate the core substance (encapsulation and retention performance).

[0013] The cooling component is preferably solid at room temperature. In this specification, "room temperature" means a temperature that is neither particularly cold nor hot, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

[0014] The cooling component is preferably one or more selected from the group consisting of, for example, l-menthol, l-menthol derivatives, and 2-isopropyl-N,2,3-trimethylbutyramide.

[0015] In this specification, an l-menthol derivative means a compound having a structure in which one or more hydrogen atoms in l-menthol are substituted with a group other than a hydrogen atom, or a compound having a structure in which one hydroxyl group is substituted with a group other than a hydroxyl group. In this specification, unless otherwise specified, the term "group" includes not only an atomic group formed by bonding multiple atoms but also a single atom.

[0016] Among the above-mentioned l-menthol derivatives, examples of l-menthol derivatives having a structure in which a hydrogen atom in l-menthol is substituted with a group other than a hydrogen atom include menthoxypropanediol. Among the 1-menthol derivatives, examples of 1-menthol derivatives having a structure in which the hydroxyl group in 1-menthol is substituted with a group other than a hydroxyl group include N-ethyl-p-menthane-3-carboxamide, N-((ethoxycarbonyl)methyl)-p-menthane-3-carboxamide, (2S,5R)-2-isopropyl-N-(4-methoxyphenyl)-5-methylcyclohexanecarboximide, etc.

[0017] The strength of the cooling sensation of l-menthol and the l-menthol derivatives is (2S,5R)-2-isopropyl-N-(4-methoxyphenyl)-5-methylcyclohexanecarboximide > N-((ethoxycarbonyl)methyl)-p-menthane-3-carboxamide > N-ethyl-p-menthane-3-carboxamide > l-menthol. The cooling sensation of N-((ethoxycarbonyl)methyl)-p-menthane-3-carboxamide is about 2.5 times stronger than that of N-ethyl-p-menthane-3-carboxamide.

[0018] When a cooling ingredient such as l-menthol comes into contact with the skin, a cool sensation (sometimes abbreviated as "cooling sensation" in this specification) is felt. This is not due to an actual decrease in temperature, but rather to the stimulation of a receptor-activated channel called "TRPM8" that causes the cooling sensation. TRPM8 is activated by cooling agents such as l-menthol, as well as by non-noxious cold stimuli (23-26°C). TRPM8 is expressed in some sensory neurons, and is therefore thought to function as a cold receptor in somatosensory sensation.

[0019] 2-Isopropyl-N,2,3-trimethylbutyramide has a cooling effect slightly inferior to that of N-ethyl-p-menthane-3-carboxamide, but is preferred because it may provide a more sensory cooling sensation than (2S,5R)-2-isopropyl-N-(4-methoxyphenyl)-5-methylcyclohexanecarboximide when brought into contact with the skin.

[0020] In the microcapsules, the total content of the refreshing ingredients is preferably 30 to 500 parts by mass, and may be, for example, 40 to 450 parts by mass or 50 to 400 parts by mass, relative to 100 parts by mass of the total content of the solvents having a vapor pressure of 0.1 mmHg (25°C) or more, as described below. Microcapsules having a total content of the refreshing ingredients in this range can provide a more refreshing feeling.

[0021] In the microcapsules, the total content of the cooling ingredients is preferably 30 to 90 parts by mass, more preferably 35 to 80 parts by mass, and even more preferably 40 to 70 parts by mass, relative to 100 parts by mass of the total content of the core material of the microcapsules. Microcapsules having a total content of the cooling ingredients in this range have better quality and can be produced more easily.

[0022] In the microcapsules, the total content of the refreshing ingredients is preferably 200 to 1200 parts by mass, and may be, for example, 300 to 1000 parts by mass or 400 to 800 parts by mass, relative to 100 parts by mass of the cationic polymer described below. Microcapsules having a total content of the refreshing ingredients in this range have better quality and can be produced more easily.

[0023] <Solvents with a vapor pressure of 0.1 mmHg (25°C) or more> The solvent having a vapor pressure of 0.1 mmHg (25° C.) or more, together with the cooling component, is the core material in the microcapsules of this embodiment.

