W / o / w emulsion and method for producing same

Abstract

The purpose of the present invention is to provide: a W / O / W emulsion having good temporal stability; and a method for producing the same. The present invention relates to a W / O / W emulsion comprising an inner aqueous phase, an oil phase, and an outer aqueous phase, wherein a polyoxyethylene sterol ether is contained.

Description

W / O / W emulsion and its manufacturing method

[0001] The present invention relates to a W / O / W emulsion and a method for producing the same, and more particularly to a W / O / W emulsion having good stability over time and a method for producing the same.

[0002] A W / O / W (water-in-oil-in-water) emulsion is a multiphase emulsion in which a water-in-oil (W / O) emulsion is further emulsified and dispersed in an aqueous phase (external aqueous phase). W / O / W emulsions are expected to be used in a variety of applications, including cosmetics, foods, and pharmaceuticals. However, W / O / W emulsions are prone to separation over time, and once separated, they cannot be restored to their original state as a W / O / W emulsion. For this reason, W / O / W emulsions are required to have good stability over time.

[0003] For example, Patent Document 1 describes that the appearance stability of a W / O / W emulsion containing a polyoxyalkylene saturated fatty alcohol ether or the like as an O / W surfactant in the external aqueous phase was evaluated after storage at 40°C for one month.

[0004] Japanese Patent Application Laid-Open No. 2001-179077

[0005] However, the W / O / W emulsion described in Patent Document 1 may be prone to separation (phase separation) under more severe conditions (for example, at a temperature of 50°C), and there is room for improvement in order to further improve the stability over time.

[0006] An object of the present invention is to provide a W / O / W emulsion having good stability over time and a method for producing the same.

[0007] The present inventors have conducted extensive research to obtain a W / O / W emulsion that is stable over time and less susceptible to separation. As a result, they have found that by adding polyoxyethylene sterol ether to a W / O / W emulsion, a W / O / W emulsion that is stable over time can be obtained, and have thus completed the present invention.

[0008] That is, the present invention relates to the following W / O / W type emulsions and methods for producing the same, although the present invention is not limited thereto: [1] A W / O / W type emulsion comprising an internal aqueous phase, an oil phase, and an external aqueous phase, which contains a polyoxyethylene sterol ether. [2] The W / O / W type emulsion according to [1] above, in which the polyoxyethylene sterol ether is solid at 25°C. [3] The W / O / W type emulsion according to [1] or [2] above, in which the oil phase contains a solid oily component. [4] The W / O / W type emulsion according to [3] above, in which the solid oily component is a wax. [5] The W / O / W type emulsion according to any one of [1] to [4] above, which contains at least one lipophilic surfactant selected from the group consisting of a silicone surfactant, a dipolyhydroxy fatty acid ester of polyethylene glycol, and a polyglycerin condensed ricinoleate. [6] The W / O / W emulsion according to [5] above, wherein the polyglycerol condensed ricinoleic acid ester is an ester of condensed ricinoleic acid and polyglycerol having an average degree of glycerol polymerization of 3 to 20. [7] The W / O / W emulsion according to [5] or [6] above, wherein the silicone surfactant is a polyether-modified silicone surfactant having an alkyl group. [8] The W / O / W emulsion according to any one of [1] to [7] above, wherein the external aqueous phase contains a thickener. [9] The W / O / W emulsion according to [8] above, wherein the thickener is at least one selected from the group consisting of alkyl acrylate copolymer, acrylate / alkyl methacrylate copolymer, (sodium acrylate / sodium acryloyldimethyltaurate) copolymer, (acrylates / C10-30 alkyl acrylate) crosspolymer, carboxyvinyl polymer, and xanthan gum.

[10] The W / O / W emulsion according to any one of [1] to [9] above, which contains a polyglycerol condensed ricinoleate.

[11] The W / O / W emulsion according to any one of [1] to

[10] above, which is a skin external preparation.

[12] The W / O / W emulsion according to any one of [1] to

[11] above, which is a cream or a milky lotion.

[13] A method for producing a W / O / W emulsion, comprising the steps of: mixing an inner aqueous phase with an oil phase and emulsifying the mixture to prepare a W / O emulsion; and mixing the prepared W / O emulsion with an outer aqueous phase containing a polyoxyethylene sterol ether and emulsifying the mixture.

[0009] According to the present invention, it is possible to provide a W / O / W emulsion having good stability over time and a method for producing the same. The W / O / W emulsion of the present invention is useful, for example, as an external preparation for skin, such as a cosmetic.

[0010] Embodiments of the present invention are exemplified below. (W / O / W Emulsion) The W / O / W emulsion of the present invention is a W / O / W emulsion containing an internal aqueous phase, an oil phase, and an external aqueous phase. The W / O / W emulsion of the present invention contains polyoxyethylene sterol ether. The W / O / W emulsion of the present invention is typically a W / O / W emulsion containing an internal aqueous phase, an oil phase (W / O emulsion) in which the internal aqueous phase is dispersed (emulsified), and an external aqueous phase in which the oil phase (W / O emulsion) is dispersed (emulsified). The W / O / W emulsion of the present invention may be composed of the internal aqueous phase, oil phase, and external aqueous phase described above. In a W / O / W emulsion, a W / O emulsion in which the internal aqueous phase (internal aqueous phase droplets) is dispersed (emulsified) in the oil phase is dispersed (emulsified) in the external aqueous phase. The W / O / W emulsion of the present invention has good stability over time and is resistant to separation, and is therefore useful in the field of cosmetics and the like.

[0011] As used herein, the terms "internal aqueous phase," "oil phase," and "external aqueous phase" may refer to the respective phases of a W / O / W emulsion, or may refer to the respective solutions containing the components of the respective phases used in producing a W / O / W emulsion. Furthermore, as used herein, "internal aqueous phase components," "oil phase components," and "external aqueous phase components" refer to the components contained in the "internal aqueous phase," "oil phase," and "external aqueous phase" of a W / O / W emulsion, respectively.

