Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2001-01-22
2003-05-13
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S070100, C424S070700, C424S070110, C424S070120, C424S070270, C424S070280, C424S061000, C424S450000, C424S489000
Reexamination Certificate
active
06562356
ABSTRACT:
The present invention relates to O/W (oil-in-water) nanoemulsions comprising oil globules with an average size of less than 150 nm comprising at least one oil, at least one amphiphilic lipid, and at least one PEG (poly ethylene glycol) derivative chosen from specific PEG esters and PEG ethers. The present invention also relates to the use of such nanoemulsions in topical application, for example, in cosmetics and/or in dermopharmacy.
The term “nanoemulsion” means a metastable oil-in-water emulsion (wherein, for example, the emulsion can comprise an oily phase dispersed in an aqueous phase) whose oil globule size is less than 150 nm, these oil globules being stabilized with a crown of amphiphilic lipids which can optionally form a liquid crystal phase of lamellar type located at the oil/aqueous phase interface. The transparency of these emulsions derives from the small size of the oil globules, wherein said small size can be obtained for example by using a high-pressure homogenizer. Nanoemulsions are to be distinguished from microemulsions by their structure. Microemulsions are thermodynamically stable dispersions comprising micelles of at least one amphiphilic lipid swollen with oil. Furthermore, microemulsions do not require considerable mechanical energy to be prepared. They form spontaneously simply by placing the constituents in contact. At least one possible drawback of microemulsions can be associated with the presence of a high proportion of surfactants, which may tend to lead to intolerance and entailing a sticky feel when applied to the skin. Moreover, their field of formulation is generally narrow and their temperature stability can be limited.
The at least one (as used throughout herein above and below, the expression “at least one” means one or more and thus includes individual components as well as mixtures/combinations) amphiphilic lipid is present in an amphiphilic lipid phase, which comprises at least one amphiphilic lipid chosen from for example nonionic and ionic amphiphilic lipids. The expression “amphiphilic lipid” means any molecule of bipolar structure comprising at least one hydrophobic portion and at least one hydrophilic portion having the property of reducing the surface tension of water (g<55 mN/m) and of reducing the interface tension between water and an oily phase. The synonyms of amphiphilic lipid are, for example: surfactant, surface agent, and emulsifier.
The prior art discloses nanoemulsions comprising an amphiphilic lipid phase comprising phospholipids, a cationic lipid, water and al hydrophobic sunscreen. They are obtained by a high-pressure homogenization process. These nanoemulsions can have at least one drawback, for example, such nanoemulsion s may tend to be unstable on storage at the conventional storage temperatures, i.e., between 0° C. and 45° C. Such nanoemulsions may lead to yellow compositions and may produce unpleasant odors, which may develop after a few days of storage. Furthermore, such nanoemulsions tend to exhibit less favorable cosmetic properties. They are described in the “DCI” review of April 1996, pages 46-48, the disclosure of which is incorporated by reference herein.
Moreover, documents EP-A-728 460 and EP-A-780 114, the disclosures of which are incorporated by reference herein, disclose nanoemulsions based on fluid nonionic amphiphilic lipids and on silicone surfactants.
However, all these nanoemulsions are fluid. For certain uses, products are sought which can be measured out and taken up easily by hand. To do this, these products must have a certain level of consistency or viscosity. Specifically, a liquid product may be more difficult to measure out and tends to run easily between the fingers.
It is known practice to use, as thickeners for aqueous media, water-soluble or water-dispersible polymers, such as optionally crosslinked polymers for example polycarboxyvinylic acids, such as carbopol, wherein said polymers can have a long chain length and a high molecular weight.
When such polymers are used in compositions in the form of nanoemulsions, some of such nanoemulsions may tend to exhibit a decrease in at least one characteristic, such as stability and transparency.
Thus, there is still a need for a thickening system which can conveniently thicken, or even gel, a composition in the form of an oil-in-water nanoemulsion, while minimizing any possible influence that it may have on the cosmetic properties of said compositions.
The inventors have discovered, unexpectedly, that oil-in-water nanoemulsions comprising oil globules with an average size of less than 50 nm comprising at least one oil, and at least one amphiphilc lipid can be thickened with at least one PEG (poly ethylene glycol) derivative chosen from specific PEG esters and PEG ethers.
One subject of the present invention is oil-in-water nanoemulsions comprising oil globules with an average size of less than 150 nm comprising at least one oil, at least one amphiphilc lipid, and at least one PEG (poly ethylene glycol) derivative chosen from specific PEG esters and PEG ethers defined below, wherein the weight ratio of the amount of said at least one oil to the amount of said at least one amphiphilic lipid ranges for example from 1:1 to 10:1, such as for example from 1.2:1 to 6:1.
Another subject of the invention is a process for thickening oil-in-water nanoemulsions comprising oil globules with an average size of less than 150 nm comprising at least one oil and at least one amphiphilc lipid comprising including at least one PEG (poly ethylene glycol) derivative chosen from specific PEG esters and PEG ethers defined below in said nanoemulsions.
As a non-restrictive explanation, it may be considered that, in the context of the invention, the increase in the viscosity of the medium may result from the formation of a network of oil particles, said network involving combinations of hydrophobic type between, on the one hand, the hydrophobic groups of the polymer and, on the other hand, the hydrophobic cores of the oil particles. The existence of labile bonds between the particles may be responsible in part for increasing the viscosity of the mixture.
The nanoemulsions in accordance with the invention are prepared at temperatures ranging for example from 4° C. to 45° C. and are compatible with heat-sensitive active agents. If desired, the nanoemulsions can comprise large amounts of oil. Such nanoemulsions can for example comprise large amounts of fragrance and can improve their remanence. They can also promote the penetration of the active agents into the superficial layers of the skin and the deposition of active agent onto keratin fibres such as the hair. Hair treated with these nanoemulsions may be at least one of the following: shiny, while simultaneously avoiding a greasy look or feel, softer and more lively in nature, while also tending to disentangle easily.
The cosmetic composition, such as for example a hair composition, obtained by comprising the nanoemulsions of the present invention may spread easily, may be easier to handle and may be removed satisfactorily by rinsing.
The at least one PEG (poly ethylene glycol) derivative chosen from PEG esters and PEG ethers can be, for example, chosen from compounds of formula (I):
R
1
—(O—CH
2
—CH
2
)
n
—OR
2
(I)
in which:
R
1
is chosen from linear and branched, saturated and unsaturated alkyl groups comprising from 8 to 30 carbon atoms and linear and branched, saturated and unsaturated acyl groups comprising from 8 to 30 carbon atoms,
R
2
is chosen from a hydrogen atom, linear and branched, saturated and unsaturated alkyl groups comprising from 1 to 30 carbon atoms, and linear and branched, saturated and unsaturated acyl groups comprising from 1 to 30 carbon atoms, and
n is a number ranging from 80 to 350.
In one embodiment, R
1
can be for example chosen from acyl groups comprising from 12 to 20 carbon atoms. In another embodiment, R
2
can be for example chosen from acyl groups comprising from 12 to 20 carbon atoms. In yet another embodiment, n can be for example a number ranging from 100 to 30
Aubrun Odile
Cazin Benedicte
Douin Véronique
Simonnet Jean-Thierry
Verite Claude
Finnegan Henderson Farabow Garrett & Dunner LLP
Howard S.
L'Oreal (S.A.)
Page Thurman K.
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