[0024] By using a solvent with a vapor pressure of 0.1 mmHg (25°C) or higher, the temperature drops due to the latent heat of vaporization, making the liquid feel cooler. Furthermore, when the temperature actually drops to 23 to 26°C, the human nervous system "TRPM8" is activated, and the cooling sensation caused by the cooling component can be felt. As a result, the microcapsules of this embodiment can provide a sufficient cooling sensation.

[0025] The solvent having a vapor pressure of 0.1 mmHg (25°C) or more is preferably hydrophobic, which can further improve the encapsulation and retention performance of the microcapsules.

[0026] The vapor pressure of the solvent having a vapor pressure of 0.1 mmHg (25°C) or more is preferably 0.1 mmHg (25°C) to 100 mmHg (25°C), more preferably 0.5 mmHg (25°C) to 50 mmHg (25°C), even more preferably 2.0 mmHg (25°C) to 25 mmHg (25°C), and particularly preferably 4.0 mmHg (25°C) to 10 mmHg (25°C). Microcapsules having a vapor pressure of 0.1 mmHg (25°C) or more in this range can provide a more refreshing feeling.

[0027] The solvent having a vapor pressure of 0.1 mmHg (25° C.) or more is preferably, for example, cyclic siloxane.

[0028] In the cyclic siloxane, the number of silicon atoms constituting the ring skeleton is preferably 3 to 5. In the cyclic siloxane, the two groups bonded to one silicon atom, other than the oxygen atom that does not constitute the ring skeleton, are preferably alkyl groups, more preferably alkyl groups having 1 to 3 carbon atoms, and even more preferably methyl groups. In the cyclic siloxane, the multiple groups other than the oxygen atom bonded to the silicon atom may all be the same, all be different, or only some may be the same, but it is preferable that they are all the same.

[0029] Examples of the cyclic siloxane include hexamethylcyclotrisiloxane (vapor pressure 5.03 mmHg (25°C)), octamethylcyclotetrasiloxane (vapor pressure 1.05 mmHg (25°C)), decamethylcyclopentasiloxane (vapor pressure 0.3 mmHg (25°C)), etc. Of these, decamethylcyclopentasiloxane is preferred because, like the cooling component, it provides a cooling sensation when brought into contact with the skin.

[0030] The solvent having a vapor pressure of 0.1 mmHg (25°C) or more that constitutes the microcapsules (in other words, that is encapsulated in the wall material) may be one type or two or more types, and if there are two or more types, the combination and ratio of these can be selected arbitrarily.

[0031] In the microcapsules, the total content of the solvents having a vapor pressure of 0.1 mmHg (25°C) or more is preferably 5 to 80 parts by mass, more preferably 10 to 60 parts by mass, and even more preferably 20 to 50 parts by mass, relative to 100 parts by mass of the total content of the core material of the microcapsules. By having the total content of the solvents having a vapor pressure of 0.1 mmHg (25°C) or more in this range, a more refreshing feeling can be obtained.

[0032] In the microcapsules, the total content of the solvents having a vapor pressure of 0.1 mmHg (25°C) or more is preferably 50 to 1200 parts by mass, and may be, for example, 150 to 1000 parts by mass or 250 to 800 parts by mass, relative to 100 parts by mass of the cationic polymer described below. Microcapsules having a total content of the solvents having a vapor pressure of 0.1 mmHg (25°C) or more in this range have better quality and can be produced more easily.

[0033] <Other microcapsule-encapsulated ingredients> The microcapsules may contain, as a core material, other components that do not fall into either the category of a cooling component or a solvent with a vapor pressure of 0.1 mmHg (25°C) or higher, as long as the effects of the present invention are not impaired. The other components (other encapsulated components) can be selected arbitrarily depending on the purpose and are not particularly limited.

[0034] Examples of the other components (other encapsulated components) include hydrophobic solvents with a vapor pressure of less than 0.1 mmHg (25° C.). Examples of the hydrophobic solvent having a vapor pressure of less than 0.1 mmHg (25°C) include isopropyl myristate (vapor pressure 0.0000935 mmHg (25°C)), dodecamethylcyclohexasiloxane (vapor pressure 0.0169 mmHg (25°C)), etc. Among these, isopropyl myristate is preferred from the viewpoint of properly forming the wall material of the microcapsules and properly producing the microcapsules.

[0035] The other component encapsulated in the microcapsules may be one kind or two or more kinds, and when there are two or more kinds, the combination and ratio thereof can be selected arbitrarily.

