JP7794075B2 - Water-in-oil sunscreen cosmetics - Google Patents

Description

The present invention relates to a water-in-oil sunscreen cosmetic.

Sunscreen cosmetics protect the skin from UV damage and are applied to a wide range of areas of the body, including the face, neck, hands, arms, and legs. Therefore, they are required to have a pleasant texture and feel, such as being non-greasy or sticky, and easy to spread, as well as good UV protection and water resistance and abrasion resistance to maintain that effect. Because the external phase of water-in-oil sunscreen cosmetics is oil, they have the advantages of being non-greasy and water-resistant. However, water-in-oil sunscreen cosmetics tend to be sticky, and the more UV protection agents added to achieve high UV protection, the more sticky the product becomes and the more difficult it becomes to spread. Furthermore, sunscreens made with low-viscosity oils to reduce stickiness can have the problem of sticking when applied to dry skin caused by winter air or air conditioning, making them particularly difficult to spread.

For example, Patent Document 1 proposes a water-in-oil emulsion cosmetic that contains an organic UV protection agent, zinc oxide, a polymer whose constituent units are a hydrophilic segment having N-acylalkyleneimine repeating units and an organopolysiloxane segment, an acrylic ester resin powder, a silicone resin, silicone oil, and water, thereby providing excellent UV protection and being non-sticky and non-greasy.

Patent Document 2 proposes a water-in-oil emulsion sunscreen cosmetic that contains a specific benzotriazole-type UV absorber, a surfactant, an electrolyte, and a specific silicone compound, which provides high UV protection while spreading easily and not leaving a sticky feeling.

One way to maintain UV protection is to improve the abrasion resistance of sunscreen cosmetics. In recent years, the number of times people wear masks to prevent infectious diseases has increased, and to prevent differences in the degree of sunburn on the face depending on whether or not a mask is worn, it is necessary to apply sunscreen underneath the mask as well. However, when adjusting the mask or putting it on or taking it off, pressing the mask with your fingers or wearing a tight-fitting mask can easily cause the mask to rub against the face, causing the sunscreen cosmetics to come off. For this reason, there is a demand for products that can form a cosmetic film that is resistant to abrasion.

Patent Document 3 proposes a water-in-oil emulsion cosmetic for sunscreen that is less sticky and has excellent abrasion resistance, by combining an alkyl-modified silicone wax with a melting point of 60°C or higher, a hydrophobic UV scattering agent, and water.

JP 2016-69282 A Japanese Patent Application Laid-Open No. 2008-247897 Japanese Patent Application Laid-Open No. 2020-97576

Patent Documents 1 and 2 propose water-in-oil sunscreen cosmetics with reduced stickiness. However, according to the inventors' investigations, the water-in-oil emulsion cosmetic proposed in Patent Document 1 was insufficient in terms of ease of spreadability. Furthermore, the water-in-oil emulsion sunscreen cosmetic proposed in Patent Document 2 was insufficient in terms of ease of spreadability on dry skin and the durability of its high UV protection effect.

Patent Document 3 also proposes a water-in-oil emulsion sunscreen cosmetic that is expected to reduce stickiness and improve durability due to improved friction resistance. However, according to the inventors' investigations, the water-in-oil emulsion sunscreen cosmetic proposed in Patent Document 3 was insufficient in terms of ease of application.

In view of the above problems, the present invention aims to provide a water-in-oil sunscreen cosmetic that has enhanced UV protection effects due to SPF-enhancing ingredients, is non-sticky, can be spread all over the body even on dry skin, and forms a cosmetic film that is resistant to rubbing.

As a result of extensive research in light of the above-mentioned problems, the inventors discovered that a water-in-oil sunscreen cosmetic that can solve the above-mentioned problems can be obtained by combining a UV scattering agent, a specific oil, and an alkylene oxide derivative with a specific structure in specified amounts, leading to the completion of the present invention.

