Microcapsules and methods for manufacturing the same

Abstract

To provide a microcapsule having a strong wall material, small average particle diameter and high heat resistance.SOLUTION: There is provided a microcapsule which comprises gelatin, a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, a cross-linking agent and an inorganic compound, wherein the microcapsule encapsulates an oil component and an average particle diameter of the microcapsule is 30 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to microcapsules and methods for producing the same. [Background technology]

[0002] Microcapsules are formed when the wall material encapsulates the target component as a core material. One method for manufacturing microcapsules is the coacervation method. Furthermore, there are two types of coacervation: simple coacervation, which uses only one type of polymer to form the wall material, and composite coacervation, which uses two or more types of polymers to form the wall material. In composite coacervation, the wall material is composed of anionic polymers and cationic polymers. Composite coacervation is suitable for producing microcapsules with a strong wall material.

[0003] When manufacturing microcapsules using the composite coacervation method, the strength of the microcapsules is usually improved by applying a crosslinking agent to the wall material containing the core material, thereby crosslinking the components of the wall material. However, during these steps, the particle size of the final microcapsules tends to increase due to aggregation or coalescence of the microcapsules and the components of the wall material during their formation. Such large-particle microcapsules can have limited applications, for example, because they are easily visible to the naked eye.

[0004] On the other hand, a method is known to improve the properties of microcapsules by incorporating inorganic compounds into the wall material (see Patent Document 1). For example, microcapsules equipped with a wall material containing inorganic compounds are expected to have improved heat resistance. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-174043 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The microcapsules disclosed in Patent Document 1 contain inorganic compounds in their wall material, but these microcapsules are obtained by a simple coacervation method and have a large particle size. Furthermore, microcapsules obtained by a composite coacervation method that have a small particle size and excellent heat resistance are not known to date.

[0007] The present invention aims to provide microcapsules that are strong in their wall material, have a small average particle size, and exhibit high heat resistance. [Means for solving the problem]

[0008] To solve the above problems, the present invention adopts the following configuration. [1] A microcapsule comprising gelatin, a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, a crosslinking agent, and an inorganic compound, wherein the microcapsule contains an oily component, and the average particle size of the microcapsule is 30 μm or less. [2] The microcapsule according to [1], wherein the average particle size of the inorganic compound is 1 μm or less. [3]. The microcapsule according to [1] or [2], wherein the oily component is a fragrance. [4]. The microcapsule according to any one of [1] to [3], wherein the crosslinking agent is transglutaminase.

[0009] [5] A method for producing microcapsules, comprising the steps of: preparing an emulsion (1) by mixing gelatin and an oily component in the presence of water; preparing a mixture (a1) by mixing a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, an inorganic compound and the emulsion (1) in the presence of water; preparing an acidic mixture (b1) by mixing the mixture (a1) and an acid; cooling the mixture (b1) until its temperature is 10°C or lower; and preparing an aqueous dispersion (1) of microcapsules by mixing the cooled mixture (b1) and a crosslinking agent. [6] A method for producing microcapsules, comprising the steps of: preparing an emulsion (2) by mixing gelatin, an inorganic compound, and an oily component in the presence of water; preparing a mixture (a2) by mixing a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, and the emulsion in the presence of water; preparing an acidic mixture (b2) by mixing the mixture (a2) and an acid; cooling the mixture (b2) until its temperature is 10°C or lower; and preparing an aqueous dispersion (2) of microcapsules by mixing the cooled mixture (b2) and a crosslinking agent. [7]. A method for producing microcapsules according to [5] or [6], wherein in the step of producing the mixed solution (a1) or the step of producing the mixed solution (a2), the amount of the inorganic compound is 3 to 13 parts by mass per 100 parts by mass of the total amount of the gelatin, the first anionic polymer, and the second anionic polymer. [Effects of the Invention]

[0010] According to the present invention, microcapsules are provided that have a strong wall material, a small average particle size, and high heat resistance. [Modes for carrying out the invention]

[0011] <<Microcapsules>> The microcapsules according to one embodiment of the present invention are composed of gelatin, a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, a crosslinking agent, and an inorganic compound. The microcapsules encapsulate an oily component, and the average particle diameter of the microcapsules is 30 μm or less.

[0012] The microcapsules of this embodiment can be produced by the complex coacervation method, and their wall material is strong. Also, the average particle diameter of the microcapsules of this embodiment is small. In addition, the microcapsules of this embodiment are composed of an inorganic compound and have high heat resistance. Such microcapsules with high heat resistance are more stable for a longer time than usual even when heated in the coexistence of water, and are suitable as microcapsules used in the coexistence of water.

[0013] The microcapsules of this embodiment are composed of a core substance encapsulated by a wall material. As described later, the microcapsules can be produced by applying the complex coacervation method. The gelatin, the first anionic polymer, and the second anionic polymer are constituent components of the wall material of the microcapsules (which may be abbreviated as "wall material components" in this specification), and constitute the wall material by the complex coacervation method.

[0014] ◎ Wall material, wall material components As described above, the wall material is composed of the gelatin, the first anionic polymer, and the second anionic polymer, and the crosslinking agent contributes to maintaining the strong structure of the wall material.

[0015] <Gelatin> The gelatin, together with the first anionic polymer and the second anionic polymer, serves as a wall material component of the microcapsules. The gelatin constituting the wall material is a cationic polymer having a cationic part in its molecule.

[0016] As for gelatin, ordinary types, such as those derived from animal bones or skin, can be used. The molecular weight of gelatin may be, for example, between 20,000 and 9,000,000.

[0017] Since gelatin is an amphoteric polymer that can be either cationic or anionic, it is used after being cationized by the action of an acid, as will be described later.

[0018] The gelatin constituting the microcapsules may be derived from only one type of gelatin, or from two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0019] <First anionic polymer> The first anionic polymer is a polymer having an anionic portion in its molecule, and together with gelatin, it serves as a component of the microcapsule wall material.

[0020] The first anionic polymer is not particularly limited as long as it is a polymer having anionic groups. Examples of primary anionic polymers include polymers having groups in which an acidic groups have been dissociated (anionized). As a primary anionic polymer, more specifically, for example, a group obtained by dissociating (anionizing) a carboxyl group (-C(=O)-OH), i.e., a carboxylate anion (-C(=O)-OH - ) polymers having a sulfo group (-SO3H) that has been dissociated (anionized) (-SO3 - Examples include polymers having the following properties: In a single molecule of primary anionic polymer, some or all of the anionic groups may form a salt together with a cation.

[0021] In the first 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 valency of 2 or more (polyvalent metal ion), but it is preferably a monovalent metal ion.

[0022] Examples of the monovalent metal ions include sodium ions (Na + ), potassium ions (K + ), lithium ion (Li + Examples include alkali metal ions such as ) Examples of the aforementioned polyvalent metal ions include calcium ions (Ca 2+ ), magnesium ions (Mg 2+ Examples include alkaline earth metal ions such as )

[0023] Examples of primary anionic polymers include gum arabic, alginic acid, sodium alginate, carboxymethylcellulose, sodium carboxymethylcellulose, carrageenan (e.g., ι-carrageenan (iotacarrageenan), κ-carrageenan (kappacarrageenan), λ-carrageenan (lambdacarrageenan)), ring-opened products of ethylene maleic anhydride copolymers, xanthan gum, and pectin. The ring-opened product of the ethylene maleic anhydride copolymer refers to a constituent unit derived from maleic anhydride in the ethylene maleic anhydride copolymer in which the acid anhydride moiety can be considered to have undergone ring-opening by hydrolysis.

[0024] The molecular weight of the first anionic polymer is not particularly limited and may be, for example, 20,000 to 50,000,000. The molecular weight of the first anionic polymer may vary depending on the type of first 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 sodium carboxymethylcellulose may be 20,000 to 400,000, the molecular weight of xanthan gum may be 2,000,000 to 5,000,000, and the molecular weight of pectin may be 50,000 to 360,000.

[0025] In the microcapsules, the content of the first anionic polymer per 100 parts by mass of gelatin is preferably 100 to 300 parts by mass, for example, it may be any of 100 to 270 parts by mass, 100 to 240 parts by mass, 100 to 210 parts by mass, and 100 to 180 parts by mass, or any of 140 to 300 parts by mass, 180 to 300 parts by mass, and 220 to 300 parts by mass, or any of 140 to 270 parts by mass and 180 to 240 parts by mass. By having the content of the first anionic polymer within such a range, the amount of the first anionic polymer or gelatin that does not contribute to the composition of the wall material can be reduced.

[0026] <Second anionic polymer> The second anionic polymer, like the first anionic polymer, is a polymer having an anionic portion in its molecule, and together with gelatin, it serves as a component of the microcapsule wall material.

[0027] The second anionic polymer is a polymer having anionic groups and is of a different type from the first anionic polymer, but is not particularly limited.

[0028] In this embodiment, the fact that the first anionic polymer and the second anionic polymer are of different types means that the polymeric portion having the anionic part of the first anionic polymer and the polymeric portion having the anionic part of the second anionic polymer are different in terms of composition, and it is preferable that one of these polymeric portions has a constituent unit that the other does not have.

[0029] Examples of secondary anionic polymers include those similar to the primary anionic polymers described earlier.

[0030] The molecular weight of the second anionic polymer may be the same as that of the second anionic polymer described earlier.

[0031] In the microcapsules, the content of the secondary anionic polymer per 100 parts by mass of gelatin is preferably 1 to 20 parts by mass, for example, it may be any of 1 to 17 parts by mass, 1 to 14 parts by mass, 1 to 11 parts by mass, and 1 to 8 parts by mass, or any of 4 to 20 parts by mass, 7 to 20 parts by mass, and 10 to 20 parts by mass, or any of 4 to 17 parts by mass and 7 to 14 parts by mass. By having the content of the secondary anionic polymer within such a range, the amount of secondary anionic polymer or gelatin that does not contribute to the composition of the wall material can be reduced.

[0032] The first anionic polymer and the second anionic polymer contained in the microcapsule (in other words, constituting the wall material components) may consist of only two types in total, or three or more types, and the combination and ratio of the first anionic polymer and the second anionic polymer can be arbitrarily selected according to the purpose.

[0033] In this embodiment, for example, if the microcapsule contains only two types of anionic polymers in total, the anionic polymer with a higher content (parts by mass) in the microcapsule is designated as the first anionic polymer, and the anionic polymer with a lower content (parts by mass) is designated as the second anionic polymer.

[0034] On the other hand, if the microcapsule contains a total of three or more anionic polymers, the classification of the anionic polymers differs depending on whether the calculated ratio of the content (parts by mass) of the anionic polymer X1, which has the highest content (parts by mass) in the microcapsule, to the total content (parts by mass) of anionic polymers ([Content of anionic polymer X1 (parts by mass)] / [Total content of anionic polymers (parts by mass)] × 100) is 50% by mass or more, or less than 50% by mass. Here, "total content of anionic polymers (parts by mass)" refers to the total content of all anionic polymers contained in the microcapsule, and is the sum of the contents of each individual anionic polymer.

[0035] If the calculated value is 50% by mass or more, the anionic polymer X1 is designated as the first anionic polymer, and the other anionic polymers are designated as the second anionic polymers. In contrast, if the calculated value is less than 50% by mass, the total amount (parts by mass) of each type of anionic polymer is calculated by summing the anionic polymer content (parts by mass) in descending order of value. The anionic polymer with the smallest amount whose ratio to the total anionic polymer content (parts by mass) ([total anionic polymer content (parts by mass) obtained by summing the anionic polymer content in descending order of value] / [total anionic polymer content (parts by mass)] × 100) is 50% by mass or more is designated as the first anionic polymer. The remaining anionic polymers are designated as the second anionic polymers. However, multiple types of anionic polymers with the same content (parts by mass) in the microcapsules are treated equally. For example, if the mixture contains 40 parts by mass of anionic polymer X1, 30 parts by mass of anionic polymer X2, 20 parts by mass of anionic polymer X3, and 10 parts by mass of anionic polymer X4, then anionic polymers X1 and X2 are designated as first anionic polymers, and anionic polymers X3 and X4 are designated as second anionic polymers. Alternatively, if the mixture contains 35 parts by mass of anionic polymer X1, 25 parts by mass of anionic polymer X2, 25 parts by mass of anionic polymer X3, and 15 parts by mass of anionic polymer X4, then anionic polymers X1, X2, and X3 are designated as first anionic polymers, and anionic polymer X4 is designated as second anionic polymer. In this case, anionic polymers X2 and X3 are treated equally, and one is not designated as the first anionic polymer and the other as the second anionic polymer.

[0036] The microcapsules may, for example, contain only one type each of the first anionic polymer and the second anionic polymer, or contain only one type of the first anionic polymer and two or more types of the second anionic polymer, or contain two or more types of the first anionic polymer and only one type of the second anionic polymer, or contain two or more types each of the first anionic polymer and the second anionic polymer.

[0037] In the microcapsule manufacturing method described later, the timing of the use of the first and second anionic polymers is crucial. This point, along with the microcapsule manufacturing method, will be explained in detail later.

