Drug – bio-affecting and body treating compositions – Anti-perspirants or perspiration deodorants
Reexamination Certificate
1999-10-12
2001-07-17
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Anti-perspirants or perspiration deodorants
C424S066000, C424S068000, C424S400000, C424S401000, C424S078020, C424S078080
Reexamination Certificate
active
06261543
ABSTRACT:
The present invention relates to compositions containing an antiperspirant, particularly to emulsion compositions and to a process for their production.
1. Technical Field
A variety of applicators have been described and/or commercialised for topically applying antiperspirant compositions to human skin. Amongst applicators which have found favour over the years, there can be listed roll-ons, pump or squeeze sprays, and pressurised aerosols which normally or often employ flowable liquids and creams or sticks which are sometimes produced from flowable liquids.
Antiperspirant formulations have been proposed or commercialised in a number of different physical forms, including powders, suspension or emulsions structured solids or creams and solution or emulsion liquids. The present invention is particularly directed to emulsions in liquid form or optionally after structuring and especially to oil in water emulsions.
2. Background and Prior Art
Emulsions can be made by mixing an aqueous phase with an oil phase in the presence of an emulsifier or blend of emulsifiers, optionally at an elevated temperature selected to dissolve desired ingredients in one or other of the phases. An established method to produce fine droplet dispersion emulsions is the so-called phase inversion temperature or PIT process, the emulsifier, aqueous phase and the oil phase are mixed at, or the mixture heated to, a temperature at which phase inversion occurs, and thereafter the emulsion is permitted to cool or is cooled to ambient.
Emulsions represent a potentially convenient form for antiperspirant compositions in that it is theoretically possible to obtain fine dispersions of the one phase in the other. This can result, if sufficiently fine, in the formation of transparent or nearly transparent formulations which a number of consumers perceive to be beneficial.
However, stability problems can arise for emulsions. Emulsions (not microemulsions) are thermodynamically unstable and accordingly rely for their apparent stability on de-emulsification being kinetically hindered. De-emulsification can be exacerbated by storage of the formulations at high ambient temperatures, such as can arise in warehouses during summer months, especially in tropical or central continental or Mediterranean climates, or by a temperature cycle in which the formulations are subjected to cyclical heating and cooling. Additionally, the presence of elevated concentrations of salts in the aqueous phase encourages de-emulsification. This is of direct pertinence to antiperspirant emulsions, and especially aluminium or aluminium/zirconium emulsions which incorporate a substantial concentration of antiperspirant active salts in the aqueous phase. Accordingly, teaching concerning the stability of emulsions which do not contain a significant concentration of antiperspirant salts cannot be transferred unquestioningly to antiperspirant-containing emulsions.
A number of publications have described the preparation of water in oil emulsions, or anhydrous emulsions, such as GB-A-2113706 to Colgate-Palmolive Co, GB-A-2009617 to Petersen/Puritan, Inc and GB-A-20968891 to Colgate-Palmolive Co. These, however, do not provide suitable teaching for stabilising oil in water emulsions.
In DE-A-4337041 to Henkel, there is described a process for producing oil in water emulsions employing a PIT technique, but the disclosure is silent about the incorporation of antiperspirant actives. In practice, the addition of antiperspirant actives in attractive concentrations, e.g. at a concentration which offers substantial sweat reduction to the Henkel compositions impairs their stability.
In WO 96/23483 to Bristol Meyers Squibb, there is described a process producing emulsions at below the phase inversion temperature of the emulsion and employing tightly defined combinations of ingredients. They are in the form of microemulsions.
In U.S. Pat. No.4,499,069 to Gillette, there is described the preparation of a stable emulsion employing a surfactant mixture containing polyethylene glycol (21) stearyl ether, but this does not provide a transferable teaching on how to achieve stability, because the document discloses that closely related surfactants such as polyethylene glycol (20) stearyl ether and other polyglycol ether mixtures did not produce stable emulsions. Moreover, it employs a hydrophobic polymer.
Aqueous emulsions can also suffer from an impaired sensory perception by users, and particularly emulsions containing particularly efficacious antiperspirant salts.
Accordingly, there is a continuing need for a method that is capable of producing stable emulsions containing an antiperspirant active salt. Additionally or alternatively, there remains an outstanding desire for aqueous emulsions which are both sensorially pleasing and effective in reduction of perspirancy. Alternatively or additionally, there remains a need for a method or an alternative method to produce an emulsion comprising a fine dispersion and containing an antiperspirant active salt, and particularly a process to produce an emulsion which is stable. Furthermore, there remains a need for a process which can produce not only a stable antiperspirant emulsion offering acceptable sweat reduction, but one that exhibits sensorially pleasing characteristics.
OBJECTS OF THE INVENTION
It is an object of at least one aspect of the present invention to provide a process that is capable producing an antiperspirant emulsion having a small mean droplet size.
It is an object of at least some embodiments of the present invention to provide an antiperspirant emulsion which is resistant to phase separation, and particularly in preferred embodiments offering resistance to phase separation during storage at above standard temperature.
It is an additional or alternative object of certain or other embodiments of the present invention to provide aqueous emulsions containing a high concentration of a salt or salts which is resistant to phase separation and particularly in preferred embodiments offering resistance to phase separation during storage at above standard temperature.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a process for producing an antiperspirant—containing emulsion comprising the steps of:
i) dispersing a hydratable polymer in an aqueous emulsion comprising an aqueous phase, an oil phase and an emulsifier at a concentration and at a temperature selected such that the polymer is hydrated and the viscosity of the emulsion is substantially higher than in the absence of the polymer,
ii) subjecting the emulsion containing the dispersion of hydratable polymer to high shear,
iii) agitating the emulsion until its temperature has attained a temperature below 40° C. and
iv) introducing an antiperspirant salt into the emulsion with agitation to form an antiperspirant emulsion.
A hydratable polymer is one which exhibits swelling when brought into contact with an aqueous medium. There is a tendency for the polymer chains to uncoil during hydration and thereby expand. This is in contrast with hydrophobic polymers which do not exhibit swelling.
By subjecting a viscous emulsion containing a dispersed hydratable polymer to high shear, it is possible to obtain an emulsion in which its dispersed phase has a reduced mean droplet size. The emulsions obtained in the present invention are not micro-emulsions. Without being restricted to any theory as to the mode by which the invention result is achieved, it is believed that the hydratable polymer tends to hydrate at the selected processing temperature subsisting in step i) and produces a thickened aqueous phase. When the hydratable polymer is dispersed through the emulsion and subjected to high shear, the elevated viscosity of the emulsion induces rupturing of the droplets. By contrast, without dispersion of the polymer and in a thin formulation, efficient droplet rupturing has not been observed.
The temperature and concentration of the hydratable polymer to provide a significant increase in the viscosity of the emulsion is related to
Fletcher Neil Robert
Kanda Miyuki
Ketelson Howard Allen
Turner Graham Andrew
Boxer Matthew
Dodson Shelley A.
Unilever Home & Personal Care USA , division of Conopco, Inc.
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