Microcapsules

Abstract

To provide a micro capsule including, as a core substance, a lipophilic substance, and suppressing oxidation deterioration of the lipophilic substance.SOLUTION: There is provided a micro capsule, the micro capsule comprising therein: natural essential oil; and an oxidation inhibitor. The oxidation inhibitor is one or two or more kinds selected from a group formed of: tocopherol; and dibutylhydroxytoluene. The micro capsule includes: a lipophilic substance; and the oxidation inhibitor. The lipophilic substance has a carbon number of 9-11, and has one or two ore more unsaturated bonds between carbon atoms, or has one or two or more formyl groups. The oxidation inhibitor is one or two or more kinds selected from a group formed of tocopherol and dibutylhydroxytoluene, in the micro capsule.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to microcapsules. [Background technology]

[0002] Microcapsules are constructed by encapsulating a target component as a core material within a wall material. Furthermore, microcapsules can be designed to have a sustained-release property, gradually releasing the encapsulated oily component over time. For example, microcapsules containing components such as insect repellents, insecticides, insecticides, antibacterial agents, fragrances, and cosmetic materials as core materials can sustain the effects of these components over a long period by gradually releasing them, making them very useful.

[0003] Microcapsules are used in different forms depending on their application, typically as aqueous dispersions or dry materials. Dry microcapsules, in particular, have durability issues, and are prone to problems such as capsule breakage, increased core material release rate, and degradation due to oxidation of the core material. Of these, capsule breakage and increased core material release rate can be easily improved by appropriately designing the thickness and density of the membrane (wall material) that constitutes the microcapsule. However, degradation due to oxidation of the core material is difficult to improve because it is difficult to suppress oxygen permeation through the membrane. Oxidative degradation of the core material is a serious problem because it reduces or eliminates the original function of the core material, directly leading to a deterioration in the quality of the microcapsule and lowering its product value.

[0004] Antioxidants are typically used to suppress the oxidative degradation of chemical substances. Examples of chemical materials using antioxidants that have been disclosed to date include a diesel fuel composition containing dibutylhydroxytoluene as an antioxidant (see Patent Document 1), and microcapsules containing n-propyl gallate as an antioxidant along with a dye (see Patent Document 2). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2012-197353 [Patent Document 2] Japanese Patent Application Publication No. 3-267140 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, the types of chemical substances affected by antioxidants are relatively limited depending on the antioxidant. For example, natural essential oils are useful ingredients that can be used as insect repellents, insecticides, insecticides, antibacterial agents, fragrances, and cosmetic materials, but microcapsules that contain lipophilic components (lipophilic substances) like natural essential oils as a core material and effectively suppress their oxidative degradation have not been known until now.

[0007] The present invention aims to provide microcapsules that contain a lipophilic substance as a core material and in which oxidative degradation of the core material is suppressed. [Means for solving the problem]

[0008] To solve the above problems, the present invention adopts the following configuration. [1] A microcapsule containing a natural essential oil and an antioxidant, wherein the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene. [2] A microcapsule comprising a lipophilic substance and an antioxidant, wherein the lipophilic substance has 9 to 11 carbon atoms and has one or more unsaturated bonds between carbon atoms, or has one or more formyl groups, and the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene. [3] The microcapsule according to [2], wherein the lipophilic substance is either terpinen-4-ol or citronellal or both. [4]. The microcapsule according to [1], wherein the natural essential oil is either tea tree oil or lemon eucalyptus oil or both. [Effects of the Invention]

[0009] According to the present invention, microcapsules are provided that contain a lipophilic substance as a core material and whose oxidative degradation is suppressed. [Modes for carrying out the invention]

[0010] ◎Microcapsules (First Embodiment) The microcapsule according to the first embodiment of the present invention contains a natural essential oil and an antioxidant, wherein the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene. The microcapsules of this embodiment (which may be referred to as "microcapsule(1)" in this specification) contain a specific range of antioxidants along with natural essential oils, thereby suppressing oxidative degradation of the natural essential oils even in a dry state (even if they are dried products).

[0011] The microcapsule (1) is constructed by enclosing a core substance (for example, a natural essential oil, the aforementioned antioxidant) within a wall material. Microcapsules (1) can be manufactured by applying known methods such as the composite coacervation method and the interfacial polycondensation method, as described later.

[0012] <<Natural essential oil>> In the microcapsule (1), the natural essential oil is not particularly limited and may be a known one. Natural essential oils are oily at room temperature.

[0013] In this specification, "normal temperature" means a temperature that is not particularly cooled or heated, that is, an ordinary temperature, and examples thereof include a temperature of 15 to 25°C.

[0014] Preferred natural essential oils include, for example, lipophilic substances (lipophilic components) that can be used as insect repellents, insecticides, insect-proof agents, antibacterial agents, fragrances, or cosmetic materials.

[0015] More specifically, preferred natural essential oils include, for example, tea tree essential oil having terpinene-4-ol, 1,8-cineole, γ-terpinene, α-terpinene, etc. as main components; lemon eucalyptus oil having citronellal, etc. as main components.

[0016] The natural essential oil encapsulated in the microcapsule (1) may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected according to the purpose.

[0017] In the microcapsule (1), the natural essential oil is preferably either one or both of tea tree essential oil and lemon eucalyptus oil. In addition to their high utility value, these natural essential oils have a particularly high effect of suppressing oxidative degradation in the dried microcapsule (1).

[0018] In the microcapsule (1), the content of the natural essential oil can be adjusted as appropriate. For example, by applying the complex coacervation method to produce the microcapsule (1), in the microcapsule (1) containing gelatin as the wall material component described later, the content of the natural essential oil is preferably 100 to 1000 parts by mass with respect to 100 parts by mass of the content of gelatin, and may be, for example, either 200 to 800 parts by mass or 300 to 600 parts by mass. The microcapsule (1) having the content of the natural essential oil within such a range has better quality and can be manufactured more easily.

[0019] In the microcapsules (1), the content of the natural essential oil can be adjusted according to the manufacturing conditions of the microcapsules (1) described below, regardless of the manufacturing method of the microcapsules (1). For example, when manufacturing the microcapsules (1) by applying the interfacial polycondensation method, the content (encapsulation amount) of the natural essential oil is preferably adjusted by considering the blending amount of the natural essential oil and the blending amount of the raw material of the wall material (for example, the polyisocyanate compound etc. described below) as described below.

[0020] <<Antioxidant>> The microcapsules (1) encapsulate the antioxidant together with the natural essential oil. In such microcapsules (1), even when the microcapsules (1) are in a dried state, the oxidative degradation of the natural essential oil is suppressed.

