WO2002023989A1

WO2002023989A1 - Insecticidal microcrystalline dry aerosol spray

Info

Publication number: WO2002023989A1
Application number: PCT/US2001/029107
Authority: WO
Inventors: Trent R. Northen
Original assignee: The Clorox Company
Priority date: 2000-09-20
Filing date: 2001-09-10
Publication date: 2002-03-28

Abstract

An insecticidal formulation which provides excellent secondary insect kill is disclosed herein. The insecticidal formulation comprises deltamethrin volatile solvents such as octane, propellants such as fluorinated hydrocarbons. The solvents and propellants must flash off at room temperature when sprayed to result in microcrystals of the deltamethrin being deposited on the target surface.

Description

INSECTICIDAL MICROCRYSTALLINE DRY AEROSOL SPRAY

Background and Summary of the Invention:

This invention relates to a novel insecticiάal formulation that forms microcrystalline

(^' insecticiάe when the formulation is sprayeά. Using the formulation of this invention crystals form rapiάly, precipitating insecticiάe before it has a chance to absorb into porous surfaces, as in the case of conventional formulations άelivereά as an aerosol. The formulation of this invention has the aάάitional benefit that the microcrystals are easily pickeά up from a surface by the insects, particularly targeteά are cockroaches anά ants, who then transfer the active formulation to other cockroaches anά ants. This proviάes the formulation the aάvantageous property of what is known in the art as seconάary kill. By seconάary kill a cockroach that has not been άirectly exposeά to the insecticiάe is killed either by contact to exposeά cockroaches or to surfaces upon which exposeά insects have depositeά the insecticiάe.

It is extremely άesirable for a proάuct to have gooά residual performance and seconάary kill. This is because the roaches are most active at night, hence this novel formulation will be available for the cockroaches when they are most active. With favorable secondary kill properties an insecticide in a preferred formulation, such as in the instant formulation, the insects, themselves, will spread the active formulation to their habitat.

Conventional insecticide products rely on the user to spray or apply the formulation containing the active insecticiάal ingreάient άirectly onto the insects or to the habitat of the insect. Since cockroaches are nocturnal, direct application will not be practical or effective unless the user is present when the cockroaches are present. Though many insecticide products claim resiάual control, those claims are based on long periods of forced exposure of the insects to the surface, i.e., 24 hours of continuous exposure is common in the art. This extended exposure time is required to kill the roaches, because the insecticide must be absorbed by the roach from the surface where the active has been applied. With the formulation of the present invention long exposure time is not necessary, because the crystals sit on the surface, are readily accessible to the insect and can be easily picked up within a few minutes.

Conventional aerosol insecticides, either water or oil based, contain solvents in which the insecticide is dissolved. Typically, the solvent is based on mixtures of normal paraffins. These paraffins not only dissolve the insecticide, they also facilitate wetting the insect when it is sprayed άirectly with the product. This allows for faster transfer and uptake of the insecticide by the insect, and provides what is known in the art as "knockdown." However, due to EPA regulations formulators use paraffins that are long chain hydrocarbons (typically C-14 and longer), so they are not considered by the EPA to be volatile organic compounds (VOC's). Hence, the insecticide is dissolved in a solvent having low volatility. When such a product is dispensed on a porous surface, the solvent seeps into the surface carrying the insecticide with it. This drastically diminishes the residual performance of the product because it is no longer available on the surface for the insect.

Secondary kill is not possible for conventional aerosol insecticides because an insect cannot pick up a sufficient quantity of insecticide to kill other insects that have not been exposed to the treated surface. On non-porous surfaces like tile, conventional aerosol insecticide proάucts that are soliά at room temperature, e.g. Baygon or Dursban (O,O-άiethyl O-3,5,6-triehloro-2-pyriάinyl phosphorothioate) will form crystals on the surface. However, because the insecticiάe evaporates so slowly (over hours or days) the subsequent crystals are very large (on the order of millimeters) which do not exhibit seconάary kill. With the volatile solvents used in the present formulation (combinations of one or more of the following: propane, heptane, octane short chain alcohols ( -Cs), and dymel (1,1 difluoroethane) (152a)) the solvent evaporates within seconds, which not only keeps the insecticide from aάsorbing on the surface but also causes small crystals to form (on the orάer of 30 microns). Excellent seconάary kill is exhibited by this novel insecticidal formulation.