[0038] In the microcapsules, the content of the second anionic polymer per 100 parts by mass of the first anionic polymer is preferably 0.5 to 10 parts by mass, for example, 0.5 to 8 parts by mass, 0.5 to 6 parts by mass, and 0.5 to 4 parts by mass, or 1 to 10 parts by mass, 3 to 10 parts by mass, and 5 to 10 parts by mass, or 1 to 8 parts by mass and 3 to 6 parts by mass. When the content is above the lower limit, the yield of the microcapsules is further improved. When the content is below the upper limit, the wall material of the microcapsules becomes stronger.

[0039] In the microcapsules, the total content of the first anionic polymer and the second anionic polymer per 100 parts by mass of gelatin is preferably 30 to 300 parts by mass, for example, 30 to 270 parts by mass, 30 to 240 parts by mass, 30 to 210 parts by mass, and 30 to 180 parts by mass, or 70 to 300 parts by mass, 110 to 300 parts by mass, and 150 to 300 parts by mass, or 70 to 270 parts by mass, 110 to 240 parts by mass, 150 to 210 parts by mass, and 150 to 180 parts by mass. When the total content is above the lower limit, the yield of the microcapsules is further improved. When the total content is below the upper limit, the wall material of the microcapsules becomes stronger.

[0040] The aforementioned microcapsules contain at least two types of anionic polymers, a first anionic polymer and a second anionic polymer, as wall material components, resulting in a small average particle size and a strong wall material for the microcapsules. For example, if a microcapsule contains only one type of anionic polymer as a wall material component, aggregation or coalescence of the microcapsules themselves or aggregation or coalescence of the wall material components during the microcapsule formation process may occur. In such cases, the microcapsules may not form properly, or even if they do form, the particle size may become significantly larger.

[0041] <Crosslinking agent> The aforementioned crosslinking agent is presumed to contribute to binding the wall material components together within the microcapsules. More specifically, the crosslinking agent is presumed to interpose between different parts of a single wall material component molecule, linking these parts together by hydrogen bonds or electrical attraction, or to interpose between two wall material component molecules, linking these two molecules together by hydrogen bonds or electrical attraction.

[0042] The crosslinking agent may be either an inorganic compound or an organic compound, but it is preferably an organic compound. Examples of organic crosslinking agents include polyphenols such as tannic acid, catechin, chlorogenic acid, gallic acid, quinic acid, and caffeic acid; and enzymes such as transglutaminase. The aforementioned polyphenols are components that 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 the carbon atoms constituting the ring skeleton of the aromatic ring. While formaldehyde, glutaraldehyde, and other similar substances can be used as crosslinking agents, these are highly toxic and therefore undesirable. In contrast, the aforementioned polyphenols and enzymes are both highly safe for living organisms.

[0043] The crosslinking agent constituting the microcapsule may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0044] Among the crosslinking agents, transglutaminase is particularly preferred because it is highly safe for living organisms and also highly effective in improving the heat resistance of microcapsules.

[0045] In the microcapsules, the crosslinking agent content is preferably 10 to 80 parts by mass per 100 parts by mass of the total content of gelatin, the first anionic polymer, and the second anionic polymer. For example, it may be 10 to 60 parts by mass, 10 to 40 parts by mass, or 10 to 20 parts by mass, or 20 to 80 parts by mass, 40 to 80 parts by mass, or 60 to 80 parts by mass, or 20 to 60 parts by mass. When the crosslinking agent content is above the lower limit, the wall material of the microcapsule becomes stronger. When the crosslinking agent content is below the upper limit, excessive use of the crosslinking agent is suppressed.

[0046] <Inorganic compounds> The inorganic compound is a component that does not fall under the category of the crosslinking agent and improves the heat resistance of the microcapsules. Furthermore, depending on the type of inorganic compound, it may be possible to impart properties other than heat resistance derived from that inorganic compound to the microcapsules. In this specification, unless otherwise specified, "inorganic compound" refers to an inorganic component that does not fall under the category of a crosslinking agent and improves the heat resistance of microcapsules. The microcapsules contain inorganic compounds, and it is presumed that these inorganic compounds interact with the wall material and are incorporated into it.

[0047] Examples of the inorganic compound include metal salts, metal oxides, and metal hydroxides. Examples of the aforementioned metal salts include talc (also known as hydrated magnesium silicate, Mg3Si4O 10 Examples include silicates such as (OH)2; carbonates (metal carbonates) such as calcium carbonate (CaCO3); and sulfates (metal sulfates) such as barium sulfate (BaSO4). Examples of the aforementioned metal oxides include aluminum oxide (also known as alumina, Al2O3); titanium oxide (TiO2); zirconium oxide (ZrO2); iron(II) oxide (also known as ferrous oxide, FeO); iron(III) oxide (also known as triiron tetroxide, Fe3O4); iron(III) oxide (also known as diiron trioxide, Fe2O3); and other iron oxides. Examples of the aforementioned metal hydroxides include aluminum hydroxide (Al(OH)3) and magnesium hydroxide (Mg(OH)2).

[0048] The average particle size of the inorganic compound is not particularly limited, but is preferably 1 μm or less, and may be, for example, 0.8 μm or less. Having the average particle size of the inorganic compound within this range increases the heat resistance of the microcapsules and reduces the average particle size of the microcapsules. The lower limit of the average particle diameter of the inorganic compound is not particularly limited. For example, inorganic compounds with an average particle diameter of 0.1 μm or more are more readily available. In one embodiment, the average particle size of the inorganic compound may be, for example, 0.1 to 1 μm and 0.1 to 0.8 μm. However, this is just one example of the average particle size of the inorganic compound.

[0049] In this specification, "average particle size" refers to the median diameter of the volume particle size distribution, measured using a particle size analyzer, for particles, not limited to inorganic compounds, unless otherwise specified.

[0050] The inorganic compound constituting the microcapsule may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0051] In the microcapsule manufacturing method described later, the timing of the use of inorganic compounds is crucial. This point, along with the microcapsule manufacturing method, will be explained in detail later.

[0052] In the microcapsules, the amount of the inorganic compound is, for example, 2 to 17 parts by mass, but preferably 3 to 13 parts by mass, and may be any of 4 to 9 parts by mass, 3 to 6 parts by mass, or 6 to 13 parts by mass, based on 100 parts by mass of the total amount of gelatin, the first anionic polymer, and the second anionic polymer.

[0053] <Cationic polymers other than gelatin> The wall material in the microcapsules may be composed of a cationic polymer other than gelatin (which may be referred to as "other cationic polymer" in this specification) as long as the effects of the present invention are not impaired.

[0054] The other cationic polymer is not particularly limited. Examples of the other cationic polymer include chitosan, casein, polyethyleneimine, cation-modified polyvinyl alcohol, and the like.

[0055] The other cationic polymer constituting the microcapsules may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected.

[0056] In the microcapsules, the content of the other cationic polymer is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 1 part by mass or less, and particularly preferably 0 part by mass (that is, the microcapsules do not contain the other cationic polymer) with respect to 100 parts by mass of the gelatin content. When the content of the other cationic polymer is below the above upper limit value, the average particle diameter of the microcapsules becomes smaller, the wall material of the microcapsules becomes stronger, and the stability of the microcapsules is further improved.

[0057] ◎ Oil component The oil component is the core substance in the microcapsules of the present embodiment. In the present embodiment, the "oil component" means "a component having an SP value (solubility parameter) of 7.0 to 11.0 (cal / cm 3 ) 1 / 2 ".

[0058] The oil component is not particularly limited and can be arbitrarily selected according to the purpose. The oil component is preferably in an oily state at room temperature. In this specification, "room temperature" means a temperature that is neither cooled nor heated, i.e., a normal temperature, such as 15-25°C.

[0059] Examples of the oily components include animal oils, vegetable oils, mineral oils, and the like. Examples of the aforementioned vegetable oils include peppermint essential oil, lavender essential oil, palm oil, palm kernel oil, soybean oil, rapeseed oil, sunflower oil, cottonseed oil, coconut oil, corn oil, sesame oil, castor oil, linseed oil, peanut oil, and olive oil. Lavender essential oil, for example, mainly consists of linalyl acetate and linalool, and also contains trace components such as cis-β-ocimene, trns-β-ocimene, terpinen-4-ol, lavandulyl acetate, 3-octanone, and 3-octanyl acetate.

[0060] Examples of oily components, from a functional standpoint, include fragrances, insecticides, insect repellents, cosmetic materials, deodorants, pharmaceuticals, disinfectants, fabric softeners for detergents, and other chemical reactants. A chemical reactant is a component that, by reacting with a specific chemical substance, inhibits the action of that chemical substance, and does not fall under any of the categories of fragrances, insecticides, insect repellents, cosmetic materials, deodorants, pharmaceuticals, disinfectants, or fabric softeners.

[0061] The oily components constituting the microcapsules (in other words, those encapsulated in the wall material) may consist of only one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0062] Among the aforementioned oily components, a particularly preferred example is a fragrance.

[0063] In the aforementioned microcapsules, the content of the oily component is preferably 400 to 1200 parts by mass per 100 parts by mass of gelatin, for example, it may be 400 to 1000 parts by mass and 400 to 800 parts by mass, or 600 to 1200 parts by mass and 800 to 1200 parts by mass, or 600 to 1000 parts by mass. Microcapsules in which the content of the oily component (core material) is in such a range are of better quality and can be manufactured more easily.

[0064] In the aforementioned microcapsules, since gelatin, the first anionic polymer, and the second anionic polymer have high biocompatibility, components with high biocompatibility are selected as crosslinking agents and inorganic compounds, and components suitable for use in living organisms are selected as oily components, making the microcapsules suitable for use in living organisms.

[0065] Because of its high heat resistance, the aforementioned microcapsules are suitable for use in water, for example.

[0066] The average particle size of the microcapsules is 30 μm or less, preferably 28 μm or less, and may be, for example, 27 μm or less, 26 μm or less, or 25 μm or less. Microcapsules with such small average particle sizes do not exhibit the problems of larger average particle sizes, such as being easily visible to the naked eye and difficult to remove by washing, thus not limiting their applications.

[0067] The lower limit of the average particle diameter of the microcapsules is not particularly limited. For example, microcapsules with an average particle diameter of preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more, can be manufactured more easily.

[0068] The average particle size of the microcapsules can be appropriately adjusted within a range set by arbitrarily combining any of the lower and upper limits described above. For example, in one embodiment, the average particle size of the microcapsules may be any of 1 to 30 μm, 2 to 28 μm, 3 to 27 μm, 3 to 26 μm, or 3 to 25 μm or less. However, these are just examples of average particle sizes of microcapsules.

[0069] The aforementioned microcapsules contain gelatin, a first anionic polymer, a second anionic polymer, and further contain a crosslinking agent and an inorganic compound. Because they have excellent heat resistance, they can be made to have a sustained-release property that gradually releases the encapsulated oily component to the outside over time. Such microcapsules can sustain the action of the oily component as the core material over a long period of time.

[0070] The aforementioned microcapsules can be manufactured by applying a composite coacervation method, as described below. The microcapsules manufactured in this manner according to this embodiment have stronger wall materials than microcapsules manufactured by applying a simple coacervation method.

[0071] <<Method for manufacturing microcapsules>> ◎Manufacturing method (1) A method for producing microcapsules according to one embodiment of the present invention comprises the steps of preparing an emulsion (1) by mixing gelatin and an oily component in the presence of water (this may be referred to as the "emulsification step (1)" in this specification), A step of preparing a mixture (a1) by mixing a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, an inorganic compound, and the emulsion (1) in the presence of water (this may be referred to as the "emulsion mixing step (1)" in this specification), The process involves mixing the aforementioned mixture (a1) with an acid to produce an acidic mixture (b1) (this may be referred to as the "acidification step (1)" in this specification), The process of cooling the aforementioned mixture (b1) until its temperature is 10°C or lower (this may be referred to as "cooling step (1)" in this specification), The method comprises a step of producing an aqueous dispersion of microcapsules (1) by mixing the cooled mixture (b1) with a crosslinking agent (this may be referred to as the "crosslinking agent mixing step (1)" in this specification) (this method of production may be referred to as the "production method (1)" in this specification).

[0072] Manufacturing method (1) is a method for manufacturing microcapsules using a composite coacervation method, and by this method, the microcapsules of the present invention described above can be successfully manufactured.

[0073] <Emulsification process (1)> In the emulsification step (1) described above, an emulsion (1) is prepared by mixing gelatin and an oily component in the presence of water. The emulsified liquid (1) contains gelatin, water, and an oily component.

[0074] The gelatin and oily components used in the emulsification step (1) are as previously described, and a detailed explanation is omitted here.

[0075] The gelatin and oily components used in the emulsification step (1) may be one type each, or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0076] In the emulsification step (1), for example, gelatin, water, and an oily component may be blended, or an aqueous gelatin solution and an oily component may be blended. When an aqueous gelatin solution is blended, additional water may be added in addition to the water in the aqueous gelatin solution, or it may not be added.

[0077] In the emulsification step (1), the order in which gelatin, water, and oily components are added is not particularly limited, nor is the order in which the gelatin aqueous solution, oily components, and additionally, water as needed, are added.

[0078] In the emulsification step (1), it is preferable to blend a gelatin aqueous solution, an oily component, and water separately as needed. By doing so, an emulsified solution (1) with higher uniformity can be produced.

[0079] The gelatin concentration of the gelatin aqueous solution used in the emulsification step (1) is preferably 2 to 20% by mass, and more preferably 3 to 10% by mass.

