Oil-in-water composition

Abstract

To provide a new oil-in-water composition including a continuous aqueous phase, a dispersed phase, and particles present at the interface between the aqueous phase and the dispersed phase.SOLUTION: A composition contains a continuous aqueous phase, a dispersed phase, and particles present at an interface between the aqueous phase and the dispersed phase, wherein the dispersed phase includes an oil phase in contact with the interface, the particles are composite particles that include a hydrophobic portion having a cationic group on the surface and a hydrophilic polymer covering the surface, and the volume ratio of the composite particles to the entire volume of the composition is more than 0.10 and 0.20 or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to oil-in-water compositions. [Background technology]

[0002] Oil-in-water (O / W) emulsion compositions, which have an aqueous phase as the continuous phase and an oil phase as the dispersed phase, are used in cosmetics and other applications, and provide a refreshing feel when used due to the aqueous component of the outer phase. Oil-in-water emulsion compositions with a high internal phase ratio can contain high concentrations of active ingredients while maintaining this feel when used. In recent years, attention has been focused on Pickering emulsions, which are emulsified by having solid particles present at the interface between the oil phase and the water phase, as oil-in-water emulsion compositions.

[0003] Patent Document 1 discloses particles that have a hydrophobic portion with a cationic group and a specific hydrophilic portion as particles that can be used to form a Pickering emulsion. Patent Document 2 discloses an oil-in-water emulsion composition with a high internal oil phase, in which an association containing a water-soluble cationic polymer and an anionic polymer, called a polyion complex (hereinafter referred to as PIC), is present at the interface between the oil droplets and the water phase. Furthermore, Non-Patent Document 1 discloses a high internal phase oil-in-water emulsion composition prepared by Pickering emulsion using polymer microparticles containing polydimethylsiloxane, polyhydroxystearic acid, polymethyl methacrylate, and the like. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2023 / 243633 [Patent Document 2] International Publication No. 2020 / 137220 [Non-patent literature]

[0005] [Non-Patent Document 1] Current Opinion in Colloid & Interface Science, 2022, 57: 101556. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present disclosure is to provide a novel oil-in-water composition comprising an aqueous phase as a continuous phase, a dispersed phase, and particles present at the interface between the aqueous phase and the dispersed phase. [Means for solving the problem]

[0007] As described above, oil-in-water emulsion compositions with a high internal phase ratio are expected to have a variety of applications, for example, in the field of cosmetics. However, there have been few reports of oil-in-water Pickering emulsions with a high internal phase ratio, and further development is needed to provide safer and more stable products depending on the application. The present inventors conducted extensive research using the particles described in Patent Document 1 and found that it is possible to create an oil-in-water emulsion composition with a high internal phase ratio that exhibits the remarkable properties of a Pickering emulsion. The present invention was completed through further investigation based on the above findings.

[0008] As some of the representative aspects of the present invention, the present disclosure provides the following [1] to

[13] . [1] A composition comprising an aqueous phase as a continuous phase, a dispersed phase, and particles at the interface between the aqueous phase and the dispersed phase, wherein the dispersed phase contains an oil phase in contact with the interface, the particles are composite particles comprising a hydrophobic portion having cationic groups on the surface and a hydrophilic polymer coating the surface, and the volume ratio of the composite particles to the total volume of the composition is greater than 0.10 and not more than 0.20. [2] The composition according to [1], wherein the sum of the volume ratio of the composite particles and the volume ratio of the dispersed phase to the total volume of the composition is 0.74 or more. [3] The composition described in [1] or [2], which is in an emulsified state. [4] The composition according to any one of [1] to [3], wherein the oil ratio, which is the mass ratio of the oil phase to the total mass of the aqueous phase and the oil phase, is 72 mass % or more. [5] The composition according to any one of [1] to [4], which is non-flowable. [6] The composition according to any one of [1] to [4], which is fluid. [7] The composition according to any one of [1] to [6], wherein the composite particles have a Z-average particle size of 100 nm or more. [8] The composition according to any one of [1] to [7], wherein the hydrophobic portion having the cationic group on the surface thereof comprises a hydrophobic polymer obtained by polymerizing a hydrophobic monomer in the presence of a cationic radical polymerization initiator, and the cationic group is a residue of the cationic radical polymerization initiator. [9] The composition according to [8], wherein the hydrophobic monomer is a (meth)acrylic acid-based monomer.

[10] The composition according to any one of [1] to [9], wherein the hydrophilic polymer is polyvinyl alcohol.

[11] A method for producing a composition comprising a step of mixing and stirring composite particles comprising a hydrophobic portion having a cationic group on the surface and a hydrophilic polymer coating the surface, water, and an oil, wherein the mass of the oil is 20 to 60 times the mass of the composite particles, and the composition comprises an aqueous phase as a continuous phase, a dispersed phase, and the composite particles at the interface between the aqueous phase and the dispersed phase.

[12] The method according to

[11] , wherein the mass of the oil or fat is 24 to 55 times the mass of the composite particles.

[13] The method according to

[11] or

[12] , wherein the mass of the water is 21% by mass to 30% by mass relative to the mass of the fat or oil. [Effects of the Invention]

[0009] The present disclosure provides a novel oil-in-water composition comprising an aqueous phase as a continuous phase, a dispersed phase, and particles present at the interface between the aqueous phase and the dispersed phase. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a diagram showing a schematic diagram of the interface between the continuous phase (aqueous phase) and the dispersed phase (oil droplets) in an example of a composition of the present disclosure, and particles at the interface. In the diagram, "1" indicates a composite particle. [Figure 2] FIG. 1 is a diagram in which the shaded portion of a triangular graph ABC represents the preparation conditions for a non-flowable composition among the compositions of the present disclosure. [Figure 3] 1 shows a microscope image of an example of a composition of the present disclosure, observed fluorescently using a 63x oil immersion objective lens. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments shown below are described for illustrative purposes only, and the following description of the present embodiments should not be construed as limiting the scope of the claims. In the following description, the amount of a substance, such as the content, is expressed by mass unless otherwise specified. Furthermore, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0012] The composition of the present disclosure is a composition containing a continuous aqueous phase, a dispersed phase, and particles at the interface between the aqueous phase and the dispersed phase. Figure 1 shows a schematic diagram of the interface between the continuous phase (aqueous phase) and the dispersed phase (oil droplets) and the composite particles at the interface in one embodiment of the composition of the present disclosure.

[0013] <Composite particles> In the composition of the present disclosure, the particles present at the interface between the continuous phase and the dispersed phase are composite particles containing a hydrophobic portion having a cationic group on its surface and a hydrophilic polymer coating the surface. The shape of the composite particles is not particularly limited as long as they have the function of stabilizing the dispersed phase in the continuous phase in the composition of the present disclosure, but a substantially spherical shape is preferred.

[0014] The composite particles have organic groups exposed at least on the surface. The core portion of the composite particles may be composed solely of organic materials, but is not limited to those composed solely of organic groups and may also contain inorganic materials. When the core portion of the composite particles contains an inorganic material, a polymer containing a hydrophobic monomer unit may be bonded or associated with the surface of the inorganic material in the core portion.

[0015] For details of the components and manufacturing methods of the composite particles, please refer to the disclosure of WO 2023 / 243633, the contents of which are incorporated herein by reference.

[0016] [Hydrophobic part having cationic groups on the surface] The hydrophobic portion having a cationic group on its surface is not particularly limited as long as it has a hydrophobic portion with low affinity for water and a cationic group. The cationic group is present on the surface of the hydrophobic portion, but a portion may be present internally as long as it does not affect the properties of the composite particle. Examples of hydrophobic portions having a cationic group on their surface include particles formed from a cationic polymer having a hydrophobic monomer unit and a cationic group, particles formed from a hydrophobic polymer and a cationic polymer containing a hydrophobic monomer unit, particles formed from a hydrophobic polymer whose surface is modified with a compound having a cationic group, or mixtures thereof. In this specification, the "cationic polymer having a hydrophobic monomer unit and a cationic group" that forms the hydrophobic portion and the "hydrophobic polymer used together with a cationic polymer or a compound having a cationic group" are collectively referred to as "hydrophobic polymer." Preferably, the hydrophobic portion having a cationic group on its surface is a spherical particle.

