Microcapsule

Abstract

To provide a microcapsule that has a wall material composed of polyurea and contains a core substance having a formyl group.SOLUTION: A microcapsule has a wall material composed of polyurea. The polyurea is a polycondensate of a polyisocyanate compound and a polyamine compound. An aqueous solution of the polyamine compound with a concentration of 1 mass% has a pH of 9-13. The microcapsule contains a component having a formyl group.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to microcapsules.

Background Art

[0002] Microcapsules are composed of a wall material encapsulating a target component as a core substance. The core substance encapsulated in the microcapsules can have its release characteristics adjusted, for example, to be gradually released outside the capsules over time (such a property is referred to as "sustained release" in the art). Therefore, microencapsulation of active ingredients has been studied in various fields.

[0003] For example, natural essential oils have been used as insect repellents, antibacterial agents, etc. However, due to their high volatility, they have problems in terms of the sustainability of their effects and handling properties. Therefore, microencapsulation of natural essential oils has been attempted. Among natural essential oils, lemon eucalyptus oil, which has citronellal as its main component, is used as an insect repellent. As microcapsules encapsulating lemon eucalyptus oil, those having polyurethane as a constituent component of the wall material have been known so far (see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of microcapsules having polyurethane as a constituent component of the wall material, generally, the density of the wall material (film) is lower than that of microcapsules having polyurea as a constituent component of the wall material, and the encapsulated core substance is likely to leak out of the capsule. Therefore, in such microcapsules, the core substance, particularly a highly volatile component such as natural essential oil, cannot fully obtain the effects of microencapsulation. Therefore, the development of microcapsules having polyurea as a constituent component of the wall material is desired.

[0006] Polyurea is obtained, for example, by a polycondensation reaction of a polyisocyanate compound and a polyamine compound, and microcapsules having polyurea as a constituent component of the wall material are produced by performing this polycondensation reaction in the coexistence of a core substance. For example, when producing microcapsules having citronellal as a core substance and polyurea as a constituent component of the wall material, it is conceivable to perform a polycondensation reaction of a polyisocyanate compound and a polyamine compound in the coexistence of citronellal. However, since citronellal has a formyl group (-C(=O)-H), when attempting to perform a polycondensation reaction, the formyl group in citronellal and the amino group (-NH 2 ) in the polyamine compound react with each other, and an unintended reaction proceeds, resulting in insufficient formation of the wall material and the problem that the target microcapsules cannot be obtained.

[0007] An object of the present invention is to provide a microcapsule having polyurea as a constituent component of the wall material and encapsulating a core substance having a formyl group.

Means for Solving the Problems

[0008] The present invention provides a microcapsule having polyurea as a constituent component of the wall material, wherein the polyurea is a polycondensate of a polyisocyanate compound and a polyamine compound, the pH of an aqueous solution of the polyamine compound having a concentration of 1% by mass is 9 to 13, and the microcapsule encapsulates a component having a formyl group.

Effects of the Invention

[0009] According to the present invention, there is provided a microcapsule having a polyurea as a constituent component of a wall material and encapsulating a core substance having a formyl group.

Brief Description of Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0011] <<Microcapsule>> The microcapsule according to one embodiment of the present invention has a polyurea as a constituent component of a wall material, the polyurea is a polycondensate of a polyisocyanate compound and a polyamine compound, and the pH of an aqueous solution of the polyamine compound having a concentration of 1% by mass is 9 to 13, and the microcapsule encapsulates a component having a formyl group.

[0012] The microcapsules of the present embodiment have polyurea as a constituent component of the wall material. Since the polyamine compound, which is a raw material of this polyurea, has the above-described specific pH characteristics, even when a polycondensation reaction between this polyamine compound and a polyisocyanate compound is carried out in the coexistence of a component having a formyl group, the reaction between the polyamine compound and the component having a formyl group is suppressed. As a result, the polycondensation reaction between the polyisocyanate compound and the polyamine compound proceeds normally, so that the wall material is sufficiently formed, and microcapsules having polyurea as a constituent component of the wall material and encapsulating a component having a formyl group as a core material can be obtained without problems. The microcapsules of the present embodiment manufactured through such a normal process have normal and good characteristics.

[0013] From the structure of the polyurea constituting the microcapsules of the present embodiment, the polyisocyanate compound and the polyamine compound, which are its raw materials, can be specified. The microcapsules of the present embodiment only need to be those in which the pH of an aqueous solution of a specified polyamine compound at a concentration of 1% by mass is 9 to 13. In this specification, the "constituent component of the wall material" may be referred to as the "wall material component".

[0014] In this specification, "polyurea" means, unless otherwise specified, the "polycondensate of a polyamine compound having a pH of 9 to 13 in an aqueous solution with a concentration of 1% by mass and a polyisocyanate compound" described above.

[0015] In this specification, the "polyisocyanate compound" means "a compound having two or more isocyanate groups (-NCO) in one molecule". Further, the "polyamine compound" means "a compound having two or more amino groups (-NH 2 ) in one molecule".

[0016] <Wall material, wall material component> The wall material component (constituent components of the wall material) is a polycondensate of the polyisocyanate compound and the polyamine compound, is a polyurea, and is an oligomer or a polymer. The wall material component has a film-forming ability. The wall material encapsulates a component having a formyl group as a core substance and constitutes a microcapsule.

[0017] The thickness of the film or layer of the wall material is not particularly limited and may be, for example, 50 to 1000 nm.

[0018] [Polyamine compound] In this specification, unless otherwise specified, the "polyamine compound" means the above-mentioned "polyamine compound having a pH of 9 to 13 in an aqueous solution having a concentration of 1% by mass".

[0019] In the present embodiment, the "aqueous solution of a polyamine compound having a concentration of 1% by mass" means "in an aqueous solution of a polyamine compound, the ratio of the content (parts by mass) of the polyamine compound to the total mass (parts by mass) of the aqueous solution of the polyamine compound is 1% by mass".

[0020] In the present embodiment, the polyamine compound has two or more amino groups (-NH 2 ) in one molecule, and is not particularly limited as long as the pH of an aqueous solution having a concentration of 1% by mass is 9 to 13.

[0021] The pH of an aqueous solution of a polyamine compound having a concentration of 1% by mass may be, for example, any one of 10 to 13 and 11 to 13, or any one of 9 to 12 and 9 to 11.

[0022] The pH of the aqueous solution of the polyamine compound is preferably the pH when the temperature of the aqueous solution is 20 to 25°C. By using polyurea made from such a polyamine compound as a raw material, microcapsules encapsulating a component having a formyl group as a core substance can be obtained in a higher yield.

