JP7631709B2 - Microcapsules and their manufacturing method - Google Patents

Description

The present invention relates to microcapsules and their manufacturing method.

Microcapsules are constructed by encapsulating a target component as a core substance within a wall material.
One method for manufacturing microcapsules is to apply the coacervation method. The coacervation method is further divided into a simple coacervation method in which the wall material is made of only one type of polymer, and a complex coacervation method in which the wall material is made of two or more types of polymer. In the complex coacervation method, the wall material is made of an anionic polymer and a cationic polymer. The complex coacervation method is suitable for manufacturing microcapsules with a strong wall material.

When manufacturing microcapsules by applying the complex coacervation method, a crosslinking agent is usually applied to the wall material encapsulating the core substance to crosslink the components of the wall material, thereby improving the strength of the microcapsules. However, in the process up to this point, the particle size of the microcapsules finally obtained tends to become large due to aggregation or coalescence of the components of the microcapsules and the wall material during their formation. Such microcapsules with large particle sizes can have limited uses, for example, because they are easily visible to the naked eye.

On the other hand, formaldehyde, glutaraldehyde, etc. are well known as crosslinking agents, and it has been disclosed that their use can be used to produce small microcapsules, for example, with an average particle size of 20 μm or less (see Patent Document 1).

Special table 2015-518031 publication

However, because these crosslinking agents (formaldehyde, glutaraldehyde, etc.) are highly toxic, the microcapsules obtained using these crosslinking agents have low safety for living organisms and cannot be used for purposes that come into contact with the skin (e.g., topical agents, cosmetics, etc.), let alone for consumption.

In response to this, the present inventors have discovered that by using a polyvalent metal salt with low toxicity as a crosslinking agent, and further using a specific range of surfactants, it is possible to obtain microcapsules with a small average particle size and high safety for living organisms. However, there is a problem in that some of these microcapsules have insufficient properties for stably encapsulating a core substance (such properties are referred to as "encapsulation and retention performance" in this specification).

The objective of the present invention is to provide microcapsules that have a small average particle size, are highly safe for living organisms, and have high encapsulation and retention performance.

The present invention provides a microcapsule comprising gelatin, a first anionic polymer, a second anionic polymer different from the first anionic polymer, and polyphenols, wherein the microcapsule encapsulates an oily component, and the average particle size of the microcapsule is 20 μm or less.
In the microcapsules of the present invention, the oily component is preferably a fragrance.

The microcapsules of the present invention may further contain a polyvalent metal salt.
In the microcapsules of the present invention, the polyvalent metal salt may be one or more selected from the group consisting of aluminum salts and zirconium salts.
In the microcapsules of the present invention, it is preferable that the total content of aluminum in the aluminum salt and zirconium in the zirconium salt is 5 to 30 mmol per 100 g of the total content of the gelatin, the first anionic polymer, and the second anionic polymer.
In the microcapsules of the present invention, the polyvalent metal salt may be one or more selected from the group consisting of calcium salts, magnesium salts, barium salts and zinc salts.
In the microcapsules of the present invention, it is preferable that the total content of calcium in the calcium salt, magnesium in the magnesium salt, barium in the barium salt, and zinc in the zinc salt is 20 to 110 mmol per 100 g of the total content of the gelatin, the first anionic polymer, and the second anionic polymer.

The present invention also provides a method for producing microcapsules, comprising the steps of: mixing gelatin and an oily component in the presence of water to prepare an emulsion; mixing a first anionic polymer, a second anionic polymer different from the first anionic polymer, and the emulsion in the presence of water to prepare a mixed liquid (a); mixing the mixed liquid (a) with an acid to prepare an acidic mixed liquid (c); cooling the mixed liquid (c) until its temperature is 10° C. or less; mixing the cooled mixed liquid (c) with the second anionic polymer to prepare a mixed liquid (d); mixing the mixed liquid (d) with a polyphenol to prepare a mixed liquid (e); and mixing the mixed liquid (e) with a base to prepare an aqueous dispersion of microcapsules with an adjusted pH.
In the method for producing microcapsules of the present invention, in the step of preparing the mixed liquid (e), a polyvalent metal salt may be further mixed.

The present invention provides microcapsules that have a small average particle size, are highly safe for living organisms, and have high encapsulation and retention capabilities.

<<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 polyphenols, the microcapsule encapsulating an oily component, and the average particle diameter of the microcapsule is 20 μm or less.

The microcapsules of this embodiment are highly safe for living organisms because highly toxic components such as formaldehyde and glutaraldehyde are not used during their production. The average particle size of the microcapsules of this embodiment is small. The encapsulation and retention performance of the microcapsules of this embodiment is high. The reason why the average particle size of the microcapsules of this embodiment is small, safe for living organisms, and has high encapsulation and retention performance is because the first anionic polymer, the second anionic polymer, and polyphenols are used at appropriate times during their production.

The microcapsules of this embodiment have a high ability to encapsulate and retain the oily component, which is the core substance. For example, the microcapsules have a high ability to maintain the state in which the oily component is encapsulated (in other words, the normal state of the microcapsules) even when in a dry state.

The microcapsules of this embodiment do not contain highly toxic components such as formaldehyde and glutaraldehyde, and are highly safe for living organisms. Therefore, the microcapsules of this embodiment are particularly suitable for use in applications such as skin contact (e.g., topical agents, cosmetics, etc.).

The microcapsules of the present embodiment are configured such that a core substance is encapsulated within a wall material.
The microcapsules can be produced by applying a complex coacervation method, as described below.
The gelatin, the first anionic polymer and the second anionic polymer are components of the wall material of the microcapsules (sometimes abbreviated as "wall material components" in this specification), and form the wall material by a complex coacervation method.

Wall Material and Wall Material Components As described above, the wall material is composed of the gelatin, the first anionic polymer, and the second anionic polymer, and the polyphenols contribute to maintaining the strong structure of the wall material.

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

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

Gelatin is an amphoteric polymer that can be either cationic or anionic, so it is used after being cationized by the action of an acid, as described below.

The gelatin constituting the microcapsules may be of one type or two or more types, and if there are two or more types, the combination and ratio of the gelatin may be selected arbitrarily.

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

The first anionic polymer is not particularly limited as long as it is a polymer having an anionic group.
The first anionic polymer may be, for example, a polymer having a group in which an acid group is dissociated (anionized).
More specifically, examples of the first anionic polymer include a polymer having a group in which a carboxy group (-C(=O)-OH) is dissociated (anionized), i.e., a carboxylate anion (-C(=O)-O ^- ); a polymer having a group in which a sulfo group (-SO ₃ H) is dissociated (anionized) (-SO ₃ ^- ); and the like.
In one molecule of the first anionic polymer, some or all of the anionic groups may form a salt with a cation.

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 having a valence of two or more (a polyvalent metal ion), but is preferably a monovalent metal ion.

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

Examples of the first anionic polymer include gum arabic, alginic acid, sodium alginate, carboxymethylcellulose, sodium carboxymethylcellulose, carrageenan (e.g., iota carrageenan, kappa carrageenan, lambda carrageenan), ring-opened ethylene maleic anhydride copolymer, xanthan gum, and pectin.
The ring-opened product of the ethylene-maleic anhydride copolymer means a product which can be regarded as being obtained by ring-opening the acid anhydride moiety in the structural unit derived from maleic anhydride in the ethylene-maleic anhydride copolymer through hydrolysis.

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 the first anionic polymer.
For example, the molecular weight of gum arabic may be 200,000-2,000,000, the molecular weight of sodium alginate may be 40,000-4,000,000, the molecular weight of sodium carboxymethylcellulose may be 20,000-400,000, the molecular weight of xanthan gum may be 2,000,000-50,000,000, and the molecular weight of pectin may be 50,000-360,000.

In the microcapsules, the content of the first anionic polymer relative to 100 parts by mass of gelatin is preferably 10 to 210 parts by mass, and may be, for example, any of 10 to 190 parts by mass, 10 to 170 parts by mass, 10 to 150 parts by mass, and 10 to 130 parts by mass, or any of 60 to 210 parts by mass, 110 to 210 parts by mass, and 160 to 210 parts by mass, or any of 60 to 190 parts by mass and 110 to 170 parts by mass. By setting the content of the first anionic polymer in such a range, the amount of the first anionic polymer or gelatin that does not contribute to the configuration of the wall material can be reduced.

<Second Anionic Polymer>
The second anionic polymer, like the first anionic polymer, is a polymer having an anionic moiety in its molecule, and serves as a wall material component of the microcapsule together with gelatin.

The second anionic polymer is not particularly limited as long as it is a polymer having an anionic group and is a different type from the first anionic polymer.

In this embodiment, the first anionic polymer and the second anionic polymer are different in type from each other, which means that the polymer portion having an anionic portion of the first anionic polymer and the polymer portion having an anionic portion of the second anionic polymer are different from each other in terms of composition, and it is preferable that one of these polymer portions has a structural unit that the other does not have.

The second anionic polymer can be the same as the first anionic polymer described above.

The molecular weight of the second anionic polymer may be similar to the molecular weight of the second anionic polymer described above.

In the microcapsules, the content of the second anionic polymer relative to 100 parts by mass of gelatin is preferably 3 to 80 parts by mass, and may be, for example, any of 3 to 70 parts by mass, 3 to 60 parts by mass, 3 to 50 parts by mass, and 3 to 40 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 70 parts by mass, and 30 to 60 parts by mass. By setting the content of the second anionic polymer in such a range, the amount of the second anionic polymer or gelatin that does not contribute to the composition of the wall material can be reduced.

The first anionic polymer and the second anionic polymer contained in the microcapsule (in other words, constituting the wall material component) may be only two types in total, or may be three or more types, and the combination and ratio of the first anionic polymer and the second anionic polymer can be selected arbitrarily depending on the purpose.

In this embodiment, for example, when the microcapsule contains only two types of anionic polymers in total, the anionic polymer contained in the microcapsule in a larger amount (parts by mass) is designated as the first anionic polymer, and the anionic polymer contained in the microcapsule in a smaller amount (parts by mass) is designated as the second anionic polymer.

On the other hand, when the microcapsule contains a total of three or more kinds of anionic polymers, the anionic polymers are classified differently depending on whether the calculated ratio of the content (parts by mass) of the anionic polymer _X1 ([content (parts by mass) of the anionic polymer _X1 ]/[total content (parts by mass) _of the anionic polymers]×100) to the total content (parts by mass) of the anionic polymers is 50% by mass or more or less than 50% by mass, for the anionic polymer X1 having the highest content (parts by mass) in the microcapsule. Here, the "total content (parts by mass) of the anionic polymers" refers to the content of all the anionic polymers contained in the microcapsule, and is the sum of the contents of the individual anionic polymers.

When the calculated value is 50% by mass or more, the anionic polymer _X1 is defined as the first anionic polymer, and the other anionic polymer is defined as the second anionic polymer.
On the other hand, if the calculated value is less than 50% by mass, the contents (parts by mass) of the anionic polymers are summed up in descending order of value for each type of anionic polymer to obtain a total value (parts by mass), and the smallest type of anionic polymer whose ratio of the total value to the total content (parts by mass) of the anionic polymers ([total value (parts by mass) obtained by summing up the contents of the anionic polymers in descending order of value]/[total content (parts by mass) of the anionic polymers]×100) is 50% by mass or more is taken as the first anionic polymer. The other anionic polymers are taken as the second anionic polymer. However, multiple types of anionic polymers having the same content (parts by mass) in the microcapsules are treated as equal.
For example, when the composition 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, the anionic polymers _X1 and _X2 are defined as the first anionic polymer, and the anionic polymers _X3 and _X4 are defined as the second anionic polymer. Also, when the composition 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 , the anionic polymers _X1 , _X2 , and _X3 are defined as the first anionic polymer, and the anionic polymer _X4 is defined as the second anionic polymer. In this case, the anionic polymers _X2 and _X3 are not treated as being of the same rank, and one of them is not designated as the first anionic polymer and the other as the second anionic polymer.

