Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2000-01-05
2002-10-15
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S400000, C424S078030, C424S450000, C514S873000, C514S937000, C514S938000
Reexamination Certificate
active
06464990
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a nanoemulsion based on a surfactant having polyethylene oxide and polypropylene oxide blocks and on 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 present invention also relates to a process for the preparation of the nanoemulsion and to its uses in the cosmetics, dermatological and/or ophthalmological fields. This nanoemulsion is stable on storage and can comprise large amounts of oil while retaining good transparency and while having good cosmetic properties.
2. Description of the Background
Nanoemulsions are oil-in-water emulsions, the oil globules of which have a very fine particle size, that is to say 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 uniquely different 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; they are transparent solutions of micelles swollen by oil, which oil is generally a very-short-chain oil such as 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 because of 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 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.
In addition, nanoemulsions are known in the art which comprise an amphiphilic lipid phase composed of phospholipids, water and oil. These emulsions exhibit the disadvantage of being unstable on storage at conventional storage temperatures, i.e., from 0 to 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 problematic to prepare. Furthermore, the nanoemulsions obtained exhibit a waxy and film-forming feel which is not very pleasant for the user.
Furthermore, EP 0 728 460 discloses nanoemulsions which are based on fluid non-ionic amphiphilic lipids. However, these nanoemulsions exhibit the disadvantage of having a sticky effect during application to the skin. A need, therefore, continues to exist for nanoemulsions which have neither the disadvantages of those of the prior art nor the disadvantages of microemulsions.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a nonoemulsion which exhibits all of the advantages of known nanoemulsions without their disadvantages.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a nanoemulsion comprising an oily phase dispersed in an aqueous phase and having oil globules with a number-average size of less than 100 nm, which dispersion is facilitated by a surfactant comprised of polyethylene oxide and polypropylene oxide blocks, the oily phase comprising at least one oil having a molecular weight of greater than 400 and wherein the ratio by weight of the amount of oily phase to the amount of surfactant ranges from 2 to 10.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The nanoemulsions of the invention generally have a transparent to bluish appearance. Their transparency is measured by a transmittance coefficient at 600 nm ranging from 10 to 90% or else by a turbidity ranging from 60 to 600 NTU, preferably from 70 to 300 NTU, which turbidity is measured with a Hach Model 2100 P portable turbidimeter.
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, more preferably from 40 to 60 nm. 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 can be used in the nanoemulsion of the invention is selected from ethylene oxide and propylene oxide block copolymers, and their mixtures, and, preferably, the nanoemulsion of the invention is devoid of any surfactant other than ethylene oxide and propylene oxide block copolymers.
The ethylene oxide and propylene oxide block copolymers which can be used as surfactant in the nanoemulsion of the invention can be selected, in particular, from the block copolymers of formula (I):
HO(C
2
H
4
O)
x
(C
3
H
6
O)
y
(C
2
H
4
O)
z
H (I)
wherein x, y and z are integers such that x+z ranges from 2 to 100 and y ranges from 14 to 60, and their mixtures, and more particularly from the block copolymers of formula (I) having an HLB ranging from 2 to 16.
These block copolymers can be selected, in particular, from poloxamers and in particular from Poloxamer 231, such as the product sold by ICI under the name Pluronic L81, of formula (I) where x=z=6 and y=39 (HLB 2); Poloxamer 282, such as the product sold by ICI under the name Pluronic L92, of formula (I) where x=z=10 and y=47 (HLB 6); and Poloxamer 124, such as the product sold by ICI under the name Pluronic L44, of formula (I) where x=z=11 and y=21 (HLB 16).
The amount of surfactant in the nanoemulsion of the invention can range, for example, from 0.2 to 15% by weight, preferably from 1 to 8% by weight with respect to the total weight of the nanoemulsion.
The ratio by weight of the amount of the oily phase to the amount of surfactant ranges from 2 to 10, preferably from 3 to 6. The term
amount of oily phase
is understood here to mean the total amount of the constituents of this phase without including the amount of surfactant.
The nanoemulsion of the invention comprises at least one oil with a molecular weight of greater than 400. Oils with a molecular weight of greater than 400 can be selected from oils of animal or vegetable origin, mineral oils, synthetic oils and silicone oils, and their mixtures. Suitable oils of this type, of, for example, include isocetyl palmitate, isocetyl stearate, avocado oil and jojoba oil.
In addition, the oily phase can optionally comprise other oils and, in particular, oils having a molecular weight of less than 400. These oils are also selected from oils of animal and vegetable origin, mineral oils, synthetic oils and silicone oils. Suitable oils with a molecular weight of less than 400 include isododecane, isohexadecane, volatile silicone oils, isopropyl myristate, isopropyl palmitate and C
11
-C
13
isoparaffin.
The oily phase can also comprise fatty substances other than the oils indicated above, such as fatty alcohols, for example stearyl, cetyl and behenyl alcohols, fatty acids, for example stearic, palmitic and behenic acids, oils of the fluorinated type, waxes, gums and their mixtures.
The nanoemulsions of the invention comprise an amount of oily phase preferably ranging from 2 to 40% and better still from 5 to 30% by weig
Legret Sylvie
Simonnet Jean-Thierry
Sonneville Odile
Evans Charesse
L'Oreal
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Page Thurman K.
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