Antiperspirant compositions

Details Antiperspirant compositions Antiperspirant compositions

2001-01-12

2002-05-14

Dodson, Shelley A. (Department: 1616)

Drug, bio-affecting and body treating compositions

Anti-perspirants or perspiration deodorants

C424S066000, C424S068000, C424S078020, C424S078080, C424S400000, C424S401000

Reexamination Certificate

active

06387358

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to soft solid antiperspirant compositions for application to human skin, especially the axilla.
BACKGROUND OF THE INVENTION AND SUMMARY OF PRIOR ART
Antiperspirant compositions are widely used in order to enable their users to avoid or minimise wet patches on their skin, especially in axillary regions. A variety of these compositions make use of a thickened or structured liquid which is applied to the surface of the skin and serves as a carrier for the antiperspirant active. In many such compositions the liquid is water-immiscible and is thickened or structured by one or more materials incorporated into the composition for that purpose.
Antiperspirant formulations have been provided with a range of different 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. Another possibility is a softer solid composition accommodated in a dispensing container which in use extrudes the composition through one or more apertures.
The present invention is concerned with such soft solid compositions. Such compositions have sufficient rigidity that they are not observed by the human eye to flow, but they are deformable by hand pressure and can be extruded from a container through one or more apertures at the end of the container.
For use a small amount of the composition is extruded from the container, which may then be used as an applicator to spread the extruded material on the skin.
A number of properties of such compositions are significant. The composition should be stable and not leak from its container until deliberately extruded. Its sensory feel when applied should, desirably, not be sticky. The applied film of the composition preferably is of a transparent or translucent appearance rather than an opaque white. This property is referred to as low visible residue, and it is desirable in order that the deposit on the user's skin is not easily seen. Moreover, this also avoids conspicuous marks on clothing, to which the deposited material can accidentally transfer.
Soft solid antiperspirant compositions have been marketed. One commercial product used inorganic silica to thicken a carrier liquid. Some products currently on the market use mixtures of waxes to thicken a hydrophobic carrier liquid mixture. Such a formulation requires some complexity in its production process and careful control of temperature and other parameters at which the composition is put into containers for retail sale. The existing products structured with mixtures of waxes display some syneresis—that is to say weeping of liquid from the body of the composition.
Soft solid antiperspirant compositions with a continuous phase provided by water-immiscible liquid have also been disclosed in U.S. Pat. No. 5,635,165 (Panitch/Helene Curtis). The teaching of this document is that the structuring of antiperspirant compositions can be accomplished using either a sterol, such as lanosterol or a starch hydrolysate ester, such as dextrin palmitate.
The document states that to achieve the full advantage of its invention, a fatty alcohol should be included in an amount from 1 to 15% by weight of the composition, to adjust firmness and increase phase stability.
The examples in this document show two approaches to formulation. One is to use dextrin palmitate alone, or sterols alone, in an amount of 8% or more by weight of the composition. The alternative approach is to use a much smaller amount of such structuring agent accompanied by a larger amount of a fatty alcohol which is solid at room temperature of 20 C. One example [Ex 6] uses 1% dextrin palmitate with 2.8% sucrose distearate and 5.7% behenyl alcohol. Another example [Ex 16] uses 1% of a mixture of lanosterol and dihydrolanosterol, together with 1.25% sucrose distearate and 10% of behenyl alcohol. This document does not attempt to use lanosterol/dihydro-lanosterol jointly with dextrin palmitate and we have found that it would be impossible to do so. Lanosterol/dihydrolanosterol gives unstable compositions except with a restricted selection of carrier liquids (this is the subject of a copending application) but these liquids are such poor solvents for dextrin palmitate that it cannot be used to thicken them.
The thickening of organic liquids with polyamides in order to make antiperspirant compositions has been disclosed in U.S. Pat. No. 5,500,209. Typically, compositions exemplified in this document are thickened with 15% or more of thickening polymer, and are emulsions in which the antiperspirant active is dissolved in water or hydrophilic solvent.
U.S. Pat. No. 5,846,520 (Procter & Gamble) discloses compositions structured with a 12-hydroxystearic acid as a gelling agent. The document acknowledges that soft solid compositions may be made, although it prefers (and exemplifies) firm sticks. The document mentions possible optional components including waxes and fatty acid esters to be used in small percentages as nucleating agents.
12-hydroxystearic acid (12-HSA) is an example of materials which cause gelation by forming a network of fibres within the composition as it cools from a heated state during processing.
These materials can be used to make rigid sticks, as taught in U.S. Pat. No. 5,846,520 and other documents. However, we have found that if such a structurant is used to make a soft solid, the viscosity or hardness of the soft solid composition is very sensitive to small changes in the concentration of gelling agent, which is a potential difficulty when scaling up to commercial production. Also, complex processing is required similar to that required in making existing wax-structured soft solid products.
U.S. Pat. No. 5,480,637 (Dow Corning) used 12-hydroxystearic acid, together with an alkyl siloxane polymer or copolymer as a gelating system in order to produce solid products described as “firm” and “rigid”. The examples use a range of alkyl methyl siloxane polymers but always at a concentration of only 1% by weight of the composition.
SUMMARY OF THE INVENTION
We have now found that advantageous soft solid antiperspirant compositions can be prepared by using a combination of a polymeric thickener and a second structurant in specified amounts which overall predominate over the amount (if any) of fatty alcohol which is solid at room temperature of 20° C.
Therefore, in a first aspect, this invention provides a soft solid antiperspirant composition having a continuous phase which contains water-immiscible liquid, and contains:
i) 1.5 to 15%, preferably 1.5 to 10% by weight of the composition, of an organic polymeric thickener which is effective to increase the viscosity of the water-immiscible liquid;
ii) 0.5 to 15%, preferably 0.5 to 10%, by weight of the composition, of second structuring material selected from the group consisting of
a) structurant which forms a network of fibres within the continuous phase,
b) waxes, other than fatty alcohols, which are solid at temperatures of 30° C. and below, but melt below 95° C., and
c) mixtures thereof; and a particulate antiperspirant active in suspension in said continuous phase.
It will be appreciated that compositions according to this invention contain at least two materials serving to thicken/structure the composition.
In many instances the total amount of the organic polymeric thickener and second structuring material will be greater than the total amount of any fatty alcohol which is solid at 20° C.
If structurant (a) which forms a network of fibres within the continuous phase is present, the amount of it will generally be from 0.5 to 7% by weight of the composition.
If wax (b) is present the amount of it will generally be from 0.5 to 15% by weight of the composition.
A composition of this invention will generally be marketed in a container by means of which it can be applied at time of use. This container may be of conventional type.
A second aspect of the invention therefore pro

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