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

In the method for producing microcapsules described below, the timing of using the first anionic polymer and the second anionic polymer is important. This point and other aspects of the method for producing microcapsules will be described in detail later.

In the microcapsules, the content of the first anionic polymer relative to 100 parts by mass of the second anionic polymer is preferably 100 to 600 parts by mass, and may be, for example, any of 200 to 600 parts by mass and 300 to 600 parts by mass, any of 100 to 500 parts by mass and 100 to 400 parts by mass, or any of 200 to 500 parts by mass and 300 to 400 parts by mass. When the content is equal to or greater than the lower limit, the yield of the microcapsules is further improved. When the content is equal to or less than the upper limit, the encapsulation and retention performance of the microcapsules is further improved.

In the microcapsules, the total content of the first anionic polymer and the second anionic polymer relative to 100 parts by mass of gelatin is preferably 13 to 290 parts by mass, and may be, for example, any of 13 to 260 parts by mass, 13 to 230 parts by mass, 13 to 200 parts by mass, and 13 to 170 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 equal to or greater than the lower limit, the yield of the microcapsules is further improved. When the total content is equal to or less than the upper limit, the encapsulation and retention performance of the microcapsules is further improved.

The microcapsules contain at least two types of anionic polymers, a first anionic polymer and a second anionic polymer, as their wall material components, which results in a small average particle size and high encapsulation retention performance. For example, if a microcapsule contains only one type of anionic polymer as the wall material component, the microcapsules themselves may aggregate or coalesce, or the wall material components may aggregate or coalesce during the process of forming the microcapsules. In such cases, the microcapsules may not be formed neatly, or even if they are formed, the particle size may be significantly large.

<Polyphenols>
The polyphenols are not particularly limited as long as they have two or more phenolic hydroxyl groups in one molecule, in other words, they have an aromatic ring such as a benzene ring skeleton or a naphthalene ring skeleton, and have two or more hydroxyl groups (—OH) directly bonded to carbon atoms constituting the ring skeleton of the aromatic ring.

It is presumed that a part or all of the polyphenols contribute to binding the wall material components together in the microcapsules. More specifically, it is presumed that the phenolic hydroxyl groups in the polyphenols are interposed between different sites in one molecule of the wall material component, and these sites are connected together by hydrogen bonds or electrical attraction, or that they are interposed between two molecules of the wall material component, and these two molecules are connected together by hydrogen bonds or electrical attraction. That is, it is presumed that the polyphenols exhibit the same action as known crosslinking agents, and in this specification, such polyphenols may be referred to as crosslinking agents. It is presumed that the polyphenols form hydrogen bonds, for example, between the amino group (-NH ₂ ) in gelatin or its hydrogen ion adduct (-NH ₃ ⁺ ).

Examples of the polyphenols include tannic acid, catechin, chlorogenic acid, gallic acid, quinic acid, caffeic acid, etc.

The polyphenols constituting the microcapsules may be of only one type or of two or more types, and when there are two or more types, the combination and ratio of the polyphenols may be selected arbitrarily.

In the microcapsules, the content of polyphenols may be any of 20 to 70 parts by mass, 30 to 60 parts by mass, and 40 to 50 parts by mass, relative to 100 parts by mass of the total content of gelatin, the first anionic polymer, and the second anionic polymer. When the content of polyphenols is equal to or greater than the lower limit, the wall material of the microcapsule becomes stronger. When the content of polyphenols is equal to or less than the upper limit, excessive use of polyphenols is suppressed.

The microcapsules contain polyphenols as a component for strengthening the wall material, so that the average particle size becomes small and the encapsulation retention performance becomes high.
For example, when a polyvalent metal salt that can act as a crosslinking agent is used in place of the entire amount of polyphenols, aggregation or coalescence of the microcapsules themselves may occur, or aggregation or coalescence of the wall material components during the formation of the microcapsules may occur. In such cases, the microcapsules may not be formed neatly, or even if they are formed, the particle size may become significantly large. For example, when aluminum sulfate (Al ₂ (SO ₄ ) ₃ , calcium chloride (CaCl ₂ ), etc. are used as the polyvalent metal salt, this tendency is clearly observed. It is presumed that the cations constituting the polyvalent metal salt are bonded to the anionic groups in the anionic polymer (e.g., the first anionic polymer, the second anionic polymer) by electrical attraction.
Furthermore, when transglutaminase, which is known as a cross-linking agent that cross-links proteins, was used in place of the total amount of polyphenols, a similar tendency was remarkably observed.
Furthermore, the above-mentioned tendency is significantly observed when the total content of the first anionic polymer and the second anionic polymer in the microcapsules is greater than the content of gelatin (cationic polymer).

On the other hand, as explained above, even when the microcapsule contains only one type of anionic polymer as the wall material component, the microcapsule itself may aggregate or coalesce, or the wall material components during the formation process of the microcapsule may aggregate or coalesce. In order to solve such problems, when a nonionic surfactant such as polyoxyethylene polyoxypropylene block polymer is used as the surfactant, microcapsules with a small average particle size are normally formed, but the encapsulation and retention performance of the core substance (oil component, etc.) of the microcapsule may be reduced. Examples of the polyoxyethylene polyoxypropylene block polymer include those represented by the following general formula (G3):
HO-(CH ₂ CH ₂ O) _m2 -(CH ₂ CH(CH ₃ )O) _n2 -(CH ₂ CH ₂ O) _l2 -H (G3)
(In general formula (G3), m2, n2 and l2 each independently represent an integer of 2 or more.) Examples of nonionic surfactants include those having an HLB value of 12 or more. In this specification, the "HLB value" refers to a value calculated by the Griffin method, unless otherwise specified.

<Cationic polymers other than gelatin>
The wall material in the microcapsules may contain a cationic polymer other than gelatin (sometimes referred to as "other cationic polymer" in this specification) as long as the effect of the present invention is not impaired.

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

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

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 microcapsule does not contain the other cationic polymer) relative to 100 parts by mass of the gelatin content. When the content of the other cationic polymer is equal to or less than the upper limit, the average particle size of the microcapsules becomes smaller, the encapsulation retention performance of the microcapsules becomes higher, and the stability of the microcapsules is further improved. In addition, the wall material is formed better.

Oily Component The oily component is the core material in the microcapsules of this embodiment.
In this embodiment, the term "oil component" refers to a component having an SP value (solubility parameter) of 7.0 to 11.0 (cal/cm ³ ) ^1/2 .

The oil component is not particularly limited and can be arbitrarily selected depending on the purpose.
The oil component is preferably an oil at room temperature.
In this specification, "room temperature" means a temperature that is neither particularly cooled nor heated, that is, an ordinary temperature, and examples thereof include temperatures of 15 to 25°C.

Examples of the oily component include animal oils, vegetable oils, and mineral oils.
Examples of the vegetable oil include lavender essential oil, palm oil, palm kernel oil, soybean oil, rapeseed oil, sunflower oil, cottonseed oil, coconut oil, corn oil, sesame oil, castor oil, linseed oil, peanut oil, and olive oil.
Lavender essential oil, for example, contains linalyl acetate and linalool as main components, and also contains minor components such as cis-β-ocimene, trans-β-ocimene, terpinen-4-ol, lavandulyl acetate, 3-octanone, and 3-octanyl acetate.

In terms of their functions, the oily components include, for example, fragrances, insect repellents, insecticides, insect repellents, cosmetics, deodorants, medicines, bactericides, and other chemical reactants. The chemical reactants are components that react with specific chemical substances to inhibit the action of the chemical substances, and do not fall under any of the following categories: fragrances, insect repellents, insecticides, insect repellents, cosmetics, deodorants, medicines, and bactericides.

The components of the microcapsules other than the oily component are highly safe for living organisms, so the excellent effects of the microcapsules are more pronounced when the oily component is a component suitable for use on living organisms.

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

Among the oil-based ingredients, particularly preferred ones include, for example, fragrances.

In the microcapsules, the content of the oily component may be, for example, 400 to 1200 parts by mass or 600 to 1000 parts by mass per 100 parts by mass of gelatin. Microcapsules with the content of the core substance in such a range have better quality and can be manufactured more easily.

The average particle size of the microcapsules is 20 μm or less, preferably 18 μm or less, more preferably 16 μm or less, and may be, for example, any of 14 μm or less, 11 μm or less, 8 μm or less, and 5 μm or less. Microcapsules with such a small average particle size are difficult to visually recognize, so their applications are not limited.

The lower limit of the average particle size of the microcapsules is not particularly limited. For example, microcapsules having an average particle size of preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more can be more easily produced.

The average particle size of the microcapsules can be adjusted as appropriate within a range set by any combination of any of the lower limit values and any of the upper limit values described above. For example, in one embodiment, the average particle size of the microcapsules is preferably 1 to 20 μm, more preferably 2 to 18 μm, and even more preferably 3 to 16 μm, and may be, for example, any of 3 to 14 μm, 3 to 11 μm, 3 to 8 μm, and 3 to 5 μm.

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

The microcapsules can be made to have sustained release properties, gradually releasing the encapsulated oily component to the outside over time. Such microcapsules can sustain the action of the oily component as a core substance for a long period of time.

For example, a microcapsule containing gelatin, a first anionic polymer, a second anionic polymer, and polyphenols, and further containing a polyvalent metal salt, is preferable as it has a higher sustained release property.
The microcapsules contain both the polyphenols and the polyvalent metal salt, rather than the polyvalent metal salt without the polyphenols, and thus have higher sustained release properties without impairing the effects of the present invention.
It is presumed that the polyvalent metal salts, like polyphenols, exert an action similar to that of known crosslinking agents in the microcapsules.

<Polyvalent metal salt>
The polyvalent metal salt is not particularly limited as long as it contains a metal ion having a valence of two or more (polyvalent metal ion) 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 a non-hydrate.

Examples of the polyvalent metal inorganic salt include sulfates such as aluminum sulfate ( _Al2 ( _SO4 ) ₃ ), zirconium sulfate (Zr( _SO4 ) ₂ ), calcium sulfate ( _CaSO4 ), magnesium sulfate ( _MgSO4 ), potassium aluminum sulfate (potassium alum, AlK( _SO4 ) ₂ ) _{, and ammonium aluminum sulfate (ammonium alum, AlNH4(SO4)3 ) ;} hydrochlorides such as calcium chloride ( _CaCl2 ), magnesium chloride ( _MgCl2 ), aluminum chloride ( _AlCl3 ), barium chloride ( _BaCl2 ), and zinc chloride ( _ZnCl2 ); and nitrates such as calcium nitrate (Ca( _NO3 ) ₂ ).

Examples of the polyvalent metal organic salt include acetates such as magnesium acetate ((CH ₃ COO) ₂ Mg) and calcium acetate ((CH ₃ COO) ₂ Ca).

The polyvalent metal salt, whether an inorganic polyvalent metal salt or an organic polyvalent metal salt, may include aluminum salts (Al salts), zirconium salts (Zr salts), calcium salts (Ca salts), magnesium salts (Mg salts), barium salts (Ba salts), zinc salts (Zn salts), and the like.
For example, potassium aluminum sulfate and ammonium aluminum sulfate are classified as aluminum salts.

The multivalent metal salt constituting the microcapsules may be of only one type, or of two or more types. If there are two or more types, the combination and ratio of the salts may be selected arbitrarily.

Preferred examples of the polyvalent metal salt containing a divalent metal ion as a constituent component include one or more types selected from the group consisting of aluminum salts and zirconium salts.
Preferred examples of the polyvalent metal salts containing metal ions with a valence of three or more as a constituent include one or more selected from the group consisting of calcium salts, magnesium salts, barium salts and zinc salts.

The content of the polyvalent metal salt in the microcapsules can be adjusted as appropriate, for example, depending on the type of polyvalent metal salt.