[0023] The number of amino groups that the polyamine compound has in one molecule is not particularly limited as long as it is 2 or more, but is preferably 2 to 6, more preferably 2 to 5, even more preferably 2 to 4, and particularly preferably 2 or 3.

[0024] The polyamine compound preferably has no isocyanate group or hydroxyl group, and more preferably has neither an isocyanate group nor a hydroxyl group.

[0025] The polyamine compound is preferably an organic polyvalent amine compound. The organic polyvalent amine compound may have only a chain structure, only a cyclic structure, or both a chain structure and a cyclic structure. The chain structure may be a linear structure or a branched-chain structure. The cyclic structure may be a monocyclic structure or a polycyclic structure. Examples of the group having a chain structure include a chain aliphatic hydrocarbon group. Examples of the group having a cyclic structure include a cyclic aliphatic hydrocarbon group and an aromatic hydrocarbon group.

[0026] The organic polyvalent amine compound having a cyclic structure may have only one cyclic structure or two or more cyclic structures. When having two or more cyclic structures, these cyclic structures may all be the same, all different, or only some of them may be the same. Also, when the organic polyvalent amine compound has two or more cyclic structures, their combination and ratio can be arbitrarily selected.

[0027] Preferred examples of the organic polyvalent amine compound include, for example, an aliphatic polyvalent amine compound having a structure in which two or more hydrogen atoms (-H) of an aliphatic hydrocarbon are substituted with amino groups (-NH 2 ); an NH-substituted aliphatic polyvalent amine compound having a structure in which one or two or more methylene groups (-CH 2 -) of the aliphatic polyvalent amine compound are substituted with a group represented by the formula "-NH-", and the like.

[0028] In the polyamine compound, the bonding position of the amino group is not particularly limited. For example, in an aliphatic polyvalent amine compound having a chain structure, the amino group may be bonded to a carbon atom at the terminal of the main chain or side chain, or may be bonded to a carbon atom at a non-terminal part of the main chain or side chain. For example, in an aliphatic polyvalent amine compound having a cyclic structure, the amino group may be bonded to adjacent carbon atoms among the carbon atoms constituting the ring skeleton, or may be bonded to non-adjacent carbon atoms. In the aliphatic polyvalent amine compound, it is preferable that two or more amino groups are not bonded to the same carbon atom.

[0029] In this specification, the "main chain" means the one continuous chain-like skeleton present in the molecule that has the largest number of atoms forming this chain-like skeleton. The "side chain" means a one continuous chain-like skeleton present in the molecule that does not correspond to the main chain.

[0030] In the NH-substituted aliphatic polyvalent amine compound, the position of the methylene group substituted with the group represented by the formula "-NH-" is not particularly limited, but it is preferably a methylene group not adjacent to the carbon atom to which the amino group is bonded. In the NH-substituted aliphatic polyvalent amine compound, the number of methylene groups substituted with the group represented by the formula "-NH-" varies depending on the number of carbon atoms of this amine compound, and may be, for example, any of 1 to 4, 1 to 3, or 1 to 2.

[0031] The amine compound used in the formation of the wall material component (in other words, the structural unit derived from the amine compound that the wall material component has) may be only one kind, or may be two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected.

[0032] The polyamine compound is preferably the organic polyvalent amine compound having both a chain structure and a cyclic structure, more preferably the organic polyvalent amine compound having both a cyclic aliphatic hydrocarbon group and a chain aliphatic hydrocarbon group, and still more preferably the organic polyvalent amine compound having a structure in which hydrogen atoms bonded to two or more different carbon atoms constituting the ring skeleton of cycloalkane are substituted with aminoalkyl groups. Examples of such an organic polyvalent amine compound include 1,3-bis(aminomethyl)cyclohexane and the like.

[0033] When forming the wall material component, as a compound having two or more amino groups (-NH 2 ) in one molecule, in addition to the polyamine compound (the polyamine compound having a pH of 9 to 13 in an aqueous solution with a concentration of 1% by mass), other compounds (which may be abbreviated as "other polyamine compounds" in this specification) may be used. That is, the polyurea may be a polycondensate of the polyisocyanate compound, the polyamine compound, and other polyamine compounds.

[0034] The other polyamine compound has two or more amino groups in one molecule, and is not particularly limited as long as the pH of an aqueous solution having a concentration of 1% by mass is less than 9 or more than 13.

[0035] The other polyamine compound used when forming the wall material component (in other words, the structural unit derived from the other polyamine compound included in the wall material component) may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected.

[0036] In the wall material component, the ratio of the number of structural units derived from the other polyamine compound to the total number of the structural unit derived from the polyamine compound and the structural unit derived from the other polyamine compound ([the number of structural units derived from the other polyamine compound in the wall material component] / ([the number of structural units derived from the polyamine compound in the wall material component]+[the number of structural units derived from the other polyamine compound in the wall material component])×100) is preferably 10% or less, more preferably 5% or less, still more preferably 3% or less, and particularly preferably 1% or less. The microcapsules with such a ratio can be obtained in a higher yield.

[0037] [Polyisocyanate compound] In the present embodiment, the polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups (-NCO) in one molecule. The polyisocyanate compound may be a polyisocyanate modified product. That is, the polyisocyanate compound may be either a polyisocyanate modified product or a non-modified polyisocyanate.

[0038] The number of isocyanate groups that the polyisocyanate compound has in one molecule is not particularly limited as long as it is two or more, but is preferably two or three.

[0039] In the polyisocyanate compound, the bonding position of the isocyanate group is not particularly limited.

[0040] (Non-modified polyisocyanate) Among the polyisocyanate compounds, examples of the non-modified polyisocyanate include aliphatic polyisocyanate compounds having a structure in which two or more hydrogen atoms (-H) of an aliphatic hydrocarbon are substituted with isocyanate groups (-N=C=O); aromatic polyisocyanate compounds having a structure in which two or more hydrogen atoms of an aromatic hydrocarbon are substituted with isocyanate groups, and the like.

[0041] The aliphatic hydrocarbon group in the aliphatic polyisocyanate compound may be linear, branched or cyclic. In this specification, a cyclic aliphatic group may be referred to as an "aliphatic cyclic group". The cyclic aliphatic group (aliphatic cyclic group) has a cyclic structure and may or may not have a chain (i.e., linear or branched) structure, that is, it has at least a cyclic structure. The aliphatic cyclic group may be monocyclic or polycyclic. The aromatic hydrocarbon group in the aromatic polyisocyanate compound may be monocyclic or polycyclic.