[0012] The W / O / W emulsion of the present invention contains a polyoxyethylene sterol ether. In this specification, the term "polyoxyethylene sterol ether" refers to a dehydration condensation reaction product of polyethylene glycol with a compound having a sterol skeleton (a phytosterol skeleton or a cholesterol skeleton) and a hydroxyl group.

[0013] Examples of polyoxyethylene sterol ethers include PEG-5 phytosterol, PEG-10 phytosterol, PEG-20 phytosterol, PEG-30 phytosterol, PEG-25 phytostanol, POE10 cholesteryl ether, POE15 cholesteryl ether, POE20 cholesteryl ether, POE24 cholesteryl ether, and POE30 cholesteryl ether. Among these, polyoxyethylene sterol ethers having a phytosterol skeleton are preferred, with PEG-20 phytosterol, PEG-30 phytosterol, and PEG-25 phytostanol being more preferred, and PEG-25 phytostanol being even more preferred. One type of polyoxyethylene sterol ether may be used alone, or two or more types may be used in combination.

[0014] In the W / O / W emulsion of the present invention, the polyoxyethylene sterol ether is preferably solid at 25° C. This is because the stability of the W / O / W emulsion over time is further improved and separation is less likely to occur.

[0015] In the W / O / W emulsion of the present invention, the polyoxyethylene sterol ether preferably has an average number of moles of ethylene oxide added (average degree of polymerization) in the polyoxyethylene moiety of 3 to 50, more preferably 4 to 40, even more preferably 5 to 35, even more preferably 10 to 30, still more preferably 20 to 30, even more preferably 25 to 30, and particularly preferably 25.

[0016] In the W / O / W emulsion of the present invention, the content of the polyoxyethylene sterol ether in the W / O / W emulsion may be, for example, 0.05 to 15.0% by weight, preferably 0.1 to 10.0% by weight, and more preferably 0.2 to 8.0% by weight.

[0017] Polyoxyethylene sterol ether is a hydrophilic surfactant. Surfactants other than polyoxyethylene sterol ether may be used in the W / O / W emulsion of the present invention, as long as the effects of the present invention are not impaired. For example, conventionally known hydrophilic surfactants other than polyoxyethylene sterol ether may be used as an auxiliary surfactant. In the present invention, a hydrophilic surfactant is a surfactant with an HLB value of greater than 7, preferably an HLB value of 8 or greater, more preferably an HLB value of 9 or greater, and even more preferably an HLB value of 10 or greater. The HLB value of a hydrophilic surfactant is preferably 8 to 20, more preferably 9 to 20, and even more preferably 10 to 19. The HLB value is a measure of the balance between hydrophilicity and lipophilicity. Unless otherwise specified, the HLB value herein refers to the HLB value calculated by the Griffin method. The HLB value may be calculated by the Oda method only when calculation by the Griffin method is not possible. The Oda method is a method described, for example, on page 212 of "Introduction to Surfactants, 2007, Sanyo Chemical Industries, Ltd., authored by Takehiko Fujimoto." When using the Oda method, the HLB value can be calculated by the following formula using the inorganic value and organic value in the table on page 213 of the above-mentioned "Introduction to Surfactants." HLB value = 10 × inorganic / organic

[0018] Examples of hydrophilic surfactants other than polyoxyethylene sterol ether include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, POE20 sorbitan monostearate, POE20 sorbitan monoisostearate, POE20 sorbitan monooleate, etc. These may be used alone or in combination of two or more.

[0019] In the W / O / W emulsion of the present invention, the content of the hydrophilic surfactant may be, for example, 0.05 to 15.0 wt %, preferably 0.1 to 10.0 wt %, and more preferably 0.2 to 8.0 wt %. In the present invention, the content of the polyoxyethylene sterol ether in the hydrophilic surfactant is preferably 90 to 100 wt %, more preferably 95 to 100 wt %, and even more preferably 100 wt %. The W / O / W emulsion of the present invention preferably contains only polyoxyethylene sterol ether as the hydrophilic surfactant.

[0020] In the W / O / W emulsion of the present invention, the polyoxyethylene sterol ether is an O / W surfactant and is usually present at least at the interface between the oil phase and the external aqueous phase. The present invention also includes an embodiment in which the polyoxyethylene sterol ether is contained not only at the interface between the oil phase and the external aqueous phase but also in, for example, the external aqueous phase. In one embodiment, the external aqueous phase may contain the polyoxyethylene sterol ether.

[0021] A lipophilic surfactant can be used in the W / O / W emulsion of the present invention. The lipophilic surfactant is preferably one that is used in W / O surfactants. In the present invention, the lipophilic surfactant is a surfactant with an HLB value of 7 or less. The HLB value of the lipophilic surfactant is preferably 6 or less, more preferably 2.5 to 6, and even more preferably 3 to 5.5. The lipophilic surfactant is not particularly limited, and conventionally known lipophilic surfactants used in the cosmetic field can be used. Examples of the lipophilic surfactant include silicone surfactants (lipophilic silicone surfactants), dipolyhydroxy fatty acid esters of polyethylene glycol, polyglycerin condensed ricinoleic acid esters, monoglycerin monofatty acid esters, monoglycerin difatty acid esters, diglycerin monofatty acid esters, monoglycerin monoalkyl ethers, diglycerin monoalkyl ethers, and sorbitan fatty acid esters. These lipophilic surfactants may be used alone or in combination of two or more.

[0022] The W / O / W emulsion of the present invention preferably contains at least one lipophilic surfactant selected from the group consisting of silicone surfactants, dipolyhydroxy fatty acid esters of polyethylene glycol, and polyglycerol condensed ricinoleate, and more preferably contains a polyglycerol condensed ricinoleate. This is because the stability of the W / O / W emulsion over time is improved. In the present invention, the lipophilic surfactant is preferably at least one selected from the group consisting of silicone surfactants, dipolyhydroxy fatty acid esters of polyethylene glycol, and polyglycerol condensed ricinoleate, and more preferably polyglycerol condensed ricinoleate.