[0080] In this embodiment, "concentration of gelatin in the gelatin aqueous solution" means "the ratio of the gelatin content (parts by mass) to the total mass (parts by mass) of the gelatin aqueous solution." Although gelatin is used as an example here, the same applies to the concentrations of aqueous solutions or dispersions of other components.

[0081] Both the water used in the emulsification step (1) and the gelatin aqueous solution may be heated. By heating the water or the gelatin aqueous solution, an emulsified solution (1) with higher uniformity can be produced. The heating temperature of the water and gelatin aqueous solution is preferably 40 to 75°C, and more preferably 40 to 60°C. A heating temperature above the lower limit yields a more pronounced heating effect. A heating temperature below the upper limit further enhances the suppression of adverse effects caused by heating, such as deterioration of gelatin or oily components.

[0082] When the gelatin aqueous solution is combined with an oily component, the oily component may be added to the gelatin aqueous solution, or the gelatin aqueous solution may be added to the oily component. When the oily component is added to the gelatin aqueous solution, the oily component may be added to the gelatin aqueous solution all at once, or added in stages or dropwise. When the gelatin aqueous solution is added to the oily component, the gelatin aqueous solution may be added to the oily component all at once, or added dropwise.

[0083] In the emulsification step (1), the amount of water used is preferably 10 to 30 times the amount of gelatin used, and more preferably 15 to 25 times. When the amount of water used is above the lower limit, the effects of using water are enhanced, such as being able to produce an emulsified liquid (1) with higher uniformity. When the amount of water used is below the upper limit, excessive use of water is suppressed. Here, the amount of water used refers to the amount of water when gelatin, water, and an oily component are combined; the amount of water in the gelatin aqueous solution when a gelatin aqueous solution and an oily component are combined without adding water separately; and the total amount of water in the gelatin aqueous solution and the separately added water when a gelatin aqueous solution, an oily component, and water are combined.

[0084] In the emulsification step (1), the amount of oily component used is preferably 4 to 12 times the amount of gelatin used, for example, it may be 4 to 10 times and 4 to 8 times, or 6 to 12 times and 8 to 12 times, or 6 to 10 times. By using the aforementioned amount of oily component within this range, microcapsules of better quality can be manufactured more easily.

[0085] In the emulsification step (1), other components that do not fall under any of the following categories (referred to as "other components (11)" in this specification) may be mixed, provided that the effects of the present invention are not impaired.

[0086] The aforementioned other components (11) are not particularly limited and can be arbitrarily selected depending on the purpose. The other components (11) used in the emulsification step (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0087] In the emulsification step (1), the amount of the other component (11) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (11). Typically, in the emulsification step (1), the ratio of the amount of other components (11) used to the total amount of gelatin, water, and oily components used ([amount of other components (11)] / ([amount of gelatin]+[amount of water]+[amount of oily components])×100) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less. When the ratio is within this range, microcapsules with a smaller average particle size and higher heat resistance can be obtained. Here, water usage is as explained earlier.

[0088] In the emulsification step (1), the mixing of gelatin, oily components, and other components (11) as needed, in the presence of water is preferably carried out under temperature conditions of 15 to 75°C, and more preferably under temperature conditions of 18 to 60°C.

[0089] The method for mixing gelatin, an oily component, and other components (11) as needed in the presence of water is not particularly limited, and one example is to mix these components by rotating a stirring means such as a stirring bar or a stirring blade. The stirring speed of the stirring means may be, for example, 1000 to 7000 rpm and 2000 to 4000 rpm, but is not limited to these. For example, such a stirring speed is particularly suitable when the amount of gelatin used is 5 to 15 g. However, the amount of gelatin used is not limited to this. Furthermore, it is preferable to apply such a stirring speed in this process at least after all the gelatin, oily components, and other components (11) as needed have been blended in the presence of water.

[0090] In the emulsification step (1), when adding the remaining components to any of the components to be added, namely gelatin or an aqueous gelatin solution, an oily component, water as needed, and other components (11) as needed, the remaining components may be added while stirring any of the components to be added, or the remaining components may be added without stirring any of the components to be added, and the mixture may be stirred after all the components have been combined.

[0091] In the emulsification step (1), after blending all the components (gelatin or gelatin aqueous solution, oily component, water as needed, and other components (11) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0092] In the emulsification step (1), it is preferable to prepare the emulsion (1) by adding an oily component alone to a heated gelatin aqueous solution, or the emulsion (1) may be prepared by adding an oily component at room temperature alone to a heated gelatin aqueous solution.

[0093] <Emulsion mixing process (1)> In the emulsifier mixing step (1), a mixture (a1) is prepared by mixing a first anionic polymer, a second anionic polymer, an inorganic compound, and the emulsifier (1) in the presence of water. The aforementioned mixture (a1) contains a first anionic polymer, a second anionic polymer, an inorganic compound, gelatin, water, and an oily component.

[0094] In the emulsion mixing step (1), by using a first anionic polymer, a second anionic polymer, and an inorganic compound in combination, aggregation or coalescence of the wall material components during the microcapsule formation process is suppressed in subsequent steps.

[0095] The primary anionic polymer, secondary anionic polymer, and inorganic compound used in the emulsion mixing step (1) are as previously described, and a detailed explanation is omitted here.

[0096] The primary anionic polymer, secondary anionic polymer, and inorganic compound used in the emulsion mixing step (1) may each be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected. The classification method for first-anionic polymers and second-anionic polymers is as explained above.

[0097] In the emulsion mixing step (1), for example, a first anionic polymer, a second anionic polymer, an inorganic compound, water, and emulsion (1) may be blended; or an aqueous solution of the first anionic polymer, a second anionic polymer, an inorganic compound, and emulsion (1) may be blended; or a first anionic polymer, an aqueous solution of the second anionic polymer, an inorganic compound, and emulsion (1) may be blended; or an aqueous solution of the first anionic polymer, an aqueous solution of the second anionic polymer, an inorganic compound, and emulsion (1) may be blended. Furthermore, in the emulsion mixing step (1), a dispersion (11) obtained by mixing an inorganic compound with an aqueous solution of a first anionic polymer, or a dispersion (12) obtained by mixing an inorganic compound with an aqueous solution of a second anionic polymer may be used. That is, in the emulsion mixing step (1), the dispersion (11), the second anionic polymer or an aqueous solution thereof, the emulsion (1), and an inorganic compound as needed, and water as needed may be blended together, or the first anionic polymer or an aqueous solution thereof, the dispersion (12), the emulsion (1), an inorganic compound as needed, and water as needed may be blended together, or the dispersion (11), the dispersion (12), the emulsion (1), an inorganic compound as needed, and water as needed may be blended together. When a first anionic polymer aqueous solution, a second anionic polymer aqueous solution, dispersion (11), or dispersion (12) is formulated, water may or may not be added separately in addition to the water in the first anionic polymer aqueous solution, the second anionic polymer aqueous solution, dispersion (11), or dispersion (12).

[0098] In the emulsion mixing step (1), the order in which the first anionic polymer, aqueous solution or dispersion of the first anionic polymer (11), the second anionic polymer, aqueous solution or dispersion of the second anionic polymer (12), the emulsion (1), and optionally an inorganic compound and optionally water are mixed is not particularly limited.

[0099] In the emulsifier mixing step (1), it is preferable to blend the first anionic polymer aqueous solution or dispersion (11), the second anionic polymer aqueous solution or dispersion (12), the emulsifier (1), and, separately as needed, an inorganic compound and, separately as needed, water. By doing so, a mixture (a1) with higher uniformity can be produced.

[0100] The concentration of the first anionic polymer in the aqueous solution or dispersion (11) of the first anionic polymer used in the emulsification mixing step (1) is preferably 3 to 20% by mass, and more preferably 5 to 12% by mass.

[0101] The concentration of the second anionic polymer in the aqueous solution or dispersion (12) of the second anionic polymer used in the emulsification mixing step (1) is preferably 3 to 20% by mass, and more preferably 5 to 12% by mass.

[0102] The concentration of the inorganic compound in the dispersion (11) used in the emulsifier mixing step (1) is preferably 0.1 to 3% by mass, and more preferably 0.3 to 1.2% by mass.

[0103] The concentration of the inorganic compound in the dispersion (12) used in the emulsifier mixing step (1) is preferably 0.1 to 3% by mass, and more preferably 0.3 to 1.2% by mass.

[0104] In the emulsified liquid mixing step (1) (step for preparing the mixed liquid (a1)), the amount of inorganic compound (sometimes referred to as the "converted amount" in this specification) per 100 parts by mass of the total amount of gelatin, the first anionic polymer, and the second anionic polymer may be 2 to 17 parts by mass, but is preferably 3 to 13 parts by mass, and may be 4 to 9 parts by mass, 3 to 6 parts by mass, or 6 to 13 parts by mass. The heat resistance of the microcapsules is improved when the amount of inorganic compound (converted amount) is above the lower limit. The microcapsule formation is improved when the amount of inorganic compound (converted amount) is below the upper limit.

[0105] The water used in the emulsifier mixing step (1), the first anionic polymer aqueous solution or dispersion (11), and the second anionic polymer aqueous solution or dispersion (12) may all be heated. By heating the water, the first anionic polymer aqueous solution, the dispersion (11), the second anionic polymer aqueous solution, or the dispersion (12), a mixture (a1) with higher uniformity can be produced. The heating temperature of the water, the first anionic polymer aqueous solution or dispersion (11), and the second anionic polymer aqueous solution or dispersion (12) is preferably 40 to 75°C, and more preferably 40 to 60°C. When the heating temperature is above the lower limit, the effect of heating is more pronounced. When the heating temperature is below the upper limit, the effect of suppressing adverse effects caused by heating, such as deterioration of the first anionic polymer aqueous solution, dispersion (11), the second anionic polymer aqueous solution, dispersion (12), gelatin, or oily components, is further enhanced.

[0106] When a first anionic polymer aqueous solution, dispersion (11), second anionic polymer aqueous solution, or dispersion (12) is added, the substance to be added may be added to these aqueous solutions or dispersions, or these aqueous solutions or dispersions may be added to the substance to be added. When a first anionic polymer aqueous solution, dispersion (11), second anionic polymer aqueous solution, or dispersion (12) is added, the substance to be added may be added to these aqueous solutions or dispersions all at once, or added in stages or dropwise. When a first anionic polymer aqueous solution, dispersion (11), second anionic polymer aqueous solution, or dispersion (12) is added to the substance to be added, these aqueous solutions or dispersions may be added to the substance all at once, or added dropwise.

[0107] In the emulsifier mixing step (1), the amount of water used is preferably 10 to 30 times the total amount of the first anionic polymer, the second anionic polymer, and the inorganic compound, and more preferably 15 to 25 times the total amount. When the amount of water used is above the lower limit, the effects of using water are enhanced, such as being able to produce a more uniform mixture (a1). When the amount of water used is below the upper limit, excessive use of water is suppressed.

[0108] Here, the amount of water used refers to the amount of water used when mixing the first anionic polymer, the second anionic polymer, water, and emulsion (1). Furthermore, if a first anionic polymer aqueous solution or dispersion (11), a second anionic polymer, and an emulsion (1) are combined and no additional water is added, the amount of water is the amount of water in the first anionic polymer aqueous solution or dispersion (11). Furthermore, when a first anionic polymer aqueous solution or dispersion (11), a second anionic polymer, an emulsion (1), and water are combined, the total amount of water is the sum of the water in the first anionic polymer aqueous solution or dispersion (11) and the water added separately. Furthermore, if a mixture of a first anionic polymer, a second anionic polymer aqueous solution or dispersion (12), and an emulsion (1) is used, and no additional water is added, the amount of water is the amount of water in the second anionic polymer aqueous solution or dispersion (12). Furthermore, when a first anionic polymer, a second anionic polymer aqueous solution or dispersion (12), an emulsifier (1), and water are combined, the total amount of water is the sum of the water in the second anionic polymer aqueous solution or dispersion (12) and the water added separately. Furthermore, if a first anionic polymer aqueous solution or dispersion (11), a second anionic polymer aqueous solution or dispersion (12), and an emulsion (1) are combined and no additional water is added, the amount of water is the sum of the water in the first anionic polymer aqueous solution or dispersion (11) and the water in the second anionic polymer aqueous solution or dispersion (12). Furthermore, when a first anionic polymer aqueous solution or dispersion (11), a second anionic polymer aqueous solution or dispersion (12), an emulsifier (1), and water are combined, the total amount of water is the sum of the water in the first anionic polymer aqueous solution or dispersion (11), the water in the second anionic polymer aqueous solution or dispersion (11), and the water added separately.

[0109] In the emulsifier mixing step (1), the amount of the first anionic polymer used is preferably 1 to 3 times the amount of gelatin in the emulsifier (1). For example, it may be 1 to 2.7 times, 1 to 2.4 times, 1 to 2.1 times, and 1 to 1.8 times, or 1.4 to 3 times, 1.8 to 3 times, and 2.2 to 3 times, or 1.4 to 2.7 times, and 1.8 to 2.4 times. By using the first anionic polymer within this range, the amount of the first anionic polymer or gelatin that does not contribute to the composition of the wall material can be reduced.

