Cosmetic compositions

Details Cosmetic compositions Cosmetic compositions

2000-04-11

2002-09-24

Dees, Jose′ G. (Department: 1616)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

C424S065000, C424S066000, C424S068000

Reexamination Certificate

active

06455056

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to cosmetic compositions for application to human skin. Significant forms of the invention are concerned with antiperspirant compositions for application to human skin, especially the axilla. However, the invention can also be applied to other forms of cosmetic composition.
BACKGROUND OF THE INVENTION AND SUMMARY OF PRIOR ART
A wide variety of cosmetic compositions for application to human skin make use of a thickened or structured liquid carrier to deliver colour or some other active material to the surface of the skin. A significant example of such cosmetic compositions are antiperspirant compositions which are widely used in order to enable their users to avoid or minimise wet patches on their skin, especially in axillary regions.
Cosmetic compositions have been made in a variety of product forms. One of these is a so-called “stick” which is usually a bar of an apparently firm solid material held within a dispensing container and which retains its structural integrity and shape whilst being applied. When a portion of the stick is drawn across the skin surface a film of the stick composition is transferred to the skin surface. Although the stick has the appearance of a solid article capable of retaining its own shape for a period of time, the material usually has a structured liquid phase so that a film of the composition is readily transferred from the stick to another surface upon contact. Examples of cosmetic compositions which are, or can be, marketed in a stick form are lipsticks, lip salves and eyebrow pencils. The stick form has been used in particular for deodorant and antiperspirant compositions where the composition includes a deodorant active material or an antiperspirant active material respectively.
Another possibility is that a stick is a softer solid composition accommodated in a dispensing container which in use extrudes the composition through one or more apertures.
Antiperspirant sticks and other cosmetic compositions can be divided into three categories. Suspension sticks contain a particulate material, notably a particulate antiperspirant active material, suspended in a structured carrier liquid phase. Emulsion sticks normally have a hydrophilic phase forming an emulsion with a second, more hydrophobic, liquid phase. One of the phases contains an active material. Solution sticks typically have the active material dissolved in a structured liquid phase; this phase may be organic solvent or may be a mixture of water and a water-miscible organic solvent. This classification into suspension, emulsion and solution types can be applied to both firm and soft solid compositions.
Besides firm and soft sticks, a number of cosmetic compositions have taken the form of liquids which are formulated to be somewhat viscous and hence pour and flow more slowly than water. One example is antiperspirant compositions in liquid form, such as applied using a roll-on applicator.
There is substantial literature on the structuring or thickening of cosmetic compositions which is frequently accomplished using some form of thickening agent as part of the composition.
Some compositions have a substantial viscosity, which may even make them capable of retaining their own shape for a time, because of transient interactions between molecules of a thickening agent in the liquid.
This is characteristic of compositions which are thickened with polymers. Thickening can be attributed to interactions between polymer molecules.
It is characteristic of such thickened compositions that their viscosity can be achieved or recovered on standing at room temperature. If subjected to shear their viscosity reduces (hence they are described as shear thinning) but the viscosity recovers towards its original value if the composition is subsequently allowed to stand at room temperature.
Compositions which have two phases, i.e. compositions which are an emulsion or a suspension may also have substantial viscosity, even to the extent of being able to sustain their own shape.
Here too it is characteristic of the composition that—provided the composition is stable—its viscosity will recover spontaneously if it is reduced by subjecting the composition to shear.
Compositions have also been given structure and an enhanced viscosity or rigidity by the incorporation of a structurant (also referred to as a gellant or gelling agent) which causes the liquid to gel upon cooling from an elevated temperature.
Gel formation takes place as an exothermic event within a temperature range referred to as the gel point or gel temperature. Upon reheating, melting of the gel takes place as an endothermic event within a temperature range. When the gel melts, the structurant goes into solution in the liquid. Such gels can be disrupted by shearing and do not recover their viscosity for a long time, if at all unless remelted, although a small partial recovery may be observed.
One material which is well known to form gels is 12-hydroxystearic acid which is discussed in Terech et al “Organogels and Aerogels of Racemic and Chiral 12-hydroxy octadecanoic Acid”, Langmuir Vol 10, 3406-3418, 1994. The material is commercially available from Ajinomoto and from Caschem.
U.S. Pat. No. 5,750,096 and U.S. Pat. No. 5,489,276 are two of several documents which teaches that gelation can be brought about using esters or amides of 12-hydroxystearic acid.
In these documents, especially the latter, there is a proposal to enhance the efficacy of 12-hydroxystearic acid or other gellant by including a “nucleating agent”. A range of possibilities for the nucleating agent are suggested, including esterified sucrose. The only function attributed to that material is to modify or promote the gelating action of another material.
Gelation with a waxy material, especially stearyl alcohol, has been mentioned in a great many documents. WO-A-98/43605 is a recent example.
N-acyl amino acid amides and esters are also known to structure liquids. We have established that they do so by forming fibrous networks. They are described in U.S. Pat. No. 3969087. N-Lauroyl-L-glutamic acid di-n-butylamide is commercially available from Ajinomoto under their designation GP-1.
Further materials which have been disclosed as gelling agents are the amide derivatives of di and tribasic carboxylic acids set forth in WO 98/27954 notably alkyl N,N′dialkyl succinamides.
Yet another example of material which can be used to bring about gelation of a hydrophobic carrier liquid is lanosterol, as described in WO 97/11678 where it is used in the preparation of soft, opaque gels as antiperspirant compositions WO 98/34588 also describes the use of lanosterol as a gellant for oil-based cosmetic compositions.
SUMMARY OF THE INVENTION
We have recognised that when a gel is formed, the solution of the structurant in a liquid may supercool before gelling commences, and in consequence the gel-melting temperature may be higher than the gel-formation temperature. If gel-formation takes place in a quiescent solution of the structurant the extent of supercooling may be substantial. We have observed that it varies from one structurant to another.
However, if the structurant is being used to prepare a product where a constituent such as a disperse phase is mixed into the hot liquid before gel formation, we have found that it is likely to be necessary to carry out this mixing operation at a temperature at which the structurant is fully soluble in the liquid. If an attempt is made to mix the composition at a temperature at which there is some supercooling, it is likely that the mixing will induce gelation to commence.
It is a consequence of this that when preparing structured liquid compositions containing a structurant to gel the liquid, all constituents of the composition must be subjected to a temperature high enough to dissolve the structuring agent.
We have now found that advantageous properties and processing can be provided by utilising as gelling agent an esterified saccharide with has an enthalpy of gelation of at least 45 kilojoule per mole.
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