[0023] In this specification, the term "silicone surfactant" refers to a surfactant having a structure in which a hydrophilic substituent is introduced into silicone.The silicone surfactant can be a surfactant suitable for various applications depending on the type of hydrophilic substituent introduced.For example, in the application of external skin preparations such as cosmetics, polyether-modified silicone surfactants in which the substituent is a polyether group, and polyglyceryl-modified silicone surfactants in which the substituent is a polyglyceryl group are preferred, polyether-modified silicone surfactants having an alkyl group, and polyglyceryl-modified silicone surfactants having an alkyl group are more preferred, and polyether-modified silicone surfactants having an alkyl group are even more preferred.

[0024] Examples of polyether-modified silicone surfactants that can be used as lipophilic surfactants include PEG-3 dimethicone, PEG-9 methyl ether dimethicone, polysilicone-13, PEG-9 polydimethylsiloxyethyl dimethicone, PEG / PPG-19 / 19 dimethicone, bis(PEG / PPG-14 / 14) dimethicone, (dimethicone / (PEG-10 / 15)) crosspolymer, cetyl PEG / PPG-10 / 1 dimethicone, lauryl PEG-9 polydimethylsiloxyethyl dimethicone, (PEG-15 / lauryl dimethicone) crosspolymer, and (PEG-15 / lauryl polydimethylsiloxyethyl dimethicone) crosspolymer. Examples of polyether-modified silicone surfactants having an alkyl group that can be used as lipophilic surfactants include cetyl PEG / PPG-10 / 1 dimethicone, lauryl PEG-9 polydimethylsiloxyethyl dimethicone, (PEG-15 / lauryl dimethicone) crosspolymer, and (PEG-15 / lauryl polydimethylsiloxyethyl dimethicone) crosspolymer.

[0025] Examples of polyglyceryl-modified silicone surfactants that can be used as lipophilic surfactants include polyglyceryl-3 polydimethylsiloxyethyl dimethicone, (dimethicone / polyglycerin-3) crosspolymer, isostearyl polyglyceryl-3 dimethicone, lauryl polyglyceryl-3 polydimethylsiloxyethyl dimethicone, (lauryl dimethicone / polyglycerin-3) crosspolymer, etc. Examples of polyglyceryl-modified silicone surfactants having an alkyl group that can be used as lipophilic surfactants include isostearyl polyglyceryl-3 dimethicone, lauryl polyglyceryl-3 polydimethylsiloxyethyl dimethicone, (lauryl dimethicone / polyglycerin-3) crosspolymer, etc.

[0026] Among silicone surfactants, polyether-modified silicone surfactants with an HLB value of 2.5 to 6 (preferably 3 to 5.5) are preferred, and cetyl PEG / PPG-10 / 1 dimethicone and lauryl PEG-9 polydimethylsiloxyethyl dimethicone are more preferred. Among silicone surfactants, cetyl PEG / PPG-10 / 1 dimethicone is even more preferred. One type of silicone surfactant may be used alone, or two or more types may be used in combination.

[0027] When the W / O / W emulsion of the present invention contains a silicone surfactant, the content thereof in the W / O / W emulsion may be, for example, 0.05 to 15.0 wt %, preferably 0.1 to 10.0 wt %, more preferably 0.2 to 8.0 wt %, even more preferably 0.3 to 7.0 wt %, and particularly preferably 0.4 to 5.0 wt %.

[0028] Dipolyhydroxy fatty acid esters of polyethylene glycol are compounds in which polyhydroxy fatty acids are ester-bonded to both ends of polyethylene glycol. Polyhydroxy fatty acids are condensates obtained by condensing the carboxylic acid and hydroxyl groups of hydroxy fatty acids. In the dipolyhydroxy fatty acid esters of polyethylene glycol, the average degree of polymerization of ethylene glycol in the polyethylene glycol moiety is preferably 10 to 50, more preferably 15 to 40, even more preferably 20 to 35, and particularly preferably 30.

[0029] Examples of dipolyhydroxy fatty acid esters of polyethylene glycol include dipoly(12-hydroxystearic acid) esters of polyethylene glycol (preferably PEG-30 dipolyhydroxystearate), dipoly(9,10-dihydroxystearate) esters of polyethylene glycol, and dipolyricinoleic acid esters of polyethylene glycol, with dipoly(12-hydroxystearic acid) esters of polyethylene glycol being preferred. As the dipolyhydroxy fatty acid esters of polyethylene glycol, PEG-30 dipolyhydroxystearate is preferred. One type of dipolyhydroxy fatty acid ester of polyethylene glycol may be used alone, or two or more types may be used in combination.

[0030] When the W / O / W emulsion of the present invention contains a dipolyhydroxy fatty acid ester of polyethylene glycol, the content thereof in the W / O / W emulsion may be, for example, 0.05 to 15.0 wt %, preferably 0.1 to 10.0 wt %, more preferably 0.2 to 8.0 wt %, even more preferably 0.3 to 7.0 wt %, and particularly preferably 0.4 to 5.0 wt %.

[0031] The polyglycerol condensed ricinoleate used in the present invention is a surfactant in which polyricinoleic acid, obtained by condensing ricinoleic acid, is bonded to polyglycerin. In the W / O / W emulsion of the present invention, the polyglycerol condensed ricinoleate ester preferably has an average degree of polymerization of glycerin of 3 to 20, more preferably 4 to 10, even more preferably 5 to 6, and particularly preferably 6. That is, in the W / O / W emulsion of the present invention, the polyglycerol condensed ricinoleate ester is preferably an ester of condensed ricinoleic acid with polyglycerin having an average degree of polymerization of glycerin of 3 to 20, more preferably an ester of condensed ricinoleic acid with polyglycerin having an average degree of polymerization of glycerin of 4 to 10, and even more preferably an ester of condensed ricinoleic acid with polyglycerin having an average degree of polymerization of glycerin of 5 to 6 (particularly preferably 6).

