Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2000-08-17
2003-07-15
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C424S400000, C514S938000
Reexamination Certificate
active
06592883
ABSTRACT:
The present invention relates to emulsifier-free finely disperse systems of the water-in-oil type, preferably as cosmetic or dermatological preparations.
By far the most important type of product in the field of skin care compositions are emulsions. Emulsions are disperse two- or multi-phase systems, cosmetic emulsions consisting of at least one fatty phase (fats and mineral oils, fatty acid esters etc.) and at least one water phase (water, glycerol, glycols etc.), which are finely distributed in one another with the help of emulsifiers. The lipophilic phase of a body care emulsion usually comprises a mixture of oils, fats and waxes, the composition of which is said to significantly influence the product-determining properties such as skin care and feel on the skin.
If the two liquids are water and oil and if oil droplets are finely distributed in water, then this is an oil-in-water emulsion (O/W emulsion, e.g. milk). The basic character of an O/W emulsion is determined by the water. In the case of a water-in-oil emulsion (W/O emulsion, e.g. butter), the principle is reversed, the basic character here being determined by the oil.
In order to achieve permanent dispersion of one liquid in another, emulsions in the traditional sense require the addition of a surface-active substance (emulsifier). Emulsifiers have an amphiphilic molecular structure, consisting of a polar (hydrophilic) and a nonpolar (lipophilic) molecular moiety, which are spatially separate from one another. They lower the surface tension between the phases by positioning themselves at the interface between two liquids (they form interfacial films), as a result of which irreversible coalescence of the droplets is prevented. Emulsions are frequently stabilized using emulsifier mixtures.
Traditional emulsifiers can, depending on their hydrophilic molecular moiety, be divided into ionic (anionic, cationic and amphoteric) and nonionic:
The most well-known example of an anionic emulsifier is soap, which is usually the term used for the water-soluble sodium or potassium salts of saturated and unsaturated higher fatty acids.
Important examples of cationic emulsifiers are the quaternary ammonium compounds.
The hydrophilic molecular moiety of nonionic emulsifiers frequently consists of glycerol, polyglycerol, sorbitans, carbohydrates and polyoxyethylene glycols and, in most cases, is linked to the lipophilic molecular moiety via ester and ether bonds. The lipophilic molecular moiety usually consists of fatty alcohols, fatty acids or isofatty acids.
By varying the structure and the size of the polar and nonpolar molecular moiety, the lipophilicity and hydrophilicity of emulsifiers can be varied within wide limits.
A decisive factor for the stability of an emulsion is the correct choice of emulsifiers. In this connection, the characteristics of all the substances present in the system are to be taken into consideration. In the case of, for example, skin care emulsions, polar oil components and, for example, UV filters lead to instability. As well as the emulsifiers, therefore, other stabilizers are also used which, for example, increase the viscosity of the emulsion and/or act as protective colloid.
Cosmetic preparations are essentially used for skin care. The main aim of skin care in the cosmetics sense is to strengthen or rebuild the skin's natural function as the barrier against environmental influences (e.g. dirt, chemicals, microorganisms) and against the loss of endogenous substances (e.g. water, natural fats, electrolytes). If this function becomes impaired, increased resorption of toxic or allergenic substances or attack by microorganisms may result, leading to toxic or allergic skin reactions.
Another aim of skin care is to compensate for the loss by the skin of lipids and water caused by daily washing. This is particularly important where the natural regeneration ability is inadequate. Furthermore, skincare products should protect against environmental influences, in particular against sun and wind, and delay skin ageing.
The harmful effect of the ultraviolet part of solar radiation on the skin is generally known. Depending on their respective wavelength, the rays have different effects on the skin organ: UV-C radiation having a wavelength of less than 290 nm is absorbed by the ozone layer in the earth's atmosphere and is of no physiological importance. By contrast, rays in the range between 290 nm and 320 nm, the UV-B region, cause erythema, simple sunburn or even burns of varying severity. UV-A radiation (320 to 400 nm) is much more harmful than UV-B radiation with regard to the triggering of photodynamic, specifically phototoxic, reactions and chronic changes in the skin. For example, UV-A radiation on its own under very normal everyday conditions is sufficient to damage collagen and elastin fibres within a short period. The harmful effect of UV-B radiation can also be further intensified by UV-A radiation.
In addition, even very low doses of radiation can trigger photochemical reactions. These include, in particular, the formation of free radicals, which in turn can trigger uncontrolled secondary reactions as a result of their high reactivity. In order to prevent such reactions, as well as UV filter substances, it is also possible to additionally add antioxidants and/or free-radical scavengers to cosmetic or dermatological formulations.
Emulsions also play the decisive role in the field of sunscreen formulations. In this connection, preference is given to flowable emulsions, since they can be applied more easily than viscous creams. Most sunscreens are applied in the vicinity of water or during sporting activity (perspiration), for which reason the water resistance of such formulations is to be attributed particular importance. A water-resistant sunscreen protects the user not only after bathing, but also protects him against sunburn during bathing.
In order to achieve high sunscreen factors coupled with very good water resistance, W/O formulations are advantageous. However, W/O emulsions of the prior art frequently have unsatisfactory cosmetic properties. During application, appropriate preparations can leave behind a greasy, shiny and sometimes sticky impression on the skin and—particularly on hairy skin—are difficult to spread. In individual cases, therefore, such preparations may not even be marketable since they are unacceptable to or viewed negatively by the consumer.
An object of the present invention was therefore to remedy the disadvantages of the prior art and to find preparations of the water-in-oil type which, for example, permit the formulation of high sunscreen factors coupled with very good water resistance, but which do not leave behind a greasy or sticky impression on the skin.
In addition, cosmetic preparations are also used as deodorants. Such formulations are used to control body odour which forms when fresh perspiration, which is in itself odourless, is decomposed by microorganisms.
Medicinal topical compositions usually comprise one or more medicaments in an effective concentration. For the sake of simplicity, in order to distinguish clearly between cosmetic and medicinal use and corresponding products, reference is made to the legal provisions of the Federal Republic of Germany (e.g. Cosmetics Directive, Food and Drugs Act).
The use of customary emulsifiers in cosmetic or dermatological preparations is in itself acceptable. Nevertheless, emulsifiers, like ultimately any chemical substance, may in individual instances cause allergic reactions or reactions based on oversensitivity of the user.
For example, it is known that certain light dermatoses are triggered by certain emulsifiers, but also by various fats and simultaneous exposure to sunlight. Such light dermatoses are also called “Mallorca acne”. There has thus been no lack of attempts to reduce the amount of customary emulsifiers to a minimum, and in an ideal case even completely.
A reduction in the required amount of emulsifier can, for example, be achieved by taking advantage of the fact that very finely divided solid pa
Gers-Barlag Heinrich
Grotelüschen Birgit
Müller Anja
Beiersdorf AG
Dodson Shelley A.
Norris & McLaughlin & Marcus
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