Method of preparing particularly skin-compatible cosmetic or...

Details Method of preparing particularly skin-compatible cosmetic or... Method of preparing particularly skin-compatible cosmetic or...

2000-12-15

2002-10-22

Krass, Frederick (Department: 1619)

Drug, bio-affecting and body treating compositions

Live hair or scalp treating compositions

Two or more designated surfactant containing

C424S401000, C424S070210, C424S070240, C514S975000, C514S846000, C514S887000, C514S773000, C514S801000, C514S828000, C514S847000, C514S945000, C510S155000, C510S108000, C510S130000, C510S135000, C510S152000

Reexamination Certificate

active

06468514

ABSTRACT:

The present invention relates to a method of preparing particularly skin-compatible cosmetic or dermatological cleansing preparations.
Preparations of this type are, for example, foam baths and shower preparations, solid and liquid soaps or co-called “syndets” (synthetic detergents), shampoos, handwash pastes, personal hygiene washing compositions, special cleansers for small children and the like.
In a particular embodiment, the present invention relates to cleansing preparations for use as shower preparations, bath preparations, body cleansing and face cleansing.
Preparations of this type are also known per se. They are essentially surface-active substances or substance mixtures supplied to the consumer in a variety of preparations. Preparations of such type are generally distinguished by a greater or lesser water content, but can also, for example, be in the form of concentrate.
Even simple bathing in water without the addition of surfactants will initially cause the horny layer of the skin to swell, the degree of this swelling depending, for example, on the bathing time and temperature. As well as water-soluble substances, e.g. water-soluble constituents of dirt, substances endogenous to the skin which are responsible for the water-binding capacity of the horny layer are also washed off or out. In addition, as a result of surface-active substances endogenous to the skin, fats in the skin are also dissolved and washed out to a certain degree. After the initial swelling, this causes a subsequent significant drying-out of the skin, which may be further intensified by washing-active additives.
In healthy skin, these processes are generally of no consequence since the protective mechanisms of the skin can readily compensate for such slight disturbances to the upper layers of the skin. However, even in the case of nonpathological deviations from the norm, e.g. as a result of wear damage or irritation caused by the environment, photodamage, aging skin etc., the protective mechanism of the surface of the skin is impaired. In some circumstances it is then no longer able to fulfill its role by itself and must be regenerated by external measures.
The object of the present invention was therefore to remedy these shortcomings of the prior art. It was further an object of the invention to provide bath or shower preparations which on the one hand have a high care action, without, on the other hand, the cleansing action becoming inferior.
Surface-active substances, the best known being the alkali metal salts of higher fatty acids, i.e. the classical “soaps”—are amphiphilic substances which are able to emulsify or solubilize organic nonpolar substances in water.
These substances not only flush dirt from the skin and hair, they irritate skin and mucous membranes to a greater or lesser extent depending on the choice of surfactant or surfactant mixture.
One of the most commonly used surfactants for cosmetic compositions throughout the world is sodium lauryl ether sulfate. Although an excellent washing-active agent with good foaming ability, in higher concentrations it has an irritative effect on skin and mucous membranes.
As more recent investigations show, the irritancy potential of sodium lauryl ether sulfate is at least partially promoted by the fact that this substance binds to the surface of the skin where it forms a certain reservoir. Studies suggest that lauryl ether sulfate from this reservoir penetrates into the deeper layers of the skin, where it can then cause uncontrolled secondary reactions, which harbor an increased risk of irritation.
Commercially available sodium lauryl ether sulfate (=sodium polyoxyethylene lauryl sulfate, according to INCI nomenclature: “Sodium laureth sulfate”; CAS No.1335-72-4), like most raw materials used in cosmetics, is not a pure substance, but, depending on the preparation, is more likely a mixture of substances, the structures of which conform to the general formula
where n assumes numbers from 0 to 10 and m assumes numbers from 4 to 6. The lauryl ether derivative which predominates in the commerical products and gives them their name has m=5, n=2-3. Commercial products are, for example, Texapon® N 25, Texapon® N 40, Texapon® N 70 and Texapon® N 103 from Henkel KGaA.
There are, however, also other lauryl ether sulfates which have, as counterion, for example, unsubstituted ammonium ions or ammonium ions substituted by alkyl groups or hydroxyalkyl groups, but also magnesium and such like.
However, because of the ready availability, the acceptable price and the excellent washing properties of sodium lauryl ether sulfate, it will not be possible in practice to dispense with this substance entirely in the foreseeable future. Although lauryl ether sulfate-free preparations are known and entirely advantageous, they are characterized by other performance- or preparation-related or economic disadvantages.
The long-term application (for example longer than 1 hour) or repeated short-term application of anionic surfactants can lead to a reduction in skin moisture or to an increase in the transepidermal water loss (TEWL).
It is known per se to use sodium lauryl ether sulfate in combination with other surfactants as washing-active agent. The person skilled in the art who would then like to increase the skin compatibility of such preparations then replaces some of the sodium lauryl ether sulfate with milder surfactants. However, a reduction in foaming and/or cleansing performance usually has to be accepted as an undesired side effect. The aim was therefore to remedy this shortcoming.
In the attempt to increase the compatibility of lauryl ether sulfate on the basis of scientific laws without replacing the surfactant with other, better tolerated surfactants (=cosurfactants), the person skilled in the art is faced with the following, as yet unresolved, contradiction:
The skin compatibility of surfactants correlates with the monomer concentration/CMC of the surfactants. It does not increase further at concentrations above the CMC.
Imokawa G, Mishima Y.
Contact Dermatitis.
1979: 5: 357
Breuer M M.
J Soc. Cosmet. Chem.
1979: 30: 41
The degree of skin damage increases with increasing surfactant concentration—even above the CMC.
Wilhelm K P, Surber C, Maibach H I.
Arch. Dermatol. Res.
1989: 281: 293-295.
Because of this contradiction, it was not clear to the developer which laws can be used to prepare a milder formulation of a given surfactant system—in this case lauryl ether sulfate.
In various publications it has been speculated that there is a connection between the skin reaction and the adsorption of surfactants on the skin. However, all of the investigations relating to the adsorption of surfactants on the skin have been carried out either
in vitro on substances with limited similarity to the human skin (callous powder, skin powder, isolated human or mammal Stratum corneum)
Dominguez J G, Parra J L, Infante M R, Pelejero C M, Balaguer F, Sastre T.
J Soc. Cosmet. Chem.
1977: 28: 165
Garret H E.
Trans. of St. John's Hosp. Dermatol. Soc.
1965: 51: 166
Faucher J A, Goddard E D.
J Soc. Cosmet. Chem.
1978: 29: 323
Gibson W T, Teall M R.
Fd Chem. Toxic.
1982: 21: 581
ex vivo (excised human or mammal skin)
Fullerton A, Broby-Johansen U, Agner T.
Contact Dermatitis.
1994: 30: 222
or
in vivo using inadequate, irrelevant, due to being application-remote, or nonvalidated methods (indirect dyeing methods, extraction with water or acetone)
Imokawa G, Mishima Y.
Contact Dermatitis.
1979: 5: 357.
Adsorption measurements carried out under equilibrium conditions (long-term application) are of no relevance for application conditions (showering). Measurements described in the literature do not therefore adequately reflect the application situation and therefore produced irrelevant results.
At the 2
nd
Scientific Conference of the Asian Societies of Cosmetic Scientists, 1995, in Seoul, a paper entitled “Development of High-Safety Facial Cleansers through Reduction of Cutaneous Surfactant Adsorption” was presented which dealt with a the

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