[0042] In the aliphatic polyisocyanate compound and the aromatic polyisocyanate compound having a chain structure, the isocyanate group may be bonded to a carbon atom at the terminal of the main chain or side chain in the chain structure, or may be bonded to a carbon atom at a non-terminal part of the main chain or side chain in the chain structure. In the aliphatic polyisocyanate compound and the aromatic polyisocyanate compound having a cyclic structure and no chain structure, the isocyanate group may be bonded to adjacent carbon atoms among the carbon atoms constituting the ring skeleton, or may be bonded to non-adjacent carbon atoms. In the aliphatic polyisocyanate compound and the aromatic polyisocyanate compound, it is preferable that two or more isocyanate groups are not bonded to the same carbon atom.

[0043] Examples of the aliphatic polyisocyanate compound include pentamethylene diisocyanate (which may be abbreviated as "PDI" in this specification), hexamethylene diisocyanate (which may be abbreviated as "HDI" in this specification), 2,4,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, and the like. Examples of the aromatic polyisocyanate compound include tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate (in this specification, tolylene diisocyanate may be abbreviated as "TDI"), xylylene-1,3-diisocyanate, xylylene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-2,4'-diisocyanate, polymethylene polyphenyl polyisocyanate (in this specification, it may be referred to as "polymeric MDI"), and the like.

[0044] The polymeric MDI is represented by the following general formula (P1).

[0045] [Chemical formula] (In the formula, n is an integer of 0 or more.)

[0046] In the general formula (P1), n may be any integer of 0 or more, for example, it may be 0 to 100.

[0047] The NCO content of the polymeric MDI can be adjusted as appropriate, for example, it may be 30 to 32% by mass.

[0048] The polymeric MDI is liquid at normal temperature, and its viscosity at 25°C is not particularly limited, but it is preferably 150 to 250 mPa·s. In this specification, "normal temperature" means a temperature without particularly cooling or heating, that is, the ordinary temperature, for example, a temperature of 15 to 25°C and the like.

[0049] There are multiple types of polymeric MDI depending on the value of n. The polymeric MDI used in the formation of the wall material component (in other words, the structural unit derived from polymeric MDI in the wall material component) may be only one type, or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected.

[0050] (Polyisocyanate modified product) Among the polyisocyanate compounds, examples of the polyisocyanate modified product include modified products of the aliphatic polyisocyanate compound, modified products of the aromatic polyisocyanate compound, and the like.

[0051] More specifically, examples of the polyisocyanate modified product include isocyanurate modified products of diisocyanate, biuret modified products, trimethylolpropane adduct modified products, allophanate modified products, and the like. For example, examples of the isocyanurate modified product include isocyanurate modified products of PDI, isocyanurate modified products of HDI, and the like. Examples of the biuret modified product include biuret modified products of HDI. In this specification, for example, "isocyanurate modified product of diisocyanate" may be described as "diisocyanate-isocyanurate modified product". The same applies to the other diisocyanate modified products.

[0052] The polyisocyanate compound used for forming the wall material component (in other words, the structural unit derived from the polyisocyanate compound that the wall material component has) may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected. For example, the wall material component may have only one type or two or more types of structural units derived from a polyisocyanate non-modified product as the structural unit derived from the polyisocyanate compound, or may have only one type or two or more types of structural units derived from a polyisocyanate modified product, or may have both one type or two or more types of structural units derived from a polyisocyanate non-modified product and structural units derived from a polyisocyanate modified product.

[0053] The polyisocyanate compound is preferably the polyisocyanate modified product, and more preferably the isocyanurate modified product of the polyisocyanate. Examples of such isocyanurate-modified polyisocyanates include PDI-isocyanurate-modified products, HDI-isocyanurate-modified products, TDI-isocyanurate-modified products, and the like.

[0054] In the present embodiment, it is also preferable to use polymeric MDI and a polyisocyanate compound other than polymeric MDI in combination as the polyisocyanate compound. That is, as a structural unit derived from the polyisocyanate compound, the wall material component preferably has one or more kinds each of a structural unit derived from polymeric MDI and a structural unit derived from a polyisocyanate compound other than polymeric MDI. Microcapsules having such a wall material component have improved properties such as excellent handleability, and further have high stability during storage, particularly high stability during storage under heating conditions (during heat storage), and have heat resistance.

[0055] When polymeric MDI and a polyisocyanate compound other than polymeric MDI are used in combination as described above, it is preferable to use polymeric MDI and the isocyanurate-modified polyisocyanate in combination, and it is more preferable to use polymeric MDI and a PDI-isocyanurate-modified product, an HDI-isocyanurate-modified product or a TDI-isocyanurate-modified product in combination. By using such polyisocyanate compounds in combination, the stability of the above microcapsules during storage becomes higher.

[0056] When using polymeric MDI and a polyisocyanate compound other than polymeric MDI in combination, in the wall material component, the amount of the structural unit derived from polymeric MDI is preferably 0.1 to 2 times by mass, more preferably 0.2 to 1.5 times by mass, and even more preferably 0.3 to 1 times by mass, relative to the amount of the structural unit derived from the polyisocyanate compound other than polymeric MDI. When the amount of the structural unit derived from polymeric MDI is at or above the lower limit value, the above-described effects obtained by having the structural unit derived from polymeric MDI become higher. A wall material component in which the amount of the structural unit derived from polymeric MDI is at or below the upper limit value is easier to form.

[0057] The wall material component may contain only the above-mentioned polyurea (a polycondensate of a polyamine compound and a polyisocyanate compound having a pH of 9 to 13 in an aqueous solution with a concentration of 1% by mass), or may contain the above-mentioned polyurea and either one or both of other oligomers and polymers within a range that does not impair the effects of the present invention.

[0058] Examples of the other oligomers or polymers include polyurea other than the above-mentioned polyurea (a polycondensate of a polyamine compound and a polyisocyanate compound having a pH of 9 to 13 in an aqueous solution with a concentration of 1% by mass) (which may be abbreviated as "other polyurea" in this specification), and resin components that do not correspond to either the above-mentioned polyurea or other polyurea.

[0059] Any of the other oligomers and polymers contained in the wall material component may be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected.

[0060] In the microcapsules of the present embodiment, the ratio ([total content of the other oligomers and polymers in the wall material component (parts by mass)] / [total mass of the wall material component in the microcapsules (parts by mass)] × 100) of the total content of the other oligomers and polymers in the wall material component to the total mass of the wall material component is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 1% by mass or less. In other words, in the microcapsules, the ratio ([content of the polyurea in the wall material component in the microcapsules (parts by mass)] / [total mass of the wall material component in the microcapsules (parts by mass)] × 100) of the content of the polyurea in the wall material component to the total mass of the wall material component is preferably 95% by mass or more, more preferably 97% by mass or more, and particularly preferably 99% by mass or more. The microcapsules with these ratios within such ranges can be obtained in a higher yield.