[0036] In the microcapsules, the total content of the other components (other encapsulated components) relative to 100 parts by mass of the total content of the core material of the microcapsules is preferably 0 to 50 parts by mass, more preferably 0 to 40 parts by mass, and even more preferably 5 to 30 parts by mass. When the total content of the other components (other encapsulated components) is within this range, the wall material of the microcapsules can be formed more normally, and the microcapsules can be produced more normally.

[0037] <Wall materials and wall material components> The microcapsules of this embodiment are configured by encapsulating a core substance within a wall material. The microcapsules can be produced by applying a complex coacervation method, as described below. Examples of the components constituting the wall material of the microcapsules (sometimes abbreviated as "wall material components" in this specification) include cationic polymers, anionic polymers, dispersants, and crosslinking agents, which will be described later. By using a cationic polymer and an anionic polymer as the wall material components of the microcapsules, the wall material of the microcapsules can be made stronger.

[0038] As described above, the wall material preferably contains the cationic polymer, the anionic polymer, the dispersant, and the crosslinking agent.

[0039] [Cationic polymer] The cationic polymer preferably serves as a wall material component of the microcapsule together with the anionic polymer. A cationic polymer is a polymer that has a cationic moiety in its molecule.

[0040] The cationic polymer is not particularly limited as long as it has a cationic moiety in its molecule, but examples thereof include gelatin, chitosan, casein, etc. Among these, gelatin is preferred. That is, the wall material of the microcapsules preferably contains gelatin.

[0041] As the gelatin, conventional gelatin such as that derived from animal bones or skin can be used. The molecular weight of the gelatin may be, for example, 20,000 to 9,000,000.

[0042] Gelatin is an amphoteric polymer that can be either cationic or anionic, and is therefore preferably used after being cationized, for example, by the action of an acid, as will be described later.

[0043] The origin of the gelatin may be one kind or two or more kinds, and when two or more kinds are used, the combination and ratio thereof can be selected arbitrarily.

[0044] In the microcapsules, the content of the cationic polymer is preferably 10 to 50 parts by mass, more preferably 15 to 45 parts by mass, and even more preferably 20 to 40 parts by mass, relative to 100 parts by mass of the total content of the wall material components of the microcapsules. By having the content of the cationic polymer in this range, the wall material of the microcapsules can be made stronger.

[0045] [Anionic polymer] The anionic polymer, together with the cationic polymer, preferably constitutes a wall component of the microcapsules. An anionic polymer is a polymer that has an anionic moiety in its molecule.

[0046] The anionic polymer is not particularly limited as long as it has an anionic moiety in its molecule, and examples thereof include polymers having groups in which acid groups are dissociated (anionized). More specifically, the anionic polymer may be, for example, a group in which a carboxy group (-C(=O)-OH) is dissociated (anionized), that is, a carboxylate anion (-C(=O)-O - ) polymers; sulfo groups (-SO3H) dissociated (anionized) groups (-SO3 - ) and the like. In one molecule of an anionic polymer, some or all of the anionic groups may form a salt together with a cation.

[0047] In an anionic polymer, the cation forming a salt with the anionic group (anionized group) is preferably a metal ion. The metal ion may be either a monovalent metal ion or a metal ion with a valence of two or more (a polyvalent metal ion), but is preferably a monovalent metal ion.

[0048] Examples of the monovalent metal ions include sodium ions (Na + ), potassium ions (K + ), lithium ion (Li +) and other alkali metal ions. Examples of the polyvalent metal ions include calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ) and other alkaline earth metal ions.

[0049] Examples of anionic polymers include gum arabic, alginic acid, sodium alginate, carrageenan (e.g., iota carrageenan, kappa carrageenan, lambda carrageenan), ring-opened ethylene-maleic anhydride copolymers, xanthan gum, and pectin. The ring-opened product of the ethylene-maleic anhydride copolymer means a copolymer in which the acid anhydride moiety in the structural unit derived from maleic anhydride in the ethylene-maleic anhydride copolymer is considered to have been ring-opened by hydrolysis.

[0050] The molecular weight of the anionic polymer is not particularly limited and may be, for example, 20,000 to 50,000,000. The molecular weight of the anionic polymer may vary depending on the type of anionic polymer. For example, the molecular weight of gum arabic may be 200,000 to 2,000,000, the molecular weight of sodium alginate may be 40,000 to 4,000,000, the molecular weight of xanthan gum may be 2,000,000 to 50,000,000, and the molecular weight of pectin may be 50,000 to 360,000.