[0110] In the emulsion mixing step (1), the amount of secondary anionic polymer used is preferably 0.01 to 0.2 times the amount of gelatin in the emulsion (1). For example, it may be 0.01 to 0.17 times, 0.01 to 0.14 times, 0.01 to 0.11 times, and 0.01 to 0.08 times, or 0.04 to 0.2 times, 0.07 to 0.2 times, and 0.1 to 0.2 times, or 0.04 to 0.17 times and 0.07 to 0.14 times. By using secondary anionic polymer within this range, the amount of secondary anionic polymer or gelatin that does not contribute to the composition of the wall material can be reduced.

[0111] In the emulsified liquid mixing step (1), other components (which may be referred to as "other components (12)" in this specification) that do not fall under any of the following categories: gelatin, first anionic polymer, second anionic polymer, inorganic compound, water, and oily component, may be mixed, provided that the effects of the present invention are not impaired.

[0112] The aforementioned other components (12) are not particularly limited and can be arbitrarily selected depending on the purpose. The other components (12) used in the emulsifier mixing step (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0113] In the emulsifier mixing step (1), the amount of the other component (12) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (12). Typically, in the emulsion mixing step (1), the ratio of the amount of other components (12) used to the total amount of the first anionic polymer, the second anionic polymer, the inorganic compound, water, and emulsion (1) used ([amount of other components (12)] / ([amount of first anionic polymer]+[amount of second anionic polymer]+[amount of inorganic compound]+[amount of water]+[amount of emulsion (1)])×100) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less. When the ratio is within this range, microcapsules with a smaller average particle size and higher heat resistance can be obtained. Here, water usage is as explained earlier.

[0114] In the emulsion mixing step (1), the mixing of the first anionic polymer, the second anionic polymer, the inorganic compound, the emulsion (1), and optionally other components (12) in the presence of water is preferably carried out under temperature conditions of 20 to 75°C, and more preferably under temperature conditions of 20 to 60°C.

[0115] The method for mixing the first anionic polymer, the second anionic polymer, the inorganic compound, the emulsion (1), and optionally other components (12) in the presence of water is not particularly limited and may be the same as, or different from, the method for mixing gelatin, an oily component, and optionally other components (11) in the presence of water in the emulsification step (1) described above.

[0116] In the emulsifier mixing step (1), when adding the remaining components to any of the following additives: the first anionic polymer, the first anionic polymer aqueous solution or dispersion (11), the second anionic polymer, the second anionic polymer aqueous solution or dispersion (12), the emulsifier (1), and optionally an inorganic compound, optionally water, and optionally other components (12), the remaining components may be added while stirring the additives, or the remaining components may be added without stirring the additives, and the mixture may be stirred after all components have been combined.

[0117] In the emulsifier mixing step (1), after mixing all the components (first anionic polymer, first anionic polymer aqueous solution or dispersion (11), second anionic polymer, second anionic polymer aqueous solution or dispersion (12), emulsifier (1), inorganic compound as needed, water as needed, and other components (12) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0118] In the emulsifier mixing step (1), it is preferable to prepare a mixture (a1) by adding the emulsifier (1) alone to a heated first anionic polymer aqueous solution or dispersion (11), and then adding a second anionic polymer aqueous solution or dispersion (12) at room temperature to the resulting mixture. Alternatively, a mixture (a) may be prepared by adding the emulsifier (1) at 25°C or higher alone to a heated first anionic polymer aqueous solution or dispersion (11), and then adding a second anionic polymer aqueous solution or dispersion (12) at room temperature to the resulting mixture.

[0119] <Acidification step (1)> In the acidification step (1), an acidic mixture (b1) is prepared by mixing the mixture (a1) with an acid. The gelatin in the mixture (a1) does not have cationic groups and therefore cannot be considered a cationic polymer, or even if it has cationic groups, the number of such groups is small and it does not have sufficient properties as a cationic polymer. In contrast, the gelatin in the mixture (b1) has a sufficiently large number of cationic groups due to the action of the acid, and is in a state where it fully possesses the properties of a cationic polymer, and is clearly a cationic polymer. In other words, the mixture (b1) contains gelatin (cationic polymer), a first anionic polymer, a second anionic polymer, an inorganic compound, water, and an oily component.

[0120] The acid used in the acidification step (1) is not particularly limited and may be, for example, an inorganic acid or an organic acid. Examples of the inorganic acids include hydrochloric acid (HCl), sulfuric acid (H2SO4), nitric acid (HNO3), and phosphoric acid (H3PO4). Examples of the aforementioned organic acids include citric acid (HOOCCH2C(COOH)(OH)CH2COOH) and acetic acid (CH3COOH).

[0121] The acid used in the acidification step (1) may be one type or two or more types, and if two or more types are used, their combination and ratio can be arbitrarily selected.

[0122] In the acidification step (1), the acid may be added alone or as an aqueous solution. Using an aqueous acid solution makes it easier to prepare a pH-adjusted mixture (b1).

[0123] The concentration of the acid in the acid aqueous solution used in the acidification step (1) can be adjusted as appropriate depending on the type of acid, but it is preferably 10 to 70% by mass, and more preferably 30 to 60% by mass.

[0124] When the aforementioned acidic aqueous solution is combined with a mixed solution (a1), it is preferable to add the acidic aqueous solution to the mixed solution (a1), and the acidic aqueous solution may be added to the mixed solution (a1) all at once or dropwise. If the acid is not added as an aqueous solution, it is preferable to add the acid to the mixture (a1). The acid may be added to the mixture (a1) all at once, or it may be added dropwise or in installments.

[0125] In the acidification step (1), other components (which may be referred to as "other components (13)" in this specification) that do not fall under any of the following categories: gelatin, first anionic polymer, second anionic polymer, inorganic compound, oily component, and acid, may be mixed, as long as the effects of the present invention are not impaired.

[0126] The aforementioned other component (13) is not particularly limited and can be arbitrarily selected depending on the purpose, and may be, for example, water. That is, in the acidification step (1), water may be added separately as the other component (13), regardless of whether the acid is added alone or as an aqueous solution. In this specification, water as the other component (13) may be referred to as "water (13)".

[0127] When using water (13), for example, an acidic mixture (b01) can be prepared by mixing the mixture (a1) with an acid or an acidic aqueous solution, and then an acidic mixture (b1) can be prepared by mixing the acidic mixture (b01) with water (13). Furthermore, when using water (13), for example, the mixture (a1) can be diluted by mixing it with water (13), and then an acidic mixture (b1) can be prepared by mixing this diluted mixture (a1) with an acid or an acidic aqueous solution.

[0128] The other components (13) used in the acidification step (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0129] In the acidification step (1), the amount of the other component (13) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (13). For example, if the other component (13) is a component other than water, in the acidification step (1), the ratio of the amount of the other component (13) used to the total amount of the mixed solution (a1) and the acid used ([amount of other component (13) used] / ([amount of mixed solution (a1) used] + [amount of acid used]) × 100) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less. By keeping the ratio below the upper limit, microcapsules with a smaller average particle size and higher heat resistance can be obtained. Here, the amount of acid used refers to the amount of acid if it is not added as an aqueous solution, and to the amount of acid in the aqueous solution if it is added as an aqueous solution.

[0130] On the other hand, if the other component (13) is water, in the acidification step (1), the ratio of the amount of water (13) used to the total amount of the mixture (a1) and the acid or acidic aqueous solution used ([amount of water (13) used] / ([amount of mixture (a1) used]+[amount of acid or acidic aqueous solution used])×100) is preferably 10 to 100% by mass, and may be, for example, 20 to 90% by mass, 30 to 80% by mass, and 40 to 70% by mass. If the ratio is above the lower limit, the effect of using water will be more pronounced. If the ratio is below the upper limit, excessive use of water will be suppressed. Here, the amount of acid used is the same as described above.

[0131] In the acidification step (1), when mixing the mixed solution (a1), an acid or an acidic aqueous solution, and other components (13) as needed, it is preferable to perform the mixing under temperature conditions of 30 to 75°C, and more preferably under temperature conditions of 40 to 60°C. For example, when using water (13), it is preferable to mix in water (13) that has been adjusted (heated) to such a temperature.

[0132] The method of mixing the mixture (a1), the acid or acidic aqueous solution, and other components (13) as needed is not particularly limited and may be the same as or different from the method of mixing gelatin, an oily component, and other components (11) as needed in the emulsification step (1) described above in the presence of water.

[0133] In the acidification step (1), when adding the remaining components to the mixture (a1), the acid or acidic aqueous solution, and any other components (13) as needed, the remaining components may be added while stirring the mixture, or the remaining components may be added without stirring the mixture, and the mixture may be stirred after all the components have been combined.

[0134] In the acidification step (1), after mixing all the components (the mixed solution (a1), the acid or acidic aqueous solution, and other components (13) as needed), the time for stirring the resulting mixture may be, for example, 1 to 10 minutes.

[0135] In the acidification step (1), it is preferable to prepare an acidic mixture (b1) by adding or dropwise adding an acidic aqueous solution to the mixture (a1), and it is more preferable to prepare an acidic mixture (b1) by dropwise adding an acidic aqueous solution to the mixture (a1). When using water (13), it is preferable to prepare an acidic mixture (b1) by adding or dropping the water (13) onto the object.

[0136] From the start to the end of the acidification process (1), the minimum pH value of the liquid containing gelatin, a first anionic polymer, a second anionic polymer, and an inorganic compound is preferably 2 to 5, and more preferably 2 to 4. When the minimum pH value is below the upper limit, the gelatin, together with the first anionic polymer, the second anionic polymer, and the inorganic compound, forms a more stable wall material. When the minimum pH value is above the lower limit, an excessive decrease in the pH of the liquid is avoided. The liquid may be, for example, the mixed solution (b1), or it may be a mixed solution in an intermediate stage before obtaining the mixed solution (b1).

[0137] <Cooling process (1)> In the cooling step, the mixed liquid (b1) is cooled until its temperature reaches 10°C or below. Cooling the mixture (b1) promotes the precipitation of wall material containing oily components within the mixture (b1).

[0138] The temperature of the mixed liquid (b1) during cooling is preferably 0 to 10°C, and more preferably 2 to 9°C. A temperature below the upper limit allows for a more pronounced cooling effect of the mixed liquid (b1). A temperature above the lower limit suppresses excessive cooling of the mixed liquid (b1).

[0139] The cooling rate of the mixture (b1) is not particularly limited, but is preferably 0.2 to 2.0°C / min, and more preferably 0.3 to 1.0°C / min. By having a cooling rate within this range, the cooling effect of the mixture (b1) is more pronounced.

[0140] <Crosslinking agent mixing process (1)> In the crosslinking agent mixing step (1), a microcapsule aqueous dispersion (1) is prepared by mixing the cooled mixture (b1) with the crosslinking agent. By performing this process, microcapsules with a small average particle size and high heat resistance, which are the target, can be obtained as an aqueous dispersion. In the aqueous dispersion (1) described above, the crosslinking agent causes the wall material components to bond together, forming strong microcapsules of the wall material. The action of the crosslinking agent at this time is as described above. In other words, the aqueous dispersion (1) contains the target microcapsules.

[0141] The crosslinking agent used in the crosslinking agent mixing step (1) is the one described above, and a detailed explanation will be omitted here.

[0142] The crosslinking agent used in the crosslinking agent mixing step (1) may be one type or two or more types, and if there are two or more types, the combination and ratio of them can be arbitrarily selected.

[0143] In the crosslinking agent mixing step (1), depending on the type of crosslinking agent, the crosslinking agent may be blended alone or as an aqueous solution. Using an aqueous solution of the crosslinking agent may result in microcapsules with a more stable structure.

[0144] When a crosslinking agent aqueous solution and a mixed solution (b1) are combined, it is preferable to add the crosslinking agent aqueous solution to the mixed solution (b1), and the crosslinking agent aqueous solution may be added to the mixed solution (b1) all at once or dropwise. If the crosslinking agent is not added as an aqueous solution, it is preferable to add the crosslinking agent to the mixture (b1), and the crosslinking agent may be added to the mixture (b1) all at once or in stages.

[0145] In the crosslinking agent mixing step (1), the amount of crosslinking agent used is preferably 0.1 to 0.8 times the mass of the total amount of gelatin, the first anionic polymer, and the second anionic polymer in the mixed liquid (b1). For example, it may be 0.1 to 0.6 times, 0.1 to 0.4 times, and 0.1 to 0.2 times, or 0.2 to 0.8 times, 0.4 to 0.8 times, and 0.6 to 0.8 times, or 0.2 to 0.6 times. When the amount of crosslinking agent is above the lower limit, the wall material of the microcapsule becomes stronger. When the amount of crosslinking agent is below the upper limit, excessive use of the crosslinking agent is suppressed.

[0146] In the crosslinking agent mixing step (1), other components that do not fall under any of the following categories (sometimes referred to as "other components (14)" in this specification) may be mixed with gelatin, a first anionic polymer, a second anionic polymer, an inorganic compound, an oily component, an acid, or a crosslinking agent, as long as the effects of the present invention are not impaired.

[0147] The aforementioned other components (14) are not particularly limited and can be arbitrarily selected depending on the purpose. The other components (14) used in the crosslinking agent mixing step (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0148] Examples of the other component (14) include water.

[0149] In the crosslinking agent mixing step (1), the amount of the other component (14) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (14).

[0150] When the other component (14) is a component other than water, the ratio of the amount of the other component (14) used to the total amount of the mixture (b1) and the crosslinking agent used in the crosslinking agent mixing step (1) ([amount of other component (14) used] / ([amount of mixture (b1) used] + [amount of crosslinking agent used]) × 100) is usually 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less. When the ratio is within this range, microcapsules with a smaller average particle size and higher heat resistance can be obtained.

