Cosmetic stick composition

Details Cosmetic stick composition Cosmetic stick composition

2000-02-16

2002-02-26

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

C424S066000, C424S059000, C424S068000, C424S060000

Reexamination Certificate

active

06350460

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an improved cosmetic stick made with a combination dipropylene glycol, diethyl phthalate and stearyl alcohol. This stick exhibits improved stability and allows for the use of reduced amounts of dipropylene glycol.
BACKGROUND OF THE INVENTION
Previous attempts to form stable sticks have been made using a variety of different chemistries. While ingredients such as stearyl alcohol and polyhydric alcohols such as dipropylene glycol are useful in forming cosmetic sticks such as lipsticks, sunscreens, solid perfumes, antiperspirants, deodorants, etc., there can be problems in stability which have unwanted side effects, such as high package elevating torques. This can lead to a compromise in the integrity of the product container.
Diethyl phthalate itself has previously been taught as a diluent, solubilizing agent or extender for the perfume art as in U.S. Pat. No. 5,833,999 to Trinh et al (for example, at column 4, lines 25-35) and U.S. Pat. No. 5,849,310 to Trinh et al (for example, at column 5, at 25-34).
It was noticed by us that the inclusion of fragrancing material was helpful in producing improved sticks in certain cosmetic stick products with certain chemical components. Problems sometimes arose, however, when fragrance was not included in the formulation. Since fragrance compositions sometimes contain incidental amounts of diethylphthalate (“DEP”), such as in amounts on the order of 0.02% by weight based on the total weight of the composition, it may have been this ingredient that was causing some improvement. It has now been discovered that the deliberate use of diethyl phthalate in combination with a sufficient amount of dipropylene glycol and stearyl alcohol, can be used to form satisfactory cosmetic sticks even in fragrance free products.
Thus it is an object of the present invention to create improved cosmetic sticks, especially those that are better able to be used in rigid packaging after formulation. It is a further object to form improved cosmetic sticks with reduced amounts of dipropylene glycol. These and other objects of the invention will be apparent from the following description.
SUMMARY OF THE INVENTION
The cosmetic stick compositions of the invention are made by combining:
a) 10-24% of stearyl alcohol (particularly 18-24%);
b) 37-55% of a volatile silicone (particularly 50-55%);
c) 18-25% of a cosmetically active ingredient;
d) 0.05-0.15% dipropylene glycol;
e) 0.06-2.0% (particularly 0.10-1.0%, and more particularly 0.30-1.0%) of a co-solvent (particularly diethyl phthalate) with a solubility parameter in the range of 19-20; and
f) 1-8% of a high melting point wax (melting point in the range of 65-102 degrees C.);
wherein the cosmetic stick has a three point flexure of at least 0.093 MPa±0.01 and an elevating torque that does not exceed 90% of the strength rating of the package in Newton-meters; and wherein all percent are weight percents based on the total weight of the composition.
DETAILED DESCRIPTION OF THE INVENTION
The importance of this invention is the creation of a more structurally desirable cosmetic stick. The use of a gellant such as stearyl alcohol in combination with a solvent such as dipropylene glycol does not always produce a product with a satisfactory shelf life as reflected in a satisfactory combination of hardness properties and elevating torque. It has been found that the use of a co-solvent such as diethyl phthalate works remarkably and surprisingly well in this system. This is in contrast to a system containing propylene glycol or tripropylene glycol which does not work satisfactorily as a substitute for dipropylene glycol in this invention. A particular embodiment of interest is a fragrance free system.
Another important aspect of this invention is that it allows for the formation of a suitable cosmetic stick with a much reduced amount of the dipropylene glycol solvent than would normally be required. For example, sticks have been made with {fraction (1/10)} of the usual amount of dipropylene glycol. It has been shown that in systems that use dipropylene glycol alone as the solvent, one of two situations occur. In the first situation, if enough DPG is added to form a stick with sufficient hardness (for example, a three point flexure of at least 0.093 MPa±0.01, where when using a large sampling no more than a few percent of the data points fall below the lower limit) the elevating torque is not satisfactory (for example, it exceeds a level of 90% of the value of the strength of the package rating in N-m) resulting in a problem with the ability of the stick to be contained in the packaging. In the second situation, the amount of DPG is reduced, but the hardness of the stick is not satisfactory. This occurs even if the DPG level is reduced by only 30% of the normal amount.
Parameters for hardness and elevating torque have been described in terms of certain numerical limits (a three point flexure of at least 0.093 MPa±0.01 and an elevating torque that does not exceed 90% of the strength rating of the packaging). It should be noted, however, that the elevating torque starts out as an initial value at the time of manufacture and then increases over time depending on the amount of moisture the composition absorbs over time. The value of the elevating torque will plateau out a final value at about 6 months of age. From a statistical standpoint, the cosmetic sticks of the invention should be made so that no more that 4% of the sticks made in a given batch exhibit a three point flexure less than 0.093 MPa±0.01 and an elevating torque (after 4-6 months) that exceeds 90% of the strength rating of the package in Newton-meters.
In one particular example, a package of the type described in U.S. Pat. No. 5,275,496 (incorporated by reference in its entirety herein) can be made to withstand a force of X N-m. In that case it is preferred that the composition of the invention be made to have an initial elevating torque value (as measured within 2 weeks of manufacture) of less than X-2 N-m. For example if the packaging is rated at 4.1 N-m the initial elevating torque value should be less than 1.76 N-m. Other equivalents are possible. For example, for a package rated at being able to withstand a force of 5.1 N-m, an initial elevating torque not exceeding 2.76-2.79 may be used.
For packaging that is not completely air tight (for example, a package of the type described in U.S. Pat. No. 5,275,496), a greater increase in elevating torque can be expected over the shelf life of the product (for example, over a period of 6 months) than for more air-tight packaging. Thus, for packaging that is air-tight a higher initial elevating torque value can be tolerated, as long as the final value (for example, after a shelf life of 6 months) is less than the 90% limit described above.
With respect to the components used to make this invention, the volatile silicone may be selected from the group consisting of volatile, low, molecular weight polydimethylsiloxane materials which are either linear or cyclic, with particular example being cyclomethicone such as Dow Corning 245 Fluid, Dow Corning 345 Fluid, SF-1204 (GE Silicones) which are cyclic dimethyl polysiloxane compounds where the ring may contain from between 4-6 silicone atoms.
The cosmetically active ingredient may be selected from the group consisting of topically active compositions that act upon contact with skin or that are cosmetic enhancements in their own right such as lipsticks and eye shadow sticks. These ingredients can be added separately or added with any of the ingredients in the cosmetic stick. Examples of cosmetically active ingredients include sun screens, coloring agents, topical anesthetics, insect repellents, antimicrobial compounds, antifungal compounds, and antiperspirant actives.
Antiperspirant actives include conventional aluminum and aluminum/zirconium salts, as well as aluminum/zirconium salts complexed with a neutral amino acid such as glycine, as known in the art. See each of European Patent Application Number 51

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