Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Reexamination Certificate
2000-05-23
2004-09-21
Padmanabhan, Sreeni (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
C514S844000, C514S937000
Reexamination Certificate
active
06793929
ABSTRACT:
DESCRIPTION
The present invention relates to cosmetic and dermatological preparations, in particular those of the water-in-oil type, to processes for their preparation and to their use for cosmetic and medicinal purposes.
The human skin is man's largest organ and performs a number of vital functions. Having an average area of about 2 m
2
in adults, it has a prominent role as a protective and sensory organ. The purpose of this organ is to transmit and avert mechanical, thermal, actinic, chemical and biological stimuli. In addition, it has an important role as a regulatory and target organ in human metabolism.
The main aim of skin care in the cosmetics sense is to strengthen or rebuild the skin's natural function as a barrier against environmental influences (e.g. dirt, chemicals, microorganisms) and against the loss of endogenous substances (e.g. water, natural fats, electrolytes), and also to assist its horny layer in its natural regeneration ability where damage has occurred.
If the barrier properties of the skin are impaired, increased resorption of toxic or allergenic substances or infection 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 sebum and water caused by daily washing. This is particularly important if the natural regeneration ability is inadequate. Furthermore, skin care products should protect against environmental influences, in particular against sun and wind, and delay skin ageing.
Medicinal topical compositions usually comprise one or more medicaments in an effective concentration. For the sake of simplicity, in order to clearly distinguish between cosmetic and medicinal use and corresponding products, reference is made to the legal provisions in the Federal Republic of Germany (e.g. Cosmetics Directive, Foods and Drugs Act).
Emulsions are generally taken to mean heterogeneous systems which consist of two liquids which are immiscible or miscible with one another only to a limited extent, which are usually referred to as phases. In an emulsion, one of the two liquids is dispersed in the form of very fine droplets in the other liquid.
If the two liquids are water and oil and oil droplets are very finely dispersed in water, 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 structure being determined here by the oil.
The person skilled in the art is of course aware of a large number of ways to formulate stable W/O preparations for cosmetic or dermatological use, for example in the form of creams and ointments which can be spread in the range from room temperature to skin temperature, or as lotions and milks, which are more likely flowable in this temperature range. However, there are only a few formulations in the prior art which are of sufficiently low-viscosity that they would, for example, be sprayable.
In addition, low-viscosity preparations of the prior art frequently have the disadvantage that they are unstable, and are limited to a narrow field of application or a limited choice of feed materials. Low-viscosity products in which, for example, strongly polar oils—such as the plant oils otherwise frequently used in commercially available products—are sufficiently stabilized are therefore currently not on the market.
The term “viscosity” means the property of a liquid to resist the mutual laminar displacement of two neighbouring layers (internal friction). This so-called dynamic viscosity is nowadays defined according to &eegr;=t/D as the ratio of shear stress to the velocity gradient perpendicular to the direction of flow. For Newtonian liquids, &eegr; is a material constant having the SI unit Pascal second (Pa·s) at a given temperature.
The quotient &ngr;=&eegr;/&rgr; from the dynamic viscosity &eegr; and the density &rgr; of the liquid is referred to as the kinematic viscosity &ngr; and is given in the SI unit m
2
/s.
Fluidity (&phgr;) is the inverse of viscosity (&phgr;=1/&eegr;). In the case of ointments and the like, the use value is inter alia codetermined by the so-called tack. The tack of an ointment or ointment base or the like means its property to draw threads of varying lengths when a small sample is removed; accordingly, a distinction is made between short- and long-stretch substances.
Whilst the graphical representation of the flow behaviour of Newtonian liquids at a given temperature produces a straight line, in the case of so-called non-Newtonian liquids considerable deviations often arise, depending on the velocity gradient D (shear rate &ggr;) or the shear stress &tgr;. In these cases, the so-called apparent viscosity can be determined which, although not obeying the Newtonian equation, can be used to determine the true viscosity values by graphical methods.
Falling-body viscometry is suitable only for investigating Newtonian liquids and gases. It is based on Stokes's law, according to which, for the falling of sphere through a liquid which flows around it, the dynamic viscosity &eegr; can be determined from
η
=
2
r
2
(
ρ
K
-
ρ
F
I
)
·
g
9
·
v
where
r=radius of the sphere, v=fall velocity, &rgr;
K
=density of the sphere, &rgr;
FI
=density of the liquid and g=acceleration of the fall.
W/O emulsions with a high water content and any desired viscosity which moreover have storage stability, as is required for marketable products, in particular those with a relatively high water content of more than 75% by weight water content and nevertheless having very good sensory properties continue to be a weighty problem. As a result of the very high water content of the emulsions, they “break” on the skin particularly rapidly—sensorily unpleasant—into their main constituents (hydrophilic and hydrophobic components). Solutions have hitherto only been attempted for W/O emulsions comprising predominantly nonpolar lipids. Accordingly, the supply of formulations of this type is extremely low.
An object of the present invention was to provide preparations which can be formulated in virtually any viscosities and which do not have the disadvantages of the prior art.
Another object of the present invention was to provide preparations which can be charged with a high content of water-soluble and/or water-miscible substances having cosmetic or dermatological activity, without impairing the galenical quality or other properties of the preparations.
According to K. J. Lissant:
The Geometry of High
-
Internal
-
Phase
-
Ratio Emulsions
; Journal of Colloid and Interface Science 22, 462-468 (1966), emulsions with an internal phase of more than 70% are defined as so-called high internal phase emulsions. The preparation of stable, flowable water-in-oil emulsions with a water content of more than 80% is very difficult. In particular, “high internal phase” W/O emulsions with a very high water content of more than 85% (“very high internal phase” W/O emulsions) are not accessible.
The technique of varying the phase volume ratio (i.e. incorporating higher amounts of liquid lipids) which is usually used for water-in-oil emulsions can, because of the low lipid content, be used only to a limited extent in the case of high internal phase W/O emulsions, or not at all in the case of very high internal phase W/O emulsions.
Surprisingly, it has been found that water-in-oil emulsions
(a) with a content of water and optionally water-soluble substances totalling at least 75% by weight, and with a content of lipids, emulsifiers and lipophilic constituents totalling at most 25%, preferably at most 20%, based in each case on the total weight of the preparations,
(b) whose oil phase is chosen from the group of lipids or lipid mixtures, where the total polarity of the lipid phase is between 20 and 30 mN/m,
(c) comprising at least one interface-active substance, chosen from the group of
Bleckmann Andreas
Fecht Stephanie von der
Kropke Rainer
Nielsen Jens
Schneider Gunther
Beiersdorf AG
Norris McLaughlin & Marcus PA
Padmanabhan Sreeni
Wells Lauren Q.
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