JP7757764B2 - Oil-in-water emulsion composition - Google Patents

Description

The present invention relates to an oil-in-water emulsion composition, specifically an oil-in-water emulsion composition that combines a rich, full-bodied texture with good spreadability when applied, and that has a smooth, non-sticky feel even when in contact with water after application.

Oil-in-water emulsion compositions are widely used in skin care products, hair cosmetics, and other products for the purpose of moisturizing the skin. In general, it is important for emulsion cosmetics to have a feel that consumers find appealing when using them. A preferred feel is, for example, a high level of moisturizing, and a rich, full-bodied texture that is easy to sense is desired. Known methods for creating a rich feel include adding a thickener to increase viscosity and using solid oils and fats as oil-based ingredients. However, adding solid oils and fats can sometimes worsen the spreadability of the emulsion composition when spread and the stickiness after application, and various technologies have been developed to address these issues.

For example, Patent Document 1 discloses an emulsion composition that combines solid hydrocarbon oils, waxes, polyoxyethylene cetyl ether, and cationic polymers to achieve excellent spreadability on the skin, reduced stickiness after application, and excellent moisturizing effects.

Patent Document 2 also discloses an oil-in-water emulsion cosmetic that contains an acylamino acid salt, a paste or solid oil, a liquid oil, a polyalkylene glycol, and a polysaccharide, and has a mass ratio of (paste or solid oil)/liquid oil of 0.35 or more and 1.0 or less. It is reported that this cosmetic combines a rich, heavy texture with good spreadability, blends well with the skin, and reduces stickiness after application.

However, in the high humidity of summer or in sweaty conditions, the applied emulsion composition may re-emulsify when mixed with sweat or moisture. Conventional technologies have had the problem of becoming sticky in such cases. Therefore, there has been a demand for an emulsion composition that is less likely to become sticky even when it comes into contact with moisture again after application, and that has a smooth, powdery feel.

JP 2011-102258 A JP 2018-16583 A

The object of the present invention is to provide an oil-in-water emulsion composition that combines a rich, full-bodied texture with good spreadability when applied, and that has a smooth, non-sticky feel even when it comes into contact with water again after application.

As a result of extensive research, the present inventors have found that the above-mentioned object can be achieved by an oil-in-water emulsion composition containing the following components (A) and (B) in predetermined amounts. Based on this finding, the present invention is as follows.
[1] The following components (A) and (B):
(A) The following formula (1):
RO-(AO) _a -[(PO) _b /(EO) _c ]-H...(1)
(In the formula,
R is a linear or branched alkyl group having 12 to 36 carbon atoms;
AO is an oxyalkylene group having 3 or 4 carbon atoms;
PO is an oxypropylene group;
EO is an oxyethylene group;
[(PO) _b /(EO) _c ] is a polyoxyalkylene group formed by randomly bonding PO and EO, and a, b, and c are the average number of moles of AO, PO, and EO added per molecule, respectively, and are within the ranges of 1≦a≦40, 1≦b≦40, 1≦c≦80, 20≦(a+b+c), and 0.1≦(b+c)/(a+b+c)<1.
and (B) a fatty acid ester wax having a melting point of 40 to 110°C, the fatty acid ester wax being composed of an alcohol having 1 to 6 hydroxyl groups and a fatty acid having 16 to 22 carbon atoms, and water, wherein the content of component (A) is 0.1 to 10% by mass and the content of component (B) is 0.2 to 15% by mass based on the total mass of the composition.

The oil-in-water emulsion composition of the present invention combines a rich, full-bodied texture with good spreadability when applied, and provides a smooth, non-sticky feel even when in contact with water after application.

Hereinafter, an embodiment of the present invention will be described.
In this specification, numerical ranges defined using the symbol "to" are intended to include the numerical values at both ends (upper and lower limits) of the symbol "to." For example, "2 to 5" means 2 or more and 5 or less.

The oil-in-water emulsion composition of the present invention (hereinafter sometimes abbreviated as "the composition of the present invention") contains components (A) and (B) and water. Below, we will explain each component in turn, starting with component (A).