[0021] In the microcapsules (1), the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene (3,5 - di - tert - butyl - 4 - hydroxytoluene). In this specification, unless otherwise specified, the "antioxidant" in the microcapsules (1) means tocopherol and dibutylhydroxytoluene. In this specification, unless otherwise specified, "tocopherol" is a concept that includes all of α - tocopherol, β - tocopherol, γ - tocopherol and δ - tocopherol. That is, the microcapsules (1) may encapsulate one or more kinds of tocopherols and may not encapsulate dibutylhydroxytoluene, or may encapsulate dibutylhydroxytoluene and may not encapsulate tocopherol, or may encapsulate both one or more kinds of tocopherols and dibutylhydroxytoluene.

[0022] Among the four types of tocopherols, α-tocopherol, β-tocopherol, γ-tocopherol, and δ-tocopherol are preferred in terms of their antioxidant effect, in that order. In other words, the most preferred tocopherol is α-tocopherol.

[0023] In the microcapsule (1), the antioxidant content (the total amount of tocopherol and dibutylhydroxytoluene) is preferably 0.05% by mass or more relative to the natural essential oil content, and may be, for example, 0.2% by mass or more, 0.4% by mass or more, 0.6% by mass or more, or 0.8% by mass or more. When the antioxidant content is above the lower limit, the effect of suppressing the oxidative degradation of the natural essential oil in the microcapsule (1) is further enhanced. In the microcapsule (1), the antioxidant content is preferably 3% by mass or less relative to the natural essential oil content, and may be, for example, 0.5% by mass or less. By keeping the antioxidant content below the upper limit, the excessive use of antioxidants is suppressed. In one embodiment, the content of the antioxidant may be any of 0.05 to 3% by mass, 0.2 to 3% by mass, 0.4 to 3% by mass, 0.6 to 3% by mass, and 0.8 to 3% by mass, or 0.05 to 0.5% by mass. However, these are just examples of the content of the antioxidant.

[0024] <<Wall materials, wall material components>> In the microcapsule (1), the wall material containing the natural essential oil and the antioxidant is not particularly limited as long as it is capable of forming the microcapsule (1), and may be any known material.

[0025] The wall material is determined, for example, by the manufacturing method of the microcapsules (1). When manufacturing microcapsules (1) by applying a composite coacervation method, the wall material may be composed of, for example, gelatin, a first anionic polymer, and a second anionic polymer of a different type from the first anionic polymer (sometimes referred to as "wall material (1)" in this specification). It is preferable that the microcapsules (1) having such a wall material further contain a crosslinking agent, the crosslinking agent interacting with the wall material to firmly constitute the wall material. When manufacturing microcapsules (1) by applying the interfacial polycondensation method, the wall material may be, for example, one composed of polyurea, polyurethane, polyamide, etc. (referred to as "wall material (2)" in this specification).

[0026] <Wall material (1)> [gelatin] In the wall material (1), the gelatin, together with the first anionic polymer and the second anionic polymer, is a component of the wall material of the microcapsule (1). The gelatin that makes up the wall material is a cationic polymer that has a cationic part in its molecule.

[0027] As for gelatin, ordinary types, such as those derived from animal bones or skin, can be used. The molecular weight of gelatin may be, for example, between 20,000 and 9,000,000.

[0028] Since gelatin is an amphoteric polymer that can be either cationic or anionic, it is used after being cationized by the action of an acid, as will be described later.

[0029] The gelatin that makes up the microcapsule (1) may be derived from only one type or from two or more types, and if there are two or more types, the combination and ratio of these can be arbitrarily selected.

[0030] [First anionic polymer] The first anionic polymer is a polymer having an anionic portion in its molecule, and together with gelatin, it serves as a wall material component of the microcapsule (1).

[0031] The first anionic polymer is not particularly limited as long as it is a polymer having anionic groups. Examples of primary anionic polymers include polymers having groups in which an acidic groups have been dissociated (anionized). More specifically, as a first anionic polymer, 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.

[0032] 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.

[0033] 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 )

[0034] 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.

[0035] 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.

[0036] In the microcapsule (1), 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.

[0037] [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 wall material component of the microcapsule (1).

[0038] 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.

[0039] 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.

[0040] Examples of secondary anionic polymers include those similar to the primary anionic polymers described earlier.

[0041] The molecular weight of the second anionic polymer may be the same as that of the second anionic polymer described earlier.

[0042] In the microcapsule (1), the content of the secondary anionic polymer per 100 parts by mass of gelatin is preferably 2 to 80 parts by mass, for example, it may be any of 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 any of 10 to 80 parts by mass, 30 to 80 parts by mass, and 50 to 80 parts by mass, or any of 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.

[0043] The first anionic polymer and the second anionic polymer contained in the microcapsule (1) (in other words, constituting the wall material components) may be 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.

[0044] In this embodiment, for example, if the microcapsule (1) contains only two types of anionic polymers in total, the anionic polymer with a higher content (parts by mass) in the microcapsule (1) 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.

[0045] On the other hand, if a microcapsule (1) 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 is the most abundant anionic polymer in the microcapsule (1), 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 (1), and is the sum of the contents of each individual anionic polymer.

[0046] 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 microcapsule (1) 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.

[0047] The microcapsule (1) may contain, for example, only one type each of the first anionic polymer and the second anionic polymer, or it may contain only one type of the first anionic polymer and two or more types of the second anionic polymer, or it may contain two or more types of the first anionic polymer and only one type of the second anionic polymer, or it may contain two or more types each of the first anionic polymer and the second anionic polymer.

[0048] In the method for producing the microcapsules (1) described later, the timing of the use of the first anionic polymer and the second anionic polymer is important. This point, along with the method for producing the microcapsules (1), will be explained in detail later.

[0049] In the microcapsule (1), the content of the first anionic polymer per 100 parts by mass of the content of the second anionic polymer is preferably 50 to 600 parts by mass, for example, it may be any of 100 to 600 parts by mass, 200 to 600 parts by mass, and 300 to 600 parts by mass, or any of 50 to 400 parts by mass, 50 to 200 parts by mass, and 50 to 100 parts by mass, or 100 to 400 parts by mass. When the content is above the lower limit, the yield of the microcapsule (1) is further improved. When the content is below the upper limit, the encapsulation and retention performance of the microcapsule (1) is further improved.

[0050] In the microcapsule (1), 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, it may be any of 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 any of 70 to 290 parts by mass, 140 to 290 parts by mass, and 210 to 290 parts by mass, or any of 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 microcapsule (1) is further improved. When the total content is below the upper limit, the encapsulation retention performance of the microcapsule (1) is further improved.

[0051] The microcapsule (1) has a smaller average particle size because it contains at least two types of anionic polymers, a first anionic polymer and a second anionic polymer, as its wall material components. For example, if the microcapsule (1) contains only one type of anionic polymer as its wall material component, aggregation or coalescence of the microcapsule (1) itself or aggregation or coalescence of the wall material components during the formation process of the microcapsule (1) may occur. In such cases, the microcapsule (1) may not form properly, or even if it does form, the particle size will be significantly larger.

