Microcapsules and methods for manufacturing the same

Abstract

To provide a novel microcapsule which has lavender essential oil as a core material and can be produced by the composite coacervation method, and which has a small particle diameter and has high retention performance of the core material even in a state where the microcapsule is dried.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, and a cross-linking agent, wherein the microcapsule encapsulates a lavender essential oil and one or two or more selected from the group consisting of a polyoxyalkylene alkyl ether having an HLB value of 10.0 or less and a sorbitan fatty acid ester having an HLB value of 10.0 or less, and has an average particle diameter of 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 constructed by encapsulating the target component as a core material within the wall material. Furthermore, it is possible to design microcapsules to have a sustained-release property, gradually releasing the encapsulated oily component to the outside over time. 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, typically, an emulsion is prepared in the initial stage by mixing a cationic polymer with a core material, and then this emulsion is mixed with an anionic polymer to create microcapsules. Gelatin is commonly used as the cationic polymer. As described above, microcapsules manufactured by preparing an emulsified solution using gelatin include microcapsules with lavender essential oil as the core material and whose sustained release properties are adjusted (see Patent Document 1), and microcapsules with peppermint essential oil as the core material and which have sustained release properties (see Patent Document 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-159661 [Patent Document 2] Japanese Patent Application Publication No. 11-12105 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, when gelatin is used, the stability of the emulsion may be low, and if microcapsules are made under such conditions, the microcapsules may not be able to stably encapsulate the core material (encapsulation retention performance). For example, when the microcapsules are dried, the encapsulated core material may leak out of the microcapsule, or the core material may not remain inside the microcapsule (the microcapsule may not encapsulate the core material). In this way, if the encapsulation retention performance of the core material of the microcapsule deteriorates, one of the characteristics of microcapsules, such as sustained release, is lost.

[0006] It has become clear that the stability of emulsified solutions using gelatin is influenced by the particle size of the microcapsules and the type of core material. For example, microcapsules with larger particle sizes tend to have higher emulsification stability because it is easier to encapsulate the core material. On the other hand, lavender essential oil is a natural essential oil containing many trace components, and when such lavender essential oil is used as the core material, the stability of the emulsified solution tends to be low. In other words, there was a problem in that it was difficult to produce a highly stable emulsified solution using gelatin and lavender essential oil, and then to manufacture microcapsules with small particle sizes, using lavender essential oil as the core material, and maintaining high core material encapsulation and retention performance even in a dried state from such an emulsified solution.

[0007] In contrast, the microcapsules disclosed in Patent Document 1 use lavender essential oil as the core material, but the particle size of the microcapsules is large. The microcapsules disclosed in Patent Document 2 have a small particle size, but they do not use lavender essential oil as the core material.

[0008] The present invention aims to provide a novel microcapsule that uses lavender essential oil as a core material and can be manufactured by a composite coacervation method, wherein the microcapsule has a small particle size and maintains high encapsulation and retention performance of its core material even when the microcapsule is dried. [Means for solving the problem]

[0009] 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, and a crosslinking agent, wherein the microcapsule contains lavender essential oil and one or more selected from the group consisting of polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less and sorbitan fatty acid esters with an HLB value of 10.0 or less, and the average particle size of the microcapsule is 30 μm or less. [2] The microcapsule according to [1], wherein the crosslinking agent is one or more selected from the group consisting of transglutaminase, polyphenols, and glutaraldehyde.

[0010] [3]. A step of preparing a mixed solution (z) by mixing lavender essential oil and one or more selected from the group consisting of polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less and sorbitan fatty acid esters with an HLB value of 10.0 or less; a step of preparing an emulsion by mixing gelatin and the mixed solution (z) in the presence of water; and a step of mixing a first anionic polymer and a second anionic polymer of a different type from the first anionic polymer and the emulsion in the presence of water. A method for producing microcapsules, comprising the steps of: preparing a mixed solution (a) by mixing and; preparing an acidic mixed solution (b) by mixing the mixed solution (a) with an acid and; cooling the mixed solution (b) until its temperature is 10°C or lower; preparing a mixed solution (c) by mixing the cooled mixed solution (b) with a crosslinking agent and; and preparing an aqueous dispersion of microcapsules with adjusted pH by mixing the mixed solution (c) with a base and. [4] The method for producing microcapsules according to [3], wherein the crosslinking agent is one or more selected from the group consisting of transglutaminase, polyphenols, and glutaraldehyde. [Effects of the Invention]

[0011] According to the present invention, a novel microcapsule is provided that uses lavender essential oil as a core material and can be manufactured by a composite coacervation method, wherein the microcapsule has a small particle size and maintains high encapsulation and retention performance of its core material even when the microcapsule is dried. [Modes for carrying out the invention]

[0012] <<Microcapsules>> A microcapsule according to one embodiment of the present invention comprises gelatin, a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, and a crosslinking agent, and the microcapsule contains lavender essential oil and one or more selected from the group consisting of polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less and sorbitan fatty acid esters with an HLB value of 10.0 or less, and the average particle size of the microcapsule is 30 μm or less.

[0013] The microcapsules of this embodiment contain, along with lavender essential oil, one or more substances selected from the group consisting of polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less and sorbitan fatty acid esters with an HLB value of 10.0 or less as a core material. As a result, the microcapsules of this embodiment have high performance in retaining the core material even when dried, and have a high ability to maintain the state in which the core material is contained (in other words, the normal state of the microcapsule). The microcapsules of this embodiment are manufactured by a composite coacervation method described later, and therefore have a small particle size. In the composite coacervation method, during production using the manufacturing method described later, a highly stable emulsion is prepared by using one or more substances selected from the group consisting of a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less and a sorbitan fatty acid ester with an HLB value of 10.0 or less (in this specification, these may be collectively referred to as "additives") in addition to gelatin and lavender essential oil, and by preparing microcapsules from such an emulsion, the microcapsules of this embodiment have the excellent properties described above.

[0014] The microcapsules in this embodiment are constructed by enclosing a core material within a wall material. The aforementioned microcapsules can be manufactured by applying a composite coacervation method, as described later. The gelatin, the first anionic polymer, and the second anionic polymer are components of the wall material of the microcapsules (which may be abbreviated as "wall material components" in this specification), and the wall material is formed by the complex coacervation method.

[0015] ◎Wall material, wall material component 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.

[0016] <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 that constitutes the wall material is a cationic polymer having a cationic part in its molecule.

[0017] As the gelatin, ordinary ones, for example, those derived from animal bones, skins, etc. can be used. The molecular weight of the gelatin may be, for example, 20,000 to 9,000,000.

[0018] Since gelatin is an amphoteric polymer that can become either cationic or anionic, as described later, it is cationized by the action of an acid and then used.

[0019] The origin of the gelatin constituting the microcapsules may be only one kind or two or more kinds. In the case of two or more kinds, their combinations and ratios can be arbitrarily selected.

[0020] <The first anionic polymer> The first anionic polymer is a polymer having an anionic part in its molecule and, together with gelatin, serves as a wall material component of the microcapsules.

[0021] The first anionic polymer is not particularly limited as long as it is a polymer having an anionic group. 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.

[0022] 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.

[0023] 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 )

[0024] 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.

[0025] 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.

[0026] In the microcapsules, the content of the first anionic polymer per 100 parts by mass of gelatin is preferably 10 to 210 parts by mass, for example, it may be any of 10 to 190 parts by mass, 10 to 170 parts by mass, 10 to 150 parts by mass, and 10 to 130 parts by mass, or any of 60 to 210 parts by mass, 110 to 210 parts by mass, and 160 to 210 parts by mass, or any of 60 to 190 parts by mass and 110 to 170 parts by mass. By having the content of the 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.

[0027] <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.

[0028] 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.

[0029] 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.

[0030] Examples of secondary anionic polymers include those similar to the primary anionic polymers described earlier.

[0031] The molecular weight of the second anionic polymer may be the same as that of the second anionic polymer described earlier.

[0032] In the microcapsules, the content of the secondary anionic polymer per 100 parts by mass of gelatin is preferably 2 to 80 parts by mass, for example, 2 to 60 parts by mass, 2 to 40 parts by mass, 2 to 20 parts by mass, and 2 to 10 parts by mass, or 10 to 80 parts by mass, 30 to 80 parts by mass, and 50 to 80 parts by mass, or 10 to 60 parts by mass and 30 to 40 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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 value (parts by mass) of the anionic polymer content (parts by mass) for each type of anionic polymer is calculated by summing them up in descending order of value. The smallest type of anionic polymer whose ratio of this total value to the total anionic polymer content (parts by mass) ([total value (parts by mass) obtained by summing the anionic polymer content (parts by mass) 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.

[0037] 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.

[0038] 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.

[0039] In the microcapsules, the content of the first anionic polymer per 100 parts by mass of the second anionic polymer is preferably 100 to 6000 parts by mass, for example, 1000 to 6000 parts by mass, 2000 to 6000 parts by mass, and 3000 to 6000 parts by mass, or 100 to 4000 parts by mass, 100 to 2000 parts by mass, and 100 to 1000 parts by mass, or 1000 to 4000 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 encapsulation and retention performance of the microcapsules is further improved.

[0040] 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 13 to 290 parts by mass, for example, 13 to 260 parts by mass, 13 to 230 parts by mass, 13 to 210 parts by mass, and 13 to 190 parts by mass, or 70 to 290 parts by mass, 140 to 290 parts by mass, and 210 to 290 parts by mass, or 70 to 260 parts by mass and 140 to 230 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 encapsulation and retention performance of the microcapsules is further improved.

[0041] The aforementioned microcapsules have a smaller average particle size because they contain at least two types of anionic polymers, a first anionic polymer and a second anionic polymer, as their wall material components. For example, if a microcapsule contains only one type of anionic polymer as its 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.

[0042] <Crosslinking agent> The crosslinking agent strengthens the wall material of the microcapsule. It is presumed that the crosslinking agent in the microcapsules contributes to binding the wall material components together. For example, it is presumed that the crosslinking agent interposes between different parts of a single wall material component molecule, linking these parts together by hydrogen bonds, covalent bonds, or electrical attraction, or that it interposes between two wall material component molecules, linking these two molecules together by hydrogen bonds, covalent bonds, or electrical attraction.

[0043] The crosslinking agent may be any known agent and is not particularly limited. Preferred crosslinking agents include, for example, transglutaminase, polyphenols, and glutaraldehyde.

[0044] The aforementioned polyphenols are not particularly limited as long as they have two or more phenolic hydroxyl groups in one molecule, in other words, they have an aromatic ring such as a benzene ring skeleton or a naphthalene ring skeleton, and have two or more hydroxyl groups (-OH) directly bonded to the carbon atoms constituting the ring skeleton of the aromatic ring. Polyphenols include, for example, the amino group (-NH2) or its hydrogen ion adduct (-NH3) in gelatin. + It is presumed that a hydrogen bond is formed between them.