In the case of the polyvalent metal salt having a divalent metal ion as a constituent component, the content of the metal in the polyvalent metal salt is preferably 20 to 110 mmol, more preferably 23 to 106 mmol, per 100 g of the total content of the gelatin, the first anionic polymer, and the second anionic polymer in the microcapsule. When the content is equal to or greater than the lower limit, the sustained release properties of the microcapsules are improved. When the content is equal to or less than the upper limit, the average particle size of the microcapsules is smaller.
For example, when the polyvalent metal salt is one or more selected from the group consisting of calcium salts, magnesium salts, barium salts and zinc salts, the total content of calcium in the calcium salt, magnesium in the magnesium salt, barium in the barium salt, and zinc in the zinc salt per 100 g of the total content of gelatin, the first anionic polymer, and the second anionic polymer in the microcapsules is preferably 20 to 110 mmol, and more preferably 23 to 106 mmol.

In the case of the polyvalent metal salt having a metal ion with a valence of 3 or more as a constituent, the content of the metal in the polyvalent metal salt is preferably 5 to 30 mmol, more preferably 5.5 to 29 mmol, per 100 g of the total content of gelatin, the first anionic polymer, and the second anionic polymer in the microcapsule. When the content is equal to or more than the lower limit, the sustained release property of the microcapsule is higher. When the content is equal to or less than the upper limit, the average particle size of the microcapsule is smaller.
For example, when the polyvalent metal salt is one or more selected from the group consisting of aluminum salts and zirconium salts, the total content of aluminum in the aluminum salt and zirconium in the zirconium salt per 100 g of the total content of gelatin, the first anionic polymer, and the second anionic polymer in the microcapsules is preferably 5 to 30 mmol, and more preferably 5.5 to 29 mmol.

The degree of sustained release of the microcapsules can be determined, for example, by the remaining percentage (volume %) of the core material in the microcapsules, calculated from the amount of the core material in the microcapsules before and after heat treatment.

The remaining ratio (volume %) of the core material in the microcapsules can be calculated by the method shown below.
That is, at room temperature, an aqueous dispersion of the target microcapsules is dropped onto a filter paper, and the filter paper on which the drop has been dropped is heat-treated at 40° C. for 2 hours. The residue on the filter paper after the heat treatment is extracted with acetonitrile, and the obtained extract is analyzed by high performance liquid chromatography (HPLC). The amount of the core substance in the extract is quantified, and the following formula (i):
[Residual rate of core material in microcapsules (volume %)] = [Amount of core material in extract extracted from residue on filter paper after heat treatment (volume parts)] / [Amount of core material on filter paper before heat treatment (volume parts)] × 100 (i)
This allows the residual ratio (volume %) of the core material in the microcapsules to be calculated.
The amount (volume parts) of the core substance in the extract can be quantified by preparing a calibration curve for the core substance in advance by HPLC according to a known method and using this calibration curve.
The amount (part by volume) of the core material on the filter paper before the heat treatment can be calculated from the amount of microcapsules in the aqueous dispersion to be heat treated and the amount of the aqueous dispersion dropped onto the filter paper.

Microcapsules in which the residual ratio of the core substance is 30% by volume or more can be judged to be particularly excellent in sustained release properties.
The remaining ratio of the core substance in the microcapsules may be, for example, any one of 35 vol. % or more, 40 vol. % or more, 45 vol. % or more, and 50 vol. % or more.
On the other hand, in order to easily produce microcapsules that are capable of fully expressing the functions of the core substance, it is preferable that the remaining ratio of the core substance in the microcapsules is 70% by volume or less.

The microcapsules can be produced by applying a complex coacervation method, as described below. The microcapsules of this embodiment produced in this manner have stronger walls than microcapsules produced by applying a simple coacervation method.

<<Method of manufacturing microcapsules>>
A method for producing microcapsules according to one embodiment of the present invention includes the steps of: preparing an emulsion by mixing gelatin and an oily component in the presence of water (sometimes referred to as an "emulsification step" in this specification);
A step of preparing a mixed liquid (a) by mixing a first anionic polymer, a second anionic polymer different from the first anionic polymer, and the emulsion in the presence of water (sometimes referred to as an "emulsion mixing step" in this specification);
A step of preparing an acidic mixed solution (c) by mixing the mixed solution (a) with an acid (sometimes referred to as an "acidification step" in this specification);
A step of cooling the mixed liquid (c) until its temperature becomes 10° C. or less (in this specification, this step may be referred to as a “cooling step”);
a step of preparing a mixed solution (d) by mixing the cooled mixed solution (c) with the second anionic polymer (hereinafter, this step may be referred to as an "additional mixing step");
A step of preparing a mixed liquid (e) by mixing the mixed liquid (d) with polyphenols (hereinafter, this step may be referred to as a "polyphenols mixing step");
The method also includes a step of preparing an aqueous dispersion of microcapsules having an adjusted pH by mixing the mixed liquid (e) with a base (sometimes referred to as a "base mixing step" in this specification).

The above-mentioned manufacturing method is a method for manufacturing microcapsules that applies the complex coacervation method, and this method can satisfactorily manufacture the above-mentioned microcapsules of the present invention.

<Emulsification process>
In the emulsification step, gelatin and an oily component are mixed in the presence of water to prepare an emulsion.
The emulsion contains gelatin, water, and an oil component.

The gelatin and oily components used in the emulsification process have been described above, and detailed description thereof will be omitted here.

The gelatin and oily components used in the emulsification process may each be one type only, or two or more types. If two or more types are used, the combination and ratio of the two or more types can be selected arbitrarily.

In the emulsification process, for example, gelatin, water, and an oily component may be mixed, or an aqueous gelatin solution and an oily component may be mixed. When an aqueous gelatin solution is mixed, water may or may not be mixed in addition to the water in the aqueous gelatin solution.

In the emulsification process, the order in which the gelatin, water, and oil component are mixed is not particularly limited, and the order in which the gelatin aqueous solution, the oil component, and water, if necessary, are mixed is also not particularly limited.

In the emulsification process, it is preferable to mix the gelatin aqueous solution, the oil component, and, if necessary, water. In this way, it is possible to produce the emulsion with higher uniformity.

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

In this embodiment, the "gelatin concentration of 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." Here, gelatin has been used as an example, but the concentrations of aqueous solutions of other components are similar.

The water used in the emulsification step and the aqueous gelatin solution may both be heated. By heating the water or the aqueous gelatin solution, the emulsion can be prepared with higher uniformity.
The heating temperature of the water and gelatin aqueous solution is preferably 40 to 75° C., and more preferably 40 to 60° C. When the heating temperature is equal to or higher than the lower limit, the effect of heating is more pronounced. When the heating temperature is equal to or lower than the upper limit, the effect of suppressing adverse effects caused by heating, such as deterioration of gelatin or oily components, is more enhanced.

When the gelatin aqueous solution and oil component are mixed, the oil component may be added to the gelatin aqueous solution, or the gelatin aqueous solution may be added to the oil component. When the oil component is added to the gelatin aqueous solution, the oil component may be added to the gelatin aqueous solution all at once, or may be added in portions or dropwise. When the gelatin aqueous solution is added to the oil component, the gelatin aqueous solution may be added to the oil component all at once, or may be added dropwise.

In the emulsification step, the amount of water used is preferably 10 to 30 times by mass, and more preferably 15 to 25 times by mass, the amount of gelatin used. When the amount of water used is equal to or more than the lower limit, the effect of using water is enhanced, such as the ability to prepare an emulsion with higher uniformity. When the amount of water used is equal to or less than the upper limit, excessive use of water is suppressed.
Here, the amount of water used refers to the amount of water when gelatin, water, and an oily component are combined; it refers to the amount of water in the aqueous gelatin solution when an aqueous gelatin solution and an oily component are combined without additional water; and it refers to the total amount of water in the aqueous gelatin solution and the additional water when an aqueous gelatin solution, an oily component, and additional water are combined.

In the emulsification process, the amount of oily component used is preferably 4 to 12 times, and more preferably 6 to 10 times, the amount of gelatin used. By using the oily component in such a range, it is easier to produce microcapsules of better quality.

In the emulsification step, other components that do not fall into the category of gelatin, water, or oily components (sometimes referred to as "other components (01)" in this specification) may be mixed in as long as the effects of the present invention are not impaired.

The other component (01) is not particularly limited and can be selected arbitrarily depending on the purpose.
The other component (01) used in the emulsification step may be one type or two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily.

In the emulsification step, the amount of the other component (01) used is not particularly limited and can be appropriately adjusted depending on the type of the other component (01).
Typically, in the emulsification process, the ratio of the amount of other component (01) used to the total amount of gelatin, water, and oil component used ([amount of other component (01) used]/([amount of gelatin used]+[amount of water used]+[amount of oil component 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. When the ratio is within such a range, microcapsules with a smaller average particle size and higher encapsulation retention performance can be obtained.
Here, the amount of water used is as described above.

In the emulsification process, the gelatin, oil component, and, if necessary, other components (01) are mixed in the presence of water at a temperature of preferably 15 to 75°C, and more preferably 18 to 60°C.

The method for mixing gelatin, an oil component, and, if necessary, other components (01) in the presence of water is not particularly limited, and examples thereof include a method in which these components are mixed by rotating a stirring means such as a stirring bar or a stirring blade.
The stirring speed of the stirring means may be, for example, either 5000 to 15000 rpm or 7500 to 12500 rpm, but is not limited thereto. For example, such a stirring speed is particularly suitable when the amount of gelatin used is 5 to 15 g. However, the amount of gelatin used is not limited thereto. In addition, such a stirring speed is preferably applied at least in the present process after the gelatin, the oil component, and, if necessary, other components (01) are all mixed in the presence of water.

In the emulsification process, when the remaining components are added to any of the gelatin or gelatin aqueous solution, the oil component, and water as necessary, and other components (01) as necessary, 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 after all the components have been mixed, the mixture may be stirred.

In the emulsification process, after mixing all the components (gelatin or gelatin aqueous solution, oil component, water if necessary, and other components (01) if necessary), the mixture is stirred for a period of preferably 1 to 30 minutes, and more preferably 1 to 10 minutes.

In the emulsification process, for example, it is preferable to prepare an emulsion by adding the oil component alone to a heated aqueous gelatin solution, and it is also possible to prepare an emulsion by adding the oil component alone at room temperature to a heated aqueous gelatin solution.

<Emulsion mixing process>
In the emulsion mixing step, a first anionic polymer, a second anionic polymer, and the emulsion are mixed in the presence of water to prepare a mixed liquid (a).
The mixed liquid (a) contains a first anionic polymer, a second anionic polymer, gelatin, water, and an oil component.

By using the first anionic polymer and the second anionic polymer in combination in the emulsion mixing process, aggregation or coalescence of the wall material components in the process of forming the microcapsules is suppressed until the additional mixing process described below.

The first anionic polymer and the second anionic polymer used in the emulsion mixing process have been described above, and detailed description thereof will be omitted here.

The first anionic polymer and the second anionic polymer used in the emulsion mixing step may each be only one type, or two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily.
The method for classifying the first anionic polymer and the second anionic polymer is as described above.

In the emulsion mixing step, for example, a first anionic polymer, a second anionic polymer, water, and the emulsion may be mixed, a first anionic polymer aqueous solution, a second anionic polymer, and the emulsion may be mixed, a first anionic polymer, a second anionic polymer aqueous solution, and the emulsion may be mixed, or a first anionic polymer aqueous solution, a second anionic polymer aqueous solution, and the emulsion may be mixed. When the first anionic polymer aqueous solution or the second anionic polymer aqueous solution is mixed, water may or may not be mixed separately in addition to the water in the first anionic polymer aqueous solution or the second anionic polymer aqueous solution.

In the emulsion mixing process, the order in which the first anionic polymer or its aqueous solution, the second anionic polymer or its aqueous solution, the emulsion, and, if necessary, water are mixed is not particularly limited.

