OILY MOISTURIZER AND TOPICAL SKIN COMPOSITION CONTAINING SAME

Abstract

The present invention provides an oily moisturizer composed of an esterified product of a component A and a component B, or an esterified product of the component A, the component B and a component C, wherein the hydroxyl value of the esterified product is within a range from 0 to 180 mgKOH/g, and the mass ratio between fatty acid residues derived from the component B and fatty acid residues derived from the component C within the fatty acid residues that constitute the esterified product of the component A, the component B and the component C is within a range from 99.9:0.1 to 25:75. The invention also provides a topical skin composition containing the oily moisturizer.

Component A: a polyglycerol having an average polymerization degree, calculated from the hydroxyl value, of 2 to 10

Component B: one fatty acid, or two or more fatty acids, selected from among linear saturated fatty acids of 6 to 10 carbon atoms

Component C: one fatty acid, or two or more fatty acids, selected from among fatty acids of 6 to 28 carbon atoms (but excluding fatty acids of the component B)

Claims

1. An oily moisturizer composed of an esterified product of a component A and a component B, or an esterified product of the component A, the component B and a component C, wherein a hydroxyl value of the esterified product is within a range from 0 to 180 mgKOH/g, and a mass ratio between fatty acid residues derived from the component B and fatty acid residues derived from the component C within fatty acid residues that constitute the esterified product of the component A, the component B and the component C is within a range from 99.9:0.1 to 25:75. Component A: a polyglycerol having an average polymerization degree, calculated from a hydroxyl value, of 2 to 10 Component B: one fatty acid, or two or more fatty acids, selected from among linear saturated fatty acids of 6 to 10 carbon atoms Component C: one fatty acid, or two or more fatty acids, selected from among fatty acids of 6 to 28 carbon atoms (but excluding fatty acids of the component B)

2. The oily moisturizer according to claim 1, wherein the hydroxyl value of the esterified product is within a range from 0 to 160 mgKOH/g.

3. The oily moisturizer according to claim 1, wherein the component A is a polyglycerol having an average polymerization degree, calculated from a hydroxyl value, of 2 to 6, and the hydroxyl value of the esterified product is within a range from 0 to 100 mgKOH/g.

4. A topical skin composition comprising the oily moisturizer according to claim 1.

5. The topical skin composition according to claim 4, wherein the topical skin composition is a cosmetic, a face wash, a full body cleanser, or a topical pharmaceutical.

6. A moisture retention method for skin, the method comprising applying a topical skin composition comprising the oily moisturizer according to claim 1 to a skin surface.

7. Use, for a purpose of moisture retention, of an esterified product of a component A and a component B having a hydroxyl value within a range from 0 to 180 mgKOH/g, or an esterified product of the component A, the component B and a component C, having a hydroxyl value within a range from 0 to 180 mgKOH/g, and in which a mass ratio between fatty acid residues derived from the component B and fatty acid residues derived from the component C within constituent fatty acid residues is within a range from 99.9:0.1 to 25:75. Component A: a polyglycerol having an average polymerization degree, calculated from a hydroxyl value, of 2 to 10 Component B: one fatty acid, or two or more fatty acids, selected from among linear saturated fatty acids of 6 to 10 carbon atoms Component C: one fatty acid, or two or more fatty acids, selected from among fatty acids of 6 to 28 carbon atoms (but excluding fatty acids of the component B)

8. Use, for producing a topical skin composition, of an esterified product of a component A and a component B having a hydroxyl value within a range from 0 to 180 mgKOH/g, or an esterified product of the component A, the component B and a component C, having a hydroxyl value within a range from 0 to 180 mgKOH/g, and in which a mass ratio between fatty acid residues derived from the component B and fatty acid residues derived from the component C within constituent fatty acid residues is within a range from 99.9:0.1 to 25:75. Component A: a polyglycerol having an average polymerization degree, calculated from a hydroxyl value, of 2 to 10 Component B: one fatty acid, or two or more fatty acids, selected from among linear saturated fatty acids of 6 to 10 carbon atoms Component C: one fatty acid, or two or more fatty acids, selected from among fatty acids of 6 to 28 carbon atoms (but excluding fatty acids of the component B)

Description

EXAMPLES

[0227] The present invention is described below in further detail based on a series of examples, but the present invention is in no way limited by these examples. In the following description, unless specifically stated otherwise, “%” means “% by mass”.