[0061] <Component having a formyl group> The component having the formyl group (-C(=O)-H) is the core substance encapsulated in the microcapsules of the present embodiment, and is not particularly limited as long as it has a formyl group.

[0062] The component having the formyl group is preferably an oily component (an oily component having a formyl group). The microcapsules in which the core substance is an oily component can be manufactured more easily. In the present embodiment, the "oily component" means "a component having an SP value (solubility parameter) of 8 to 10 (cal / cm 3 ) 1 / 2 .

[0063] Examples of the oily component include essential oils and the like.

[0064] The component having the formyl group is preferably liquid at room temperature.

[0065] The component having the formyl group may be, for example, either a natural component extracted from a natural product or a synthetic component. Preferred components having the formyl group include, for example, natural essential oils and the like.

[0066] The component having the formyl group encapsulated in the microcapsules of the present embodiment may be only one kind or two or more kinds. When there are two or more kinds, their combinations and ratios can be arbitrarily selected.

[0067] The average particle diameter of the microcapsules is not particularly limited and may be, for example, 0.1 to 100 μm.

[0068] In this specification, the "average particle diameter" means the median diameter of the volume particle size distribution measured for the particles using a particle size distribution meter, unless otherwise specified.

[0069] <<Method for Producing Microcapsules>> The microcapsules can be produced by subjecting the polyisocyanate compound, the polyamine compound, and, if necessary, the other polyamine compound to a polycondensation reaction in the coexistence of the component having the formyl group.

[0070] In the present embodiment, by selecting only the polyamine compound as the reaction object of the polyisocyanate compound or selecting the polyamine compound as the main reaction object of the polyisocyanate compound, even if the component serving as the core material has a formyl group, the target microcapsules can be obtained without problems.

[0071] At the time of the polycondensation reaction, other components not corresponding to any of the polyisocyanate compound, the polyamine compound, and the other polyamine compound may be used. Examples of the other components include solvents, emulsifiers, and the like. For example, in the coexistence of water and a hydrophobic component, a polycondensation reaction can be carried out, and the polycondensation can be carried out as interfacial polycondensation.

[0072] Among the other components, examples of the solvent include water, organic solvents, and the like. The organic solvent may be either a hydrophilic solvent or a hydrophobic solvent, but is preferably a hydrophobic solvent. Examples of the hydrophobic solvent include alcohols, amides, nitriles, ketones, esters, ethers, hydrocarbons, halogenated hydrocarbons, phenols (compounds having phenolic hydroxyl groups), carbon disulfide, carboxylic acids, and the like.

[0073] Among the other components, examples of the emulsifier include known ones. Examples of the emulsifier include polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, ethyl cellulose, methyl cellulose, casein, gum arabic, gelatin, rosin oil, alkylbenzene sulfonates such as sodium benzenesulfonate and sodium dodecylbenzenesulfonate, polyoxyethylene sulfates, ethylene-maleic anhydride copolymers, styrene-maleic anhydride copolymers, isobutylene-maleic anhydride copolymers, poly(meth)acrylic acid, and the like. In this specification, “(meth)acrylic acid” is a concept that includes both “acrylic acid” and “methacrylic acid”.

[0074] In terms of the emulsification state of the reaction solution during the polycondensation reaction being better and microcapsules being more easily produced, the emulsifier is preferably polyvinyl alcohol.

[0075] Each of the component having a formyl group, the polyisocyanate compound, the polyamine compound, the other polyamine compound, and the other components used during the polycondensation reaction may be only one kind or two or more kinds. In the case of two or more kinds, their combinations and ratios can be arbitrarily selected.

[0076] In the polycondensation reaction, the amount of the polyisocyanate compound used is, for example, preferably 10 to 50 parts by mass, more preferably 12.5 to 47.5 parts by mass, still more preferably 15 to 45 parts by mass, and may be 20 to 40 parts by mass or 25 to 45 parts by mass, based on 100 parts by mass of the amount of the component having a formyl group used. When the amount of the polyisocyanate compound used is at least the lower limit value, microcapsules having a large inclusion amount of the component having a formyl group can be produced more stably. When the amount of the polyisocyanate compound used is at most the upper limit value, microcapsules having a large inclusion amount of the component having a formyl group can be produced more stably while suppressing the excessive use of the polyisocyanate compound.

[0077] As described above, when using polymeric MDI and a polyisocyanate compound other than polymeric MDI in combination as the polyisocyanate compound, the amount (mass ratio) of polymeric MDI used with respect to the amount of the polyisocyanate compound other than polymeric MDI during the polycondensation reaction is preferably the same as the amount (mass ratio) of the structural unit derived from polymeric MDI with respect to the amount of the structural unit derived from the polyisocyanate compound other than polymeric MDI in the wall material component described above.

[0078] In the polycondensation reaction, the total amount of the polyisocyanate compound used and the total amount of the polyamine compound and other polyamine compounds is preferably an amount such that the molar ratio of [the total number of moles of amino groups in the polyamine compound and the amino groups in the other polyamine compounds]:[the number of moles of isocyanate groups in the polyisocyanate compound] is 10:90 to 60:40, and more preferably an amount such that the molar ratio is 20:80 to 40:60. When the total number of moles of the amino groups is set to be less than the number of moles of the isocyanate groups in the polyisocyanate compound, higher-quality microcapsules can be obtained.

[0079] During the polycondensation reaction, the ratio ([amount of the other polyamine compound (mol)] / ([amount of the polyamine compound (mol)] + [amount of the other polyamine compound (mol)]) × 100) of the amount of the other polyamine compound used (mol) to the total amount of the polyamine compound and the other polyamine compound used (mol) is preferably 10 mol% or less, more preferably 5 mol% or less, still more preferably 3 mol% or less, and particularly preferably 1 mol% or less. The microcapsules with the ratio within such a range can be obtained in a higher yield.

[0080] During the polycondensation reaction, the amount of the other component used can be appropriately adjusted according to its type. For example, when the other component is a solvent, the amount of the other component (solvent) used is preferably 20 to 280 parts by mass with respect to 100 parts by mass of the total amount of the component having a formyl group, the polyisocyanate compound, the polyamine compound, and the other polyamine compound. For example, it may be any one of 20 to 150 parts by mass, 25 to 100 parts by mass, and 30 to 70 parts by mass, or it may be any one of 150 to 280 parts by mass, 175 to 270 parts by mass, and 200 to 260 parts by mass.