[Component (A)]
The component (A) used in the present invention is a compound represented by the formula (1):
RO-(AO) _a -[(PO) _b /(EO) _c ]-H...(1)
The component (A) may be used alone or in combination of two or more.

In formula (1), R represents a linear or branched alkyl group having 12 to 36 carbon atoms. If R has fewer than 12 carbon atoms, the stability of the composition of the present invention may decrease. The number of carbon atoms in R is preferably 18 or more, and more preferably 20 or more. If R has more than 36 carbon atoms, the spreadability of the composition of the present invention may be impaired. The number of carbon atoms in R is preferably 32 or less, and more preferably 26 or less.

Component (A) is typically produced using an alcohol, and R in formula (1) is derived from the alcohol (ROH) used in the production of component (A). Such alcohols are linear or branched alcohols having 12 to 36 carbon atoms.

Examples of the alcohol (ROH) include linear alcohols such as dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, eicosanol, docosanol, tetracosanol, hexacosanol, octacosanol, triacosanol, and hexatriacosanol; and branched alcohols such as isotridecanol, 1-methylheptadecanol, 2-octyldecanol, 2-decyltetradecanol, 2-tetradecyloctadecanol, and 2-hexadecyleicosanol. One or more of these alcohols can be used when producing component (A). Among these alcohols, branched alcohols are preferred from the viewpoints of the good spreadability of the composition of the present invention upon application and the non-sticky feel after application, and isotridecanol, 1-methylheptadecanol, 2-octyldecanol, and 2-decyltetradecanol are more preferred.

In formula (1), AO is an oxyalkylene group having 3 or 4 carbon atoms, PO is an oxypropylene group, and EO is an oxyethylene group. Examples of AO include an oxypropylene group and an oxybutylene group. When a is 2 or more, the two or more AOs may be the same or different groups. When there are two or more types of AO, (AO) _a may be added in a random manner or in a block manner. AO is preferably an oxypropylene group.

In formula (1), a, b, and c are the average number of moles of AO, PO, and EO added per molecule, respectively.
a is a number from 1 to 40. The upper limit of a is preferably 30, more preferably 20, and even more preferably 9. The lower limit of a is preferably 2, more preferably 3, and even more preferably 4. If a is too small or too large, the stability and non-sticky feel of the composition of the present invention may be impaired.

b is a number from 1 to 40. The upper limit of b is preferably 30, more preferably 20, and even more preferably 10. The lower limit of b is preferably 2, more preferably 3, and even more preferably 4. If b is too small or too large, the stability and non-sticky feel of the composition of the present invention may be impaired.

c is a number from 1 to 80. The upper limit of c is preferably 60, more preferably 40, and even more preferably 30. The lower limit of c is preferably 5, more preferably 10, and even more preferably 20. If c is too small or too large, the composition of the present invention may become sticky after application.

The sum of a, b, and c (a+b+c) is 20 or more, preferably 30 or more, and more preferably 35 or more. If (a+b+c) is too small, the stability of the composition of the present invention may decrease. Furthermore, from the viewpoint of the stability of the composition of the present invention, (a+b+c) is preferably 100 or less, more preferably 80 or less, even more preferably 50 or less, and particularly preferably 40 or less.

In formula (1), [(PO) _b /(EO) _c ] represents a polyoxyalkylene group in which PO and EO are bonded randomly rather than in a block configuration. If EO and PO are bonded in a block configuration, the spreadability of the composition of the present invention may be poor when applied, or stickiness may occur after application.

Furthermore, when the number of carbon atoms in R is n, from the viewpoint of the stability of the composition of the present invention, preferably 30≦(2n+a)≦100, more preferably 30≦(2n+a)≦80, even more preferably 35≦(2n+a)≦80, and particularly preferably 40≦(2n+a)≦60.

For component (A), the ratio is 0.1≦(b+c)/(a+b+c)<1, preferably 0.3≦(b+c)/(a+b+c)≦0.97, more preferably 0.5≦(b+c)/(a+b+c)≦0.9, even more preferably 0.6≦(b+c)/(a+b+c)≦0.85, and particularly preferably 0.7≦(b+c)/(a+b+c)≦0.8. If (b+c)/(a+b+c) is too small, the composition of the present invention may not spread well when applied or may become sticky after application.