[Examples 1 to 37, Comparative Examples 1 to 12] Production of Esterified Products

[0228] Using polyglycerols with an average polymerization degree of 2 to 10 and fatty acids as reaction raw materials, an esterification reactions were performed with appropriate adjustment of the molar ratio between the polyglycerol and the fatty acid, thus producing esterified products.

[0229] Specifically, first, each of the polyglycerols and fatty acids shown in Tables 47-1, 47-2 and 48 were placed in a four-neck flask, and under a stream of nitrogen, the mixture was heated to 180 to 240° C., and an esterification reaction was conducted for about 10 to 20 hours while the produced water was removed from the system. Following completion of the reaction, excess acid was removed if necessary, thus obtaining the target esterified product. The esterified products obtained in Production Examples 1 and 2 were evaluated as Examples 1 and 23 of the oily moisturizer.

[0230] For each of the obtained esterified products, the reaction raw materials used, the mass ratio between the constituent fatty acid residues, the hydroxyl value, the state (external appearance) at 35° C., the evaluation result for the moisture retention effect, and the evaluation result for the sensation upon use are shown in Tables 47-1, 47-2 and 48. Further, for the esterified products produced using two fatty acids as raw materials, the composition of the constituent fatty acid residues in the obtained esterified product was measured, and the mass ratio between each of the constituent fatty acid residues was calculated. These values are shown in Tables 47-1, 47-2 and 48.

[Production Example 1] Production of Esterified Product

[0231] Using diglycerol and caprylic acid as reaction raw materials, an esterification reaction was performed with appropriate adjustment of the molar ratio between the diglycerol and the caprylic acid to achieve a hydroxyl value for the obtained esterified product of 0 mgKOH/g, thus producing an esterified product.

[0232] Specifically, first, 1,153.6 g (8.0 mol) of caprylic acid and 166.2 g (1.0 mol) of diglycerol were placed in a four-neck flask, and under a stream of nitrogen, the mixture was heated to 230 to 240° C., and an esterification reaction was conducted for about 15 hours while the produced water was removed from the system. Following completion of the reaction, excess acid was removed, yielding 604 g of the target esterified product. The obtained esterified product had an acid value of 0.1 and a hydroxyl value of 0 mgKOH/g.

[Production Example 2] Production of Esterified Product

[0233] Using tetraglycerol, caprylic acid and capric acid as reaction raw materials, an esterification reaction was performed with appropriate adjustment of the molar ratio between the tetraglycerol, the caprylic acid and the capric acid to achieve a hydroxyl value for the obtained esterified product of about 75 mgKOH/g and a mass ratio between caprylate and caprate in the obtained esterified product of 2:8, thus producing an esterified product.

[0234] Specifically, first, 146.6 g (1.0 mol) of caprylic acid, 586.7 g (3.4 mol) of capric acid and 330 g (1.0 mol) of tetraglycerol were placed in a four-neck flask, and under a stream of nitrogen, the mixture was heated to 230 to 240° C., and an esterification reaction was conducted for about 25 hours while the produced water was removed from the system. The acid value of the reaction product was checked during the reaction, and the reaction was halted at the point where the acid value was confirmed as having fallen to less than 1, thus obtaining 871 g of the target esterified product.

[0235] The obtained esterified product had an acid value of 0.1 and a hydroxyl value of 75 mgKOH/g.

[0236] Further, the mass ratio between the constituent fatty acid residues in the obtained esterified product was caprylate:caprate=20:80.

<Measurement of Composition of Constituent Fatty Acid Residues in Esterified Products>

[0237] In the following examples and the like, the mass ratio between the various constituent fatty acid residues in an esterified product was measured by preparing derivatives in which the fatty acid residues within the esterified product had been methyl esterified using a method corresponding with the 2.4.1.1-2013 methyl esterification method (sulfuric acid-methanol method) (Japan Oil Chemists' Society Standard Methods for the Analysis of Fats, Oils and Related Materials—2013 edition” published by Japan Oil Chemists' Society), and then separating and measuring the obtained derivatives using a method corresponding with the 2.4.2.3-2013 fatty acid composition (capillary gas chromatograph method) (Japan Oil Chemists' Society Standard Methods for the Analysis of Fats, Oils and Related Materials—2013 edition” published by Japan Oil Chemists' Society).

[0238] Specifically, one drop of the esterified product was first placed in a test tube and dissolved in 2 mL of a sulfuric acid-methanol solution (a solution prepared by mixing 2 mL of sulfuric acid with 230 mL of methanol). Subsequently, the test tube was heated, and a transesterification reaction was used to prepare derivatives in which the fatty acid residues in the esterified product had been methyl esterified.