[0045] Examples of the aforementioned polyphenols include tannic acid, catechin, chlorogenic acid, gallic acid, quinic acid, and caffeic acid.

[0046] 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.

[0047] In the microcapsules, the crosslinking agent content is preferably 1 to 60 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 15 to 50 parts by mass or 20 to 40 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.

[0048] Known crosslinking agents include polyvalent metal salts. The polyvalent metal salt is not particularly limited as long as it contains metal ions with a valency of 2 or higher (polyvalent metal ions) as a constituent component. For example, the polyvalent metal salt may be either a polyvalent metal inorganic salt or a polyvalent metal organic salt. The polyvalent metal salt may be either a hydrate or an unhydrated form. However, some of the microcapsules composed of polyvalent metal salts may undergo aggregation or coalescence, and aggregation or coalescence may also occur in the wall material components during the formation process of the microcapsules. In such cases, the particle size of the microcapsules becomes larger. Therefore, it is preferable to use as little polyvalent metal salt as possible. For example, in the microcapsules, the polyvalent metal salt content is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, particularly preferably 1 part by mass or less, and particularly preferably 0 parts by mass (i.e., the microcapsules do not contain polyvalent metal salts), based on 100 parts by mass of the total content of gelatin, the first anionic polymer, and the second anionic polymer.

[0049] The crosslinking agent is preferably one or more selected from the group consisting of transglutaminase, polyphenols, and glutaraldehyde, in that it strengthens the wall material of the microcapsules.

[0050] <Cationic polymers other than gelatin> The wall material within the microcapsule may contain cationic polymers other than gelatin (which may be referred to as "other cationic polymers" in this specification) to the extent that it does not impair the effects of the present invention.

[0051] The other cationic polymers mentioned above are not particularly limited. Examples of other cationic polymers include chitosan, casein, polyethyleneimine, and cation-modified polyvinyl alcohol.

[0052] The other cationic polymers constituting the microcapsules 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.

[0053] 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, even more preferably 1 part by mass or less, and particularly preferably 0 parts by mass (i.e., the microcapsules do not contain the other cationic polymer) per 100 parts by mass of gelatin. When the content of the other cationic polymer is below the upper limit, the average particle size of the microcapsules becomes smaller, the encapsulation and retention performance of the core material of the microcapsules becomes higher, and the stability of the microcapsules is further improved. In addition, the wall material is formed more effectively.

[0054] ◎ Lavender essential oil The aforementioned lavender essential oil is a type of oily component and is the core material in the microcapsule of this embodiment. Lavender essential oil is oily at room temperature.

[0055] In this specification, "room temperature" means a temperature that is neither cooled nor heated, i.e., a normal temperature, such as 15-25°C.

[0056] Examples of lavender essential oils include true lavender essential oil, which mainly consists of linalyl acetate, linalool, ocimene, terpinene, and lavandyl acetate (lavandulyl acetate); lavandin essential oil, which mainly consists of linalyl acetate, linalool, camphor, and 1,8-cineole; and spike lavender essential oil, which mainly consists of linalool, 1,8-cineole, camphor, pinene, and limonene. In addition to the main components mentioned above, lavender essential oil may also contain trace components such as terpinen-4-ol, 3-octanone, and 3-octanyl acetate.

[0057] The lavender essential oil that constitutes the microcapsule (in other words, the lavender essential oil contained within 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.

[0058] In the aforementioned microcapsules, the content of lavender essential oil is preferably 200 to 1200 parts by mass per 100 parts by mass of gelatin, and may be, for example, 300 to 1000 parts by mass or 400 to 800 parts by mass. Microcapsules in which the content of the core material is within this range are of better quality and can be manufactured more easily.

[0059] If the microcapsule's core material has poor encapsulation retention capabilities, lavender essential oil is likely to permeate the wall material and gradually leak out of the microcapsule when it is dry. Also, when the microcapsule is dried, the lavender essential oil is likely to permeate the wall material and vaporize, resulting in the microcapsule no longer containing the lavender essential oil. In contrast, the aforementioned microcapsules have a high capacity to encapsulate and retain the core material, thus suppressing the problems described above.

[0060] ◎ Additives The aforementioned microcapsules contain additives along with lavender essential oil, and even when the microcapsules are dried, they maintain high retention of these core materials (lavender essential oil, additives). This is due to the high stability (the property of maintaining the emulsified state of the emulsified liquid) of the emulsion containing gelatin, water, lavender essential oil, and the aforementioned additives in the manufacturing method described later. The aforementioned additive can be classified as a surfactant.

[0061] In this specification, unless otherwise specified, "additive" means either or both of "polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less" and "sorbitan fatty acid esters with an HLB value of 10.0 or less."

[0062] The additive is one or more selected from the group consisting of polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less and sorbitan fatty acid esters with an HLB value of 10.0 or less. That is, the microcapsule may contain one or more of the polyoxyalkylene alkyl ethers as the additive and not contain the sorbitan fatty acid esters, or it may contain one or more of the sorbitan fatty acid esters and not contain the polyoxyalkylene alkyl ethers, or it may contain one or more of the polyoxyalkylene alkyl ethers and one or more of the sorbitan fatty acid esters. When a microcapsule contains two or more substances selected from the group consisting of the polyoxyalkylene alkyl ether and the sorbitan fatty acid ester, the combination of these two or more substances (more specifically, all combinations of two or more of the polyoxyalkylene alkyl ethers, all combinations of two or more of the sorbitan fatty acid esters, or all combinations of one or more of the polyoxyalkylene alkyl ethers and one or more of the sorbitan fatty acid esters) can be arbitrarily selected depending on the purpose and are not particularly limited.

[0063] In this specification, unless otherwise specified, "HLB value" refers to the value calculated using the Griffin method.

[0064] <Polyoxyalkylene alkyl ether> The polyoxyalkylene alkyl ether may, for example, have a structure in which only one of the hydroxyl groups at either end of the polyalkylene glycol forms an ether (i.e., it may be a polyalkylene glycol monoether), or it may have a structure in which both of the hydroxyl groups at either end of the polyalkylene glycol form an ether (i.e., it may be a polyalkylene glycol diether).

[0065] The terminal monovalent hydrocarbon group forming the ether structure in the polyoxyalkylene alkyl ether may be either a saturated hydrocarbon group or an unsaturated hydrocarbon group. The number of carbon atoms in the hydrocarbon group is not particularly limited and may be, for example, 8 to 20, 12 to 20, or 16 to 20.

[0066] The HLB value of the polyoxyalkylene alkyl ether may be, for example, 9.5 or less, 8.0 or less, 6.5 or less, and 5.0 or less. The lower limit of the HLB value of the polyoxyalkylene alkyl ether is not particularly limited. For example, polyoxyalkylene alkyl ethers with an HLB value of 2.5 or higher are more readily available.

[0067] Examples of the polyoxyalkylene alkyl ether include polyoxyalkylene lauryl ether (also known as polyoxyalkylene dodecyl ether); polyoxyalkylene oleyl cetyl ether such as polyoxyethylene oleyl cetyl ether; and polyoxyalkylene tridecyl ether.

[0068] <Sorbitan fatty acid ester> The sorbitan fatty acid ester may, for example, have a structure in which any (1 to 3) of the four hydroxyl groups in 1,4-sorbitan form a fatty acid ester (it may be any of sorbitan mono fatty acid ester, sorbitan di fatty acid ester, or sorbitan tri fatty acid ester), or it may have a structure in which all (4) hydroxyl groups form a fatty acid ester (it may be sorbitan tetra fatty acid ester). The sorbitan fatty acid ester is preferably one having a structure in which 1 to 3 hydroxyl groups in 1,4-sorbitan form a fatty acid ester. In 1,4-sorbitan, there are three carbon atoms to which a hydroxyl group is bonded that have two other carbon atoms bonded (secondary carbon atoms), and one carbon atom to which a hydroxyl group is bonded that has one other carbon atom bonded (primary carbon atom). Preferably, the sorbitan fatty acid ester has a structure in which a hydroxyl group bonded to at least one carbon atom to which another carbon atom bonded (primary carbon atom) forms a fatty acid ester.

[0069] The fatty acid residue (acyl group) in the sorbitan fatty acid ester may be either a saturated fatty acid residue or an unsaturated fatty acid residue. The number of carbon atoms in the fatty acid residue is not particularly limited and may be, for example, 8 to 20, 12 to 20, or 16 to 20.

[0070] The HLB value of the sorbitan fatty acid ester may be, for example, 9.0 or less, 7.0 or less, 5.0 or less, or 3.0 or less. The lower limit of the HLB value of the sorbitan fatty acid ester is not particularly limited. For example, sorbitan fatty acid esters with an HLB value of 1.0 or higher are more readily available.

[0071] Preferred sorbitan fatty acid esters include, for example, sorbitan oleates such as sorbitan monooleate and sorbitan trioleate.

[0072] In the microcapsules, the content of the additive (the total amount of the polyoxyalkylene alkyl ether and the sorbitan fatty acid ester) is preferably 0.7% by mass or more relative to the lavender essential oil content, and may be, for example, 1.4% by mass or more, 2.1% by mass or more, or 2.8% by mass or more. A content of the additive above the lower limit improves the encapsulation and retention performance of the microcapsules. In the microcapsules, the content of the additive is preferably 10% by mass or less relative to the content of lavender essential oil. By keeping the content of the additive below the upper limit, the decrease in the amount of core material contained in the microcapsules is further suppressed, and the reduction in the effect obtained by containing the core material is further suppressed. The content of the additive may be, for example, 0.7 to 10% by mass, 1.4 to 10% by mass, 2.1 to 10% by mass, and 2.8 to 10% by mass.

[0073] ◎Other ingredients The microcapsules may contain other components that do not fall under any of the following categories: lavender essential oil, polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, or sorbitan fatty acid ester with an HLB value of 10.0 or less, as long as they do not impair the effects of the present invention. The aforementioned other components (other encapsulated components) can be arbitrarily selected depending on the purpose and are not particularly limited.

[0074] The other components contained within the microcapsules 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.

[0075] Other components include, for example, solvents other than water; oily components other than lavender essential oil; and other additives that do not fall under any of the following: water, the solvent, lavender essential oil, the oily component, the polyoxyalkylene alkyl ether (additive), or the sorbitan fatty acid ester (additive).

[0076] <Solvent other than water> Examples of the solvent other than water include solvents contained in the raw materials used for the production of the microcapsules. In this specification, unless otherwise specified, not only components capable of dissolving solutes in a solution but also components serving as dispersion media in a dispersion are referred to as "solvents". The solvent other than water is preferably an organic solvent.