[0032] Examples of polyglycerol condensed ricinoleate esters include polyglyceryl-6 polyricinoleate and polyglyceryl-5 polyricinoleate. As the polyglycerol condensed ricinoleate esters, polyglyceryl-6 polyricinoleate and polyglyceryl-5 polyricinoleate are preferred, with polyglyceryl-6 polyricinoleate being more preferred. One type of polyglycerol condensed ricinoleate may be used alone, or two or more types may be used in combination.

[0033] When the W / O / W emulsion of the present invention contains a polyglycerol condensed ricinoleate, the content thereof in the W / O / W emulsion may be, for example, 0.05 to 15.0% by weight, preferably 0.1 to 10.0% by weight, more preferably 0.2 to 8.0% by weight, even more preferably 0.3 to 7.0% by weight, and particularly preferably 0.4 to 5.0% by weight.

[0034] In one embodiment, the W / O / W emulsion of the present invention more preferably contains at least one lipophilic surfactant selected from the group consisting of alkyl group-containing polyether-modified silicone surfactants, polyethylene glycol dipolyhydroxy fatty acid esters (preferably where the average degree of polymerization of ethylene glycol in the polyethylene glycol moiety is 10 to 50), and polyglycerin condensed ricinoleate esters (preferably where the average degree of polymerization of glycerin is 3 to 20). Also, in one embodiment, the W / O / W emulsion of the present invention preferably contains polyoxyethylene sterol ether and polyglycerin condensed ricinoleate ester, more preferably where the average degree of polymerization of polyoxyethylene sterol ether and glycerin is 3 to 20, and even more preferably where the average degree of polymerization of polyoxyethylene sterol ether and glycerin is 5 to 6 (preferably 6).

[0035] Examples of the monoglycerin mono-fatty acid esters and monoglycerin di-fatty acid esters include mono- or diesters of glycerin with fatty acids having 8 to 22 carbon atoms, and more specific examples include monoglycerin octanoate, monoglycerin 2-ethylhexanoate, monoglycerin decanoate, monoglycerin laurate, monoglycerin myristate, and monoglycerin palmitate.

[0036] Examples of diglycerin monofatty acid esters include monoesters of diglycerin and fatty acids having 8 to 22 carbon atoms, and more specific examples include diglycerin octanoate, diglycerin laurate, diglycerin myristate, and diglycerin palmitate.

[0037] Examples of monoglycerin monoalkyl ethers include ethers of glycerin and alcohols having 8 to 22 carbon atoms, and more specific examples include monoglycerin octyl ether, monoglycerin decyl ether, monoglycerin lauryl ether, monoglycerin myristyl ether, and monoglycerin palmityl ether.

[0038] Examples of diglycerin monoalkyl ethers include ethers of diglycerin and alcohols having 8 to 22 carbon atoms, and more specific examples include diglycerin octyl ether, diglycerin lauryl ether, diglycerin myristyl ether, and diglycerin palmityl ether.

[0039] Examples of sorbitan fatty acid esters include esters of sorbitol and fatty acids having 8 to 22 carbon atoms, and more specific examples include sorbitan octanoate, sorbitan caprylate, sorbitan caprate, sorbitan laurate, sorbitan myristate, and sorbitan palmitate.

[0040] In the W / O / W emulsion of the present invention, the content of the lipophilic surfactant in the W / O / W emulsion may be, for example, 0.05 to 15.0% by weight, preferably 0.1 to 10.0% by weight, more preferably 0.2 to 8.0% by weight, even more preferably 0.3 to 7.0% by weight, and particularly preferably 0.4 to 5.0% by weight.

[0041] In the W / O / W emulsion of the present invention, the lipophilic surfactant is usually present at least at the interface between the internal aqueous phase and the oil phase. The present invention also includes an embodiment in which the lipophilic surfactant is contained not only at the interface between the internal aqueous phase and the oil phase but also at the interface between the oil phase and the external aqueous phase, in the oil phase, etc. In one embodiment of the present invention, the oil phase may contain a lipophilic surfactant. The W / O / W emulsion of the present invention will be further described below.

[0042] (Inner Aqueous Phase Components) In the W / O / W emulsion of the present invention, the inner aqueous phase contains water.

[0043] In the W / O / W emulsion of the present invention, the internal aqueous phase may contain a metal salt. The inclusion of a metal salt as an internal aqueous phase component is preferred because it further improves the stability of the W / O / W emulsion over time. The metal salt is not particularly limited, but magnesium sulfate, sodium citrate, amino acid metal salts such as sodium glutamate, sodium lactate, and sodium chloride are preferred, with magnesium sulfate being more preferred. One type of metal salt may be used alone, or two or more types may be used in combination. When the W / O / W emulsion contains a metal salt, the content thereof is not particularly limited, but may be, for example, 0.001 to 10.0 wt %, preferably 0.01 to 5.0 wt %, and more preferably 0.1 to 2.0 wt % in the W / O / W emulsion.

[0044] In the W / O / W emulsion of the present invention, the internal aqueous phase may contain a water-soluble active ingredient, as long as the effects of the present invention are not impaired.

[0045] (Oil Phase Component) In the W / O / W emulsion of the present invention, the oil phase contains an oil component. As the oil component, a liquid oil component or a solid oil component can be used.

[0046] The solid oil component may be solid at 25°C. "Solid" refers to a component that has no fluidity. The solid oil component also includes a semi-solid oil component. The solid oil component is not particularly limited, but examples thereof include solid fats and oils, waxes, hydrocarbons, higher fatty acids, higher alcohols, esters, silicones, etc. Among these, solid fats and oils and waxes are preferred. Examples of solid fats and oils include cocoa butter, coconut oil, palm oil, palm kernel oil, hydrogenated oil, hydrogenated castor oil, Japan wax, shea butter, etc. Examples of waxes include microcrystalline wax, beeswax, carnauba wax, candelilla wax, lanolin, etc. As the solid oil component, wax is more preferred, and microcrystalline wax is even more preferred. One type of solid oil component may be used alone, or two or more types may be used in combination.

