METHOD FOR IMPROVING SOLUBILITY OF SPARINGLY WATER-SOLUBLE COMPONENT

Abstract

A method for improving the solubility of a sparingly water-soluble component, the method including blending a compound represented by general formula (1) below with the sparingly water-soluble component in the presence of water. In formula (1), R.sup.1 denotes a group represented by formula (2) or a hydrocarbon group having 2 or 3 carbon atoms. In formula (2), R.sup.2 denotes an alkylene group having 1 to 3 carbon atoms, and n represents a number that is 0 or 1.

##STR00001##

Claims

1. A method for improving solubility of a sparingly water-soluble component, the method comprising blending a compound represented by general formula (1) below with the sparingly water-soluble component in the presence of water, ##STR00008## wherein R.sup.1 denotes a group represented by general formula (2) or a hydrocarbon group having 2 or 3 carbon atoms; ##STR00009## wherein R.sup.2 denotes an alkylene group having 1 to 3 carbon atoms, and n represents a number that is 0 or 1.

2. The method of claim 1, wherein the compound represented by general formula (1) is blended at a quantity of 0.05 to 40 mass % relative to the total quantity of a composition containing water, the compound represented by general formula (1) and the sparingly water-soluble component.

3. The method of claim 1, wherein the sparingly water-soluble component is one or more components selected from the group consisting of sparingly water-soluble antibacterial/antiseptic agents, sparingly water-soluble antioxidants, sparingly water-soluble vitamins, sparingly water-soluble UV absorbers, sparingly water-soluble fragrances, sparingly water-soluble cosmetic components and sparingly water-soluble vegetable oils.

4. The method of claim 1, wherein the sparingly water-soluble component is blended at a quantity of 0.05 to 40 mass % relative to the total quantity of a composition containing water, the compound represented by general formula (1) and the sparingly water-soluble component.

5. The method of claim 1, which further comprises blending an alcohol compound.

6. The method of claim 1, in which a surfactant is not used.

7. A method for producing a water-based cosmetic product, comprising using the method of claim 1.

Description

EXAMPLES

[0073] This invention will now be explained in detail by means of examples, but this invention is in no way limited to these examples, and may be altered as long as such alterations do not deviate from the scope of this invention. Moreover, in the examples etc. given below, % means mass percentage unless explicitly indicated otherwise.

[0074] Compounds that correspond to compounds represented by general formula (1), which are used in the examples, are shown below.

[0075] <Compounds Represented By General Formula (1)>

[0076] Compound (1)-1: 1,2-hexane diol (a compound in which R.sup.1 in general formula (1) is a propyl group) Compound (1)-2: Cyclohexyl glyceryl ether (a compound in which R.sup.1 in general formula (1) is a group represented by general formula (2) and n is 0 in general formula (2))

[0077] Compounds that replace compounds represented by general formula (1), which are used in the comparative examples, are shown below.

[0078] <Highly Water-Soluble Hydroxyl Group-Containing Compounds>

[0079] Ethanol

[0080] Propylene glycol

[0081] Dipropylene glycol

[0082] 1,3-butylene glycol

[0083] Glycerin

[0084] Moreover, examples of compounds similar to compounds represented by general formula (1) include 1,2-heptane diol, n-hexyl glyceryl ether and 2-ethylhexyl glyceryl ether. However, these compounds naturally exhibit poor solubility in water as compounds per se, and are therefore not suitable as comparative examples of compounds represented by general formula (1), and it is not possible to carry out investigations into improvements in solubility of the sparingly water-soluble components listed below. Therefore, these are excluded from comparative products.

[0085] Sparingly water-soluble compounds used in examples and comparative examples are shown below. Moreover, compounds having a solubility in water of 3 [g/100 g water] or less are used.

[0086] <Sparingly Water-Soluble Components>

[0087] n-hexyl glyceryl ether (antibacterial/antiseptic agent)

[0088] Methylparaben (antibacterial/antiseptic agent)

[0089] Caprylyl glycol (antibacterial/antiseptic agent)

[0090] 2-ethylhexyl glyceryl ether (antibacterial/antiseptic agent)

[0091] Phenoxyethanol (antibacterial/antiseptic agent)

[0092] Tocopherols (vitamins)

[0093] Peppermint oil (fragrance)

[0094] [Investigations into improvements in solubility of sparingly water-soluble components]

[0095] First, Solutions 1 to 9 shown in Table 1 below were prepared. Units for the numerical values shown in Table 1 are [g], and Solutions 1 to 9 were transparent colorless solutions.