Conventional insecticides often exhibit what is known in the art as repellence. This is the behavior of the insects to avoid treated surfaces. Often this repellence has been observed to come from an irritating but non-lethal contact between the roach and the surface. After that the roach will not return to the surface. It is therefore necessary that the roach pick-up the insecticide on its first contact. Because the insecticide in this formulation is easily picked up by the roaches, the roach will die in its first contact. One method known to the art for keeping insecticides on the surface so that it is accessible for pick-up by the roaches is microencapsulation. This is a process in which small spheres of insecticide are formed in which the insecticiάe is trapped within a polymer coating. This system is unstable in systems containing oil because the insecticide can diffuse through the membrane if there is a driving force for diffusion. If the microcapsule contacts a lipophobe in which the insecticide is soluble it will diffuse out from the microcapsule. Because aerosols contain either hydrophobe solvents or propellants, it is extremely difficult to formulate a product that will exhibit even short-term stability. One way of doing this is to make an emulsion, which isolates the microcapsules from the hydrophobe phases. However, the method for preparing such emulsions is άifficult and if there is a mistake in manufacturing, the microcapsules may end up in the oil phase, releasing the insecticide. If this insecticide is irritating or toxic at a sufficient dosage or rate this instability of the microcapsule may pose a consumer health risk.

The micro crystal formulation of the instant invention delivers the benefits of microencapsulation without the challenges and risks associated with such a formulation. Additionally, it uses a high level of propellant (>80%) which is not known to the art how to formulate using microcapsules. This high level of propellant allows the formation of very small aerosol particles (<30 microns) which can diffuse into harά to reach places where roaches hiάe. Again, this is advantageous because the roaches are not active during the daylight hours and the products' ability to diffuse back to where the roaches harboarage is extremely advantageous for the consumer. The present formulation also delivers the consumer desirable benefits of no mess (no solvent) and no odor (no solvent).

Detailed Description of the Invention:

The present invention employs a unique system of solvent and propellant which enhances the delivery and effectiveness of the active ingredient. A propellant or propellant/solvent mixture and insecticide(s) combination is selected, such that the insecticide(s) is soluble in the propellant or propellant/solvent mixture, anά the insecticide will be a solid phase once the propellant or propellant/solvent has flashed off, or the insecticide is present in a viscous suspension of powdered insecticide in a formulation in which it is not soluble. Typical pesticides useful in this invention include:

This formulation may incluάe a corrosion inhibitor common to the art e.g. soάium benzoate, nitromethane, thioacetamiάe, 2-mercaptobenzimiάazole, etc.

Surfactant systems common to the art coulά be used to form this water in oil emulsion, such as nonyl phenol ethoxylates, alkylbenzene sulfanates, sulfosuccinates, linear alkyl ethoxylates, polyethylene glycol esters, and the like.

Propellants useful in this invention are fluorinated propellants like άymel 152a such as a low boiling liquified gases such as butane, propane, dimethylether (DME) or blends thereof.

In the U.S. the use of volitile organic compounds (NOC) limit formulators to using less then 20% NOC materials. Hence, it would be possible to blend in less then 20% pentane, DME, or the like, with the dymel (152a). Internationally, any propellant that will dissolve the insecticide could be used, such as butane, propane, pentane, and the like. When nitrogen, CO2 or other compressed inert gasses are used— however this would require that the solvent for the insecticide be very volitile e.g. acetone, so that it would flash off within seconds and leave the crystalline active as described above.

The insecticide(s), solvent(s) are added to the empty aerosol container, it is then crimped anά the propellant(s) are aάded. Typical formulations will contain >95% propellant/volatile solvent and the remainder insecticide. When this product is sprayed all of the propellant/volatile solvent flashes off, leaving a residue of the solid phase insecticide behind.

A preferred formulation that has been found to be particularly effective is 0.1-0.01% deltamethrin dissolveά in a blend of 1-10% n-octane and the bulk dymel 152a, (1,1 άifluoroethane).