[0047] In the W / O / W emulsion of the present invention, the content of the solid oil component is not particularly limited, but is preferably 0.05 wt% or more, more preferably 0.1 wt% or more, and preferably 5.0 wt% or less, more preferably 3.0 wt% or less, in the W / O / W emulsion. In one embodiment, the content of the solid oil component in the W / O / W emulsion is preferably 0.05 to 5.0 wt%, more preferably 0.1 to 3.0 wt%. In the W / O / W emulsion of the present invention, the content of the solid oil component is not particularly limited, but is preferably 0.5 to 44.0 wt%, more preferably 1.0 to 30.0 wt%, in the oil component (the total amount of the solid oil component and the liquid oil component).

[0048] In the W / O / W emulsion of the present invention, the oil phase preferably contains a solid oil component, more preferably a wax. By containing a solid oil component (more preferably a wax) in the oil phase, the stability of the W / O / W emulsion over time becomes better.

[0049] In the W / O / W emulsion of the present invention, the oil phase usually contains a liquid oil component. The liquid oil component may be liquid at 25° C. Examples of the liquid oil component include natural animal and vegetable oils, hydrocarbon oils, ester oils, silicone oils, higher alcohols, and higher fatty acids.

[0050] Examples of natural animal and vegetable oils include avocado oil, linseed oil, almond oil, olive oil, cacao oil, tung oil, wheat germ oil, sesame oil, rice germ oil, rice bran oil, safflower oil, soybean oil, evening primrose oil, camellia oil, corn oil, rapeseed oil, persic oil, palm oil, palm kernel oil, castor oil, sunflower oil, grape oil, jojoba oil, macadamia nut oil, mink oil, cottonseed oil, coconut oil, peanut oil, and rosehip oil.

[0051] Examples of hydrocarbon oils include α-olefin oligomers, squalane, squalene, and liquid paraffin.

[0052] Examples of ester oils include diisobutyl adipate, 2-hexyldecyl adipate, di-2-heptylundecyl adipate, isostearyl isostearate, trimethylolpropane triisostearate, cetyl 2-ethylhexanoate, neopentyl glycol di-2-ethylhexanoate, trimethylolpropane tri-2-ethylhexanoate, pentaerythritol tetra-2-ethylhexanoate, cetyl octanoate, oleyl oleate, octyldodecyl oleate, decyl oleate, neopentyl glycol dicaprate, ethanol, 2-ethylhexyl succinate, isocetyl stearate, butyl stearate, diisopropyl sebacate, cetyl lactate, tetradecyl lactate, isopropyl myristate, octyldodecyl myristate, cetyl myristate, myristyl myristate, octyl palmitate, 2-ethylhexyl palmitate, 2-hexyldecyl palmitate, 2-heptylundecyl palmitate, phytosteryl oleate, diisostearyl malate, para-methoxycinnamate, pentaerythrityl tetrarosinate, and the like.

[0053] Examples of silicone oils include dimethylpolysiloxane, highly polymerized methylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, octamethylcyclotetrasiloxane, octamethylcyclopentasiloxane, decamethylcyclohexasiloxane, higher alkoxy-modified silicones such as stearoxysilicone, alkyl-modified silicones, and higher fatty acid ester-modified silicones.

[0054] Examples of higher alcohols include octyldodecanol, isostearyl alcohol, and oleyl alcohol.

[0055] Examples of higher fatty acids include isostearic acid, oleic acid, linoleic acid, and linolenic acid.

[0056] As the liquid oil component, hydrocarbon oils and ester oils are preferred, and squalane and 2-ethylhexanoate cetyl are more preferred. The liquid oil component may be used alone or in combination of two or more.

[0057] In the W / O / W emulsion of the present invention, the content of the liquid oil component is not particularly limited, but is preferably 0.5 wt% or more, more preferably 2.0 wt% or more, and preferably 40.0 wt% or less, more preferably 25.0 wt% or less, in the W / O / W emulsion. In one embodiment, the content of the liquid oil component in the W / O / W emulsion is preferably 0.5 to 40.0 wt%, more preferably 2.0 to 25.0 wt%. In the W / O / W emulsion of the present invention, the content of the liquid oil component is not particularly limited, but is preferably 56.0 to 99.5 wt%, more preferably 70.0 to 99.0 wt%, in the oil component (the total amount of the solid oil component and the liquid oil component).

[0058] In the W / O / W emulsion of the present invention, the oil phase may optionally contain an oil-soluble active ingredient within a range that does not impair the effects of the present invention. The type of oil-soluble active ingredient is not particularly limited. By further containing an oil-soluble active ingredient, cosmetics and the like having functions derived from the oil-soluble active ingredient can be produced.

[0059] (External Aqueous Phase Components) In the W / O / W emulsion of the present invention, the external aqueous phase contains water.

[0060] In the W / O / W emulsion of the present invention, the external aqueous phase preferably contains a thickener. When the external aqueous phase contains a thickener, the stability of the W / O / W emulsion over time is further improved. A water-soluble polymer can be used as the thickener. The water-soluble polymer increases the viscosity of the external aqueous phase and reduces the fluidity of the W / O emulsion, and is therefore effective in preventing aggregation of W / O emulsions.

