Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – For cleaning a specific substrate or removing a specific...
Reexamination Certificate
1999-03-31
2001-12-11
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
For cleaning a specific substrate or removing a specific...
C510S130000, C510S135000, C510S151000, C510S159000, C510S438000, C510S470000, C510S475000, C510S511000, C510S537000
Reexamination Certificate
active
06329331
ABSTRACT:
This invention relates to foaming detergent compositions which may be for use in personal washing, or in other applications.
A number of detergent products for personal washing are formulated as viscous liquids, creams or gels. Examples of such products are hair shampoos, shower gels and facial washes. Such products generally contain foaming surfactant which usually comprises at least 3 wt % of anionic surfactant, possibly accompanied by amphoteric, zwitterionic or nonionic surfactant. It is conventional for such products to contain one or more ingredients whose function is to increase the viscosity of the composition. Some other liquid detergent compositions are also required to contain foaming surfactant and to have a viscosity greater than that of water.
One possibility for enhancing the viscosity of a fluid composition is to incorporate a sufficient quantity of electrolyte together with a sufficient quantity of selected surfactant, so that the surfactant is present in a viscous phase, and thus increases the viscosity of the resulting composition.
It is also known to incorporate polymeric materials to enhance viscosity. One category of synthetic polymers used for this purpose are crosslinked polyacrylates, for instance those sold under the trade mark Carbopol. Natural polymers have also been used for this purpose, and in particular xanthan gum and its derivatives has been used. Personal washing products, especially shampoos, containing xanthan gum are described in for example U.S. Pat. No.5,151,210 and EP-A-500423.
Detergent products containing other polymers have been described, for example in U.S. Pat. No. 5,286,405 and GB-A-2188060.
EP-A-271131 discloses a number of products intended for application to skin which are thickened with carrageenan so as to form gels. Many of these do not include surfactant. One product disclosed in this document is a cleansing composition, containing a low foaming nonionic surfactant.
A number of polymers of biological origin, when in aqueous solution, have the ability to form so-called reversible gels 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 occurring 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 display a melting temperature or temperature range, 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 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.
Although xanthan gum can be incorporated as a thickener in aqueous compositions containing surfactant, the resulting products tend to have a stringy texture and a slimy feel. We have found that the gels formed on cooling of a number of other polymers of biological origin are incompatible with foaming surfactants. The surfactant makes the gel unstable and phase separation occurs on cooling or on subsequent storage.
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”. This document exemplifies a number of products, one of which is named a “cleanser gel” and includes a low foaming nonionic surfactant as an emulsifier.
We have now found that it is possible to form detergent compositions which are shear gels and which include foaming surfactant.
According to the present invention, there is provided an aqueous detergent composition, which has a thickened fluid form, containing foaming surfactant and a polymer or polymer mixture which is capable of forming a reversible gel in water, which polymer is present in the composition as a multiplicity of separate gel particles.
In the present specification, the expression “thickened fluid” is used to denote a composition with viscosity greater than that of water.
In order that the gel particles remain stable in the presence of surfactant, it will generally be desirable that the polymer or polymer mixture does not require polyvalent cations in order to form the precursor aggregates that are subsequently capable of intermolecular association leading to formation of a gel network. Consequently it is desirable that the polymer or mixture is capable of forming a reversible gel when dissolved at a sufficient concentration in hot distilled or demineralised water and allowed to cool to an ambient temperature of 20° C.
The composition may consist solely of a continuous aqueous phase and the gel particles therein. However, compositions thickened with gel particles, in accordance with this invention have been found to be very effective at suspending other materials and so a composition of this invention may incorporate suspended particles of a water-immiscible liquid (eg a water-immiscible oil) or of a solid other than polymer gel. The amount of such particles may lie in a range from 0.1 to 40% by weight, preferably 0.1 to 25% by weight, more preferably 0.5 to 20% by weight of the composition.
Compositions embodying this invention may be made with viscosities in a wide range. At one extreme, the compositions may be freely mobile, self-levelling and pourable, although thicker than water. On the other hand, they may be made as viscous liquids which can be squeezed from a collapsible container, and yet which are too viscous to pour, except very slowly.
They are shear-thinning, which can be a useful property, notably in personal washing compositions, because the user can perceive the product as thick and viscous, and yet find it easy to apply. An advantage of viscous shear gels, as compared to compositions thickened in some other way, is that they are better at retaining the shape which has been squeezed out.
If the compositions are heated to a temperature above the melting and transition temperatures, the individual gel particles will melt and will not reform as separate particles on cooling, but this will not be a problem in ordinary use, because reversible gels generally have melting temperatures well above
Aronson Michael Paul
Brown Charles Rupert
Chatfield Robert James
Fairley Peter
Norton Ian Timothy
Gupta Yogendra N.
Koatz Ronald A.
Mruk Brian P.
Unilever Home & Personal Care USA , division of Conopco, Inc.
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