Oil-based emulsions in water

Abstract

To provide an oil-in-water emulsion composition that demonstrates adequate antibacterial properties, excellent usability, and good emulsion stability, with no restrictions on aqueous phase components.SOLUTION: An oil-in-water emulsion composition includes the following components (a) to (d): (a) particles composed of a polymer that includes a hydrophobic part with a cationic group, including a hydrophobic monomer unit, and a hydrophilic part including at least a hydrophilic monomer unit represented by the formula (I); (b) a polyhydric alcohol; (c) an oil solution; and (d) water.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oil-in-water emulsion composition having excellent antibacterial properties. [Background technology]

[0002] Emulsified compositions, such as oil-in-water and water-in-oil compositions, generally exist stably due to the fine mixing of aqueous and oily components through the emulsifying action of the surfactants used. Such emulsions are widely used in daily necessities, personal care products, and biomedical applications. However, if a large amount of surfactant is used in an emulsion, it 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 surfactants that can be absorbed by the human body on the body. For this reason, it is desirable to minimize the amount of surfactant used in emulsions.

[0003] Against this backdrop, attempts are being made to utilize additives with emulsifying properties other than surfactants in oil-in-water emulsion compositions. One such attempt that is attracting attention is an oil-in-water emulsion composition in which solid particles are present near the interface between the oil phase and the aqueous phase.

[0004] Figure 1 is a schematic comparison of an emulsion containing a surfactant and an oil-in-water emulsion composition (hereinafter also referred to as "oil-in-water emulsion composition emulsified by solid particles"), which is emulsified by placing solid particles near the interface between the oil phase and the aqueous phase. Although the present invention is not bound by any theory, oil-in-water emulsion compositions emulsified by solid particles are generally sometimes called Pickering emulsions, and it is presumed that mineral particles or amphiphilic organic particles are present at the interface of aqueous or oily droplets, and the structure of the droplets is stabilized.

[0005] As mentioned above, there has been a certain demand for emulsified compositions that do not use surfactants. As an example of an oil-in-water emulsion composition that substantially does not contain surfactants as emulsifiers, Patent Document 1 discloses an oil-in-water emulsion composition comprising (1) an oil phase, (2) an aqueous phase, and (3) a finely milled inorganic pigment selected from the group consisting of amphiphilic metal oxides having an average particle size of less than 200 nm.

[0006] Incidentally, water-containing emulsions require preservative measures. However, in recent years, the inclusion of so-called antibacterial agents such as parabens, which are widely used in cosmetics and other products, is becoming unacceptable to consumers because they can cause skin irritation. For this reason, there is a demand for emulsions that do not contain parabens and are safe for the skin and eyes. It is known that antibacterial components such as polyhydric alcohols can be used as an alternative to antibacterial agents, but when antibacterial components are usually added to an emulsion, the antibacterial component tends to be distributed into the aqueous phase, thereby exhibiting the antibacterial properties of the emulsion. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Special Publication No. 2001-518111 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, among oil-in-water emulsion compositions, particularly those with a high oil-in-water phase, problems have arisen such as the limited types of components in the aqueous phase due to the small amount of aqueous phase components, the inability of antibacterial components to be properly distributed into the aqueous phase, and a decrease in the antibacterial properties of the oil-in-water emulsion composition. Therefore, the present invention has been made in view of the above problems, and aims to provide an oil-in-water emulsion composition that has no limitations on aqueous phase components, possesses sufficient antibacterial properties, has excellent usability, and has good emulsion stability.

[0009] In view of the above problems, the inventors of the present invention conducted intensive research. As a result, according to an oil-in-water type emulsion composition containing particles containing a polymer having a hydrophobic part containing a hydrophobic monomer unit, a cationic group, and a hydrophilic part containing at least a hydrophilic monomer unit represented by the following formula (I), a polyhydric alcohol, an oil agent, and water, it was found that the above problems can be solved, and the present invention has been completed.

Means for Solving the Problems

[0010] That is, the present invention provides the following.

[0011] The first aspect of the present invention is an oil-in-water type emulsion composition containing the following components (a) to (d); (a) Particles containing a polymer having a hydrophobic part containing a hydrophobic monomer unit and having a cationic group, and a hydrophilic part containing at least a hydrophilic monomer unit represented by the following formula (I), (b) a polyhydric alcohol, (c) an oil agent, and (d) water.

Chemical formula

[0012] The second aspect of the present invention is the oil-in-water type emulsion composition according to the first aspect, wherein the polyhydric alcohol is one or more selected from the group consisting of glycerin, ethylhexyl glycerin, 1,3-butylene glycol, propylene glycol, dipropylene glycol, isoprene glycol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol.

[0013] The third aspect of the present invention is the oil-in-water type emulsion composition according to the first or second aspect, wherein the blending amount of the oil agent is 55% by mass or more and 80% by mass or less based on the total amount of the oil-in-water type emulsion composition.

[0014] The fourth aspect of the present invention is the oil-in-water type emulsion composition according to any one of the first to third aspects, wherein the oil-in-water type emulsion composition substantially does not contain a surfactant as an emulsifier.

[0015] A fifth aspect of the present invention is an oil-in-water emulsion composition according to any one of the first to fourth aspects, wherein the cationic group is derived from a cationic radical polymerization initiator.