[0061] The thickener is not particularly limited, and known water-soluble polymers can be used, including natural water-soluble polymers, semi-synthetic water-soluble polymers, and synthetic water-soluble polymers. Examples of natural water-soluble polymers include plant-based polymers such as gum arabic, guar gum, carrageenan, pectin, agar, quince seed, and starch (rice, corn, potato, and wheat); microbial polymers such as xanthan gum, dextran, and pullulan; and animal-based polymers such as collagen, casein, albumin, and gelatin. Examples of semi-synthetic water-soluble polymers include starch-based polymers such as carboxymethyl starch and methylhydroxypropyl starch; cellulose-based polymers such as methylcellulose, nitrocellulose, ethylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, sodium carboxymethylcellulose (CMC), crystalline cellulose, and cellulose powder; and alginic acid-based polymers such as sodium alginate and propylene glycol alginate. Examples of synthetic water-soluble polymers include vinyl polymers such as polyvinyl alcohol, polyvinyl methyl ether, and carboxyvinyl polymer (carbomer); copolymer polymers such as polyoxyethylene polyoxypropylene copolymer; acrylic polymers such as sodium polyacrylate, polyacrylamide, alkyl acrylate copolymer, alkyl acrylate methacrylate copolymer (acrylic acid / alkyl methacrylate copolymer), (sodium acrylate / sodium acryloyldimethyltaurate) copolymer, and (acrylates / alkyl acrylate (C10-30)) crosspolymer; polyethyleneimine, cationic polymers, etc. One type of thickener may be used alone, or two or more types may be used in combination.The thickener is preferably at least one selected from the group consisting of alkyl acrylate copolymer, alkyl acrylate methacrylate copolymer, (sodium acrylate / sodium acryloyldimethyltaurate) copolymer, (acrylates / C10-30 alkyl acrylate) crosspolymer, carboxyvinyl polymer, and xanthan gum, and more preferably (sodium acrylate / sodium acryloyldimethyltaurate) copolymer or (acrylates / C10-30 alkyl acrylate) crosspolymer.

[0062] In the W / O / W emulsion of the present invention, when the external aqueous phase contains a thickener, the content thereof in the W / O / W emulsion is, for example, 0.001 to 10.0% by weight, preferably 0.005 to 5.0% by weight, and more preferably 0.01 to 2.0% by weight.

[0063] (Others) In addition to the above-mentioned components, the W / O / W emulsion of the present invention may contain, as appropriate, various optional components used in ordinary cosmetics, quasi-drugs, pharmaceuticals, and fragrances, such as moisturizers, active ingredients, preservatives, pigments, powders, pH adjusters, UV absorbers, antioxidants, and fragrances. Examples of moisturizers include glycerin, 1,3-butylene glycol (BG), and dipropylene glycol (DPG). Examples of pH adjusters include triethanolamine (TEA). Examples of preservatives include phenoxyethanol and ethanol. These optional components may be used alone or in combination of two or more.

[0064] The content of each component relative to the total amount of the W / O / W emulsion of the present invention can be determined appropriately depending on the active ingredient, the type of surfactant, the type and amount of the solid oil component, etc.

[0065] In the W / O / W emulsion of the present invention, the weight ratio of the oil phase to the internal aqueous phase (internal aqueous phase / oil phase) is not particularly limited, but from the viewpoint of the stability over time of the W / O / W emulsion, it is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, and even more preferably 25 / 75 to 75 / 25. Furthermore, per 100 parts by weight of the internal aqueous phase, the oil phase is preferably 10 to 500 parts by weight, more preferably 20 to 300 parts by weight, and even more preferably 50 to 200 parts by weight, and the external aqueous phase is preferably 50 to 2000 parts by weight, more preferably 100 to 1500 parts by weight, and even more preferably 200 to 1000 parts by weight.

[0066] The form of the W / O / W emulsion of the present invention is not particularly limited as long as it has stability over time. The average particle size of the inner aqueous phase droplets dispersed in the oil phase may be, for example, 0.001 to 100 μm, preferably 0.01 to 100 μm, and more preferably 0.1 to 100 μm. The average particle size of the W / O emulsion dispersed in the outer aqueous phase may be, for example, 0.01 to 100 μm, preferably 0.1 to 100 μm, more preferably 0.5 to 100 μm, and even more preferably 1 to 50 μm.

[0067] The viscosity of the W / O / W emulsion of the present invention is not particularly limited, but is preferably 500 to 50,000 mPa s, more preferably 1,000 to 40,000 mPa s, and even more preferably 2,000 to 30,000 mPa s at 25° C. In this specification, the viscosity of the W / O / W emulsion is the viscosity measured using a BM-type viscometer (manufactured by TOKI SANGYO Corporation, measurement conditions: rotor No. 4, 12 rpm, 1 minute).

[0068] The W / O / W emulsion of the present invention can be used in various applications to which a W / O / W emulsion can be applied. In one embodiment, the W / O / W emulsion of the present invention can be used as an external preparation (external composition). In another embodiment, the W / O / W emulsion of the present invention can be used as an oral composition (e.g., food and beverage products, oral pharmaceuticals, oral quasi-drugs, etc.). In another embodiment, the W / O / W emulsion of the present invention can be suitably used as an external preparation.

[0069] External preparations are those that can be applied to body surfaces such as the skin and mucous membranes, and examples thereof include cosmetics, external quasi-drugs, external medicines, cleansers, cosmetics, etc. As external preparations, for example, external preparations for skin are preferred.

[0070] The W / O / W emulsion of the present invention can be suitably used, for example, as a topical skin preparation. The term "topical skin preparation" as used herein refers to a dosage form that can be administered to the skin, and is a general term for cosmetics such as creams, serums, emulsions, lotions, and face packs, as well as quasi-drugs, pharmaceuticals, cleansers, and cosmetic products. The form of the topical skin preparation is not particularly limited, but a cream or emulsion is preferred. When the W / O / W emulsion of the present invention is used as a topical skin preparation, its use is not particularly limited as long as it is a known use for which emulsions can be used, but cosmetics are preferred, and among these, creams and emulsions are particularly preferred.