[0081] For example, when the other component is an emulsifier, the amount of the emulsifier used is preferably 20 to 45 parts by mass with respect to 100 parts by mass of the total amount of the polyisocyanate compound, the polyamine compound, and the other polyamine compound. For example, it may be any one of 25 to 40 parts by mass, 27.5 to 37.5 parts by mass, and 30 to 35 parts by mass, or it may be any one of 20 to 25 parts by mass and 20 to 23 parts by mass. When the amount used is equal to or higher than the lower limit value, the emulsification state of the reaction solution during the polycondensation reaction becomes better. When the amount used is equal to or lower than the upper limit value, excessive use of the emulsifier is suppressed.

[0082] For example, when the other component does not correspond to either the solvent or the emulsifier, the amount of the other component used is preferably 10 parts by mass or less, for example, either 5 parts by mass or less and 1 part by mass or less, based on 100 parts by mass of the total amount of the component having a formyl group, the polyisocyanate compound, the polyamine compound, and the other polyamine compound.

[0083] The temperature when carrying out the polycondensation reaction (i.e., the reaction temperature) is not particularly limited, but is preferably 60 to 110°C, for example, either 65 to 100°C or 70 to 90°C.

[0084] The time for carrying out the polycondensation reaction (i.e., the reaction time) is preferably 0.5 to 5 hours, for example, either 1 to 4 hours or 1.5 to 3 hours.

[0085] After the polycondensation reaction, for example, the microcapsules are obtained as a dispersion such as an aqueous dispersion.

[0086] The obtained microcapsules may be used as they are for the intended use, or may be post-treated, purified, etc. by known methods as necessary and then used for the intended use, or may be used for the intended use after removing the dispersion medium.

[0087] When using the solvent other than water during the polycondensation reaction, the obtained microcapsules may encapsulate this solvent in addition to the component having a formyl group. Also, depending on the conditions of the polycondensation reaction, the microcapsules may encapsulate a component that does not correspond to either the component having a formyl group or the solvent (which may be abbreviated as "other core substance" in this specification).

[0088] Both the solvent and the other core substance encapsulated in the microcapsules may each be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected.

[0089] The inclusion amounts of the component having the formyl group, the solvent, and other core substances in the microcapsules can be adjusted according to the manufacturing conditions of the microcapsules.

[0090] The rotation speed of the stirring means during the polycondensation reaction (in other words, the stirring speed of the reaction solution) may be, for example, either 300 to 900 rpm or 400 to 700 rpm. For example, when the usage amount of the component having the formyl group during the polycondensation reaction is 30 to 100 g, such a stirring speed is particularly suitable. However, the usage amount of the component having the formyl group is not limited thereto.

[0091] As an example of a more specific method for manufacturing microcapsules, for example, a step of adding a second solution containing the component having the formyl group and the polyisocyanate compound to a first solution containing water and an emulsifier to obtain an emulsion (in this specification, it may be abbreviated as "emulsification step"), and adding water and the polyamine compound to the emulsion, or adding a third solution containing water and the polyamine compound to perform a polycondensation reaction (in this specification, it may be abbreviated as "polycondensation step"). A manufacturing method having these steps (in this specification, it may be referred to as "manufacturing method (I)") can be mentioned. However, the manufacturing method of the microcapsules is not limited to this manufacturing method (I). Hereinafter, the manufacturing method (I) will be described.

[0092] <Emulsification step> In the emulsification step of the manufacturing method (I), the second solution is added to the first solution to obtain an emulsion.

[0093] [First solution] The first solution contains water and an emulsifier, and may contain other components that do not correspond to either water or the emulsifier as necessary, as long as the effects of the present invention are not impaired.

[0094] The emulsifier and other components used in the preparation of the first solution may each be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected.

[0095] In the first solution, the proportion of the content of the emulsifier relative to its total mass (i.e., the concentration of the emulsifier in the first solution) is not particularly limited, but is preferably 1 to 15% by mass, and more preferably 2 to 8% by mass.

[0096] When the first solution contains the other components, the content of the other components can be appropriately adjusted according to the purpose.

[0097] The first solution is obtained by mixing water, an emulsifier, and, if necessary, the other components. The first solution is preferably prepared by adding an emulsifier to water. When using the other components, the timing of addition and the object of addition can be appropriately adjusted according to the type of the other components. When preparing the first solution, for example, after mixing all the components, it is preferably heated and stirred at 80 to 100 °C for preferably 0.5 to 3 hours, and then cooled to room temperature such as 27 °C or lower to prepare the first solution.

[0098] [Second Solution] The second solution contains the polyisocyanate compound and the component having a formyl group, and may further contain other components that do not fall under either the polyisocyanate compound or the component having a formyl group, as long as the effects of the present invention are not impaired.

[0099] The polyisocyanate compound, the component having a formyl group, and other components used in the preparation of the second solution may each be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected.

[0100] In the manufacturing method (I), in the second solution, the content of the polyisocyanate compound may be, for example, preferably 15 to 45 parts by mass, 20 to 40 parts by mass, or 25 to 35 parts by mass with respect to 100 parts by mass of the content of the component having a formyl group. It may be either 25 to 45 parts by mass or 35 to 45 parts by mass, or either 15 to 35 parts by mass or 15 to 25 parts by mass.

[0101] Examples of the other components in the second solution include a solvent. By using the solvent, the solubility of the contained components in the second solution can be adjusted. Examples of the solvent in the second solution include water, organic solvents, etc. The organic solvents are the same as those described above.

[0102] When the second solution contains the other components, the content of the other components can be appropriately adjusted according to the purpose.

[0103] The second solution is obtained by mixing the polyisocyanate compound, the component having a formyl group, and, if necessary, the other components. When the component having a formyl group is liquid at room temperature, the second solution is preferably prepared by adding the component having a formyl group and, if necessary, other components to the polyisocyanate compound. When preparing the second solution, for example, from the blending of the raw materials (the polyisocyanate compound, the component having a formyl group, the other components) to the stirring after all the components are blended can preferably be carried out at 15 to 28°C. The stirring time after all the components are blended may be, for example, 1 to 60 minutes.

[0104] In the emulsification step, when adding the second solution to the first solution, the second solution may be added all at once or dropwise.

[0105] In the emulsification step, for example, from the initial stage of adding the second solution to the first solution to the stirring after addition, it can be preferably carried out at 15 to 28°C. The stirring time after adding the second solution to the first solution may be, for example, 1 to 60 minutes.

[0106] In the emulsification step, when obtaining an emulsion by adding the second solution to the first solution and stirring the resulting mixture, the particle diameter (average particle diameter) of the microcapsules can be adjusted by adjusting the stirring speed of the mixture. More specifically, the slower the above-mentioned stirring speed, the larger the particle diameter of the microcapsules tends to be, and the faster the above-mentioned stirring speed, the smaller the particle diameter of the microcapsules tends to be.