[0077] <Oil component other than lavender essential oil> The oil component other than lavender essential oil (which may be referred to as "other oil component" in this specification) is not particularly limited as long as it is an oil component not corresponding to lavender essential oil. In this specification, the "oil component" means "a component having an SP value (solubility parameter) of 7.0 to 11.0 (cal / cm 3 ) 1 / 2 ". The "SP value" is a calculated value by Fedors' calculation method.

[0078] The other oil components are not particularly limited and can be arbitrarily selected according to the purpose. The oil component is preferably in an oily state at room temperature.

[0079] Examples of the other oil components include animal oils, vegetable oils, mineral oils, etc. Examples of the vegetable oils include 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, olive oil, etc.

[0080] From the viewpoint of its function, examples of the other oil components include fragrances, insect repellents, insecticides, insect repellents, cosmetic materials, deodorants, pharmaceuticals, bactericides, and other chemical reaction agents. The chemical reaction agent is a component that reacts with a specific chemical substance to inhibit the action of this chemical substance and does not fall under any of the fragrances, insect repellents, insecticides, insect repellents, cosmetic materials, deodorants, pharmaceuticals, and bactericides.

[0081] <Other additives> The aforementioned other additives are not particularly limited as long as they are components that do not fall under any of the microcapsule components described above, namely water, the solvent, lavender essential oil, the oily component, the polyoxyalkylene alkyl ether (additive), or the sorbitan fatty acid ester (additive).

[0082] Other additives include, for example, polyoxyalkylene alkyl ethers with an HLB value greater than 10.0; sorbitan fatty acid esters with an HLB value greater than 10.0; and other surfactants that do not fall under either polyoxyalkylene alkyl ethers or sorbitan fatty acid esters.

[0083] If the aforementioned other component is not a solvent other than water, the ratio of the total amount of the aforementioned other component contained in the microcapsule to the total amount of the lavender essential oil contained in the microcapsule, the polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, and the sorbitan fatty acid ester with an HLB value of 10.0 or less contained in the microcapsule ([Total amount of the aforementioned other component contained in the microcapsule (parts by mass)] / ([Amount of lavender essential oil contained in the microcapsule (parts by mass)] + [Amount of polyoxyalkylene alkyl ether with an HLB value of 10.0 or less contained in the microcapsule (parts by mass)] + [Amount of sorbitan fatty acid ester with an HLB value of 10.0 or less contained in the microcapsule (parts by mass)] × 100) is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass, i.e., not containing the aforementioned other component.

[0084] If the other component is a solvent other than water, the amount of the solvent contained within the microcapsule can be appropriately adjusted depending on the type of solvent.

[0085] ◎Average particle size of microcapsules The average particle size of the microcapsules is 30 μm or less, indicating that the microcapsules have a small particle size. The average particle size of the microcapsules may be, for example, 28 μm or less, 26 μm or less, 24 μm or less, or 22 μm or less. For example, microcapsules with a small average particle size are difficult to see with the naked eye, so their applications are not limited.

[0086] The lower limit of the average particle diameter of the microcapsules is not particularly limited. For example, in terms of ease of manufacturing the microcapsules, the average particle diameter of the microcapsules may be 8 μm or more, 13 μm or more, or 18 μm or more.

[0087] The average particle size of the microcapsules can be appropriately adjusted within a range set by arbitrarily combining any of the upper and lower limits described above. For example, in one embodiment, the average particle size of the microcapsules may be any of 8-30 μm, 8-28 μm, 8-26 μm, 8-24 μm, and 8-22 μm or less, or any of 13-30 μm, 13-28 μm, 13-26 μm, 13-24 μm, and 13-22 μm or less, or any of 18-30 μm, 18-28 μm, 18-26 μm, 18-24 μm, and 18-22 μm or less.

[0088] In this specification, unless otherwise specified, "average particle size" refers to the median diameter of the volume particle size distribution measured using a particle size distribution analyzer.

[0089] In the aforementioned microcapsules, no highly toxic substances are used as raw materials for the manufacture of the wall material, and the microcapsules are highly safe for living organisms. Furthermore, the microcapsules can be easily made biodegradable by selecting appropriate materials as both the raw material for the wall material and the core material.

[0090] The aforementioned microcapsules can be designed to have a sustained-release property, gradually releasing the encapsulated core substance (especially lavender essential oil) to the outside over time. Such microcapsules can sustain the effects of the core substance over a long period of time. For example, the microcapsules composed of gelatin, a primary anionic polymer, a secondary anionic polymer, a crosslinking agent, lavender essential oil, a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, and a sorbitan fatty acid ester with an HLB value of 10.0 or less, are preferred as having higher sustained-release properties.

[0091] 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.

[0092] <<Method for manufacturing microcapsules>> A method for producing microcapsules according to one embodiment of the present invention comprises the steps of preparing a mixture (z) by mixing lavender essential oil with one or more selected from the group consisting of polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less and sorbitan fatty acid esters with an HLB value of 10.0 or less (this may be referred to as the "first mixing step" in this specification), A step of preparing an emulsion by mixing gelatin and the aforementioned mixture (z) in the presence of water (this may be referred to as the "emulsification step" in this specification), A step of preparing a mixture (a) 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 "emulsion mixing step" in this specification), The process involves mixing the aforementioned mixture (a) with an acid to produce an acidic mixture (b) (which may be referred to as the "acidification process" in this specification), The process involves cooling the aforementioned mixture (b) until its temperature is 10°C or lower (this may be referred to as the "cooling process" in this specification), A step of preparing a mixture (c) by mixing the cooled mixture (b) with a crosslinking agent (this may be referred to as the "crosslinking agent mixing step" in this specification), The process includes a step of mixing the aforementioned mixture (c) with a base to produce an aqueous dispersion of microcapsules with adjusted pH (this may be referred to as the "base mixing step" in this specification).

[0093] The above-mentioned manufacturing method 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.

[0094] <First mixing process> In the first mixing step, a mixture (z) is prepared by mixing lavender essential oil with one or more additives selected from the group consisting of polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less and sorbitan fatty acid esters with an HLB value of 10.0 or less. The mixture (z) contains lavender essential oil and further contains either or both (additives) of a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less and / or a sorbitan fatty acid ester with an HLB value of 10.0 or less.

[0095] The lavender essential oil and the additives (the polyoxyalkylene alkyl ether and the sorbitan fatty acid ester) used in the first mixing step have been described previously, and a detailed explanation is omitted here.

[0096] The lavender essential oil and additives used in the first mixing step 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.

[0097] In the first mixing step, the amount of the additive used (the total amount of the polyoxyalkylene alkyl ether and the sorbitan fatty acid ester) is preferably 0.7% by mass or more relative to the amount of lavender essential oil used, and may be, for example, 1.4% by mass or more, 2.1% by mass or more, or 2.8% by mass or more. By having the amount of the additive used be above the lower limit, the stability of the emulsion will be further enhanced in the emulsification step described later. In the aforementioned microcapsules, the amount of additive used is preferably 10% by mass or less relative to the amount of lavender essential oil used. By keeping the amount of additive below the upper limit, the decrease in the amount of core material contained in the microcapsules is further suppressed, and the reduction in the effect obtained by containing the core material is further suppressed. The amount of additive used may be, for example, 0.7 to 10% by mass, 1.4 to 10% by mass, 2.1 to 10% by mass, and 2.8 to 10% by mass.

[0098] In the first mixing step, other components (which may be referred to as "other component (01)" in this specification) that do not fall under either the lavender essential oil or the aforementioned additives may be mixed, as long as they do not impair the effects of the present invention.

[0099] The aforementioned other component (01) is not particularly limited and can be arbitrarily selected depending on the purpose. Other components (01) include, for example, oily components other than lavender essential oil from the other components described above, and the other additives mentioned above.

[0100] The other components (01) used in the first mixing step 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.

[0101] In the first mixing step, the amount of the other component (01) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (01). Typically, in the first mixing step, the ratio of the amount of other components (01) used to the total amount of lavender essential oil, polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, and sorbitan fatty acid ester with an HLB value of 10.0 or less ([amount of other components (01)] / ([amount of lavender essential oil] + [amount of polyoxyalkylene alkyl ether with an HLB value of 10.0 or less] + [amount of sorbitan fatty acid ester with an HLB value of 10.0 or less]) × 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 encapsulation retention performance can be obtained.

[0102] In the first mixing step, the mixing of lavender essential oil, the additive, and other components (01) as needed is preferably carried out at room temperature, and more preferably at a temperature of 18 to 30°C.

[0103] The method for mixing lavender essential oil, the additive, and other components (01) as needed 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.

[0104] In the first mixing step, when adding the remaining components to any of the components (01) of lavender essential oil, the additive, and other components (01) 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.

[0105] In the first mixing step, after blending all the components (lavender essential oil, the aforementioned additive, and other components (01) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0106] In the first mixing step, it is preferable to prepare a mixed solution (z) by adding the additive to lavender essential oil.

[0107] <Emulsification process> In the emulsification step, an emulsion is prepared by mixing gelatin and the mixed liquid (z) in the presence of water. The emulsified liquid contains gelatin, water, and lavender essential oil, and further contains either or both (additives) of a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, and a sorbitan fatty acid ester with an HLB value of 10.0 or less. By using the aforementioned additive, the emulsion obtained in the emulsification process has high stability (the property of maintaining the emulsified state of the emulsion).

[0108] The gelatin used in the emulsification process is the one described above, and a detailed explanation will be omitted here.

[0109] The gelatin used in the emulsification process 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.

[0110] In the emulsification process, for example, gelatin, water, and a mixture (z) may be combined, or a gelatin aqueous solution and a mixture (z) may be combined. When a gelatin aqueous solution is combined, additional water may be added in addition to the water in the gelatin aqueous solution, or it may not be added.

[0111] In the emulsification process, the order in which gelatin, water, and the mixture (z) are added is not particularly limited, nor is the order in which the gelatin aqueous solution, the mixture (z), and additional water as needed are added.

[0112] In the emulsification process, it is preferable to combine the gelatin aqueous solution, the mixed solution (z), and water separately as needed. By doing so, an emulsified solution with higher uniformity can be produced.

[0113] The gelatin concentration of the gelatin aqueous solution used in the emulsification process is preferably 2 to 20% by mass, and more preferably 3 to 10% by mass.

[0114] 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 principle applies to the concentrations of aqueous solutions of other components.

[0115] Both the water used in the emulsification process and the gelatin aqueous solution may be heated. By heating the water or the gelatin aqueous solution, a more uniform emulsified solution 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 the gelatin or additives.