In the emulsion mixing step, it is preferable to mix the first anionic polymer aqueous solution, the second anionic polymer aqueous solution, the emulsion, and, if necessary, water. In this way, a more uniform mixed solution (a) can be produced.

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

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

The water, the first anionic polymer aqueous solution, and the second anionic polymer aqueous solution used in the emulsion mixing step may all be heated. By heating the water, the first anionic polymer aqueous solution, or the second anionic polymer aqueous solution, a more uniform mixed solution (a) can be prepared.
The heating temperature of the water, the first anionic polymer aqueous solution, and the second anionic polymer aqueous solution is preferably 40 to 75° C., and more preferably 40 to 60° C. When the heating temperature is equal to or higher than the lower limit, the effect of heating is more pronounced. When the heating temperature is equal to or lower than the upper limit, the effect of suppressing adverse effects caused by heating, such as deterioration of the first anionic polymer, the second anionic polymer, gelatin, or oily components, is more enhanced.

When the first anionic polymer aqueous solution or the second anionic polymer aqueous solution is blended, the blending target 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 blending target. When the blending target is added to the first anionic polymer aqueous solution or the second anionic polymer aqueous solution, the blending target may be added to the first anionic polymer aqueous solution or the second anionic polymer aqueous solution all at once, or may be added in portions or dropped. When the first anionic polymer aqueous solution or the second anionic polymer aqueous solution is added to the blending target, the first anionic polymer aqueous solution or the second anionic polymer aqueous solution may be added to the blending target all at once, or may be dropped.

In the emulsion mixing step, the amount of water used is preferably 9 to 21 times, and more preferably 12 to 18 times, the total amount of the first anionic polymer and the second anionic polymer used. When the amount of water used is equal to or greater than the lower limit, the effect of using water is enhanced, such as producing a more uniform mixed liquid (a). When the amount of water used is equal to or less than the upper limit, excessive use of water is suppressed.

The amount of water used herein refers to the amount of water when the first anionic polymer, the second anionic polymer, water, and the emulsion are mixed together.
In addition, in the case where the first anionic polymer aqueous solution, the second anionic polymer, and the emulsion are mixed together without adding additional water, the amount of water is the amount of water in the first anionic polymer aqueous solution.
Furthermore, in the case where a first anionic polymer aqueous solution, a second anionic polymer, the emulsion, and additional water are mixed together, the amount is the total amount of water in the first anionic polymer aqueous solution and the amount of water mixed separately therefrom.
In addition, in the case where the first anionic polymer, the second anionic polymer aqueous solution, and the emulsion are mixed together without adding additional water, the amount of water is the amount of water in the second anionic polymer aqueous solution.
Furthermore, in the case where a first anionic polymer, a second anionic polymer aqueous solution, the emulsion, and additional water are mixed together, the amount of water is the total amount of water in the second anionic polymer aqueous solution and the amount of water mixed separately.
In addition, when a first anionic polymer aqueous solution, a second anionic polymer aqueous solution, and the emulsion are mixed together without adding additional water, the amount of water is the total amount of water in the first anionic polymer aqueous solution and the second anionic polymer aqueous solution.
Furthermore, in the case where a first anionic polymer aqueous solution, a second anionic polymer aqueous solution, the emulsion, and additional water are mixed together, the amount of water is the total amount of water in the first anionic polymer aqueous solution, the water in the second anionic polymer aqueous solution, and the water mixed separately from these.

In the emulsion mixing step, the amount of the first anionic polymer used is preferably 0.1 to 2.1 times by mass relative to the amount of gelatin in the emulsion, and may be, for example, any of 0.1 to 1.9 times by mass, 0.1 to 1.7 times by mass, 0.1 to 1.5 times by mass, and 0.1 to 1.3 times by mass, or any of 0.6 to 2.1 times by mass, 1.1 to 2.1 times by mass, and 1.6 to 2.1 times by mass, or any of 0.6 to 1.9 times by mass, and 1.1 to 1.7 times by mass. By using the first anionic polymer in 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.

In the emulsion mixing step, the amount of the second anionic polymer used is, for example, preferably 0.01 to 0.6 times, and more preferably 0.05 to 0.3 times, the amount of gelatin in the emulsion.

In the emulsion mixing step, other components that do not fall into any of the following categories (gelatin, the first anionic polymer, the second anionic polymer, water, and the oil component) (sometimes referred to as "other components (02)" in this specification) may be mixed in as long as the effects of the present invention are not impaired.

The other component (02) is not particularly limited and can be selected arbitrarily depending on the purpose.
The other component (02) used in the emulsion mixing step may be only one type, or may be two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily.

In the emulsion mixing step, the amount of the other component (02) used is not particularly limited and can be appropriately adjusted depending on the type of the other component (02).
Typically, in the emulsion mixing step, the ratio of the amount of the other component (02) used to the total amount of the first anionic polymer, the second anionic polymer, water, and the emulsion used ([amount of other component (02) used]/([amount of the first anionic polymer used]+[amount of the second anionic polymer used]+[amount of water used]+[amount of the emulsion 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 having the ratio in such a range, microcapsules with a smaller average particle size and higher encapsulation retention performance can be obtained.
Here, the amount of water used is as described above.

In the emulsion mixing step, the first anionic polymer, the second anionic polymer, the emulsion, and, if necessary, other components (02) are mixed in the presence of water at a temperature of preferably 30 to 75°C, and more preferably 40 to 60°C.

The method for mixing the first anionic polymer, the second anionic polymer, the emulsion, and, if necessary, other components (02) in the presence of water is not particularly limited, and may be the same as or different from the method for mixing the gelatin, the oil component, and, if necessary, other components (01) in the presence of water in the above-mentioned emulsification process.

In the emulsion mixing step, when adding the remaining components to any of the additives, which are the first anionic polymer or its aqueous solution, the second anionic polymer or its aqueous solution, the emulsion, water if necessary, and other components (02) if necessary, the remaining components may be added while stirring the additives, or the remaining components may be added without stirring the additives, and after all the components have been mixed, the mixture may be stirred.

In the emulsion mixing step, after mixing all the components (the first anionic polymer or its aqueous solution, the second anionic polymer or its aqueous solution, the emulsion, water separately as required, and other components (02) as required), the mixture is stirred for a time of preferably 1 to 30 minutes, more preferably 1 to 10 minutes.

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

<Acidification step>
In the acidification step, the mixed solution (a) is mixed with an acid to prepare an acidic mixed solution (c).
The gelatin in the mixed liquid (a) does not have any cationic groups and therefore cannot be considered as a cationic polymer, or even if it has cationic groups, the number of groups is so small that it does not have sufficient properties as a cationic polymer.
In contrast, the gelatin in the mixed solution (c) has a sufficiently large number of cationic groups due to the action of the acid, and is in a state in which it fully possesses the properties of a cationic polymer, and is clearly a cationic polymer.
That is, the mixed liquid (c) contains gelatin (cationic polymer), a first anionic polymer, a second anionic polymer, water, and an oil component.

The acid used in the acidification step is not particularly limited and may be, for example, either an inorganic acid or an organic acid.
Examples of the inorganic acid include hydrochloric acid (HCl), sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ), and phosphoric acid (H ₃ PO ₄ ).
Examples of the organic acid include citric acid (HOOCCH ₂ C(COOH)(OH)CH ₂ COOH) and acetic acid (CH ₃ COOH).

The acid used in the acidification step may be one type only, or two or more types. If two or more types are used, the combination and ratio of the acids may be selected arbitrarily.

In the acidification step, the acid may be added alone or as an aqueous solution. By using an aqueous acid solution, it becomes easier to prepare the mixture (c) with an adjusted pH.

The acid concentration of the aqueous acid solution used in the acidification step can be adjusted appropriately depending on the type of acid, but is preferably 10 to 70% by mass, and more preferably 30 to 60% by mass.

When the aqueous acid solution is mixed with the mixed liquid (a), it is preferable to add the aqueous acid solution to the mixed liquid (a). The aqueous acid solution may be added to the mixed liquid (a) all at once or dropwise.
When the acid is not added as an aqueous solution, it is preferable to add the acid to the mixed liquid (a). The acid may be added to the mixed liquid (a) all at once, or may be added dropwise or in portions.

In the acidification step, other components that do not fall into any of the following categories (gelatin, the first anionic polymer, the second anionic polymer, the oil component, and the acid) (sometimes referred to as "other components (03)" in this specification) may be mixed in as long as the effects of the present invention are not impaired.

The other component (03) is not particularly limited and can be selected arbitrarily depending on the purpose, and may be, for example, water. That is, in the acidification step, regardless of whether the acid is added alone or as an aqueous solution, water may be added separately as the other component (03). In this specification, water as the other component (03) may be referred to as "water (03)".

When water (03) is used, for example, the mixed liquid (a) is mixed with an acid or an acid aqueous solution to prepare an acidic mixed liquid (b), and then the acidic mixed liquid (b) and water (03) are mixed to prepare an acidic mixed liquid (c).
In addition, in the case of using water (03), for example, the mixed liquid (a) is mixed with water (03) to dilute the mixed liquid (a), and then the diluted mixed liquid (a) is mixed with an acid or an aqueous acid solution, thereby preparing an acidic mixed liquid (c).

The other component (03) used in the acidification step may be one type only, or two or more types. If there are two or more types, the combination and ratio of these can be selected arbitrarily.

In the acidification step, the amount of the other component (03) used is not particularly limited and can be appropriately adjusted depending on the type of the other component (03).
For example, when the other component (03) is a component other than water, the ratio of the amount of the other component (03) used to the total amount of the mixed liquid (a) and the acid used in the acidification step ([amount of the other component (03) used]/([amount of the mixed liquid (a) used]+[amount of the 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 having this ratio be equal to or less than the upper limit, microcapsules having a smaller average particle size and higher encapsulation retention performance can be obtained.
The amount of acid used herein refers to the amount of acid when the acid is not added as an aqueous solution, and refers to the amount of acid in the aqueous acid solution when the acid is added as an aqueous solution.

On the other hand, when the other component (03) is water, the ratio of the amount of water (03) used to the total amount of the mixed liquid (a) and the acid or aqueous acid solution used in the acidification step ([amount of water (03) used]/([amount of mixed liquid (a) used]+[amount of acid or aqueous acid solution used])×100) is preferably 10 to 100% by mass, and may be, for example, any one of 20 to 90% by mass, 30 to 80% by mass, and 40 to 70% by mass. When the ratio is equal to or more than the lower limit, the effect of using water can be more significantly obtained. When the ratio is equal to or less than the upper limit, excessive use of water is suppressed.
The amount of acid used here is the same as above.

In the acidification step, when the mixed solution (a), the acid or the aqueous acid solution, and, if necessary, another component (03) are mixed, the mixing is preferably carried out under a temperature condition of 30 to 75°C, and more preferably under a temperature condition of 40 to 60°C.
For example, when water (03) is used, it is preferable to mix water (03) adjusted (heated) to such a temperature.

The method for mixing the mixed liquid (a), the acid or the aqueous acid solution, and, if necessary, the other component (03) is not particularly limited, and may be the same as or different from the method for mixing the gelatin, the oil component, and, if necessary, the other component (01) in the presence of water in the above-mentioned emulsification process.

In the acidification step, when adding the remaining components to any of the components to be added, namely, the mixed liquid (a), the acid or the aqueous acid solution, and, if necessary, other components (03), the remaining components may be added while stirring the components to be added, or the remaining components may be added without stirring the components to be added, so that all the components are mixed and then the mixture is stirred.

In the acidification step, after all the components (mixture (a), acid or aqueous acid solution, and other components (03) as necessary) are mixed, the resulting mixture may be stirred for, for example, 1 to 10 minutes.

In the acidification step, for example, it is preferable to prepare the acidic mixed liquid (c) by adding or dropping an aqueous acid solution to the mixed liquid (a), and it is more preferable to prepare the acidic mixed liquid (c) by dropping an aqueous acid solution to the mixed liquid (a).
When water (03) is used, it is preferable to prepare an acidic mixed liquid (c) by adding or dropping the water (03) onto the object.