That is, the present invention relates to a water-in-oil sunscreen cosmetic composition containing 0.5 to 10 mass% of the following component (A), 5 to 35 mass% of component (B), 1 to 30 mass% of component (C), and 5 to 35 mass% of component (D):
(A) An alkylene oxide derivative represented by the following formula (1):

In formula (1), AO represents an oxyalkylene group having 3 to 4 carbon atoms, EO represents an oxyethylene group, a represents the number of moles of the oxyalkylene group having 3 to 4 carbon atoms added, b represents the number of moles of the oxyethylene group added, a represents a number from 0 to 50, b represents a number from 1 to 50, a+b≧10, and 0≦a/b≦2. When the alkylene oxide derivative represented by formula (1) has both the oxyalkylene group having 3 to 4 carbon atoms and the oxyethylene group, the oxyalkylene group having 3 to 4 carbon atoms and the oxyethylene group are added in a random or block manner, and in the case of block addition, the order of arrangement does not matter.
(B) an ultraviolet scattering agent; (C) an ester oil that is liquid at 25°C; and (D) a linear silicone oil having a kinematic viscosity of 1 to 20 mm ² /s at 25°C.

The water-in-oil sunscreen cosmetic of the present invention has enhanced UV protection effects due to the SPF-enhancing ingredients, is non-sticky, can be spread all over the body even on dry skin, and forms a cosmetic film that is resistant to rubbing.

The following describes an embodiment of the present invention.

In this specification, numerical ranges defined using the symbol "~" are intended to include the numerical values at both ends of the symbol (upper and lower limits). For example, "2 to 5" means a range of 2 or more and 5 or less.

The sunscreen cosmetic of the present invention contains at least component (A), component (B), component (C), and component (D). Each component is described below.

[Component (A)]
Component (A) is an alkylene oxide derivative represented by formula (1).

In formula (1), AO represents an oxyalkylene group having 3 to 4 carbon atoms, EO represents an oxyethylene group, a represents the number of moles of the oxyalkylene group having 3 to 4 carbon atoms added, b represents the number of moles of the oxyethylene group EO added, a represents a number from 0 to 50, b represents a number from 1 to 50, a + b ≧ 10, and 0 ≦ a / b ≦ 2. The oxyalkylene groups having 3 to 4 carbon atoms and the oxyethylene groups are added in a random or block manner, and if they are added in blocks, the order of arrangement is not important.

By setting a to 50 or less, the SPF improvement effect and ease of spreading can be improved, stickiness can be reduced, and the cosmetic film's resistance to rubbing can be improved. Therefore, a should be between 0 and 50, with 0 to 40 being preferable and 0 to 30 being most preferable.

By setting b to 1 or greater, the SPF can be improved, the ease of spreading on dry skin can be improved, the scrubbing resistance of the cosmetic film can be improved, and stickiness can be reduced. Furthermore, by setting b to 50 or less, stickiness can be reduced and the scrubbing resistance of the cosmetic film can be improved. Therefore, b should be between 1 and 50, with 10 to 40 being preferred, and 10 to 30 being most preferred.

By making a+b 10 or greater, it is possible to improve the ease of spreading on dry skin and the resistance of the cosmetic film to rubbing. It also improves the SPF improvement effect. Therefore, a+b should be 10 or greater, with 20 or greater being most preferable. There is no particular upper limit for a+b, but from the perspective of improving the SPF improvement effect, reducing stickiness, and improving the resistance of the cosmetic film to rubbing, it is preferable to make it 50 or less.

When a is greater than 0, the oxyalkylene groups and oxyethylene groups having 3 to 4 carbon atoms are added randomly or in a block pattern. When added in a block pattern, the order of arrangement is not important. When a is greater than 0, the oxyalkylene groups and oxyethylene groups having 3 to 4 carbon atoms are preferably added randomly.

By setting the a/b ratio to 2 or less, stickiness can be reduced and the SPF improvement effect, resistance to rubbing of the cosmetic film, and ease of spreading can be improved. Therefore, a/b should be 2 or less, with 1.2 or less being most preferable. The lower limit of a/b is 0, but it can also be 0.3 or more.

Examples of oxyalkylene groups having 3 to 4 carbon atoms include oxypropylene groups and oxybutylene groups, with oxypropylene groups being the most preferred. The alkylene oxide derivative represented by formula (1) may contain either an oxypropylene group or an oxybutylene group, or both. When both groups are present, the oxypropylene groups and oxybutylene groups may be arranged in either a random or block configuration. When added in a block configuration, the order of arrangement is not important.