[0116] When the gelatin aqueous solution and the mixture (z) are combined, the mixture (z) may be added to the gelatin aqueous solution, or the gelatin aqueous solution may be added to the mixture (z). When the mixture (z) is added to the gelatin aqueous solution, the mixture (z) may be added to the gelatin aqueous solution all at once, or added in portions or dropwise. When the gelatin aqueous solution is added to the mixture (z), the gelatin aqueous solution may be added to the mixture (z) all at once, or dropwise.

[0117] In the emulsification process, 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 the production of a more uniform emulsified solution. When the amount of water used is below the upper limit, excessive water use is suppressed. Here, the amount of water used is the amount of water when gelatin, water, and mixed solution (z) are combined; the amount of water in the gelatin aqueous solution when gelatin aqueous solution and mixed solution (z) are combined without adding water separately; and the total amount of water in the gelatin aqueous solution and the separately added water when gelatin aqueous solution, mixed solution (z), and water are combined.

[0118] In the emulsification process, the amount of mixed solution (z) used is preferably 2 to 10 times the amount of gelatin used, and more preferably 4 to 8 times. By using mixed solution (z) within this range, microcapsules of better quality can be manufactured more easily.

[0119] In the emulsification process, other components (which may be referred to as "other components (02)" in this specification) that do not fall under any of the following categories: gelatin, water, lavender essential oil, or the aforementioned additives, may be mixed in, to the extent that they do not impair the effects of the present invention.

[0120] The aforementioned other component (02) is not particularly limited and can be arbitrarily selected depending on the purpose. The other components (02) used in the emulsification process 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.

[0121] In the emulsification process, the amount of the other component (02) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (02). Typically, in the emulsification process, the ratio of the amount of other components (02) used to the total amount of gelatin, water, and mixed solution (z) used ([amount of other components (02)] / ([amount of gelatin]+[amount of water]+[amount of mixed solution (z)])×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 encapsulation retention performance can be obtained. Here, water usage is as explained earlier.

[0122] In the emulsification process, the mixing of gelatin, the mixed liquid (z), and optionally other components (02) 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.

[0123] The method for mixing gelatin, the mixed liquid (z), and optionally other components (02) 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 rotation speed of the stirring means may be, for example, 1500 to 4500 rpm or 2500 to 3500 rpm, but is not limited thereto. For example, such a rotation speed is particularly suitable when the amount of gelatin used is 5 to 15 g. However, the amount of gelatin used is not limited thereto. Furthermore, it is preferable to apply such a rotation speed at least in the present time of this process, after the gelatin, the mixed liquid (z), and any other components (02) have all been blended in the presence of water.

[0124] In the emulsification process, when adding the remaining components to any of the components (gelatin or gelatin aqueous solution, mixed solution (z), water as needed, and other components (02) 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.

[0125] In the emulsification process, after blending all the components (gelatin or gelatin aqueous solution, mixed solution (z), water as needed, and other components (02) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0126] In the emulsification process, it is preferable to prepare the emulsion by adding the mixed solution (z) alone to a heated gelatin aqueous solution, or the emulsion may be prepared by adding the mixed solution (z) at room temperature alone to a heated gelatin aqueous solution.

[0127] <Emulsion mixing process> In the emulsifier mixing step, a mixture (a) is prepared by mixing a first anionic polymer, a second anionic polymer, and the emulsifier in the presence of water. The aforementioned mixture (a) contains a first anionic polymer, a second anionic polymer, gelatin, water, and lavender essential oil, and further contains either or both (additives) a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, and a sorbitan fatty acid ester with an HLB value of 10.0 or less.

[0128] In the emulsion mixing process, by using a first anionic polymer and a second anionic polymer in combination, aggregation or coalescence of the microcapsules themselves, and aggregation or coalescence of the wall material components in the process of microcapsule formation are suppressed in subsequent processes.

[0129] The first and second anionic polymers used in the emulsion mixing process have been described previously, and a detailed explanation of them will be omitted here.

[0130] The first anionic polymer and the second anionic polymer used in the emulsion mixing step may be one type each, or two or more types each. If there are two or more types, their combination and ratio can be arbitrarily selected. The classification method for first- and second-anionic polymers is as explained above.

[0131] In the emulsion mixing step, for example, a first anionic polymer, a second anionic polymer, water, and the emulsion may be blended; an aqueous solution of the first anionic polymer, the second anionic polymer, and the emulsion may be blended; a first anionic polymer, an aqueous solution of the second anionic polymer, and the emulsion may be blended; or an aqueous solution of the first anionic polymer, an aqueous solution of the second anionic polymer, and the emulsion may be blended. When an aqueous solution of the first anionic polymer or an aqueous solution of the second anionic polymer is blended, water may be added separately in addition to the water in the aqueous solution of the first anionic polymer or the aqueous solution of the second anionic polymer, or it may not be added.

[0132] In the emulsifier mixing step, the order in which the first anionic polymer or its aqueous solution, the second anionic polymer or its aqueous solution, the emulsifier, and water as needed are blended is not particularly limited.

[0133] In the emulsion mixing step, it is preferable to combine the first anionic polymer aqueous solution, the second anionic polymer aqueous solution, the emulsion, and water as needed. By doing so, a mixture (a) with higher uniformity can be produced.

[0134] The concentration of the first anionic polymer in the aqueous solution of the first anionic polymer used in the emulsion mixing step is preferably 3 to 20% by mass, and more preferably 5 to 12% by mass.

[0135] The concentration of the second anionic polymer in the aqueous solution of the second anionic polymer used in the emulsion mixing step is preferably 3 to 20% by mass, and more preferably 5 to 12% by mass.

[0136] The water, the first anionic polymer aqueous solution, and the second anionic polymer aqueous solution used in the emulsification mixing step may all be heated. By heating the water, the first anionic polymer aqueous solution, or the second anionic polymer aqueous solution, a mixture (a) with higher uniformity may be produced. The heating temperature for water, the aqueous solution of the first anionic polymer, and the aqueous solution of the second anionic polymer is preferably 40 to 75°C, and more preferably 40 to 60°C. A heating temperature above the lower limit allows for 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 the first anionic polymer, the second anionic polymer, gelatin, lavender essential oil, or the additives. When preparing the mixture (a), water and either the first anionic polymer aqueous solution or the second anionic polymer aqueous solution may be left at room temperature without heating.

[0137] When a first anionic polymer aqueous solution or a second anionic polymer aqueous solution is used, the target substance may be added to the first anionic polymer aqueous solution or the second anionic polymer aqueous solution, or the first anionic polymer aqueous solution or the second anionic polymer aqueous solution may be added to the target substance. When a target substance is added to the first anionic polymer aqueous solution or the second anionic polymer aqueous solution, the target substance may be added to the first anionic polymer aqueous solution or the second anionic polymer aqueous solution all at once, or added in stages or dropwise. When a first anionic polymer aqueous solution or a second anionic polymer aqueous solution is added to the target substance, the first anionic polymer aqueous solution or the second anionic polymer aqueous solution may be added to the target substance all at once, or added dropwise.

[0138] In the emulsifier mixing step, the amount of water used is preferably 4 to 16 times the total amount of water used for the first anionic polymer and the second anionic polymer, and more preferably 7 to 13 times the total amount of water used. 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 (a). When the amount of water used is below the upper limit, excessive use of water is suppressed.

[0139] Here, the amount of water used refers to the amount of water used when the first anionic polymer, the second anionic polymer, water, and the emulsion are combined. Furthermore, if the first anionic polymer aqueous solution, the second anionic polymer, and the emulsion are combined, and no additional water is added, 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, the emulsion, 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 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, the emulsifier, 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 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, the emulsifier, 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.

[0140] In the emulsification liquid mixing step, the amount of the first anionic polymer used is preferably 0.1 to 2.1 times the mass of the amount of gelatin in the emulsification liquid. For example, it may be 0.1 to 1.9 times, 0.1 to 1.7 times, 0.1 to 1.5 times, and 0.1 to 1.3 times, or 0.6 to 2.1 times, 1.1 to 2.1 times, and 1.6 to 2.1 times, or 0.6 to 1.9 times and 1.1 to 1.7 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.

[0141] In the emulsification liquid mixing step, the amount of secondary anionic polymer used is preferably 0.02 to 0.8 times the mass of the amount of gelatin in the emulsification liquid. For example, it may be 0.02 to 0.6 times, 0.02 to 0.4 times, 0.02 to 0.2 times, and 0.02 to 0.1 times, or 0.1 to 0.8 times, 0.3 to 0.8 times, and 0.5 to 0.8 times, or 0.1 to 0.6 times and 0.3 to 0.4 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.

[0142] In the emulsion mixing step, the amount of the first anionic polymer used is preferably 1 to 60 times the mass of the amount of the second anionic polymer used, for example, it may be 10 to 60 times, 20 to 60 times, or 30 to 60 times, or 1 to 40 times, 1 to 20 times, or 1 to 10 times, or 10 to 40 times. If the amount of the first anionic polymer used is above the lower limit, the yield of microcapsules is further improved. If the amount of the first anionic polymer used is below the upper limit, the encapsulation and retention performance of the microcapsules is further improved.

[0143] In the emulsifier mixing step, the total amount of the first anionic polymer and the second anionic polymer used is preferably 0.13 to 2.9 times the amount of gelatin in the emulsifier, for example, it may be 0.13 to 2.6 times, 0.13 to 2.3 times, 0.13 to 2.1 times, and 0.13 to 1.9 times, or 0.7 to 2.9 times, 1.4 to 2.9 times, and 2.1 to 2.9 times, or 0.7 to 2.6 times and 1.4 to 2.3 times. When the total amount used is above the lower limit, the yield of microcapsules is further improved. When the total amount used is below the upper limit, the encapsulation and retention performance of the microcapsules is further improved.

[0144] In the emulsified liquid mixing step, gelatin, the first anionic polymer, the second anionic polymer, water, lavender essential oil, and other components that do not fall under any of the above additives (which may be referred to as "other components (03)" in this specification) may be mixed, to the extent that they do not impair the effects of the present invention.

[0145] The aforementioned other component (03) is not particularly limited and can be arbitrarily selected depending on the purpose. The other components (03) used in the emulsifier mixing step 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.

[0146] In the emulsifier mixing step, the amount of the other component (03) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (03). Typically, in the emulsion mixing step, the ratio of the amount of other components (03) used to the total amount of the first anionic polymer, the second anionic polymer, water, and the emulsion ([amount of other components (03)] / ([amount of first anionic polymer]+[amount of second anionic polymer]+[amount of water]+[amount of emulsion])×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 encapsulation retention performance can be obtained. Here, water usage is as explained earlier.