[0107] The stirring speed of the mixture (in other words, the rotational speed of the stirring means) when obtaining the emulsion may be, for example, either 3000 to 10000 rpm or 4000 to 8000 rpm. For example, when the usage amount of the component having a formyl group during emulsification is 30 to 100 g, such a stirring speed is particularly suitable. However, the usage amount of the component having a formyl group is not limited thereto.

[0108] <Polycondensation step> In the polycondensation step, water and the polyamine compound are added to the emulsion obtained in the emulsification step, or the third solution is added to carry out a polycondensation reaction.

[0109] [Third solution] The third solution contains water, the polyamine compound, and, if necessary, the other polyamine compound, and may further contain other components that do not fall under any of these components (water, the polyamine compound, the other polyamine compound) as long as the effects of the present invention are not impaired.

[0110] The polyamine compound, other polyamine compounds, and other components used in the preparation of the third solution may each be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected.

[0111] In the third solution, the ratio of the total content of the polyamine compound and other polyamine compounds to the total mass (i.e., the total concentration of the polyamine compound and other polyamine compounds in the third solution) is not particularly limited. For example, it may be either 5 to 40% by mass or 10 to 30% by mass, or it may be 5 to 20% by mass.

[0112] When the third solution is not used, water, the polyamine compound, and, if necessary, the other polyamine compound are added to the emulsion, and other components that do not fall under any of these components (water, the polyamine compound, the other polyamine compound) may be added as long as the effects of the present invention are not impaired.

[0113] When the third solution is not used, the polyamine compound, other polyamine compounds, and other components added to the emulsion may each be only one type or two or more types. When there are two or more types, their combinations and ratios can be arbitrarily selected.

[0114] In the production method (I), when the third solution is used, the amounts of the first solution, the second solution, and the third solution may be adjusted so that the amount of the emulsifier in the first solution, the amounts of the polyisocyanate compound and the component having a formyl group in the second solution, and the amounts of the polyamine compound and the other polyamine compounds in the third solution are in the relationship described above. In the production method (I), when the third solution is not used, the amounts of the emulsifier in the first solution, the polyisocyanate compound and the component having a formyl group in the second solution, the polyamine compound added to the emulsion, and the other polyamine compound are adjusted so as to satisfy the relationships described above. That is, the amounts of the first solution, the second solution, the polyamine compound, and the other polyamine compound may be adjusted.

[0115] When the third solution contains the other components, the content of the other components can be appropriately adjusted according to the purpose. When using the other components without using the third solution, the amount of the other components used can be appropriately adjusted according to the purpose.

[0116] The third solution is obtained by mixing water, the polyamine compound, and, if necessary, the other polyamine compound and, if necessary, the other components. The third solution may be prepared, for example, by adding water to the polyamine compound or by adding the polyamine compound to water. When using the other polyamine compound or other components, the timing of addition and the target of addition can be appropriately adjusted according to the type of the other polyamine compound or other components. When preparing the third solution, for example, after mixing all the components, the third solution may be prepared by stirring at preferably 15 to 28°C for preferably 1 to 60 minutes.

[0117] In the polycondensation step, when adding the third solution to the emulsion, the third solution may be added all at once or dropwise. In the polycondensation step, when adding water, the polyamine compound, and, if necessary, the other polyamine compound and, if necessary, the other components to the emulsion without using the third solution, these components may be added all at once or separately.

[0118] In the production method (I), in the polycondensation step, it is preferable to set the reaction temperature, reaction time, and stirring speed of the reaction solution to the reaction temperature, reaction time, and stirring speed of the reaction solution when performing the polycondensation reaction described above.

[0119] In the production method (I), by performing the polycondensation step, the microcapsules are obtained as an aqueous dispersion.

[0120] Regardless of the production method, the microcapsules of the present embodiment can be made to have sustained release properties, gradually releasing the component having the formyl group encapsulated therein to the outside over time. Therefore, even when the volatility of the component having the formyl group is high, the microcapsules can sustain the action of the component having the formyl group for a long time. Further, even when the volatility of the component having the formyl group is high, the microcapsules are excellent in handleability.

[0121] The microcapsules are suitable, for example, as insect repellents, antibacterial agents, and the like. For example, by preparing a liquid composition containing the microcapsules or using, as it is, the product of the polycondensation reaction obtained by the above-described production method, a liquid insect repellent, antibacterial agent, or the like can be obtained. Further, by applying and drying these liquid insect repellents, antibacterial agents, or the like, a layered (for example, film-like) insect repellent, antibacterial agent, or the like can be obtained. Also, by preparing a resin composition containing the microcapsules and molding this resin composition, a solid insect repellent or antibacterial agent in the form of a sheet or the like can be obtained.

Example

[0122] Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples shown below.

[0123] [Example 1] <<Production of Microcapsules>> To 144 g of distilled water, 6 g of polyvinyl alcohol (manufactured by Nippon Gohsei Kasei Co., Ltd., "JP-24", saponification degree: 87 - 89) was added, and the mixture was stirred at 90 °C for 1 hour to form a solution, which was then cooled to 25 °C to obtain an aqueous polyvinyl alcohol solution with a concentration of 4 mass% (corresponding to the first solution).

[0124] Separately, at room temperature, 50 g of lemon eucalyptus oil (manufactured by Ash Co., Ltd., main component: citronellal) was added to 15 g of PDI-isocyanurate modified product (manufactured by Mitsui Chemicals, Inc., "Stabio D-370N"), and the mixture was stirred until it became transparent to obtain a mixed solution in which all these components were dissolved (corresponding to the second solution).

[0125] At room temperature, the total amount of the mixed solution was added to the total amount of the aqueous polyvinyl alcohol solution, and the mixture was stirred for 3 minutes at a rotation speed of 7000 rpm using a homogenizer (manufactured by Primix Co., Ltd.) to obtain an emulsion (corresponding to the emulsification step).

[0126] To the total amount of the obtained emulsion, 4 g of 1,3-bis(aminomethyl)cyclohexane (manufactured by Tokyo Chemical Industry Co., Ltd.) and 20 g of distilled water were added, and the reaction solution was stirred at 80 °C with an anchor blade rotating at 500 rpm for 2 hours to perform interfacial polycondensation (corresponding to the polycondensation step). During this period, the properties of the reaction product were observed from the viewpoints of color and viscosity. The results are shown in Table 2. Also, the structure of 1,3-bis(aminomethyl)cyclohexane and the pH of its 1 mass% aqueous solution are shown in Table 1.

[0127] As described above, a microcapsule in which a polycondensate of 1,3-bis(aminomethyl)cyclohexane and a PDI-isocyanurate modified product (i.e., polyurea) is used as a wall material component and lemon eucalyptus oil is used as a core substance and encapsulated by the wall material was obtained as an aqueous dispersion.