[0017] Each hydrophobic polymer is a polymer obtained by polymerizing a hydrophobic monomer as a main constituent monomer, and contains hydrophobic monomer units. Each hydrophobic polymer may be either a homopolymer or a copolymer.

[0018] Examples of the hydrophobic monomer unit include a monomer unit obtained from a monomer having an ethylenically unsaturated double bond. Here, examples of the monomer having an ethylenically unsaturated double bond include a polymerizable monomer having a carbon-carbon double bond in the molecule, more specifically, a (meth)acrylic acid-based monomer unit, a styrene-based monomer unit, etc.

[0019] Examples of the (meth)acrylic acid-based monomer unit include a monomer unit derived from alkyl (meth)acrylate having an alkyl ester group having from 1 to 6 carbon atoms. Examples of the alkyl ester group having from 1 to 6 carbon atoms include a methyl ester group, an ethyl ester group, an n-propyl ester group, an n-butyl ester group, an n-pentyl ester group, and an n-hexyl ester group. These alkyl ester groups may have one or more hydrogen atoms of the alkyl group constituting the alkyl ester group substituted with a hydroxyl group, as necessary. From the viewpoint of ensuring sufficient storage stability of the particles, the alkyl ester group preferably has from 1 to 4 carbon atoms.

[0020] As such alkyl (meth)acrylate, methyl methacrylate (MMA), butyl methacrylate (BMA), and 2-hydroxyethyl methacrylate (HEMA) are preferred, with methyl methacrylate being more preferred. When these monomers are used, the storage stability of the resulting particles is improved, and the structure of the dispersed phase in the composition can be further stabilized.

[0021] When the (meth)acrylic acid-based monomer unit has an acidic group such as a carboxyl group, the carboxyl group may be in the form of a salt, for example, a sodium salt or a potassium salt. Examples of the styrene-based monomer unit include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylstyrene, isobutylstyrene, t-butylstyrene, o-bromostyrene, m-bromostyrene, p-bromostyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene.

[0022] In each hydrophobic polymer, the hydrophobic monomer unit may be one type or two or more types. For example, the hydrophobic polymer may contain only styrene-based monomer units, only (meth)acrylic acid-based monomer units, or both styrene-based monomer units and (meth)acrylic acid-based monomer units. The hydrophobic polymer preferably contains only styrene-based monomer units or only (meth)acrylic acid-based monomer units as the hydrophobic monomer units, and more preferably contains only (meth)acrylic acid-based monomer units.

[0023] Examples of the cationic group include a residue of a cationic radical polymerization initiator described below, and a cationic group derived from any compound or polymerization unit capable of introducing any cationic group into the end or the hydrophobic moiety. Among these, a cationic group that is a residue of a cationic radical polymerization initiator is preferred. For example, a hydrophobic polymer can be produced by polymerizing a hydrophobic monomer in the presence of a cationic radical polymerization initiator, and by carrying out this process according to a predetermined procedure such as the procedure described below, a particulate hydrophobic moiety having a residue of a cationic radical polymerization initiator on its surface can be produced.

[0024] By disposing cationic groups on or near the surface of the hydrophobic portion of the composite particle, the dispersed phase in the continuous phase can be stabilized in the composition of the present disclosure. Examples of the cationic group include a quaternary ammonium group, an imidazolium group, a pyridinium group, a piperidinium group, a pyrrolidinium group, a phosphonium group, and the like, all of which may have a substituent. Examples of the substituent that the cationic group may have include an alkyl group having from 1 to 6 carbon atoms, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, or an n-hexyl group, and more preferably a methyl group. Examples of the cationic group that is a residue of a cationic radical polymerization initiator include the following cationic groups that are residues of any of the cationic radical polymerization initiators described below.

[0025] [ka] In the above formula, * indicates the bonding position.

[0026] Examples of the cationic group include the 1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium group (residue of ADIP and ADIP-Cl described below), the 4,5-dihydro-1H-imidazol-3-ium group (residue of VA-044 described below), and the amidinium group (residue of V-50 described below), with the 1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium group being particularly preferred.When a cationic group that is a residue of a cationic radical polymerization initiator is introduced, the composite particles may be produced using a cationic radical polymerization initiator having the corresponding residue.

[0027] [Hydrophilic polymer that coats the surface of the hydrophobic part] The hydrophilic polymer used in the composition of the present disclosure is preferably a nonionic polymer. In the composite particles, the hydrophilic polymer that coats the surface of the hydrophobic portion interacts with the hydrophobic portion through intermolecular forces such as hydrophobic effect or hydrogen bonding, or is covalently bonded. Examples of such hydrophilic polymers include polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, etc., and polyvinyl alcohol is preferred. Here, when referring to coating the surface, it is sufficient to coat at least a portion of the surface, but it is preferable to coat the surface sufficiently to achieve the function of the composite particles described in the composition of the present disclosure. By including a hydrophilic polymer on the surface of the composite particles, it is possible to maintain the dispersed phase in the composition of the present disclosure stable, and the composite particles are particularly stable to salts, and aggregation in the presence of salts is suppressed.

[0028] The hydrophilic polymer may be covalently bonded to a hydrophobic polymer that constitutes the hydrophobic portion having a cationic group. The average degree of polymerization of polyvinyl alcohol may be about 100 to 2,000, more preferably 300 to 1,500, and even more preferably 400 to 1,000. The polyvinyl alcohol may have at least a portion of the hydroxyl groups in its structure acetylated. For example, polyvinyl alcohol produced by saponifying polyvinyl acetate can be used. From the viewpoint of improving the storage stability of the composite particles themselves and their stability in the composition of the present disclosure, the upper limit of the saponification degree can be 99%, 98%, or 96%, and the lower limit can be 70%, 75%, or 78%. Furthermore, the saponification degree is preferably 70% or more and 99% or less, more preferably 75% or more and 98% or less, and even more preferably 78% or more and 96% or less. Since the degree of hydrophilicity of the composite particle surface can be adjusted by adjusting the saponification degree, it is preferable to adjust the saponification degree appropriately depending on the intended use of the composition of the present disclosure.

[0029] The hydrophilic polymer may be a commercially available hydrophilic polymer or may be produced from a hydrophobic monomer. For example, polyvinyl alcohol may be a commercially available polyvinyl alcohol, or may be produced by polymerizing vinyl acetate by a radical polymerization reaction and saponifying the acetate ester group.

[0030] [Crosslinking monomer] A crosslinkable monomer unit may be used as the organic monomer unit constituting the core portion of the composite particle. In such an embodiment, a crosslinkable monomer may be partially used as one of the monomers used to prepare the composite particle. Specific examples of such crosslinkable monomers include monomers containing two or more ethylenically unsaturated double bonds in the molecule, which are commonly used as crosslinking agents. However, in this embodiment, such crosslinkable monomers do not need to be used. If used, in order to ensure sufficient storage stability of the particles, the upper limit of the content of the hydrophobic monomer and the monomer constituting the hydrophilic polymer can be set to 20%, 10%, or 5%, and the lower limit to 0.1% or 3%, respectively, in molar terms. The content can be set to a range of 0.1% to 20%, preferably 3% to 10%, and more preferably 5% or less. Specific examples of such crosslinkable monomers include N,N'-methylenebisacrylamide, N,N'-ethylenebisacrylamide, N,N'-methylenebismethacrylamide, N,N'-ethylenebismethacrylamide, ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, and divinylbenzene. The monomer units of the hydrophobic polymer that constitutes the hydrophobic portion and the hydrophilic polymer that coats the surface of the hydrophobic portion can be identified using commonly known methods, such as analysis of the fingerprint region of an IR spectrum.