[0051] In the microcapsules, the content of the anionic polymer is preferably 10 to 210 parts by mass relative to 100 parts by mass of the cationic polymer, and may be, for example, any of 10 to 190 parts by mass, 10 to 170 parts by mass, 10 to 150 parts by mass, and 10 to 130 parts by mass, or any of 60 to 210 parts by mass, 110 to 210 parts by mass, and 160 to 210 parts by mass, or any of 60 to 190 parts by mass and 110 to 170 parts by mass. By having the content of the anionic polymer in this range, the wall material of the microcapsules can be made stronger.

[0052] In the microcapsules, the content of the anionic polymer is preferably 20 to 80 parts by mass, more preferably 30 to 75 parts by mass, and even more preferably 40 to 70 parts by mass, relative to 100 parts by mass of the total content of the wall material components of the microcapsules. By having the content of the anionic polymer in this range, the wall material of the microcapsules can be made stronger.

[0053] [Dispersant] The microcapsules may contain a dispersant.

[0054] By including a dispersant in the microcapsules, aggregation or coalescence of the microcapsules themselves and aggregation or coalescence of the wall material components during the microcapsule formation process can be more effectively prevented, and as a result, the particle size of the microcapsules can be more effectively prevented from becoming excessively large.

[0055] Examples of dispersants include carboxymethyl cellulose and sodium carboxymethyl cellulose.

[0056] In the microcapsules, the content of the dispersant is preferably 0.5 to 20 parts by mass, and may be, for example, 1 to 10 parts by mass or 2 to 5 parts by mass, per 100 parts by mass of the total content of the cationic polymer. When the content of the dispersant is equal to or greater than the lower limit, the particle size of the microcapsules can be further prevented from becoming excessively large. When the content of the crosslinker is equal to or less than the upper limit, excessive use of the dispersant can be further prevented.

[0057] In the microcapsules, the content of the dispersant is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, relative to 100 parts by mass of the total content of the wall material components of the microcapsules. By keeping the content of the dispersant within this range, it is possible to further prevent the particle size of the microcapsules from becoming excessively large.

[0058] [Crosslinking agent] The microcapsules may contain a crosslinking agent.

[0059] The cross-linking agent makes the wall of the microcapsule stronger. The crosslinking agent in the microcapsules is presumed to contribute to binding the wall components together, for example, by being interposed between different sites on one wall component molecule and connecting these sites by hydrogen bonds, covalent bonds, or electrical attraction, or by being interposed between two wall component molecules and connecting these two molecules by hydrogen bonds, covalent bonds, or electrical attraction.

[0060] The crosslinking agent may be a known one and is not particularly limited. Preferred cross-linking agents include, for example, transglutaminase, polyphenols, glutaraldehyde, etc., and among these, transglutaminase is more preferred.

[0061] The polyphenols are not particularly limited as long as they have two or more phenolic hydroxyl groups in one molecule, in other words, they have an aromatic ring such as a benzene ring skeleton or a naphthalene ring skeleton, and have two or more hydroxyl groups (-OH) directly bonded to carbon atoms constituting the ring skeleton of the aromatic ring. Polyphenols are, for example, amino groups (-NH2) in cationic polymers (e.g., gelatin) or their hydrogen ion adducts (-NH3 + ) and is presumed to form hydrogen bonds.

[0062] Examples of the polyphenols include tannic acid, catechin, chlorogenic acid, gallic acid, quinic acid, and caffeic acid.

[0063] The crosslinking agent may be of only one type, or may be of two or more types, and when two or more types are used, the combination and ratio thereof can be selected arbitrarily.

[0064] In the microcapsules, the content of the crosslinking agent is preferably 0.01 to 2 parts by mass, and may be, for example, 0.05 to 1 part by mass or 0.1 to 0.5 parts by mass, relative to 100 parts by mass of the total content of the cationic polymer and the anionic polymer. When the content of the crosslinking agent is equal to or greater than the lower limit, the wall material of the microcapsules becomes stronger. When the content of the crosslinking agent is equal to or less than the upper limit, excessive use of the crosslinking agent is suppressed.

