JP-7857193-B2 - Oil-in-water emulsion composition

Inventors

• 古勢 美緒
• 寺西 諒真
• 忍田 亜希子
• 力丸 あゆみ
• 井岡 千紘
• 山崎 貴史
• 辻 俊一

Assignees

• 株式会社ファンケル
• キリンホールディングス株式会社

Dates

Publication Date

20260512

Application Date

20220905

Claims (6)

1. Oil-in-water emulsion composition comprising the components (a) and (b) below; (a) Particles comprising a polymer having a hydrophobic portion having a cationic group containing hydrophobic monomer units, and a hydrophilic portion containing at least a hydrophilic monomer unit represented by the following formula (I), (b) Hydrophobized fine metal oxide particles.
2. The oil-in-water emulsion composition according to claim 1, wherein the content of the hydrophobized fine metal oxide particles in the oil-in-water emulsion composition is 1% by mass or more and 30% by mass or less.
3. 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 .
4. The oil-in-water emulsion composition according to claim 1 or 2, wherein the cationic group is derived from a cationic radical polymerization initiator.
5. 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 4, 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).
6. 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.

Description

This invention relates to an oil-in-water emulsion composition having excellent usability. Generally, sunscreen cosmetics contain fine metal oxide powders to achieve a high SPF (Sun Protection Factor). It is widely known that these fine metal oxide particles have a strong UV-blocking effect. Because the amount of fine metal oxide particles (e.g., titanium dioxide, zinc oxide, cerium oxide) used in sunscreen cosmetics tends to be relatively large, two or more types of fine metal oxide particles are sometimes used in combination, such as titanium dioxide and zinc oxide, or, depending on the product, organic UV absorbers may also be used. When incorporating such fine metal oxide particles into sunscreen cosmetics in the form of oil-in-water emulsions, hydrophobized fine metal oxide particles are often used to improve dispersibility in the oil phase. Simultaneously, attempts have been made to enhance the dispersibility of these hydrophobized fine metal oxide particles using surfactants. However, using large amounts of surfactants in oil-in-water emulsions can cause problems such as stickiness and irritation when applied directly to the skin or other parts of the body. Furthermore, many consumers are concerned about the effects of surfactants that can be absorbed by the body. Therefore, it is desirable to minimize the amount of surfactants used in oil-in-water emulsions used as sunscreen cosmetics. 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 the development of oil-in-water emulsion compositions emulsified by placing solid particles near the interface between the oil and aqueous phases. 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 and aqueous phases. While the present invention is not bound by any theory, generally, oil-in-water emulsion compositions emulsified by solid particles are 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, stabilizing the structure of the droplets. As mentioned above, there has been a certain degree of demand for emulsified compositions that do not use surfactants. An example of an oil-in-water emulsion composition used as a sunscreen cosmetic that substantially does not contain surfactants as emulsifiers is disclosed in Patent Document 1, for example, an oil-in-water emulsion composition characterized by containing light-shielding powder and being stabilized by an emulsion powder with a charged surface. According to the oil-in-water emulsion composition described in Patent Document 1, it exhibits excellent resistance to aqueous solutions containing ions, and its light-shielding effect is maintained or improved after contact with such aqueous solutions. Japanese Patent Publication No. 2020-50627 This is a schematic comparison diagram of emulsions using surfactants and emulsions using solid particles.This graph shows the SPF for experimental examples 1 to 3 and comparative experimental examples 1 to 3.This graph shows the comparison results of water resistance in Experimental Example 1 and Comparative Experimental Example 2. The embodiments for carrying out the present invention will be described in detail below 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. <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, and (b) hydrophobically treated fine metal oxide particles. The oil-in-water emulsion composition of this embodiment is excellent in terms of feel and emulsification stability, and can be used as a general-purpose sunscreen cosmetic, and also has excellent UV shielding effect due to the sufficient dispersion of hydrophobically treated fine metal oxide particles. Furthermore, the oil-in-water emulsion composition of this embodiment has excellent water resistance of the film formed thereon, and it is easy to maintain a high SPF even after a water bath. In addition, from the viewpoint of having a good feel after application, it is preferable that the oil-in-water emulsion composition of this embodiment substantially does not contain surfactants as emulsifiers. In particular, since sunscreen cosmetics tend to be applied to a wi