Antiperspirant compositions

Details Antiperspirant compositions Antiperspirant compositions

2001-07-10

2002-05-21

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

06391291

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to antiperspirant compositions with sufficient rigidity to sustain their own shape. The usual form of such compositions is a stick.
BACKGROUND OF THE INVENTION
Topically applied antiperspirant compositions are in widespread use throughout much of the world, in order to enable their users to avoid or minimise wet patches on their skin, especially in axillary regions. Antiperspirant formulations have been applied using a range of different applicators depending on the individual preferences of consumers, including aerosols, roll-ons, pump sprays, sticks and so-called mushroom applicators which are used to apply cream formulations. In some parts of the world, sticks are especially popular. The term stick traditionally indicates a bar of material with a solid appearance which is usually housed 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.
For use, the stick is applied directly to the skin of the user. This contrasts with soft solid compositions which exist as a stick within their container but for use a portion is extruded from the container through apertures which have smaller cross section than the body of composition which is being made to flow out through these apertures.
Antiperspirant sticks have been made with a variety of different types of composition. Suspension sticks contain a particulate antiperspirant active suspended in a structured carrier material which is generally water-immiscible and may well be anhydrous. Solution sticks have the antiperspirant active dissolved in a structured carrier which is polar and may be aqueous or may be based on a non-aqueous polar solvent such as ethanol. A third form of stick is an emulsion of two phases where the continuous phase is structured so that the composition is able to sustain its own shape, the antiperspirant active being dissolved in the more polar of the two phases present. In some emulsion sticks the antiperspirant active is dissolved in an aqueous disperse phase while the continuous phase is a liquid water-immiscible phase so that the composition can be classified as a water-in-oil emulsion. The classification into suspension, emulsion and solution types can be applied to both firm and soft solid compositions.
There is substantial literature on the structuring or thickening of antiperspirant compositions which is frequently accomplished using some form of thickening agent as part of the composition.
It has been common practice for sticks to be structured by incorporating fatty alcohol into the composition, often accompanied by a smaller amount of castor wax. Sticks which are structured with fatty alcohol tend to leave visible white deposits on application to human skin. These deposits can also transfer onto clothing when it comes into contact with the skin and the wearer can, for example, find white marks on the armhole of a sleeveless garment. Fatty alcohols are often regarded as coming within the general category of waxy materials, but we have observed that they are a more significant source of white deposits than other waxy materials.
There have been some disclosures of antiperspirant stick compositions where structuring to a shape-sustaining stick has been accomplished without using a fatty alcohol. Amongst these disclosures there has sometimes been recognition that white deposits are avoided.
The thickening of organic liquids with polyamides in order to make antiperspirant compositions has been disclosed in U.S. Pat. No. 5500209. 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.
WO 97/36572 WO 97/36573 and WO 99/06473 all disclose the structuring of antiperspirant sticks with siloxane polymers which incorporate amide and/or other hydrogen bonding substituent groups.
We have found that when emulsion sticks are structured solely with such polymer according to these prior documents, the result is unsatisfactory. Over 10% polymer was required to obtain firm sticks, but these were then found to have a rubbery, tacky feel. Moreover pieces could be broken off easily.
WO 97/13496 employs polyethyleneformamides to form an antiperspirant gel in an aqueous or water-miscible medium. It provides no teaching of relevance to structuring a water-immiscible liquid carrier.
U.S. Pat. No. 4,265,878, U.S. Pat. No. 4,725,431, U.S. Pat. No. 4,732,754, U.S. Pat. No. 4,719,103 and U.S. Pat. No. 4,704,271 disclose antiperspirant stick compositions in which a solution of antiperspirant active in aqueous solution is dispersed in a hydrophobic continuous phase of hydrocarbon or silicone oil. This hydrophobic continuous phase is structured to provide a rigid stick by the incorporation of a substantial amount of waxy material, such as stearyl alcohol or spermaceti wax.
U.S. Pat. No. 4,822,602 exemplifies a composition structured with sodium stearate which restricts the choice of antiperspirant active to an unusual active which does not precipitate as an insoluble salt on contact with stearate, but is of poor efficacy. The sodium stearate causes phase transfer of a water-miscible constituent. A stick prepared in accordance with this example was found to have a tacky, draggy feel on handling.
In some cases structuring has been achieved 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; upon reheating, melting of the gel takes place as an endothermic event within a temperature range. Such gels can be disrupted by shearing and do not recover their structure for a long time, if at all unless remelted, although a small partial recovery may be observed.
U.S. Pat. No. 5,429,816 discloses an antiperspirant stick in which a solid antiperspirant active is dispersed in a carrier mixture of silicone and other oil which is gelled with 12-hydroxy stearic acid used jointly with a secondary gellant which is an n-acyl-amino acid amide. The deposit on skin is said to be a low visible residue, rather than an opaque white deposit. A number of other documents provide similar disclosures of suspension sticks structured with these materials.
U.S. Pat. No. 5,480,637 discloses the preparation of an antiperspirant stick in which a suspension of solid, encapsulated aluminium chlorohydrate dispersed in silicone oil is gelled with 12-hydroxy stearic acid used jointly with a small amount of an alkyl methyl siloxane polymer. U.S. Pat. No. 5,492,691, U.S. Pat. No. 5,455,026 and EP-A-616842 are somewhat similar but do not require the siloxane polymer. Although U.S. Pat. No. 5,480,637 teaches the use of siloxane polymer to promote the gelling action of 12-hydroxystearic acid, we have found that it has very little effect.
U.S. Pat. No. 5,840,286 is concerned with anhydrous suspension sticks containing a gelling agent and requires that the composition is substantially free of organic polymeric gellant.
U.S. Pat. No. 4,719,102, U.S. Pat. No. 4,725,430, U.S. Pat. No. 5,200,174 and U.S. Pat. No. 5,346,694 all disclose sticks formed by mixing two solutions both of which contain a substantial amount of a polar solvent. One contains dibenzylidene sorbitol or a similar compound as a structurant while the other contains the antiperspirant active dissolved in an alcohol solution with little water present. The alcoholic solution generally contains ethanol or a mixture of ethanol and propylene glycol. The two solutions beco

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