[0031] [Combination of a hydrophobic moiety having a cationic group and a hydrophilic polymer] In the composite particles, from the viewpoint of making the composition of the present disclosure more stable, it is preferable that a part or all of the surface of the hydrophobic portion having a cationic group of the composite particle is directly or indirectly coated with a hydrophilic polymer. More specifically, the hydrophobic monomer unit of the hydrophobic polymer and the hydrophilic monomer unit of the hydrophilic polymer may be bonded by a covalent bond (a "directly coated" embodiment), or the hydrophobic monomer unit and the hydrophilic monomer unit may be bonded by an intermolecular force (a "indirectly coated" embodiment).

[0032] Furthermore, when the hydrophobic monomer unit and the hydrophilic monomer unit are covalently bonded, the polymer in which they are covalently bonded may be a block copolymer or a graft copolymer. However, since the storage stability of the particles is particularly improved when the polymer is a graft copolymer, it is more preferable that the polymer in which the hydrophobic monomer unit and the hydrophilic monomer unit are covalently bonded is a graft copolymer.

[0033] Furthermore, when the hydrophobic monomer unit and the hydrophilic monomer unit are bonded by intermolecular forces, the bond by intermolecular forces is preferably induced by heat treatment, from the viewpoint of improving the storage stability of the composite particles. In this case, the heat treatment can be, for example, at a temperature of 20°C to 100°C, more specifically, at a temperature of 30°C to 80°C, for 30 minutes to 480 minutes.

[0034] In addition, the composite particles are not limited to particles in which the hydrophobic monomer units and the hydrophilic monomer units are bonded only by covalent bonds or particles in which the hydrophobic monomer units are bonded only by intermolecular forces, but may also be particles in which some of the hydrophobic monomer units are bonded to the hydrophilic monomer units by covalent bonds, and the remaining hydrophobic monomer units are bonded to the hydrophilic monomer units by intermolecular forces. From the viewpoint of stabilizing the composition of the present disclosure, the abundance ratio of the hydrophobic monomer units bonded to the hydrophilic monomer units by covalent bonds can be an upper limit of 90%, 70%, or 60%, and a lower limit of 10%, 30%, or 40%, with respect to the total hydrophobic monomer units bonded to the hydrophilic monomer units. Preferably, it is 10% or more and 90% or less, more preferably 30% or more and 70% or less, and even more preferably 40% or more and 60% or less.

[0035] In the above-described embodiment, from the viewpoint of improving the storage stability of the particles and the emulsifying ability of the particles, the abundance ratio of the hydrophobic polymer portion and the hydrophilic polymer portion can be such that the mass corresponding to the hydrophilic polymer portion relative to 100 parts by mass of the hydrophobic polymer portion is 6 parts by mass or 4 parts by mass at the upper limit and 1 part by mass or 3 parts by mass at the lower limit, preferably 1 part by mass or more and 6 parts by mass or less, and more preferably 3 parts by mass or more and 4 parts by mass or less.

[0036] The molecular weight of a composite polymer having a structure in which a hydrophilic polymer is covalently bonded to a hydrophobic polymer, or the sum of the molecular weights of the hydrophilic and hydrophobic polymers when both are non-covalently bonded, is not particularly limited. For example, the particle can be dissolved in an organic solvent such as chloroform and calculated as a polystyrene-equivalent number average molecular weight in gel permeation chromatography. In this case, if the hydrophobic portion in the form of a polymer and the hydrophilic portion in the form of a polymer are non-covalently bonded, an operation to separate the hydrophilic polymer and the hydrophobic polymer may be performed as necessary. In order to improve the storage stability of the composite particles, the upper limit of the number average molecular weight or the sum of the number average molecular weights of the composite polymers can be 500,000, 30,000, 20,000, or 10,000, and the lower limit can be 1,000, 10,000, or 50,000. From the viewpoint of improving the storage stability of the particles, the number average molecular weight or the total value of the number average molecular weights of the composite polymer is preferably 1,000 to 500,000, 1,000 to 100,000, 5,000 to 20,000, 10,000 to 500,000, 50,000 to 30,000, or 50,000 to 30,000. Furthermore, the molecular weight distribution, which is the ratio of the number average molecular weight to the weight average molecular weight, is preferably in the range of 1.05 to 5, more preferably 1.05 to 1.7. Furthermore, in this embodiment, the relative ratio of the molecular weight of only the hydrophobic polymer portion to the molecular weight of only the hydrophilic polymer portion per composite particle is preferably 1 to 6 hydrophilic polymer portions per 100 hydrophobic polymer portions. By maintaining the relative ratio within the above range, the emulsifying ability of the composite particles can be improved, and the storage stability of the composition of the present disclosure can be improved.

[0037] From the viewpoint of improving the storage stability of the emulsion composition, the upper limit of the glass transition temperature of the composite polymer can be set to 200°C, 150°C, or 100°C, and the lower limit can be set to 30°C, 40°C, or 45°C.

[0038] The glass transition temperature of the polymer can be measured by differential scanning calorimetry (DSC). A specific DSC measurement method conforms to the method described in JIS K 7121 (1987).

[0039] The glass transition temperatures of polymers can be, for example, 100°C for polystyrene, 105°C for polymethyl methacrylate, 83°C for polyisopropyl methacrylate, 107°C for polycyclohexyl methacrylate, 110°C for polyphenyl methacrylate, 101°C for polyacrylic acid, 121°C for poly-N,N-dimethylacrylamide, 100°C for polydimethyl itaconate, and 100°C for polydimethyl fumarate.

[0040] [Method of manufacturing composite particles] When a hydrophobic polymer is used, for example, the composite particles can be produced by the following procedure.

[0041] The method for producing composite particles is not particularly limited, and examples thereof include polymerizing the hydrophobic monomer and the hydrophilic monomer separately or sequentially (i.e., polymerizing the hydrophilic monomer separately from the hydrophobic monomer; or polymerizing the hydrophilic monomer after the completion of the polymerization of the hydrophobic monomer) and forming particles. Alternatively, after the completion of the polymerization of the hydrophobic monomer, a hydrophilic polymer can be added to the resulting product and reacted to form particles. The method for producing composite particles is not particularly limited, and may include, for example, the following particle formation step and a modification step or other steps.

[0042] (1) Particulate process The particulate forming step is not particularly limited, and examples thereof include emulsion polymerization, suspension polymerization, dispersion polymerization, and the like, which are steps of forming particles while polymerizing a monomer component such as a hydrophobic monomer. Note that during this polymerization, it is preferable that the polymerization reaction is carried out in the presence of an emulsifier. The particulate forming step may also be a step of polymerizing a monomer component by solution polymerization or the like, and then particulating the resulting reaction product by phase inversion emulsification, suspension, or the like.

[0043] However, from the viewpoint of reducing the complexity of the production, a step of polymerizing the monomer components while forming particles is preferred, with emulsion polymerization, suspension polymerization, or dispersion polymerization being more preferred, and emulsion polymerization being even more preferred. Furthermore, among the emulsion polymerization methods, soap-free emulsion polymerization is preferred because it prevents impurities such as emulsifiers from being mixed into the surface of the hydrophobic portion that will become the core, and is less likely to affect the subsequent modification step described below. The specific method for implementing this soap-free emulsion polymerization is not particularly limited, and can be carried out by a known method. For example, it can be carried out by emulsion polymerizing the monomer components in the presence of a polymerization initiator without using an emulsifier such as a surfactant, a polymeric emulsifier, or a reactive surfactant.