[0016] A sixth aspect of the present invention is that the cationic radical polymerization initiator is 2,2'-[diazene-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1H-imidazole-3-ium)=ditrifluoromethanesulfonate (ADIP), 2,2'-[diazene-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1H-imidazole-3-ium) = The oil-in-water emulsion composition described in the fifth embodiment above, which is one or more selected from the group consisting of dichloride (ADIP-Cl), 2,2'-azobis(2-methylpropionamidine)dihydrochloride (V-50), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (VA-061).

[0017] A seventh aspect of the present invention is an oil-in-water emulsion composition according to any one of the first to sixth aspects, wherein the hydrophilic portion further comprises monomer units represented by the following formula (II), and the ratio (degree of saponification) of the number of monomer units represented by the following formula (I) to the total number of monomer units represented by the following formula (II) is 70% or more and 99% or less. [ka] [Effects of the Invention]

[0018] The oil-in-water emulsion composition of the present invention has sufficient emulsification stability even without substantially using surfactants, is not limited in the type of aqueous phase component used, and the antibacterial component is properly distributed in the aqueous phase, exhibiting sufficient antibacterial activity. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic comparison diagram of emulsions using surfactants and emulsions using solid particles. [Modes for carrying out the invention]

[0020] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are for illustrative purposes only, and the following description in these embodiments should not be construed as limiting the language of the claims.

[0021] <Oil-in-water emulsion composition> The oil-in-water emulsion composition of this embodiment comprises (a) particles containing a polymer having a hydrophobic portion having a cationic group containing hydrophobic monomer units and a hydrophilic portion containing at least predetermined hydrophilic monomer units, (b) a polyhydric alcohol, (c) an oil, and (d) water. The oil-in-water emulsion composition of this embodiment has a good feel after application and also exhibits excellent emulsification stability as an oil-in-water emulsion composition. Furthermore, the type of aqueous phase component used is not limited, and the antibacterial component is properly distributed into the aqueous phase, exhibiting sufficient antibacterial activity. From the viewpoint of improving the feel after application, it is preferable that the oil-in-water emulsion composition of this embodiment substantially does not contain surfactants or inorganic oxides (usually fine inorganic particles with an average primary particle diameter of about 1 nm to 200 nm) as emulsifiers. Furthermore, "substantially absent" means, for example, that the content in the oil-in-water emulsion composition of this embodiment is less than 1% by mass. From the viewpoint of providing a good feel after application, it is preferably less than 0.5% by mass, more preferably 0.3% by mass or less, and even more preferably 0.1% by mass or less.

[0022] Furthermore, the oil-in-water emulsion composition of this embodiment can be prepared without using equipment that generates strong external forces industrially, such as ultrasonic devices or homogenizers, and heat treatment for stabilizing the dispersion state is not necessarily required. Therefore, this embodiment can also contribute to reducing the environmental burden during the preparation of the oil-in-water emulsion composition. However, the present invention also includes oil-in-water emulsion compositions prepared using ultrasonic devices, homogenizers, etc., within its scope of rights.

[0023] [(a) Particle] The oil-in-water emulsion composition of this embodiment contains particles comprising a polymer having hydrophobic monomer units, a hydrophobic portion having a cationic group, and a hydrophilic portion containing predetermined hydrophilic monomer units. The particle content in the oil-in-water emulsion composition of this embodiment is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.5% by mass or more and 4.0% by mass or less. By having a particle content within the above range, the oil-in-water emulsion composition of this embodiment will have sufficient emulsification stability even without substantially using surfactants.

[0024] (Hydrophobic part) As described above, the hydrophobic portion contains hydrophobic monomer units, and examples of these "hydrophobic monomer units" include monomer units obtained from monomers having an ethylenically unsaturated double bond. Here, examples of monomers having an ethylenically unsaturated double bond include polymerizable monomers that have a carbon-carbon double bond in their molecule, and more specifically, (meth)acrylic acid monomer units and styrene monomer units.

[0025] Here, examples of (meth)acrylic acid monomer units include monomer units derived from alkyl (meth)acrylate having an alkyl ester group having 1 to 6 carbon atoms. Examples of alkyl ester groups having 1 to 6 carbon atoms include methyl ester group, ethyl ester group, n-propyl ester group, n-butyl ester group, n-pentyl ester group, and n-hexyl ester group. These alkyl ester groups may, if necessary, have one or more hydrogen atoms of the alkyl group constituting the alkyl ester group substituted with a hydroxyl group. From the viewpoint of ensuring sufficient storage stability of the particles, alkyl ester groups having 1 to 4 carbon atoms are more preferable.

[0026] Preferably, methyl methacrylate (MMA), butyl methacrylate (BMA), or 2-hydroxyethyl methacrylate (HEMA) are used as such alkyl (meth)acrylates, with methyl methacrylate being more preferable. When these monomers are used, the storage stability of the resulting particles is improved, and the emulsifying ability of the particles is also enhanced.

[0027] Furthermore, if the (meth)acrylic acid 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.

[0028] Examples of styrene-based monomer units 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. Among these, styrene is preferred from the viewpoint of ensuring sufficient storage stability and emulsifying ability of the resulting particles.