[0147] In the emulsion mixing step, the mixing of the first anionic polymer, the second anionic polymer, the emulsion, and optionally other components (03) in the presence of water is preferably carried out under temperature conditions of 30 to 75°C, and more preferably under temperature conditions of 40 to 60°C.

[0148] The method for mixing the first anionic polymer, the second anionic polymer, the emulsion, and optionally other components (03) in the presence of water is not particularly limited and may be the same as, or different from, the method for mixing gelatin, the mixture (z), and optionally other components (02) in the presence of water in the emulsification step described above.

[0149] In the emulsifier mixing step, when adding the remaining components to any of the following additives: the first anionic polymer or its aqueous solution, the second anionic polymer or its aqueous solution, the emulsifier, water as needed, and other components (03) 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 components have been combined.

[0150] In the emulsifier mixing step, after mixing all the components (first anionic polymer or aqueous solution thereof, second anionic polymer or aqueous solution thereof, the emulsifier, water as needed, and other components (03) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0151] In the emulsion mixing step, it is preferable to prepare a mixture (a) by, for example, adding the emulsion alone to a heated first anionic polymer aqueous solution, and then adding a heated second anionic polymer aqueous solution to the resulting mixture. Alternatively, a mixture (a) may be prepared by adding the emulsion at 25°C or higher alone to a heated first anionic polymer aqueous solution, and then adding a heated second anionic polymer aqueous solution to the resulting mixture.

[0152] <Acidification process> In the acidification step, an acidic mixture (b) is prepared by mixing the mixture (a) with an acid. The gelatin in mixture (a) 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 mixture (b) 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 (b) contains gelatin (cationic polymer), a first anionic polymer, a second anionic polymer, water, and lavender essential oil, and further contains either or both (additives) of a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, and a sorbitan fatty acid ester with an HLB value of 10.0 or less.

[0153] The acid used in the acidification process 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).

[0154] The acid used in the acidification process 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.

[0155] In the acidification process, 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 (b).

[0156] The concentration of the acid in the acid aqueous solution used in the acidification process 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.

[0157] When the aforementioned acidic aqueous solution is combined with the mixed solution (a), it is preferable to add the acidic aqueous solution to the mixed solution (a), and the acidic aqueous solution may be added to the mixed solution (a) 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 (a). The acid may be added to the mixture (a) all at once, or it may be added dropwise or in portions.

[0158] In the acidification step, other components (which may be referred to as "other components (04)" in this specification) that do not fall under any of the following categories: gelatin, first anionic polymer, second anionic polymer, lavender essential oil, the aforementioned additives, and acid, may be mixed in, to the extent that they do not impair the effects of the present invention.

[0159] The aforementioned other component (04) 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, water may be added separately as the other component (04), regardless of whether the acid is added alone or as an aqueous solution. In this specification, water as the other component (04) may be referred to as "water (04)".

[0160] When using water (04), for example, an acidic mixture (b) can be prepared by mixing the mixture (a) with an acid or an acidic aqueous solution, and then another acidic mixture (b) can be prepared by mixing the acidic mixture (b) with water (04). Furthermore, when using water (04), for example, the mixture (a) can be diluted by mixing it with water (04), and then an acidic mixture (b) can be prepared by mixing this diluted mixture (a) with an acid or an acidic aqueous solution.

[0161] The other components (04) used in the acidification process 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 acidification process, the amount of the other component (04) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (04). For example, if the other component (04) is a component other than water, in the acidification step, the ratio of the amount of the other component (04) used to the total amount of the mixture (a) and the acid used ([amount of other component (04) used] / ([amount of mixture (a) 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 encapsulation retention performance 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.

[0163] On the other hand, when the other component (04) is water, in the acidification step, the ratio of the amount of water (04) used to the total amount of the mixture (a) and the acid or acidic aqueous solution used ([amount of water (04) used] / ([amount of mixture (a) 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, or 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.

[0164] In the acidification process, when mixing the mixed solution (a), an acid or an aqueous acid solution, and other components (04) 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 (04), it is preferable to mix in water (04) that has been adjusted (heated) to such a temperature.

[0165] The method of mixing the mixture (a), the acid or acidic aqueous solution, and optionally other components (04) is not particularly limited and may be the same as or different from the method of mixing gelatin, the mixture (z), and optionally other components (02) in the presence of water in the emulsification step described above.

[0166] In the acidification process, when adding the remaining components to the mixture (a), the acid or acidic aqueous solution, and any other components (04) 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.

[0167] In the acidification step, after mixing all the components (mixture (a), acid or acidic aqueous solution, and other components (04) as needed), the time for stirring the resulting mixture may be, for example, 1 to 10 minutes.

[0168] In the acidification step, it is preferable to prepare an acidic mixture (b) by adding or dropwise adding an acidic aqueous solution to the mixture (a), and it is more preferable to prepare an acidic mixture (b) by dropwise adding an acidic aqueous solution to the mixture (a). When using water (04), it is preferable to prepare an acidic mixture (b) by adding or dropping water (04) onto the object.

[0169] From the start to the end of the acidification process, the minimum pH value of the liquid containing gelatin, the first anionic polymer, and the second anionic polymer 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 and second anionic polymers, 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 aforementioned liquid may be, for example, the mixture (b), or it may be a mixture in an intermediate stage before obtaining the mixture (b).

[0170] <Cooling process> In the cooling step, the mixed liquid (b) is cooled until its temperature is 10°C or lower. Cooling the mixture (b) promotes the precipitation of the wall material containing lavender essential oil and the additive within the mixture (b).

[0171] The temperature of the mixed liquid (b) 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 (b). A temperature above the lower limit suppresses excessive cooling of the mixed liquid (b).

[0172] The cooling rate of the mixture (b) is not particularly limited, but is preferably 0.2 to 2.0°C / min, and more preferably 0.3 to 1.0°C / min. A cooling rate within this range allows for a more pronounced cooling effect of the mixture (b).

[0173] <Crosslinking agent mixing process> In the crosslinking agent mixing step, a mixed liquid (c) is prepared by mixing the cooled mixed liquid (b) with the crosslinking agent. By performing this process, microcapsules with a small average particle size and high core material retention performance even in a dried state can be obtained as an aqueous dispersion. In the mixture (c), 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 mixture (c) contains the target microcapsules.

[0174] The crosslinking agent used in the crosslinking agent mixing process is the one described earlier, and a detailed explanation will be omitted here.

[0175] The crosslinking agent used in the crosslinking agent mixing step is preferably one or more selected from the group consisting of transglutaminase, polyphenols, and glutaraldehyde.

[0176] The crosslinking agent used in the crosslinking agent mixing process 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.

[0177] In the crosslinking agent mixing process, depending on the type of crosslinking agent, it 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.

[0178] When combining the crosslinking agent aqueous solution with the mixed solution (b), it is preferable to add the crosslinking agent aqueous solution to the mixed solution (b), and the crosslinking agent aqueous solution may be added to the mixed solution (b) 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 (b), and the crosslinking agent may be added to the mixture (b) all at once or in stages.

[0179] In the crosslinking agent mixing step, the amount of crosslinking agent used is preferably 0.01 to 0.6 times the mass of the total amount of gelatin, the first anionic polymer, and the second anionic polymer in the mixture (b), for example, it may be 0.15 to 0.5 times the mass or 0.2 to 0.4 times the mass. If the amount of crosslinking agent used is above the lower limit, the wall material of the microcapsule becomes stronger. If the amount of crosslinking agent used is below the upper limit, excessive use of the crosslinking agent is suppressed.

[0180] In the crosslinking agent mixing step, other components (which may be referred to as "other components (05)" in this specification) that do not fall under any of the following categories: gelatin, first anionic polymer, second anionic polymer, lavender essential oil, the aforementioned additives, acid, and crosslinking agent, may be mixed, provided that the effects of the present invention are not impaired.

[0181] The aforementioned other components (05) are not particularly limited and can be arbitrarily selected depending on the purpose. The other components (05) used in the crosslinking agent mixing process 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.

[0182] Examples of the other component (05) include water.

[0183] In the crosslinking agent mixing process, the amount of the other component (05) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (05).

[0184] When the other component (05) is a component other than water, the ratio of the amount of other component (05) used to the total amount of the mixture (b) and the crosslinking agent used in the crosslinking agent mixing step ([amount of other component (05) used] / ([amount of mixture (b) 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 encapsulation retention performance can be obtained.

[0185] In the crosslinking agent mixing step, when mixing the mixed solution (b), the crosslinking agent or an aqueous solution of the crosslinking agent, and other components (05) 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 may or may not coincide with the temperature range of the mixed liquid (b) in the cooling step.

[0186] The method of mixing the mixture (b), the crosslinking agent or aqueous solution of the crosslinking agent, and other components (05) as needed is not particularly limited and may be the same as or different from the method of mixing gelatin, the mixture (z), and other components (02) as needed in the presence of water in the emulsification step described above.

[0187] In the crosslinking agent mixing step, when adding the remaining components to the mixture (b), the crosslinking agent or aqueous crosslinking agent solution, and any other components (05) 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.

[0188] In the crosslinking agent mixing step, after mixing all the components (mixture (b), the crosslinking agent or aqueous crosslinking agent solution, and other components (05) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0189] In the crosslinking agent mixing step, after all components (mixture (b), crosslinking agent or aqueous crosslinking agent solution, and other components (05) as needed) are combined, the temperature of the resulting mixture when it is stirred is preferably 0 to 10°C, and more preferably 2 to 9°C.

[0190] <Base mixing process> In the base mixing step, the mixture (c) and the base are mixed to produce an aqueous dispersion of microcapsules with adjusted pH. The microcapsules obtained in the base mixing step exhibit greater structural stability in the aqueous dispersion.

[0191] The pH of the aqueous dispersion of microcapsules obtained in the base mixing step can be arbitrarily selected depending on the purpose and is not particularly limited. It may be 4 to 9.2, preferably 4 to 6.8, and for example, 5 to 6.5.

[0192] The base used in the base mixing step 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).

[0193] The bases used in the base mixing step 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.

[0194] In the base mixing step, the base may be mixed individually or as an aqueous solution. Using an aqueous base solution makes it easier to prepare a pH-adjusted mixture (c).

[0195] The concentration of the base in the aqueous base solution used in the base mixing step can be adjusted as appropriate depending on the type of base, but it is preferably 10 to 30% by mass, and more preferably 15 to 25% by mass.

[0196] When preparing the aforementioned aqueous base solution and mixed solution (c), it is preferable to add the aqueous base solution to mixed solution (c), and the aqueous base solution may be added to mixed solution (c) 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 (c), and the base may be added to the mixture (c) all at once, or added dropwise or in portions.

[0197] In the base mixing step, the mixing of the mixture (c) 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.

