Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – C-o-group doai
Reexamination Certificate
2000-12-15
2002-11-19
Pryor, Alton (Department: 1616)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
C-o-group doai
C514S738000, C424S405000
Reexamination Certificate
active
06482863
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to insect repellent formulations which contain polar solvents, have low viscosity, and are deliverable by piezoelectric device.
2. Description of the Related Art
Sprayable insecticidal compositions are known and generally comprise an insecticide and a solvent, in addition to other components. As the common insecticides are non-polar, the most common solvents used for this purpose are themselves non-polar, e.g. hydrocarbon solvents, such as hexane and petroleum solvent blends available under the trade names Shellsol and Isopar, for example.
While hydrocarbon solvents are effective to dissolve most common non-polar insecticides, they tend to have low flash points and to otherwise pose environmental and health risks. Therefore, it is desired to develop sprayable insecticidal compositions which avoid or minimize the use of these solvents. An insecticide formulation deliverable by piezoelectric delivery system which minimizes or avoids the use of non-polar solvents would be an advancement in the art.
Low-flash point solvents typically have high volatility. High volatility results in unintended evaporation of the insecticidal formulation—so-called “latent losses.” The problem of latent losses is particularly acute when the formulations are intended for delivery by a piezoelectric device over an extended period of time. For this and other reasons, there is a need in the art for insecticidal formulations using low-volatility solvents which are deliverable by piezoelectric device.
U.S. Pat. No. Re. 31,927 discloses electrostatically sprayable insecticidal formulations. High-boiling, high flash point hydrocarbon solvents, such as Isopar L are used to dissolve these insecticides, but lesser amounts of a polar component, such as n-butanol or cyclohexanone are added to raise the viscosity and reduce the resistivity of the final formulations. The viscosity of these solutions is believed to be too high for effective delivery using a piezoelectric delivery system.
U.S. Pat. No. 5,935,554 is directed to an aerosol space spray which, in some embodiments, is an insecticidal composition. The composition includes an insecticide, a solvent and a propellant, and in some cases a co-solvent. Where an insecticide is used, the solvent is Shellsol T, with ethanol as a co-solvent.
European Patent No. 897,755 discloses aerosol and piezoelectric-deliverable insecticide compositions. Mentioned as solvents for the piezoelectric systems are aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, esters, ethers, and ketones, with a particular preference given to aliphatic saturated hydrocarbons having 5 to 18 carbon atoms. EP 897,755 does not identify polar solvents that would dissolve insecticides, nor does it identify the properties that render a polar solvent suitable for use with a piezoelectric delivery system.
Typical prior art liquid atomizers utilize a large amount of propellants in the formulation. Conventionally, to obtain the desired characteristics of an aerosol for dispersion into the air, the formulations contain minimal active ingredients, a solvent for the active ingredient and a suitable propellant. The active ingredient usually constitutes less than 1% w/w. The solvent is present in the order of 10-20% w/w and the propellant constitutes 80-90% w/w. In most cases of such aerosol formulations, the solvent is a hydrocarbon solvent and the propellant a fluorocarbon or hydrocarbon. Alternatively, the propellant is partially substituted with water, wherein the weight percentage being water is in the range of 30-40% w/w. Therefore it is evident that to deliver one gram of insecticide conventionally requires the release to the atmosphere of between 80 and 250 g of volatile organic compounds (VOC's). Volatile organic compound (VOC) is the general name given for compounds with an appreciable vapor pressure, for example, fluorocarbons, hydrocarbons, e.g. butane, etc., commonly used as propellants.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an insecticidal composition which can be delivered with a piezoelectric delivery system. In particular, it is desired to provide an insecticidal composition with a sufficiently low viscosity that it can be delivered with a piezoelectric delivery system in the form of a fine mist or puff to provide continuous insect repellency throughout a room without settling too rapidly on surrounding surfaces.
Another object of the invention is to provide a low viscosity insecticidal composition that is not harmful or hazardous and which minimizes or eliminates the use of hydrocarbon solvents. In particular, it is desired to provide an insecticidal composition that exhibits overall low toxicity to humans and which will not be harmful to the respiratory system. It is also an object of the invention to provide an insecticidal composition that is non-flammable, and exhibits sufficiently low vapor pressure that latent losses are minimized when the formulation is used with a piezoelectric delivery device.
These and other objects of the invention are achieved by providing an insecticidal composition comprising an insecticide and at least one polar solvent having a vapor pressure below about 5 mm Hg at 25° C., where the insecticidal composition has a viscosity lower than 2.6 centipoise at 25° C. In preferred embodiments, the polar solvent comprises dipropylene glycol dimethyl ether.
Preferably, more than 75% of the solvent is a polar solvent or combination of polar solvents and co-solvents. In particularly preferred embodiments, the composition is substantially free of hydrocarbon solvents.
In preferred embodiments, the insecticidal composition according to the invention comprises an insecticide in an amount between about 3 percent by weight and about 20 percent by weight of the composition, while the solvent or solvents comprise between about 80 and 97 percent by weight of the composition.
The preferred formulations according to the invention are not emulsions and do not require propellants for delivery.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As understood by those of skill in the art, a piezoelectric liquid atomizer comprises an orifice plate which is vibrated by an actuator made of a piezoelectric material, such as lead zirconate titanate (PZT) or lead metaniobate (PN). Upon application of an alternating electrical field across the piezoelectric actuator it expands and contracts and causes the orifice plate to vibrate. The vibrating orifice plate contacts a liquid and as a result liquid droplets are propelled ultrasonically through the orifices in the plate and ejected into the atmosphere.
The diameter of the orifices in the orifice plate of a piezoelectric liquid delivery system determines the size of the droplets produced. The diameter generally ranges between about 1 and about 25 microns, preferably from about 4 to about 10 microns. The size of the orifices is tailored such that energy consumption by the device is minimal while the size of the droplets is small enough to permit the droplets to remain suspended in the air and evaporate without collecting on the surrounding surfaces.
Droplets having an average size greater than about 15 to 20 microns and larger have a tendency to settle out of the air, onto the delivery device and other surfaces. Thus, it is advantageous to provide a solution that will produce droplets having a size less than 20 microns, preferably less than 15 microns. An average droplet size of about 10 microns has been observed to stay suspended in air for a suitable length of time to effectively kill insects in a room.
The low viscosity insecticidal compositions according to the invention are particularly suitable for piezoelectric delivery systems powered by low voltage batteries, such as conventional “A”, “AA”, “AAA”, “C”, “D” cell batteries and the like. In a particularly preferred embodiment, the insecticidal composition of the present invention is adapted for use with a piezoelectric deliv
Ananth Gopal P.
Gartland Kevan
Munagavalasa Murthy S.
Pryor Alton
S. C. Johnson & Son Inc.
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