[0029] When preparing a hydrophobic moiety containing hydrophobic monomer units and having a cationic group using the monomers described above, it is generally possible to radically polymerize the monomers.

[0030] (cationic group) The cationic groups in the hydrophobic portions of the particles contained in the oil-in-water emulsion composition of this embodiment are generally assumed to be cationic groups derived from a cationic radical polymerization initiator. However, they are not limited to cationic groups derived from a cationic radical polymerization initiator, and cationic groups derived from any compound or polymerization unit that can introduce any cationic group at the terminal or in the hydrophobic portion can be mentioned. Specific examples of such cationic groups include primary amino groups, secondary amino groups, tertiary amino groups, quaternary ammonium groups, imidazole groups, imidazolium groups, pyridyl groups, pyridinium groups, piperidyl groups, piperidinium groups, pyrrolidinyl groups, pyrrolidinium groups, phosphonium groups, and the like. However, in this embodiment, it is particularly preferable to use a cationic radical polymerization initiator as the polymerization initiator to polymerize the hydrophobic monomer, thereby adopting the cationic group introduced at the terminal of the hydrophobic portion as the cationic group. By using a cationic radical polymerization initiator, the terminal structure derived from the cationic radical polymerization initiator can be covalently bonded to the monomer units at the ends of the hydrophobic portion. In this embodiment, the core portion includes a hydrophobic portion, and cationic groups are arranged on or near the surface of the core portion, which can result in particles with excellent emulsifying ability.

[0031] (Cationic radical polymerization initiator) In this embodiment, cationic radical polymerization initiators that balance safety after polymerization with reactivity as radical polymerization initiators can generally be used, but more specifically, 2,2'-[diazene-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1H-imidazole-3-ium)=ditrifluoromethanesulfonate (ADIP), 2,2'-[diazene-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1 It is preferable to use one or more selected from the group consisting of H-imidazole-3-ium) dichloride (ADIP-Cl), 2,2'-azobis(2-methylpropionamidine) 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.). Using these cationic radical polymerization initiators results in better emulsification ability of the resulting particles.

[0032] In addition, examples of the radical polymerization initiator that can be used in the present embodiment include, for example, a cationic radical polymerization initiator represented by the general formula (III). For further details regarding the following cationic radical polymerization initiator, for example, refer to Japanese Patent Application Laid-Open No. 2017-051113. The content of this document is incorporated herein by reference. Specific examples of the cationic radical polymerization initiator represented by the general formula (III) include ADIP and ADIP-Cl described above. By using ADIP or ADIP-Cl, particles contained in the oil-in-water type emulsion composition of the present embodiment can be prepared under milder reaction conditions, and it is also possible to suppress a decrease in the storage stability of the particles due to damage such as heating during the preparation of the particles. Further, by using ADIP or ADIP-Cl, as described above, particles contained in the oil-in-water type emulsion composition of the present embodiment can be prepared under milder reaction conditions, and thus it can also contribute to the environmental load during synthesis.

Chemical Formula

[0033] The term "counter anion" in the cationic radical polymerization initiator of formula (III) above is not particularly limited as long as it is an anion that is commonly used as a counter anion for organic compounds in the field of organic chemistry, and includes, for example, halide anions (chloride ion, bromide ion, fluoride ion, iodide ion), conjugate bases of organic acids (e.g., acetate ion, citrate ion, trifluoroacetate ion), nitrate ion, sulfate ion, carbonate ion, etc. Preferred counter anions in this embodiment include, for example, trifluoromethanesulfonate ion (triflate), chloride ion, nitrate ion, etc. Among these, chloride ions, acetate ions, and citrate ions are preferred, and chloride ions are more preferred, from the viewpoint of significantly improving the emulsification stability of the oil-in-water emulsion composition of this embodiment, increasing the yield of particles when preparing the particles contained in the oil-in-water emulsion composition of this embodiment, and improving manufacturing costs.

[0034] (Hydrophilic part) The hydrophilic portion of the particles contained in the oil-in-water emulsion composition of this embodiment more specifically includes a hydrophilic monomer unit represented by the following formula (I). [ka]

[0035] The hydrophilic monomer unit represented by formula (I) above is not particularly limited, but can generally be obtained by polymerizing vinyl acetate by a radical polymerization reaction and hydrolyzing (saponifying) the acetate ester group. Therefore, in this embodiment, although the hydrophilic portion always contains the hydrophilic monomer unit represented by formula (I) above, not all monomer units of the hydrophilic portion are limited to those represented by formula (I) above. More specifically, the hydrophilic portion comprises a monomer unit represented by the following formula (II) and a monomer unit represented by the following formula (I), derived from vinyl acetate. The ratio of the hydroxyl groups (sometimes simply referred to as "saponification degree" in this invention) to the total number of acetate groups in the monomer unit represented by the following formula (II) and the hydroxyl groups in the monomer unit represented by the following formula (I) is preferably 70% to 99%, more preferably 75% to 98%, and even more preferably 78% to 96%, from the viewpoint of improving the storage stability and emulsifying ability of the particles themselves and ensuring good emulsification stability of the oil-in-water emulsion composition formed using these particles. By adjusting this "saponification degree," the degree of hydrophilicity in the hydrophilic portion of the particles is adjusted. Therefore, it is preferable to adjust the "saponification degree" appropriately according to the intended use of the oil-in-water emulsion composition of this embodiment. [ka]

[0036] (The core of the particle) The particles contained in the oil-in-water emulsion composition of this embodiment have organic groups exposed on at least their surface, but their core may consist only of organic groups, or is not limited to consisting only of such organic groups, and may also contain inorganic materials. When the core of the particles contained in the oil-in-water emulsion composition of this embodiment contains inorganic materials, one example is to bond or associate a polymer containing hydrophobic monomer units to the surface of the inorganic substance in the core.