[0239] These methyl ester derivatives were dissolved in 2 mL of hexane and injected into the column of a gas chromatograph device fitted with a FID, and each of the methyl ester derivatives was separated and detected under the following GC analysis conditions.

<GC Analysis Conditions>

[0240] Column: DB-1ht (manufactured by Agilent Technologies, Inc.)

[0241] Injection volume: 1 μL

[0242] Carrier gas: helium

[0243] Column temperature: 50 to 370° C. (rate of temperature increase: 15° C./min)

[0244] Identification of the peaks in the chromatograph was performed by comparison with the retention times for peaks obtained by analyzing standard substances under the same measurement conditions as the test sample. The composition of the fatty acid residues in the esterified product was calculated based on the percentage (%) of the peak surface area for the peak of the methyl ester derivative derived from each fatty acid residue in the chromatograph.

<Skin Stratum Corneum Moisture Content Measurement Test>

[0245] In the present invention, the moisture retention effect of the esterified product, namely the improvement effect on the moisture retention function of the skin, was evaluated based on the change in the stratum corneum moisture content of the skin before and after application of the esterified product.

[0246] Measurement of the stratum corneum moisture content was performed using a stratum corneum moisture content measuring device (device name: SKICON-200), manufactured by IBS Co., Ltd. This stratum corneum moisture content measuring device is a device that is widely used for measuring the moisture state of the stratum comeum, and is a device that measures the electrical conductivity (μS) of the stratum comeum. The larger the skin moisture content, the higher the electrical conductivity of the stratum corneum becomes. Accordingly, the electrical conductivity (μS) measured using the stratum comeum moisture content measuring device was deemed to indicate the stratum comeum moisture content.

<Evaluation Test of Moisture Retention Effect Upon Single Application of Esterified Product>

[0247] The skin moisture retention effect of each test sample was evaluated by applying the test sample directly to washed skin, and then measuring the change in the skin stratum corneum moisture content after wiping the test sample off the skin using a cotton swab soaked in hexane.

[0248] The skin stratum corneum moisture content measurement test was conducted on a plurality of panelists in the season from autumn to spring when the skin is prone to dryness. Further, in order to remove the effects of room temperature and humidity on the measurement results, the tests were performed in a room in which the room temperature had been adjusted to 18 to 22° C. and the humidity had been adjusted to 40 to 55% RH.

[0249] Specifically, first, the forearm of the person was washed with soap, and the person was then held for 30 minutes in a room in which the room temperature and the humidity had been controlled within the above ranges to acclimatize the skin of the forearm to the measurement environment, thus completing preparations for the initial conditions for measurement.

[0250] Then, a square portion of the washed forearm having a length of 3 cm and a width of 3 cm was designated as the measurement region, and the stratum corneum moisture content of the skin in that region was measured and recorded as a blank value (the stratum comeum moisture content prior to test commencement).

[0251] Subsequently, 40 μL of the test sample being evaluated was applied uniformly to the square measurement region of the forearm. Sixty minutes after the application, a cotton swab that had been immersed in hexane was used to wipe off the test sample, and 30 minutes after the test sample had been wiped off, the stratum corneum moisture content of the wiped region of the skin (the stratum corneum moisture content upon test completion) was measured.

[0252] Further, when evaluating the moisture retention effect of the test sample, in order to consider and subtract the change in the state of the skin during the measurement period, the stratum corneum moisture content of a portion of the skin to which the sample had not been applied was also measured prior to test commencement and upon test completion, and the change in the stratum corneum moisture content of this uncoated portion was calculated.

[0253] A moisture retention effect value (μS) was determined from the measured values for the skin stratum corneum moisture content based on the formulas below. The moisture retention effect value (μS) for each test sample was calculated as the average value for the moisture retention effect values (μS) across five panelists.

[Moisture retention effect value (μS)]=[stratum corneum moisture content (μS) of applied region upon test completion]−[stratum corneum moisture content (μS) of blank]−[change in stratum corneum moisture content (μS) of uncoated portion]  (Formula 1)

[Change in stratum corneum moisture content (μS) of uncoated portion]=[stratum comeum moisture content (μS) of uncoated portion upon test completion]−[stratum comeum moisture content (μS) of uncoated portion prior to test commencement]  (Formula 2)

[0254] Based on the moisture retention effect value (μS) for each test sample, the moisture retention effect of each test sample was evaluated using the criteria in Table 44. Test samples having a moisture retention evaluation of a1, b1 or c1 were adjudged to have a moisture retention effect, and were therefore deemed useful as moisturizers, whereas test samples having an evaluation of d1 or e1 were adjudged to lack a satisfactory moisture retention effect, and were therefore deemed not useful as moisturizers.