[0128] <<Evaluation of Microcapsules>> <Evaluation of the Degree of Microcapsule Formation> Using a wire bar (No. 30), the product obtained in the polycondensation step above (i.e., the microcapsule aqueous dispersion) was coated on high-quality paper and dried at 105°C for 1 minute using an oven. Next, using a scanning electron microscope (manufactured by JEOL Ltd.), the obtained dried product was observed at magnifications of 2500 times or 1000 times. Then, by confirming the degree of wall material formation, the degree of microcapsule formation was evaluated according to the following criteria. The results are shown in Table 2. Also, the imaging data of the dried product obtained at this time is shown in Figure 1. [Evaluation Criteria] A: The wall material is formed normally, and microcapsules are formed normally. B: The wall material is not formed normally, and microcapsules are not formed.

[0129] <<Manufacture and Evaluation of Microcapsules>> [Comparative Example 1] As shown in Table 1, except that 1,3-diaminopropane (4 g, manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 1,3-bis(aminomethyl)cyclohexane (4 g), the manufacture and evaluation of microcapsules were attempted in the same manner as in Example 1. However, the observation of the dried product using the scanning electron microscope was performed at a magnification of 2000 times instead of 2500 times. The results are shown in Table 2 and Figure 2. Figure 2 is the imaging data of the dried product obtained in this comparative example.

[0130] [Comparative Example 2] As shown in Table 1, except that diethylenetriamine (4 g, manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 1,3-bis(aminomethyl)cyclohexane (4 g), the manufacture and evaluation of microcapsules were attempted in the same manner as in Example 1. The results are shown in Table 2 and Figure 3. Figure 3 is the imaging data of the dried product obtained in this comparative example.

[0131] [Comparative Example 3] As shown in Table 1, except that N,N'-bis(3-aminopropyl)ethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) (4 g) was used instead of 1,3-bis(aminomethyl)cyclohexane (4 g), the production and evaluation of microcapsules were attempted in the same manner as in Example 1. The results are shown in Table 2 and Figure 4. Figure 4 is the imaging data of the dried product obtained in this comparative example.

[0132] [Comparative Example 4] As shown in Table 1, except that urea (manufactured by Tokyo Chemical Industry Co., Ltd.) (4 g) was used instead of 1,3-bis(aminomethyl)cyclohexane (4 g), the production and evaluation of microcapsules were attempted in the same manner as in Example 1. The results are shown in Table 2.

[0133] [Comparative Example 5] As shown in Table 1, except that adipic dihydrazide (manufactured by Tokyo Chemical Industry Co., Ltd.) (4 g) was used instead of 1,3-bis(aminomethyl)cyclohexane (4 g), the production and evaluation of microcapsules were attempted in the same manner as in Example 1. The results are shown in Table 2 and Figure 5. Figure 5 is the imaging data of the dried product obtained in this comparative example.

[0134] [Example 2] [Manufacture of Microcapsules] An aqueous polyvinyl alcohol solution (corresponding to the first solution) with a concentration of 4% by mass was prepared in the same manner as in Example 1.

[0135] Separately, at room temperature, to a mixture of a PDI-isocyanurate modified product (Stabio D-370N manufactured by Mitsui Chemicals, Inc.) (15 g) and polymeric MDI (Millionate MR-200 manufactured by Tosoh Corporation, NCO content 31.3% by mass) (7.5 g), lemon eucalyptus oil (manufactured by Ash Co., main component: citronellal) (50 g) was added and stirred until it became transparent to obtain a mixed solution (corresponding to the second solution) in which all these components were dissolved.

[0136] At room temperature, the total amount of the mixed solution was added to the total amount of the polyvinyl alcohol aqueous solution, and the mixture was stirred for 3 minutes at a rotation speed of 7000 rpm using a homogenizer (manufactured by Primix Corporation) to obtain an emulsion (corresponding to the emulsification step).

[0137] To the total amount of the obtained emulsion, 1,3-bis(aminomethyl)cyclohexane (manufactured by Tokyo Chemical Industry Co., Ltd.) (5.5 g) and distilled water (50 g) were added, and the reaction solution was stirred by rotating an anchor blade at 80 °C and a rotation speed of 500 rpm for 2 hours to perform interfacial polycondensation (corresponding to the polycondensation step). During this period, the properties of the reaction product were observed from the viewpoints of color and viscosity. The results are shown in Table 1.

[0138] As described above, a microcapsule in which a polycondensate (i.e., polyurea) of 1,3-bis(aminomethyl)cyclohexane and a PDI-isocyanurate modified product, and a polycondensate (i.e., polyurea) of 1,3-bis(aminomethyl)cyclohexane and polymeric MDI are used as wall material components and lemon eucalyptus oil is encapsulated as a core substance by the wall material was obtained as an aqueous dispersion.

[0139] [Evaluation of Microcapsules] The microcapsules obtained above were evaluated by the same method as in Example 1. The results are shown in Table 1. Also, the imaging data of the dried product obtained at this time are shown in Fig. 6.

[0140] [Example 3] [Manufacture of Microcapsules] Polyvinyl alcohol (manufactured by Nippon Gohsei Co., Ltd., "JP-24", saponification degree: 87 - 89) (10 g) was added to distilled water (240 g), and the mixture was stirred at 90 °C for 1 hour to form a solution, which was then cooled to 25 °C to obtain an aqueous polyvinyl alcohol solution with a concentration of 4 mass% (corresponding to the first solution).

[0141] Separately, at room temperature, to a mixture of a PDI-isocyanurate modified product (Stabio D-370N manufactured by Mitsui Chemicals, Inc.) (15 g) and polymeric MDI (Millionate MR-200 manufactured by Tosoh Corporation) (7.5 g), lemon eucalyptus oil (manufactured by Ash, main component: citronellal) (100 g) was added, and the mixture was stirred until it became transparent to obtain a mixed solution in which all these components were dissolved (corresponding to the second solution).

[0142] At room temperature, the total amount of the mixed solution was added to the total amount of the polyvinyl alcohol aqueous solution, and the mixture was stirred for 3 minutes at a rotation speed of 7000 rpm using a homogenizer (manufactured by Primix Corporation) to obtain an emulsion (corresponding to the emulsification step).

[0143] To the total amount of the obtained emulsion, 1,3-bis(aminomethyl)cyclohexane (manufactured by Tokyo Chemical Industry Co., Ltd.) (5.5 g) and distilled water (50 g) were added, and the reaction solution was stirred by rotating an anchor blade at 80 °C and a rotation speed of 500 rpm for 2 hours to perform interfacial polycondensation (corresponding to the polycondensation step). During this period, the properties of the reaction product were observed from the viewpoints of color and viscosity. The results are shown in Table 1.