[0037] (Cross-linkable monomer) As organic monomer units constituting the core, crosslinkable monomer units may be used. In such embodiments, crosslinkable monomers may be partially used as one of the monomers that prepare the particles contained in the oil-in-water emulsion composition of this embodiment. 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, it is not necessary to use such crosslinkable monomers. If they are used, from the viewpoint of ensuring sufficient storage stability of the particles, their content can be set in a range of typically 0.1% to 20%, preferably 3% to 10%, and more preferably 5%, on a molar basis, relative to the monomers constituting the hydrophobic portion and the monomers constituting the hydrophilic portion, respectively. 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.

[0038] (Combinations of hydrophobic and hydrophilic parts) The above particles include a polymer having a hydrophobic portion and a hydrophilic portion. In the above particles, from the viewpoint of improving the emulsifying ability of the particles, it is preferable that the surface of the core portion of the particles is hydrophobic, and that part or all of it is directly or indirectly coated with a hydrophilic monomer or its polymer. More specifically, the hydrophobic monomer unit and the hydrophilic monomer unit may be bonded by covalent bonds ("directly coated"), or the hydrophobic monomer unit and the hydrophilic monomer unit may be bonded by intermolecular forces ("indirectly coated").

[0039] Furthermore, when hydrophobic monomer units and hydrophilic monomer units are covalently bonded, the polymer formed by the covalent bond between them may be a block copolymer or a graft copolymer. However, in particular, a graft copolymer is preferable because it provides better storage stability for the particles.

[0040] Furthermore, when hydrophobic monomer units and hydrophilic monomer units are bonded by intermolecular forces, it is preferable that the bonding by intermolecular forces is brought about by heat treatment, from the viewpoint of improving the storage stability of the particles and the emulsifying ability of the particles. Examples of heat treatment in this case include heat treatment 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.

[0041] Furthermore, the above-mentioned particles are not limited to particles in which hydrophobic monomer units and hydrophilic monomer units are bonded only by covalent bonds or only by intermolecular forces. Some hydrophobic monomer units may be bonded to hydrophilic monomer units by covalent bonds, while the remaining hydrophobic monomer units are bonded to hydrophilic monomer units by intermolecular forces. From the viewpoint of ensuring good emulsifying ability of the particles, the proportion of hydrophobic monomer units bonded to hydrophilic monomer units is preferably 10% to 90%, more preferably 30% to 70%, and even more preferably 40% to 60% of the total hydrophobic monomer units bonded to hydrophilic monomer units.

[0042] In the embodiments described above, from the viewpoint of improving the emulsification stability and degree of emulsification of the oil-in-water emulsion composition of this embodiment, the ratio of hydrophobic and hydrophilic portions is preferably such that the amount of the hydrophilic portion is 1 to 6 parts by mass, and more preferably 3 to 4 parts by mass, relative to 100 parts by mass of the hydrophobic portion.

[0043] (Cumulant average diameter) The average cumulant diameter of the above-mentioned particles is calculated by measuring the intensity of scattered light from particles undergoing Brownian motion in the dispersion medium in a dispersion containing the particles, and observing the temporal variation of that intensity (dynamic light scattering method). In this embodiment, the average cumulant diameter of the particles is preferably 100 nm to 500 nm, and more preferably 150 nm to 450 nm, from the viewpoint of improving the storage stability of the particles, improving the emulsifying ability of the particles, and improving the emulsification stability of the emulsified composition.

[0044] [(b) Polyhydric alcohols] The oil-in-water emulsion composition of this embodiment contains a polyhydric alcohol. The polyhydric alcohol content in the oil-in-water emulsion composition of this embodiment is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less. The polyhydric alcohol is not particularly limited as long as it is one that is commonly used in cosmetics, etc., but from the viewpoint of antibacterial properties, it is preferable to use one or more selected from the group consisting of glycerin, ethylhexylglycerin, 1,3-butylene glycol, propylene glycol, dipropylene glycol, isoprene glycol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol, and it is particularly preferable to use one or more selected from the group consisting of 1,3-butylene glycol, dipropylene glycol, and 1,2-pentanediol.

[0045] [(c) Oils] The oil-in-water emulsion composition of this embodiment contains an oil. The oil content in the oil-in-water emulsion composition of this embodiment is preferably 55% to 80% by mass, and more preferably 60% to 75% by mass. By keeping the oil content within the above range, the emulsion stability of the oil-in-water emulsion composition can be sufficiently maintained while also providing a good feel for use. Furthermore, even if the oil content of the oil-in-water emulsion composition is higher than usual, as described above, it will still exhibit sufficient antibacterial properties. The oil is not particularly limited in terms of properties or type, as long as it is commonly used in cosmetics, etc., but from the viewpoint of emulsion stability and feel, it is preferable that it be one or more selected from hydrocarbon oils, silicone oils, and ester oils.