[0052] When manufacturing microcapsules (1) by applying the interfacial polycondensation method, the wall material may be, for example, one composed of polyurea, polyurethane, polyamide, etc. (referred to as "wall material (2)" in this specification).

[0053] <Wall material (2)> The polyurea, polyurethane, and polyamide in the microcapsule (1) may be the same as those in a typical microcapsule. In this specification, "polyurea" means an oligomer or polymer having a bond (urea bond) represented by the formula "-NH-C(=O)-NH-", which can be obtained, for example, by polycondensation reaction of a polyisocyanate compound having two or more isocyanate groups and a polyamine compound having two or more amino groups as starting compounds. "Polyurethane" refers to an oligomer or polymer having a bond (urethane bond) represented by the formula "-NH-C(=O)-O-". For example, it can be obtained by polycondensation reaction of a polyisocyanate compound having two or more isocyanate groups and a polyhydroxy compound having two or more hydroxyl groups (-OH) as raw material compounds. "Polyamide" refers to an oligomer or polymer having a bond (amide bond) represented by the formula "-NH-C(=O)-". For example, it can be obtained by polycondensation reaction of a polycarboxylic acid having two or more carboxyl groups (-C(=O)-OH), or a carboxylic acid chloride having a structure in which one or more carboxyl groups are substituted with chlorocarbonyl groups (-C(=O)-Cl), and a polyamine compound having two or more amino groups.

[0054] Examples of the polyisocyanate compounds for producing polyureas and polyurethanes include toylene-2,4-diisocyanate, toylene-2,6-diisocyanate, xylylene-1,3-diisocyanate, xylene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, 3-methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and dicyclo Examples include organic polyvalent polyisocyanate compounds such as hexylmethane-4,4'-diisocyanate and dicyclohexylmethane-2,4'-diisocyanate; derivatives of the above organic polyvalent polyisocyanate compounds (provided that the isocyanate group is not substituted); trimethylolpropane adducts of the above organic polyvalent polyisocyanate compounds; and trimethylolpropane adducts of derivatives of the above organic polyvalent polyisocyanate compounds (provided that the isocyanate group is not substituted). In this specification, trimethylolpropane adducts may also be referred to as trimethylolpropane adducts.

[0055] The polyisocyanate compound may be used alone or in combination of two or more types. When using two or more types in combination, the combination and ratio of these compounds can be arbitrarily selected.

[0056] Examples of polyamine compounds used to produce polyureas include melamine, urea, and organic polyvalent polyamine compounds such as 1,3-bis(aminomethyl)cyclohexane.

[0057] The polyamine compound may be used alone or in combination of two or more types. When using two or more types in combination, the combination and ratio of these compounds can be arbitrarily selected.

[0058] Examples of the polyhydroxy compounds used to produce polyurethane include organic polyhydroxy compounds, and examples of the organic polyhydroxy compounds include ethylene glycol, propylene glycol, alkylene glycol such as 1,4-butanediol, and the like.

[0059] The polyhydroxy compound may be used alone or in combination of two or more types. When using two or more types in combination, the combination and ratio of these compounds can be arbitrarily selected.

[0060] Examples of the polyamine compounds used to produce polyamides include the same polyamine compounds used to form polyureas as described above. Furthermore, examples of the polyamine compounds used to produce polyamides include aliphatic polyvalent polyamine compounds such as hexamethylenediamine, nonanediamine, methylpentadiamine, and diethylenetriamine.

[0061] The polyamine compound used to produce the polyamide may be used alone or in combination of two or more types. When two or more types are used in combination, the combination and ratio of these compounds can be arbitrarily selected.

[0062] The polycarboxylic acid used to produce the polyamide does not have an amino group. Examples of the polycarboxylic acid include organic polycarboxylic acids (aliphatic polycarboxylic acids, aromatic polycarboxylic acids) such as adipic acid (hexanediic acid), sebacic acid (decanediic acid), terephthalic acid (benzene-1,4-dipolycarboxylic acid), and isophthalic acid (benzene-1,3-dipolycarboxylic acid).

[0063] The carboxylic acid chloride for producing the polyamide may have a structure in which one or more carboxyl groups of the polycarboxylic acid are substituted with chlorocarbonyl groups, or it may have a structure in which all carboxyl groups of the polycarboxylic acid are substituted with chlorocarbonyl groups.

[0064] For producing polyamides, the polycarboxylic acid and carboxylic acid chloride may be used individually or in combination of two or more types. When using two or more types in combination, the combination and ratio can be arbitrarily selected.

[0065] <<Crosslinking agent>> When manufacturing microcapsules (1) by applying a composite coacervation method, it is preferable that the microcapsules (1) further contain a crosslinking agent. It is presumed that the crosslinking agent in the microcapsule (1) 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.

[0066] The crosslinking agent may be any known agent and is not particularly limited. Preferred crosslinking agents include, for example, transglutaminase, polyphenols, and glutaraldehyde.

[0067] 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.

[0068] Examples of the aforementioned polyphenols include tannic acid, catechin, chlorogenic acid, gallic acid, quinic acid, and caffeic acid.

[0069] The crosslinking agent constituting the microcapsule (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0070] In the microcapsule (1), the crosslinking agent content is preferably 1 to 12 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 1 to 9 parts by mass or 1 to 6 parts by mass. When the crosslinking agent content is above the lower limit, the wall material of the microcapsule (1) becomes stronger. When the crosslinking agent content is below the upper limit, excessive use of the crosslinking agent is suppressed.

[0071] 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 microcapsules (1) 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 (1). In such cases, the particle size of the microcapsules (1) becomes larger. Therefore, it is preferable to use as little polyvalent metal salt as possible. For example, in microcapsules (1), 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 especially preferably 0 parts by mass (i.e., the microcapsules (1) 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.

[0072] The crosslinking agent is preferably one or more selected from the group consisting of glutaraldehyde, transglutaminase, and polyphenols, in that it strengthens the wall material of the microcapsule (1).

[0073] <<Other ingredients (1)>> In addition to the components described above, the microcapsule (1) may contain other components (1) to the extent that they do not impair the effects of the present invention.

[0074] <Other ingredients (11)> For example, when a microcapsule (1) is manufactured by applying a composite coacervation method, the microcapsule (1) may contain, as other components (1), other components (1) that do not fall under any of the following: natural essential oil, the antioxidant, gelatin, the first anionic polymer, the second anionic polymer, and the crosslinking agent (which may be referred to as "other components (11)" in this specification).

[0075] Other components (11) can be arbitrarily selected depending on the purpose and are not particularly limited.