TABLE-US-00044 TABLE 44 Moisture Retention Evaluation Criteria Moisture retention Usability as Evaluation effect value (μS) oily moisturizer a1 70 or greater yes b1 at least 60 but less than 70 yes c1 at least 50 but less than 60 yes d1 at least 40 but less than 50 110 e1 less than 40 110
<Evaluation of Moisture Retention upon Single Application>

[0255] Using each of the esterified products, the <Evaluation test of moisture retention effect upon single application of esterified product> described above was conducted using five panelists to evaluate the moisture retention.

[0256] However, because the surface temperature of the skin during testing is about 30 to 35° C., evaluation samples that were solid at 35° C. could not be applied satisfactorily to the skin. Accordingly, for those esterified products that were solid at 35° C., the esterified product was mixed with cetyl 2-ethylhexanoate (product name “SALACOS 816T” manufactured by The Nisshin OilliO Group, Ltd.) in a mass a ratio of 1:1, and the resulting mixture that was liquid at 35° C. was used as the test sample for evaluation.

<Evaluation of Sensation upon Use>

[0257] For topical skin compositions, an excellent sensation upon use is also very important in actual usage.

[0258] Each of the esterified products was subjected to sensory evaluations for sensation upon use, specifically “lack of stickiness” and “adhesive feeling”.

[0259] Four specialist evaluation panelists evaluated the sensations of “lack of stickiness” and “adhesive feeling” when a test sample of the evaluation target product was applied uniformly to the forearm on a five-grade scale (5 points: good, 4 points: fairly good, 3 points: normal, 2 points: slightly poor, 1 point: poor). The evaluation score for the sensation upon use for each test sample was recorded as the average of the evaluation scores of the four panelists.

[0260] Based on the evaluation score for the “lack of stickiness” for each test sample, the sensation upon use of each test sample was evaluated against the criteria in Table 45.

TABLE-US-00045 TABLE 45 “Lack of Stickiness” Evaluation Criteria Evaluation Sensation upon use evaluation score (average) a2 greater than 4 points but not more than 5 points b2 greater than 3 points but not more than 4 points c2 greater than 2 points but not more than 3 points d2 greater than 1 point but not more than 2 points e2 1 point

[0261] Based on the evaluation score for the “adhesive feeling” for each test sample, the sensation upon use of each test sample was evaluated against the criteria in Table 46.

TABLE-US-00046 TABLE 46 “Adhesive Feeling” Evaluation Criteria Evaluation Sensation upon use evaluation score (average) a3 greater than 4 points but not more than 5 points b3 greater than 3 points but not more than 4 points c3 greater than 2 points but not more than 3 points d3 greater than 1 point but not more than 2 points e3 1 point

TABLE-US-00047 TABLE 47-1 Reaction raw materials, moisture retention evaluation results, and sensation upon use evaluation results for various esterified products Mass Moisture ratio of State at retention Moisture Sensation upon use Reaction raw materials constituent Hydroxyl 35° C. effect retention evaluation results Fatty acid (number fatty acid value (external value evaluation Lack of Adhesive Example Alcohol of carbon atoms) residues [mgKOH/g] appearance) [μS] result stickiness feeling 1 Diglycerol Caprylic acid (8) — 0 Liquid 66 b1 a2 b3 2 Capric acid (10) — 0 Liquid 57 c1 a2 b3 3 Caprylic acid (8) — 87 Liquid 78 a1 a2 b3 4 Caprylic acid (8) — 157 Liquid 65 b1 b2 a3 5 Caprylic acid (8) — 174 Liquid 56 c1 b2 a3 6 Caprylic acid (8)/ 81:19 0 Liquid 76 a1 a2 b3 Capric acid (10) 7 Caprylic acid (8)/ 52:48 2 Liquid 68 b1 a2 b3 Isocaprylic acid (8) 8 Caprylic acid (8)/ 30:70 1 Liquid 51 c1 a2 b3 Isocaprylic acid (8) 9 Caprylic acid (8)/ 71:29 1 Liquid 54 c1 a2 b3 Palmitic acid (16) 10 Triglycerol Caprylic acid (8) — 0 Liquid 57 c1 a2 b3 11 Caprylic acid (8)/ 79:21 37 Liquid 66 b1 a2 b3 Capric acid (10) 12 Caprylic acid (8)/ 80:20 139 Liquid 60 b1 b2 a3 Capric acid (10) 13 Caprylic acid (8)/ 80:20 173 Liquid 57 c1 b2 a3 Capric acid (10)