[0046] More specifically, as the hydrocarbon oil, one or more selected from the group consisting of mineral oil, liquid paraffin, squalene, squalane, hydrogenated polydecene, and hydrogenated polyisobutene can be used. As the silicone oil, linear polysiloxane and / or cyclic polysiloxane can be used. Examples of linear polysiloxanes include dimethylpolysiloxane and methylphenylpolysiloxane, and examples of cyclic polysiloxanes include cyclohexasiloxane and cyclopentasiloxane. As the ester oil, one or more selected from the group consisting of cetyl ethylhexanoate, 1,3-butylene glycol diisononanoate, 1,3-butylene glycol di2-ethylhexanoate, dipropylene glycol diisononanoate, dipropylene glycol di2-ethylhexanoate, isononyl isononanoate, neopentyl glycol dicaprate, ethylhexyl palmitate, isostearyl neopentanoate, octyldodecyl stearoyl oxystearate, and jojoba oil can be used.

[0047] The choice of which of the oils listed above to use can be appropriately determined according to the intended use, expected usage amount, and usage conditions of the oil-in-water emulsion composition of this embodiment. If necessary, multiple types of oils, which may originate from multiple categories, can be used in combination.

[0048] [(d)Water] The oil-in-water emulsion composition of this embodiment contains water. The water is added to form the oil-in-water emulsion composition and is not particularly limited as long as it is the type commonly used in cosmetics and the like. In addition to water, purified water, hot spring water, deep-sea water, or steam-distilled water from plants may also be used, and one or more of these may be appropriately selected and used as needed. Furthermore, the amount added is not particularly limited and can be added in an amount appropriate to the amount of other components, but it is generally sufficient to use it in a range of 10% by mass or more and 40% by mass or less.

[0049] [Other antibacterial agents and antibacterial adjuvants] The oil-in-water emulsion composition of this embodiment may contain other antibacterial agents and antibacterial aids. Examples of antibacterial agents and antibacterial aids include sulfur, benzalkonium chloride, benzethonium chloride, chlorhexidine chloride, 2,4,4-trichloro-2-hydroxyphenol, halocarban, pionin (photosensitizer No. 201), hinokitiol, phenol, resorcinol, N-coconut oil fatty acid acyl L-arginine ethyl DL-pyrrolidone carboxylate, and the like. In particular, examples include antibacterial agents such as sulfur, pionin, N-coconut oil fatty acid acyl L-arginine ethyl DL-pyrrolidone carboxylate, trichlorocarbanilide, cetylpyridinium chloride, and hexachlorophene, as well as sorbic acid, parachlormethacresol, hinokitiol, phenoxyethanol, and parabens. These antibacterial agents and antibacterial aids may be used alone or in combination of two or more.

[0050] [Other additives] The oil-in-water emulsion composition of this embodiment may contain, as an optional component, various additives commonly used for the intended use, in addition to various active ingredients (for example, cosmetic active ingredients; such as whitening agents, cell activators, anti-inflammatory agents, blood circulation promoters, skin astringents, and anti-seborrheic agents) which may be added as needed depending on the intended use of the composition, to the extent that they do not impair the objective of the present invention. Examples of such additives include antioxidants, rust inhibitors, gelling agents, dispersants, thickeners, alcohols, ethers, pH adjusters, stabilizers, colorants, chelating agents, humectants, pearlescent agents, fragrances, UV absorbers, UV scattering agents, and the like.

[0051] <Method for manufacturing particles> The method for producing the particles used in the oil-in-water emulsion composition of this embodiment is not particularly limited, and includes methods such as 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 polymerization of the hydrophobic monomer is complete) to form particles. The method for producing the particles is not particularly limited, but for example, it may have the particle formation step shown below and may include a modification step or other steps.

[0052] [(1) Particulate process] The above particle formation process is not particularly limited, but examples include emulsion polymerization, suspension polymerization, dispersion polymerization, etc., which involve polymerizing monomer components such as hydrophobic monomers while forming particles. It is preferable that the polymerization reaction is carried out in the presence of an emulsifier. Alternatively, the above particle formation process may involve polymerizing the monomer components by solution polymerization, etc., and then forming the resulting reaction product into particles by phase inversion emulsification, suspension polymerization, etc.

[0053] However, from the viewpoint of reducing the complexity of manufacturing, a process of atomizing monomer components while polymerizing them is preferred, with emulsion polymerization, suspension polymerization, or dispersion polymerization being more preferred, and emulsion polymerization being even more preferred. Furthermore, among emulsion polymerization methods, it is preferable to adopt a soap-free emulsion polymerization method from the viewpoint that impurities such as emulsifiers do not mix into the surface of the hydrophobic core and do not affect subsequent modification steps described below. The specific method for implementing this soap-free emulsion polymerization method is not particularly limited and can be carried out by known methods. For example, it can be carried out by emulsion polymerization of monomer components in the presence of a polymerization initiator without using emulsifiers such as surfactants, polymer emulsifiers, or reactive surfactants.