[0151] In the crosslinking agent mixing step (1), when mixing the mixed liquid (b1), the crosslinking agent or an aqueous solution of the crosslinking agent, and other components (14) as needed, it is preferable to perform the mixing under temperature conditions of 0 to 10°C, and more preferably under temperature conditions of 2 to 9°C. By mixing at such temperatures, microcapsules with a more stable structure can be obtained. The temperature range during the crosslinking agent mixing step (1) may or may not coincide with the temperature range of the mixed liquid (b1) in the cooling step.

[0152] The method of mixing the mixture (b1), the crosslinking agent or aqueous solution of the crosslinking agent, and other components (14) as needed is not particularly limited and may be the same as or different from the method of mixing gelatin, an oily component, and other components (11) as needed in the emulsification step (1) described above in the presence of water.

[0153] In the crosslinking agent mixing step (1), when adding the remaining components to the mixture (b1), the crosslinking agent or an aqueous crosslinking agent solution, and any other components (14) as needed, the remaining components may be added while stirring the target material, or the remaining components may be added without stirring the target material, and the mixture may be stirred after all components have been combined.

[0154] In the crosslinking agent mixing step (1), after mixing all the components (the mixed solution (b1), the crosslinking agent or aqueous crosslinking agent solution, and other components (14) as needed), the time for stirring the resulting mixture is preferably 1 minute to 15 hours, for example, 1 to 10 minutes or 1 to 15 hours, and can be appropriately selected depending on the type of crosslinking agent.

[0155] In the crosslinking agent mixing step (1), after all components (the mixed liquid (b1), the crosslinking agent or aqueous crosslinking agent solution, and other components (14) as needed) are combined, the temperature of the resulting mixture when it is stirred is preferably 15°C or higher, and may be, for example, 15 to 35°C. The time for stirring the mixture at such a temperature may be, for example, 1 to 5 hours.

[0156] If the crosslinking agent is an enzyme such as transglutaminase, in the crosslinking agent mixing step (1), it is preferable to mix all the components (the mixture (b1), the crosslinking agent or aqueous crosslinking agent solution, and other components (14) as needed), and then stir the resulting mixture at a temperature of 35 to 75°C. This allows for the deactivation of any excess enzyme. The time for stirring the mixture at such a temperature may be, for example, 5 to 30 minutes.

[0157] <Other processes (1)> The manufacturing method (1) may include other steps (1) that do not fall under any of the above-described emulsification step (1), emulsion mixing step (1), acidification step (1), cooling step (1), or crosslinking agent mixing step (1), as long as they do not impair the effects of the present invention. The type of other process (1), the number of other processes (1), and the timing of performing other processes (1) can be arbitrarily selected according to the purpose and are not particularly limited.

[0158] [Base mixing step (1)] The other step (1) mentioned above may include, for example, a step (sometimes referred to as the "base mixing step (1)" in this specification) in which the cooled mixture (b1) and a base are mixed between the cooling step (1) and the crosslinking agent mixing step (1) to produce a mixture (c1) with an adjusted pH. In other words, manufacturing method (1) consists of a cooling step (1) and A base mixing step (1) is performed to prepare a pH-adjusted mixture (c1) by mixing the cooled mixture (b1) with a base, The method may include a crosslinking agent mixing step (1) in which a crosslinking agent is mixed with the aforementioned mixed liquid (c1) to produce an aqueous dispersion of microcapsules (1). When the crosslinking agent is an enzyme such as transglutaminase, the base mixing step (1) is performed, and the pH of the mixture (b1) is adjusted to a range in which the activity of the enzyme is high (for example, a range including the optimal pH) to obtain the mixture (c1), thereby further improving the action of the crosslinking agent in the subsequent crosslinking agent mixing step (1).

[0159] The pH of the mixture (c1) obtained in the base mixing step (1) can be arbitrarily selected depending on the purpose and is not particularly limited, but is preferably 4 to 6.8, and when the crosslinking agent is an enzyme such as transglutaminase, it is preferably 5 to 6.5.

[0160] The base used in the base mixing step (1) is not particularly limited and may be, for example, an inorganic base or an organic base. Examples of the inorganic bases include alkali metal hydroxides such as sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH); alkali metal carbonates such as sodium carbonate (Na2CO3), potassium carbonate (K2CO3), and lithium carbonate (Li2CO3); and alkali metal bicarbonates such as sodium bicarbonate (NaHCO3) and potassium bicarbonate (KHCO3). Examples of the aforementioned organic bases include alkylamines such as triethylamine ((CH3CH2)3N).

[0161] The bases used in the base mixing step (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0162] In the base mixing step (1), the base may be mixed alone or as an aqueous solution. Using an aqueous base solution makes it easier to prepare a pH-adjusted mixture (c1).

[0163] The concentration of the base in the aqueous base solution used in the base mixing step (1) can be adjusted as appropriate depending on the type of base, but is preferably 10 to 40% by mass, and more preferably 20 to 30% by mass.

[0164] When the aforementioned aqueous base solution is combined with a mixed solution (b1), it is preferable to add the aqueous base solution to the mixed solution (b1). The aqueous base solution may be added to the mixed solution (b1) all at once or dropwise. If the base is not added as an aqueous solution, it is preferable to add the base to the mixture (b1). The base may be added to the mixture (b1) all at once, or it may be added dropwise or in portions.

[0165] In the base mixing step (1), the mixing of the mixture (b1) with the base or aqueous base solution is preferably carried out under temperature conditions of 0 to 10°C, and more preferably under temperature conditions of 2 to 9°C.

[0166] The method for mixing the mixture (b1) with the base or aqueous base solution is not particularly limited and may be the same as, or different from, the method used in the emulsification step (1) described above, in which gelatin, an oily component, and other components (11) as needed are mixed in the presence of water.

[0167] In the base mixing step (1), when adding the remaining substance to the mixture (b1) and either the base or the aqueous base solution, the remaining substance may be added while stirring the substance to be added, or the remaining substance may be added without stirring the substance to be added, and the mixture may be stirred after all the components have been combined.

[0168] In the base mixing step (1), after mixing all the components (mixture (b1) and the base or aqueous base solution), the time for stirring the resulting mixture may be, for example, 10 to 60 minutes. If the time is above the lower limit, the effect of using the base will be more pronounced. If the time is below the upper limit, it is possible to avoid the required time for the base mixing step (1) becoming excessively long.

[0169] Thus, when stirring the mixture obtained after blending all the components, it is preferable to stir the mixture under temperature conditions of 0 to 10°C, and more preferably under temperature conditions of 2 to 9°C.

[0170] In the base mixing step (1), it is preferable to prepare the mixture (c1) by adding or dropwise adding the aqueous base solution to the mixture (b1), and it is more preferable to prepare the mixture (c1) by dropwise adding the aqueous base solution to the mixture (b1). The addition or dropwise addition of the aqueous base solution to the mixed solution (b1) is preferably carried out under temperature conditions of 0 to 10°C, and more preferably under temperature conditions of 2 to 9°C.

[0171] In manufacturing method (1), when the base mixing step (1) is performed, the crosslinking agent mixing step (1) may be the same as the crosslinking agent mixing step (1) described above, except that the mixed solution (c1) is used instead of the cooled mixed solution (b1).

[0172] [Additional mixing process (1)] The aforementioned other step (1) may include, for example, a step of preparing a mixture (d1) by mixing the cooled mixture (b1) with the second anionic polymer between the cooling step (1) and the crosslinking agent mixing step (1) (this may be referred to as the "additional mixing step (1)" in this specification). Thus, in the manufacturing method (1), the second anionic polymer may be added and mixed to the cooled mixture (b1). In other words, manufacturing method (1) consists of a cooling step (1) and An additional mixing step (1) is performed to prepare a mixed liquid (d1) by mixing the cooled mixed liquid (b1) with the second anionic polymer. The method may include a crosslinking agent mixing step (1) in which a crosslinking agent is mixed with the aforementioned mixed liquid (d1) to produce an aqueous dispersion of microcapsules (1). By performing the additional mixing step (1), the aggregation or coalescence of the microcapsules themselves and the aggregation or coalescence of the wall material components in the process of forming the microcapsules are both highly suppressed in subsequent steps, and microcapsules with a smaller average particle size may be obtained.

[0173] The mixture (d1) contains gelatin (cationic polymer), a primary anionic polymer, a secondary anionic polymer, an inorganic compound, water, and an oily component.

[0174] The second anionic polymer used in the additional mixing step (1) is the one described above, and a detailed explanation will be omitted here.

[0175] The second anionic polymer used in the additional mixing step (1) may be the same as or different from the second anionic polymer used in the emulsion mixing step (1).

[0176] The second anionic polymer used in the additional mixing step (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0177] The mass ratio of [amount of second anionic polymer used in emulsion mixing step (1) (parts by mass)] to [amount of second anionic polymer used in additional mixing step (1) (parts by mass)] is preferably 75:25 to 25:75, and may be any of the following: 68:32 to 32:68, 61:39 to 39:61, and 55:45 to 45:55. Having the mass ratio within this range allows for the production of microcapsules with a smaller average particle size.

[0178] The total amount of the second anionic polymer used in the additional mixing step (1) and the emulsion mixing step (1) (the sum of the amount of the second anionic polymer used in the additional mixing step (1) and the amount of the second anionic polymer used in the emulsion mixing step (1)) is preferably 0.03 to 0.4 times the amount of gelatin used. By keeping the total amount within this range, the amount of the second anionic polymer or gelatin that does not contribute to the composition of the wall material can be reduced.

[0179] The amount of the first anionic polymer used in the emulsion mixing step (1) is preferably 40 to 60 times by mass the total amount of the second anionic polymer used in the additional mixing step (1) and the emulsion mixing step (1) (the sum of the amount of the second anionic polymer used in the additional mixing step (1) and the amount of the second anionic polymer used in the emulsion mixing step (1)). If the amount used is above the lower limit, the yield of microcapsules is further improved. If the amount used is below the upper limit, the heat resistance of the microcapsules is further improved.

[0180] The total amount of the first anionic polymer used in the emulsion mixing step (1), the total amount of the second anionic polymer used in the additional mixing step (1) and the emulsion mixing step (the total amount of the first anionic polymer used in the emulsion mixing step (1), the total amount of the second anionic polymer used in the additional mixing step (1), and the total amount of the second anionic polymer used in the emulsion mixing step (1)) is preferably 0.5 to 3.5 times the amount of gelatin used. If the total amount is above the lower limit, the yield of microcapsules is further improved. If the total amount is below the upper limit, the heat resistance of the microcapsules is further improved.

[0181] In the additional mixing step (1), for example, the second anionic polymer and the cooled mixture (b1) may be blended, or the aqueous solution of the second anionic polymer and the cooled mixture (b1) may be blended. Regardless of whether the second anionic polymer is blended alone or as an aqueous solution, water may or may not be added separately.

[0182] In the additional mixing step (1), the order in which the second anionic polymer or its aqueous solution, the cooled mixture (b1), and water as needed are added is not particularly limited.

[0183] In the additional mixing step (1), it is preferable to combine the aqueous solution of the second anionic polymer, the cooled mixture (b1), and water separately as needed. By doing so, a mixture (d1) with higher uniformity can be produced.

[0184] The concentration of the second anionic polymer in the aqueous solution of the second anionic polymer used in the additional mixing step (1) is preferably 3 to 20% by mass, and more preferably 5 to 12% by mass.

[0185] When a second anionic polymer aqueous solution is included, the target substance may be added to the second anionic polymer aqueous solution, or the second anionic polymer aqueous solution may be added to the target substance. When the target substance is added to the second anionic polymer aqueous solution, the target substance may be added to the second anionic polymer aqueous solution all at once, or added in stages or dropwise. When the second anionic polymer aqueous solution is added to the target substance, the second anionic polymer aqueous solution may be added to the target substance all at once, or added dropwise.

[0186] In the additional mixing step (1), gelatin, a first anionic polymer, a second anionic polymer, an inorganic compound, water, an oily component, and an acid, or other components (which may be referred to as "other components (15)" in this specification), may be mixed, to the extent that they do not impair the effects of the present invention.

[0187] The aforementioned other components (15) are not particularly limited and can be arbitrarily selected depending on the purpose. The other components (15) used in the additional mixing step (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0188] In the additional mixing step (1), the amount of the other component (15) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (15). Typically, in the additional mixing step (1), the ratio of the amount of other components (15) used to the total amount of the second anionic polymer and the cooled mixture (b1) used ([amount of other components (15)] / ([amount of second anionic polymer]+[amount of cooled mixture (b1)])×100) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less. When the ratio is within this range, microcapsules with a smaller average particle size and higher heat resistance can be obtained.

[0189] The additional mixing step (1) may be performed immediately following the cooling step (1). In this case, the temperature of the mixture (b1) at the start of the additional mixing step (1) is the same as the temperature of the mixture (b1) at the end of the cooling step (1).

[0190] In the additional mixing step (1), the mixing of the second anionic polymer or its aqueous solution, the cooled mixture (b1), and other components (15) as needed is preferably carried out under temperature conditions of 0 to 10°C, and more preferably under temperature conditions of 2 to 9°C. The temperature range during this mixing in the additional mixing step (1) may or may not coincide with the temperature range of the mixture (b1) in the cooling step (1).

