WO2010084301A1

WO2010084301A1 - Insecticidal composition in the form of an aerosol water-in-oil emulsion

Info

Publication number: WO2010084301A1
Application number: PCT/GB2010/000029
Authority: WO
Inventors: Daniel Sheehy; Mario Abela
Original assignee: Reckitt and Colman Overseas Ltd
Current assignee: Reckitt and Colman Overseas Ltd
Priority date: 2009-01-20
Filing date: 2010-01-08
Publication date: 2010-07-29
Anticipated expiration: 2011-07-20
Also published as: GB0900874D0

Abstract

An insecticidal composition in the form of an aerosol water-in-oil emulsion comprising: (a) an effective amount of an aqueous suspension of at least one insecticide, said insecticide being in particulate form or adsorbed onto inert particles; (b) at least one water soluble or water dispersible thickener in an amount of from 0.01-5% w/w; (c) at least one solvent in an amount of from 1 to 20% w/w; (d) at least one emulsifier in an amount of from 0.2 to 10% w/w and selected from the group comprising mono, di- and tri-sorbitan esters, polyoxyethylene sorbitan esters, mono- and poly-glycerol esters; (e) from 2 to 80% w/w of at least one propellant; (f) optionally from 0.001 to 5% w/w of one or more oil phase soluble insecticides; and (g) the balance being water.

Description

INSECTICIDAL COMPOSITION IN THE FORM OF AN AEROSOL WATER-IN-OIL EMULSION

This invention relates to insecticidal compositions for use in pressurised aerosol containers, in particular to aerosol compositions in the form of water-in-oil emulsions where the insecticidally active ingredients provide a sustained insecticidal effect. Background to the Invention

The advantage of sustained effect insecticidal compositions is well recognised in that an insecticidal effect is provided over a prolonged period of time. Such compositions may, for example, be used in and around buildings so as to prevent the entry of insects.

Microencapsulation of insecticides has been used to provide sustained release of actives thereby providing a sustained insecticidal effect. A variety of microencapsulation methods and compositions are known in the art as represented by the microencapsulated lambda-cyhalothrin (available from Zeneca as DEMAND CS®). This material is available as 2.5 and 10% w/v aqueous capsule suspensions. In use, it is diluted with water and dispensed using a suitable spray means.

Whilst such diluted formulations are useful for professional pest controllers, they are of limited use owing to the inconvenience of preparation, particularly in domestic or other situations where ready to use non-sustained release insecticidal formulations are currently available.

One form of insecticide composition that is widely used domestically are aerosol insecticides. Generally water based aerosol insecticide compositions are emulsions with the active insecticide(s) being incorporated in the continuous oil phase.

By contrast, incorporation of insecticides that are aqueous dispersions or suspensions into aerosol compositions can be problematic owing to the instability of the so-formed emulsions. This instability has been attributed to the fact that the insecticide is present in the dispersed aqueous phase rather than the oil phase as occurs with conventional water based aerosol insecticides.

Pressurised aerosol formulations present particular difficulties because the liquefied propellant can act as an additional solvent, destroying the integrity of the insecticide particles. WO97/13409 discloses an aerosol water-in-oil composition comprising an aqueous suspension of microencapsulated insecticide and specified emulsifiers for stabilising the composition.

Given the potential utility of sustained effect insecticides in aerosol form, the present inventors have directed considerable efforts towards providing an alternate formulation which is both effective and stable and does not require microencapsulation of the insecticide to achieve sustained effect. Disclosure of the Invention

Surprisingly, the present inventors have found that it is possible to produce such aerosol formulations as water-in-oil emulsions by using insecticides in particulate form or adsorbed onto inert particles together with certain thickeners. Without wishing to be bound by theory, it is believed that the thickeners retain the insecticide particles in the water phase during preparation of the emulsion and prevents the particles migrating to the oil phase/propellant.

Accordingly, the present invention consists in an insecticidal composition in the form of an aerosol water-in-oil emulsion comprising:

(a) an effective amount of an aqueous suspension of at least one insecticide, said insecticide being in particulate form or adsorbed onto inert particles;

(b) at least one water soluble or water dispersible thickener in an amount of from 0.01-5% w/w;

(c) at least one solvent in an amount of from 1 to 20% w/w;

(d) at least one emulsifier in an amount of from 0.2 to 10% w/w and selected from the group comprising mono, di- and tri-sorbitan esters, polyoxyethylene sorbitan esters, mono- and poly-glycerol esters;

(e) from 2 to 80% w/w of at least one propellant;

(f) optionally from 0.001 to 5% w/w of at least one oil-phase-soluble insecticide; and (g) the balance being water.