[0054] The solvent used in the particle formation process is not particularly limited, but examples include aqueous media. The aqueous media used in the particle formation process may contain water or an alcohol containing a polyhydric alcohol, from the viewpoint of improving the storage stability of the particles. The reaction temperature when carrying out the particle formation process is preferably set to a temperature below the boiling point of the solvent.

[0055] [(2) Modification process] In the above modification step, for example, part or all of the surface of the hydrophobic portion is directly or indirectly coated with a hydrophilic monomer or a polymer of the hydrophilic monomer. Alternatively, in the above modification step, for example, polymerized hydrophobic monomer and polymerized hydrophilic monomer are bonded or associated.

[0056] Examples of directly coating the surface of the hydrophobic portion with the hydrophilic monomer, etc. include a method of covalently bonding hydrophobic monomer units present on the surface of the hydrophobic portion with the hydrophilic monomer units, more specifically, a method of covalently bonding atomic groups derived from a polymer of the hydrophilic monomer to atomic groups derived from hydrophobic monomer units present on the surface of the core portion, or a method of covalently bonding vinyl acetate, which is a hydrophilic monomer, to atomic groups derived from hydrophobic monomer units present on the surface of the core portion, further polymerizing vinyl acetate, and then saponifying the polyvinyl acetate portion by ester hydrolysis to form a hydrophilic portion. However, from the viewpoint of improving emulsification ability, it is preferable to adopt a method of covalently bonding a polymer containing the hydrophilic monomer units to atomic groups derived from hydrophobic monomer units present on the surface of the core portion as a method of directly coating the surface of the hydrophobic portion with the hydrophilic monomer, etc., and it is more preferable that the polymer containing the hydrophilic monomer units 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.

[0057] One way in which the surface of the hydrophobic portion is indirectly coated with the hydrophilic monomer, etc., is to cause the atomic groups contained in the hydrophobic monomer units present on the surface of the core portion (hydrophobic portion) to interact with the atomic groups contained in the hydrophilic monomer units by intermolecular forces, electrostatic interactions, etc. In this case, since the hydrophobic portion and the hydrophilic portion will interact as a result, any functional groups or atomic groups may be introduced into the hydrophobic portion and / or the hydrophilic portion to facilitate the interaction between the two. As a method for causing the atomic groups contained in the hydrophobic monomer units present on the surface of the hydrophobic portion and the atomic groups contained in the hydrophilic monomer units to interact by intermolecular forces, electrostatic interactions, etc., it is preferable to (1) add a polymer containing the hydrophilic monomer units to the particles obtained in the particle formation step, and introduce any functional groups or atomic groups as necessary, while appropriately setting the temperature, pressure, concentration conditions of the mixture, etc., and it is more preferable to heat, pressurize, or concentrate the mixture.

[0058] [Other processes] The above-described method for producing particles may include other steps in addition to (1) particle formation and (2) modification. The "other steps" to be added are not particularly limited, but include washing, concentration, and drying steps. For example, the washing, concentration, and drying steps may be incorporated into at least one of the steps of (1) particle formation and (2) modification, or they may be independent of the steps of (1) particle formation and (2) modification (temporarily or spatially).

[0059] The above particle manufacturing method preferably includes a washing step in order to reduce the irritancy of the composition containing the resulting particles. The medium used in the washing step is not particularly limited, and an aqueous medium can be used. For example, if the reaction solvent used in the particle formation step is an aqueous medium, the washing step can be carried out by repeating the operation of settling the particles by centrifugation, removing the supernatant, and then adding the aqueous medium to redisperse them. Alternatively, if the reaction solvent used in the particle formation step is an organic solvent, the washing step may be carried out by mixing an aqueous medium to which a salt such as brine has been added with the reaction solvent, stirring, and separating the aqueous phase from the organic phase using a separatory funnel or the like. By including a washing step in the above particle manufacturing method, the amount of unreacted radical polymerization initiators, their decomposition products, and unreacted monomers remaining in the medium can be reduced (for example, their concentrations can be reduced to less than 100 ppm).

[0060] The above-mentioned method for producing particles preferably includes a concentration step to increase the concentration of particles in the composition, from the viewpoint of fully exhibiting the emulsifying ability of the particles. Although not particularly limited, this concentration step may be carried out by centrifugation to settle the particles, removing the supernatant, and then redispersing by adding a medium in a quantity smaller than the mass and / or volume of the removed supernatant, or by drying the particles into a powder and then redispersing by adding a medium in a quantity smaller than the mass and / or volume of the medium removed by drying.

[0061] Furthermore, the method for producing the above particles preferably includes a drying step to bring the particles into a powder state. This drying step can be carried out by evaporating and drying the medium containing the particles. The 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. On the other hand, the oil-in-water emulsion composition of this embodiment can also be produced without drying, with the medium containing the above particles.

[0062] The above-described method for producing particles may consist of only one particle formation step, but it may also be a multi-step method that includes other steps in addition to the particle formation step.

[0063] If the method for producing the above-mentioned particles consists of only one particle formation step, it is preferable to configure the surface of the core portion of the particles to be hydrophobic by appropriately modifying the hydrophobic portion during the particle formation step, and to directly or indirectly coat a part or all of the surface of the core portion with a hydrophilic monomer or the like.