[0071] (Method for producing W / O / W emulsion) The method for producing a W / O / W emulsion of the present invention (hereinafter also simply referred to as the production method of the present invention in this specification) comprises the steps of mixing and emulsifying an internal aqueous phase and an oil phase to prepare a W / O emulsion, and mixing and emulsifying the prepared W / O emulsion with an external aqueous phase. In the production method of the present invention, the external aqueous phase contains polyoxyethylene sterol ether. The production method of the present invention allows for the production of a W / O / W emulsion of the present invention, which has excellent stability over time.

[0072] In the production method of the present invention, the internal aqueous phase, oil phase, components of these phases, preferred embodiments thereof, optional embodiments, etc. are the same as those of the above-mentioned W / O / W emulsion of the present invention.

[0073] In the production method of the present invention, the oil phase preferably contains the above-mentioned lipophilic surfactant. The lipophilic surfactant and its preferred embodiments are the same as those in the W / O / W emulsion of the present invention. The oil phase preferably contains at least one lipophilic surfactant selected from the group consisting of the above-mentioned silicone surfactants, dipolyhydroxy fatty acid esters of polyethylene glycol, and polyglycerin condensed ricinoleic acid esters, and more preferably contains at least one lipophilic surfactant selected from the group consisting of polyether-modified silicone surfactants having alkyl groups, dipolyhydroxy fatty acid esters of polyethylene glycol (preferably, the average degree of polymerization of ethylene glycol in the polyethylene glycol moiety is 10 to 50), and polyglycerin condensed ricinoleic acid esters (preferably, the average degree of polymerization of glycerin is 3 to 20).

[0074] In the production method of the present invention, the external aqueous phase contains a polyoxyethylene sterol ether. The external aqueous phase, its components, and preferred embodiments thereof are the same as those of the external aqueous phase in the W / O / W emulsion of the present invention described above. The preferred embodiment of the polyoxyethylene sterol ether is the same as that of the W / O / W emulsion of the present invention.

[0075] Specifically, in the production method of the present invention, an inner aqueous phase is first added to an oil phase, and the mixture is emulsified at an emulsification temperature of preferably 50 to 100°C to prepare a W / O emulsion. The weight ratio of the inner aqueous phase to the oil phase (inner aqueous phase / oil phase) is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, and even more preferably 25 / 75 to 75 / 25. In one embodiment, the weight ratio of the inner aqueous phase, oil phase, and outer aqueous phase is preferably 10 to 500 parts by weight, more preferably 20 to 300 parts by weight, and even more preferably 50 to 200 parts by weight of the oil phase, and preferably 50 to 2000 parts by weight, more preferably 100 to 1500 parts by weight, and even more preferably 200 to 1000 parts by weight of the outer aqueous phase, per 100 parts by weight of the inner aqueous phase.

[0076] Next, the W / O emulsion is added to the external aqueous phase and emulsified. This allows the W / O / W emulsion of the present invention to be prepared. In the production method of the present invention, it is preferable to blend each component so that the content of each component in the resulting W / O / W emulsion falls within the above-mentioned range.

[0077] In this specification, a numerical range expressed by a lower limit and an upper limit, i.e., "lower limit to upper limit," includes the lower limit and the upper limit. For example, a range expressed by "1 to 2" means 1 or more and 2 or less, including 1 and 2. In this specification, the upper limit and the lower limit may be any combination of ranges.

[0078] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0079] 1. Raw Materials The following raw materials were used in the following Examples and Comparative Examples: Purified water was used as water. (Oil phase) Microcrystalline wax (manufactured by Nikko Rica Corporation) Polyglyceryl-6 polyricinoleate (manufactured by Sakamoto Pharmaceutical Co., Ltd., Sy Glystar CRS-75, HLB value: 3.3) Polyglyceryl-5 polyricinoleate (manufactured by Taiyo Kagaku Co., Ltd., Sunsoft No. 818R-C) Cetyl PEG / PPG-10 / 1 dimethicone (manufactured by Evonik Operations GmbH, ABIL EM 90, HLB value: 5.0) PEG-30 dipolyhydroxystearate (manufactured by Croda Japan Co., Ltd., Cisrol DPHS, HLB value: 5.0) (External aqueous phase) PEG-30 phytosterol (manufactured by Nikko Chemicals Co., Ltd., NIKKOL BPS-30, HLB value: 18.0, solid at 25°C) PEG-25 phytostanol (NIKKOL BPSH-25, manufactured by Nikko Chemicals Co., Ltd., HLB value: 14.5, solid at 25°C) POE20 cholesteryl ether (EMALEX CS-20, manufactured by Nippon Emulsion Co., Ltd., HLB value: 12.0, solid at 25°C) Polyglyceryl-10 oleate (SUNSOL Q-17S-C, manufactured by Taiyo Kagaku Co., Ltd., HLB value: 15.0) Polyglyceryl-10 stearate (SUNSOL Q-18Y-C, manufactured by Taiyo Kagaku Co., Ltd., HLB value: 17.5) Polyglyceryl-5 stearate (SUNSOL A-181E-C, HLB value: 12.9) PEG-20 glyceryl isostearate (EMALEX, manufactured by Nippon Emulsion Co., Ltd.) GWIS-120, HLB value: 13) Disodium stearoyl glutamate (Amisoft (registered trademark) HS-21P, manufactured by Ajinomoto Co., Inc.) Sodium dioleth-8-phosphate (diPOE(8) oleyl ether sodium phosphate, Nikko Chemicals Co., Ltd., NIKKOL DOP-8NV) POE20 sorbitan trioleate (NIKKOL TO-30V, manufactured by Nikko Chemicals Co., Ltd., HLB value: 11.0) POE20 sorbitan tristearate (NIKKOL TS-30V, manufactured by Nikko Chemicals Co., Ltd., HLB value: 10.5) POE6 sorbitan monostearate (NIKKOL TS-106V, manufactured by Nikko Chemicals Co., Ltd., HLB value: 9.5)POE6 sorbitan monooleate (Kao Corporation, Rheodol TW-O106V, HLB value: 10) Sorbitan trioleate (Nikko Chemicals Co., Ltd., NIKKOL SO-30V, HLB value: 1.7) (Acrylates / C10-30 alkyl acrylate) crosspolymer (Lubrizol Japan Corporation, PEMULEN TR-1) (Sodium acrylate / Sodium acryloyldimethyltaurate) copolymer (Seiwa Kasei Co., Ltd., SIMULGEL EG QD) The HLB values ​​listed here are catalog values ​​provided by the manufacturers.