Component (A) can be produced by known methods. For example, component (A) can be obtained by addition polymerizing an alkylene oxide with a linear or branched alkyl alcohol having 12 to 36 carbon atoms in the presence of an alkali catalyst at 50 to 160°C and 0.5 MPa (gauge pressure) or less, followed by addition polymerizing a mixture of ethylene oxide and propylene oxide, neutralizing the mixture with an acid such as hydrochloric acid, phosphoric acid, or acetic acid, and then removing the water and neutralization salt.

The content of component (A) is 0.1 to 10% by mass, based on the total amount of the composition of the present invention. If the content of component (A) is too low, the stability of the composition of the present invention will be poor, and if it is too high, the composition of the present invention may become sticky after application. From this perspective, the content of component (A) is preferably 0.2 to 7% by mass, and more preferably 0.5 to 5% by mass, based on the total amount of the composition of the present invention.

[Component (B)]
Component (B) used in the present invention is a fatty acid ester wax having a melting point of 40 to 110° C., which is a fatty acid ester wax of an alcohol having 1 to 6 hydroxyl groups and a fatty acid having 16 to 22 carbon atoms. Component (B) may be used alone or in combination of two or more types.

The melting point of component (B) is 40 to 110°C, preferably 60 to 100°C, and more preferably 70 to 95°C. If the melting point of component (B) is excessively low, the stability of the composition of the present invention may decrease, and it may feel sticky to the touch. If the melting point of component (B) is excessively high, the stability of the composition of the present invention may decrease, and its rich texture may be impaired.

The alcohol constituting component (B) is an alcohol having 1 to 6 hydroxyl groups. Examples of such alcohols include monohydric higher alcohols such as lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, isostearyl alcohol, and behenyl alcohol; dihydric alcohols such as ethylene glycol and propylene glycol; trihydric alcohols such as glycerin, pentanetriol, and trimethylolpropane; tetrahydric alcohols such as pentaerythritol and hexanetetrol; pentahydric alcohols such as glucose; and hexahydric alcohols such as sorbitol, sorbitan, mannitol, and dipentaerythritol. Of these, polyhydric alcohols are preferred, and polyhydric alcohols having 3 to 6 hydroxyl groups are more preferred.

The fatty acids that make up component (B) are fatty acids having 16 to 22 carbon atoms. Examples of such fatty acids include palmitic acid, palmitoleic acid, stearic acid, oleic acid, isostearic acid, linoleic acid, ricinoleic acid and their hydrogenated derivatives, arachidic acid, and behenic acid.

Examples of component (B) include stearyl stearate, behenyl behenate, pentaerythritol tetrabehenate, pentaerythritol tetrastearate, hexaglycerin octabehenate, and hydrogenated castor oil. Of these, hydrogenated castor oil, pentaerythritol tetrabehenate, and stearyl stearate are preferred, with hydrogenated castor oil and pentaerythritol tetrabehenate being more preferred.

The area of component (B) contained within a range of 7°C lower and 3°C higher than the maximum peak temperature in the differential thermal curve, totaling 10°C, is preferably 80% or more of the total peak area, and more preferably 90% or more of the total peak area. Use of such component (B) makes the feel of the composition of the present invention after application even more pleasant.

The "maximum peak temperature" refers to the temperature at which the endotherm reaches its maximum in a differential thermal curve obtained by differential scanning calorimetry (DSC). The "total peak area" refers to the area enclosed by two lines: the differential thermal curve and the extension of the high-temperature baseline in a differential thermal curve obtained by DSC. The "area within a total of 10°C, extending 7°C below the maximum peak temperature and 3°C above the maximum peak temperature" refers to the area enclosed by four lines: the baseline of the differential thermal curve (including the extension of the high-temperature baseline of the differential thermal curve to the low-temperature side), the high-temperature side perpendicular line, the low-temperature side perpendicular line, and the differential thermal curve, when perpendicular lines (lines parallel to the vertical axis) are drawn from the temperature axis at 7°C below the maximum peak temperature and 3°C above the maximum peak temperature. For more specific details, please refer to Japanese Patent Publication No. 4435434.