[0044] In the particulate formation process, the polymerization initiator used is preferably a cationic radical polymerization initiator. The cationic radical polymerization initiator can be one that is both safe after polymerization and has the reactivity required for a radical polymerization initiator. Examples of the cationic radical polymerization initiator include 2,2'-[diazene-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium) ditrifluoromethanesulfonate (ADIP), 2,2'-[diazene-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1H-imidazol-3-ium) dichloride (ADIP-Cl), 2,2'-azobis(2-methyl-4,5-dihydro-1H-imidazol-3-ium) dichloride (ADIP-Cl), and 2,2'-azobis(2-methyl-4,5-dihydro-1H-imidazol-3-ium) dichloride (ADIP-Cl). Examples of suitable initiators include 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (V-50, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (VA-061, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.). Reference can also be made to the description in paragraphs 0050 to 0060 of JP 2017-051113 A. In the particle formation process, it is preferable to use one or more polymerization initiators selected from the group consisting of the exemplified polymerization initiators. ADIP or ADIP-Cl is more preferred as a cationic radical polymerization initiator because it allows composite particles to be prepared under milder reaction conditions and can prevent a decrease in particle storage stability due to damage such as heating during particle preparation.

[0045] The amount of the cationic radical polymerization initiator used may be 0.01 mol% or more relative to the total molar amount of the monomers used, and may be selected appropriately within the range of concentration at which radical synthesis proceeds. For example, the polymerization initiator may be used in an amount of 0.1 mol% or more, preferably 1 mol% or more, and 10 mol% or less, preferably 5 mol% or less.

[0046] The solvent used in the granulation step is not particularly limited, and examples thereof include an aqueous medium. The aqueous medium used in the granulation step may contain an alcohol in addition to water in order to improve the storage stability of the particles. Examples of the alcohol include methanol or ethanol. The reaction temperature during the granulation step is preferably set to a temperature below the boiling point of the solvent. The particle size of the composite particles can be adjusted by changing the solvent used in the granulation step. As shown in the examples, the present inventors have found that a larger particle size can be obtained in an example where a solvent prepared by adding a certain amount of methanol to water is used as the solvent, compared to an example where water is used as the solvent.

[0047] (2) Modification process In the modification step, for example, a part or all of the surface of the hydrophobic portion is directly or indirectly coated with a hydrophilic monomer or the hydrophilic polymer, or the modification step can also be expressed as a step of bonding or associating a polymerized hydrophobic monomer with the hydrophilic polymer.

[0048] Examples of embodiments in which the surface of the hydrophobic portion is directly coated with the hydrophilic polymer include a method in which the hydrophobic monomer unit present on the surface of the hydrophobic portion is covalently bonded to the hydrophilic monomer unit. More specifically, there are embodiments in which an atomic group derived from the hydrophilic polymer is covalently bonded to an atomic group derived from the hydrophobic monomer unit present on the surface of the core portion, and an embodiment in which, for example, vinyl acetate is covalently bonded to an atomic group derived from the hydrophobic monomer unit present on the surface of the core portion, and then vinyl acetate is further polymerized thereto, followed by ester hydrolysis of the polyvinyl acetate moiety to saponify the resulting hydrophilic polymer. However, from the viewpoint of improving emulsification ability, the embodiment in which the surface of the hydrophobic portion is directly coated with the hydrophilic monomer or the like is preferably a method in which the hydrophilic polymer is covalently bonded to an atomic group derived from the hydrophobic monomer unit present on the surface of the core portion. It is more preferable that the hydrophilic polymer is polyvinyl alcohol, and it is even more preferable that the covalent bond is a carbon-carbon covalent bond formed by a radical reaction using a radical polymerization initiator.

[0049] An example of an embodiment in which the surface of the hydrophobic portion is indirectly coated with the hydrophilic monomer or the like is an embodiment in which an atomic group contained in a hydrophobic monomer unit present on the surface of the core portion (hydrophobic portion) and an atomic group contained in the hydrophilic polymer are caused to interact with each other through intermolecular forces, electrostatic interactions, or the like. In this case, since the hydrophobic portion and the hydrophilic polymer ultimately interact with each other, any functional group or atomic group may be introduced into the hydrophobic portion and / or the hydrophilic polymer to facilitate the interaction between them. A preferred method for causing an atomic group contained in a hydrophobic monomer unit present on the surface of the hydrophobic portion and an atomic group contained in the hydrophilic polymer to interact with each other through intermolecular forces, electrostatic interactions, or the like is to add the hydrophilic polymer to the particles obtained in (1) the particulate formation step, introduce any functional group or atomic group as necessary, and appropriately set the temperature, pressure, concentration, and other conditions of the mixture. It is more preferred to heat, pressurize, or concentrate the mixture.

[0050] (3) Other processes The dispersion (composition in which composite particles are dispersed in a solvent) obtained after the above-mentioned (1) particulation step, or the (1) particulation step and (2) modification step, may be used as is in the production of the composition of the present disclosure, or may be used after other steps have been added. Examples of "other steps" include, but are not limited to, a washing step, a concentration step, and a drying step. For example, the washing step, the concentration step, and the drying step may be incorporated into at least one of the (1) particulation step and the (2) modification step, or may be independent (temporally or spatially) from the (1) particulation step and the (2) modification step.

[0051] The composite particles may be washed to reduce the irritation of the composition produced using the composite particles. The medium used in the washing step is not particularly limited, and an aqueous medium can be used. For example, when the reaction solvent used in the particulation step is an aqueous medium, the washing step can be performed by repeatedly sedimenting the composite particles by centrifugation, removing the supernatant, and then adding the aqueous medium to redisperse the particles. Furthermore, when the reaction solvent used in the particulation step is an organic solvent, the washing step can be performed by mixing an aqueous medium containing salt, such as brine, with the reaction solvent, stirring, and separating the aqueous and organic phases using a separatory funnel or the like. Alternatively, the composite particles may be purified by a treatment using a dialysis membrane. By including a washing step in the method for producing composite particles, the amount of unreacted radical polymerization initiator, its decomposition products, and unreacted monomer remaining in the medium can be reduced (e.g., each concentration can be reduced to less than 100 ppm).

[0052] In order to fully utilize the emulsifying ability of the composite particles, a concentration step for increasing the particle concentration in the dispersion may be included. Although not particularly limited, this concentration step may be carried out by sedimenting the composite particles by centrifugation, removing the supernatant, and then redispersing the particles by adding a medium in an amount smaller than the mass and / or volume of the removed supernatant, or by drying the composite particles to form a powder, and then redispersing the particles by adding a medium in an amount smaller than the mass and / or volume of the medium removed by drying.

[0053] Furthermore, the composite particles may be dried to obtain a powder. The drying step can be carried out by evaporating the medium containing the composite particles to dry them. Specific methods used in the drying step are not particularly limited, and include hot air drying, infrared drying, fluidized bed drying, spray drying, freeze drying, reduced pressure drying, and vacuum drying.

[0054] The method for producing composite particles may have only one step of a particulate formation step, but may also be a multi-step production method including other steps in addition to the particulate formation step.

[0055] When the method for producing composite particles has only one step, the particulation step, it is preferable to modify the hydrophobic portion during the particulation step as appropriate to make the surface of the core portion of the composite particle hydrophobic, and to coat part or all of the surface of the core portion directly or indirectly with a hydrophilic monomer or the like.

[0056] When the method for producing composite particles is a multi-step method including a particulation step, it is preferable to use a two-step method including (1) a particulation step and (2) a modification step, from the viewpoint of improving storage stability and ensuring sufficient emulsification ability of the particles. Furthermore, when the method for producing composite particles is a multi-step method including a particulation step, it may be a three-step or more method including one or more other steps, and the order of the steps does not matter, and each step may be performed multiple times. When the method for producing composite particles is a two-step or more method including (1) a particulation step and (2) a modification step, it is preferable to form a hydrophobic portion (core portion) in the (1) particulation step, and then directly or indirectly coat part or all of the surface of the hydrophobic portion (core portion) with a hydrophilic monomer or the like in the (2) modification step. A more specific method for producing the composite particles will be disclosed in detail in the following Examples.