[0191] The method for mixing the second anionic polymer or an aqueous solution thereof with the cooled mixture (b1) and, if necessary, other components (15) is not particularly limited and may be the same as or different from the method used in the emulsification step (1) described above, in which gelatin, an oily component, and, if necessary, other components (11) are mixed in the presence of water.

[0192] In the additional mixing step (1), when adding the remaining components to any of the additives, such as the second anionic polymer or its aqueous solution, the cooled mixture (b1), and other components (15) as needed, the remaining components may be added while stirring the additives, or the remaining components may be added without stirring the additives, and the mixture may be stirred after all the components have been combined.

[0193] In the additional mixing step (1), after blending all the components (the second anionic polymer or its aqueous solution, the cooled mixture (b1), and other components (15) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0194] In the additional mixing step (1), it is preferable to prepare the mixed solution (d1) by, for example, adding or dropwise adding a second anionic polymer aqueous solution to the cooled mixed solution (b1).

[0195] In manufacturing method (1), if an additional mixing step (1) is performed, the crosslinking agent mixing step (1) may be the same as the crosslinking agent mixing step (1) described above, except that the mixed liquid (d1) is used instead of the cooled mixed liquid (b1).

[0196] If the manufacturing method (1) includes both a base mixing step (1) and an additional mixing step (1), it is preferable that the additional mixing step (1) and the base mixing step (1) are performed in this order. By performing the additional mixing step (1) followed by the base mixing step (1), the effects obtained by performing these steps, namely the effect of highly suppressing both the aggregation or coalescence of the microcapsules themselves and the aggregation or coalescence of the wall material components in the microcapsule formation process, and the effect of further improving the action of the crosslinking agent, are most significantly obtained. In other words, an example of a preferred manufacturing method (1) is a cooling step (1) and An additional mixing step (1) is performed to prepare a mixed liquid (d1) by mixing the cooled mixed liquid (b1) with the second anionic polymer. A base mixing step (1) is performed to prepare a pH-adjusted mixture (c1) by mixing the aforementioned mixture (d1) with a base, A manufacturing method is provided which includes a crosslinking agent mixing step (1) in which a crosslinking agent is mixed with the aforementioned mixed liquid (c1) to produce an aqueous dispersion of microcapsules (1).

[0197] In manufacturing method (1), when the additional mixing step (1) and the base mixing step (1) are performed in this order, the additional mixing step (1) can be performed as previously described, the base mixing step (1) may be the same as the base mixing step (1) described earlier, except that the mixture (d1) is used instead of the cooled mixture (b1), and the crosslinking agent mixing step (1) may be the same as the crosslinking agent mixing step (1) described earlier, except that the mixture (c1) is used instead of the cooled mixture (b1).

[0198] The microcapsules obtained by manufacturing method (1) may be used as an aqueous dispersion as is, or the aqueous dispersion obtained after known post-treatment, purification, etc. may be used as is, or, if necessary, after known post-treatment, purification, etc., the dispersion medium may be removed and the microcapsules may be used individually. In any state (especially when the microcapsule is alone after the dispersion medium has been removed), the aforementioned microcapsules have a strong wall material, a small average particle size, and high heat resistance.

[0199] ◎Manufacturing method (2) A method for producing microcapsules according to one embodiment of the present invention comprises the steps of preparing an emulsion (2) by mixing gelatin, an inorganic compound, and an oily component in the presence of water (this may be referred to as the "emulsification step (2)" in this specification), A step of preparing a mixture (a2) by mixing a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, and the emulsion in the presence of water (this may be referred to as the "emulsifier mixing step (2)" in this specification), The process involves mixing the aforementioned mixture (a2) with an acid to produce an acidic mixture (b2) (this may be referred to as the "acidification step (2)" in this specification), The process of cooling the aforementioned mixture (b2) until its temperature is 10°C or lower (this may be referred to as "cooling step (2)" in this specification), The method comprises a step of producing an aqueous dispersion of microcapsules (2) by mixing the cooled mixture (b2) with a crosslinking agent (this may be referred to as the "crosslinking agent mixing step (2)" in this specification) (this manufacturing method may be referred to as the "manufacturing method (2)" in this specification).

[0200] Method (2) is also a method for manufacturing microcapsules using a composite coacervation method, and this method can be used to successfully manufacture the microcapsules of the present invention described above. Manufacturing method (2) is the same as manufacturing method (1), except that the inorganic compounds used in the formulation are different.

[0201] <Emulsification process (2)> In the emulsification step (2), an emulsion (2) is prepared by mixing gelatin, an inorganic compound, and an oily component in the presence of water. The emulsified liquid (2) contains gelatin, water, an inorganic compound, and an oily component.

[0202] The gelatin, inorganic compound, and oily component used in the emulsification step (2) are as previously described, and a detailed explanation is omitted here.

[0203] The gelatin, inorganic compound, and oily component used in the emulsification step (2) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0204] In the emulsification step (2), for example, gelatin, water, an inorganic compound, and an oily component may be blended, or an aqueous gelatin solution, an inorganic compound, and an oily component may be blended. Furthermore, in the emulsification step (2), a dispersion (21) obtained by mixing an inorganic compound with an aqueous gelatin solution may be used. That is, in the emulsification step (2), the dispersion (21) and an oily component may be blended together. When incorporating a gelatin aqueous solution or dispersion (21), water may or may not be added separately in addition to the water in the gelatin aqueous solution or dispersion (21).

[0205] In the emulsification step (2), the order in which gelatin, gelatin aqueous solution or dispersion (21), oily component, inorganic compound as needed, and water as needed is not particularly limited.

[0206] In the emulsification step (2), it is preferable to blend the gelatin aqueous solution or dispersion (21), the oily component, an inorganic compound as needed, and water as needed. By doing so, an emulsified solution (2) with higher uniformity can be produced.

[0207] In the emulsification step (2), other components that do not fall under any of the following categories (referred to herein as "other components (21)") may be mixed, to the extent that they do not impair the effects of the present invention.

[0208] The aforementioned other components (21) are not particularly limited and can be arbitrarily selected depending on the purpose. The other components ((21)) used in the emulsification step (2) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0209] In the emulsification step (2), the amount of the other component (21) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (21). Typically, in the emulsification step (2), the ratio of the amount of other components (21) used to the total amount of gelatin, inorganic compounds, oily components, and water used ([amount of other components (21)] / ([amount of gelatin]+[amount of inorganic compounds]+[amount of oily components]+[amount of water])×100) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less. When the ratio is within this range, microcapsules with a smaller average particle size and higher heat resistance can be obtained. Here, the amount of water used is the amount of water when gelatin, water, an inorganic compound, and an oily component are combined; when a gelatin aqueous solution or dispersion (21), an oily component, and an inorganic compound as necessary are combined, and no additional water is added, it is the amount of water in the gelatin aqueous solution or dispersion (21); and when a gelatin aqueous solution or dispersion (21), an oily component, and an inorganic compound as necessary are combined, and water is added separately, it is the total amount of water in the gelatin aqueous solution or dispersion (21) and the additional water added separately.

[0210] The emulsification step (2) is the same as the emulsification step (1), except that a dispersion (21) may be used instead of the gelatin aqueous solution, and an inorganic compound may be used. The manner in which the dispersion (21) is used in the emulsification step (2) may be the same as the manner in which the gelatin aqueous solution is used in the emulsification step (1). Further detailed explanation of the emulsification process (2) will be omitted.

[0211] <Emulsion mixing process (2)> In the emulsion mixing step (2), a mixture (a2) is prepared by mixing a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, and the emulsion (2) in the presence of water. The aforementioned mixture (a2) contains a first anionic polymer, a second anionic polymer, an inorganic compound, gelatin, water, and an oily component.

[0212] In the emulsion mixing step (2), by using the first anionic polymer and the second anionic polymer in combination, aggregation or coalescence of the wall material components in the microcapsule formation process is suppressed in subsequent steps.

[0213] The first anionic polymer and the second anionic polymer used in the emulsion mixing step (2) are the same as those described above, and a detailed explanation of them will be omitted here.

[0214] The first anionic polymer and the second anionic polymer used in the emulsion mixing step (2) may be one type each, or there may be two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected. The classification method for first-anionic polymers and second-anionic polymers is as explained above.

[0215] In the emulsion mixing step (2), for example, a first anionic polymer, a second anionic polymer, water, and emulsion (2) may be blended; or an aqueous solution of the first anionic polymer, a second anionic polymer, and emulsion (2) may be blended; or a first anionic polymer, an aqueous solution of the second anionic polymer, and emulsion (2) may be blended; or an aqueous solution of the first anionic polymer, an aqueous solution of the second anionic polymer, and emulsion (2) may be blended. When a first anionic polymer aqueous solution or a second anionic polymer aqueous solution is formulated, water may or may not be added separately in addition to the water in the first anionic polymer aqueous solution or the second anionic polymer aqueous solution.

[0216] In the emulsion mixing step (2), the order in which the first anionic polymer or aqueous solution of the first anionic polymer, the second anionic polymer or aqueous solution of the second anionic polymer, the emulsion (2), and water as needed are not particularly limited.

[0217] In the emulsion mixing step (2), it is preferable to combine the first anionic polymer aqueous solution, the second anionic polymer aqueous solution, the emulsion (2), and water separately as needed. By doing so, a mixture (a2) with higher uniformity can be produced.

[0218] The concentration of the first anionic polymer in the aqueous solution of the first anionic polymer used in the emulsion mixing step (2) may be the same as the concentration of the first anionic polymer in the aqueous solution of the first anionic polymer used in the emulsion mixing step (1). The concentration of the second anionic polymer in the aqueous solution of the second anionic polymer used in the emulsion mixing step (2) may be the same as the concentration of the second anionic polymer in the aqueous solution of the second anionic polymer used in the emulsion mixing step (1).

[0219] In the emulsified liquid mixing step (2) (step for preparing the mixed liquid (a2)), the amount of inorganic compound (in the case of manufacturing method (2), this may also be referred to as the "converted amount" in this specification) per 100 parts by mass of the total amount of gelatin, the first anionic polymer, and the second anionic polymer may be 2 to 17 parts by mass, but is preferably 3 to 13 parts by mass, and may be 4 to 9 parts by mass, 3 to 6 parts by mass, or 6 to 13 parts by mass. The heat resistance of the microcapsules is further improved when the amount of inorganic compound (converted amount) is above the lower limit. The microcapsule formation is further improved when the amount of inorganic compound (converted amount) is below the upper limit.

[0220] In the emulsified liquid mixing step (2), other components that do not fall under any of the following categories (i.e., the other components (12)) may be mixed, to the extent that they do not impair the effects of the present invention.

[0221] The aforementioned other components (12) are not particularly limited and can be arbitrarily selected depending on the purpose. The other components (12) used in the emulsifier mixing step (2) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0222] In the emulsifier mixing step (2), the amount of the other components (12) used is not particularly limited and can be adjusted as appropriate depending on the type of other components (12). Typically, in the emulsion mixing step (2), the ratio of the amount of other components (12) used to the total amount of the first anionic polymer, the second anionic polymer, water, and emulsion (2) used ([amount of other components (12)] / ([amount of first anionic polymer]+[amount of second anionic polymer]+[amount of water]+[amount of emulsion (2)])×100) is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less. When the ratio is within this range, microcapsules with a smaller average particle size and higher heat resistance can be obtained.

[0223] Here, the amount of water used refers to the amount of water used when mixing the first anionic polymer, the second anionic polymer, water, and emulsion (2). Furthermore, if the first anionic polymer aqueous solution, the second anionic polymer, and the emulsion (2) are combined, and no additional water is added, then the amount of water is the amount of water in the first anionic polymer aqueous solution. Furthermore, when a first anionic polymer aqueous solution, a second anionic polymer, an emulsion (2), and water are combined, the total amount of water is the sum of the water in the first anionic polymer aqueous solution and the water added separately. Furthermore, if the first anionic polymer, the second anionic polymer aqueous solution, and the emulsion (2) are combined, and no additional water is added, then the amount of water is the amount of water in the second anionic polymer aqueous solution. Furthermore, when a first anionic polymer, a second anionic polymer aqueous solution, an emulsion (2), and water are combined, the total amount of water is the sum of the water in the second anionic polymer aqueous solution and the water added separately. Furthermore, if the first anionic polymer aqueous solution, the second anionic polymer aqueous solution, and the emulsion (2) are combined and no additional water is added, the amount of water is the sum of the water in the first anionic polymer aqueous solution and the water in the second anionic polymer aqueous solution. Furthermore, when a first anionic polymer aqueous solution, a second anionic polymer aqueous solution, an emulsion (2), and water are combined, the total amount of water is the sum of the water in the first anionic polymer aqueous solution, the water in the second anionic polymer aqueous solution, and the water added separately.

[0224] The emulsion mixing step (2) is the same as the emulsion mixing step (1), except that emulsion (2) is used instead of emulsion (1) and inorganic compounds are not used. The manner in which the emulsion (2) is used in the emulsion mixing step (2) may be the same as the manner in which the emulsion (1) is used in the emulsion mixing step (1). In the emulsion mixing step (2), the manner in which the first anionic polymer or its aqueous solution is used may be the same as in the emulsion mixing step (1) in which the first anionic polymer or its aqueous solution is used. In the emulsion mixing step (2), the manner in which the second anionic polymer or its aqueous solution is used may be the same as in the emulsion mixing step (1) in which the second anionic polymer or its aqueous solution is used. Further detailed explanation of the emulsifier mixing step (2) will be omitted.