The minimum pH value exhibited by the liquid containing gelatin, the first anionic polymer, and the second anionic polymer from the start to the end of the acidification step is preferably 2 to 5, and more preferably 2 to 4. When the minimum pH value is equal to or less than the upper limit, the gelatin forms a wall material more stably together with the first anionic polymer and the second anionic polymer. When the minimum pH value is equal to or more than the lower limit, an excessive decrease in pH of the liquid is avoided.
The liquid may be, for example, the mixed liquid (c) or a mixed liquid at an intermediate stage prior to obtaining the mixed liquid (c).

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

The temperature of the mixed liquid (c) during cooling is preferably 0 to 10°C, and more preferably 2 to 9°C. When the temperature is equal to or lower than the upper limit, the cooling effect of the mixed liquid (c) is more pronounced. When the temperature is equal to or higher than the lower limit, excessive cooling of the mixed liquid (c) is suppressed.

The cooling rate of the mixed liquid (c) is not particularly limited, but is preferably 0.2 to 2.0°C/min, and more preferably 0.3 to 1.0°C/min. By keeping the cooling rate within this range, the cooling effect of the mixed liquid (c) can be more pronounced.

<Additional mixing process>
In the additional mixing step, the cooled mixed liquid (c) and the second anionic polymer are mixed to prepare a mixed liquid (d). That is, in this step, the second anionic polymer is additionally mixed into the cooled mixed liquid (c).
The mixed liquid (d) contains gelatin (cationic polymer), a first anionic polymer, a second anionic polymer, water, and an oil component.

In this embodiment, in addition to blending the second anionic polymer in the emulsion mixing step, the second anionic polymer is also blended in the additional mixing step, thereby suppressing the aggregation or coalescence of the microcapsules themselves and the aggregation or coalescence of the wall material components in the process of forming the microcapsules in the subsequent steps, thereby obtaining microcapsules with a small average particle size.

The second anionic polymer used in the additional mixing step has been described above, and detailed description thereof will be omitted here.

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.

The second anionic polymer used in the additional mixing step may be one type or two or more types, and if two or more types are used, the combination and ratio of the polymers may be selected arbitrarily.

The mass ratio of [the amount (parts by mass) of the second anionic polymer used in the emulsion mixing step]:[the amount (parts by mass) of the second anionic polymer used in the additional mixing step] is preferably 75:25 to 25:75, and may be, for example, any of 68:32 to 32:68, 61:39 to 39:61, and 55:45 to 45:55. By having the mass ratio in such a range, microcapsules having a smaller average particle size can be obtained.
In the polyphenol mixing step described below, when a polyvalent metal salt is mixed, the mass ratio is preferably 75:25 to 25:75, but may be, for example, any of 60:40 to 25:75, 50:50 to 25:75, and 40:60 to 25:75. Even when the mass ratio is in such a range, microcapsules with a smaller average particle size can be obtained while using a polyvalent metal salt in combination.

The total amount of the second anionic polymer used in the additional mixing step and the emulsion mixing step (the total amount of the second anionic polymer used in the additional mixing step and the emulsion mixing step) is preferably 0.03 to 0.8 times by mass relative to the amount of gelatin used, and may be, for example, 0.03 to 0.7 times by mass, 0.03 to 0.6 times by mass, 0.03 to 0.5 times by mass, or 0.03 to 0.4 times by mass, or 0.1 to 0.8 times by mass, 0.3 to 0.8 times by mass, or 0.5 to 0.8 times by mass, or 0.1 to 0.7 times by mass, or 0.3 to 0.6 times by mass. By keeping the total amount used in such a range, the amount of the second anionic polymer or gelatin that does not contribute to the composition of the wall material can be reduced.

The amount of the first anionic polymer used in the emulsion mixing step is preferably 1 to 6 times by mass relative to the total amount of the second anionic polymer used in the additional mixing step and the emulsion mixing step (the total amount of the second anionic polymer used in the additional mixing step and the second anionic polymer used in the emulsion mixing step), and may be, for example, 2 to 6 times by mass or 3 to 6 times by mass, 1 to 5 times by mass or 1 to 4 times by mass, or 2 to 5 times by mass or 3 to 4 times by mass. When the amount used is equal to or greater than the lower limit, the yield of the microcapsules is further improved. When the amount used is equal to or less than the upper limit, the encapsulation and retention performance of the microcapsules is further improved.

The total amount of the first anionic polymer used in the emulsion mixing process and the total amount of the second anionic polymer used in the additional mixing process and the emulsion mixing process (the total amount of the first anionic polymer used in the emulsion mixing process, the second anionic polymer used in the additional mixing process, and the second anionic polymer used in the emulsion mixing process) is preferably 0.13 to 2.9 times by mass relative to the amount of gelatin used, and may be, for example, 0.13 to 2.6 times by mass, 0.13 to 2.3 times by mass, 0.13 to 2 times by mass, or 0.13 to 1.7 times by mass, or 0.7 to 2.9 times by mass, 1.4 to 2.9 times by mass, or 2.1 to 2.9 times by mass, or 0.7 to 2.6 times by mass, or 1.4 to 2.3 times by mass. When the total amount is equal to or greater than the lower limit, the yield of microcapsules is further improved. By keeping the total amount below the upper limit, the encapsulation and retention performance of the microcapsules is improved.

In the additional mixing step, for example, the second anionic polymer may be mixed with the cooled mixed liquid (c), or the second anionic polymer aqueous solution may be mixed with the cooled mixed liquid (c). And, regardless of whether the second anionic polymer is mixed alone or as an aqueous solution, water may or may not be mixed separately.

In the additional mixing step, the order in which the second anionic polymer or its aqueous solution, the cooled mixed liquid (c), and water, if necessary, are mixed is not particularly limited.

In the additional mixing step, it is preferable to mix the second anionic polymer aqueous solution, the cooled mixed liquid (c), and water, if necessary. In this way, a more uniform mixed liquid (d) can be produced.

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

When blending the second anionic polymer aqueous solution, the blending target may be added to the second anionic polymer aqueous solution, or the second anionic polymer aqueous solution may be added to the blending target. When adding the blending target to the second anionic polymer aqueous solution, the blending target may be added to the second anionic polymer aqueous solution all at once, or may be added in portions or dropped. When adding the second anionic polymer aqueous solution to the blending target, the second anionic polymer aqueous solution may be added to the blending target all at once, or may be added dropwise.

In the additional mixing step, other components that do not fall into any of the following categories (gelatin, the first anionic polymer, the second anionic polymer, water, an oil component, and an acid) (sometimes referred to as "other components (04)" in this specification) may be mixed in as long as the effects of the present invention are not impaired.

The other component (04) is not particularly limited and can be selected arbitrarily depending on the purpose.
The other component (04) used in the additional mixing step may be only one type, or may be two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily.

In the additional mixing step, the amount of the other component (04) used is not particularly limited and can be appropriately adjusted depending on the type of the other component (04).
Typically, in the additional mixing step, the ratio of the amount of the other component (04) used to the total amount of the second anionic polymer and the cooled mixed liquid (c) used ([amount of the other component (04) used]/([amount of the second anionic polymer used]+[amount of the cooled mixed liquid (c) 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 having the ratio within such a range, microcapsules with a smaller average particle size and higher encapsulation retention performance can be obtained.

The additional mixing step is usually carried out immediately and consecutively following the cooling step.
Therefore, the temperature of the mixed liquid (c) at the start of the additional mixing step is the same as the temperature of the mixed liquid (c) at the end of the cooling step.

In the additional mixing step, the mixing of the second anionic polymer or its aqueous solution, the cooled mixed liquid (c), and, if necessary, other components (04) 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 match the temperature range of the mixed liquid (c) in the cooling step.

The method for mixing the second anionic polymer or its aqueous solution, the cooled mixed liquid (c), and, if necessary, other components (04) is not particularly limited, and may be the same as or different from the method for mixing gelatin, an oil component, and, if necessary, other components (01) in the presence of water in the above-mentioned emulsification process.

In the additional mixing step, when adding the remaining components to any of the additive objects, namely the second anionic polymer or its aqueous solution, the cooled mixed liquid (c), and other components (04) as necessary, the remaining components may be added while stirring the additive object, or the remaining components may be added without stirring the additive object, so that all the components are mixed and then the mixture is stirred.

In the additional mixing step, after all the components (the second anionic polymer or its aqueous solution, the cooled mixture (c), and other components (04) as necessary) are mixed, the mixture is stirred for a time period of preferably 1 to 30 minutes, more preferably 1 to 10 minutes.

In the additional mixing step, for example, it is preferable to prepare mixed liquid (d) by adding or dropping a second anionic polymer aqueous solution to mixed liquid (c) after cooling.

<Polyphenols mixing process>
In the polyphenols mixing step, the mixed liquid (d) is mixed with polyphenols to prepare a mixed liquid (e).
By carrying out this step, the desired microcapsules having a small average particle size and high encapsulation-retention performance can be obtained as an aqueous dispersion.
In the mixed solution (e), the wall material components are bound together by the action of the phenolic hydroxyl groups in the polyphenols, forming microcapsules with strong walls. The action of the phenolic hydroxyl groups in this case is as described above.
That is, the mixed liquid (e) contains the desired microcapsules.

The polyphenols used in the polyphenol mixing process have been described above, and detailed description will be omitted here.

The polyphenols used in the polyphenol mixing step may be one type only, or two or more types. If two or more types are used, the combination and ratio of the polyphenols may be selected arbitrarily.

In the polyphenol mixing step, the polyphenols may be mixed alone, but it is preferable to mix them as an aqueous solution. By using an aqueous solution of polyphenols, microcapsules with a more stable structure can be obtained.

The concentration of polyphenols in the aqueous polyphenol solution used in the polyphenol mixing step can be adjusted appropriately depending on the type of polyphenols, but is preferably 15 to 45% by mass, and more preferably 20 to 30% by mass.

When the aqueous polyphenol solution is mixed with the mixed liquid (d), it is preferable to add the aqueous polyphenol solution to the mixed liquid (d), and the aqueous polyphenol solution may be added to the mixed liquid (d) all at once or dropwise.
When the polyphenols are not added as an aqueous solution, it is preferable to add the polyphenols to the mixed liquid (d). The polyphenols may be added to the mixed liquid (d) all at once or in portions.

In the polyphenols mixing step, the amount of polyphenols used may be 0.2 to 0.7 times, 0.3 to 0.6 times, or 0.4 to 0.5 times by mass relative to the total amount of gelatin, the first anionic polymer, and the second anionic polymer in the mixed liquid (d). When the amount of polyphenols used is equal to or greater than the lower limit, the wall material of the microcapsules becomes stronger. When the amount of polyphenols used is equal to or less than the upper limit, excessive use of polyphenols is suppressed.

In the polyphenols mixing step, other components that do not fall into any of the following categories (gelatin, the first anionic polymer, the second anionic polymer, the oil component, the acid, and the polyphenols) (sometimes referred to as "other components (05)" in this specification) may be mixed within a range that does not impair the effects of the present invention.

The other component (05) is not particularly limited and can be arbitrarily selected depending on the purpose.
The other component (05) used in the polyphenol mixing step may be only one type, or may be two or more types. When two or more types are used, the combination and ratio thereof can be selected arbitrarily.

Examples of the other component (05) include polyvalent metal salts and water.
The polyvalent metal salt used in the polyphenol mixing step has been described above, and detailed description thereof will be omitted here. The effects obtained when using the polyvalent metal salt are as described above.

In the polyphenol mixing step, the polyvalent metal salt may be mixed alone, but it is preferable to mix it as an aqueous solution. By using an aqueous solution of the polyvalent metal salt, microcapsules with a more stable structure can be obtained.