[0057] [Other properties of composite particles] The average zeta potential of the composite particles is calculated by electrophoresing a composition mainly containing the particles, measuring the particle migration speed using laser Doppler velocimetry (e.g., Zetasizer Nano ZSP, manufactured by Malvern Panalytical), and applying Henry's equation shown below to the particle migration speed.

number

[0058] For more details, please refer to the method for measuring the average zeta potential described in the Examples. The average zeta potential of the composite particles can be set to an upper limit of +60 mV or +40 mV and a lower limit of +10 mV or +30 mV, preferably +10 mV or more and +60 mV or less, and more preferably +30 mV or more and +40 mV or less. Although the present invention is not bound by any theory, it is presumed that when the average zeta potential of the composite particles is within the above range, particle repulsion between the particles suppresses particle aggregation, thereby improving the storage stability of the particles. Furthermore, it is presumed that when the average zeta potential of the composite particles is within the above range, they are more likely to be adsorbed to the interface between the aqueous phase and the oil phase in the composition, thereby improving the storage stability of the composition of the present disclosure.

[0059] The Z-average particle size (also called the cumulant mean diameter) of the composite particles is calculated from the temporal fluctuation of the scattered light intensity measured by dynamic light scattering (DLS) from particles undergoing Brownian motion in a dispersion containing the particles. From the viewpoints of improving the storage stability of the particles, improving the emulsifying ability of the particles, and improving the storage stability of the emulsion composition, the Z-average particle size of the composite particles can have an upper limit of 1000 nm or 900 nm and a lower limit of 100 nm or 150 nm, preferably 100 nm to 800 nm, and more preferably 150 nm to 700 nm.

[0060] The polydispersity index (PdI) of the composite particles used in the composition of the present disclosure, as measured by dynamic light scattering, is preferably 0.2 or less, and more preferably 0.1 or less. PdI can be measured, for example, using a Zetasizer Nano ZSP (Malvern Instruments). PdI, together with the average particle size, is used as an index for evaluating the width of the particle size distribution of the composite particles in the composition.

[0061] In the high-internal oil-in-water emulsion described in Patent Document 2, an association complex containing a water-soluble cationic polymer and anionic polymer, known as a polyion complex (PIC), exists between the aqueous and oil phases. During the PIC preparation process, the particle size distribution of the PIC produced changes depending on the concentration and pH of the cationic and anionic polymers, exhibiting bimodal or broadening, resulting in different sizes and dispersities depending on the conditions. In particular, polydisperse PICs may reduce the emulsion stability of emulsion compositions prepared with PICs, or the PICs themselves may aggregate, resulting in reduced stability. Furthermore, according to Langmuir 2019, 35, 6693-6707, the maximum PIC concentration required for preparation is 2 g / L. Lower PIC concentrations require the incorporation of excess PIC dispersant during composition preparation, potentially limiting composition formulation. These PIC preparation methods and the challenges associated with emulsion compositions using PICs have been reported in the above-mentioned literature. On the other hand, the composite particles used in the composition of the present disclosure are polymer fine particles produced by polymerization, and the particle size can be easily adjusted during production, and they can be produced at a high concentration while maintaining monodispersity.

[0062] Furthermore, the interfacial tension (T 0.01 ), and the difference in interfacial tension (T1) between the aqueous dispersion containing 1% by mass of composite particles and decamethylcyclopentasiloxane (T 0.01 From the viewpoints of enhancing the emulsifying ability of the particles and ensuring sufficient storage stability of the emulsion composition, -T1) is preferably 10 mN / m or more, and more preferably 15 mN / m or more. Furthermore, from the viewpoint of ensuring good storage stability of the composition of the present disclosure, the interfacial tension value (T1) between an aqueous dispersion containing 1% by mass of composite particles and decamethylcyclopentasiloxane is preferably 25 mN / m or less, more preferably 20 mN / m or less, and even more preferably 10 mN / m or more and 18 mN / m or less.

[0063] In this embodiment, the interfacial tension can be measured by the pendant drop method. A contact angle meter (trade name: DMo-502, manufactured by Kyowa Interface Science Co., Ltd.) can be used for the measurement. The surrounding phase is decamethylcyclopentasiloxane (cyclopentasiloxane, commonly known as "DMCPS"), with a specific gravity of 0.96 g / cm. 3 ) can be used, and purified water, ion-exchanged water, pure water, etc. can be used as the water used in the aqueous dispersion. In this case, measurement conditions of room temperature (e.g., 25°C) and humidity of 45%±10% can be used.

[0064] <Continuous phase: aqueous phase> The composition of the present disclosure includes an aqueous phase, which is a continuous phase. The aqueous phase is a dispersion medium for the dispersed phase. The aqueous phase may be composed of water commonly used in cosmetics, quasi-drugs, etc. The water is not particularly limited, but examples include tap water, purified water, ion-exchanged water, elixir water, hot spring water, deep sea water, and steam-distilled water from plants. One or more types may be appropriately selected and used as needed. The aqueous phase may contain hydrophilic components such as lower alcohols, polyhydric alcohols, and various salts, as long as they do not impair the effects of the present disclosure.

[0065] <Dispersed phase> The dispersed phase includes an oil phase in contact with the interface with the aqueous phase. Since specific particles, which will be described later, exist at the interface, the dispersed phase also includes an oil phase in contact with the particles. The dispersed phase may consist of only an oil phase or may consist of multiple phases (multilayer structure). For example, it may contain an aqueous phase inside an oil phase (a so-called W / O phase). For the composition of the aqueous phase in this case, please refer to the explanation of the aqueous phase as the continuous phase above.

[0066] The dispersed phase may be dispersed as oil droplets in the dispersion medium. The oil droplets may contain an aqueous phase inside. The particle size of the oil droplets is not particularly limited, but is preferably 10 μm to 200 μm, and more preferably 30 μm to 100 μm. The particle size of the oil droplets is a value read using a scale as an index when observing the composition under a microscope. Note that if the volume of the dispersed phase exceeds 74% of the volume of the composition, the oil droplets may not be able to assume a spherical shape. In this case, the composition may be diluted with water before measurement. The maximum particle size of the oil droplets is not particularly limited, but is preferably 50 μm to 500 μm, and more preferably 100 μm to 300 μm. The present inventors have found that a composition containing oil droplets with a particle size of 10 μm or more can be provided by preparing a composition under specified conditions using hydrophobic particles, as described below.

[0067] The oil phase is a phase composed of oils and fats. The oils and fats may be oils that are liquid at room temperature or fats that are solid at room temperature. Examples of oils and fats include liquid oils and fats, solid oils and fats, waxes, hydrocarbon oils, ester oils, and silicone oils. Examples of liquid oils include olive oil, camellia oil, macadamia nut oil, and castor oil. Examples of solid fats and oils include palm oil and hardened oil. Examples of waxes include carnauba wax, candelilla wax, jojoba oil, beeswax, and lanolin. Examples of hydrocarbon oils include liquid paraffin, paraffin, volatile isoparaffin, petrolatum, ceresin, microcrystalline wax, and squalane. Examples of ester oils include isopropyl myristate, 2-octyldodecyl myristate, cetyl 2-ethylhexanoate, and diisostearyl malate. Examples of silicone oils include volatile and non-volatile linear dimethylpolysiloxanes such as dimethylpolysiloxane (1cs), dimethylpolysiloxane (1.5cs), dimethylpolysiloxane (2cs), and dimethylpolysiloxane (6cs); branched siloxanes such as methyltrimethicone, tris(trimethylsilyl)methylsilane, and tetrakis(trimethylsilyl)silane; cyclic dimethylsiloxanes such as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane; crosslinked methylpolysiloxanes, network methylpolysiloxanes, methylphenylpolysiloxanes such as methyltrimethicone and diphenylsiloxyphenyltrimethicone; and higher alcohol-modified organopolysiloxanes. When the composition of the present disclosure is used in cosmetic applications, cyclic dimethylsiloxanes are preferred as the silicone oil, from the viewpoint of improving the application feel of the composition to a refreshing feel. The fat or oil forming the oil phase is preferably an oil that is liquid at 25°C.