[0064] When the above-mentioned particle manufacturing method is a multi-step method including a particle formation step, it is preferable to use a two-step method including (1) a particle formation step and (2) a modification step, from the viewpoint of improving the storage stability of the particles and ensuring sufficient emulsifying ability by the particles. Furthermore, when the above-mentioned particle manufacturing method is a multi-step method including a particle formation step, it may also be a three-step or more method including one or more other steps, but the order of each step is not important, and each step may be repeated multiple times. When the above-mentioned particle manufacturing method is a two-step or more method including (1) a particle formation step and (2) a modification step, it is preferable to form a hydrophobic part (core part) in the (1) particle formation step, and to directly or indirectly coat a part or all of the surface of the hydrophobic part (core part) with a hydrophilic monomer or the like in the (2) modification step.

[0065] More specific methods for producing the particles are disclosed in detail in the following examples.

[0066] <Uses of oil-in-water emulsion compositions> The uses of the oil-in-water emulsion composition of this embodiment are not particularly limited, and it can be used as a cosmetic, pharmaceutical, quasi-drug, ink (including inks and pigment dispersions contained in stationery such as writing instruments), paint, etc. Depending on the above-mentioned uses, the oil-in-water emulsion composition of this embodiment can be formulated by appropriately combining various main components / active ingredients and various additives.

[0067] If the oil-in-water emulsion composition of this embodiment is, for example, a cosmetic, pharmaceutical, or quasi-drug, then various commonly used additives may be incorporated into the composition, to the extent that they do not impede the effects of the present invention. Examples of such additives include antioxidants, rust inhibitors, gelling agents, dispersants, thickeners, alcohols, ethers, pH adjusters, stabilizers, colorants, chelating agents, humectants, pearlescent agents, fragrances, UV absorbers, UV scattering agents, and the like.

[0068] For the sake of clarity, if we consider the case where the oil-in-water emulsion composition of this embodiment is used as a cosmetic, examples of active cosmetic ingredients include various skin-beautifying ingredients (for example, whitening agents, cell activators, anti-inflammatory agents, blood circulation promoters, skin astringents, anti-seborrheic agents, etc.). [Examples]

[0069] The present invention will be described in detail below with reference to examples. The following examples are provided for illustrative purposes only, and the content of the present invention is not limited in any way to these examples.

[0070] <Production Example 1; Synthesis of PMMA-PVA Dispersion 1> 42 g of methyl methacrylate (MMA) was added to a 300 mL baffled separable flask, and 166 g of argon-purified water (water purified with Elix Essential UV [Merck Millipore]; hereinafter sometimes simply referred to as "Elix water"; the resistivity of Elix water is 5 MΩ·cm or higher) was added. The mixture was heated to 80°C while stirring at 450 rpm using a sealed stirrer (product name: UZ-SM1, Nakamura Scientific Instruments Co., Ltd.) and a mantle heater. As a cationic radical polymerization initiator, 0.36 g of ADIP (hereinafter referred to as ADIP-Cl), whose counteranion is a chloride ion, was dissolved in 2 g of Elix water and the entire amount was added. After stirring for 6 hours, a PMMA dispersion was obtained.

[0071] In a 300 mL baffled separable flask, the above PMMA dispersion was added to a final solid content mass of 30 g. Then, 15 g of polyvinyl alcohol (saponification degree: 86% to 89%, degree of polymerization: 500) was added, and Elix water was added to bring the total mass to 198 g. The solution was then heated to 60°C while stirring at a stirring speed of 450 rpm. Next, 0.20 g of ADIP-Cl was dissolved in 2 g of Elix water and the entire amount was added. The mixture was stirred at 60°C and a stirring speed of 450 rpm for 3 hours to obtain PMMA-PVA dispersion 1.

[0072] <Experimental Examples 1 to 4: Preparation of Oil-in-Water Emulsifier Compositions> As shown in Table 1A (values ​​are in mass%), PMMA-PVA dispersion 1, Elix water, and 1,3-butylene glycol (BG) were uniformly mixed as aqueous components to obtain an aqueous phase composition. Cyclopentasiloxane (product name: KF-995, manufactured by Shin-Etsu Chemical Co., Ltd.) was added thereto, and the mixture was stirred at room temperature in a homomixer at 4,500 rpm for 1 minute to obtain the oil-in-water emulsion compositions of Examples 1 to 4. Observation of the properties and appearance 1 minute after the end of stirring confirmed that no phase separation was observed and that the mixture had been emulsified.

[0073] <Experimental Examples 5 to 10> Except for changing the amounts of each component as shown in Table 1B, the oil-in-water emulsion compositions of Experimental Examples 5 to 10 were prepared in the same manner as Experimental Example 1. The manufacturers of the various components used in the preparation of the oil-in-water emulsion compositions in the experimental examples are as follows. Dipropylene glycol (DPG) (Product name: DPG-FC (External Standard), manufactured by AGC Inc.) 1,2-Pentanediol (Pentylene Glycol) (Product Name: Diol PD, manufactured by Higher Alcohol Industry Co., Ltd.) Glycerin (Product name: Concentrated glycerin for cosmetics, manufactured by Lion Corporation) Cetyl ethylhexanoate (product name: Cetiol SN-1F, manufactured by BASF Japan Ltd.) Citric acid (Product name: Citric acid conforming to quasi-drug raw material standards, manufactured by Komatsuya Co., Ltd.) Sodium citrate (Product name: Sodium citrate, quasi-drug raw material standard, manufactured by Komatsuya Co., Ltd.)