Throughout this specification all percentages are w/w unless otherwise stated. Insecticide

Suitable insecticides have no or little water solubility and have some environmental residuality when applied to surfaces. Solubility in water is preferably less than 10 mg/L, more preferably less than 5 mg/L and most preferably less than 1 mg/L. Residual insecticides are those that do not break down quickly in air or sunlight such that when applied at an insecticidally effective rate, can continue to kill insects that come in contact with the residual deposit for a prolonged period such as days, weeks or even months after application, depending on the dose applied, the chemical activity or porosity of the surface treated and the rate of insecticide removal by various environmental factors. Suitable insecticides include: pyrethroid ester insecticides such as bifenthrin, cyfluthrin, beta-cyfluthrin, lambda-cyhalothrin, cypermethrin, alpha-cypermethrin, deltamethrin, esfenvalerate, permethrin and tralomethrin; oxadiazine insecticides such as indoxacarb; juvenile hormone mimics such as fenoxycarb, chitin synethsis inhibitors such as diflubenzuron, triflumuron or hexaflumuron, lufenuron etc. Pyrethroid ester insecticides are preferred with deltamethrin being the preferred pyrethroid. Combinations of two or more of the above insecticides may be included. The insecticide is present in an aqueous suspension in solid particulate form or in liquid form adsorbed onto a solid inert particles such as silica or diatomaceous earth.

Suitable particles sizes are from >2 to <500 microns, preferably from 3 to 250 microns, more preferably from 5 to 200 microns and most preferably from 5 to 30 microns. Particle sizes of 500 microns or more may pass through some aerosol valves; however, such particles are likely to leave undesirable visible deposits on surfaces and cause issues with sedimentation. The standard screens to filter particles from liquids before filling into aerosols have about a 200 micron size. Some of the insecticide ingredients listed above are not crystalline at room temperature but are in liquid form (e.g. permethrin) and others (e.g. cyfluthrin and cypermethrin) are waxy semi-solids. Such materials would need to be adsorbed onto solid carrier materials to deliver the residual benefit; however, even the crystalline active ingredients can be adsorbed onto particulate carriers if it is desired to have a particle size greater than that generated during the active ingredient synthesis process.

WO 97/37538 uses such a method whereby active ingredients are adsorbed onto particles Of TiO₂, AI₂O₃ , MgO or SiO₂ by dissolving the active in a volatile solvent (e.g acetone) and spraying or soaking the particulate matter with the solution, before evaporating off all the volatile solvent. The insecticide is incorporated in the compositions of the invention as an aqueous suspension so as to give an effective concentration of insecticide in the composition, preferably of from 0.001 to 5%w/w. A more preferred concentration range is from 0.001 to 2.5%w/w. Most preferred concentration is from 0.001 to 1% w/w.

Synthetic pyrethroids such as lambda cyhalothrin or deltamethrin will generally be incorporated in concentrations of about 0.03% w/w or more.

Other synthetic pyrethroids such as cypermethrin, permethrin will generally be incorporated to give a concentration of about 0.2% w/w or 0.4% w/w respectively or more. Thickener

Suitable water soluble or water dispersible thickeners are able to form a flowable liquid with a viscosity such as 100-800cps, preferably 100-400cps, to suspend the dispersed insecticide particles during the manufacturing process. Suitable thickeners include natural or modified natural thickening agents of vegetable origin (such as algin or methyl cellulose), natural or modified natural thickening agents of mineral origin (such as bentonite or hectorite) and natural or modified natural thickening agents of animal origin

(such as gelatine) and mixtures thereof. Synthetic thickeners such as acrylic acid esters may also be used.

The preferred thickeners would be derivatised cellulose thickeners such as methyl cellulose at a concentration of about 0.02 to 0.05% w/w.

Solvent

In order to maintain emulsion stability and, where required, to enable the incorporation of an optional oil phase soluble insecticide, at least one solvent is incorporated in the compositions of the invention in an amount of from 1 to 20% w/w . Generally, the solvent will be water immiscible.

A wide range of solvent materials may be used, although care should be exercised to ensure that the solvent does not adversely affect insecticidal activity.

Furthermore, it should be noted that combinations of solvents may be used.