[0065] In the microcapsules, the content of the crosslinking agent is preferably 0.01 to 2 parts by mass, more preferably 0.05 to 1 part by mass, and even more preferably 0.1 to 0.5 parts by mass, relative to 100 parts by mass of the total content of the wall material components of the microcapsules. By having the content of the crosslinking agent in this range, the wall material of the microcapsules becomes stronger.

[0066] Known crosslinking agents also include polyvalent metal salts. The polyvalent metal salts are not particularly limited as long as they contain metal ions with a valence of two or more (polyvalent metal ions) as constituent components. For example, the polyvalent metal salt may be either a polyvalent metal inorganic salt or a polyvalent metal organic salt. The polyvalent metal salt may be either a hydrate or a non-hydrate.

[0067] The crosslinking agent is preferably one or more selected from the group consisting of transglutaminase, polyphenols, and glutaraldehyde, in that the wall material of the microcapsules becomes stronger.

[0068] [Other microcapsule components] The wall material in the microcapsules may contain other components that do not fall into the category of cationic polymers, anionic polymers, dispersants, or crosslinking agents, as long as the effects of the present invention are not impaired. The other components (other constituent components) can be selected arbitrarily depending on the purpose and are not particularly limited.

[0069] Examples of the other components (other constituent components) include additives known in the art. Examples of the additives include pH adjusters such as citric acid, sodium hydroxide, and hydrochloric acid.

[0070] The other components constituting the microcapsules may be of only one type or of two or more types, and when there are two or more types, the combination and ratio thereof can be selected arbitrarily.

[0071] <Characteristics of microcapsules> The average particle size of the microcapsules is not particularly limited and may be, for example, 30 μm or less, 28 μm or less, 26 μm or less, 24 μm or less, or 22 μm or less. For example, microcapsules with a small average particle size are difficult to visually recognize, so their applications are not limited.

[0072] The lower limit of the average particle size of the microcapsules is not particularly limited. For example, the average particle size of the microcapsules may be any of 1 μm or more, 3 μm or more, and 5 μm or more, in terms of ease of production of the microcapsules.

[0073] The average particle size of the microcapsules can be adjusted appropriately within a range set by arbitrarily combining any of the upper and lower limits described above. For example, in one embodiment, the average particle size of the microcapsules may be any of 1 to 30 μm, 1 to 28 μm, 1 to 26 μm, 1 to 24 μm, and 1 to 22 μm or less, or any of 3 to 30 μm, 3 to 28 μm, 3 to 26 μm, 3 to 24 μm, and 3 to 22 μm or less, or any of 5 to 30 μm, 5 to 28 μm, 5 to 26 μm, 5 to 24 μm, and 5 to 22 μm or less.

[0074] In this specification, unless otherwise specified, the term "average particle size" refers to the median diameter of the volume particle size distribution of particles measured using a particle size distribution analyzer.

[0075] In the microcapsules, the safety of the microcapsules to living organisms can be further improved by not using any materials that are highly toxic to living organisms as the raw materials for the wall material. Furthermore, the microcapsules can be easily made biodegradable by selecting appropriate raw materials for the wall material and the core material.

[0076] The microcapsules can be made to have sustained release properties, in which the encapsulated core substance is gradually released to the outside over time, and such microcapsules can maintain the action of the core substance for a long period of time. For example, the microcapsules described above, which are formed by appropriately combining the cooling component, the solvent with a vapor pressure of 0.1 mmHg (25°C) or more, the cationic polymer, the anionic polymer, the dispersant, and the crosslinking agent, are suitable as they have higher sustained release properties.

[0077] <<Microcapsule manufacturing method>> One method for manufacturing microcapsules is to apply the coacervation method. Furthermore, there are two types of coacervation methods: simple coacervation, in which the wall material is made of only one type of polymer, and complex coacervation, in which the wall material is made of two or more types of polymer. In the complex coacervation method, the wall material is made of anionic polymers and cationic polymers. The complex coacervation method is suitable for manufacturing microcapsules with strong wall materials.

[0078] The microcapsules of this embodiment can be produced by applying a complex coacervation method. The microcapsules of this embodiment produced in this manner have stronger walls than microcapsules produced by applying a simple coacervation method.