Component (A) has a monoether structure in which an alkylene oxide is added to the first hydroxyl group of the three hydroxyl groups in glycerin. The monoether purity is 80% or more, preferably 90% or more, and more preferably 95% or more. There is no particular upper limit to the monoether purity, but it can be 100% or less.

The monoether purity can be calculated from the following formula using the peak integral value obtained by ¹ H-NMR measurement.

x represents the peak integral at approximately 2.4 ppm, which is derived from the methylene groups at the 1,3-positions of glycerin to which ethylene oxide has been added, when the peak integral at approximately 3.3 ppm, which is derived from the methine group at the 2-position of glycerin and is detected only in monoethers, is taken as 1. However, if the peak integral at approximately 3.3 ppm, which is derived from the methine group at the 2-position of glycerin in monoethers, cannot be detected, the monoether purity is taken as 0.

The alkylene oxide derivative represented by formula (1) can be produced by known methods. An alkylene oxide is addition-polymerized with an alkyl alcohol, such as isopropylidene glycol in which all but the primary hydroxyl group of glycerin has been protected, in the presence of an alkali catalyst at 50-160°C and 0.5 MPa (gauge pressure) or less. When using two or more alkylene oxides, in the case of a random alkylene oxide, the two or more alkylene oxides are mixed together before addition polymerization. In the case of a block alkylene oxide, AO may be polymerized first followed by EO, or EO may be polymerized first followed by AO. An acid such as hydrochloric acid, phosphoric acid, or acetic acid is then added to deacetalize the mixture. The excess acid is neutralized with a base such as potassium hydroxide or sodium hydroxide, and the water and neutralization salt are then removed to obtain the alkylene oxide derivative.

The concentration of component (A) added is 0.5 to 10% by mass, preferably 1 to 8% by mass, and more preferably 1.5 to 5% by mass, based on the total mass of the water-in-oil sunscreen cosmetic. Increasing the content of component (A) can provide sufficient SPF improvement and improve the ease of spreading on the skin. By not including an excessive amount of component (A), uneven application is less likely to occur, stickiness is less likely to occur, and the cosmetic is less susceptible to rubbing.

[Component (B)]
Component (B) is an ultraviolet scattering agent. An ultraviolet scattering agent refers to a substance that can reflect and scatter ultraviolet rays to protect the skin and the like from ultraviolet rays. Examples of ultraviolet scattering agent materials that can be used in the present invention include titanium oxide, zinc oxide, iron oxide, zirconium oxide, and aluminum oxide. Examples of ultraviolet scattering agents include those obtained by microparticulating these materials or composites. The ultraviolet scattering agent preferably contains one or two types selected from titanium oxide and zinc oxide.

The titanium oxide and zinc oxide used as UV scattering agents may be the titanium oxide and zinc oxide commonly used in cosmetics. Preferably, the skin composition contains titanium oxide and zinc oxide with better dispersibility, for example, titanium oxide and zinc oxide that have been surface-treated, specifically hydrophobized, using a known method as needed.

Surface treatment methods include silicone treatment with methylhydrogenpolysiloxane, methylpolysiloxane, etc.; fluorine treatment with perfluoroalkyl phosphate ester, perfluoroalcohol, etc.; amino acid treatment with N-acylglutamic acid, etc.; alkylalkoxysilane treatment with octyltriethoxysilane, octyltrimethoxysilane, etc.; lecithin treatment; metal soap treatment; fatty acid treatment; alkyl phosphate ester treatment, etc.

Component (B) is preferably microparticulated to an average primary particle size of 8 to 80 nm, more preferably 10 to 20 nm.

The concentration of the UV scattering agent added is 5 to 35% by mass, preferably 10 to 30% by mass, and more preferably 15 to 25% by mass, based on the total mass of the water-in-oil sunscreen cosmetic. By increasing the content of component (B), sufficient UV protection effects as a sunscreen can be obtained, while by not including an excessive amount of component (B), the product is easier to spread, is less prone to unevenness, and is less likely to have adverse effects on the feel when used, such as a rough feeling or a white cast.