TABLE-US-00001 TABLE 1 Solu- Solu- Solu- Solu- Solu- Solu- Solu- Solu- Solu- tion 1 tion 2 tion 3 tion 4 tion 5 tion 6 tion 7 tion 8 tion 9 Water 100 90 90 90 90 90 90 90 80 Com- 10 pound (1)-1 Com- 10 10 pound (1)-2 Ethanol 10 Propyl- 10 ene glycol Dipro- 10 pylene glycol Butyl- 10 10 ene glycol Glyc- 10 erin

[0096] Next, solubility [g/100 g solution] in Solutions 1 to 9 was investigated for three sparingly water-soluble components whose solubility in water could be confirmed but whose solubility was 1 [g/100 g water] or less (methylparaben, caprylyl glycol and 2-ethylhexyl glyceryl ether). In terms of test procedure, a target sparingly water-soluble component was added 0.1 g at a time to each of Solutions 1 to 9 shown in Table 1, and the added quantity of the sparingly water-soluble component immediately before the added quantity at which turbidity occurred is shown as the solubility in the table. In addition, confirmation that turbidity or precipitation had not occurred was carried out by adding 0.1 g of the sparingly water-soluble component at a time, stirring for 10 minutes at 25 C. and then leaving to stand. For example, in a case where methylparaben was dissolved in Solution 1, complete dissolution occurred until 0.2 g of methylparaben had been added, and turbidity occurred at the stage where 0.3 g of methylparaben had been added, and the solubility was therefore taken to be 0.2 g. Moreover, further tests were not carried out in cases where the solubility exceeded 5 [g/100 g solution].

[0097] Units for the numerical values shown in Table 2 below are [g/100 g solution].

TABLE-US-00002 TABLE 2 Compar- Compar- Compar- Compar- Compar- Compar- ative ative ative ative ative ative Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 1 ple 2 ple 2 ple 3 ple 4 ple 5 ple 6 ple 3 Solu- Solu- Solu- Solu- Solu- Solu- Solu- Solu- Solu- tion 1 tion 2 tion 3 tion 4 tion 5 tion 6 tion 7 tion 8 tion 9 Methylparaben 0.2 1.1 0.8 0.3 0.3 0.3 0.3 0.2 1.8 Caprylyl glycol 0.3 2.7 3.9 0.3 0.3 0.6 0.5 0.6 >5 2-ethylhexyl 0.2 1.5 2.3 0.3 0.3 0.3 0.2 0.2 >5 glyceryl ether

[0098] As a result, by comparing Comparative Example 1 with Examples 1 and 2, it was understood that the solubility of all three of these sparingly water-soluble components (methylparaben, caprylyl glycol and 2-ethylhexyl glyceryl ether) improved in Solution 2 and Solution 3, in which Compound (1)-1 and Compound (1)-2 were used. In addition, it was confirmed that the solubility of these sparingly water-soluble components was further improved in Solution 9, in which Compound (1)-2 and butylene glycol were both used.

[0099] Next, in order to investigate whether or not a similar advantageous effect was achieved for other sparingly water-soluble components (n-hexyl glyceryl ether, phenoxyethanol, tocopherols and peppermint oil), solubility values [g/100 g solution] were investigated by carrying out similar tests to those described above using Solutions 1, 2, 3 and 8.

TABLE-US-00003 TABLE 3 Comparative Comparative Example 7 Example 4 Example 5 Example 8 Solution 1 Solution 2 Solution 3 Solution 8 n-hexyl glyceryl 1.0 >5 >5 1.2 ether Phenoxyethanol 2.7 3.9 3.9 2.7 Tocopherols Insoluble 0.8 0.2 Insoluble Peppermint oil Insoluble 0.5 0.3 Insoluble

[0100] As a result, it became clear that the solubility of these other sparingly water-soluble components was improved in the same way as in the tests carried out using methylparaben, caprylyl glycol and 2-ethylhexyl glyceryl ether, which are also sparingly water-soluble components, in Solution 2, Solution 3 and Solution 9, in which Compound (1)-1 and Compound (1)-2 were used. In particular, it was confirmed that solubility in water of tocopherols and peppermint oil was achieved by using Compound (1)-1 and Compound (1)-2, despite tocopherols and peppermint oil being insoluble components that do not dissolve in water at all.

[0101] Moreover, formulations containing the sparingly water-soluble components obtained in Examples 1 to 5 can be used as transparent cosmetic products that impart functions (functionality) exhibited by sparingly water-soluble components, and it is also possible to blend optional components that are commonly used as additives for cosmetic products. As a specific example, Table 4 shows a formulation example of a transparent cosmetic product formulated using the method of this invention.

[0102] Formulation example 1 (a transparent cosmetic product)

TABLE-US-00004 TABLE 4 Component Blending quantity (mass %) Compound (1)-2 10 Tocopherols 0.2 Betaine 1 1% aqueous solution of hyaluronic acid 2 Water Balance Total 100

[0103] As a result, by using the method of this invention, it is possible to obtain a highly functional transparent cosmetic product which is gentle on the skin and which contains tocopherols (vitamins) that are insoluble in water without using a surfactant.

INDUSTRIAL APPLICABILITY

[0104] The method of this invention is not limited in terms of application, and can also be used in any type of application as long as this is an application that requires an improvement in the solubility of a sparingly water-soluble component. Of these applications, a high degree of functionalization of water-based cosmetic products by sparingly water-soluble components can be realized in water-based cosmetic product applications in which usage quantities of surfactants such as emulsifying agents and solubilizing agents are restricted, and this invention is therefore extremely useful.