Antiperspirant compositions

Details Antiperspirant compositions Antiperspirant compositions

2000-04-12

2001-05-15

Dodson, Shelley A. (Department: 1616)

Drug, bio-affecting and body treating compositions

Anti-perspirants or perspiration deodorants

C424S066000, C424S068000, C424S400000, C424S401000

Reexamination Certificate

active

06231841

ABSTRACT:

TECHNICAL FIELD
The present invention relates to antiperspirant compositions and in particular to thickened or structured compositions.
BACKGROUND AND PRIOR ART
Topically applied antiperspirant compositions are in widespread use throughout much of the world, in order to enable their users to avoid or minimise visible wet patches on their skin, especially in axillary regions. Antiperspirant formulations have been applied using a range of different applicators, including aerosols, roll-ons, pump sprays, sticks and mushroom applicators, in accordance with the individual preferences of consumers. In some parts of the world, sticks are especially popular. The term stick traditionally indicates a bar of solid material which was usually housed within a dispensing container and which retains its integrity whilst being applied, a firm stick. When a portion of a firm stick is drawn across the skin surface, a film of the stick composition is transferred onto the skin surface. Although the stick has the appearance of a solid article, the material forming the stick usually comprises a structured liquid phase such that a film of the material is readily transferred onto another surface upon contact under pressure.
More recently, the term has been applied to soft solids, which have an apparent solid form during storage, but which flow under mild pressure or shear, so that in use they can be extruded through an aperture or apertures onto a dispensing surface. Soft solids retain their shape for at least 30 seconds if removed under non-shear/stress conditions from a container, but if subjected to shear or stress, their structure is destroyed and no more than a minor fraction of the structure can be reformed within a period of about 24 hours when the shear/stress is removed.
There are typically three classes of antiperspirant sticks, namely suspension sticks, emulsion sticks and solution sticks. Suspension sticks contain a particulate antiperspirant active material suspended in a structured carrier. Emulsion sticks normally comprise an emulsion of an oil phase and a hydrophilic phase containing the antiperspirant active in solution, the continuous phase being structured. In some emulsion sticks, the continuous phase is an oil phase. In solution sticks, the antiperspirant is typically dissolved in the liquid carrier phase which is structured. The liquid phase can comprise water and/or a water-miscible organic solvent. The three categories can be applied to sticks of both firm and soft solids compositions.
Conventionally, many sticks have been structured using naturally-occurring or synthetic waxes, of which typical examples include stearyl alcohol, and hydrocarbon waxes or silicone waxes. Waxes are widely available, and by suitable selection of the waxes themselves and their concentrations in the formulation can effectively obtain either a soft solid or a firm solid. Thus for example, wax-structured sticks are described in an article in Cosmetics and Toiletries, 1990, vol 105, p75-78. However, fatty alcohol or wax structured sticks tend to leave visible white deposits on application to human skin, and the deposits can also be transferred onto clothing by physical contact with the skin. A significant, and possibly growing, proportion of consumers of antiperspirants have indicated displeasure at visible deposits. Accordingly, the antiperspirant industry, including the instant inventors, is devoting considerable time and resources to finding means to ameliorate or overcome the customer perception of whiteness deposits.
A number of alternative structurants to waxes have been proposed. The term “gellant” is often employed instead of “structurant”. Where the resultant product is a liquid of increased viscosity rather than a solid or gel, the term “thickener” can also be used. For example, the use of dibenzylidene sorbitol (DBS) or derivatives thereof has been proposed as gellant in a number of publications, such as EP 0512770, WO 92/19222, U.S. Pat. Nos. 4,822,602 and 4,725,430. Formulations containing such gellants can suffer from a number of disadvantages, including instability in the presence of acidic antiperspirants, and comparatively high processing temperatures needed in the production of sticks. Some of such formulations containing such gellants are sticky or tacky.
A combination of an n-acylaminoacid amide and 12-hydroxystearic acid to gel a non-aqueous formulation is described in WO 93/23008 and U.S. Pat. No. 3,989,087. However, high processing temperatures are needed to dissolve the gellants and prevent premature gelling. When applied to the skin the formulation can be difficult to wash off, reformulation to overcome the latter problem can be made impossible by the need for high processing temperature.
In WO 97/11678 to Helene Curtis, Inc, there is described the use of a sterol and particularly lanosterol as gellant, sometimes in conjunction with a starch hydrolyzate derivative for antiperspirant compositions.
In WO 98/34588 to Lancaster Group GmbH, there is described the use of lanesterol as a gellant for oil-based cosmetic compositions, containing a cosmetic active material, of which one listed material is a deodorant, though not exemplified.
OBJECTS OF THE INVENTION
It is an object of the present invention to ameliorate or overcome one or more of the foregoing disadvantages of structured sticks. A particular object of the invention, in at least one aspect, comprises providing a stick exhibiting low visible deposits gelled by a non-wax system.
SUMMARY OF THE INVENTION
According to the present invention there is provided an antiperspirant composition comprising an antiperspirant active, a liquid carrier and a structurant including a sterol to thicken or solidify the composition characterised in that the structurant comprises an effective concentration of a combination of at least one sterol and at least one sterol ester.
The combination of the sterol and the sterol ester in a suitable mole ratio enables the hydrophobic liquid carrier in the antiperspirant formulation to be structured effectively and in a readily controllable manner. The invention combination of gellants, a twin gellant system, has demonstrated superior gelation in comparison with either constituent. Without being bound to any specific theory or explanation as to why the combination is so effective, it is believed that the sterol and sterol ester constituents stack with each other to form a network of strands, the stacking possibly being regular. The presence of both constituents in the stacking appears to encourage the growth of the strands and result in a network which is superior to that from either constituent alone.
The employment of the twin gellant system can avoid or at least ameliorate a potential problem of premature gelation which can sometimes arise if a single gellant system is employed, for example by controlling the manner and timing in which the two components of the twin gellant system are mixed with the phase to be gelled.
DETAILED DESCRIPTION OF THE INVENTION
The invention formulation comprises as essential constituents
a) a sterol/sterol ester gellant system in addition to;
b) an antiperspirant active and
c) a liquid carrier
The sterol/sterol ester gellant system comprises the sterol and sterol ester in a mole ratio that is normally selected in the range of from 10:1 to 1:10, especially from 6:1 to 1:4 and preferably in the range of from 3:1 to 1:2. Employment of the two system constituents within such a mole ratio range, and especially within the preferred range facilitates the co-stacking of the constituents and consequently facilitates the formation of a network that is readily able to structure the formulation.
The invention twin gellant system is desirably present at a concentration of greater than 0.5%, and preferably greater than 1%. It is normally present at a concentration of up to 20%, and in many preferred embodiments of not more than 15%. Concentrations herein are expressed by weight based on the formulations, unless explicitly otherwise stated, be they for the gellant system or some other con

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