[0068] The oil phase may contain additives in addition to the oil. The additives may be dissolved in the oil, for example. Examples of the additives include additives known in cosmetics or quasi-drugs, such as moisturizers, ultraviolet absorbers, ultraviolet scattering agents, antioxidants, antioxidant assistants, pigments, various extracts, blood circulation promoters, local stimulants, hair follicle activators, antiandrogenic agents, antiseborrheic agents, keratolytic agents, disinfectants, anti-inflammatory agents, whitening agents, antiwrinkle agents, astringents, antioxidants, active oxygen removers, skin nutrients, vitamins, hair growth agents such as herbal extracts, and fragrances.

[0069] <Composition> The composition of the present disclosure comprises a continuous aqueous phase, a dispersed phase, and composite particles at the interface between the aqueous phase and the dispersed phase. A composition in which the oil phase in the dispersed phase is liquid can be called an emulsified composition. "Emulsion," also known as "emulsion," refers to a state in which a liquid dispersoid is dispersed in a liquid dispersion medium, or to the state of being brought into such a state. The composition of this embodiment is a Pickering emulsion, which is emulsified by the presence of particles, rather than a surfactant, at the interface between the aqueous and oil phases. Surfactants are generally considered to be in an equilibrium state in which they do not remain at the oil-water interface but instead adsorb to the aqueous phase or adjacent oil droplets. In this state, a film of surfactant molecules formed on the oil droplet surface may reversibly form, exposing the oil droplet surface. In this case, adjacent oil droplets tend to coalesce, resulting in reduced emulsion stability. The composition of the present disclosure exhibits excellent emulsion stability due to the use of composite particles, even without a surfactant as an emulsifier, or even when only a small amount is used. Emulsion compositions include gels, sols, and the like. A sol refers to a state in which fine particles are dispersed in a dispersion medium, and the dispersion medium is liquid (colloidal solution). A gel refers to a sol that has lost its fluidity. The composition of the present disclosure is preferably a gel.

[0070] The composition of the present disclosure is an oil-in-water composition. In this specification, the term "oil-in-water" may refer to an O / W type, a W / O / W type in which the oil phase (O) of an oil-in-water (O / W) emulsion composition is water-in-oil (W / O) type, an O / W / O type, a W / O / W / O type, or the like.

[0071] In the present disclosure, the oil ratio Φ is the ratio of the mass of the oil phase to the total mass of the oil phase and the aqueous phase. The larger the Φ, the larger the proportion of the oil phase in the composition, and therefore the more active ingredients that can be dissolved or dispersed in the oil phase can be contained in the composition.

[0072] In the present disclosure, an emulsion composition having an oil ratio of 50% by mass or more is sometimes referred to as a "high internal oil phase oil-in-water emulsion composition." A large amount of surfactant is often used to prepare a high internal oil phase oil-in-water emulsion, but this can cause problems such as stickiness and irritation when applied directly to the human body, such as the skin. Furthermore, many consumers are concerned about the effects of directly ingesting a surfactant that can be absorbed by the human body. For this reason, it is desirable to minimize the amount of surfactant used in an emulsion composition. The composition of the present disclosure can provide a high internal oil phase oil-in-water emulsion without substantially using a surfactant.

[0073] The oil ratio ΦD can be calculated from the blending amounts during the production of the composition, but for example, for the composition that is the final product, it can be calculated by subjecting it to an operation that promotes phase separation, causing phase separation, and measuring the masses of the water-insoluble phase and the water-soluble phase. Methods for phase separation include, for example, centrifugation and heating.

[0074] The present inventors have found that by examining various production conditions as shown in the Examples, a composition with a high oil ratio can be obtained using the above composite particles. The oil ratio is not particularly limited as long as it is 50% by mass or more, but is preferably 70% by mass or more, more preferably 72% by mass or more, even more preferably 74% by mass or more, particularly preferably 76% by mass or more, and most preferably 80% by mass or more.

[0075] The present inventors further found that, as shown in the examples, emulsion compositions with a high oil content and even non-flowable compositions can be obtained by adjusting the volume ratio of composite particles to the total volume of the composition to be more than 0.10 and not more than 0.20. In such compositions, compositions containing composite particles and the dispersed phase at a volume occupancy of 74% or more, which is the closest packing of spheres formed by the composite particles and the dispersed phase, were also obtained.

[0076] As a result of obtaining a composition with a high oil ratio as described above, it is possible to produce a composition containing a high concentration of an active ingredient that dissolves in the oil phase, particularly in an O / W composition in which the dispersed phase is an oil phase. Examples of active ingredients include various active ingredients in quasi-drugs used in cosmetics. As shown in the examples, it was unexpected that a very high oil ratio could be obtained not only in a non-flowable composition but also in a flowable composition.

[0077] One embodiment of the composition of the present disclosure provides a non-flowable oil-in-water composition. A composition can be determined to be non-flowable if, at room temperature (25°C), a vial containing the composition is inverted without dripping and maintains the same appearance as when the vial is upright. In a non-flowable oil-in-water composition, the oil ratio is particularly preferably 74% by mass or more. Because the composition of the present disclosure has a high internal phase ratio, stable oil droplets come into contact with each other, generating frictional forces, making it possible to obtain a non-flowable composition as described above even without the addition of a thickener. Using a composition that does not contain a thickener, it is possible to provide cosmetics with a refreshing feel. Furthermore, the composition of the present disclosure, which is a Pickering emulsion without a thickener, generates a novel feel, allowing the provision of formulations (creams, cleansers, etc.) with a unique feel.

[0078] The volume ratio of the continuous phase in the composition of the present disclosure is represented by φ C , the volume ratio of the dispersed phase is φ D , the volume ratio of the composite particles is φ P In the composition of the present disclosure, C , φ D , φ P The sum of is 1. P The volume of the composite particle Vp (cm 3 ) is calculated using the following formula, where the composite particles are assumed to be spheres: Vp(cm 3 )=π×Ds 3 ×(1 / 6)×Np×10 -12 π: Pi Ds (μm): Composite particle diameter obtained from scanning electron microscope (SEM) Np (pieces): total number of composite particles Here, Np is calculated by the following formula: Np (units) = (S A ×m)÷(π×Ds 2 ) S W (μm 2 / g): specific surface area of ​​composite particles (mass basis) m (g): total mass of the composite particles And S W is calculated by the following formula: S W (μm 2 / g) = 6 ÷ (Ds × ρ) ρ(1.2×10 -12 g / μm 3 ): Density of composite particles Here, the value of ρ is based on that of polymethyl methacrylate. The value will change depending on the material that makes up the hydrophobic polymer. For example, polystyrene has a value of 1.0 x 10 -12 g / μm 3 , and polybutyl acrylate is 1.1 × 10 -12 g / μm 3 These values ​​may be values ​​obtained from literature or experiments.

[0079] The particle diameter Ds obtained from a scanning electron microscope (SEM) was measured by photographing the field of view of the SEM, reading the particle diameters of any 20 recognizable particles on a scale, and taking the average of the diameters. Ds is not particularly limited as long as the desired composition is obtained, but is preferably 100 to 900 nm, more preferably 200 to 800 nm. φ in the composition C , φ D , φ P is not particularly limited as long as the desired composition can be obtained, but is preferably φ C is 0.1 to 0.2, or φ P is 0.1 to 0.2, and more preferably φ C is 0.1 to 0.2 and φ P is 0.1 to 0.2. From a practical standpoint, the mass of the composite particles is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 8.0% by mass or less, relative to the total mass of the composition, and is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1.0% by mass or more.

[0080] The composition of the present disclosure may contain a surfactant to promote emulsification during production. There are no limitations on the type or amount of surfactant, as long as the effects of the present invention are obtained. Examples of types of surfactant include nonionic surfactants, anionic surfactants, cationic surfactants, and polymeric emulsifiers. The amount of surfactant may be 0 to 1% by mass of the emulsion composition, preferably 0 to 0.5% by mass, and more preferably the composition of the present disclosure does not contain a surfactant.