[0079] When microcapsules are produced by applying the complex coacervation method, typically, in the initial stage, a cationic polymer and a core substance are mixed to prepare an emulsion, and this emulsion is then mixed with an anionic polymer to produce microcapsules.

[0080] For example, the microcapsules according to the present embodiment may be produced by a process comprising: a step of preparing a mixed solution (z) by mixing a cooling component with a solvent having a vapor pressure of 0.1 mmHg (25°C) or more (sometimes referred to as a "first mixing process" in this specification); a step of preparing an emulsion by mixing a cationic polymer with the mixed liquid (z) in the presence of water (sometimes referred to as an "emulsification step" in this specification); a step of preparing a mixed liquid (a) by mixing an anionic polymer, the emulsion, and a dispersant in the presence of water (sometimes referred to as an "emulsion mixing step" in this specification); a step of preparing an acidic mixed solution (b) by mixing the mixed solution (a) with an acid (sometimes referred to as an "acidification step" in this specification); a step of cooling the mixed liquid (b) until its temperature becomes 10°C or less (sometimes referred to as a "cooling step" in this specification); a step of adjusting the pH by mixing the cooled mixed solution (b) with a base (sometimes referred to as a "base mixing step" in this specification); The microcapsules can be produced by a method including a step of preparing an aqueous dispersion of microcapsules by mixing the pH-adjusted mixed solution (b) with a crosslinking agent (sometimes referred to as the "crosslinking agent mixing step" in this specification).

[0081] <<How to use microcapsules>> The microcapsules according to this embodiment can gradually release the encapsulated core substance to the outside over time. Alternatively, when the microcapsules according to this embodiment contain a water-soluble polymer such as gelatin as a wall component, the wall material can be immediately broken down by adding water dropwise, and the encapsulated core substance can be easily released. [Example]

[0082] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the examples shown below.

[0083] [Example 1] <<Microcapsule manufacturing>> At room temperature (under conditions of 23°C), 1-menthol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., equivalent to a cooling component) (30.0 g) was added to and dissolved in decamethylcyclopentasiloxane (manufactured by TCI Corporation, vapor pressure 0.3 mmHg (25°C), equivalent to a solvent) (20.0 g) to obtain a mixed solution (z) (first mixing step).

[0084] An aqueous solution (116.0 g) of gelatin ("Pigskin Gelatin (Type A)" manufactured by Nitta Gelatin Co., Ltd., equivalent to a cationic polymer) with a concentration of 5.2% by mass was heated to 50°C, and the entire amount of the mixed liquid (z) obtained above at room temperature was added to this aqueous solution. An emulsifier (manufactured by Primix Corporation) was used to stir the mixture at a rotation speed of 3000 rpm at room temperature for 5 minutes to produce an emulsion (emulsification step).

[0085] An aqueous solution (120.0 g) of gum arabic (manufactured by Nacalai Tesque, Inc., equivalent to an anionic polymer) with a concentration of 8.3% by mass was heated to 50°C, and the entire amount of the emulsion obtained above was added to this aqueous solution and stirred.

[0086] Next, an aqueous solution (2.0 g) of carboxymethylcellulose sodium (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., equivalent to a dispersant) with a concentration of 10% by mass was heated to 50°C, and the entire amount of this heated aqueous solution was added to the above obtained solution. The mixture was stirred for 2 minutes while maintaining the temperature at 50°C, thereby preparing mixed solution (a) (emulsion mixing step).

[0087] Next, while stirring the mixed solution (a) at 50°C, an aqueous solution of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with a concentration of 50% by mass at room temperature was added dropwise to the mixed solution (a), and the pH of the mixed solution (a) was adjusted to 3.8, thereby preparing an acidic mixed solution (b) (acidification step).

[0088] Next, the resulting mixed liquid (b) was cooled to a temperature of 5°C at a cooling rate of 0.5°C / min while being stirred (cooling step).

[0089] Next, under the condition of 5°C, while stirring the mixed solution (b), an aqueous solution of sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) with a concentration of 20% by mass was added dropwise thereto to adjust the pH of the mixed solution (b) to 6.0 (base mixing step).

[0090] Next, a cross-linking agent (Ajinomoto Co., Inc.'s "Activa TG-S," transglutaminase 1% by mass) (5.0 g) was added, and the mixture was stirred for 2 minutes, followed by stirring at room temperature for 18 hours to prepare an aqueous dispersion of microcapsules.