[Component (C)]
Component (C) is an ester oil that is liquid at 25° C. The ester oil that is liquid at 25° C. used in the present invention is preferably an ester oil of a linear or branched, saturated or unsaturated fatty acid or hydroxy fatty acid having 8 to 28 carbon atoms with a linear or branched, saturated or unsaturated alcohol having 2 to 28 carbon atoms, and examples thereof include isononyl isononanoate, isotridecyl isononanoate, isopropyl myristate, myristyl myristate, octyldodecyl myristate, isopropyl palmitate, isopropyl isostearate, 2-ethylhexyl hydroxystearate, butyl stearate, neopentyl glycol dicaprate, cetyl 2-ethylhexanoate, and 2-ethylhexanoic acid. Examples of the glycerin-based copolymer include pentaerythrityl, isostearyl isostearate, trimethylolpropane triisostearate, neopentyl glycol di-2-ethylhexanoate, trimethylolpropane tri-2-ethylhexanoate, pentaerythritol tetra-2-ethylhexanoate, cetyl octanoate, oleyl oleate, octyldodecyl oleate, decyl oleate, ethyl oleate, octyldodecyl erucate, isocetyl stearate, butyl stearate, diisopropyl sebacate, 2-ethylhexyl palmitate, 2-hexyldecyl palmitate, and 2-heptylundecyl palmitate.

Preferred are isopropyl myristate, 2-ethylhexyl hydroxystearate, diisopropyl sebacate, neopentyl glycol dicaprate, and isononyl isononanoate, which are obtained by reacting saturated or unsaturated fatty acids or hydroxy fatty acids having 8 to 10 carbon atoms with saturated or unsaturated alcohols having 3 to 10 carbon atoms, and from the standpoint of increasing the resistance to rubbing of the cosmetic film, isopropyl myristate and 2-ethylhexyl hydroxystearate are even more preferred.

The concentration of the ester oil that is liquid at 25°C is 1 to 30% by mass, preferably 3 to 25% by mass, and more preferably 5 to 20% by mass, based on the total mass of the water-in-oil sunscreen cosmetic. Increasing the content of component (C) makes it easier to spread over a wide area and ensures that the cosmetic film is sufficiently resistant to rubbing, while not including an excessive amount of component (C) reduces stickiness and makes it easier to spread.

[Component (D)]
Component (D) is a linear silicone oil having a kinematic viscosity of 1 to 20 mm ² /s at 25° C. Examples of linear silicone oils having a kinematic viscosity of 1 to 20 mm ² /s at 25° C. include dimethylpolysiloxane (dimethicone) and methylphenylpolysiloxane. Dimethylpolysiloxane is preferably used.

The concentration of the linear silicone oil having a kinematic viscosity of 1 to 20 mm ² /s at 25° C. added is 5 to 35% by mass, preferably 10 to 30% by mass, and more preferably 15 to 25% by mass, relative to the total mass of the water-in-oil sunscreen cosmetic. By increasing the content of component (D), it is possible to ensure sufficient ease of spreading over a wide range, and by not including an excessive content of component (D), it is possible to increase resistance to rubbing and improve the stability of the cosmetic.

The total concentration of components (C) and (D) added in the present invention is preferably 10 to 45% by mass, and more preferably 20 to 35% by mass, based on the total mass of the water-in-oil sunscreen cosmetic. Furthermore, the value calculated by component (C)/[component (C) + component (D)] is preferably 0.10 to 0.70, and more preferably 0.15 to 0.60. When the value of component (C)/[component (C) + component (D)] is 0.10 or higher, resistance to rubbing and ease of spread on dry skin are sufficiently enhanced, while when it is 0.60 or lower, stickiness is reduced and the cosmetic is easy to spread.

[Other ingredients]
The water-in-oil sunscreen cosmetic of the present invention typically contains water in addition to the above-mentioned components (A) to (D). Examples of water include purified water, tap water, industrial water, and deionized water. The concentration of water added in the present invention is typically 5 to 60% by mass, preferably 10 to 55% by mass, and more preferably 15 to 50% by mass, based on the total mass of the water-in-oil sunscreen cosmetic.

In addition to the above-mentioned components (A) to (D) and water, the sunscreen cosmetic of the present invention may contain additives used in cosmetics, quasi-drugs, pharmaceuticals, etc., as needed, provided that the purpose of the present invention is not impaired.

