Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
2002-02-05
2002-12-31
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S401000, C424S060000, C424S078020, C424S078080, C424S400000
Reexamination Certificate
active
06500411
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a multifunctional particulate additive for personal care and cosmetic formulations, and a process of making the same. More specifically, it relates to the following:
i) an additive composition that when added as a component in personal care and cosmetic formulations, can simultaneously serve one or more of the following purposes: i) improve the efficacy of sunscreen actives used as ultraviolet radiation (UVR) filters, ii) thicken hydrophilic solvents such as water, glycols, glycerine, and alcohols or mixtures of these solvents, iii) emulsify and stabilize oil droplets in oil-in-water (O/W) emulsions, and iv) function as an antioxidant;
ii) an additive that comprises a particulate-based thickener/gellant such as smectite clays and/or a particulate-based UV-filter such as titanium dioxide or zinc oxide, and certain types of dispersants or surface-modifiers for these particulate materials;
iii) natural polymer-based surface-modifiers that contain polarizable functional groups such as phenolic, catecholic, and other aromatic groups, as well as hydrogen bond-forming groups such as hydroxyl, phenol, carbonyl, and carboxyl groups, which in turn enable the adsorption of these macromolecules on a variety of particulate surfaces;
iv) natural polymer-based surface-modifiers of the type mentioned above, contained in the multifunctional additive, that can emulsify and stabilize oil droplets in an O/W emulsion, such that the polymer molecules act as an emulsifier/stabilizer when the multifunctional additive is used as a component in an O/W emulsion-based cosmetic formulation;
v) the use of the foregoing natural polymers as dispersants or surface-modifiers in order to increase the number-concentration of particles of the aforementioned particulate materials in a suspension, and/or to impart colloidal stability (stability against coagulation) of such suspended particles, which in turn promotes and/or preserves the thickening or UV-filtering ability of these particulate substances in cosmetic dispersions;
vi) an additive that can enhance the effectiveness of organic sunscreen-actives, and thus increase the sun protection factor (SPF), a measure of efficacy of UV-filters, of sunscreen products containing these UV-filters;
vii) the use of natural polymer-based surface-modifiers as components in the multifunctional additive, that are essentially polyphenols, by virtue of which the additive delivers antioxidant functionality;
viii) the use of surface-modifiers as components in the multifunctional additive, that are natural polymers, used in combination with natural thickeners, such as smectite clays, and natural particulate UV-filters, such as titanium dioxide and zinc oxide, catering to the consumer demand for the use of natural ingredients in cosmetics;
ix) a method of delivering various functional properties listed in section i), that are useful in personal care and cosmetic formulations, through a single additive and thus providing ease and cost-savings in product formulations;
x) an in-situ method for surface-modifying a particulate material such as smectite clays and thus producing the particulate in an aqueous gel, that allows the thickener functionality of the particulate to be realized in one or more hydrophilic solvents.
Examples of personal care and cosmetic products where the additive composition of the present invention may be used may include skin-care creams, lotions, facial creams, and sunscreens; hair care products such as shampoos, conditioners, colorants, and hair styling aids; liquid makeups, foundations, shaving creams and lotions. The additive can also be used in topical pharmaceutical formulations that can benefit from enhanced protection of the skin from harmful UV rays. The foregoing personal care, cosmetic, and pharmaceutical products can be in the form of oil-in-water emulsion or water-in-oil emulsion, or gel.
BACKGROUND OF THE INVENTION
I. Particulate-based Thickener
Smectite clays are a class of inorganic particulate materials that occur as stacks of individual, planar silicate layers referred to as platelets in the clay-literature. Examples of smectite clays include montmorillonite, bentonite, bidelite, hectorite, saponite, and stevensite.
These clays are popular particulate gellants or thickeners for aqueous compositions, particularly oil-in-water (O/W) emulsions. Fundamentally, the formation of particulate gels is a manifestation of suspended colloidal particles forming a network structure that entraps and thus immobilizes the suspending medium. Clay-based gels may form when individual platelets or stacks of a few aggregated platelets (tactoids) engage in interparticle associations with their neighboring platelets. If these particle-to-particle links extend throughout the total available volume, a gel, comprised of a continuous, linked particulate structure that entraps within itself the suspending medium, is formed. Such interparticle associations are governed by the interplay between the attractive and repulsive forces that generally act between particles suspended in a liquid. Hydrodynamic effects due to the orientation of planar clay particles in a flow-field may also contribute to the rheological properties of clay suspensions.
Clearly, the strength of particulate gels will depend on the number of interparticle associations in a given volume of the gel, implying that the greater the number-concentration of suspended particles, the stronger is the gel. Also, a dominance of the attractive interactions over the repulsive interactions, the likelihood of which increases with decrease in interparticle separation distance, is required for suspended particles to associate with their neighbors. An increase in the number-concentration of particles will tend to reduce their separation distances, an effect that could be especially dramatic for planar particles since the separation distance between two adjacent platelets will vary along their lengths when their faces do not align in parallel configuration. Nonetheless, too strong an attraction between adjacent clay platelets may draw them into strong association or coagulation, minimizing the particle number-concentration, once such coagulation occurs via face-to-face associations. In fact, it is these attractive forces that hold the clay platelets together in a stack.
Considering the above, the key to making clay-based gels is to ensure that there is sufficient interplatelet repulsion for the clay platelets to exfoliate (delaminate or deflocculate) under shear, releasing a large number of platelets as individual platelets or tactoids having fewer stacked platelets, that would then be available to form a particle network. On the other hand, in order to form a voluminous network structure, the net interaction (the sum of attractive and repulsive forces) between the delaminated platelets must be such that they can remain “bound” (attracted) to their neighboring platelets without being drawn into coagulation with their neighbors via face-to-face association. Accordingly, the gel-network may form if the delaminated platelets, while being separated from the surrounding platelets by as thick as possible an intervening layer of the suspending medium, reside in a relatively deep minimum in free energy of interaction with the neighboring platelets. Albeit physically separated from their neighbors, the individual platelets are no longer free to move independently, being trapped in a free energy minimum, producing in effect a continuous particle network, and hence thickening or gelation. Yet another way by which clay-based gels may form is where clay platelets coagulate due to edge-to-face associations, forming the so-called “card-house” structure described in clay literature.
Forming clay-based gels, as an outcome of the aforementioned phenomena, would require tuning of interplatelet forces, such as by modification of the clay-surface. Adding complexity, these attractive and repulsive forces may vary with the properties of the suspending medium. Evidence of this may be found in
Darlington, Jr. Jerald W.
SenGupta Ashoke K.
Spindler Ralph
Amcol International Corporation
Dodson Shelley A.
Marshall Gerstein & Borun
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