3L~3~8~6 This invention relates to chemical compositions and more particularly to chemical compositions useful as insect repellents.
Insect repellents for use by humans, animals, etc.
may be applied to exposed portions of the human skin as well as to clothing, for the purpose of deterring the approach and landing of insects thereon so as to avoid stings and bites and subsequent inflammation and/or infection. Various repellent formulations have been developed in recent years, in spray, lotion or cream form, for application to the desired area. However, in order for the repellent to be acceptable, aside from being effective to repel insects and the like, it must also be agreeable to the user, and be essentially free from harmful side effects. Thus, repellent compositions should not be irritating to the skin. Moreover, the composition should be sincerely agreeable to the user particularly with respect to smell and color. The composition should be heat stable within the anticipated temperature ranges of use. Additionally, and importantly, the composition should be capable of remaining on the area of application for an optimum length of time and should be capable of ready removal from the site when desired.
Many chemicals capable of eliciting a negative chemotactic response on insects are known. Not all, however, for the reasons given above can be utilized as repellents by humans or animals. Moreover, after prolonged ~3~B~6 use, insect repellent compositions may become insect tolerable either by manifestation of an inherent biological defense or by mere continued exposure ox the insects to a particular repellent. In either case, the efficacy of the composition is reduced.
The present invention provides a novel insect repellent composition which comprises a combination of chemical compounds. The composition of the present invention, whilst including known compounds, provides a repellent effect which is extremely durable, and appears to outlast any of the commercially available formulations, even under the most adverse, insect-infested conditions Thus, according to one aspect of the present invention there is provided an insect repelling composition comprising as active ingredients citronella or lavender oil, dimethylphthalate and 2-ethylhexane-1,3-diol in admixture with a suitable inert carrier.
As previously mentioned, preferably the composition of this invention should have an acceptable color and odor. These properties are determined to some extent by the active ingredients of the composition. For this reason it is preferable to limit the proportion of the citronella compound or lavender oil of the composition of the present invention to within the approximate range of from 5-20%
preferably about 10-15% and most preferably about 12.5% by weight, based on the total weight of the active ingredients.
To ensure that an insect repelling composition is compatible with human and animal skin and does not cause excessive irritation or other undesirable side effects, the concentration of active ingredients in the composition should be limited to a safe level, consistent with insect repelling potency.
Thus, the composition of the present invention desirably has an active ingredient content of from about 25% to about 60~ by weight based on the total weight of the composition. Accordingly, it is preferred to provide, as active ingredient in admixture with citronella or lavender oil, the dimethylphthalate component in a range of from about 35~ to about 65~ based on the total weight of the active ingredients, more preferably in the 45-55%
approximate range and most preferably as about 50% of the total weight of the active ingredients.
Preferably, the 2-ethylhexane-1,3-diol component of the composition of the present invention is present in the range of from about 30% to about 45~ based on the total weight of the active ingredients, more preferably from about 35% to about 40% and most preferably about 37.5%
based on the total weight of the active ingredients.
where are numerous substances that may be used alone or in combination as a base or vehicle for the active ingredients. For the most part, these are standard, inert, biologically acceptable substances known and used in various types of cosmetic formulations. The specific formulation of the vehicle is largely dependent on the - ~23~826 desired consistency of the compositions. Typical such formulations provide use of the active ingredients in the form of sprays, lotions and creams. In each case, the base should preferably have an emollient and lubricating effect on the skin and preferably should be of acceptable color and odor. The base may be a natural or synthetically prepared substance or substances. Suitable bases for use in the composition include: petroleum hydrocarbon jelly ('1vaselinen*), lard, glycerin, cocoa butter (theobroma oil), olive oil, lanolin, propylene glycol, beeswax, paraffins such as parowax*l and polawax*2,stearic acid, and mineral oil. One function of the base is to regulate the consistency of the final composition. The amount of base to be used in the composition thus depends on the type and number of bases chosen. If using a single component as a base for the active ingredients, it is preferable when the cream-form of the invention is desired, to use one with semi-solid consistency so that the finished product is not * - Trade Mark l - domestic grade paraffin; mop. 52C; specific gravity 0.90 at 25C, 0.769 at 80C, 0.758 at 100C; available from Essay Petroleum Canada
2 - reaction product of higher fatty alcohols and ethylene oxide; creamy, wax-like, non-ionic solid used as emulsifier; my 48-52C, available from Coda Canada Ltd., 78 Tisdale Avenue, Toronto, Ontario, Canada 12308~6 too liquid. If using a combination of two or more components as a base they should be selected such that the final consistency of the base is creamy or semi-solid, also, to ensure that the final product is not too liquid.
The overall amount of the base present in the composition may be in the range 40-75% (by weight).
Further to ensure the suitable, semi-solid consistency of the cream form of the final composition according to the invention, a thickening agent may be - pa -12~8216 incorporated. A thickening agent, when used in suitable amounts, thickens the active ingredients base mixture to a creamy or semi-solid texture such that it may be easily applied to the skin and will not readily evaporate from or significantly absorb into the skin. Furthermore, the thickening agent may have the secondary purpose of adding to or lightening the color of the composition. Thickening agents useful in this invention should he non-irritating and light in color and odor. One or a combination of several substances may be used.
The amount of thickening agent to be used is dependent on the nature and consistency of the base used.
Too little thickener may result in an oily composition and too much thickener may result in a crumbly composition.
lo Examples ox suitable such thickeners include cornstarch, talc and chalk.
The preferred compositions according to the invention are formulated to be stable, both chemically and physically, over the full range of temperatures to be I encountered during storage transportation and use. Thus they should be able to withstand such temperatures, without chemical change, and with only minor changes in physical state or condition.
The composition of the invention may be prepared in a number of ways, all of which basically involve the physical mixture of the desired and required components.
The components may be put in a blender or chopper and .
combined by a high speed mixing process or alternatively, the components may be combined manually. In the preferred method of preparation, the base is heated to the point of softening or melting thereafter the active ingredients are added and mixed thoroughly with the base. The mixture may then be allowed to cool somewhat, prior to pouring into individual containers, or may be poured directly from the batch container to the individual containers prior to cooling. In the alternative, all of the ingredients may be mixed together initially, then heated with stirring to a temperature above the melting point of the base materials, e.g. about 185 poured into containers an allowed to cool.
The most preferred embodiment of a composition according to the invention comprises citronella, dim ethyl-phthalate and 2-ethylhexane-1,3-diol as active ingredients in admixture with Polawax, Porks and white Vaseline The cream thus formed has been found to be exceptionally effective and durable as an insect repellent.
The following specific example illustrates the most preferred embodiment of the invention, but does not limit it.
Example An insect repellent composition according to the present invention was prepared with the following composition:
~23~8~6 Ingredient% by weight dimethylphthalate 20 2-ethylhexane-1,3-diol 15 citronella 5 white Vaseline 45 polawax 10 porks 5 In preparing the composition, polawax and porks were heated to 185 in a conventional blender and mixed, thereafter white Vaseline was added and mixed therewith, to form a molten mixture. Dimethylphthalate, citronella and 2-ethylhexane-1,3-diol were consecutively added to the melt and mixed therein. The composition was allowed to cool and set about 1 hour) and the resultant product had a creamy paste-like texture and consistency, off-white in color and with an acceptable, light odor.
The formulation was tested by application to the exposed skin of a human, who then conducted manual work in an insect-infested forest area under conditions of relatively high humidity and heat. A single application was found to afford effective insect repellence over a prolonged period of no less than six hours. It successfully and effectively repelled black flies, mosquitoes, horseflies and similar type insects.