Such additives include, for example, ultraviolet absorbers, surfactants, etc. Examples of ultraviolet absorbers include amyl paradimethylbenzoate, 2-ethylhexyl paradimethylaminobenzoate, ethyl 4-[N,N-di(2-hydroxypropyl)amino]benzoate, hexyl diethylaminohydroxybenzoylbenzoate, 2-ethylhexyl salicylate, 2-ethoxyethyl paramethoxycinnamate, 2-ethylhexyl paramethoxycinnamate, glyceryl di-paramethoxycinnamate mono-2-ethylhexanoate, 2,4,6-tris[4-(2-ethylhexyloxycarbonyl)anilino]-1,3,5-triazine, octocriptine, methylparaben ... Examples of ultraviolet absorbers include hexyl diethylaminohydroxybenzoylbenzoate, 4-t-butyl-4'-methoxydibenzoylmethane, dimethicodiethyl benzalmalonate, and bisethylhexyloxyphenol methoxyphenyl triazine. Preferred are diethylaminohydroxybenzoyl hexyl benzoate, 2-ethylhexyl paramethoxycinnamate, 2,4,6-tris[4-(2-ethylhexyloxycarbonyl)anilino]-1,3,5-triazine, octocrylene, 4-t-butyl-4'-methoxydibenzoylmethane, and bisethylhexyloxyphenol methoxyphenyl triazine. More preferred are diethylaminohydroxybenzoyl hexyl benzoate, 2-ethylhexyl paramethoxycinnamate, 4-t-butyl-4'-methoxydibenzoylmethane, and bisethylhexyloxyphenol methoxyphenyl triazine. These ultraviolet absorbers can be used singly or in combination as needed.

Surfactants with an HLB of 3 to 7 are preferred, including PEG-9 polydimethylsiloxyethyl dimethicone, PEG-10 dimethicone, and polyglyceryl-2 stearate. PEG-9 polydimethylsiloxyethyl dimethicone is preferred.

When the water-in-oil sunscreen cosmetic of the present invention contains other ingredients, the content of the other ingredients relative to the total weight of the water-in-oil sunscreen cosmetic is preferably 30% by weight or less, and more preferably 0.01% by weight to 20% by weight.

The water-in-oil sunscreen cosmetic of the present invention is formed by emulsifying an oily component and an aqueous phase component, and can be produced according to commonly used methods. For example, it can be produced by mixing and dissolving oily components such as components (C) and (D), adding component (B) while stirring, and then adding and emulsifying an aqueous phase component prepared by mixing and dissolving component (A) and the like in water.

The water-in-oil sunscreen cosmetic of the present invention can be provided in a variety of forms suitable for various uses, such as emulsion, cream, gel, etc.

The present invention will be explained in detail below with reference to examples and comparative examples.

[Examples 1 to 11, Comparative Examples 1 to 8]
<Synthesis Example 1: Example Compound A-1>
100 g of isopropylidene glycol and 0.5 g of potassium tert-butoxide 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 130°C with stirring. Subsequently, 866 g of ethylene oxide was added dropwise using a dropping device at 130°C and 0.2 to 0.5 MPa (gauge pressure), and the mixture was stirred for 1 hour. Thereafter, the reaction composition was removed from the autoclave, and the pH was adjusted to 3 with hydrochloric acid to carry out deacetalization. Thereafter, the reaction composition was neutralized with potassium hydroxide and treated at 100°C under a reduced pressure of -0.095 MPa (gauge pressure) for 3 hours to remove contained water, followed by filtration to obtain Example Compound A-1.

<Synthesis Examples 2 to 4: Example Compound A-2, Comparative Compounds A'-1 and A'-2>
Example compound A-2 and comparative compounds A'-1 to A'-2 were obtained in the same manner as in Synthesis Example 1, except that the amounts of ethylene oxide, propylene oxide, and butylene oxide added were changed. However, in the case of a random adduct such as comparative compound A'-1, ethylene oxide and propylene oxide or butylene oxide were mixed in advance and the mixture was added dropwise using a dropping device to carry out the reaction. In addition, in the case of a block adduct such as example compound A-2, propylene oxide was added dropwise using a dropping device to achieve a predetermined number of moles of addition, and then ethylene oxide was added dropwise using a dropping device to achieve a predetermined number of moles of addition, to carry out the reaction.

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 and b in formula (1) were determined from this number-average molecular weight. Table 1 shows the total average number of moles of ethylene oxide and propylene oxide added for example compounds A-1 to A-2 and comparative example compounds A'-1 to A'-2. In Table 1, "AO" represents the type of oxyalkylene group (AO) possessed by the alkylene oxide derivative shown in formula (1), and "PO" represents an oxypropylene group. Table 1 also shows the monoether purity calculated using the method described above.