[0225] <Acidification step (2)> In the acidification step (2), an acidic mixture (b2) is prepared by mixing the mixture (a2) with an acid. The acid used in acidification step (2) is the same as the acid used in acidification step (1). The acidification step (2) may be the same as the acidification step (1), except that the mixture (a2) is used instead of the mixture (a1). In the acidification step (2), the manner in which the mixed solution (a2) and the acid are used may be the same as in the manner in which the mixed solution (a1) and the acid are used in the acidification step (1). Further detailed explanation of the acidification process (2) will be omitted.

[0226] <Cooling process (2)> In the cooling step (2), the mixed liquid (b2) is cooled until its temperature becomes 10°C or lower. By cooling the mixed liquid (b2), precipitation of the wall material encapsulating the oily component is promoted in the mixed liquid (b2).

[0227] The cooling step (2) is the same as the cooling step (1), except that the mixed liquid (b2) is used instead of the mixed liquid (b1). The mode of using the mixed liquid (b2) in the cooling step (2) may be the same as the mode of using the mixed liquid (b1) in the cooling step (1). Regarding the cooling step (2), further detailed description thereof is omitted.

[0228] <Crosslinking agent mixing step (2)> In the crosslinking agent mixing step (2), the microcapsule aqueous dispersion (2) is produced by mixing the cooled mixed liquid (b2) and a crosslinking agent. By performing this step, the target microcapsules having a small average particle diameter and high heat resistance are obtained as an aqueous dispersion. In the aqueous dispersion (2), due to the action of the crosslinking agent, the wall material components are linked to each other, and microcapsules with a strong wall material are formed. The action of the crosslinking agent at this time is as described above. That is, the aqueous dispersion (2) contains the target microcapsules.

[0229] The crosslinking agent mixing step (2) is the same as the crosslinking agent mixing step (1), except that the mixed liquid (b2) is used instead of the mixed liquid (b1). The mode of using the mixed liquid (b2) in the crosslinking agent mixing step (2) may be the same as the mode of using the mixed liquid (b1) in the crosslinking agent mixing step (1). Regarding the crosslinking agent mixing step (2), further detailed description thereof is omitted.

[0230] <Other steps (2)> The manufacturing method (2) may have other processes (2) that do not fall under any of the above-mentioned emulsification process (2), emulsion mixing process (2), acidification process (2), cooling process (2), and crosslinking agent mixing process (2) as long as the effects of the present invention are not impaired. The type of the other process (2), the number of the other processes (2), and the timing of performing the other process (2) can be arbitrarily selected according to the purpose and are not particularly limited.

[0231] [Base mixing process (2)] As the other process (2), for example, there is a process of preparing a mixed solution (c2) with adjusted pH by mixing the cooled mixed solution (b2) and a base between the cooling process (2) and the crosslinking agent mixing process (2) (in this specification, it may be referred to as the "base mixing process (2)"). That is, the manufacturing method (2) includes a cooling process (2) and a base mixing process (2) of preparing a mixed solution (c2) with adjusted pH by mixing the cooled mixed solution (b2) and a base, and a crosslinking agent mixing process (2) of preparing an aqueous dispersion (2) of microcapsules by mixing the mixed solution (c2) and a crosslinking agent, and may have these. When the crosslinking agent is an enzyme such as transglutaminase, by performing the base mixing process (2) and adjusting the pH of the mixed solution (b2) to a range where the activity of the enzyme is high (for example, a range including the optimum pH) to obtain the mixed solution (c2), the action of the crosslinking agent can be further improved in the subsequent crosslinking agent mixing process (2).

[0232] The base mixing process (2) is the same as the base mixing process (1) except that the mixed solution (b2) is used instead of the mixed solution (b1). The base used in the base mixing process (2) may be the same as the base used in the base mixing process (1). The modes of using the mixed solution (b2) and the base in the base mixing process (2) may be the same as the modes of using the mixed solution (b1) and the base in the base mixing process (1), respectively. Further detailed explanation of the base mixing step (2) will be omitted.

[0233] [Additional mixing process (2)] The aforementioned other step (2) may include, for example, a step of preparing a mixture (d2) by mixing the cooled mixture (b2) with the second anionic polymer between the cooling step (2) and the crosslinking agent mixing step (2) (this may be referred to as the "additional mixing step (2)" in this specification). Thus, in the manufacturing method (2), the second anionic polymer may be added and mixed to the cooled mixture (b2). In other words, manufacturing method (2) consists of a cooling step (2) and An additional mixing step (2) is performed to prepare a mixed liquid (d2) by mixing the cooled mixed liquid (b2) with the second anionic polymer. The method may include a crosslinking agent mixing step (2) in which a crosslinking agent is mixed with the aforementioned mixed liquid (d2) to produce an aqueous dispersion of microcapsules (2). By performing the additional mixing step (2), the aggregation or coalescence of the microcapsules themselves and the aggregation or coalescence of the wall material components in the process of forming the microcapsules are both highly suppressed in subsequent steps, and microcapsules with a smaller average particle size may be obtained.

[0234] The mixture (d2) contains gelatin (cationic polymer), a first anionic polymer, a second anionic polymer, an inorganic compound, water, and an oily component.

[0235] The additional mixing step (2) is the same as the additional mixing step (1), except that the mixture (b2) is used instead of the mixture (b1). The second anionic polymer used in the additional mixing step (2) may be the same as the second anionic polymer used in the additional mixing step (1). The manner in which the mixture (b2) and the second anionic polymer are used in the additional mixing step (2) may be the same as the manner in which the mixture (b1) and the second anionic polymer are used in the additional mixing step (1). Further detailed explanation of the additional mixing step (2) will be omitted.

[0236] If the manufacturing method (2) includes both a base mixing step (2) and an additional mixing step (2), it is preferable that the additional mixing step (2) and the base mixing step (2) are performed in this order. By performing the additional mixing step (2) followed by the base mixing step (2), the effects obtained by performing these steps, namely the effect of highly suppressing both the aggregation or coalescence of the microcapsules themselves and the aggregation or coalescence of the wall material components in the microcapsule formation process, and the effect of further improving the action of the crosslinking agent, are most significantly obtained. In other words, an example of a preferred manufacturing method (2) is a cooling step (2) and An additional mixing step (2) is performed to prepare a mixed liquid (d2) by mixing the cooled mixed liquid (b2) with the second anionic polymer. The base mixing step (2) involves mixing the aforementioned mixture (d2) with a base to prepare a mixture (c2) with adjusted pH, A manufacturing method is provided which includes a crosslinking agent mixing step (2) in which a crosslinking agent is mixed with the aforementioned mixed liquid (c2) to produce an aqueous dispersion of microcapsules (2).

[0237] In manufacturing method (2), when the additional mixing step (2) and the base mixing step (2) are performed in this order, the additional mixing step (2) can be performed as previously described, the base mixing step (2) may be the same as the base mixing step (2) described earlier, except that the mixture (d2) is used instead of the cooled mixture (b2), and the crosslinking agent mixing step (2) may be the same as the crosslinking agent mixing step (2) described earlier, except that the mixture (c2) is used instead of the cooled mixture (b2).

[0238] The microcapsules obtained by manufacturing method (2) may be used as an aqueous dispersion as is, or the aqueous dispersion obtained by performing known post-treatment, purification, etc. may be used as is, or, if necessary, after performing known post-treatment, purification, etc., the dispersion medium may be removed and the microcapsules may be used individually. In any state (especially when the microcapsule is alone after the dispersion medium has been removed), the aforementioned microcapsules have a strong wall material, a small average particle size, and high heat resistance.

[0239] In both manufacturing methods (1) and (2), the inorganic compound is incorporated during the formation of the wall material when manufacturing microcapsules. The inorganic compound is incorporated into a portion of these materials at a stage before the gelatin, the first anionic polymer, and the second anionic polymer all coexist. In this respect, manufacturing methods (1) and (2) have commonalities. [Examples]

[0240] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited in any way to the examples shown below.

[0241] [Example 1] <<Microcapsule Manufacturing>> A gelatin aqueous solution with a concentration of 4.7% by mass was prepared by adding 6g of gelatin ("Type A gelatin" manufactured by Nitta Gelatin Co., Ltd.) to 122g of distilled water and dissolving it by heating at 50°C. A 7.8% by mass aqueous solution of gum arabic was prepared by adding 10 g of gum arabic (manufactured by Nacalai Tesque, equivalent to a first anionic polymer) to 118 g of distilled water and dissolving it by heating at 50°C. Furthermore, while this aqueous solution of gum arabic was still heated at 50°C, 0.8 g of talc (manufactured by Nippon Talc Co., Ltd., "NanoAce D600", average particle size 0.7 μm, equivalent to an inorganic compound) was added and dispersed to prepare dispersion (1). Sodium carboxymethyl cellulose (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., corresponding to the second anionic polymer) (0.2 g) was dissolved in distilled water (1.8 g) to prepare an aqueous solution of sodium carboxymethyl cellulose with a concentration of 10% by mass.

[0242] While heating the entire amount (128 g) of the gelatin aqueous solution obtained above at 50°C, essential oil of peppermint at room temperature (manufactured by Sin Co., corresponding to the oily component) (50 g) was added thereto, and using an emulsifier, it was stirred at a stirring speed of 3000 rpm for 5 minutes at room temperature to prepare an emulsion (1) (emulsification step (1)). While heating the entire amount (128.8 g) of the dispersion (1) obtained above at 50°C, the entire amount (178 g) of the emulsion (1) was added thereto, and using an emulsifier, it was stirred at a stirring speed of 350 rpm at room temperature. Furthermore, the entire amount (2 g) of the aqueous solution of sodium carboxymethyl cellulose at room temperature obtained above was added thereto, and it was stirred for 2 minutes at room temperature to prepare a mixed solution (a1) (emulsion mixing step (1)).

[0243] Next, while stirring the mixed solution (a1) under the condition of 50°C, an aqueous solution of citric acid (manufactured by Fujifilm Wako Pure Chemical Corporation) with a concentration of 50% by mass at room temperature was dropped thereto, and it was stirred to adjust the pH of the mixed solution (a1) to 3.8, thereby preparing an acidic mixed solution (b1) (acidification step (1)). Next, while stirring the obtained mixed solution (b1) at a cooling rate of 0.5°C / min, it was cooled until its temperature became 10°C or lower (cooling step (1)). Next, while maintaining the temperature of the mixed solution (b1) at 10°C or lower and stirring, an aqueous solution of sodium hydroxide (manufactured by Kanto Chemical Co., Inc.) with a concentration of 24% by mass was dropped thereto to adjust the pH of the mixed solution (b1) to 6.0, and a mixed solution (c1) was obtained (base mixing step (1)). While maintaining the temperature of the resulting mixture (c1) below 10°C, transglutaminase (Ajinomoto Co., Ltd.'s "Activa TG-S," equivalent to a crosslinking agent) (5g) was added. The temperature of the solution after the addition was raised to 20°C, and the solution was stirred overnight while maintaining this temperature (crosslinking agent mixing step (1)). Furthermore, the temperature of the solution was raised to 30°C, and the solution was stirred for 4 hours while maintaining this temperature. Finally, the temperature of the solution was raised to 70°C, and the solution was stirred for 15 minutes while maintaining this temperature to inactivate the excess transglutaminase. Based on the above, microcapsules comprising gelatin, gum arabic, sodium carboxymethylcellulose, transglutaminase, and talc, and containing peppermint essential oil as a core substance, were obtained as an aqueous dispersion (aqueous dispersion (1)).

[0244] <<Evaluation of Microcapsules>> <Evaluation of microcapsule formation ability> Using a wire bar, the aqueous dispersion of the freshly manufactured microcapsules obtained above was coated onto fine paper and dried in an oven at 105°C for 2.5 minutes. Subsequently, imaging data of the dried material obtained above was acquired using a scanning electron microscope (SEM, JEOL Ltd. "JSM-6700F"). Separately, the aqueous dispersion of microcapsules obtained in Comparative Example 1, described later, was similarly dried, and imaging data of the resulting dried product was acquired. Based on these imaging data, the microcapsules in the dried material obtained in this embodiment were compared with the microcapsules in the dried material obtained in Comparative Example 1 in terms of sphericity (degree of closeness to a true sphere) and the proportion of indentations (the proportion of microcapsules showing indentations). The degree to which the microcapsules were normally formed, i.e., the microcapsule formation ability, was evaluated according to the following criteria. The results are shown in Table 1. [Evaluation Criteria] A: No difference was observed in either the sphericity or the proportion of indentations, indicating good microcapsule formation. B: A difference is observed in at least one aspect of the ratio of sphericity to concavity, indicating poor microcapsule formation.

[0245] <Evaluation of the content of inorganic compounds in microcapsules> From the imaging data obtained above, the presence or absence of talc (plate-like particles) on the surface of the microcapsules was confirmed, and the degree to which the microcapsules were composed of inorganic compounds, i.e., the inorganic compound content of the microcapsules, was evaluated according to the following criteria. The results are shown in Table 1. [Evaluation Criteria] A: Numerous plate-like particles are attached to the surface of the microcapsules, resulting in good content of inorganic compounds within the microcapsules. B: The microcapsules either have no plate-like particles attached to their surface, or only a small number of plate-like particles attached, resulting in poor content of the inorganic compound within the microcapsules.