The concentration of the polyvalent metal salt in the aqueous polyvalent metal salt solution used in the polyphenol mixing step can be adjusted appropriately depending on the type of polyvalent metal salt, but is preferably 1 to 20% by mass, and more preferably 5 to 15% by mass.

In the polyphenol mixing step, the amount of the other component (05) used is not particularly limited and can be adjusted appropriately depending on the type of the other component (05).

When the other component (05) is the polyvalent metal salt having a metal ion with a valence of 2 as a constituent component, the amount of the other component (05) used in the polyphenol mixing step is preferably an amount such that the amount of metal (metal ion) in the polyvalent metal salt is 20 to 110 mmol, more preferably 23 to 106 mmol, per 100 g of the total amount of gelatin, the first anionic polymer, and the second anionic polymer in the mixed liquid (d). When the amount of the other component (05) used is equal to or greater than the lower limit, microcapsules with higher sustained release properties are obtained. When the amount of the other component (05) used is equal to or less than the upper limit, microcapsules with a smaller average particle size are obtained.
For example, in the case where the polyvalent metal salt is one or more selected from the group consisting of calcium salts, magnesium salts, barium salts, and zinc salts, the "amount of other component (05) used" means the "total amount of calcium salts, magnesium salts, barium salts, and zinc salts used."

When the other component (05) is the polyvalent metal salt having a metal ion with a valence of 3 or more as a constituent, the amount of the other component (05) used in the polyphenol mixing step is preferably an amount such that the amount of metal (metal ion) in the polyvalent metal salt is 5 to 30 mmol, more preferably 5.5 to 29 mmol, per 100 g of the total amount of gelatin, the first anionic polymer, and the second anionic polymer in the mixed liquid (d). When the amount of the other component (05) used is equal to or greater than the lower limit, microcapsules with higher sustained release properties are obtained. When the amount of the other component (05) used is equal to or less than the upper limit, microcapsules with a smaller average particle size are obtained.
For example, in the case where the polyvalent metal salt is one or more kinds selected from the group consisting of aluminum salts and zirconium salts, the "amount of other component (05) used" means the "total amount of aluminum salt and zirconium salt used."

When the other component (05) is a component other than the polyvalent metal salt, typically, in the polyphenols mixing step, the ratio of the amount of the other component (05) used to the total amount of the mixed liquid (d) and the polyphenols used ([amount of the other component (05) used]/([amount of the mixed liquid (d) used]+[amount of the polyphenols 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. When the ratio is within such a range, microcapsules with a smaller average particle size and higher encapsulation retention performance can be obtained.

In the polyphenol mixing step, when the mixed liquid (d), the polyphenols or the aqueous polyphenol solution, and, if necessary, other components (05) are mixed, the mixing is preferably carried out under a temperature condition of 0 to 10° C., and more preferably under a temperature condition of 2 to 9° C. By mixing at such a temperature, microcapsules having a more stable structure can be obtained.
The temperature range during mixing in the polyphenols mixing step may or may not be the same as the temperature range of the mixed liquid (c) in the cooling step or the temperature range of the mixed liquid (d) in the additional mixing step.

The method for mixing the mixed liquid (d), the polyphenols or the aqueous solution of polyphenols, and, if necessary, the other component (05) is not particularly limited, and may be the same as or different from the method for mixing the gelatin, the oil component, and, if necessary, the other component (01) in the presence of water in the above-mentioned emulsification process.

In the polyphenols mixing step, when adding the remaining components to any of the additive objects, namely the mixed liquid (d), the polyphenols or the aqueous solution of polyphenols, and, if necessary, other components (05), the additive objects may be stirred while the remaining components are being added, or the additive objects may be stirred without stirring, and the remaining components may be added after all the components have been mixed, and then the mixture may be stirred.

In the polyphenol mixing step, after all the components (mixture (d), polyphenols or aqueous polyphenol solution, and other components (05) as necessary) are mixed, the resulting mixture is stirred for a time period of preferably 1 to 30 minutes, more preferably 1 to 10 minutes.

In the polyphenols mixing step, for example, it is preferable to prepare mixed liquid (e) by adding an aqueous solution of polyphenols to mixed liquid (d), and it is more preferable to prepare mixed liquid (e) by adding an aqueous solution of polyphenols to mixed liquid (d) while keeping the temperature of mixed liquid (d) constant.

When the polyvalent metal salt is used, in the polyphenols mixing step, the polyphenols and the polyvalent metal salt may be mixed in this order, or the polyvalent metal salt and the polyphenols may be mixed in this order, or the polyphenols and the polyvalent metal salt may be mixed simultaneously. In terms of obtaining microcapsules with a smaller average particle size, it is preferable to mix the polyphenols and the polyvalent metal salt in this order in the polyphenols mixing step.

When the polyvalent metal salt is used, in the polyphenols mixing step, it is preferable to prepare the mixed liquid (e) by adding the polyvalent metal salt aqueous solution to the target object (e.g., the mixed liquid (d) before or after mixing with the polyphenols), and it is more preferable to prepare the mixed liquid (e) by adding the polyvalent metal salt aqueous solution to the target object while keeping the temperature of the target object constant.

<Base mixing step>
In the base mixing step, the mixed liquid (e) is mixed with a base to prepare an aqueous dispersion of microcapsules having an adjusted pH.
The microcapsules obtained in the base mixing step have a more stable structure in the aqueous dispersion.

The pH of the aqueous dispersion of microcapsules obtained in the base mixing step is not particularly limited as long as the microcapsules can be stably present, but is preferably 4 to 7, and may be, for example, 4 to 6.

The base used in the base mixing step is not particularly limited and may be, for example, either an inorganic base or an organic base.
Examples of the inorganic base include alkali metal hydroxides such as sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH); alkali metal carbonates such as sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), and lithium carbonate (Li ₂ CO ₃ ); and alkali metal hydrogen carbonates such as sodium hydrogen carbonate (NaHCO ₃ ), and potassium hydrogen carbonate (KHCO ₃ ).
The organic base includes, for example, alkylamines such as triethylamine ((CH ₃ CH ₂ ) ₃ N).

The base used in the base mixing step may be one type only, or two or more types. When two or more types are used, the combination and ratio of the bases may be selected arbitrarily.

In the base mixing step, the base may be mixed alone or as an aqueous solution. By using an aqueous base solution, it is easier to prepare an aqueous dispersion of microcapsules with an adjusted pH.

The concentration of the base in the aqueous base solution used in the base mixing step can be adjusted appropriately depending on the type of base, but is preferably 10 to 40% by mass, and more preferably 15 to 25% by mass.

When the aqueous base solution and the mixed liquid (e) are mixed, it is preferable to add the aqueous base solution to the mixed liquid (e), and the aqueous base solution may be added to the mixed liquid (e) all at once or dropwise.
When the base is not added as an aqueous solution, it is preferable to add the base to the mixed liquid (e). The base may be added to the mixed liquid (e) all at once, or may be added dropwise or in portions.

In the base mixing step, when the mixed liquid (e) is mixed with a base or an aqueous base solution, the mixing is preferably carried out at a temperature of 0 to 10°C, and more preferably at a temperature of 2 to 9°C.

The method for mixing the mixed liquid (e) with the base or the aqueous base solution is not particularly limited, and may be the same as or different from the method for mixing the gelatin, the oil component, and, if necessary, other components (01) in the presence of water in the above-mentioned emulsification process.

In the base mixing step, when the remaining components are added to either the mixed liquid (e) and the base or the aqueous base solution, the remaining components may be added while stirring the components to be added, or the remaining components may be added without stirring the components to be added, so that all the components are mixed and then the mixture is stirred.

In the base mixing step, after all the components (mixture (e) and base or aqueous base solution) are mixed, the mixture obtained is stirred for, for example, preferably 1 to 8 hours, more preferably 2 to 6 hours. When the time is equal to or greater than the lower limit, the effect of using the base is more pronounced. When the time is equal to or less than the upper limit, the time required for the base mixing step is prevented from becoming excessively long.

Thus, when stirring the mixture obtained after mixing all the components, the mixture is preferably stirred at a temperature of 15 to 40°C, more preferably at a temperature of 18 to 30°C, or may be stirred at room temperature (e.g., room temperature).

In the base mixing step, for example, it is preferable to prepare an aqueous dispersion of microcapsules by adding or dropping an aqueous base solution to the mixed liquid (e), and it is more preferable to prepare an aqueous dispersion of microcapsules by dropping an aqueous base solution to the mixed liquid (e).
The addition or dropwise addition of the aqueous base solution to the mixed liquid (e) is preferably carried out at a temperature of 0 to 10°C, more preferably at a temperature of 2 to 9°C.

<Other steps>
The method for producing microcapsules of this embodiment may include other processes that do not fall under any of the above-mentioned emulsification process, emulsion mixing process, acidification process, cooling process, additional mixing process, polyphenols mixing process, and base mixing process, as long as the effects of the present invention are not impaired.
The type of other steps, the number of other steps, and the timing of performing the other steps can be arbitrarily selected depending on the purpose, and are not particularly limited.

The microcapsules obtained by the above-mentioned production method may be used as an aqueous dispersion as it is, or the aqueous dispersion obtained by carrying out known post-treatment, purification, etc. may be used as it is, or the aqueous dispersion may be used as a single microcapsule by removing the dispersion medium after carrying out known post-treatment, purification, etc. as necessary.
The microcapsules have a high ability to encapsulate and retain the oily component, which is the core substance, in any state (particularly, even in the form of a single substance after removal of the dispersion medium).

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

Some of the polymers used in the following examples and comparative examples are shown in Table 1.

Polymer (Z)-5 was prepared in the following manner.
That is, ethylene maleic anhydride copolymer (manufactured by Aldrich) (5 parts by mass) and sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) (0.75 parts by mass) were added to distilled water (94.25 parts by mass), and the mixture was heated and stirred at 80° C. for 2 hours. This caused a hydrolysis reaction, and the ring structure (acid anhydride moiety) in the structural unit derived from maleic anhydride was opened, thereby obtaining polymer (Z)-5.

[Example 1]
<<Production of Microcapsules>>
An aqueous solution (130 g) of gelatin ("Type A" manufactured by MP Biomedicals) with a concentration of 5% by mass was heated to 50° C., and lavender essential oil (manufactured by Ash) (50 g) at room temperature (under conditions of 23° C.) was added to this aqueous solution. An emulsion was produced by stirring at a stirring speed of 10,000 rpm at room temperature for 3 minutes using an emulsifier (manufactured by Primix) (emulsification process).

An aqueous solution (130 g) of polymer (Z)-1 (gum arabic, corresponding to the first anionic polymer) having a concentration of 6% 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, an aqueous solution (10 g) of polymer (Z)-2 (sodium carboxymethylcellulose, corresponding to the second anionic polymer) having a concentration of 10% by mass was heated to 50° C., and the entire amount of this heated aqueous solution was added to the above obtained solution, and the mixture was stirred for 2 minutes while maintaining the temperature at 50° C., thereby preparing a mixed solution (a) (emulsion mixing step).

Next, while stirring the mixed solution (a) at 50°C, an aqueous solution of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with a concentration of 50% by mass at room temperature was added dropwise to the mixed solution (a) and stirred for 2 minutes to adjust the pH of the mixed solution (a) to 3.8, thereby producing an acidic mixed solution (b).

Next, while stirring the mixed solution (b) at 50°C, distilled water (200 g) at a temperature of 50°C was added to it, and the mixture was stirred for 2 minutes while maintaining the temperature at 50°C to produce an acidic mixed solution (c) (this is the acidification process).

Then, the resulting mixture (c) was cooled with stirring at a cooling rate of 0.5°C/min until its temperature reached 5°C (cooling process).

Next, an aqueous solution (10 g) of polymer (Z)-2 (corresponding to the second anionic polymer) with a concentration of 10% by mass was added to the mixed solution (c) being stirred at a temperature of 5°C, and the mixture was stirred for 2 minutes while maintaining the temperature at 5°C to prepare mixed solution (d) (additional mixing step).