[0081] The composition of the present disclosure may contain a thickener to suppress fluidity. There are no limitations on the type or amount of the thickener, as long as the effects of the present invention are achieved. Examples of types of thickeners include acrylic acid-based thickeners, cellulose-based thickeners, mucopolysaccharide-based thickeners, amino acid-based thickeners, seaweed-based thickeners, microbial-derived thickeners, polyethylene glycol-based thickeners, and starch-based thickeners. The amount of thickener may be 0 to 1.0% by mass of the emulsion composition, preferably 0 to 0.5% by mass, and more preferably the composition of the present disclosure does not contain a thickener.

[0082] <Method of producing the composition> The composition of the present disclosure can be produced by mixing and stirring the composite particles, water, oil, and, if necessary, various additives. At this time, the volume ratio of the composite particles, water, and oil is preferably within the above-mentioned preferred range of φ C , φ D , φ PIt is preferable to mix them so that the above ratio satisfies the above condition. For example, the oil or fat may be mixed in an amount 20 to 60 times, preferably 24 to 55 times, the mass of the composite particles. Furthermore, 21% by mass to 30% by mass of water may be mixed in an amount relative to the mass of the oil or fat. In this way, the composition of the present disclosure can be obtained simply by mixing and stirring the components. When using a dispersion in which the composite particles are dispersed in a solvent such as water or alcohol, the water and oil or fat may be added taking into account the volume of the solvent in the dispersion. The composition of the present disclosure can be made suitable for use even without blending 1,3-butanediol.

[0083] The stirring speed is preferably 1000 rpm to 20000 rpm, and more preferably 20000 rpm to 10000 rpm. The stirring time is preferably 1 minute to 5 minutes.

[0084] <Uses of the composition> The use of the composition of the present disclosure is not particularly limited, and it can be used as cosmetics, pharmaceuticals, quasi-drugs, etc. In particular, non-flowable compositions can be used as cream-type or wax-type products. The composition of the present disclosure can be formulated with an appropriate combination of various main ingredients / active ingredients and various additives depending on the above-mentioned use.

[0085] When the composition of the present disclosure is, for example, a cosmetic, pharmaceutical, or quasi-drug, various commonly used additives can be blended into the aqueous phase or oil phase of the composition, as long as they do not impair the effects of the present invention. Examples of such additives include antioxidants, gelling agents, thickeners, oils, alcohols, ethers, water, pH adjusters, stabilizers, bactericides, antifungal agents, preservatives, colorants, chelating agents, moisturizers, pearlescent agents, fragrances, UV absorbers, UV scattering agents, and various skin-beautifying ingredients (e.g., whitening agents, cell activators, anti-inflammatory agents, blood circulation promoters, skin astringents, antiseborrheic agents, etc.). [Example]

[0086] The present invention will be specifically explained below by way of examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0087] <Analysis method> The Z-average particle size (Dh), dispersity (PdI), and average zeta potential were measured using a particle size, zeta potential, and molecular weight analyzer (Zetasizer Nano ZSP, Malvern Panalytical). The analysis software used was Malvern's Zetasizer Software 7.12. The dielectric constant, Henry coefficient, and viscosity of the dispersion medium used for particle size, PdI, and zeta potential measurements were 78.5 (water at 25°C), 1.5 (Henry's coefficient), and 0.89 mPa·s (dispersion medium viscosity). The solid content of the aqueous dispersion samples was adjusted to 10 mg / L. The solid content after particle synthesis was calculated by weighing each dispersion and then heat-drying or freeze-drying it, and then calculating the mass difference before and after drying. The SEM particle size (Ds) was measured by scanning electron microscopy (SEM). A Nova NanoSEM 450 SEM from FEI was used. From the obtained observation images, at least 10 particles were selected and their average value was used to calculate Ds using NaviCam software manufactured by Sony Computer Science Laboratories, Inc. The solid mass was calculated from the difference in mass before and after drying by weighing any emulsion of each particle dispersion and then subjecting it to heat drying or freeze drying.

[0088] <Observation of emulsion composition> Oil droplets can be observed using a microscope, or emulsion compositions using PMMA-PVA particles and oil droplets containing fluorescent reagents can be observed three-dimensionally using a confocal microscope.

[0089] <Production Examples 1 to 5: Synthesis of polymethyl methacrylate (PMMA) particle dispersions> Methyl methacrylate (MMA), argon-substituted ion-exchanged water, methanol (Production Examples 4 and 5), and coumarin 6 (Production Examples 3 and 5) were added to a 30 mL transparent glass vial (production example SV-30, manufactured by Nichiden Rika Glass Co., Ltd.) to the specified volume in the formulation shown in Table 1. An aqueous solution of 23 mg of ADIP (hereinafter referred to as ADIP-Cl), a cationic radical polymerization initiator whose counter anion is chloride ion, dissolved in 1.0 g of water was added, and the mixture was stirred with a powerful stirrer in a water bath at a specified temperature for a specified time to obtain a PMMA dispersion. The synthesis conditions and analytical results of the PMMA particle dispersion are shown in Table 1. The measured values ​​for Z-average particle size and PdI are shown as mean ± SD (n = 3). In Production Examples 4 and 5, the SEM particle size was approximately 570 nm, indicating that particles with larger particle sizes were obtained than in Production Examples 1 to 3. In Production Examples 3 and 5, coumarin 6 (3-(2-benzothiazolyl)-7-(diethylamino)coumarin) was added to the monomer for the purpose of fluorescent labeling. The SEM particle size was almost the same under conditions where coumarin 6 was not added and when it was added, and coumarin 6 did not change the SEM particle size. In all production examples, the PdI measured by DLS was below 0.1, indicating that extremely monodisperse particles had been synthesized.

[0090] [Table 1]

[0091] <Dialysis treatment of Production Examples 4 and 5> After synthesis, Production Examples 4 and 5 contained methanol. Dialysis was performed to remove the effects of methanol on subsequent processes. Methanol was removed by dialysis (dialysis solution: ion-exchanged water) for 3 days or more using a Spectra / Por 3 Membrane (molecular weight cutoff: 3500, planar width: 45 mm, Part No. 132724). The aqueous dispersions after this dialysis were used for Production Examples 4 and 5.

[0092] <Production Examples 6 to 10: Synthesis of PMMA-PVA Dispersions> A 300 mL separable flask equipped with a baffle was charged with one of the above PMMA particle dispersions (PMMA particles listed in Table 2) to a final solids content of 4.8 g. 2.7 g of polyvinyl alcohol with the specified degree of polymerization and saponification listed in Table 2 was then added, followed by ion-exchanged water to a total mass of 199 g. The solution was then heated to 60 °C while stirring at 450 rpm. An aqueous solution of 38 mg of ADIP-Cl dissolved in 1 g of ion-exchanged water was then added, and the mixture was stirred at 450 rpm for 3 hours at 60 °C to obtain a PMMA-PVA dispersion. Visual observation of the properties of Preparation Examples 6 to 10 revealed that, even after 3 months of storage, the particles had settled, but did not form coarse aggregates. Light shaking confirmed that the dispersions returned to a uniformly dispersed state. This suggests that the resulting PMMA-PVA dispersions have good storage stability.

[0093] <Evaluation of aqueous dispersion stability: Salt tolerance test> The dispersion stability of the prepared PMMA particles or PMMA-PVA particles in a solution containing salt was evaluated. Samples were prepared with aqueous sodium chloride (NaCl) solutions with final concentrations of 0.001, 0.01, 0.1, and 1 mol / L, and with a particle solids concentration of 10 mg / L in each NaCl solution. The Z-average particle size and PdI were then measured using the methods described in the "Analysis Methods" section. The measurement results are shown in Table 2. All measurements represent the mean ± SD (n = 3). For the PMMA aqueous dispersions of Production Examples 1, 2, and 4, the Z-average particle size and PdI increased when the NaCl concentration was 0.1 mol / L or higher. At a 1 mol / L NaCl concentration, the Z-average particle size was 1000 nm or larger, the PdI was 0.2 or larger, and the particles aggregated in water. For PMMA-PVA particles in Production Examples 6, 7, 8, and 10, the Z-average particle size remained almost unchanged compared to the results measured at 0.001 mol / L, and the PdI was 0.2 or less, even at a 1 mol / L concentration. For PMMA-PVA particles in Production Example 9 using fully saponified PVA, the Z-average particle size and PdI increased when the NaCl concentration was 0.1 mol / L or higher, and aggregation occurred at a 1 mol / L concentration. These results demonstrate that PMMA-PVA particles coated with PVA exhibit good water dispersibility even at high salt concentrations of 1 mol / L in water. Furthermore, when comparing partially saponified PVA with fully saponified PVA, the partially saponified PVA exhibited better water dispersibility.