[Evaluation method]
Components (A) to (D), (A'), (D') and other components were prepared as water-in-oil sunscreen cosmetics in the compositions shown in Tables 2 and 3 (Examples), and Tables 4 and 5 (Comparative Examples). These were then evaluated according to the following criteria for (1) SPF improvement effect, (2) non-stickiness, (3) ease of spreading on dry skin, and (4) strength of the cosmetic film against rubbing.

(1) SPF Improvement Effect For each formulation, a blank without component (A) was prepared, and each sample was applied to a PMMA plate (HELIOPLATE HD6, manufactured by Labsphere) at 2 mg/ ^cm² . The sample was then allowed to stand in a dark place for 20 minutes, and the SPF of the sample was measured using an SPF analyzer (UV-2000S, manufactured by Labsphere). Measurements were taken at nine points on the plate, and the average value was used to obtain the [SPF _blank ]. The [SPF _sample ] was also measured in the same manner for each composition of the Examples and Comparative Examples. The rate of change in SPF relative to the blank was calculated using the following formula:

SPF change rate relative to blank = [SPF _sample ] / [SPF _blank ] x 100

The SPF change rate relative to the blank was evaluated according to the following criteria, and a sunscreen cosmetic product with an SPF-improving effect was determined to be 125% or higher.

<Evaluation criteria>
◎: Rate of change is 150% or more ○: Rate of change is 125% or more but less than 150% point △: Rate of change is 110% or more but less than 125% ×: Rate of change is less than 110%

(2) Non-stickiness Twenty women (aged 23 to 55) were used as panelists, and after applying sunscreen cosmetics to the entire face, hands, arms, and legs, they were scored for stickiness according to the following evaluation criteria. The scores of the 20 panelists were calculated in total, and sunscreen cosmetics with a total score of 20 or more were judged to be non-sticky.

<Evaluation criteria>
2 points: No stickiness was felt.
1 point: Slight stickiness was felt.
0 points: Sticky feeling.

◎: Total score is 30 points or more ○: Total score is 20 points or more but less than 30 points
△: Total score is 10 or more but less than 20 points ×: Total score is less than 10 points

(3) Ease of Spreading on Dry Skin Twenty women (aged 23 to 55) were used as panelists, and after applying ethanol to the entirety of their hands, arms, and legs, they were left to stand for 20 minutes in a room with a constant humidity level. After that, the ease of spreading the sunscreen cosmetic when applying it was scored according to the following evaluation criteria. The scores of the 20 panelists were calculated in total, and sunscreen cosmetics with a total score of 20 or more were judged to be easy to spread even on dry skin.

<Evaluation criteria>
2 points: I was able to spread it on my dry skin without feeling any sticking.
1 point: When spreading on dry skin, I felt a slight stickiness, but was able to spread it.
0 points: When spreading on dry skin, it felt like it was catching and was difficult to spread.

◎: Total score is 30 points or more ○: Total score is 20 points or more but less than 30 points △: Total score is 10 points or more but less than 20 points ×: Total score is less than 10 points

(4) Strength of cosmetic film against rubbing Each sunscreen cosmetic was applied to a PMMA plate (HELIOPLATE HD6, manufactured by Labsphere) at 2 mg/ ^cm2 , left to stand in a dark place for 20 minutes, and the SPF was measured using an SPF analyzer (UV-2000S, manufactured by Labsphere). An 85 g weight was then placed on the same plate so as to sandwich a paper wiper (Kimwipe S-200, manufactured by Nippon Paper Crecia Co., Ltd.), and the weight and paper wiper were rubbed together on the plate, and the SPF was measured in the same manner. The rate of change in SPF before and after rubbing with the paper wiper was calculated using the following formula. A rate of change of less than 20% was determined to be a sunscreen cosmetic that was capable of forming a cosmetic film that was resistant to rubbing.

SPF change rate due to rubbing (%) = {([SPF before rubbing] - [SPF after rubbing]) / [SPF before rubbing]} x 100

◎: The rate of change is 0% or more and less than 10%. ○: The rate of change is 10% or more and less than 20%. △: The rate of change is 20% or more and less than 30%. ×: The rate of change is 30% or more and less than 100%.