[0076] The other components (11) contained in the microcapsule (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0077] Other components (11) include, for example, a solvent other than water; an oily component other than natural essential oils; an antioxidant other than the aforementioned antioxidants (tocopherol, dibutylhydroxytoluene); and an additive that does not fall under any of the following: water, the aforementioned solvent, the aforementioned oily component, the aforementioned antioxidant, or the aforementioned other antioxidant.

[0078] Examples of solvents other than water include solvents contained in the raw materials used in the manufacture of the microcapsules. In this specification, unless otherwise specified, the term "solvent" refers not only to components capable of dissolving solutes in solution, but also to components that act as a dispersion medium in a dispersion. The solvent other than water is preferably an organic solvent.

[0079] Examples of oily components other than the aforementioned natural essential oils include animal oils, vegetable oils, mineral oils, and so on. Examples of the aforementioned 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, and olive oil. Other oily components besides the aforementioned natural essential oils include, from a functional standpoint, fragrances, insecticides, insect repellents, cosmetics, deodorants, pharmaceuticals, disinfectants, and other chemical reactants. A chemical reactant is a component that, by reacting with a specific chemical substance, inhibits the action of that chemical substance, and does not fall under any of the categories of fragrance, insecticide, insect repellent, cosmetic, deodorant, pharmaceutical, or disinfectant. The oily components other than the aforementioned natural essential oils are preferably those that are in an oily state at room temperature.

[0080] Other components (11) other than the core material include, for example, other cationic polymers other than gelatin.

[0081] Examples of other cationic polymers include chitosan, casein, polyethyleneimine, and cation-modified polyvinyl alcohol.

[0082] <Other ingredients (12)> For example, when a microcapsule (1) is manufactured by applying an interfacial polycondensation method, the microcapsule (1) may contain, as other components (1), other components (1) that do not fall under any of the following: natural essential oils, antioxidants, polyureas, polyurethanes, and polyamides (which may be referred to as "other components (12)" in this specification).

[0083] Other components (12) can be arbitrarily selected depending on the purpose and are not particularly limited.

[0084] The other components (12) contained in the microcapsule (1) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected.

[0085] The other core material component (12) is the same as the other core material component (11).

[0086] Other components (12) other than the core material include, for example, polyurea, polyurethane, polyamide, and other polycondensates that do not fall under any of these categories; emulsifiers, etc.

[0087] Examples of the other polycondensates mentioned above include polycondensates obtained by polycondensing the polyisocyanate compound, the polyamine compound, the polyhydroxy compound, the polycarboxylic acid, and the carboxylic acid chloride with other compounds that do not fall under any of the above categories.

[0088] The emulsifier is an ingredient used in the manufacture of microcapsules (1). Examples of the emulsifiers include polyvinyl alcohol, carboxymethylcellulose (CMC), ethylcellulose, methylcellulose, casein, gum arabic, gelatin, belladonna oil, alkylbenzene sulfonates such as sodium benzenesulfonate and sodium dodecylbenzenesulfonate, polyoxyethylene sulfate, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, and poly(meth)acrylic acid.

[0089] When the other component (1) is the core material, the content of the other component (1) in the microcapsule (1) is preferably 30 parts by mass or less per 100 parts by mass of the total content of the core material that does not correspond to the other component (i.e., [Content of the other component (1) that is the core material in the microcapsule (1) (parts by mass)] / [Total content of the core material that does not correspond to the other component (1) in the microcapsule (1) (parts by mass)] × 100), for example, it may be 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, and it is particularly preferable that it be 0 parts by mass (i.e., the microcapsule (1) does not contain the other component (1)). By keeping the content of the other component (1) below the upper limit, the stability of the microcapsule (1) is further improved, and the wall material is formed more effectively.

[0090] If the other component (1) is a component other than the core material, the content of the other component (1) in the microcapsule (1) is preferably 30 parts by mass or less per 100 parts by mass of the total content of components other than the core material that do not fall under the other component (i.e., [Content of other component (1) other than the core material in the microcapsule (1) (parts by mass)] / [Total content of components other than the core material that do not fall under the other component (1) in the microcapsule (1) (parts by mass)] × 100), for example, it may be 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less, and it is particularly preferable that it be 0 parts by mass (i.e., the microcapsule (1) does not contain the other component (1)). By keeping the content of the other component (1) below the upper limit, the stability of the microcapsule (1) is further improved, and the wall material is formed more effectively.

[0091] Other components of the microcapsule (1) The average particle size of the microcapsules (1) is not particularly limited. For example, the average particle size of the microcapsules (1) may be 30 μm or less, or 5 μm or more. The average particle size of the microcapsules (1) can be adjusted, for example, by adjusting the type of raw material used in the manufacture of the microcapsules (1); or by adjusting the stirring speed of the liquid (e.g., reaction solution) containing the components for forming the wall material during the manufacture of the microcapsules (1).

[0092] 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.

[0093] In the case of microcapsules (1), no highly toxic substances are used as raw materials for the manufacture of the wall material, and therefore, microcapsules (1) are highly safe for living organisms. Furthermore, the microcapsules (1) can be easily made biodegradable by selecting appropriate materials as both the raw material for the wall material and the core material.

[0094] The microcapsules (1) can be designed to have a sustained-release property, gradually releasing the encapsulated core substance (especially natural essential oils) to the outside over time. Such microcapsules (1) can sustain the effects of the core substance over a long period of time. For example, microcapsules (1) composed of a combination of the aforementioned natural essential oils, antioxidants, wall coverings, and, if necessary, crosslinking agents are preferred as having higher sustained release properties.

[0095] ◎Microcapsules (Second Embodiment) A microcapsule according to a second embodiment of the present invention contains a lipophilic substance and an antioxidant, wherein the lipophilic substance has 9 to 11 carbon atoms and has one or more unsaturated bonds between carbon atoms, or has one or more formyl groups, and the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene. The microcapsules of this embodiment (which may be referred to as "microcapsules (2)" in this specification) contain a specific range of lipophilic substances along with a specific range of antioxidants, thereby suppressing oxidative degradation of the lipophilic substances even in a dry state (even if they are dry products).

[0096] The microcapsule (2) is constructed by enclosing a core material (for example, the lipophilic substance, the antioxidant) within a wall material. Microcapsules (2) can be manufactured by applying known methods such as the composite coacervation method and the interfacial polycondensation method, as will be described later.

[0097] <<Lipophilic substances>> In the microcapsule (2), the lipophilic substance has 9 to 11 carbon atoms and one or more unsaturated bonds between carbon atoms (in one molecule) (in this specification, this lipophilic substance may be referred to as "lipophilic substance (I)"), or has 9 to 11 carbon atoms and one or more formyl groups (in one molecule) (in this specification, this lipophilic substance may be referred to as "lipophilic substance (II)"). In this specification, unless otherwise specified, "lipophilic substance" in microcapsule (2) means either lipophilic substance (I) (a lipophilic substance having 9 to 11 carbon atoms and having one or more unsaturated bonds between carbon atoms) or lipophilic substance (II) (a lipophilic substance having 9 to 11 carbon atoms and having one or more formyl groups).

