Emulsification systems and emulsions

Details Emulsification systems and emulsions Emulsification systems and emulsions

2001-05-29

2004-12-14

Metzmaier, Daniel S. (Department: 1712)

Drug, bio-affecting and body treating compositions

Designated organic nonactive ingredient containing other...

Carbohydrate or lignin, or derivative

C514S939000, C514S941000, C514S772000, C514S782000, C516S073000, C516S074000, C516S107000, C424S401000, C424S078300, C424S059000

Reexamination Certificate

active

06831107

ABSTRACT:

This invention relates to emulsification systems and emulsions and in particular to emulsification systems including emulsifiers and high molecular weight polysaccharide combinations and to emulsions made using such systems as emulsifiers and emulsion stabilisers and particularly to such emulsification systems and emulsions in the form of personal care products such as cosmetic skin creams and milks.
Personal care emulsion products such as creams and milks desirably have a number of properties in combination: stability in manufacture, formulation, storage and use; a viscosity appropriate to the end use; and preferably a desirable body and good skin feel. Body and skin feel are usually assessed subjectively, and although good body and/or skin feel are commonly associated with a non-Newtonian, shear thinning viscosity profile, a shear thinning profile does not guarantee a good body or skin feel. Typical conventional personal care emulsion products use emulsifiers (including emulsion stabilisers) in amounts of about 3 to about 5% by weight of the emulsion. Recently, thickeners have been proposed as emulsion stabilisers and the mechanism of stabilisation when these are used appears to be that the thickener increases the low shear viscosity of the emulsion sufficiently to provide a barrier to emulsion droplet coalescence, probably by limiting the movement of the droplets.
The present invention is based on our discovery that certain combinations of high molecular weight polysaccharides can provide good emulsion stabilisation at levels that do not give high, or even significantly increased, low shear viscosity and that using such combinations, the amount of emulsifier, usually a relatively low molecular weight, often non-ionic, surfactant can be much less than is used conventionally in emulsions, particularly emulsions for personal care products such as cosmetic skin creams and milks.
The present invention accordingly provides a personal care or cosmetic oil in water emulsion which includes as an emulsifier stabiliser system, an emulsifier for the oil and a polysaccharide combination of a Xanthan polysaccharide and a polyglucomannan polysaccharide.
The invention also includes the use of a polysaccharide combination of a Xanthan polysaccharide and a polyglucomannan polysaccharide as an emulsifier stabiliser system in personal care or cosmetic oil in water emulsions. The invention further includes a dry blend emulsifier stabiliser formulation which includes an oil emulsifier and an oil in water emulsion stabiliser which is a polysaccharide combination of a Xanthan polysaccharide and a polyglucomannan polysaccharide.
The polysaccharide combination of a Xanthan polysaccharide and a polyglucomannan polysaccharide may for convenience briefly referred to as a polysaccharide stabiliser.
The combined amount of emulsifier and stabiliser in emulsions of the invention can be much lower than the typical 3 to 5% used in conventional personal care emulsion systems. In particular, in many emulsions of this invention, the amount of emulsifier can be less than about 1.5%, particularly up to about 1%, and the amount of polysaccharide stabiliser can be less than about 0.5%, and sometimes as little as about 0.02%, desirably with the combined amount being less than about 1.5%, particularly up to about 1%. The minimum amount of emulsifier is typically about 0.02% more usually 0.025% by weight of the emulsion (see also below). Accordingly, the invention includes a personal care or cosmetic oil in water emulsion which includes as an emulsifier stabiliser system an emulsifier for the oil in an amount not more than about 1% by weight of the emulsion and a polysaccharide stabiliser in an amount of from about 0.02 to about 0.5% by weight of the emulsion.
Personal care emulsions can be divided by viscosity into milks and lotions, which typically have a low shear viscosity of up to about 10000 mPa.s, and creams which typically have a low shear viscosity of more than about 20000 mPa.s. Typically, milks and lotions have a low shear viscosity of from about 100 to about 10000 mPa.s, more usually from about 500 to about 5000 mPa.s, and typically creams have a low shear viscosity of at least about 30000 mPa.s, particularly from about 30000 to about 80000 mPa.s, although even higher viscosities e.g. up to about 10
6
mPa.s, may also be used. In this context low shear viscosity refers to viscosity measured at shear rates of about 0.1 to 10 s
−1
as is typically used in Brookfield viscometers. Because for good skin feel, personal care and cosmetic emulsions are usually shear thinning, the measured low shear viscosity is only a general guide to whether the product is a milk (or lotion) or cream.
The present invention includes both milk (and lotion) and cream emulsions and specifically the invention includes a personal care or cosmetic oil in water emulsion milk or lotion having a low shear viscosity of up to about 10000 mPa.s, which includes as an emulsifier stabiliser system an emulsifier for the oil and a polysaccharide stabiliser. The invention further includes a personal care or cosmetic oil in water cream emulsion having a low shear viscosity of more than about 20000 mPa.s, which includes as an emulsifier stabiliser system an emulsifier for the oil and a polysaccharide stabiliser, the emulsion further including thickener components.
Xanthan is a polysaccharide including mannose, glucose and glucuronic acid monomer units and typically the main polymer backbone is polyglucose with 3-unit acetylated side chains including glucose, glucuronic acid, typically present as a mixed potassium, sodium and calcium salt, and mannose residues. Xanthan polymers have a molecular weight typically in the range 1.10
6
to 5.10
6
and usually about 2.10
6
and are typically obtained from bacterial fermentations, particularly of
Xanthomannas campestris
and related microorganisms. The Xanthan products sold under the Keltrol tradename, particularly the ‘F’ and ‘T’ grades, by Kelco are particularly suitable in this invention.
The polyglucomannan typically has a random glucose/mannose backbone, typically at a molar ratio of glucose to mannose in the range about 1:1.5 to about 1:3, usually about 1:2 with hydroxyl groups on pendent methylol groups randomly acetylated, typically so that there is about one acetyl group per 6 to 20 sugar monomer residues. The molecular weight of useful polyglucomannans can vary within a typical range of from about 2.10
5
to about 2.10
6
. Suitable materials include vegetable polyglucomannans such as those derived from
Konjak. Konjak
polyglucomannan, sometimes referred to simply as
Konjak
or
Konjak
gum, is particularly effective in this invention and its use as a/the polyglucomannan forms a specific aspect of the invention.
Konjak,
Amorphophallus
konjak
, also known as Konjac and Devil's Tongue, is a tuber plant grown in Asia as a food plant. The carbohydrate components of the tuber include
Konjak
polyglucomannan Naturally occurring
Konjak
polyglucomannan typically has a molecular weight of about 1.10
6
to about 2.10
6
, but processing e.g. refining and milling, can reduce the molecular weight.
The emulsions of the invention have aqueous continuous phases and in making the emulsions the polysaccharides will usually be dispersed in water. The particle size of the polysaccharides, especially the polyglucomannan, can be important in achieving good dispersion in water, especially relatively cool, particularly cold (ambient temperature) water.
Konjak
polyglucomannan is readily dispersible in hot water at concentrations of 0.001 to 0.5% by weight. However, as typically derived from the tuber,
Konjak
polyglucomannan has a relatively large particle size typically having an average particle size of from about 100 to about 2000 &mgr;m. Material with this particle size tends to have relatively poor cold water dispersibility. Milling to lower particle size e.g. from about 50 to about 200 &mgr;m, can make the product much more readily cold water dispersible. Cold water dispersibility of Xanthan po

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