[0198] The method for mixing the mixture (c) 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 described above, in which gelatin, the mixture (z), and other components (02) as needed are mixed in the presence of water.

[0199] In the base mixing step, when adding the remaining component to the mixture (c) and either the base or the aqueous base solution, the remaining component may be added while stirring the target material, or the remaining component may be added without stirring the target material, and the mixture may be stirred after all components have been combined.

[0200] In the base mixing step, it is preferable to prepare an aqueous dispersion of microcapsules by adding or dropping an aqueous base solution to the mixture (c), and it is more preferable to prepare an aqueous dispersion of microcapsules by dropping an aqueous base solution to the mixture (c).

[0201] When the crosslinking agent is an enzyme such as transglutaminase, and especially when it is transglutaminase, in the base mixing step, after mixing all the components (mixture (b) and the base or base aqueous solution), it is preferable to raise the temperature of the resulting aqueous dispersion and stir it at 15 to 35°C. The time for stirring the aqueous dispersion at this temperature is preferably 2 to 6 hours. By stirring the aqueous dispersion under these conditions, the enzyme (crosslinking) reaction can be carried out sufficiently. After stirring under these conditions, it is preferable to further raise the temperature of the aqueous dispersion and stir it at 70 to 75°C. The time for stirring the aqueous dispersion at this temperature is preferably 15 to 20 minutes. By further stirring the aqueous dispersion under these temperature conditions, any excess enzyme can be sufficiently inactivated.

[0202] <Other processes> The above-mentioned manufacturing method may include other steps that do not fall under any of the above-described first mixing step, emulsification step, emulsion mixing step, acidification step, cooling step, crosslinking agent mixing step, or base mixing step, as long as they do not impair the effects of the present invention. The types of other processes, the number of other processes, and the timing of performing these other processes can be arbitrarily selected according to the purpose and are not particularly limited.

[0203] [Additional mixing process] Other steps include, for example, a step of preparing a mixture (d) by mixing the cooled mixture (b) with the second anionic polymer between the cooling step and the crosslinking agent mixing step (this may be referred to as an "additional mixing step" in this specification). Thus, in the above manufacturing method, the second anionic polymer may be added and mixed to the cooled mixture (b). In other words, the manufacturing method includes a cooling step, An additional mixing step is performed to prepare a mixed solution (d) by mixing the cooled mixed solution (b) with the second anionic polymer. A crosslinking agent mixing step is performed to prepare a mixed solution (c) by mixing the aforementioned mixed solution (d) with a crosslinking agent. The method may include a base mixing step, in which the aforementioned mixture (c) and a base are mixed to produce an aqueous dispersion of microcapsules with adjusted pH.

[0204] By performing an additional mixing step, the aggregation or coalescence of the microcapsules themselves and the aggregation or coalescence of the wall material components during the microcapsule formation process can be highly suppressed in subsequent steps, potentially resulting in microcapsules with a smaller average particle size. The additional mixing step is preferably performed when using crosslinking agents other than transglutaminase (enzyme), such as polyphenols or glutaraldehyde.

[0205] The mixture (d) contains gelatin (cationic polymer), a primary anionic polymer, a secondary anionic polymer, water, and lavender essential oil, and further contains either or both (additives) of a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, and a sorbitan fatty acid ester with an HLB value of 10.0 or less.

[0206] The second anionic polymer used in the additional mixing step is the one described earlier, and a detailed explanation of it will be omitted here.

[0207] The second anionic polymer used in the additional mixing step may be the same as or different from the second anionic polymer used in the emulsion mixing step.

[0208] The second anionic polymer used in the additional mixing step 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] The mass ratio of [amount of second anionic polymer used in the emulsion mixing step (parts by mass)] to [amount of second anionic polymer used in the additional mixing step (parts by mass)] is preferably 5:95 to 95:5, and may be any of 75:25 to 25:75, 68:32 to 32:68, 61:39 to 39:61, and 55:45 to 45:55, or any of 5:95 to 55:45, 5:95 to 25:75, and 5:95 to 15:85. By having the mass ratio within this range, microcapsules with a smaller average particle size can be obtained.

[0210] The total amount of the second anionic polymer used in the additional mixing step and the emulsifier mixing step (the sum of the amount of the second anionic polymer used in the additional mixing step and the amount of the second anionic polymer used in the emulsifier mixing step) is preferably 0.03 to 0.85 times the amount of gelatin in the mixture (b). 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, and microcapsules with a smaller average particle size can be obtained.

[0211] The amount of the first anionic polymer used in the emulsion mixing step is preferably 0.5 to 55 times the total amount of the second anionic polymer used in the additional mixing step and the emulsion mixing step (the sum of the amount of the second anionic polymer used in the additional mixing step and the amount of the second anionic polymer used in the emulsion mixing step). For example, it may be 5 to 55 times, 15 to 55 times, or 25 to 55 times, or 0.5 to 35 times, 0.5 to 20 times, or 0.5 to 10 times, or 5 to 35 times. 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 encapsulation and retention performance of the microcapsules is further improved.

[0212] The total amount of the first anionic polymer used in the emulsion mixing step and the total amount of the second anionic polymer used in the additional mixing step and the emulsion mixing step (the total amount of the first anionic polymer used in the emulsion mixing step, the amount of the second anionic polymer used in the additional mixing step, and the total amount of the second anionic polymer used in the emulsion mixing step) is preferably 0.2 to 3.4 times the amount of gelatin in the mixture (b). 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 encapsulation and retention performance of the microcapsules is further improved.

[0213] In the additional mixing step, for example, the second anionic polymer and the cooled mixture (b) may be blended, or the aqueous solution of the second anionic polymer and the cooled mixture (b) 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.

[0214] In the additional mixing step, the order in which the second anionic polymer or its aqueous solution, the cooled mixture (b), and water as needed are added is not particularly limited.

[0215] In the additional mixing step, it is preferable to combine the aqueous solution of the second anionic polymer, the cooled mixture (b), and water separately as needed. This allows for the production of a mixture (d) with higher uniformity.

[0216] The concentration of the second anionic polymer in the aqueous solution of the second anionic polymer used in the additional mixing step is preferably 3 to 20% by mass, and more preferably 5 to 12% by mass.

[0217] 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.

[0218] In the additional mixing step, other components (which may be referred to as "other components (06)" in this specification) that do not fall under any of the following categories: gelatin, first anionic polymer, second anionic polymer, water, lavender essential oil, the aforementioned additives, and acid, may be mixed, provided that they do not impair the effects of the present invention.

[0219] The aforementioned other component (06) is not particularly limited and can be arbitrarily selected depending on the purpose. The other components (06) used in the additional mixing step 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.

[0220] In the additional mixing step, the amount of the other component (06) used is not particularly limited and can be adjusted as appropriate depending on the type of the other component (06). Typically, in the additional mixing step, the ratio of the amount of other component (06) used to the total amount of the second anionic polymer, water, and the cooled mixture (b) used ([amount of other component (06)] / ([amount of second anionic polymer]+[amount of water]+[amount of cooled mixture (b)])×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 encapsulation retention performance can be obtained.

[0221] Here, the amount of water used is zero if the second anionic polymer and the cooled mixture (b) are combined, and no additional water is added. Furthermore, when mixing the second anionic polymer, the cooled mixture (b), and water separately, this is the amount of water. Furthermore, if the aqueous solution of the second anionic polymer and the cooled mixture (b) are combined, and no additional water is added, the amount of water is the amount of water in the aqueous solution of the second anionic polymer. Furthermore, when a second anionic polymer aqueous solution, the cooled mixture (b), 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.

[0222] The additional mixing step may be performed immediately following the cooling step. In this case, the temperature of the mixture (b) at the start of the additional mixing step is the same as the temperature of the mixture (b) at the end of the cooling step.

[0223] In the additional mixing step, the mixing of the second anionic polymer or its aqueous solution, the cooled mixture (b), and optionally other components (06) 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 may or may not coincide with the temperature range of the mixture (b) in the cooling step.

[0224] The method for mixing the second anionic polymer or an aqueous solution thereof, the cooled mixture (b), and optionally other components (06) is not particularly limited and may be the same as, or different from, the method for mixing gelatin, the mixture (z), and optionally other components (02) in the presence of water in the emulsification step described above.

[0225] In the additional mixing step, when adding the remaining components to any of the additives (b) – the second anionic polymer or its aqueous solution, the cooled mixture (b), and other components (06) 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 components have been combined.

[0226] In the additional mixing step, after blending all components (the second anionic polymer or its aqueous solution, the cooled mixture (b), and other components (06) as needed), the time for stirring the resulting mixture is preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

[0227] In the additional mixing step, it is preferable to prepare the mixture (d) by, for example, adding or dropwise adding a second anionic polymer aqueous solution to the cooled mixture (b).

[0228] In the above manufacturing method, if an additional mixing step is performed, the crosslinking agent mixing step may be the same as the crosslinking agent mixing step described earlier, except that the mixed liquid (d) is used instead of the cooled mixed liquid (b).

[0229] The microcapsules obtained by the manufacturing method may be used as a water dispersion as they are, or the water dispersion obtained by performing known post-treatment, purification, etc. may be used as it is, or after performing known post-treatment, purification, etc. as necessary, the dispersion medium may be removed and the microcapsules may be used as a single entity (dry product). Regardless of the state (especially even as a single entity (dry product) after removing the dispersion medium), the microcapsules have a high encapsulation retention performance of lavender essential oil as the core substance.

Examples

[0230] Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples shown below.

[0231] The lavender essential oil used in the following examples and comparative examples is shown in Table 1.

[0232]

Table 1

[0233] The additives used in the following examples are shown in Table 2.

[0234]

Table 2

[0235] The other additives used in the following comparative examples are shown in Table 3.

[0236]

Table 3

[0237] A part of the polymers used in the following examples and comparative examples is shown in Table 4.

[0238]

Table 4

[0239] The crosslinking agents used in the following Examples and Comparative Examples are shown in Table 5.

[0240]

Table 5

[0241] [Example 1] <<Manufacture of Microcapsules>> At room temperature (under the condition of 23°C), for lavender essential oil (i)-1 (true lavender essential oil, corresponding to the core substance) (40 g), additive (ii)-1 (sorbitan trioleate) (0.4 g) was added, and the resulting mixture was stirred until it became uniform to obtain a mixed solution (z) (the first mixing step).

[0242] An aqueous solution (130 g) of gelatin (Type A manufactured by Nitta Gelatin Co., Ltd.) with a concentration of 5% by mass was heated to 50°C, and the entire amount of the mixed solution (z) obtained above at room temperature was added to this aqueous solution, and an emulsifier (manufactured by Primix Co., Ltd.) was used to stir at 3000 rpm at room temperature for 3 minutes to prepare an emulsion (emulsification step).