[0246] <Evaluation of the heat resistance of microcapsules> Using the same method as described above for evaluating the microcapsule formation ability, the aqueous dispersion of microcapsules immediately after manufacturing was dried, and SEM imaging data of the dried product was obtained. Separately, the aqueous dispersion of microcapsules obtained above was heated at 50°C and continuously stirred using a mixing rotor. Then, a portion of the aqueous dispersion was taken out, coated onto fine paper, and dried in an oven at 105°C for 2.5 minutes. Next, imaging data of the dried material obtained above was acquired using a scanning electron microscope (SEM, JEOL Ltd. "JSM-6700F"). The image data of the dried aqueous dispersion of microcapsules immediately after manufacturing, i.e., the dried aqueous dispersion without heating and stirring (hereinafter sometimes referred to as the "initial dried product"), obtained as described above, and the image data of the dried aqueous dispersion after heating and stirring (hereinafter sometimes referred to as the "dried product after heating and stirring") were compared to determine the number of microcapsules in the dried product after heating and stirring that showed indentations or other shape abnormalities (hereinafter, these may be collectively referred to as "shape abnormalities"). tFrom the number of microcapsules (number of units) and the number of microcapsules N0 (number of units) in the initial dried material that exhibit dents or other shape abnormalities, the increase rate R of the number of microcapsules exhibiting these shape abnormalities is calculated using the following formula. t The percentage (%) was calculated, and the heat resistance of the microcapsules was evaluated according to the following criteria. The results are shown in Table 1. R t (%)=(N t -N0) / N0×100 [Evaluation Criteria] A: The number of microcapsules exhibiting indentations or other shape abnormalities has not increased, or has increased only slightly. B: The number of microcapsules showing indentations or other shape abnormalities is higher than in case A, but the rate of increase R t The percentage is less than 30%. C: The number of microcapsules exhibiting indentations or other shape abnormalities is increased compared to case B, with an increase rate of R. t The percentage is 30% or more.

[0247] <Measurement of average particle size of microcapsules> The average particle size of the microcapsules was measured from the imaging data of the initial dried material obtained during the evaluation of the heat resistance of the microcapsules described above. The results are shown in Table 1.

[0248] <<Manufacturing and Evaluation of Microcapsules>> [Example 2] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that the amount of talc was changed from 0.8 g to 1.25 g. The results are shown in Table 1. In Table 1, the amount of inorganic compound (converted amount) per 100 parts by mass of the total amount of gelatin, the first anionic polymer, and the second anionic polymer is shown in the "Converted amount of inorganic compound (g)" column.

[0249] [Example 3] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that the amount of talc was changed from 0.8 g to 2.5 g. The results are shown in Table 1.

[0250] [Example 4] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that the amount of talc was changed from 0.8 g to 0.4 g. The results are shown in Table 1.

[0251] [Reference example 1] Except for changing the amount of talc from 0.8g to 5g, the same method as in Example 1 was used for the production and evaluation of microcapsules. The results are shown in Table 1.

[0252] [Comparative Example 1] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that talc was not included. The results are shown in Table 2.

[0253] [Reference example 2] <<Microcapsule Manufacturing>> Using the same method as in Example 1, an aqueous gelatin solution with a concentration of 4.7% by mass, an aqueous gum arabic solution with a concentration of 7.8% by mass, and an aqueous carboxymethylcellulose sodium solution with a concentration of 10% by mass were prepared.

[0254] The entire amount (128g) of the gelatin aqueous solution obtained above was heated at 50°C, and 50g of peppermint essential oil (manufactured by Sin Co., Ltd., corresponding to the oily component) at room temperature was added thereto. An emulsifier was used to stir at a stirring speed of 3000 rpm for 5 minutes at room temperature to prepare emulsion (1). The entire amount (128 g) of the 50°C gum arabic aqueous solution obtained above was added to the entire amount (178 g) of the 50°C emulsion (1), and the mixture was stirred at room temperature using an emulsifier at a stirring speed of 350 rpm. Next, the entire amount (2g) of the carboxymethylcellulose sodium aqueous solution heated to 50°C, obtained above, was added and stirred at room temperature for 2 minutes to prepare a mixture (r1).

[0255] Next, under conditions of 50°C, while stirring the mixture (r1), 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 and stirred to adjust the pH of the mixture (r1) to 3.8, thereby preparing an acidic mixture (r2). Next, the resulting mixture (r2) was cooled at a cooling rate of 0.5°C / min while being stirred until its temperature fell below 10°C. Next, while maintaining the temperature of the mixture (r2) below 10°C and stirring, talc (NanoAce D600, manufactured by Nippon Talc Co., Ltd., average particle size 0.7 μm, equivalent to an inorganic compound) (2.5 g) was added and mixed to obtain the mixture (r3). Next, an aqueous solution of sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) with a concentration of 24% by mass was added dropwise to the obtained mixture (r3) to adjust the pH of the mixture (r3) to 6.0, thereby obtaining mixture (r4). While maintaining the temperature of the resulting mixture (r4) below 10°C, transglutaminase (Ajinomoto Co., Ltd.'s "Activa TG-S," equivalent to a crosslinking agent) (5g) was added. The temperature of the solution after the addition was raised to 20°C, and the solution was stirred overnight while maintaining this temperature. Furthermore, the temperature of the solution was raised to 30°C, and the solution was stirred for 4 hours while maintaining this temperature. Finally, the temperature of the solution was raised to 70°C, and the solution was stirred for 15 minutes while maintaining this temperature to inactivate the excess transglutaminase. Based on the above, microcapsules comprising gelatin, gum arabic, sodium carboxymethylcellulose, and transglutaminase, further blended with talc, and containing peppermint essential oil as a core substance, were obtained as an aqueous dispersion.

[0256] <<Evaluation of Microcapsules>> The microcapsules obtained above were evaluated using the same method as in Example 1. The results are shown in Table 2.

[0257] [Reference example 3] <<Microcapsule Manufacturing>> The mixture (r2) was cooled using the same method as in Reference Example 1. Next, while maintaining the temperature of the mixture (r2) below 10°C and stirring, an aqueous solution of sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) with a concentration of 24% by mass was added dropwise to adjust the pH of the mixture (r2) to 6.0, thereby obtaining the mixture (r5). While maintaining the temperature of the resulting mixture (r5) below 10°C, transglutaminase (Ajinomoto Co., Ltd.'s "Activa TG-S," equivalent to a crosslinking agent) (5g) was added. The temperature of the solution after the addition was raised to 20°C, and the solution was stirred overnight while maintaining this temperature. Furthermore, the temperature of the solution was raised to 30°C, and the solution was stirred for 4 hours while maintaining this temperature. Finally, the temperature of the solution was raised to 70°C, and the solution was stirred for 15 minutes while maintaining this temperature to inactivate the excess transglutaminase. Next, talc (NanoAce D600, manufactured by Nippon Talc Co., Ltd., average particle size 0.7 μm, equivalent to an inorganic compound) (4.7 g) was added to this solution and mixed. Based on the above, microcapsules comprising gelatin, gum arabic, sodium carboxymethylcellulose, and transglutaminase, further blended with talc, and containing peppermint essential oil as a core substance, were obtained as an aqueous dispersion.

[0258] <<Evaluation of Microcapsules>> The microcapsules obtained above were evaluated using the same method as in Example 1. The results are shown in Table 2.

[0259] [Reference example 4] Microcapsules were manufactured and evaluated using the same method as in Reference Example 3, except that the amount of talc was changed from 4.7g to 2.35g. The results are shown in Table 2.

[0260] [Table 1]

[0261] [Table 2]

[0262] As is clear from the results above, in Examples 1 to 4, the formation of microcapsules was good, and the wall material was able to obtain strong microcapsules by the composite coacervation method. Furthermore, in Examples 1 to 4, the average particle size of the microcapsules was 27.2 μm or less (24.7 to 27.2 μm), which was sufficiently small. Furthermore, in Examples 1-4, even after heating and stirring the microcapsules at 50°C for one week, the increase rate R of the number of microcapsules showing shape abnormalities was observed. t The R was low, and in these examples, the heat resistance of the microcapsules was high. In these examples, the content of the inorganic compound in the microcapsules was good, which was consistent with the high heat resistance of the microcapsules. In particular, in Examples 1 and 2, even when the microcapsules were heated and stirred at 50°C for more than two weeks, the increase rate R remained low. t This suppressed the heat-resistant properties of the microcapsules, resulting in extremely high heat resistance.

[0263] In Examples 1-4, inorganic compounds were incorporated during the formation of the wall material in the manufacturing of microcapsules. More specifically, the inorganic compounds were incorporated into a portion of these materials at a stage before gelatin, the first anionic polymer, and the second anionic polymer all coexisted. In Examples 1 to 4, the converted amount of the inorganic compound was 2.5 to 15.4 parts by mass, and in Examples 1 to 2, the converted amount of the inorganic compound was 4.9 to 7.7 parts by mass.

[0264] In contrast, in Comparative Example 1, the formation of microcapsules was good, and a strong wall material was obtained using the composite coacervation method, but the heat resistance of the microcapsules was inferior to that of Examples 1 to 4. In Comparative Example 1, no inorganic compounds were included.

[0265] In Reference Example 1, the microcapsule formation was poor, and microcapsules could not be formed properly. Therefore, in Reference Example 1, evaluations other than microcapsule formation were not performed. In Reference Example 1, the converted blending amount of the inorganic compound was 30.9 parts by mass, which was excessive.

[0266] In Reference Example 2, the formation of microcapsules was poor, and furthermore, the average particle size of the microcapsules was large. In Reference Example 2, during the manufacturing of microcapsules, the inorganic compound was added after the formation of the wall material and before crosslinking (before the addition of the crosslinking agent). It was presumed that the inorganic compound was unevenly distributed on or near the surface of the wall material, resulting in inhibited crosslinking. In Reference Example 2, the heat resistance of the microcapsules was not evaluated.

[0267] In Reference Examples 3-4, the increase rate R of the number of microcapsules showing shape abnormalities was observed after heating and stirring the microcapsules at 50°C for one week. t The heat resistance was high, and in these reference examples, the heat resistance of the microcapsules was low. In Reference Examples 3 and 4, it was hypothesized that during the manufacturing of microcapsules, inorganic compounds were added after the crosslinking agent was deactivated, and as a result of the inorganic compounds being unevenly distributed on the surface of the wall material, they were unable to perform their function. [Industrial applicability]

[0268] The present invention can be used as a microcapsule requiring a small average particle size, and is particularly suitable as a microcapsule used in the presence of water.

Claims

1. It is a microcapsule, The microcapsule is composed of gelatin, a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, a crosslinking agent, and an inorganic compound. The average particle size of the inorganic compound is 1 μm or less. The microcapsule contains talc as the inorganic compound, In the microcapsule, the amount of the inorganic compound is 2 to 17 parts by mass with respect to 100 parts by mass of the total amount of gelatin, the first anionic polymer, and the second anionic polymer. The aforementioned microcapsules contain an oily component, A microcapsule having an average particle diameter of 30 μm or less.

2. The microcapsule according to claim 1, wherein the oily component is a fragrance.

3. The microcapsule according to claim 1 or 2, wherein the crosslinking agent is transglutaminase.

4. A step of preparing an emulsion (1) by mixing gelatin and an oily component in the presence of water, A step of preparing a mixed solution (a1) by mixing a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, an inorganic compound, and the emulsion (1) in the presence of water. The process involves mixing the aforementioned mixture (a1) with an acid to produce an acidic mixture (b1), The steps include: cooling the aforementioned mixture (b1) until its temperature is 10°C or lower; The process includes a step of mixing the cooled mixture (b1) with a crosslinking agent to produce an aqueous dispersion of microcapsules (1), In the step of preparing the aforementioned mixed liquid (a1), talc is mixed as the inorganic compound, A method for producing microcapsules, wherein in the step of preparing the mixed liquid (a1), the amount of the inorganic compound is 2 to 17 parts by mass per 100 parts by mass of the total amount of the gelatin, the first anionic polymer, and the second anionic polymer.

5. A step of preparing an emulsion (2) by mixing gelatin, an inorganic compound, and an oily component in the presence of water, A step of preparing a mixed solution (a2) by mixing a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, and the emulsion in the presence of water. The process involves mixing the aforementioned mixture (a2) with an acid to produce an acidic mixture (b2), The process involves cooling the aforementioned mixture (b2) until its temperature reaches 10°C or below. The process includes a step of mixing the cooled mixture (b2) with a crosslinking agent to produce an aqueous dispersion of microcapsules (2), In the step of preparing the emulsion (2), talc is mixed as the inorganic compound. A method for producing microcapsules, wherein in the step of preparing the mixed liquid (a2), the amount of the inorganic compound is 2 to 17 parts by mass per 100 parts by mass of the total amount of the gelatin, the first anionic polymer, and the second anionic polymer.

6. A method for producing microcapsules according to claim 4 or 5, wherein in the step of producing the mixed solution (a1) or the step of producing the mixed solution (a2), the amount of the inorganic compound is 3 to 13 parts by mass per 100 parts by mass of the total amount of the gelatin, the first anionic polymer, and the second anionic polymer.

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