[0144] As described above, a microcapsule in which a polycondensate of 1,3-bis(aminomethyl)cyclohexane and a PDI-isocyanurate modified product (i.e., polyurea), and a polycondensate of 1,3-bis(aminomethyl)cyclohexane and polymeric MDI (i.e., polyurea) are used as wall material components and lemon eucalyptus oil is used as a core substance and the wall material encapsulates the core substance was obtained as an aqueous dispersion.

[0145] <<Evaluation of Microcapsules>> The microcapsules obtained above were evaluated in the same manner as in Example 1. The results are shown in Table 1. Also, the imaging data of the dried product obtained at this time are shown in FIG. 7.

[0146] In Table 1, the pH of an aqueous solution of a polyamine compound having a concentration of 1 mass% shown as "pH of 1 mass% aqueous solution" is the pH when the temperature of the aqueous solution is 25 °C.

[0147]

Table 1

[0148]

Table 2

[0149] As is clear from the above results and FIGS. 1 to 3, in Examples 1 to 3, microcapsules were normally generated in sufficient amounts.

[0150] In Example 1, during the polycondensation reaction of 1,3-bis(aminomethyl)cyclohexane and the PDI-isocyanurate modified product, the color of the reactant became slightly red, but the redness did not become stronger. Also, during the polycondensation reaction, the viscosity of the reactant did not increase, and no change in viscosity was observed. Thus, there were few changes in the properties of the reactant. The pH of the aqueous solution of 1,3-bis(aminomethyl)cyclohexane was 12.

[0151] In Examples 2 to 3, during the polycondensation reaction of 1,3-bis(aminomethyl)cyclohexane and the PDI-isocyanurate modified product, and during the polycondensation reaction of 1,3-bis(aminomethyl)cyclohexane and polymeric MDI, the color of the reactant did not turn red. Also, during the polycondensation reaction, the viscosity of the reactant did not increase, and no change in viscosity was observed. Thus, there were almost no changes in the properties of the reactant.

[0152] In contrast, as is clear from the above results and FIGS. 2 to 4, in Comparative Examples 1 to 3, almost no microcapsules were generated. In Comparative Examples 1 to 3, during the polycondensation reaction of 1,3-diaminopropane, diethylenetriamine, or N,N'-bis(3-aminopropyl)ethylenediamine with the PDI-isocyanurate modified product, the color of the reaction product clearly turned red. Also, during the polycondensation reaction, the viscosity of the reaction product increased. These were presumed to be due to the above polyamine compound reacting with citronellal, which is the main component of lemon eucalyptus oil, and being affected by the product thereof. In Comparative Examples 1 to 3, the pH of the aqueous solution of 1,3-diaminopropane, diethylenetriamine, or N,N'-bis(3-aminopropyl)ethylenediamine exceeded 14.

[0153] In Comparative Example 4, no microcapsules were formed at all. In Comparative Example 4, the color of the reaction product did not change during the reaction, and no change was observed in the viscosity of the reaction product. This was presumed to be because the reactivity of urea was too low and the polycondensation reaction hardly proceeded. In Comparative Example 4, after coating the product in the polycondensation step on high-quality paper, it could not be dried even using an oven. An oily component was observed. This oily component was lemon eucalyptus oil. Therefore, in this comparative example, the presentation of imaging data was omitted. The pH of the aqueous solution of the polyamine compound (urea) was 6 to 8.

[0154] As is clear from the above results and Figure 5, in Comparative Example 5, although not as much as in the case of Comparative Example 4, almost no microcapsules were formed. In Comparative Example 5, the color of the reaction product did not change during the reaction, and no change was observed in the viscosity of the reaction product. This was presumed to be because the reactivity of adipic acid dihydrazide was too low and the polycondensation reaction hardly proceeded. The pH of the aqueous solution of adipic acid dihydrazide was 6 to 8.

[0155] From the comparison between Example 1 and Examples 2 to 3, it was confirmed that by using polymeric MDI in combination as the polyisocyanate compound, the properties of the reactants during the polycondensation reaction were improved as described above. It was presumed that this was because polymeric MDI suppressed some side reactions during the polycondensation reaction. Since polymeric MDI has higher reactivity than other polyisocyanate compounds, it promotes the consumption of 1,3-bis(aminomethyl)cyclohexane by the polycondensation reaction, rapidly forms the wall material component, or increases the formation amount of the wall material component, thereby suppressing minor side reactions involving 1,3-bis(aminomethyl)cyclohexane. As a side reaction in this case, the reaction between 1,3-bis(aminomethyl)cyclohexane and citronellal, which is the main component of lemon eucalyptus oil, was suggested.

[0156] From the aqueous dispersion of the microcapsules obtained in Example 1, a dried product was prepared in the same manner as when evaluating the degree of formation of the above microcapsules, and this dried product (i.e., the microcapsules) was stored statically (heated storage) at 50 °C for 30 days. Subsequently, when observing this dried product after heat storage at a magnification of 1000 times using a scanning electron microscope (manufactured by JEOL Ltd.), a large number of microcapsules with obvious depressions were observed. On the other hand, using the aqueous dispersions of the microcapsules obtained in Examples 2 to 3, a dried product (i.e., the microcapsules) was heat-stored in the same manner as in the case of Example 1, and when observing this dried product after heat storage, only a part of the microcapsules with slightly depressions were observed. That is, from the comparison between Example 1 and Examples 2 to 3, it was confirmed that by using polymeric MDI in combination as the polyisocyanate compound, the storage stability of the microcapsules under heating conditions was improved. This supports the fact that polymeric MDI rapidly forms the wall material component or increases the formation amount of the wall material component as described above, indicating that the heat resistance of the microcapsules is improved by the combined use of polymeric MDI.

Industrial Applicability

[0157] The present invention can be used as microcapsules in which polyurea is a constituent component of the wall material and a component having a formyl group is encapsulated as a core substance. As the core substance, a component having a formyl group and having high volatility like natural essential oil is also suitable.

Claims

【Claim 1】 Microcapsules having a polyurea as a constituent component of the wall material, wherein the polyurea is a reaction product of a polyisocyanate compound and a polyamine compound, the pH of an aqueous solution of the polyamine compound having a concentration of 1% by mass is 9 to 13, a polyisocyanate modified product and polymethylene polyphenyl polyisocyanate are used as the polyisocyanate compound, an organic polyvalent amine compound having both a cycloaliphatic hydrocarbon group and a linear aliphatic hydrocarbon group is used as the polyamine compound, the microcapsules encapsulating a component having a formyl group.

Images