Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
1999-08-16
2001-08-28
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S060000, C424S069000, C424S078030, C424S078320, C424S489000
Reexamination Certificate
active
06280710
ABSTRACT:
FIELD OF INVENTION
This invention relates to processes for producing small particle size powder alloys from molten mixtures and for producing recrystallized small particle size dispersions from high temperature solvent solutions. These alloys and dispersions are useful in both clear and color formulations for personal care preparations, especially cosmetics and particularly cosmetic sunscreen formulations. In addition, this invention relates to the use of selected cosolvents in the process of recrystallization to form small particle size dispersions. Moreover, this invention relates to the inclusion of an insoluble nucleating agent in the recrystallization process to enhance small size crystal growth as well as dispersion processing, and to improve the formula properties of the powder alloys and recrystallized dispersions. Furthermore, this invention relates to the use of the disclosed processes to prepare improved personal care formulae, especially improved cosmetics formulae, and in particular improved sunscreen formulae and sunscreen-containing cosmetic formulae.
BACKGROUND OF THE INVENTION
The recrystallization of polar solutes with marginal solubility in non-polar solvents is known. For relatively pure solutes, enhancing solubility by increasing the temperature of the solvent may be sufficient to effect a suitable recrystallization result. However, conventional methods of recrystallization may be unsuitable for mixtures in which impurities are present, or more than one solute is employed, or an insoluble substance is present during recrystallization, since the nature of mixtures is to prevent or retard crystal growth of selected ingredients. As a result, small size crystals and small size dispersed particles cannot be consistently and reproducibly obtained using conventional recrystallization techniques.
The recrystallization of organic solids to produce small crystals, leading to powders and dispersions of small particle size, i.e., ranging from less than one to about twenty-five microns, is important in several formulation-based industries. As used herein, a formulation-based industry is an industry whose products are based on mixtures of ingredients, in which each ingredient retains most of its original chemical properties despite being combined with the other ingredients. Such industries include, but are not limited to, those which produce personal care products, cosmetics, and over-the-counter drug formulations such as antiperspirants and sunscreens.
Conventional dispersion methods such as high speed, high shear stirring and solvent recrystallization are widely used in these industries, but these methods do not readily create a uniform dispersion of very small particle size unless the solid component has been micronized by prior processing, or has undergone purification processing, or has been processed through expensive and time-consuming specialized equipment, e.g., high-pressure homogenizers.
Therefore, there exists a need in the formulation-based industries to reduce the particle size of certain ingredients, and to formulate with such ingredients in either powder form or dispersed form, without premicronization or purification processing or specialized equipment. This has become especially evident in the personal care and cosmetics industries, the latter in particular for the formulation of sunscreens and cosmetics containing sunscreens.
Due to the increasing use of both natural and synthetic organic ingredients, the personal care industries and especially the cosmetics industry have recently been seeking a greater degree of perceived topical benefits from products applied directly onto the stratum corneum. These benefits include lubricity, evenness of application, spreadability, lack of oiliness or stickiness, greater skin adhesion and a more comfortable, even pleasant, skin feel.
Thus, a need exists in the cosmetics and personal care industries for new formulations of fine particle size powders and dispersions, and for processes to produce such formulations that are efficient, effective, and yield products with a uniform particle size that are comfortable to use. In the case of cosmetics, sunscreens and sunscreen-containing cosmetics, a need exists for formulations that are lubricous, have a non-oily, non-greasy, non-sticky, pleasant skin feel, and are efficacious in that the expected Sun Protection Factor (“SPF”) value of a sunscreen formula is not impaired.
Accordingly, it is an object of the present invention to provide improved processes for producing small particle size powders, and recrystallized mixtures and dispersions of small crystal size, that function as active ingredient delivery systems within the types of industries described.
Another object of the invention is to provide an improved process by which to recrystallize an insoluble active ingredient, thereby affording the formulator substantial ease of use when incorporating such an active ingredient into finished product formulae.
Still another object of the invention is to provide improved fine particle size powders, mixtures and dispersions
A further object of the invention is to provide improved topical ingredients for personal care products such as cosmetics and sunscreens that are lubricous and aesthetically pleasing to the skin.
Yet another object of the invention is to provide lubricous mixtures that are efficacious, particularly in the active ingredient delivered.
SUMMARY OF THE INVENTION
The present invention employs chemical means of enhancing solubility at elevated temperature, followed by rapid cooling to induce recrystallization from a solution or from the molten state, as well as optional fine particle nucleation. As a result, neither premicronization, nor high purity, nor special equipment is required in order to produce powder mixtures and dispersions of small particle size.
In accordance with one embodiment of the present invention, a process for producing via recrystallization powder alloys of small particle size, for use in both color and clear formulations in personal care products and the like, comprises the steps of combining at least one first solid organic wax lubricant (lubricating wax), with at least one active ingredient. An active ingredient is a compound having physical and/or chemical characteristics which would be considered necessary or desirable in a finished product (i.e., the compound would be useful as an active ingredient of the finished product), provided that the compound could be introduced or delivered in a usable form, that is, as a powder or as a dispersion incorporating very small size particles of the compound.
Active ingredients useful in the present invention include those that may be useful in a personal care product, such as hydrogenated jojoba, or such as a material that is capable of absorbing and/or blocking ultraviolet light and which is therefore useful in sunscreen formulations and in sunscreen-containing cosmetic formulations (referred to herein as “sunscreen actives”). In accordance with the present invention, the active ingredients can be delivered as a wax alloy powder, rather than as the more common form, an emulsion. Emulsions are conventional in the prior art but are susceptible to weakening or destruction of desirable physical properties when a formulation containing the emulsion is spread upon the skin.
In this embodiment of the invention, the sunscreen active or hydrogenated jojoba is selected as the active ingredient. Since most organic wax lubricants are non-polar and therefore not directly miscible with hydrogenated jojoba or with a polar organic sunscreen active, even at elevated temperatures, the other component of the alloy, the solid organic wax lubricant, is selected from a group of polar waxes having chemical structures that impart the above-described desired physical properties to the resulting alloy powder.
The solid organic wax lubricant and the active ingredient are heated together to an elevated temperature with stirring, after which the molten alloy solution is cast as a thin sheet and thereby cooled. As used herein,
DeBlasi Douglas S.
Pe Roy
Sui Manshi
Dodson Shelley A.
Shamrock Technologies Inc.
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