TABLE-US-00048 TABLE 47-2 Reaction raw materials, moisture retention evaluation results, and sensation upon use evaluation results for various esterified products Mass Moisture ratio of State at retention Moisture Sensation upon use Reaction raw materials constituent Hydroxyl 35° C. effect retention evaluation results Fatty acid (number fatty acid value (external value evaluation Lack of Adhesive Example Alcohol of carbon atoms) residues [mgKOH/g] appearance) [μS] result stickiness feeling 14 Tetraglycerol Caprylic acid (8) — 0 Liquid 72 a1 a2 b3 15 Capric acid (10) — 1 Liquid 69 b1 a2 b3 16 Caprylic acid (8) — 83 Liquid 75 a1 b2 a3 17 Caprylic acid (8) — 157 Liquid 79 a1 b2 a3 18 Capric acid (10) — 36 Liquid 81 a1 a2 a3 19 Capric acid (10) — 73 Liquid 76 a1 b2 a3 20 Pelargonic acid (9) — 0 Liquid 84 a1 a2 b3 21 Pelargonic acid (9) — 36 Liquid 74 a1 a2 b3 22 Caprylic acid (8)/ 19:81 2 Liquid 72 a1 b2 b3 Capric acid (10) 23 Caprylic acid (8)/ 20:80 75 Liquid 83 a1 b2 a3 Capric acid (10) 24 Caprylic acid (8)/ 21:79 176 Liquid 54 c1 c2 a3 Capric acid (10) 25 Caprylic acid (8)/ 29:71 84 Liquid 61 b1 d2 a3 Isolauric acid (12) 26 Caprylic acid (8)/ 31:69 0 Liquid 58 c1 a2 b3 Lauric acid (12) 27 Hexaglycerol Caprylic acid (8) — 2 Liquid 51 c1 b2 a3 28 Capric acid (10) — 4 Liquid 69 b1 b2 a3 29 Caprylic acid (8) — 82 Liquid 63 b1 c2 a3 30 Caprylic acid (8) — 142 Liquid 51 c1 c2 a3 31 Capric acid (10) — 44 Liquid 50 c1 b2 a3 32 Caprylic acid (8) — 176 Liquid 56 c1 d2 a3 33 Caprylic acid (8)/ 79:21 46 Liquid 63 b1 b2 a3 Capric acid (10) 34 Decaglycerol Caprylic acid (8) — 0 Liquid 59 c1 b2 a3 35 Caprylic acid (8) — 47 Liquid 74 a1 b2 a3 36 Caprylic acid (8) — 115 Liquid 54 c1 c2 a3 37 Caprylic acid (8) — 172 Liquid 62 b1 d2 a3

TABLE-US-00049 TABLE 48 Reaction raw materials, moisture retention evaluation results, and sensation upon use evaluation results for various esterified products Mass Moisture ratio of State at retention Moisture Sensation upon use Compar- Reaction raw materials constituent Hydroxyl 35° C. effect retention evaluation results ative Fatty acid (number fatty acid value (external value evaluation Lack of Adhesive Example Alcohol of carbon atoms) residues [mgKOH/g] appearance) [μS] result stickiness feeling 1 Diglycerol Lauric acid (12) — 1 Liquid 42 d1 b2 b3 2 Caprylic acid (8) — 188 Liquid 39 e1 c2 a3 3 Isocaprylic acid (8) — 0 Liquid 43 d1 b2 b3 4 Caprylic acid (8)/ 10:90 0 Liquid 31 e1 a2 b3 Isocaprylic acid (8) 5 Triglycerol Caprylic acid (8)/ 80:20 196 Liquid 44 d1 c2 a3 Capric acid (10) 6 Tetraglycerol Caprylic acid (8) — 185 Liquid 34 e1 d2 a3 7 Decaglycerol Caprylic acid (8) — 197 Liquid 44 d1 e2 a3 8 Trimethylol- Caprylic acid (8) — 1 Liquid 26 e1 a2 d3 propane Capric acid (10) — 1 Liquid 36 e1 a2 d3 9 Pentaerythritol Caprylic acid (8) — 0 Liquid 39 e1 a2 d3 10 Capric acid (10) — 1 Solid 29 e1 c2 d3 11 Sorbitol Caprylic acid (8) — 0 Solid 38 e1 c2 d3 12 2-methyl-1- Isostearic acid (18) — 0 Liquid 47 d1 a2 e3 propanol

Comparative Examples 13 to 25

[0262] Using various commercially available oils and glycerol, the <Evaluation of moisture retention upon single application> described above was conducted to ascertain the moisture retention effect and the sensation upon use for each substance. The state (external appearance) and the evaluation results for each of the commercially available oils and glycerol at 35° C. are shown in Table 49.

