Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2000-02-02
2001-04-03
Reamer, James H. (Department: 1614)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S450000, C514S529000, C514S938000
Reexamination Certificate
active
06210693
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to an oil-in-water (O/W) emulsion composition which is primarily used as a composition for external use. More particularly, the present invention relates to an O/W emulsion composition in which a vitamin A fatty acid ester is stabilized.
2. Background Art
Vitamin A and vitamin A fatty acid esters have conventionally been known as effective ingredients for prevention and therapy of keratinization of the skin and retardation of and restoration from aging of the skin. Thus, vitamin A and vitamin A fatty acid esters are incorporated into a variety of external-use compositions formulated for these purposes.
However, vitamin A and vitamin A fatty acid esters are inherently very unstable. That is, they are easily degraded when they undergo isomerization or oxidation evoked by any of a number of factors, such as light, air, heat, and metal ions. Therefore, external-use compositions containing vitamin A or vitamin A fatty acid esters exhibit unsatisfactory stability over time and in addition have drawbacks such as need for particularly careful attention to storage conditions.
Among such unstable vitamin A and vitamin A fatty acid esters, vitamin A has already been a target of a variety of means for stabilization in an external-use composition. Among such means, use of a chelating agent and use of an antioxidant have been proposed.
As compared with vitamin A, fatty acid esters of vitamin A exhibit excellent stability against oxidation, and yet, due to their chemical structure, the fatty acid esters are prone to hydrolysis. Stabilization methods typified by the above methods can improve stability of vitamin A fatty acid esters against oxidation, but cannot improve stability against the problematic hydrolysis.
Accordingly, an object of the present invention is to provide means for enhancing the stability of fatty acid esters of vitamin A against hydrolysis.
DISCLOSURE OF THE INVENTION
In an attempt to attain the above-mentioned objective, the present inventors have carried out extensive studies in search for effective means for stabilizing vitamin A fatty acid esters contained in an O/W emulsion composition, and have found that the objective can be attained by the provision of means for preventing oxidation of vitamin A fatty acid esters together with means for preventing hydrolysis of vitamin A fatty acid esters, thus leading to completion of the present invention.
Accordingly, the present invention provides an O/W emulsion composition containing a vitamin A fatty acid ester, which composition comprises means for preventing oxidation of the vitamin A fatty acid ester together with means for preventing hydrolysis of the vitamin A fatty acid ester.
According to the present invention, the O/W emulsion composition of the present invention can be divided into two cases, depending on the form of the composition: essences and creams.
In the case in which the O/W emulsion composition of the present invention assumes the essence form, the present inventors have found that the aforementioned objective can be attained by incorporating an antioxidant into the oil phase of the composition and also incorporating, as means for preventing hydrolysis of a vitamin A fatty acid ester, a hydrophilic nonionic surfactant or nonionic amphipathic substance under specific conditions.
Thus, the present invention also provides an O/W emulsion composition which assumes, inter alia, an essence form and which comprises means for preventing oxidation of a vitamin A fatty acid ester and means for preventing hydrolysis of the vitamin A fatty acid ester, wherein the means for preventing hydrolysis of the vitamin A fatty acid ester comprises a limited amount of a hydrophilic nonionic surfactant, or, a nonionic amphipathic polymer having a molecular weight of 5,000 or more.
In the case in which the O/W emulsion composition of the present invention assumes the cream form, the present inventors have found that the aforementioned objective can be attained by incorporating an antioxidant into the oil phase of the composition and also incorporating, as means for preventing hydrolysis of a vitamin A fatty acid ester, an amphipathic substance and a hydrophilic nonionic surfactant under specific conditions.
Thus, the present invention also provides an O/W emulsion composition which assumes, inter alia, a cream form and which comprises means for preventing oxidation of a vitamin A fatty acid ester and means for preventing hydrolysis of the vitamin A fatty acid ester, wherein the means for preventing hydrolysis of the vitamin A fatty acid ester comprises an amphipathic substance and a hydrophilic nonionic surfactant, the amphipatic substance and the hydrophilic nonionic surfactant being incorporated into the composition under the following conditions 1) through 3):
1) the gel transition temperature in a three-phase system consisting of the amphipathic substance, the hydrophilic nonionic surfactant, and water is 50° C. or higher;
2) the ratio by weight of the amphipathic substance to the hydrophilic nonionic surfactant is 0.5 or more; and
3) the total amount of all surfactants incorporated into the composition is 5.0% by weight or less with respect to the entirety of the composition.
As used herein, I.O.B. (Inorganic/Organic Balance) value serves as a basis for calculation of &Sgr; I.O.B. value, which is a factor that determines characteristics of the O/W emulsion composition of the present invention, and signifies an index representing the polarity of an oily component. Briefly, I.O.B. represents the ratio of an inorganic value of an oily component to an organic value of the oily component [note: the ratio is calculated as follows: an organic value of 20 is assigned for each carbon atom in the molecule of the oily component, and an inorganic value of 100 is assigned per hydroxyl group in the molecule of the oily component, and these values are used as yardsticks for calculation of an inorganic value of another substituent (inorganic group); see (1) “Organic Analysis” authored by Fujita (1930), published by Kaniya Shoten, (2) “Prediction of Organic Compounds and Organic Conceptional Diagram (Kagaku-no-Ryoiki 11-10)” (1957), pp.719-725, authored by Fujita, (3) “Systematic Organic Qualitative Analysis (Book of Purified Substances)” (1970), p.487, authored by Fujita and Akatsuka, published by Kazama Shoten, (4) “Organic Conceptional Diagram, Its Fundamentals and Applications” (1984), p.227, authored by Koda, published by Sankyo Shuppan, (5) “Design of Emulsion Formulations by use of Organic Conceptional Diagram” (1985), p.98, authored by Yaguchi, published by Nippon Emulsion K. K., and (6) R. H. Ewell, J. M. Harrison, L. Berg.: Ind. Eng. Chem. 36, 871 (1944)], and is expressed by:
I.O.B.=<inorganic value of the oily component>÷<organic value of the oily component>.
In the present invention, the &Sgr; I.O.B. value is defined as a summation of I.O.B. values of respective oily ingredients which constitute the oil phase of the emulsion.
Thus, &Sgr; I.O.B. is defined as
&Sgr; I.O.B.=<the inorganic value of the oil phase>÷<the organic value of the oil phase>, wherein the inorganic value of the oil phase is expressed by A×x+B×y+C×z+ . . . (wherein A, B, C, . . . represent inorganic values, on an organic conceptional diagram, of the respective oily ingredients which constitute the oil phase of the emulsion and x, y, z, . . . represent proportions of respective oily ingredients A, B, C, . . . which constitute the oil phase of the emulsion, and x+y+z+ . . . =1), and the organic value of the oily phase is expressed by A′×x+B′×y+C′×z+ . . . (wherein A′, B′, C′, . . . represent organic values, on an organic conceptional diagram, of the respective oily ingredients which constitute the oil phase of the emulsion).
The greater the &Sgr; I.O.B. value, the more prominent the inorganic properties of the oil phase
Inoue Haruhiko
Nakajima Hideo
Okamoto Tohru
Reamer James H.
Shiseido Company Ltd.
Townsend & Banta
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