The content of component (B) is 0.2 to 15% by mass, and preferably 0.2 to 10% by mass, based on the total mass of the composition of the present invention. If the content of component (B) is excessively low, the smooth feeling of the composition of the present invention after application may be impaired, and if the content of component (B) is excessively high, the spreadability of the composition of the present invention when applied may be reduced.

From the viewpoint of achieving good spreadability during application of the composition of the present invention and suppressing stickiness after application, the mass ratio of component (B)/component (A) is preferably 0.05 to 30, more preferably 0.05 to 15, and even more preferably 0.1 to 10.

(Other additives)
The composition of the present invention may contain additives commonly used in cosmetics as appropriate, provided that the effects of the present invention are not impaired. Examples of such additives include oils, surfactants, moisturizers, thickeners, colorants, alcohols, UV protection agents, amino acids, vitamins, whitening agents, organic acids, inorganic salts, enzymes, antioxidants, stabilizers, preservatives, disinfectants, anti-inflammatory agents, skin activators, blood circulation promoters, antiseborrheic agents, anti-inflammatory agents, sequestering agents, pH adjusters, astringents, refreshing agents, fragrances, and pigments.

The present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to these. Furthermore, "%" in the amounts of components described below means "% by mass."

<Synthesis Example 1: Synthesis of Component (A-1)>
100 g of isotridecanol and 2.0 g of potassium hydroxide as a catalyst were charged into an autoclave, and the air in the autoclave was replaced with dry nitrogen. The catalyst was then dissolved at 140°C with stirring. Subsequently, 232 g of propylene oxide was added dropwise at 120°C and 0.2 to 0.5 MPa (gauge pressure) using a dropping device, and the mixture was stirred for 3 hours. Subsequently, a mixture of 528 g of ethylene oxide and 145 g of propylene oxide was added dropwise at 120°C and 0.2 to 0.5 MPa (gauge pressure) using a dropping device, and the mixture was stirred for 2 hours. Thereafter, the reaction mixture was removed from the autoclave, neutralized with hydrochloric acid to adjust the pH to 6 to 7, and treated at 100°C for 1 hour under a reduced pressure of -0.095 MPa (gauge pressure) to remove contained water. Further, filtration was carried out to remove the salt formed after the treatment, and component (A-1) was obtained.
Further, the number average molecular weights of the ethylene oxide and propylene oxide adducts were determined from the hydroxyl value obtained by hydroxyl value measurement in accordance with JIS K1557-1, and the values of a, b, and c in formula (1) were determined from the number average molecular weights.

<Synthesis Examples 2 to 4: Synthesis of Components (A-2), (A-3), (A'-1), and (A'-2)>
Components (A-2), (A-3), (A'-1) and (A'-2) were obtained in the same manner as in Synthesis Example 1, except that the starting materials and the amounts of ethylene oxide and propylene oxide added were changed.

For components (A-1) to (A'-2), the starting materials, type of alkylene oxide, a, b, c, (a+b+c), (2n+a), and (b+c)/(a+b+c) are shown in Table 1. Note that components (A-1) to (A-3) are alkylene oxide derivatives that satisfy the requirements of the present invention, while components (A'-1) and (A'-2) are alkylene oxide derivatives that do not satisfy the requirements of the present invention.

<Examples 1 to 9 and Comparative Examples 1 to 8>
The components (i.e., component (A) or its corresponding component (A'), component (B) or its corresponding component (B'), a component common to the oil phase, and a component common to the aqueous phase) were mixed in the types and amounts shown in Tables 2 or 3, heated to 75 to 80°C, mixed at that temperature using a homomixer, and then cooled to obtain an oil-in-water emulsion composition.

The compositions obtained in the Examples and Comparative Examples were evaluated as follows for body when applied, ease of spread when applied, stickiness after application, and smooth feeling when moisture is applied, and the results are shown in Tables 2 and 3. In addition, in Tables 2 and 3, the melting points of the components (B) or (B') used are listed next to the names of the compounds.