[0098] The lipophilic substances (lipophilic substance (I), lipophilic substance (II)) may be well-known substances. Lipophilic substances are oily at room temperature.

[0099] The unsaturated bond in the lipophilic substance (I) may be either a double bond (C=C) or a triple bond (C≡C). If the lipophilic substance (I) has two or more of the aforementioned unsaturated bonds, the aforementioned unsaturated bonds may consist only of double bonds, only of triple bonds, or both double and triple bonds. In particular, it is preferable that the lipophilic substance (I) has only double bonds as the unsaturated bonds (in other words, it does not have triple bonds). Generally, the fewer triple bonds a lipophilic substance (I) has, the more stable it is, and in this respect it has desirable properties.

[0100] The number of the unsaturated bonds possessed by the lipophilic substance (I) is preferably 1 to 4, and may be, for example, any of 1 to 3, 1 to 2, and 1. In the present specification, since the conjugated double bonds such as the unsaturated bonds possessed by the aromatic cyclic group are highly delocalized and thermodynamically stable, they are not included in the unsaturated bonds defining the lipophilic substance. That is, the unsaturated bonds defining the lipophilic substance (I) are unsaturated bonds other than conjugated double bonds.

[0101] Among them, the number of carbon atoms of the lipophilic substance (I) is preferably 10. Examples of the lipophilic substance (I) having 10 carbon atoms include terpinene (α-terpinene, γ-terpinene), terpineol (α-terpineol), ocimene (trans-β-ocimene), limonene ((R)-limonene), linalool (α-linalool, β-linalool), 1-phenyl-2-buten-1-one ((E)-1-phenyl-2-buten-1-one), and the like.

[0102] The number of formyl groups (-C(=O)-H) possessed by the lipophilic substance (II) may be, for example, any of 1 to 3, 1 to 2, and 1.

[0103] Among them, the number of carbon atoms of the lipophilic substance (II) is preferably 10. Examples of the lipophilic substance (II) having 10 carbon atoms include decanal (C9H 19 CHO), and the like.

[0104] Preferred lipophilic substances include, for example, lipophilic substances (lipophilic components) that can be used as components such as insect repellents, insecticides, insect-proof agents, antibacterial agents, fragrances, or cosmetic materials.

[0105] More specifically, preferred lipophilic substances include, for example, the main components of tea tree essential oils such as terpineol-4-ol, 1,8-cineole, γ-terpinene, and α-terpinene; the main components of lemon eucalyptus oil such as citronellal, and the like.

[0106] The lipophilic substance contained within the microcapsule (2) may be one type or two or more types, and if there are two or more types, their combination and ratio can be arbitrarily selected according to the purpose.

[0107] In the microcapsule (2), the lipophilic substance is preferably either terpinen-4-ol or citronellal, or both. These lipophilic substances have high utility value, and in addition, they exhibit a particularly high inhibitory effect on oxidative degradation in the dry state of the microcapsule (2).

[0108] In microcapsules (2), the content of lipophilic substances can be adjusted as appropriate. For example, in microcapsules (1) containing gelatin as a wall material component, as described later, the content of natural essential oil is preferably 100 to 1000 parts by mass per 100 parts by mass of gelatin, and may be, for example, 200 to 800 parts by mass and 300 to 600 parts by mass. Microcapsules (1) with the above-mentioned content of natural essential oil in this range are of better quality and can be manufactured more easily.

[0109] The content of lipophilic substances in microcapsules (2) can be adjusted by the manufacturing conditions of microcapsules (2) as described later, regardless of the manufacturing method of microcapsules (2). For example, when manufacturing microcapsules (2) by applying the interfacial polycondensation method, it is preferable to adjust the content (encapsulation amount) of lipophilic substances by adjusting the amount of lipophilic substances blended in consideration of the amount of raw materials for the wall material (for example, polyisocyanate compounds as described later), as described later.

[0110] <<Antioxidant>> The microcapsule (2) contains the antioxidant along with the lipophilic substance, and in such a microcapsule (2), oxidative degradation of the lipophilic substance is suppressed even when the microcapsule (2) is dried.

[0111] In the microcapsule (2), the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene (3,5-di-tert-butyl-4-hydroxytoluene), and is the same as the antioxidant in the microcapsule (1). The manner in which the microcapsule (2) contains the antioxidant is the same as the manner in which the microcapsule (1) contains the antioxidant. Therefore, further explanation regarding the antioxidants in the microcapsules (2) is omitted.

[0112] 〇Composition of microcapsules (2) Microcapsule (2) is the same as microcapsule (1), except that it contains the aforementioned lipophilic substance instead of natural essential oil as an essential core material.

[0113] For example, when a microcapsule (2) is manufactured by applying a composite coacervation method, the microcapsule (2) may contain other components (which may be referred to as "other components (21)" in this specification) that do not fall under any of the following categories: the lipophilic substance, the antioxidant, gelatin, the first anionic polymer, the second anionic polymer, or the crosslinking agent. Other components (21) include, for example, a solvent other than water; an oily component other than the lipophilic substance; an antioxidant other than the antioxidant (tocopherol, dibutylhydroxytoluene); and an additive that does not fall under any of the following: water, the solvent, the oily component, the antioxidant, or the other antioxidant.

[0114] The solvent other than water and the antioxidants other than the antioxidants (tocopherol, dibutylhydroxytoluene) are the same as the solvent other than water and the antioxidants other than the antioxidants in the microcapsule (1).

[0115] Examples of oily components other than the aforementioned lipophilic substances include, for example, those that are the same as the oily components other than the natural essential oil in the microcapsule (1), except that they do not have 9 to 11 carbon atoms and do not have one or more unsaturated bonds between carbon atoms.

[0116] <Other ingredients (22)> For example, when a microcapsule (2) is manufactured by applying an interfacial polycondensation method, the microcapsule (2) may contain other components (which may be referred to as "other components (22)" in this specification) that do not fall under any of the following categories: the lipophilic substance, the antioxidant, polyurea, polyurethane, or polyamide.

[0117] The other core material component (22) is the same as the other core material component (21). Among the other components (22), those other than the core material are the same as the other components (12) that are components other than the core material.

[0118] In this specification, the other components (21) and (22) are collectively referred to as the other component (2).

[0119] The microcapsules (2) can also be designed to have a sustained-release property, gradually releasing the encapsulated core material (especially the lipophilic substance) to the outside over time. Such microcapsules (2) can sustain the effects of the core material over a long period of time. For example, microcapsules (2) composed of the aforementioned lipophilic substance, antioxidant, wall material, and optionally a crosslinking agent, in appropriate combinations, are preferred as having higher sustained release properties.