[0091] As a result of the above, microcapsules were obtained as an aqueous dispersion, with the wall component comprising gelatin (cationic polymer), gum arabic (anionic polymer), and sodium carboxymethylcellulose (dispersant), and further containing transglutaminase (crosslinking agent), and the core material encapsulating l-menthol (cooling component) and decamethylcyclopentasiloxane (solvent).

[0092] <<Evaluation of Microcapsules>> <Evaluation of the degree of microcapsule formation> The appearance of the product in the aqueous dispersion obtained above was observed using a scanning electron microscope (SEM, "JSM-6700F" manufactured by JEOL Ltd.), and the degree of wall formation was confirmed, and the degree of microcapsule formation was evaluated according to the following criteria. [Evaluation criteria] A: The wall material is formed normally and the microcapsules are produced normally. B: Wall material was formed, but microcapsules were not formed neatly. C: The wall material was not formed normally and no microcapsules were produced.

[0093] <Refreshing sensory evaluation> The microcapsule water dispersion prepared above was applied to a 5cm x 5cm nonwoven fabric at a density of 5g / m 2 After coating and drying, the product was placed on the wrist, and then 1 cc of water was dropped onto it. The degree of coolness was evaluated sensorily according to the following criteria. The results are shown in Table 1. [Evaluation criteria] A: After dripping the water, I felt a cooling sensation immediately, and the cooling sensation continued. B: After dripping the water, a cooling sensation was felt immediately, but the cooling sensation was weaker than in "A" above. However, the cooling sensation continued as in "A" above. C: After dripping the water, the cool feeling was not felt immediately. After a few minutes, the cool feeling was felt, but it was weaker than the above "A" and "B".

[0094] <<Production and evaluation of microcapsules>> [Example 2] Microcapsules were produced and evaluated in the same manner as in Example 1, except that l-menthol (30.0 g) was replaced with l-menthol (21.0 g) and 2-isopropyl-N,2,3-trimethylbutyramide (manufactured by TCI, corresponding to a cooling component) (9.0 g). The results are shown in Table 1.

[0095] [Example 3] Microcapsules were produced and evaluated in the same manner as in Example 2, except that decamethylcyclopentasiloxane (14.0 g) and isopropyl myristate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., vapor pressure 0.0000935 mmHg (25°C)) (6.0 g) were used instead of decamethylcyclopentasiloxane (20.0 g). The results are shown in Table 1.

[0096] [Example 4] Microcapsules were produced and evaluated in the same manner as in Example 2, except that decamethylcyclopentasiloxane (10.0 g) and isopropyl myristate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., vapor pressure 0.0000935 mmHg (25°C)) (10.0 g) were used instead of decamethylcyclopentasiloxane (20.0 g). The results are shown in Table 1.

[0097] [Comparative Example 1] Microcapsules were produced and evaluated in the same manner as in Example 2, except that isopropyl myristate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., vapor pressure 0.0000935 mmHg (25°C)) (20.0 g) was used instead of decamethylcyclopentasiloxane (20.0 g). The results are shown in Table 1.

[0098] [Table 1] In Table 1, "-" means that the ingredient in that column is not used.

[0099] As is clear from the above results, in Examples 1 to 4, a refreshing feeling could be felt immediately after the water was dripped. In Examples 1 to 4, the microcapsules contained a cooling component and a solvent with a vapor pressure of 0.3 mmHg (25° C.).

[0100] In contrast to this, in Comparative Example 1, the refreshing feeling could not be felt immediately after the water was dripped. In Comparative Example 1, the microcapsules contained a cooling component and a solvent with a vapor pressure of 0.0000935 mmHg (25° C.). [Industrial Applicability]

[0101] The present invention can provide microcapsules that can provide a sufficient cooling sensation.

Claims

1. A microcapsule encapsulating a cooling component and a solvent having a vapor pressure of 0.1 mmHg or more at 25°C.

2. The microcapsules according to claim 1, wherein the cooling component is one or more selected from the group consisting of 1-menthol, 1-menthol derivatives, and 2-isopropyl-N,2,3-trimethylbutyramide.

3. 3. The microcapsule according to claim 1, wherein the wall material of the microcapsule comprises gelatin.

4. 3. The microcapsule of claim 1, wherein the solvent is a cyclic siloxane.

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