Next, an aqueous solution (30 g) of tannic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) with a concentration of 25% by mass was added to the mixed solution (d) and stirred for 2 minutes at a temperature of 5°C to prepare the mixed solution (e) (polyphenols mixing step).

Next, while stirring the mixed liquid (e) at 5°C, an aqueous solution of sodium hydroxide (manufactured by Kanto Chemical Co., Ltd.) having a concentration of 20% by mass was added dropwise to the mixed liquid (e) to adjust the pH of the mixed liquid (e) to 6.0. Next, the mixed liquid (e) after the pH adjustment was stirred at room temperature for 4 hours to prepare an aqueous dispersion of microcapsules (base mixing process).
As a result of the above, microcapsules having wall components containing gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), further containing tannic acid, and encapsulating lavender essential oil as a core material were obtained as an aqueous dispersion.

The raw materials used in this example are shown in Table 2. Among the raw materials, components that do not fall into either the category of "polymer to be mixed with emulsion" or "polymer to be mixed with mixed liquid after acid addition and cooling" (e.g., crosslinking agent) are listed as "additives" in Table 2. The same applies to the following Table 3.

<<Evaluation of Microcapsules>>
<Evaluation of the degree of microcapsule formation>
The appearance of the product in the aqueous dispersion obtained above was observed using a scanning electron microscope (SEM, JEOL Ltd. "JSM-6700F") to confirm the degree of wall formation, and the degree of microcapsule formation was evaluated according to the following criteria. The results are shown in Table 4.
[Evaluation Criteria]
A: The wall material is formed normally, and the microcapsules are produced normally.
B: A wall material was formed, but the microcapsules were not neatly formed.
C: The wall material was not formed normally and no microcapsules were produced.

In Table 4, a "-" in the "Evaluation Result" column means that the item has not been evaluated. The same applies to the following Table 5.

<Measurement of average particle size of microcapsules>
The average particle size of the microcapsules was measured using a particle size distribution analyzer (Sysmex Corporation, "CDA-1000X") and the aqueous dispersion obtained above. The results are shown in Table 4.

<Evaluation of the encapsulation retention performance of microcapsules>
The aqueous dispersion of microcapsules obtained above was coated on fine paper using a wire bar (No. 30), and then dried in an oven at 105° C. for 10 minutes.
Next, a cylindrical weight having a mass of 4 kg was placed on the obtained dried material with its curved surface (side surface) in contact with the dried material, and the weight was rolled back and forth five times on the dried material.
Next, the dried product was checked to see if it gave off the scent of lavender essential oil, and the encapsulation-retaining performance of the microcapsules was evaluated according to the following criteria. The results are shown in Table 4.
[Evaluation Criteria]
A: The dried product did not give off the scent of lavender essential oil, and the encapsulation and retention performance of the microcapsules was high.
B: The dried product had a scent of lavender essential oil, and the encapsulation-retaining performance of the microcapsules was not observed or was low.

<Safety classification of microcapsules>
The safety of the obtained microcapsules to living organisms was classified according to the following criteria based on the manufacturing raw materials of the wall material. The results are shown in Table 4.
[Classification criteria]
A: The raw materials used to manufacture the wall material do not contain any substances that are highly toxic to living organisms, making the microcapsules highly safe for living organisms.
B: The raw materials used for manufacturing the wall material are highly toxic to living organisms, and the safety of the microcapsules to living organisms is low.

<Evaluation of sustained release properties of microcapsules>
The aqueous dispersion of the microcapsules (50 μL) obtained above was dropped onto a filter paper (No. 3 manufactured by ADVANTEC), and the filter paper with the drops on it was placed inside an oven and heat-treated at 40° C. for 2 hours.
The filter paper was then removed from the oven, and the residue on the filter paper was extracted with acetonitrile (30 mL). The resulting extract was analyzed by high performance liquid chromatography (HPLC) to quantify the amount of the core material in the extract. From the quantitative value, the remaining rate (volume %) of the core material in the microcapsules was calculated using the formula (i) described above. The results are shown in Table 4 (column "Sustained release (remaining rate (volume %))").

<<Production and Evaluation of Microcapsules>>
[Example 2]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that in both the emulsion mixing step and the additional mixing step, the same amount (parts by mass) of polymer (Z)-3 (sodium alginate) was used instead of polymer (Z)-2. In this example, microcapsules were obtained as an aqueous dispersion, in which the wall material components were composed of gelatin, gum arabic (polymer (Z)-1), and sodium alginate (polymer (Z)-3), and further contained tannic acid and contained lavender essential oil as a core material. The results are shown in Table 4.

[Example 3]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that in both the emulsion mixing step and the additional mixing step, the same amount (parts by mass) of polymer (Z)-4 (iota carrageenan) was used instead of polymer (Z)-2. In this example, microcapsules were obtained as an aqueous dispersion, in which the wall material components were composed of gelatin, gum arabic (polymer (Z)-1), and iota carrageenan (polymer (Z)-4), and further contained tannic acid and contained lavender essential oil as a core material. The results are shown in Table 4.

[Example 4]
In both the emulsion mixing step and the additional mixing step, the same amount (parts by mass) of polymer (Z)-5 (a ring-opened product of ethylene-maleic anhydride copolymer with sodium hydroxide) was used instead of polymer (Z)-2. Microcapsules were produced and evaluated in the same manner as in Example 1. In this example, microcapsules were obtained as an aqueous dispersion, in which the wall material components were composed of gelatin, gum arabic (polymer (Z)-1), and a ring-opened product of ethylene-maleic anhydride copolymer with sodium hydroxide (polymer (Z)-5), and further contained tannic acid and contained lavender essential oil as a core material. The results are shown in Table 4.

[Example 5]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that the same amount (parts by mass) of polymer (Z)-3 was used instead of polymer (Z)-1. In this example, microcapsules were obtained as an aqueous dispersion, in which the wall material components contained gelatin, sodium alginate (polymer (Z)-3), and sodium carboxymethylcellulose (polymer (Z)-2), and further contained tannic acid and contained lavender essential oil as a core material. The results are shown in Table 4.

[Example 6]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that the same amount (parts by mass) of polymer (Z)-2 was used instead of polymer (Z)-1, and the same amount (parts by mass) of polymer (Z)-3 was used instead of polymer (Z)-2 in both the emulsion mixing step and the additional mixing step. In this example, microcapsules were obtained as an aqueous dispersion, in which the wall material components were composed of gelatin, sodium carboxymethylcellulose (polymer (Z)-2), and sodium alginate (polymer (Z)-3), and further contained tannic acid and contained lavender essential oil as a core material. The results are shown in Table 4.

[Comparative Example 1]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that polymer (Z)-2 was not used in either the emulsion mixing step or the additional mixing step. The results are shown in Table 5.
The raw materials used in this comparative example are shown in Table 3.
In Table 3, the notation "-" in the "Raw Material" column means that the raw material was not used.

[Comparative Example 2]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that in both the emulsion mixing step and the additional mixing step, the same amount (parts by mass) of polymer (Z)-7 (polyvinyl alcohol) was used instead of polymer (Z)-2. The results are shown in Table 5.

[Comparative Example 3]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that in both the emulsion mixing step and the additional mixing step, the same amount (parts by mass) of polymer (Z)-8 (chitosan) was used instead of polymer (Z)-2. The results are shown in Table 5.

[Comparative Example 4]
Except for not using the polymer (Z)-2 in the additional mixing step, microcapsules were produced and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[Comparative Example 5]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that polymer (Z)-2 was not used in the emulsion mixing step. The results are shown in Table 5.

[Comparative Example 6]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that the same amount (parts by mass) of polymer (Z)-2 was used instead of polymer (Z)-1. The results are shown in Table 5.

[Comparative Example 7]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that the same amount (parts by mass) of aluminum sulfate (Al ₂ (SO ₄ ) ₃ , manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of tannic acid. The results are shown in Table 5.

[Comparative Example 8]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that the same amount (parts by mass) of calcium chloride (CaCl ₂ , manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of tannic acid. The results are shown in Table 5.

[Comparative Example 9]
Except for using the same amount (parts by mass) of transglutaminase (manufactured by Ajinomoto Co., Inc.) instead of tannic acid, microcapsules were produced and evaluated in the same manner as in Example 1. The results are shown in Table 5.

[Reference Example 1]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that in the emulsion mixing step, the same amount (parts by mass) of polymer (Z)-6 (polyoxyethylene polyoxypropylene block polymer) was used instead of polymer (Z)-2, and in the additional mixing step, polymer (Z)-2 was not used. The results are shown in Table 5.

[Reference Example 2]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that in the emulsion mixing step, the same amount (parts by mass) of polymer (Z)-6 was used instead of polymer (Z)-2, in the additional mixing step, polymer (Z)-2 was not used, and the same amount (parts by mass) of aluminum sulfate (Al ₂ (SO ₄ ) ₃ , Fujifilm Wako Pure Chemical Industries, Ltd.) was used instead of tannic acid. The results are shown in Table 5.

<<Production and Evaluation of Microcapsules>>
[Example 7]
Microcapsules were produced and evaluated in the same manner as in Example 1, except that in the acidification step, the addition of distilled water (200 g) at a temperature of 50° C. was omitted, and in the additional mixing step, the amount of the aqueous solution of polymer (Z)-2 used was 20 g instead of 10 g. In this example, microcapsules were obtained as an aqueous dispersion, in which the wall material components were composed of gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), and further contained tannic acid and contained lavender essential oil as a core material. The results are shown in Table 4.

[Example 8]
In the acidification step, the addition of distilled water (200 g) at a temperature of 50 ° C. was omitted, in the additional mixing step, the amount of the aqueous solution of polymer (Z)-2 used was 20 g instead of 10 g, and in the polyphenols mixing step, after the aqueous solution of tannic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (30 g) was added, an aqueous solution of potassium aluminum sulfate (AlK (SO ₄ ) ₂ ), Fuji Film Wako Pure Chemical Industries, Ltd.) having a concentration of 10% by mass (10 g) was added, and then the mixture was stirred for 2 minutes under a temperature condition of 5 ° C. Microcapsules were produced and evaluated in the same manner as in Example 1. In this example, a microcapsule containing gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), which is a wall material component, further contains tannic acid and potassium aluminum sulfate (polyvalent metal salt), and contains lavender essential oil as a core material, was obtained as an aqueous dispersion. In the microcapsules, the aluminum content in potassium aluminum sulfate was 6 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose. The results are shown in Table 4.

In Table 2, among the raw materials listed in the "Additives" column, for potassium aluminum sulfate (AlK( _SO4 ) ₂ ), i.e., polyvalent metal salt, the aluminum content (mmol) described above, i.e., the metal content (mmol) in the polyvalent metal salt per 100 g of the total content of gelatin, first anionic polymer, and second anionic polymer in the microcapsules, is also listed in parentheses. This is the same for the other subsequent examples in which polyvalent metal salts are used.

[Example 9]
Microcapsules were produced and evaluated in the same manner as in Example 8, except that the amount (parts by mass) of potassium aluminum sulfate used was doubled, so that the aluminum content in potassium aluminum sulfate was 12 mmol instead of 6 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 10]
Microcapsules were produced and evaluated in the same manner as in Example 8, except that the amount (parts by mass) of potassium aluminum sulfate used was increased by four times, so that the aluminum content in potassium aluminum sulfate was 24 mmol instead of 6 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 11]
Microcapsules were produced and evaluated in the same manner as in Example 8, except that in the polyphenol mixing step, an aqueous solution of aluminum sulfate (Al ₂ (SO ₄ ) ₃ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) with a concentration three times (by mass) was used instead of the aqueous solution of potassium aluminum sulfate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.). In this example, microcapsules were obtained as an aqueous dispersion, in which the wall material components were composed of gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), and further contained tannic acid and aluminum sulfate, and contained lavender essential oil as a core material. In the microcapsules, the content of aluminum in aluminum sulfate was 18 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose. The results are shown in Table 4.