The compositions and evaluation results of Examples 1 to 11 and Comparative Examples 1 to 8 are shown in Tables 2 to 5. The compositions listed in Tables 2 to 5 indicate the ratio (parts by mass) of each component when the total mass is 100 parts by mass. "C+D" indicates the total amount of component (C), component (D), and component (D'), and "C/(C+D)" indicates the ratio of component (C) to the total amount. Table 6 shows the compositions of components common to sunscreen cosmetics. The compositions listed in Table 6 indicate the ratio (parts by mass) of each component when the total mass of the compositions listed in Tables 2 to 5 is 100 parts by mass.

The ingredients used in the sunscreen cosmetics are as follows:
Titanium oxide: fatty acid-treated titanium oxide fine particles ("MT-10EX" manufactured by Teika Corporation, average primary particle diameter 10 nm)
Zinc oxide: Silicone-treated zinc oxide fine particles ("MZY-505M" manufactured by Teika Corporation, average primary particle diameter 25 nm)
PEG-9 polydimethylsiloxyethyl dimethicone: "KF-6028" manufactured by Shin-Etsu Chemical Co., Ltd., HLB 4.0)

Furthermore, the isopropyl myristylates, diisopropyl sebacates, ethylhexyl hydroxystearate, and isononyl isononanoates used as component (C) are all ester oils that are liquid at 25°C.

All of the samples from Examples 1 to 11 had sufficient SPF improvement effects, were non-sticky, could be spread all over the body even on dry skin, and formed a cosmetic film that was resistant to rubbing.

On the other hand, sufficient effects were not obtained in Comparative Examples 1 to 8.

In other words, Comparative Example 1 did not contain component (A), so there was no SPF improvement effect, the resistance to rubbing was not significantly improved, and the ease of spread on dry skin was insufficient. Comparative Examples 2 and 3 contained alkylene oxide derivatives different from component (A), so the SPF improvement effect, ease of spread on dry skin, and non-stickiness were insufficient, and the resistance to rubbing was not significantly improved. Comparative Example 4 did not contain component (C), so the ease of spread on dry skin and resistance to rubbing were insufficient. Comparative Example 5 did not contain component (D), so the ease of spread on dry skin was particularly insufficient, and the resistance to rubbing was not significantly improved. Comparative Example 6 contained an excessive amount of component (A), so the non-stickiness and ease of spread on dry skin were insufficient. In Comparative Example 7, the amount of component (B) blended was excessive, resulting in insufficient non-stickiness, ease of spread on dry skin, and little improvement in resistance to rubbing. In Comparative Example 8, a silicone oil different from component (D) was blended, resulting in insufficient non-stickiness, ease of spread on dry skin, and resistance to rubbing.

The medium-oil sunscreen cosmetic of the present invention can be applied to the face, skin, and other skin types, and offers unique effects not available with conventional sunscreen cosmetics, specifically, ease of spread on dry skin, non-stickiness, and resistance to rubbing of the cosmetic film, making it expected to be widely used in sunscreen cosmetics.

Claims (1)

A water-in-oil sunscreen cosmetic comprising 0.5 to 10 mass% of the following component (A), 5 to 35 mass% of component (B), 1 to 30 mass% of component (C), and 5 to 35 mass% of component (D):
(A) An alkylene oxide derivative represented by the following formula (1):
(In formula (1), AO represents an oxyalkylene group having 3 to 4 carbon atoms, EO represents an oxyethylene group, a represents the number of moles of the oxyalkylene group having 3 to 4 carbon atoms added, b represents the number of moles of the oxyethylene group added, a represents a number from 0 to 50, b represents a number from 1 to 50, a+b≧10, and 0≦a/b≦2. When the alkylene oxide derivative represented by formula (1) has both the oxyalkylene group having 3 to 4 carbon atoms and the oxyethylene group, the oxyalkylene group having 3 to 4 carbon atoms and the oxyethylene group are added in a random or block manner, and in the case of block addition, the order of arrangement does not matter.)
(B) an ultraviolet scattering agent; (C) an ester oil that is liquid at 25°C; and (D) a linear silicone oil having a kinematic viscosity of 1 to 20 mm ² /s at 25°C.