Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
1999-12-29
2002-04-23
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S400000, C514S844000, C514S845000, C514S937000, C514S938000
Reexamination Certificate
active
06375960
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nanoemulsion based on a surfactant which is solid at a temperature of less than or equal to 45° C., which surfactant is chosen from ethoxylated fatty ethers and ethoxylated fatty esters, and at least one oil having a molecular weight of greater than 400, the ratio by weight of the amount of oily phase to the amount of surfactant ranging from 2 to 10.
The invention also relates to a process for the preparation of the nanoemulsion and to its uses in the cosmetics, dermatological and/or ophthahnological fields. This nanoemulsion is stable on storage and can contain large amounts of oil while retaining good transparency and while having good cosmetic properties.
2. Discussion of the Background
Nanoemulsions are oil-in-water emulsions, the oil globules of which have a very fine particle size, i.e. a number-average size of less than 100 nm. They are generally manufactured by mechanical fragmentation of an oily phase in an aqueous phase in the presence of a surfactant. In the case of nanoemulsions, the very small size of the oily globules is obtained in particular by virtue of at least one pass through a high-pressure homogenizer. The small size of the globules confers on them cosmetically advantageous properties which distinguish them from conventional emulsions: they are transparent and exhibit a novel texture. They can also carry active principles more efficiently.
Transparent microemulsions are known in the art. In contrast to nanoemulsions, microemulsions are not, strictly speaking, emulsions. Rather, microemulsions are transparent solutions of micelles swollen by oil, which oil is generally a very-short-chain oil (e.g. hexane or decane) and is solubilized by virtue of the joint presence of a significant amount of surfactants and of cosurfactants which form the micelles. The size of the swollen micelles is very small owing to the small amount of oil which they can solubilize. This very small size of the micelles is the cause of their transparency, as with nanoemulsions. However, in contrast to nanoemulsions, microemulsions are spontaneously formed by mixing the constituents, without contributing mechanical energy other than simple magnetic stirring. The major disadvantages of microemulsions are related to their necessarily high proportion of surfactants, leading to intolerance and resulting in a sticky feel during application to the skin. Furthermore, their formulation range is generally very narrow and their temperature stability very limited.
Nanoemulsions, which contain an amphiphilic lipid phase composed of phospholipids, water and oil, are known in the art. These emulsions exhibit the disadvantage of being unstable on storage at conventional storage temperatures, namely between 0 and 45° C. They lead to yellow compositions and produce rancid smells which develop after several days of storage.
Nanoemulsions stabilized by a lamellar liquid crystal coating, obtained by the combination of a hydrophilic surfactant and of a lipophilic surfactant, are also known. However, these combinations are difficult to prepare. Furthermore, the nanoemulsions obtained exhibit a waxy and film-forming feel, which is not very pleasant,for the user.
EP-A-728,460 discloses nanoemulsions based on fluid non-ionic amphiphilic lipids. However, these nanoemulsions exhibit the disadvantage of having a sticky effect during application to the skin.
The need therefore remains for nanoemulsions which have neither the disadvantages of known nanoemulsions not the disadvantages of microemulsions.
SUMMARY OF THE INVENTION
It has now been found that, surprisingly, that the use of a surfactant which is solid at a temperature of less than or equal to 45° C., which surfactant is chosen from ethoxylated fatty ethers and ethoxylated fatty esters and mixtures thereof, and of at least one oil having a molecular weight of greater than 400 (=400 grams per mole) makes it possible to obtain novel nanoemulsions exhibiting all the advantages of known nanoemulsions without their disadvantages.
Accordingly, the first embodiment of the present invention relates to a nanoemulsion that includes:
an oily phase dispersed in an aqueous phase; and
at least one surfactant that is solid at a temperature of less than or equal to 45° C. and which is selected from the group including ethoxylated fatty ethers and ethoxylated fatty esters, and mixtures thereof; wherein
the oily phase includes oil globules having a number-average size of less than 100 nm;
wherein the oily phase includes at least one oil having a molecular weight of greater than 400; and
wherein a weight ratio of the oily phase to the surfactant ranges from 2 to 10.
Another embodiment of the present invention relates to a composition selected from the group including a topical composition, an ophthalmic vehicle, a pharmaceutical composition, dermatological composition, a cosmetic, and an opthalmological composition, and mixtures thereof, that includes the above-noted nanoemulsion.
Another embodiment of the present invention relates to a method of caring for, treating and/or making up the skin, face and/or scalp, that includes applying to the skin, face and/or scalp the above-noted nanoemulsion.
Another embodiment of the present invention relates to a method of caring for and/or treating the hair, that includes applying to the hair the above-noted nanoemulsion.
Another embodiment of the present invention relates to a method of caring for and/or moisturizing the skin, mucous membranes and/or scalp, that includes applying to the skin, mucous membranes and/or scalp the above-noted nanoemulsion.
Another embodiment of the present invention relates to a process for preparing the above-noted nanoemulsion, that includes:
mixing an aqueous phase and an oily phase with stirring at temperature ranging from 10 to 80° C. to form a mixture; and
homogenizing the mixture at a pressure ranging from 6×10
7
Pa to 18×10
7
Pa.
DETAILED DESCRIPTION OF THE INVENTION
Various other objects, features and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description of the preferred embodiments of the invention.
The nanoemulsions according to the invention preferably have a transparent to bluish appearance. Their transparency is measured by a transmittance coefficient at 600 nm ranging from 10 to 90%, more preferably 20 to 85% or else by a turbidity preferably ranging from 60 to 600 NTU and more preferably from 70 to 300 NTU, which turbidity is measured with a Hach Model 2100 P portable turbidimeter. These ranges include all values and subranges therebetween.
The oil globules of the nanoemulsions of the invention have a number-average size of less than 100 nm, preferably ranging from 20 to 75 nm and more preferably from 40 to 60 nm. These ranges include all values and subranges therebetween. The decrease in the size of the globules makes it possible to promote the penetration of the active principles into the surface layers of the skin (carrier effect).
The surfactant which is solid at a temperature of less than or equal to 45° C. is preferably an ethoxylated fatty ether or an ethoxylated fatty ester or their mixtures. According to a more preferred embodiment of the invention, the nanoemulsion contains only one or more of a surfactant chosen from these ethers or esters, and most preferably is devoid of any surfactant other than ethoxylated fatty ethers and ethoxylated fatty esters.
The ethoxylated fatty ethers which are solid at a temperature of less than or equal to 45° C. which can be used as surfactants in the nanoemulsion according to the invention are preferably ethers formed of 1 to 100 ethylene oxide units and of at least one fatty alcohol chain having from 16 to 22 carbon atoms. The fatty chain of the ethers can be chosen in particular from behenyl, arachidyl, stearyl or cetyl units and their mixtures, such as cetearyl. Mention may be made, by way of preferred examples of ethoxylated fatty ethers
Legret Sylvie
Simonnet Jean-Thierry
Sonneville Odile
Evans Charesse
L'Oreal
Page Thurman K.
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