[0263] The glycerol of Comparative Example 25 is atypical aqueous moisturizer, and is widely used as a moisturizer. In the case of glycerol, removal of the glycerol that had been applied to the skin during the <Evaluation of moisture retention upon single application> described above was performed using a cotton swab that had been immersed in water rather than hexane. With the exception of changing the removal solvent from hexane to water, the evaluation conditions were the same as those described above in the <Evaluation of moisture retention upon single application>.

TABLE-US-00050 TABLE 49 State, moisture retention evaluation results, and sensation upon use evaluation results for various oils and glycerol State at Moisture Moisture Sensation upon use Compar- 35° C. retention retention evaluation results ative (external effect value evaluation Lack of Adhesive Example Name appearance) [μS] result stickiness feeling 13 2-ethylhexyl palmitate Liquid 26 e1 a2 e3 (product name ″SALACOS P-8″, manufactured by The Nisshin OilliO Group, Ltd.) 14 Cetyl 2-ethylhexanoate (product name ″SALACOS 816T″, manufactured Liquid 26 e1 a2 e3 by The Nisshin OilliO Group, Ltd.) 15 Neopentyl glycol dicaprate Liquid 22 e1 a2 e3 (product name ″ESTEMOL N-01″, manufactured by The Nisshin OilliO Group, Ltd.) 16 Glyceryl tri(caprylate/caprate) Liquid 26 e1 a2 e3 (product name ″O.D.O″, manufactured by The Nisshin OilliO Group, Ltd., constituent fatty acid ratio: caprylic acid/capric acid = 75/25) 17 Glyceryl tri(2-ethylhexanoate) Liquid 32 e1 a2 e3 (product name ″T.I.O″, manufactured by The Nisshin OilliO Group, Ltd.) 18 Pentaelythrityl tetra(2-ethylhexanoate) Liquid 27 e1 a2 d3 (product name ″SALACOS 5408″, manufactured by The Nisshin OilliO Group, Ltd.) 19 2-ethylhexyl hydroxystearate Liquid 39 e1 a2 e3 (product name ″SALACOS EH″, manufactured by The Nisshin OilliO Group, Ltd.) 20 Liquid paraffin Liquid 31 e1 a2 e3 21 Squalane Liquid 35 e1 a2 e3 22 Macadamia nut oil Liquid 44 d1 a2 d3 23 Castor oil Liquid 47 d1 e2 a3 24 Vaseline Liquid 33 e1 e2 a3 25 Glycerol Liquid 8 e1 e2 a3

[0264] Based on the results in Tables 47-1, 47-2, 48 and 49, it was evident that esterified products of Examples 1 to 37, namely, esterified products with a hydroxyl value within a range from 0 to 180 mgKOH/g that were obtained using, as essential reaction raw materials, a polyglycerol having an average polymerization degree, calculated from the hydroxyl value, of 2 to 6 as an alcohol, and one fatty acid, or two or more fatty acids, selected from among linear saturated fatty acids of 6 to 10 carbon atoms as a fatty acid, were oily substances, had a high moisture retention effect value of 50 μS or higher, and were extremely useful as oily moisturizers. In contrast, the esterified products of Comparative Example 1 and Comparative Example 3 which did not use a linear saturated fatty acid of 6 to 10 carbon atoms as the fatty acid, the esterified products of Comparative Example 2 and Comparative Examples 5 to 7 which had hydroxyl values exceeding 180 mgKOH/g, the esterified product of Comparative Example 4 in which the mass ratio among the fatty acid residues that constituted the esterified product between the fatty acid residues derived from the component B and the fatty acid residues derived from the component C was outside the range of 99.9:0.1 to 25:75, and the esterified products of Comparative Examples 8 to 12 which used an alcohol other than a polyglycerol as a raw material for the esterification reaction had moisture retention effect values of less than 50 μS, and did not exhibit moisture retention effects sufficient for use as oily moisturizers. The oils of Comparative Examples 13 to 24 are used as raw materials for conventional topical skin compositions, but the esterified products of Examples 1 to 37 that represent oily moisturizers according to the present invention were confirmed as exhibiting superior moisture retention effects to those of the oils of Comparative Examples 13 to 24.