[0074] <Comparative Experiment Examples 1 to 4> In place of PMMA-PVA dispersion 1, polyvinyl alcohol (product name: Gosenol EG-05C, degree of saponification: 86.5% to 89.0%, manufactured by Mitsubishi Chemical Corporation), which is commonly used as an emulsifier, was added. Except for changing the amount of each component as shown in Table 1C, oil-in-water emulsion compositions for comparative experiments 1 to 4 were prepared in the same manner as in experimental example 1.

[0075] <Comparative Experiment Examples 5 to 11> Without adding PMMA-PVA dispersion 1 or polyhydric alcohol, the oil-in-water emulsion compositions of Comparative Experiment Examples 5 to 10 were prepared by blending each component as shown in Table 1D. The same polyvinyl alcohol used in Comparative Experiment Examples 1 to 4 was used.

[0076] <Rating> The oil-in-water emulsion compositions prepared in Experimental Examples 1 to 10 and Comparative Experimental Examples 1 to 11 were evaluated for emulsification properties, emulsion stability, usability, and antibacterial properties using the following methods.

[0077] [Emulsifying property] The miscibility of the oil and water in the obtained oil-in-water emulsion composition was visually evaluated according to the following criteria. ○; Well emulsified △; There is some oily residue on the surface or a few oil droplets are floating on it. ×; Complete separation or obvious oil droplets present.

[0078] [Emulsification stability] To confirm the emulsion stability of the obtained oil-in-water emulsion composition over time, it was stored at room temperature and 35°C for one month, and changes in appearance were judged according to the following criteria. In the evaluation criteria below, "separation" refers to the state in which the oil in the emulsion layer has separated after standing. "Solidification" refers to the state in which part or all of the emulsion layer has solidified after standing and has lost its fluidity. Samples that received an "X" for emulsion performance were not evaluated. (Evaluation Criteria) ○: No problem (no separation or solidification) △: Very slight separation or a slight decrease in fluidity and a tendency towards solidification are observed. ×: Either obvious separation or obvious solidification occurs.

[0079] [Usability] Five trained expert panelists applied 0.5g each of the experimental and comparative oil-in-water emulsion compositions to the inner side of their forearms and evaluated the feel of the product after application based on the following criteria. The panelists made their decisions regarding the feel of the product through consensus. Products that received a negative evaluation for emulsification were not evaluated. (Evaluation Criteria) ○; It is not sticky and has a smooth texture. △: Slightly sticky ×; sticky

[0080] [Antibacterial] The preservative efficacy against microorganisms was tested using the method specified in ISO 11930. Specifically, four species—E. coli, P. aeruginosa, S. aureus, and C. albicans—were tested to see if they met the criteria described in Criteria A of the ISO preservative standards. Based on the number of species that met the criteria, the following evaluation was performed. (Evaluation Criteria) 〇:4 types △:3 types ×: 2 types or less

[0081] [Table 1A] [Table 1B]

Table 1C

Table 1D

Claims

1. Oil-in-water emulsion composition containing the following components (a) to (d); (a) Particles comprising a polymer having a hydrophobic portion having a cationic group containing hydrophobic monomer units, and a hydrophilic portion containing at least hydrophilic monomer units represented by the following formula (I), wherein the hydrophobic monomer units are units derived from methyl methacrylate, (b) Polyhydric alcohols, (c) Oils and (d) Water. 【Chemistry 1】

2. The oil-in-water emulsion composition according to claim 1, wherein the polyhydric alcohol is one or more selected from the group consisting of glycerin, ethylhexylglycerin, 1,3-butylene glycol, propylene glycol, dipropylene glycol, isoprene glycol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-octanediol.

3. The oil-in-water emulsion composition according to claim 1 or 2, wherein the content of the oil agent in the oil-in-water emulsion composition is 55% by mass or more and 80% by mass or less.

4. The oil-in-water emulsion composition according to claim 1 or 2, wherein the content of a surfactant as an emulsifier in the oil-in-water emulsion composition is less than 1% by mass.

5. The oil-in-water emulsion composition according to claim 1 or 2, wherein the cationic group is derived from a cationic radical polymerization initiator.

6. The cationic radical polymerization initiator is 2,2'-[diazen-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1H-imidazole-3-ium)=ditrifluoromethanesulfonate (ADIP), 2,2'-[diazen-1,2-diylbis(propane-2,2-diyl)]bis(1,3-dimethyl-4,5-dihydro-1H-imidazole-3-ium)=di The oil-in-water emulsion composition according to claim 5, comprising one or more selected from the group consisting of chloride (ADIP-Cl), 2,2'-azobis(2-methylpropionamidine)dihydrochloride (V-50), 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane] (VA-061).

7. The oil-in-water emulsion composition according to claim 1 or 2, wherein the hydrophilic portion further comprises monomer units represented by the following formula (II), and the ratio of the number of monomer units represented by formula (I) to the total number of monomer units represented by the following formula (II) (degree of saponification) is 70% or more and 99% or less. 【Chemistry 2】

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