[0243] An aqueous solution (130 g) of polymer (iii)-1 (gum arabic, corresponding to the first anionic polymer) with a concentration of 9% by mass was heated to 50°C, and the entire amount of the emulsion obtained above was added to this aqueous solution and stirred. Next, the entire amount of an aqueous solution (2 g) of polymer (iii)-2 (sodium carboxymethyl cellulose, corresponding to the second anionic polymer) with a concentration of 10% by mass at normal temperature was added to the above-obtained mixture and stirred for 2 minutes to prepare a mixed solution (a) (emulsion mixing step).

[0244] Next, under conditions of 50°C, while stirring the mixture (a), 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 the mixture was stirred for 2 minutes to adjust the pH of the mixture (a) to 3.8, thereby preparing an acidic mixture (b) (acidification step).

[0245] Next, the resulting mixture (b) was cooled at a cooling rate of 0.5°C / min while being stirred until its temperature reached 5°C (cooling step).

[0246] Next, to the mixture (b) being stirred at a temperature of 5°C, crosslinking agent (iv)-1 (transglutaminase) (5g) was added and stirred for 2 minutes under the same temperature condition of 5°C to prepare mixture (c) (crosslinking agent mixing step).

[0247] Next, under conditions of 5°C, while stirring, an aqueous solution of sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) with a concentration of 20% by mass was added dropwise, and the mixture was stirred for 2 minutes to adjust the pH of the mixture (c) to 6.0. Then, the pH-adjusted mixture (c) was heated and stirred at 20°C for 4 hours to allow the enzymatic reaction of crosslinking agent (iv)-1 to proceed, and further stirring at 72°C for 17 minutes deactivated the excess crosslinking agent (iv)-1 to produce an aqueous dispersion of microcapsules (base mixing step). Based on the above, a microcapsule was obtained as an aqueous dispersion containing gelatin, gum arabic (high molecular weight (iii)-1), sodium carboxymethylcellulose (high molecular weight (iii)-2) as the wall material component, and transglutaminase (crosslinking agent (iv)-1), and containing true lavender essential oil (lavender essential oil (i)-1) and sorbitan trioleate (additive (ii)-1) as the core material.

[0248] The raw materials used in this example are shown in Table 6. In Table 6, the "Additives (Amount Added (Mass %))" column's "Amount Added (Mass %)" refers to the ratio of the amount of additives used (parts by mass) to the amount of lavender essential oil used (parts by mass). Similarly, the "Additives (Amount Added (Mass %))" column's "Amount Added (Mass %)" refers to the ratio of the amount of other additives used (parts by mass) to the amount of lavender essential oil used (parts by mass). In Table 6, a "-" indicates that the ingredient in that column is not used.

[0249] <<Evaluation of Microcapsules>> <Evaluation of microcapsule encapsulation and retention performance (1) (Evaluation of the effect of suppressing leakage of lavender essential oil from microcapsules)> Using a wire bar (No. 30), the aqueous dispersion of microcapsules obtained above was coated onto fine paper and dried in an oven at 105°C for 10 minutes. Next, the obtained dried material was observed using a scanning electron microscope (SEM, JEOL Ltd. "JSM-6700F"), and the degree of lavender essential oil leakage from the microcapsules was evaluated according to the following criteria. If lavender essential oil has leaked from the microcapsules, it will appear as a black image in the SEM image, as the lavender essential oil accumulated between the microcapsules will be visible. The presence or absence of such a black image was used as an indicator to determine whether or not lavender essential oil leakage had occurred. The results are shown in Table 7. [Evaluation Criteria] A: There was no leakage of lavender essential oil at all, or only a small amount leaked, indicating a high level of inhibition of lavender essential oil leakage from the microcapsules. B: The amount of lavender essential oil leakage was high, and the effect of suppressing the leakage of lavender essential oil from the microcapsules was low or not observed.

[0250] <Evaluation of microcapsule encapsulation retention performance (2) (Confirmation of the degree of encapsulation of lavender essential oil in microcapsules)> A cylindrical weight (4 kg) was placed on the dried product for evaluating the above-mentioned "effect of suppressing the leakage of lavender essential oil from microcapsules". At this time, the side surface of the weight was brought into contact with the dried product. Then, the weight was rolled back and forth 5 times on the dried product to pressurize the dried product. Next, by checking whether the dried product after pressurization smelled of lavender essential oil, the degree of encapsulation of lavender essential oil in the microcapsules was evaluated according to the following criteria. The results are shown in Table 7. [Evaluation Criteria] A: The smell of lavender essential oil was clearly felt from the dried product, and the microcapsules contained a sufficient amount of lavender essential oil. B: The smell of lavender essential oil was not felt at all from the dried product, or was only slightly felt, indicating that the microcapsules did not contain any lavender essential oil or contained a small amount of lavender essential oil.

[0251] <Measurement of the average particle diameter of microcapsules> Using a particle size distribution measuring device ("MT3000II" manufactured by Microtrac Bell Co., Ltd.) and the aqueous dispersion obtained above, the average particle diameter of the microcapsules was measured. The results are shown in Table 7.

[0252] <Classification of the safety of microcapsules> The safety of the obtained microcapsules to the living body was classified according to the following criteria based on the raw materials for manufacturing the wall material. The results are shown in Table 7. [Classification Criteria] A: As raw materials for manufacturing the wall material, those with strong toxicity to the living body are not used, and the safety of the microcapsules to the living body is high. B: As raw materials for manufacturing the wall material, those with strong toxicity to the living body are used, and the safety of the microcapsules to the living body is low.

[0253] <<Manufacture and evaluation of microcapsules>> [Example 2] Microcapsules were manufactured and evaluated in the same manner as in Example 1, except that additive (ii)-2 (polyoxyalkylene lauryl ether) (0.4 g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4 g). In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained transglutaminase (crosslinking agent (iv)-1). Microcapsules containing true lavender essential oil (lavender essential oil (i)-1) and polyoxyalkylene lauryl ether (additive (ii)-2) as core material were obtained as an aqueous dispersion. The results are shown in Table 7.

[0254] [Example 3] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that additive (ii)-3 (sorbitan monooleate) (0.4g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4g). In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained transglutaminase (crosslinking agent (iv)-1). Microcapsules containing true lavender essential oil (lavender essential oil (i)-1) and sorbitan monooleate (additive (ii)-3) as core material were obtained as aqueous dispersions. The results are shown in Table 7.

[0255] [Example 4] Microcapsules were manufactured and evaluated using the same method as in Example 3, except that the amount of additive (ii)-3 (sorbitan monooleate) used was changed from 0.4 g to 1.2 g. The results are shown in Table 7.

[0256] [Example 5] Microcapsules were manufactured and evaluated in the same manner as in Example 1, except that additive (ii)-4 (polyoxyethylene oleyl cetyl ether) (1.2 g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4 g). In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained transglutaminase (crosslinking agent (iv)-1). Microcapsules containing true lavender essential oil (lavender essential oil (i)-1) and polyoxyethylene oleyl cetyl ether (additive (ii)-4) as core material were obtained as aqueous dispersions. The results are shown in Table 7.

[0257] [Example 6] Microcapsules were manufactured and evaluated in the same manner as in Example 1, except that additive (ii)-5 (polyoxyalkylene alkyl ether) (1.2 g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4 g). In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained transglutaminase (crosslinking agent (iv)-1). The microcapsules, obtained as an aqueous dispersion, contained true lavender essential oil (lavender essential oil (i)-1) and polyoxyalkylene alkyl ether (additive (ii)-5) as core materials. The results are shown in Table 7.

[0258] [Example 7] Microcapsules were manufactured and evaluated in the same manner as in Example 1, except that additive (ii)-6 (polyoxyalkylene tridecyl ether) (1.2 g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4 g). In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained transglutaminase (crosslinking agent (iv)-1). Microcapsules containing true lavender essential oil (lavender essential oil (i)-1) and polyoxyalkylene tridecyl ether (additive (ii)-6) as core material were obtained as an aqueous dispersion. The results are shown in Table 7.

[0259] [Example 8] Microcapsules were manufactured and evaluated in the same manner as in Example 2, except that the same amount (parts by mass) of polymer (iii)-3 (sodium alginate, corresponding to a second anionic polymer) was used instead of polymer (iii)-2 (sodium carboxymethylcellulose). In this example, the wall material component consisted of gelatin, gum arabic (polymer (iii)-1), and sodium alginate (polymer (iii)-3), and further contained transglutaminase (crosslinking agent (iv)-1). The microcapsules, obtained as an aqueous dispersion, contained true lavender essential oil (lavender essential oil (i)-1) and polyoxyalkylene lauryl ether (additive (ii)-2) as core materials. The results are shown in Table 7.

[0260] [Example 9] Microcapsules were manufactured and evaluated in the same manner as in Example 2, except that the same amount (parts by mass) of polymer (iii)-3 (sodium alginate, corresponding to a second anionic polymer) was used instead of polymer (iii)-1 (gum arabic). In this example, the wall material component consisted of gelatin, sodium carboxymethylcellulose (polymer (iii)-2), and sodium alginate (polymer (iii)-3), and further contained transglutaminase (crosslinking agent (iv)-1). The microcapsules, obtained as an aqueous dispersion, contained true lavender essential oil (lavender essential oil (i)-1) and polyoxyalkylene lauryl ether (additive (ii)-2) as core materials. The results are shown in Table 7.

[0261] [Example 10] The process up to the cooling of the mixture (b) was carried out in the same manner as in Example 2 (first mixing step to cooling step). Next, to the mixture (b) being stirred at a temperature of 5°C, an aqueous solution (20g) of polymer (iii)-2 (carboxymethylcellulose sodium, corresponding to a second anionic polymer) with a concentration of 10% by mass was added, and the mixture (d) was prepared by stirring for 2 minutes while maintaining the temperature at 5°C (additional mixing step). Next, to the mixture (d) being stirred at a temperature of 5°C, crosslinking agent (iv)-2 (tannic acid) (5g) was added and stirred for 2 minutes under the same temperature condition of 5°C to prepare mixture (c) (crosslinking agent mixing step). Next, under conditions of 5°C, while stirring, an aqueous solution of sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) with a concentration of 20% by mass was added dropwise, and the mixture was stirred for 2 minutes to adjust the pH of the mixture (c) to 6.0. Then, the pH-adjusted mixture (c) was heated and stirred at 20°C for 4 hours to produce an aqueous dispersion of microcapsules (base mixing step). Based on the above, a microcapsule was obtained as an aqueous dispersion containing gelatin, gum arabic (high molecular weight (iii)-1), sodium carboxymethylcellulose (high molecular weight (iii)-2) as the wall material component, and further containing tannic acid (crosslinking agent (iv)-2), and containing true lavender essential oil (lavender essential oil (i)-1) and polyoxyalkylene lauryl ether (additive (ii)-2) as the core material. The obtained microcapsules were evaluated using the same method as in Example 2. The results are shown in Table 7.