[0265] The esterified products of Examples 1 to 37 were able to retain a high level of stratum corneum moisture content even after removal from the skin. It is thought that this indicates that these esterified products exhibit a moisture retention effect that relies on a mechanism of action that differs from that of conventional oily moisturizers that display a moisture retention effect, by forming an oily film on the skin surface that suppresses moisture transpiration from the skin surface.

[0266] Despite the fact that the glycerol of Comparative Example 25 is generally considered to have favorable moisture retention properties and is widely used as an aqueous moisturizer, the moisture retention evaluation result achieved in this test revealed a moisture retention effect value for glycerol of 8 μS, and a satisfactory moisture retention effect could not be confirmed. For reference purposes, after 60 minutes had elapsed from application of the glycerol, the skin stratum corneum moisture content with the glycerol still applied to the skin surface was measured prior to removal using water, and the increase in the electrical conductivity that corresponds with the moisture retention effect value was an extremely high numerical value of 477 μS, confirming why glycerol is said to be useful as a moisturizer. However, if the fact that glycerol is highly hygroscopic, and the fact that this numerical value decreases dramatically upon removal of the glycerol from the skin surface are taken into consideration, then it is surmised that this moisture retention effect value of glycerol observed prior to removal represents a result of measuring a combination of the moisture content of the stratum corneum and the moisture content contained within the glycerol.

Examples 38 to 40, Comparative Examples 26 to 31

[0267] Emulsions containing the esterified products of Examples 1, 3 and 23, the esterified product of Comparative Example 6 and the oils of Comparative Examples 14, 17, 20 and 22 were each investigated for moisture retention effect using a single application test (a test in which the number of applications to the skin surface was only one).

[0268] Specifically, emulsions having the blend formulations shown in Tables 51 and 52 were first produced by the following steps A to C. A product “LASEMUL 92AE” manufactured by Industrial Quimica Lasem (IQL) was used as the glyceryl stearate, a product “LASEMUL 4000” manufactured by IQL was used as the PEG-100 stearate, and a product “Pemulen TR-1” manufactured by The Lubrizol Corporation was used as the (acrylates/alkyl acrylate (C10 to C30)) crosspolymer.

[0269] A: Components 1 and 2 were heated and mixed at 70° C.

[0270] B: Components 3 to 10 were heated and mixed uniformly at 70° C.

[0271] C: The mixture obtained in step A was added to the mixture obtained in step B, and an emulsion was obtained by using an emulsifier (table-top Disper mixer) to conduct an emulsification at 2,000 rpm and 70° C. for 5 minutes.

<Evaluation Test of Moisture Retention Effect Upon Single Application of Emulsion>

[0272] The emulsions of Examples 38 to 40 and Comparative Examples 26 to 31 were evaluated for moisture retention by 10 panelists.

[0273] Specifically, the moisture retention effect of each emulsion containing an esterified product was evaluated by applying the emulsion containing the esterified product or oil to a washed portion of skin, washing the emulsion off with running water, and then measuring the stratum corneum moisture content of the skin.

[0274] The skin stratum corneum moisture content measurement test was conducted in the season from autumn to spring when the skin is prone to dryness. Further, in order to remove the effects of room temperature and humidity on the measurement results, the tests were performed in a room in which the room temperature had been adjusted to 18 to 22° C. and the humidity had been adjusted to 40 to 55% RH.

[0275] The skin stratum corneum moisture content was measured in the following manner.

[0276] First, in the same manner as described above in the <Evaluation test of moisture retention effect upon single application of esterified product>, the measurement portion was washed, the skin was left to acclimatize to the environment, a blank value measurement was performed, and an uncoated portion measurement was performed.

[0277] Subsequently, 40 mg of the emulsion was applied uniformly to a square measurement region of the forearm. Five hours after the application, the coated portion of the skin was washed under running water (2 L/min) for 20 seconds, any excess water was then wiped away, and 30 minutes later, the stratum corneum moisture content (μS) was measured.

[0278] Subsequently, in the same manner as described above in the <Evaluation test of moisture retention effect upon single application of esterified product>, the average value of the moisture retention effect values from the 5 panelists, determined using formula 1 and formula 2, was recorded as the moisture retention effect value (μS) for the emulsion.