[0120] Aside from the points mentioned above, microcapsule (2) is the same as microcapsule (1), and no further explanation of the composition of microcapsule (2) is provided.

[0121] ◎ Microcapsule manufacturing method Microcapsules (1) and microcapsules (2) can be manufactured using the same method as conventional microcapsules, except that the essential components of the core material are different.

[0122] More specifically, for example, when producing a microcapsule (1) containing a natural essential oil and the antioxidant by applying a composite coacervation method, the method for producing the microcapsule (1) includes a step of preparing a mixture (x) by mixing the natural essential oil and the antioxidant (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 (x) 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, and the emulsion in the presence of water (this may be referred to as the "emulsion mixing step" in this specification), A step of preparing an acidic mixture (b) by mixing the aforementioned mixture (a) with an acid (this may be referred to as the "acidification step" 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), A manufacturing method (which may be referred to as "manufacturing method (11)" in this specification) is provided, which includes a step of preparing an aqueous dispersion of microcapsules with adjusted pH by mixing the aforementioned mixture (c) with a base.

[0123] The manufacturing method (11) may include, for example, a step (sometimes referred to as an "additional mixing step" in this specification) between the cooling step and the crosslinking agent mixing step, in which the cooled mixture (b) and the second anionic polymer are mixed to produce a mixture (d). Thus, in the manufacturing method (11), the second anionic polymer may be added and mixed into the cooled mixture (b). In other words, the manufacturing method (11) includes the cooling step and 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 manufacturing method may also include a base mixing step of mixing the aforementioned mixture (c) with a base to produce an aqueous dispersion of microcapsules with adjusted pH.

[0124] More specifically, for example, when producing microcapsules (1) containing polyurea as a wall material component, natural essential oil, and the antioxidant by applying an interfacial polycondensation method, the method for producing microcapsules (1) includes a step of adding a second solution containing natural essential oil, the antioxidant, and the polyisocyanate compound to a first solution containing water and an emulsifier to obtain an emulsion (this may be abbreviated as the "emulsification step" in this specification), A manufacturing method (which may be referred to as "manufacturing method (12)" in this specification) is provided, which includes the step of adding the polyamine compound to the emulsified liquid and carrying out a polycondensation reaction (which may be abbreviated as "polycondensation step" in this specification).

[0125] When obtaining polyurea by interfacial polycondensation using the aforementioned natural essential oil, the polyisocyanate compound, and the polyamine compound, the content of the polyisocyanate compound in the second solution may be, for example, preferably 5 to 70 parts by mass, 5 to 60 parts by mass, and 5 to 55 parts by mass, or 40 to 70 parts by mass and 45 to 70 parts by mass, or 40 to 60 parts by mass and 45 to 55 parts by mass, based on 100 parts by mass of the natural essential oil. By having the content of the polyisocyanate compound in such a range, higher quality microcapsules (1) can be obtained.

[0126] When obtaining polyurea by interfacial polycondensation using the aforementioned natural essential oil, the polyisocyanate compound, and the polyamine compound, the amounts used are preferably such that the molar ratio of [moles of amino groups in the polyamine compound] to [moles of isocyanate groups in the polyisocyanate compound] is 10:90 to 60:40, and more preferably 20:80 to 55:45. By setting the number of moles of amino groups in the polyamine compound to be less than the number of moles of isocyanate groups in the polyisocyanate compound, higher quality microcapsules (1) can be obtained.

[0127] Microcapsules (1) in which polyurethane is used as the wall material component instead of polyurea can be manufactured by the same method as in manufacturing method (12), except that the polyhydroxy compound is used instead of the polyamine compound. Microcapsules (1) in which polyamide is used as the wall material component instead of polyurea can be manufactured by the same method as in manufacturing method (12), except that the polycarboxylic acid or carboxylic acid chloride is used instead of the polyisocyanate compound.

[0128] More specifically, for example, when producing a microcapsule (2) containing the lipophilic substance and the antioxidant by applying a composite coacervation method, the method for producing the microcapsule (2) includes a step of preparing a mixture (x) by mixing the lipophilic substance and the antioxidant (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 (x) 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, and the emulsion in the presence of water (this may be referred to as the "emulsion mixing step" in this specification), A step of preparing an acidic mixture (b) by mixing the aforementioned mixture (a) with an acid (this may be referred to as the "acidification step" 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), A manufacturing method (which may be referred to as "manufacturing method (21)") is provided, comprising the step of preparing an aqueous dispersion of microcapsules with adjusted pH by mixing the aforementioned mixture (c) with a base (which may be referred to as the "base mixing step" in this specification).

[0129] The manufacturing method (21) may include, for example, a step (sometimes referred to as an "additional mixing step" in this specification) between the cooling step and the crosslinking agent mixing step, in which the cooled mixture (b) and the second anionic polymer are mixed to produce a mixture (d). Thus, in the manufacturing method (21), the second anionic polymer may be added and mixed into the cooled mixture (b). In other words, the manufacturing method (21) includes the cooling step and 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 manufacturing method may also include a base mixing step of mixing the aforementioned mixture (c) with a base to produce an aqueous dispersion of microcapsules with adjusted pH.

[0130] More specifically, for example, when producing microcapsules (2) containing polyurea as a wall material component, the lipophilic substance, and the antioxidant by applying an interfacial polycondensation method, the method for producing the microcapsules (2) includes a step of adding a second solution containing the lipophilic substance, the antioxidant, and the polyisocyanate compound to a first solution containing water and an emulsifier to obtain an emulsion (this may be abbreviated as the "emulsification step" in this specification), A manufacturing method (sometimes referred to as "manufacturing method (22)") is provided, which includes the step of adding the polyamine compound to the emulsified liquid and carrying out a polycondensation reaction (sometimes abbreviated as "polycondensation step" in this specification).

[0131] When obtaining polyurea by interfacial polycondensation using the lipophilic substance, the polyisocyanate compound, and the polyamine compound, the content of the polyisocyanate compound in the second solution may be, for example, preferably 30 to 70 parts by mass, 30 to 60 parts by mass, and 30 to 55 parts by mass, or 40 to 70 parts by mass and 45 to 70 parts by mass, or 40 to 60 parts by mass and 45 to 55 parts by mass, based on 100 parts by mass of the lipophilic substance. By having the content of the polyisocyanate compound in such a range, higher quality microcapsules (2) can be obtained.

[0132] When obtaining polyurea by interfacial polycondensation using the lipophilic substance, the polyisocyanate compound, and the polyamine compound, the amounts used are preferably such that the molar ratio of [moles of amino groups in the polyamine compound] to [moles of isocyanate groups in the polyisocyanate compound] is 10:90 to 60:40, and more preferably 20:80 to 40:60. By setting the number of moles of amino groups in the polyamine compound to be less than the number of moles of isocyanate groups in the polyisocyanate compound, higher quality microcapsules (2) can be obtained.