<Body when applied>
Ten healthy panelists applied 0.1 g of each composition of the Examples and Comparative Examples to their forearms. The texture of the composition upon application was evaluated on a three-point scale according to the following criteria. The total score of the 10 panelists was calculated and evaluated according to the following criteria.
(Rating criteria)
3 points: The texture is rich when applied.
2 points: The texture is slightly rich when applied.
1 point: The texture lacks body when applied.
(Evaluation criteria)
◎: 25 points or more ○: 20 points or more, less than 25 points △: 15 points or more, less than 20 points ×: Less than 15 points

<Good spreadability when applied>
Ten healthy panelists applied 0.1 g of each composition of the Examples and Comparative Examples to their forearms. The spread of the composition upon application was evaluated on a three-point scale based on the following criteria. The total score of the 10 panelists was calculated and evaluated according to the following criteria.
(Rating criteria)
3 points: Spreads well when applied.
2 points: Spreads fairly well when applied.
1 point: poor spread when applied.
(Evaluation criteria)
◎: 25 points or more ○: 20 points or more, less than 25 points △: 15 points or more, less than 20 points ×: Less than 15 points

<Sticky after application>
Ten healthy panelists applied 0.1 g of each of the compositions of the Examples and Comparative Examples to their forearms. After 5 minutes, the stickiness of the skin after application was evaluated on a three-point scale according to the following criteria. The total score of the 10 panelists was calculated and evaluated according to the following criteria.
(Rating criteria)
3 points: No stickiness on skin after application.
2 points: Skin feels slightly sticky when applied.
1 point: Sticky feeling on skin when applied.
(Evaluation criteria)
◎: 25 points or more ○: 20 points or more, less than 25 points △: 15 points or more, less than 20 points ×: Less than 15 points

<Smooth feeling when moisture adheres>
Ten healthy panelists applied 0.1 g of each composition of the Examples and Comparative Examples to their forearms. A 0.5% aqueous solution of sodium chloride, simulating sweat, was placed in a spray container and sprayed once onto the skin to which the composition had been applied. The feel after spraying was evaluated relative to the skin on a three-point scale according to the following rating scale. The total score of the 10 panelists was calculated and evaluated according to the following rating scale.
(Rating criteria)
3 points: When moisture is applied, the feel is smooth.
2 points: When moisture is applied, the feel is somewhat dry.
1 point: When moisture gets on the product, it does not feel smooth.
(Evaluation criteria)
◎: 25 points or more ○: 20 points or more, less than 25 points △: 15 points or more, less than 20 points ×: Less than 15 points

As is clear from Table 2, all of the compositions of Examples 1 to 9 had good body when applied, good spreadability when applied, stickiness after application, and a smooth feel when moisture was applied.
In contrast, as is clear from Table 3, the compositions of Comparative Examples 1 to 8 were not good in any of the following: richness upon application, good spreadability upon application, stickiness after application, or smooth feeling upon adhesion of moisture.

The composition of the present invention combines a rich, full-bodied texture with good spreadability when applied, and has a smooth, non-sticky feel even when it comes into contact with water after application, making it suitable for use in formulations such as creams and emulsions.

Claims (1)

The following components (A) and (B):
(A) The following formula (1):
RO-(AO) _a -[(PO) _b /(EO) _c ]-H...(1)
(In the formula,
R is a linear or branched alkyl group having 12 to 36 carbon atoms;
AO is an oxyalkylene group having 3 or 4 carbon atoms;
PO is an oxypropylene group;
EO is an oxyethylene group;
[(PO) _b /(EO) _c ] is a polyoxyalkylene group formed by randomly bonding PO and EO, and a, b, and c are the average number of moles of AO, PO, and EO added per molecule, respectively, and are within the ranges of 1≦a≦40, 1≦b≦40, 1≦c≦80, 20≦(a+b+c), and 0.1≦(b+c)/(a+b+c)<1.
and (B) a fatty acid ester wax having a melting point of 40 to 110°C, the fatty acid ester wax being composed of an alcohol having 1 to 6 hydroxyl groups and a fatty acid having 16 to 22 carbon atoms, and water, wherein the content of component (A) is 0.1 to 10% by mass and the content of component (B) is 0.2 to 15% by mass based on the total mass of the composition.