[Moisture retention effect value (μS)]=[stratum corneum moisture content (μS) of applied region upon test completion]−[stratum corneum moisture content (μS) of blank]−[change in stratum corneum moisture content (μS) of uncoated portion]  (Formula 1)

[Change in stratum corneum moisture content (μS) of uncoated portion]=[stratum comeum moisture content (μS) of uncoated portion upon test completion]−[stratum corneum moisture content (μS) of uncoated portion prior to test commencement]  (Formula 2)

[0279] Based on the moisture retention effect value (μS) for each emulsion, the moisture retention effect of each emulsion was evaluated based on the criteria in Table 50. Emulsions having a moisture retention evaluation of a4, b4 or c4 were adjudged to be useful as emulsions having a moisture retention effect, whereas emulsions having an evaluation of d4 or e4 were adjudged to lack a satisfactory moisture retention effect, and were therefore not useful as emulsions having a moisture retention effect. The evaluation results for the various emulsions are shown in Tables 51 and 52.

TABLE-US-00051 TABLE 50 Moisture Retention Evaluation Criteria Usability as emulsion having a moisture Moisture retention retention Evaluation effect value (μS) effect a4 76 or greater yes b4 at least 71 but less than 76 yes c4 at least 66 but less than 71 yes d4 at least 61 but less than 66 no e4 less than 61 no

TABLE-US-00052 TABLE 51 Emulsion blend formulations and moisture retention evaluation results upon single application Blend formulation [% by mass] Components (raw materials) Example 38 Example 39 Example 40  1 Esterified product (Example 1) 10.0 0 0 Esterified product (Example 3) 0 10.0 0 Esterified product (Example 23) 0 0 10.0  2 Cetanol 0.2 0.2 0.2  3 Glyceryl stearate 0.02 0.02 0.02  4 PEG-100 stearate 0.08 0.08 0.08  5 (Acrylates/alkyl acrylate (C10 to C30)) 15.0 15.0 15.0 crosspolymer 2% aqueous solution  6 Glycerol 2.0 2.0 2.0  7 1,3-butylene glycol 5.0 5.0 5.0  8 1% solution of sodium hydroxide 6.0 6.0 6.0  9 Methylparaben 0.1 0.1 0.1 10 Water 61.6 61.6 61.6 Total 100.0 100.0 100.0 Moisture retention effect value [μS] 74 79 86 Moisture retention evaluation result b4 a4 a4

TABLE-US-00053 TABLE 52 Emulsion blend formulations and moisture retention evaluation results upon single application Blend formulation [% by mass] Compar- Compar- Compar- Compar- Compar- Compar- ative ative ative ative ative ative Example Example Example Example Example Example Components (raw materials) 26 27 28 29 30 31 1 Esterified product (Comparative Example 6) 10.0 0 0 0 0 0 Commercially available oil (Comparative Example 14) 0 10.0 0 0 0 0 Commercially available oil (Comparative Example 17) 0 0 10.0 0 0 0 Commercially available oil (Comparative Example 20) 0 0 0 10.0 0 0 Commercially available oil (Comparative Example 22) 0 0 0 0 10.0 0 2 Cetanol 0.2 0.2 0.2 0.2 0.2 0.2 3 Glyceryl stearate 0.02 0.02 0.02 0.02 0.02 0.02 4 PEG-100 stearate 0.08 0.08 0.08 0.08 0.08 0.08 5 (Acrylates/alkyl acrylate (C10 to C30)) 15.0 15.0 15.0 15.0 15.0 15.0 crosspolymer 2% aqueous solution 6 Glycerol 2.0 2.0 2.0 2.0 2.0 2.0 7 1,3-butylene glycol 5.0 5.0 5.0 5.0 5.0 5.0 8 1% solution of sodium hydroxide 6.0 6.0 6.0 6.0 6.0 6.0 9 Methylparaben 0.1 0.1 0.1 0.1 0.1 0.1 10 Water 61.6 61.6 61.6 61.6 61.6 71.6 Total 100.0 100.0 100.0 100.0 100.0 100.0 Moisture retention effect value [μS] 63 55 65 55 63 6 Moisture retention evaluation result d4 e4 d4 e4 d4 e4

[0280] Based on Tables 51 and 52, it was evident that, compared with the esterified product of Comparative Example 6 and the emulsions of Comparative Examples 26 to 30 containing commercially available oils, the emulsions containing an esterified product that was an oily moisturizer according to the present invention yielded a superior moisture retention effect even upon a single application to the skin surface and subsequent removal from the skin surface. Further, it was also confirmed that, compared with the emulsion that contained no oil (Comparative Example 31), adding an oily moisturizer according to the present invention yields an improved moisture retention effect value for the emulsion.

INDUSTRIAL APPLICABILITY

[0281] The present invention is able to provide an oily moisturizer having an excellent skin moisture retention effect, and a topical skin composition containing the oily moisturizer.