[0262] [Example 11] Microcapsules were manufactured and evaluated in the same manner as in Example 10, except that crosslinking agent (iv)-3 (glutaraldehyde) (5g) was used instead of crosslinking agent (iv)-2 (tannic acid) (5g), and the pH of the mixture (c) was adjusted from 6.0 to 9.0 in the base mixing step. In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained glutaraldehyde (crosslinking agent (iv)-3). Microcapsules containing true lavender essential oil (lavender essential oil (i)-1) and polyoxyalkylene lauryl ether (additive (ii)-2) as core material were obtained as aqueous dispersions. The results are shown in Table 7.

[0263] [Example 12] Microcapsules were manufactured and evaluated in the same manner as in Example 2, except that lavender essential oil (i)-2 (lavandin essential oil, corresponding to the core substance) (40g) was used instead of lavender essential oil (i)-1 (true lavender essential oil) (40g). In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained transglutaminase (crosslinking agent (iv)-1). Microcapsules containing lavandin essential oil (lavender essential oil (i)-2) and polyoxyalkylene lauryl ether (additive (ii)-2) as core substances were obtained as aqueous dispersions. The results are shown in Table 7.

[0264] [Example 13] Microcapsules were manufactured and evaluated in the same manner as in Example 2, except that lavender essential oil (i)-3 (spike lavender essential oil, corresponding to the core substance) (40g) was used instead of lavender essential oil (i)-1 (true lavender essential oil) (40g). In this example, the wall material component consisted of gelatin, gum arabic (high molecular weight (iii)-1), and sodium carboxymethylcellulose (high molecular weight (iii)-2), and further contained transglutaminase (crosslinking agent (iv)-1). Microcapsules containing spike lavender essential oil (lavender essential oil (i)-3) and polyoxyalkylene lauryl ether (additive (ii)-2) as core substances were obtained as aqueous dispersions. The results are shown in Table 7.

[0265] [Comparative Example 1] Microcapsules were manufactured and evaluated in the same manner as in Example 1, except that additive (ii)-1 (sorbitan trioleate) was not used. In other words, in this comparative example, the first mixing step was omitted, and lavender essential oil (i)-1 (true lavender essential oil) (40g) was used instead of the mixture (z). The emulsification step was performed in the same manner as in Example 1, and thereafter, an aqueous dispersion of microcapsules was obtained in the same manner as in Example 1. The results are shown in Table 7.

[0266] [Comparative Example 2] Microcapsules were manufactured and evaluated using the same method as in Comparative Example 1, except that lavender essential oil (i)-2 (lavandin essential oil) (40g) was used instead of lavender essential oil (i)-1 (true lavender essential oil) (40g). The results are shown in Table 7.

[0267] [Comparative Example 3] Microcapsules were manufactured and evaluated using the same method as in Comparative Example 1, except that lavender essential oil (i)-3 (spike lavender essential oil) (40g) was used instead of lavender essential oil (i)-1 (true lavender essential oil) (40g). The results are shown in Table 7.

[0268] [Comparative Example 4] Microcapsules were manufactured and evaluated using the same method as in Comparative Example 1, except that polymer (iii)-2 (carboxymethylcellulose sodium) was not used. The results are shown in Table 7.

[0269] [Comparative Example 5] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that additive (x)-1 (polyoxyethylene lauryl ether) (0.4 g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4 g). The results are shown in Table 7.

[0270] [Comparative Example 6] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that additive (x)-2 (polyoxyethylene polyoxypropylene glycol) (0.4 g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4 g). The results are shown in Table 7.

[0271] [Comparative Example 7] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that additive (x)-3 (polyoxyethylene oleate ester) (1.2 g) was used instead of additive (ii)-1 (sorbitan trioleate) (0.4 g). The results are shown in Table 7.

[0272] [Comparative Example 8] <<Microcapsule Manufacturing>> At room temperature, a mixture (y1) was prepared by adding an ethyl acetate solution of trimethylolpropane adduct of trilene-2,4-diisocyanate (hereinafter referred to as "TDI-TMP adduct") with a concentration of 75% by mass (26.7 g of Takenate D-103H manufactured by Mitsui Chemicals, Inc., and 20 g of TDI-TMP adduct) to lavender essential oil (i)-1 (true lavender essential oil) (40 g), and stirring until the resulting mixture was homogeneous.

[0273] Distilled water (142.5g) was mixed with polyvinyl alcohol (JP-24, manufactured by Nippon Vivaceae Co., Ltd., degree of saponification: 87-89) (7.5g), stirred at 90°C for 1 hour to form a solution, and then cooled to 25°C to obtain a 5% by mass aqueous solution of polyvinyl alcohol.

[0274] At room temperature, the entire amount of the polyvinyl alcohol aqueous solution was added to the entire amount of the mixture (y1) obtained above, and an emulsion was prepared by stirring for 3 minutes at a rotation speed of 3000 rpm using an emulsifier (manufactured by Primix).

[0275] At room temperature, 1,3-bisaminomethylcyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.) (4g) was added to the entire amount of the resulting emulsion and stirred. Then, interfacial polycondensation was carried out by stirring the reaction mixture at 80°C for 2 hours. Based on the above, we obtained microcapsules in aqueous dispersion form, using polyurea, a polycondensate of 1,3-bisaminomethylcyclohexane and a TDI-TMP adduct, as the wall material component, and containing true lavender essential oil (lavender essential oil (i)-1) as the core material.

[0276] <<Evaluation of Microcapsules>> The microcapsules obtained above were evaluated using the same method as in Example 1. The results are shown in Table 7.

[0277] [Table 6]

[0278] [Table 7]

[0279] As is clear from the results above, in Examples 1 to 13, the average particle size of the microcapsules was 29 μm or less (21 to 29 μm), indicating that the particle size of the microcapsules was small. In Examples 1 to 13, the microcapsules were composed of gelatin, a primary anionic polymer, a secondary anionic polymer, and a crosslinking agent.

[0280] In Examples 1 to 13, even when the microcapsules were dried, leakage of lavender essential oil from the microcapsules was suppressed, and furthermore, the microcapsules contained a sufficient amount of lavender essential oil, indicating high encapsulation retention performance of the microcapsules. In Examples 1 to 13, the emulsified liquid exhibited high stability during the emulsification process. The microcapsules in Examples 1-13 contained lavender essential oil and either a polyoxyalkylene alkyl ether with an HLB value of 9.0 or less (3.0-9.0) or a sorbitan fatty acid ester with an HLB value of 4.3 or less (1.8-4.3).

[0281] The microcapsules in Examples 1-13 did not use any highly toxic substances as raw materials for the wall material, and therefore demonstrated high safety for living organisms. The microcapsules in Examples 1-13 were biodegradable.

[0282] In contrast, in Comparative Examples 1-3, when the microcapsules were dried, leakage of lavender essential oil from the microcapsules was not suppressed, indicating poor encapsulation and retention performance of the microcapsules. In Comparative Examples 1-3, the stability of the emulsified solution during the emulsification process was low. The microcapsules of Comparative Examples 1-3 did not contain polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less, nor sorbitan fatty acid esters (additive (ii)) with an HLB value of 10.0 or less.

[0283] In Comparative Example 4, the average particle size of the microcapsules was 75 μm, indicating that the particle size of the microcapsules was large. In Comparative Example 4, the microcapsules contained only one type of anionic polymer.

[0284] In Comparative Example 5, when the microcapsules were dried, they did not contain lavender essential oil, indicating poor encapsulation and retention performance of the microcapsules. In Comparative Example 5, the stability of the emulsified solution during the emulsification process was low. The microcapsules of Comparative Example 5 did not contain either a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, or a sorbitan fatty acid ester with an HLB value of 10.0 or less (additive (ii)), but instead contained polyoxyethylene lauryl ether with an HLB value of 12.1 (other additive (x)).

[0285] In Comparative Examples 6 and 7, when the microcapsules were dried, leakage of lavender essential oil from the microcapsules was not suppressed, indicating poor encapsulation and retention performance of the microcapsules. In Comparative Examples 6 and 7, the stability of the emulsified solution during the emulsification process was low. The microcapsules of Comparative Examples 6 and 7 did not contain polyoxyalkylene alkyl ethers with an HLB value of 10.0 or less, nor sorbitan fatty acid esters with an HLB value of 10.0 or less (additive (ii)). Instead, the microcapsule of Comparative Example 6 contained polyoxyethylene polyoxypropylene glycol with an HLB value of 3.2 (other additive (x)), and the microcapsule of Comparative Example 7 contained polyoxyethylene oleate ester with an HLB value of 7.7 (other additive (x)).

[0286] The microcapsules in Comparative Example 8 were manufactured by an interfacial polycondensation method, not a composite coacervation method. As a raw material for the polyurea component of the wall material, a TDI-TMP adduct, which is highly toxic to living organisms, was used, the microcapsules had low safety to living organisms. [Industrial applicability]

[0287] This invention can be used as a microcapsule with lavender essential oil as the core material.

Claims

1. A microcapsule in which a core material is enclosed by a wall material, The microcapsule comprises gelatin, a first anionic polymer, a second anionic polymer of a different type from the first anionic polymer, and a crosslinking agent. The wall material is composed of the gelatin, the first anionic polymer, and the second anionic polymer. The microcapsules contain lavender essential oil and a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less. A microcapsule having an average particle diameter of 30 μm or less.

2. The microcapsule according to claim 1, wherein the crosslinking agent is one or more selected from the group consisting of transglutaminase, polyphenols, and glutaraldehyde.

3. A method for producing microcapsules according to claim 1 or 2, A step of preparing a mixed solution (z) by mixing lavender essential oil and a polyoxyalkylene alkyl ether with an HLB value of 10.0 or less, A step of preparing an emulsion by mixing gelatin and the aforementioned mixture (z) in the presence of water, A step of preparing a mixed solution (a) 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 (a) with an acid to produce an acidic mixture (b), The process involves cooling the aforementioned mixture (b) until its temperature is 10°C or lower. The process involves mixing the cooled mixture (b) with a crosslinking agent to produce a mixture (c), A method for producing microcapsules, comprising the step of mixing the aforementioned mixture (c) with a base to produce an aqueous dispersion of microcapsules with adjusted pH.

4. The method for producing microcapsules according to claim 3, wherein the crosslinking agent is one or more selected from the group consisting of transglutaminase, polyphenols, and glutaraldehyde.

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