[0094] [Table 2]

[0095] <Preparation and evaluation of oil-in-water compositions> [Preparation of Composition] A transparent glass vial (trade name: SV-10, manufactured by Nichiden Rika Glass Co., Ltd., capacity 10 mL, 24 mm × 45 mm) was charged with the PMMA particle dispersions of Production Examples 1, 2, and 4 or the PMMA-PVA particle dispersions of Production Examples 6, 8, and 10, ion-exchanged water, and decamethylcyclopentasiloxane (abbreviation: DMCPS, trade name: KF-995, manufactured by Shin-Etsu Chemical Co., Ltd., specific gravity 0.96 g / cm 3) was added to make the total mass 10 g. The mixture was stirred for 2 minutes with the dial set to 25 using a handy microhomogenizer (product name: NS-310E3, shaft: NS-7, manufactured by Microtech Nichion Co., Ltd.).

[0096] [Evaluation of Composition: Emulsification Test] When the sample's appearance was observed 5 minutes after the end of stirring, and clear phase separation was observed, and the formation of a sufficient number of oil droplets was not confirmed under a microscope, the sample was rated as not emulsified (C). The microscope used was a Leica DM2000 LED (manufactured by Leica Microsystems).

[0097] [Evaluation of composition: inverted test] The vial containing the prepared emulsion composition was placed upside down, and the behavior of the emulsion composition in the vial was observed to evaluate the thickening effect. Non-emulsified samples were not evaluated for thickening and were marked with (-). When evaluating samples other than non-emulsified samples in the inversion test, if the emulsion composition fell, it was marked with (B), and if it did not fall, i.e., thickened, it was marked with (A). Table 3 shows the evaluation criteria for the thickening effect (emulsification test and inversion test).

[0098] [Table 3]

[0099] <Result> Comparative Example: Preparation of a Composition Containing a PMMA Particle Dispersion The amounts of each component and the evaluation (emulsification test) for the examples using PMMA particle dispersions of Production Examples 1, 2, and 4 are shown in Table 4. None of the particles were emulsified.

[0100] [Table 4]

[0101] [Formulation Examples 1 to 34: Compositions containing PMMA-PVA particle dispersions] The amounts of each component and the evaluation of the thickening effect (emulsification test and inversion test) for the examples using PMMA-PVA particle dispersions of Production Examples 6, 8, and 10 are shown in Tables 5, 6, and 7, respectively.

[0102] [Table 5]

[0103] [Table 6]

[0104] [Table 7]

[0105] The volume fraction of each component is shown in the triangular graph ABC in Figure 2. When the thickened formulation examples in Tables 5 to 7 are plotted, the shaded area in Figure 2, i.e., φ C is 0.1~0.2, φ P is 0.1 to 0.2, and φ D The region where the ratio is 0.6 to 0.8 is the region where many evaluations indicate emulsification and thickening. Although the reason why excellent thickening is shown in this region is not clear, it is thought that excellent thickening is shown because, under conditions where the volume of the water (continuous phase) is limited, there are sufficient particles at the interface between the water and the oil (dispersed phase), and the particles at two adjacent interfaces interact with each other, or by physical friction, or by a combination of these. Also, φ P In the range of more than 0.10 and not more than 0.20, an emulsion composition with at least a high internal phase was obtained. P In the prescription example where φ is greater than 0.10 and equal to or less than 0.20, P +φ D In the thickened formulations, the φ was greater than 0.74, which is considered to be the closest packing of spheres formed by the composite particles and oil. P +φ D It was.

[0106] Furthermore, for all of the above compositions that were confirmed to be emulsified, no phase separation or the like was observed by visual observation of the properties even after 3 months at room temperature of 25°C, and it was confirmed that the emulsified state was maintained, suggesting that the emulsion compositions also have good storage stability.

[0107] <Observation of high internal oil phase oil-in-water emulsion> [Method for observing emulsions using fluorescently labeled particles] Approximately 100 μL of the emulsion composition prepared in Formulation Example 21 was placed on a film-bottom dish (ibidi). Fluorescence observation was performed using a confocal laser microscope (trade name: LSM900, Zeiss) with a 63x oil immersion objective lens and a numerical aperture of 1.4, at an excitation wavelength of 473 nm and emission wavelengths of 485 nm to 585 nm. The focal plane was positioned 10 μm away from the bottom dish. The microscope image is shown in Figure 3. The white line in the figure indicates 50 μm. Observation revealed fluorescent particles present at the interface between the oil and water phases, and oil droplets were confirmed to be pentagonal, as in oil droplet 1, or hexagonal, as in oil droplet 2. Considering spherical packing, the close-packing ratio was 74%. It is known that when the ratio exceeds 74%, it becomes difficult to maintain a spherical shape, and the internal phase assumes a polyhedral shape. These results demonstrate that the emulsion composition is an oil-in-water emulsion composition with a high internal oil phase ratio, exceeding the close-packing ratio. [Explanation of symbols]

[0108] 1 Composite particles

Claims

1. A composition comprising an aqueous phase as a continuous phase, a dispersed phase, and particles at the interface between the aqueous phase and the dispersed phase, wherein the dispersed phase comprises an oil phase in contact with the interface, the particles are composite particles comprising a hydrophobic portion having a cationic group on the surface thereof and a hydrophilic polymer coating the surface, and the volume ratio of the composite particles to the total volume of the composition is greater than 0.10 and not more than 0.

20.

2. 2. The composition according to claim 1, wherein the sum of the volume ratio of the composite particles and the volume ratio of the dispersed phase to the total volume of the composition is 0.74 or more.

3. The composition of claim 1 in an emulsified state.

4. The composition according to claim 1, wherein the oil ratio, which is the mass ratio of the oil phase to the total mass of the aqueous phase and the oil phase, is 72 mass% or more.

5. The composition according to any one of claims 1 to 4, which is non-flowable.

6. The composition according to any one of claims 1 to 4, which is flowable.

7. The composition according to any one of claims 1 to 4, wherein the composite particles have a Z-average particle size of 100 nm or more.

8. The composition according to any one of claims 1 to 4, wherein the hydrophobic portion having a cationic group on a surface thereof comprises a hydrophobic polymer obtained by polymerizing a hydrophobic monomer in the presence of a cationic radical polymerization initiator, and the cationic group is a residue of the cationic radical polymerization initiator.

9. The composition of claim 8 , wherein the hydrophobic monomer is a (meth)acrylic acid-based monomer.

10. The composition of claim 9 wherein the hydrophilic polymer is polyvinyl alcohol.

11. A method for producing a composition comprising: a step of mixing and stirring composite particles, each of which comprises a hydrophobic portion having a cationic group on its surface and a hydrophilic polymer coating the surface; water; and an oil or fat; wherein the mass of the oil or fat is 20 to 60 times the mass of the composite particles; an aqueous phase as a continuous phase; a dispersed phase; and the composite particles at the interface between the aqueous phase and the dispersed phase.

12. The method according to claim 11, wherein the mass of the oil or fat is 24 to 55 times the mass of the composite particles.

13. The manufacturing method according to claim 11 or 12, wherein the mass of the water is 21% by mass to 30% by mass with respect to the mass of the fat or oil.

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