The above formulation will άeliver the άesireά secondary kill and demonstrates easy pick up from the surface by the target insect. However, other materials may be adάeά to proviάe additional benefits. Such adάitions consiάereά are as follows:

Adjuvant such as silicone oils, e.g. dimethylsiloxane polymers; polymeric materials, surfactants, sugars, paraffins, etc. to increase pick up by the insect or to άecrease the aάhesion between the insecticide particles and the surface or slow the release of the insecticide;

Attractants such as fenugreek to bring insects into contact with the surface and/or increase the amount of contact time between insect anά the surface.

Insect growth regulators may also be aάάed;

Other insecticides can be addeά at low enough levels not to solvate the solid form insecticide, such as S-biolallethrin, prallethrin, tetramethrine, and the like , to speeά up the knock-άown of the formulation. For example άeltamethrin is 15% soluble in S-biolallethrin, hence if άeltamethrin is used at 0.03% the rate of S- biolallethrin must be less than 0.2% for the crystals to form, assuming there are no other low vapor pressure solvents in the formulation;

Solvents may also be addeά to άeliver knock-άown insecticide(s) more rapidly to the insect, further speeding up the knock-down. However these solvents must be volatile enough that the solvent will evaporate before having time to absorb into porous surfaces.

Fragrances, pigments, or other additives may also be employed depenάing on the particular use. These are well known in the art; and.

Trace amounts of anti-irritants may be added, such as esterol, to decrease the product irritance.

In accordance with this invention, the crystal size is important. In the development of this product solvents of άifferent volatility were added to the formula and scanning electron (SEM) micrographs were taken of the resulting forms of the insecticide -deltamethrin. It was found that crystal size was inversely proportionate to the volatility of the solvent. The secondary kill efficacy was depenάent on the form of the deltamethrin. When the crystals were small (1-50 microns) there was good seconάary kill. However, with the less volatile solvents (e.g. peanut oil) huge crystals (> 100 microns) were formed with little or no secondary kill. Other solvents, like cyclohexanone, formed a sheet-like structure that had virtually no secondary kill.

One formulation to exhibiting particularly good performance is 0.04% deltamethrin, 0.01-0.3% S-biolallethrin, 0.5% octane, and bulk dymel 152A(1,1 difluoroethane).

Example 1

Insecticide formulations were tested for their ability to be picked up from a treated surface by cockroaches (primary) and be transferred to other cockroaches (seconάary), resulting in the death of both the primary and seconάary roaches.

Sample preparation: 6"x6" unfϊnisheά pine tiles were sprayed at a distance of 12" with άifferent aerosol formulations for approximately 3 seconds. The aerosol was moved back and forth to insure that the entire tile has an even coating of the product. Each sample was labeled with its insecticide formulation treatment. Controls were similar in treated tiles.

The samples are allowed to sit overnight before being used.

Test Procedure: 1.) For each replicate/treatment 15 adult male german cockroaches (hmr Blatella germanica) are placed inside a 16 oz wide mouth glass jar with the sides greased with a mixture of white petrolatum and mineral oil (50:50).

2.) For each replicate/treatment 5 adult male german cockroaches (hmr Blatella germanica) are placed inside a plastic pint sized container with the sides greased with a mixture of white petrolatum and mineral oil (50:50).

3.) The pint container instep 2 in inverted and placed on top of the test surface, insuring that all roaches are on the surface for 5 minutes.

4.) Controls were used composed of jars with roaches exposed to untreated surfaces. 5.) After the 5 minutes the roaches are transferred in the glass jars of step 1 , where they are in contact with the 15 uncontaminated roaches.

6.) The jars are left undisturbed for 24 hours, at which point the number of dead and live roaches are counted. 7.) The secondary kill is measured by taking the total number of roaches (20) and subtracting the roaches exposed to the surface (5) from the number of dead roaches and diviάing this number by the number of roaches exposed to the surface, and multiplying by

100.

The results are reported as percent secondary kill

TABLE I

deltamethrin

Claims

What is Claimed is:

1.) An insecticidal composition comprising deltamethrin, a solvent and a low boiling propellant.

2.) The composition of Claim 1 containing from about 0.01% to about 0.1% of deltamethrin, from about 1% to about 10% solvent and from about 98.99% to about 89.9% of propellant.

3.) An insecticidal composition comprising deltamethrin having a crystalline particle size of < 50 microns.

4.) The insecticiάal composition of Claim 4 wherein the crystalline particle size is < 30 microns.