[0133] Microcapsules (2) in which polyurethane is used as the wall material component instead of polyurea can be manufactured by the same method as in manufacturing method (22), except that the polyhydroxy compound is used instead of the polyamine compound. Microcapsules (2) using polyamide as a wall material component instead of polyurea can be manufactured by the same method as in manufacturing method (22), except that the polycarboxylic acid or carboxylic acid chloride is used instead of the polyisocyanate compound. [Examples]

[0134] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited in any way to the examples shown below.

[0135] Table 1 shows the natural essential oils (lipophilic substances) used in the following examples and comparative examples. Although all of the natural essential oils shown in Table 1 also correspond to lipophilic substances (I), they are listed here as natural essential oils.

[0136] [Table 1]

[0137] [Example 1] <<Microcapsule Manufacturing (First Embodiment)>> At room temperature (under conditions of 23°C), α-tocopherol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (0.3g) was added to tea tree essential oil (30g), and the mixture was stirred until it became homogeneous to obtain a mixed solution (x) (first mixing step).

[0138] An aqueous solution (130g) of gelatin (Type A, manufactured by Nitta Gelatin Co., Ltd.) with a concentration of 5% by mass was heated to 50°C. The entire amount of the mixture (x) obtained above at room temperature was added to this aqueous solution, and an emulsion was prepared by stirring at a rotation speed of 3000 rpm for 3 minutes at room temperature using an emulsifier (manufactured by Primix Co., Ltd.) (emulsification process).

[0139] An aqueous solution (130 g) of gum arabic (manufactured by Nacalai Tesque, equivalent to a 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 (2g) of an aqueous solution of sodium carboxymethylcellulose (CMC) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., model number 7A, corresponding to a second anionic polymer) at room temperature with a concentration of 10% by mass was added to the mixture obtained above, and the mixture was stirred for 2 minutes to prepare a mixed solution (a) (emulsification mixing step).

[0140] 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). 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). Next, to the mixture (b) being stirred at a temperature of 5°C, an aqueous solution (20g) of carboxymethylcellulose sodium (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., model number 7A, 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, an aqueous solution (2.5 g) of glutaraldehyde (manufactured by Fujifilm Wako Pure Chemical Industries, equivalent to a crosslinking agent) with a concentration of 25% by mass was added at room temperature, and the mixture was stirred for 2 minutes while maintaining the temperature condition of 5°C to prepare the mixture (c) (crosslinking agent mixing step).

[0141] 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 9.0. 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 wall material component comprising gelatin, gum arabic, and sodium carboxymethylcellulose was obtained, along with glutaraldehyde, and microcapsules containing tea tree essential oil and α-tocopherol as core materials, as an aqueous dispersion.

[0142] <<Evaluation of Microcapsules>> <Evaluation of the effect of suppressing oxidative degradation of the core material> 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 2 minutes. Next, a 1cm x 5cm section was cut from the high-quality paper to which the dried microcapsules were attached. Next, the remaining high-quality paper after cutting out the aforementioned sections was placed inside the oven and heated at 60°C for one week. Next, a 1cm x 5cm section was cut from the heated high-quality paper. This section was used as the post-heating test specimen, and the section cut earlier was used as the pre-heating test specimen. These test specimens were separately immersed in acetonitrile (20 mL) and subjected to sufficient ultrasonic stimulation. This caused the components encapsulated in the dried microcapsules that were attached to these test specimens to be eluted into the acetonitrile.

[0143] Next, using a gas chromatograph-mass spectrometer (GC-MS) and octane as an internal standard, terpinen-4-ol, the main component of natural essential oils (lipophilic substances), was quantified from the core material, which is the eluted component in acetonitrile. From this quantification value, the amount (parts by mass) of terpinen-4-ol contained in the microcapsules attached to each test piece before and after heating was calculated, and the remaining percentage (%) of terpinen-4-ol in the microcapsules after heating was calculated using the following formula. This value was then adopted as the "remaining percentage (%) of the main component of the core material after heating." The results are shown in Table 2. [Percentage of terpinen-4-ol remaining in microcapsules after heating (%)] = [Amount of terpinen-4-ol contained in microcapsules attached to the test specimen after heating] / [Amount of terpinen-4-ol contained in microcapsules attached to the test specimen before heating] × 100

[0144] The measurement conditions for the GC-MS are as follows: (GC-MS measurement conditions) ·Measuring device: Agilent “7890B” • Column: Frontier Labs "Ultra ALLOY-5", 30mm length, 0.25mm inner diameter, 0.25μm film thickness • Detector: JEOL Ltd. "JMS-Q1500" • Carrier gas: Helium gas (99.9999%) • Sample injection method: Splitless injection method ·Inlet temperature: 300℃ • Column oven temperature: 40℃~250℃ ·Q-Pole temperature: 70℃ Ion source temperature: 250℃ GC interface temperature: 260℃

[0145] In Table 2, a "-" in the "Microcapsule Composition" column means that the microcapsule does not contain the component listed in that column. Furthermore, in Table 2, the "amount (mass%)" in "antioxidant (amount (mass%))" means "the ratio of the amount (parts by mass) of antioxidant to the amount (parts by mass) of natural essential oil at the time of manufacturing the microcapsules," which is synonymous with "the ratio of the amount (parts by mass) of antioxidant to the amount (parts by mass) of natural essential oil in the microcapsules."

[0146] <<Microcapsule Manufacturing (First Embodiment) and Evaluation>> [Example 2] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that the amount of α-tocopherol used was changed from 0.3 g to 3 g. The results are shown in Table 2.

[0147] [Example 3] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that dibutylhydroxytoluene (manufactured by Tokyo Chemical Industry Co., Ltd.) (0.3g) was used instead of α-tocopherol (0.3g). The results are shown in Table 2.

[0148] [Example 4] Microcapsules were manufactured and evaluated using the same method as in Example 3, except that the amount of dibutylhydroxytoluene used was increased from 0.3 g to 3 g. The results are shown in Table 2.

[0149] [Example 5] <<Microcapsule Manufacturing (Second Embodiment)>> At room temperature, a second solution was prepared by adding α-tocopherol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (4g) and an ethyl acetate solution of trimethylolpropane adduct of trilen-2,4-diisocyanate (hereinafter referred to as "TDI-TMP adduct") with a concentration of 75% by mass (Mitsui Chemicals, Ltd. "Takenate D-103H", 26.7g, 20g as TDI-TMP adduct) to tea tree essential oil (40g), and stirring until the resulting mixture was homogenized.

[0150] 7.5g of polyvinyl alcohol (JP-24, manufactured by Nippon Bi-Val Co., Ltd., degree of saponification: 87-89) was added to 142.5g of distilled water, and the mixture was stirred at 90°C for 1 hour to form a solution. This solution was then cooled to 25°C to obtain a 5% by mass aqueous solution of polyvinyl alcohol (first solution).

