Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Matrices
Reexamination Certificate
2001-10-24
2004-01-06
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Matrices
C424S484000, C424S489000, C424S070100, C424S070400, C424S070110, C424S070120, C424S070130, C424S070140
Reexamination Certificate
active
06673371
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compositions having a thickened fluid form, to a process for their production and to their use. In particular, the invention relates to compositions comprising a phase formed from a particular type of gel which may be used, for example, as hair treatment compositions and personal wash compositions.
BACKGROUND AND PRIOR ART
Suspending agents are commonly employed in a variety of different types of compositions (eg, in hair treatment compositions) in order to improve stability against separation of the components, especially settling of suspended materials.
Examples of suspending agents commonly used in hair treatment compositions include crystalline suspending agents (such as ethylene glycol distearate) and inorganic structurants (such as swelling clays). Although these materials are effective for suspending particulate matter, they can adversely affect lathering performance and impart an undesirable cloudy appearance to the composition. Furthermore, during use of the composition they tend to get co-deposited along with the ingredients it is desired to deposit, which can lead to dulling of the hair through excessive build up and reduced performance.
The prior art also proposes the use for suspending purposes of hydrophilic polymers which disperse in aqueous media. Natural polymers have been used for this purpose, and in particular xanthan gum has been used. Personal washing products, especially shampoos, containing xanthan gum are described for example in U.S. Pat. No. 5,286,405 and GB-A-2188060. A problem is that the resulting products often have an unacceptable “stringy” texture and a slimy feel.
One category of synthetic polymers used for suspending purposes are carboxyvinyl polymers. The carboxyvinyl polymers are colloidally water soluble polymers of acrylic acid cross-linked with polyallylsucrose or polyallylpentaerythritol, obtainable under the CARBOPOL trademark from B F Goodrich. U.S. Pat. No. 5,635,171 describes a transparent or translucid gel based on such polymers, in which the gel is rigidified by the incorporation of a very small quantity of an aqueous solution of galactomannan (carob, guar or tara gum). This rigidification enables the stabilization of suspended phases.
A problem is, however, that carboxyvinyl polymers of the above described type can be difficult to formulate because of, inter alia, their sensitivity to pH and ionic strength and their incompatibility with ethoxylated surfactants.
A number of polymers of biological origin, when in aqueous solution, have the ability to form so-called reversible gels, for example, those which melt when heated but revert to a gel when cooled down subsequently. One well known example of a polysaccharide which forms reversible gels is agar. An aqueous solution containing a small percentage of agar is a mobile liquid when hot, but when left to cool it forms a gel with sufficient rigidity to maintain its own shape. Other naturally derived polymers which can form reversible gels are carrageenan, furcelleran, gellan and pectin.
The formation of gels by natural polysaccharides arises from interaction between the polymer molecules. Reversible gels generally melt over a range of temperatures or display a melting temperature, referred to as the gel point. This is the temperature at which, on slow heating, the gel is observed to melt as this interaction largely disappears. Thus, above the gel point, the hot solution of polymer is mobile. When it cools below its gel point, the interaction of polymer molecules enables them to form a continuous and branched network which extends throughout the sample. In contrast with the formation of a continuous, branched network, some other materials which thicken water do so through merely local, transient entanglement of molecules. A discussion of polysaccharide gels, including their range of mechanical properties, is found in “Gels and Gelling” by Allan H Clark which is Chapter 5 in Physical Chemistry of Foods, Schwartzberg and Hartel, editors; published by Marcel Dekker 1992. In some instances, there is hysteresis and the melting and setting temperatures are not identical.
The melting temperature of a gel can suitably be measured by placing a steel ball, having a diameter of approximately 1 mm, on the surface of a sample which is fully set, then raising the temperature slowly, e.g., in a programmable water bath. The gel melting point is the temperature at which the ball begins to sink through the sample. Apparatus to facilitate such determinations is available, for example as a Physica AMV200 rolling ball viscometer from Anton Paar KG.
A reversible gel also displays a transition temperature at which, upon slow temperature increase, all ordering, be it of microscopical or macroscopical extent, has disappeared completely. This transition temperature (from order to disorder) can be measured by means of differential scanning calorimetry (DSC). The transition temperature of a reversible gel, as measured by DSC, usually approximately coincides with gel melting, observable visually.
EP-A-355908 teaches that polysaccharides which are capable of forming a reversible gel can be used to form viscous, yet mobile, fluid compositions by subjecting the composition to shear while gel formation takes place. The resulting compositions can be termed “shear gels”.
Another way of forming a shear gel is to use a protein gel rather than a polysaccharide gel. An example of this is using a cold set whey gel as disclosed in U.S. Pat. No. 5,217,741, which is a gel created from pre-formed whey aggregates when the pH is changed or salt is added. This cold set whey gel can be produced as a shear gel of similar properties to that of the polysaccharide shear gels.
EP0250623 discloses the formation of whey particles by heating the whey solution under high shear to produce small heat set particles, that can be used as a fat replacement. The particles are not described as entrapping any material, nor are they described as a fluid gel with apparent yield stress properties.
We have now found that compositions comprising a continuous phase formed from such shear gels not only display excellent resistance to separation of components and settling of suspended materials but also can be used to entrap beneficial materials within the gel particles. “Entrap” is a used to describe situations where the beneficial materials are residing within a single gel particle and/or where the beneficial materials are associated with the gel matrix structure. The shear gels of these compositions are tolerant to the presence of many surfactants (eg, in personal wash or hair treatment compositions), and may under some circumstances enhance the delivery of the beneficial materials from the compositions.
WO98/08601 describes aqueous compositions such as liquid personal cleansers containing large hydrogel particles formed by two different water soluble polymers. The hydrogel particles trap water insoluble benefit agents in a network formed by these two polymers. The system is not a shear gel since it is prepared by first forming elongated polymer gel noodles which after gel formation are subsequently cut/broken into the desired gel particle size. The second polymer (which is typically an acrylic polymer such as CARBOPOL™ referred to above) is required to modify gel strength in order to help stabilise benefit agent in the polymer hydrogel system. WO95/12988 refers to suspensions or dispersions of gelled and hydrated biopolymer particles for use in food or personal care products to impart a fatty-like character to the product. This system is not a shear gel since particulation of dry material at a temperature equal to or above T(gel) is followed by hydration of the particles at a temperature lower than T(gel), the term “T(gel)” denoting the temperature at which, upon cooling, an aqueous solution of the biopolymer concerned, sets to a gel.
WO99/51193 discloses hair treatment compositions comprising a first (shear gel) phase and a second (suspended) phase. The second (suspended) phase is suspended in the shear
Brown Charles Rupert
Carew Peter Simon
Eklund John Charles
Evans Jeannette Marcia
Fairley Peter
Aronson Michael P.
Page Thurman K.
Sheikh Humera N.
Unilever Home & Personal Care USA , division of Conopco, Inc.
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