[Example 12]
Microcapsules were produced and evaluated in the same manner as in Example 11, except that the amount (parts by mass) of aluminum sulfate used was 1.56 times, so that the aluminum content in aluminum sulfate was 28 mmol instead of 18 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 13]
Microcapsules were produced and evaluated in the same manner as in Example 8, except that in the polyphenol mixing step, instead of the aqueous solution of potassium aluminum sulfate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), an aqueous solution of calcium chloride (CaCl ₂ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) with a concentration of 4.3 times (mass ratio) was used. In this example, a microcapsule was obtained as an aqueous dispersion, in which the wall material component was composed of gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), further containing tannic acid and calcium chloride, and encapsulating lavender essential oil as a core material. In the microcapsules, the calcium content in calcium chloride was 26 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose. The results are shown in Table 4.

[Example 14]
Microcapsules were produced and evaluated in the same manner as in Example 13, except that the amount of calcium chloride used (parts by mass) was doubled, so that the calcium content in calcium chloride was 52 mmol instead of 26 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 15]
Microcapsules were produced and evaluated in the same manner as in Example 13, except that the amount (parts by mass) of calcium chloride used was tripled, so that the calcium content in calcium chloride was 78 mmol instead of 26 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 16]
Microcapsules were produced and evaluated in the same manner as in Example 13, except that the amount (parts by mass) of calcium chloride used was increased four-fold, so that the calcium content in calcium chloride was 104 mmol instead of 26 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 17]
Microcapsules were produced and evaluated in the same manner as in Example 8, except that in the polyphenol mixing step, instead of the aqueous solution of potassium aluminum sulfate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), an aqueous solution of magnesium sulfate (MgSO ₄ , manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) with a concentration of 8 times (mass ratio) was used. In this example, a microcapsule was obtained as an aqueous dispersion, in which the wall material component was composed of gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), further containing tannic acid and magnesium sulfate, and encapsulating lavender essential oil as a core material. In the microcapsules, the magnesium content in magnesium sulfate was 24 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose. The results are shown in Table 4.

[Example 18]
Microcapsules were produced and evaluated in the same manner as in Example 17, except that the amount (parts by mass) of magnesium sulfate used was doubled, so that the magnesium content in magnesium sulfate was 48 mmol instead of 24 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 19]
In the polyphenol mixing step, instead of the aqueous solution of potassium aluminum sulfate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), an aqueous solution containing calcium chloride (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) and magnesium sulfate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) at a concentration of 4.3 times (mass ratio) was used. The microcapsules were produced and evaluated in the same manner as in Example 8. In this example, the wall material components were composed of gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), and further contained tannic acid, calcium chloride, and magnesium sulfate, and contained lavender essential oil as a core material. In the microcapsules, the calcium content in calcium chloride and the magnesium content in magnesium sulfate were both 26 mmol (total 52 mmol) per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose. The results are shown in Table 4.

[Example 20]
In the acidification step, the addition of distilled water (200 g) at a temperature of 50 ° C. was omitted, in the additional mixing step, the amount of the aqueous solution of polymer (Z)-2 used was 20 g instead of 10 g, and in the polyphenols mixing step, after adding the aqueous solution of tannic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (30 g), an aqueous solution of potassium aluminum sulfate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) having a concentration of 10% by mass (10 g) was added, and then the mixture was stirred for 2 minutes under a temperature condition of 5 ° C. Microcapsules were produced and evaluated in the same manner as in Example 2. In this example, a microcapsule containing gelatin, gum arabic (polymer (Z)-1), and sodium alginate (polymer (Z)-2), which is a wall material component, further contains tannic acid and potassium aluminum sulfate, and contains lavender essential oil as a core material, was obtained as an aqueous dispersion. In the microcapsules, the aluminum content in potassium aluminum sulfate was 17 mmol per 100 g of the total content of gelatin, gum arabic, and sodium alginate. The results are shown in Table 4.

[Example 21]
Microcapsules were produced and evaluated in the same manner as in Example 8, except that the amount (parts by mass) of potassium aluminum sulfate used was 0.5 times, so that the aluminum content in potassium aluminum sulfate was 3 mmol instead of 6 mmol per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules. The results are shown in Table 4.

[Example 22]
Microcapsules were produced and evaluated in the same manner as in Example 13, except that the amount (parts by mass) of calcium chloride used was 0.5 times, so that the calcium content in calcium chloride per 100 g of the total content of gelatin, gum arabic, and sodium carboxymethylcellulose in the microcapsules was 13 mmol instead of 26 mmol. The results are shown in Table 4.

[Example 23]
In the acidification step, the addition of distilled water (200 g) at a temperature of 50° C. was omitted, the amount of the aqueous solution of polymer (Z)-2 used in the additional mixing step was 20 g instead of 10 g, and in the polyphenols mixing step, the aqueous solution of tannic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) (30 g) was added, and then transglutaminase (manufactured by Ajinomoto Co., Inc.) (5 g) was added and stirred for 2 minutes under a temperature condition of 5° C. Microcapsules were produced and evaluated in the same manner as in Example 1. In this example, a microcapsule containing gelatin, gum arabic (polymer (Z)-1), and sodium carboxymethylcellulose (polymer (Z)-2), which is a wall material component, further contains tannic acid and transglutaminase, and contains lavender essential oil as a core material, was obtained as an aqueous dispersion. The results are shown in Table 4.

As is clear from the above results, in Examples 1 to 23, the wall material was formed normally, the microcapsules were generated normally, and the average particle size was 15 μm or less (4 to 15 μm), which was sufficiently small. In Examples 1 to 23, the encapsulation and retention performance of the microcapsules was high. In Examples 1 to 23, the raw materials used to manufacture the wall material did not contain any substances that are highly toxic to living organisms, and the microcapsules were highly safe for living organisms.

The microcapsules of Examples 1 to 7 were composed of gelatin, a first anionic polymer, a second anionic polymer, and polyphenols.
The microcapsules of Examples 8 to 22 were composed of gelatin, a first anionic polymer, a second anionic polymer, a polyphenol, and a polyvalent metal salt.
The microcapsules of Example 23 contained gelatin, a first anionic polymer, a second anionic polymer, polyphenols, and transglutaminase.
In Examples 1 to 23, when producing the microcapsules, the emulsion was mixed with a first anionic polymer and a second anionic polymer, and the mixed liquid after the addition of acid and cooling was further mixed with the second anionic polymer.

In Examples 8 to 20, when polyphenols and polyvalent metal salts (potassium aluminum sulfate, aluminum sulfate, calcium chloride, or magnesium sulfate) were used in combination, the residual rate of the core material in the microcapsules was 30.9% by volume or more (30.9 to 54.3% by volume), and the sustained release properties of the microcapsules were particularly high.

In contrast, in Comparative Examples 1, 4 to 5, and Reference Example 1, the wall material was formed normally and microcapsules were produced, but the average particle size was large, at 21 μm or more. Furthermore, in Reference Example 1, the encapsulation and retention performance of the microcapsules was low.

In Comparative Example 1, no anionic polymer was used.
In Comparative Example 4, the first anionic polymer and the second anionic polymer were used in combination, but the second anionic polymer was not mixed with the mixed liquid after the addition of acid and cooling.
In Comparative Example 5, the first anionic polymer and the second anionic polymer were used in combination, but the second anionic polymer was not mixed with the emulsion.
In Reference Example 1, a nonionic surfactant was used in combination as a polymer, but only one type of anionic polymer was used.

In Reference Example 2, the wall material was formed normally, the microcapsules were generated normally, and the average particle size was 6 μm, which was sufficiently small, but the encapsulation and retention performance of the microcapsules was low.
In Reference Example 2, a nonionic surfactant was used in combination as a polymer, but only one type of anionic polymer was used. Furthermore, a polyvalent metal salt (aluminum sulfate) was used in combination, but no polyphenols were used.

In Comparative Example 2, the average particle diameter of the microcapsules was several hundred μm, which was significantly large, and the microcapsules were aggregated. In Comparative Example 2, the microcapsules were not neatly formed, and the encapsulation and retention performance of the microcapsules was not evaluated.
In Comparative Example 2, a nonionic polymer was used in combination, but only one anionic polymer was used.

In Comparative Example 3, the average particle size of the microcapsules was large at 90 μm. In Comparative Example 3, the microcapsules were not neatly formed, and the encapsulation and retention performance of the microcapsules was not evaluated.
In Comparative Example 3, a cationic polymer was used in combination, but only one anionic polymer was used.

In Comparative Examples 6 and 7, the average particle size of the microcapsules reached several hundred μm, which was significantly large, and the microcapsules were aggregated.
In Comparative Example 6, only one anionic polymer was used.
In Comparative Example 7, a polyvalent metal salt (aluminum sulfate) was used in combination, but no polyphenols were used.

In Comparative Examples 8 and 9, the wall material was not formed normally and no microcapsules were produced. Therefore, in Comparative Examples 8 and 9, the encapsulation and retention performance of the microcapsules could not be evaluated.
In Comparative Example 8, a polyvalent metal salt (calcium chloride) was used in combination, but no polyphenols were used.
In Comparative Example 9, transglutaminase was used in combination, but no polyphenols were used.

The present invention can be used as microcapsules for skin contact (e.g., topical agents, cosmetics, etc.).

Claims (10)

A microcapsule comprising:
The microcapsules are configured to include gelatin, a first anionic polymer, a second anionic polymer different from the first anionic polymer, and polyphenols;
The microcapsules encapsulate an oily component with a wall material,
the wall material is composed of the gelatin, a first anionic polymer, and a second anionic polymer;
The polyphenols are one or more selected from the group consisting of tannic acid, catechin, chlorogenic acid, gallic acid, quinic acid, and caffeic acid;
The microcapsules have an average particle size of 20 μm or less. 2. The microcapsule according to claim 1, wherein the first anionic polymer and the second anionic polymer are one or more selected from the group consisting of gum arabic, alginic acid, sodium alginate, carboxymethylcellulose, sodium carboxymethylcellulose, carrageenan, a ring-opened product of ethylene maleic anhydride copolymer, xanthan gum, and pectin, and the first anionic polymer and the second anionic polymer are different in type from each other. The microcapsule according to claim 1 or 2, wherein the oil component is a fragrance. The microcapsule according to any one of claims 1 to 3, further comprising a polyvalent metal salt. The microcapsule according to claim 4, wherein the polyvalent metal salt is one or more selected from the group consisting of aluminum salts and zirconium salts. The microcapsule according to claim 5, wherein the total content of aluminum in the aluminum salt and zirconium in the zirconium salt is 5 to 30 mmol per 100 g of the total content of the gelatin, the first anionic polymer, and the second anionic polymer. The microcapsule according to claim 4, wherein the polyvalent metal salt is one or more selected from the group consisting of calcium salts, magnesium salts, barium salts and zinc salts. The microcapsule according to claim 7, wherein the total content of calcium in the calcium salt, magnesium in the magnesium salt, barium in the barium salt, and zinc in the zinc salt is 20 to 110 mmol per 100 g of the total content of the gelatin, the first anionic polymer, and the second anionic polymer. A step of preparing an emulsion by mixing gelatin and an oil component in the presence of water;
preparing a mixed solution (a) by mixing a first anionic polymer, a second anionic polymer different from the first anionic polymer, and the emulsion in the presence of water;
preparing an acidic mixed solution (c) by mixing the mixed solution (a) with an acid;
cooling the mixture (c) until its temperature is 10° C. or less;
mixing the cooled mixture (c) with the second anionic polymer to prepare a mixture (d);
preparing a mixed liquid (e) by mixing the mixed liquid (d) with polyphenols;
and mixing the mixed liquid (e) with a base to prepare an aqueous dispersion of microcapsules having an adjusted pH. The method for producing microcapsules according to claim 9, further comprising mixing a polyvalent metal salt in the step of preparing the mixed liquid (e).