[0080] 2. Preparation of W / O / W Emulsions (Examples 1 to 23) The components were mixed in the proportions (wt %) shown in Table 1 to prepare an oil phase, an inner aqueous phase, and an outer aqueous phase. Next, the inner aqueous phase was added to the oil phase at a temperature of 80°C and emulsified to prepare a W / O emulsion. The W / O emulsion was then added to the outer aqueous phase to obtain the W / O / W emulsions (W / O / W emulsion preparations) of Examples 1 to 23. More specifically, the W / O emulsion and the outer aqueous phase were mixed and emulsified to obtain the W / O / W emulsions. The obtained W / O / W emulsions were observed with an optical microscope, and it was confirmed that W / O / W emulsions consisting of an inner aqueous phase, an oil phase, and an outer aqueous phase had been prepared. Visual inspection of the appearance of the obtained W / O / W emulsions revealed that they were milky.

[0081] The values ​​in Tables 1 and 2 are the amounts (wt%) of each component in the W / O / W emulsion (100 wt%). In Tables 1 and 2, the amount of water contained in the external aqueous phase is listed as "balance," which means that water was added so that the total amount of water contained in the external aqueous phase and all other components (total amount of W / O / W emulsion) was 100 wt%.

[0082] (Comparative Examples 1 to 22) W / O / W emulsions (W / O / W emulsion preparations) were prepared in the same manner as in Example 1, except that the compositions of the components were as shown in Table 2. The resulting W / O / W emulsions were observed under an optical microscope to confirm whether W / O / W emulsions consisting of an inner aqueous phase, an oil phase, and an outer aqueous phase had been prepared. In Comparative Examples 2 to 6, 13 to 17, and 19 to 22, no W / O / W emulsions were prepared. In Comparative Examples 1, 7 to 12, and 18, W / O / W emulsions were prepared, and the appearance (visual inspection) of the resulting W / O / W emulsions was milky.

[0083] 3. Evaluation of W / O / W Emulsions The temporal stability of the W / O / W emulsions prepared in the above Examples and Comparative Examples was evaluated. The prepared W / O / W emulsion preparations were stored for one month under accelerated conditions at 50°C. After storage, the W / O / W emulsion preparations were visually inspected for the presence or absence of separation and for their glossy appearance, and were evaluated according to the following criteria. The results are shown in Tables 1 and 2. A glossy appearance indicates that the W / O / W emulsion is uniform. Note that the temporal stability of Comparative Examples 2 to 6, 13 to 17, and 19 to 22, which did not become W / O / W emulsions immediately after preparation, was not evaluated. (Evaluation criteria) ⊚: No separation was observed, and the appearance was glossy. ×: Separation was observed

[0084]

[0085]

[0086] In Tables 1 and 2, BG stands for 1,3-butylene glycol, DPG stands for dipropylene glycol, and TEA stands for triethanolamine.

[0087] 4. Discussion The W / O / W emulsions of Comparative Examples 1, 7 to 12, and 18 exhibited insufficient stability over time, with separation observed after one month of storage. On the other hand, the W / O / W emulsions of the present invention of Examples 1 to 23 exhibited good stability over time, with no separation observed even after one month of storage.

[0088] According to the present invention, it is possible to provide a W / O / W emulsion having good stability over time and a method for producing the same.

Claims

1. A W / O / W emulsion comprising an internal aqueous phase, an oil phase, and an external aqueous phase, the W / O / W emulsion containing a polyoxyethylene sterol ether.

2. The W / O / W emulsion according to claim 1, wherein the polyoxyethylene sterol ether is solid at 25°C.

3. A W / O / W emulsion according to claim 1 or 2, wherein the oil phase contains a solid oily component.

4. A W / O / W emulsion according to claim 3, wherein the solid oily component is a wax.

5. A W / O / W type emulsion according to claim 1 or 2, which contains at least one lipophilic surfactant selected from the group consisting of silicone surfactants, dipolyhydroxy fatty acid esters of polyethylene glycol, and polyglycerin condensed ricinoleic acid esters.

6. A W / O / W emulsion according to claim 5, wherein the polyglycerol condensed ricinoleic acid ester is an ester of polyglycerol having an average degree of glycerol polymerization of 3 to 20 and condensed ricinoleic acid.

7. The W / O / W emulsion according to claim 5, wherein the silicone surfactant is a polyether-modified silicone surfactant having an alkyl group.

8. A W / O / W emulsion according to claim 1 or 2, wherein the external aqueous phase contains a thickener.

9. The W / O / W emulsion according to claim 8, wherein the thickener is at least one selected from the group consisting of alkyl acrylate copolymer, alkyl acrylate / methacrylate copolymer, sodium acrylate / sodium acryloyldimethyltaurate copolymer, acrylates / C10-30 alkyl acrylate crosspolymer, carboxyvinyl polymer, and xanthan gum.

10. The W / O / W emulsion according to claim 5, which contains a polyglycerin condensed ricinoleate.

11. The W / O / W emulsion according to claim 1 or 2, which is an external preparation for the skin.

12. The W / O / W emulsion according to claim 1 or 2, which is a cream or a milky lotion.

13. A method for producing a W / O / W emulsion, comprising the steps of: preparing a W / O emulsion by mixing and emulsifying an inner aqueous phase and an oil phase; and mixing and emulsifying the prepared W / O emulsion with an outer aqueous phase containing a polyoxyethylene sterol ether.

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