[0151] At room temperature, the entire amount of the polyvinyl alcohol aqueous solution (first solution) was added to the entire amount of the second solution obtained above, and an emulsion was prepared by stirring at a rotation speed of 3000 rpm for 3 minutes using an emulsifier (manufactured by Primix Corporation) (emulsification step).

[0152] 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, the reaction mixture was stirred at 80°C for 2 hours to carry out interfacial polycondensation (polycondensation step). 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 encapsulating tea tree essential oil and α-tocopherol as the core material.

[0153] <<Evaluation of Microcapsules>> The microcapsules obtained above were evaluated using the same method as in Example 1. The results are shown in Table 2.

[0154] <<Microcapsule Manufacturing (Second Embodiment) and Evaluation>> [Example 6] Microcapsules were manufactured and evaluated using the same method as in Example 5, except that lemon eucalyptus oil (40g) was used instead of tea tree essential oil (40g), and dibutylhydroxytoluene (manufactured by Tokyo Chemical Industry Co., Ltd.) (4g) was used instead of α-tocopherol (4g). The results are shown in Table 2.

[0155] In this embodiment, since lemon eucalyptus oil was used as the natural essential oil, when evaluating the microcapsules, citronellal, the main component of lemon eucalyptus oil, was quantified as the main component of the natural essential oil (lipophilic substance), instead of terpinen-4-ol, the main component of tea tree essential oil. From this quantified value, the amount of citronellal contained in the microcapsules attached to each test piece before and after heating was calculated, and the residual rate (%) of citronellal in the microcapsules after heating was calculated using the following formula. This value was then adopted as the "residual rate (%) of the main component of the core material after heating." [Percentage of citronellal remaining in microcapsules after heating (%)] = [Amount of citronellal contained in microcapsules attached to the test specimen after heating] / [Amount of citronellal contained in microcapsules attached to the test specimen before heating] × 100

[0156] <<Microcapsule Manufacturing (First Embodiment) and Evaluation>> [Example 7] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that lemon eucalyptus oil (40g) was used instead of tea tree essential oil (40g), and the amount of α-tocopherol used was increased from 0.3g to 3g. The results are shown in Table 2.

[0157] <<Microcapsule Manufacturing (Second Embodiment) and Evaluation>> [Example 8] Microcapsules were manufactured and evaluated using the same method as in Example 6, except that dibutylhydroxytoluene (manufactured by Tokyo Chemical Industry Co., Ltd.) (4g) was used instead of α-tocopherol (4g). The results are shown in Table 2.

[0158] <<Manufacturing and evaluation of comparative microcapsules>> [Comparative Example 1] Microcapsules were manufactured and evaluated in the same manner as in Example 1, except that α-tocopherol was not used. In other words, in this comparative example, the emulsification step was performed in the same manner as in Example 1, except that the first mixing step was omitted and tea tree essential oil (30 g) was used instead of the mixed solution (x). Subsequently, an aqueous dispersion of microcapsules was obtained in the same manner as in Example 1. The results are shown in Table 2.

[0159] [Comparative Example 2] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that propyl gallate (manufactured by Tokyo Chemical Industry Co., Ltd.) (0.3g) was used instead of α-tocopherol (0.3g). The results are shown in Table 2.

[0160] [Comparative Example 3] Microcapsules were manufactured and evaluated using the same method as in Comparative Example 2, except that the amount of propyl gallate used was changed from 0.3 g to 3 g. The results are shown in Table 2.

[0161] [Comparative Example 4] Microcapsules were manufactured and evaluated using the same method as in Example 1, except that β-carotene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (0.3g) was used instead of α-tocopherol (0.3g). The results are shown in Table 2.

[0162] [Comparative Example 5] Microcapsules were manufactured and evaluated using the same method as in Example 6, except that α-tocopherol was not used. The results are shown in Table 2.

[0163] [Comparative Example 6] Microcapsules were manufactured and evaluated using the same method as in Example 6, except that propyl gallate (manufactured by Tokyo Chemical Industry Co., Ltd.) (4g) was used instead of α-tocopherol (4g). The results are shown in Table 2.

[0164] [Comparative Example 7] Microcapsules were manufactured and evaluated using the same method as in Example 6, except that β-carotene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) (4g) was used instead of α-tocopherol (4g). The results are shown in Table 2.

[0165] [Table 2]

[0166] As is clear from the results above, in Examples 1 to 8, the residual rate of the main component of the core material after heating was 85.0% or more (85.0-99.8%), indicating that the microcapsules had a high inhibitory effect on oxidative degradation of the core material, regardless of the manufacturing method of the microcapsules.

[0167] The microcapsules in Examples 1-8 contained either α-tocopherol or dibutylhydroxytoluene as an antioxidant. In the microcapsules of Examples 1 to 8, the main component of the natural essential oil encapsulated together with the antioxidant was terpinen-4-ol or citronellal, which had 9 to 11 carbon atoms and possessed one unsaturated bond between carbon atoms.

[0168] In contrast, in Comparative Examples 1 to 7, the residual rate of the main component of the core material after heating was 79.0% or less (31.1-79.0%), indicating that the microcapsules had a low effect in suppressing oxidative degradation of the core material, regardless of the manufacturing method of the microcapsules.

[0169] The microcapsules in Comparative Examples 1 and 5 did not contain any antioxidants. The microcapsules of Comparative Examples 2, 3, and 6 did not contain α-tocopherol or dibutylhydroxytoluene as antioxidants, but contained propyl gallate. The microcapsules of Comparative Examples 4 and 7 did not contain either α-tocopherol or dibutylhydroxytoluene as antioxidants, but contained β-carotene. [Industrial applicability]

[0170] The present invention can be used as a microcapsule with a lipophilic substance such as a natural essential oil as the core material, and is particularly suitable for use in a dry state.

Claims

1. It is a microcapsule, The aforementioned microcapsules contain natural essential oils and antioxidants through a wall material. The wall material is composed of gelatin, a first anionic polymer, and a second anionic polymer of a different type from the first anionic polymer. Microcapsules in which the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene.

2. It is a microcapsule, The aforementioned microcapsules contain a lipophilic substance and an antioxidant through a wall material. The wall material is composed of gelatin, a first anionic polymer, and a second anionic polymer of a different type from the first anionic polymer. The aforementioned lipophilic substance has 9 to 11 carbon atoms and has one or more unsaturated bonds between carbon atoms, or has one or more formyl groups. Microcapsules in which the antioxidant is one or more selected from the group consisting of tocopherol and dibutylhydroxytoluene.

3. The microcapsule according to claim 2, wherein the lipophilic substance is either terpinen-4-ol or citronellal, or both.

4. The microcapsule according to claim 1, wherein the natural essential oil is either tea tree essential oil or lemon eucalyptus oil, or both.

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