Examples of solvents that may be used in the compositions of the invention include: liquid n-paraffins, liquid isoparaffins, cycloalkanes, naphthene- containing solvents, white spirit, kerosene, aromatic solvents, mineral turpentine, ester solvents, silicone solvents or oils, terpenes, fatty acids, linear alkylbenzene , dialkyl phthalates, C₅-Cn alcohols and fatty alcohols. Specific examples of these are as follows:

• liquid n-paraffins: Norpar 12, Norpar 13 and Norpar 15 (available from Exxon);

• liquid isoparaffins: lsopar G, lsopar H, lsopar L, lsopar M and lsopar V (available from Exxon);

• naphthene-containing solvents: Exxsol D40, Exxsol D60, Exxsol D80, Exxsol D100, Exxsol D110, Nappar 10 (available from Exxon); • ester solvents: alkyl acetates, examples being Exxate 1000, Exxate 1300 (available from Exxon), and Coasol (available from Chemoxy International);

• silicone solvents: oils such as Dow Corning 244, 245, 344 and 345 fluids;

• terpenes: eucalyptus oil, cineole, orange oil, limonene;

• fatty amines: soya amines, tallow amines, cocoamines; • fatty acids: caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid;

• fatty alcohols: octanol, dodecanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, cetostearyl alcohol, oleyl alcohol;

• aromatic solvents: benzene, xylene. Preferred solvents are liquid hydrocarbon solvents, n-paraffins and isoparaffins.

Although the solvent may be incorporated at a level of from 1 to 20% w/w, preferably the concentration will be in the range of 2 to 10% w/w, most preferably about 5% w/w . Propellants

One or more propellants are used in the composition of the invention in a total amount of from 2 to 80% w/w . Amongst the propellants that may be used are hydrocarbons, dimethylether and compressed gas of which hydrocarbons are preferred. In the case of the hydrocarbon propellants those that may be used are acetylene, methane, ethane, ethylene, propane, propene, n-butane, n-butene, isobutane, isobutene, pentane, pentene, isopentane and isopentene. Mixtures of these propellants may also be used. Indeed, it should be noted that commercially available propellants typically contain a number of hydrocarbon gases. For example, an odorised commercial butane, available from Boral gas contains predominantly n-butane and some iso-butane along with small amounts of propane, propene, pentane and butene.

Preferred hydrocarbon propellants include propane, n-butane, isobutane, pentane and isopentane, whilst most preferred are propane, iso- butane and n-butane.

Particularly preferred hydrocarbon propellants are mixtures of propane, n-butane and iso-butane.

Whilst broadly the concentration of hydrocarbon propellant will be from 2 to 80% w/w, generally the concentration will be from 10 to 60% w/w, preferably 25 to 60% w/w, most preferably about 40% w/w .

When compressed gases are used as a propellant generally these will be carbon dioxide, nitrogen or air. Usually they will be used at a concentration of 2 to 10% w/w, preferably about 5% w/w .

The person skilled in the art will appreciate that the pressure in an aerosol package will be determined by propellant or mixture of propellant. This pressure will have a determining effect on spray rates. Hence for any particular valve system, varying the propellant or propellant mixture will allow for the selection of a desired spray rate.

Likewise for a particular propellant or propellant mixture, it is possible to select a valve and actuator system to achieve a desired rate. Emulsifiers

One or more emulsifiers are included in the composition in an amount of from 0.2 to 10% and selected from the group comprising mono-, di- and tri- sorbitan esters, polyoxyethylene sorbitan esters, mono- and poly-glycerol esters are used in the compositions of the invention. Preferably the emulsifiers are selected from this group only.

It has been found advantageous to use two emulsifiers in the compositions of the invention. Generally, one of the emulsifiers will be a polyoxyethylene sorbitan ester whilst the second emulsifier will be chosen from either mono-, di- and tri-sorbitan esters or mono- and poly-glycerol esters.

Preferably, the emulsifiers will be esters with C10-C22 fatty acids. Particularly preferred are C1₂-C1₈ fatty acids.

Particular combinations of emulsifiers that have been found to be effective are sorbitan monooleate with 20 moles of ethylene oxide sorbitan monooleate; and, glycerol monooleate with 20 moles of ethylene oxide sorbitan monooleate. Whilst the total emulsifier concentration may be 0.2 to 10%, generally the concentration will be 0.5 to 8% preferably 1 to 5%, most preferably about 1 to 2%, particularly about 1.2%.

When two emulsifiers are used, usually the w/w ratio of the polyoxyethylene sorbitan ester to mono-, di- and tri-sorbitan esters or mono- and poly-glycerol esters will be from 0.5 to 3:9.5 to 7, preferably 0.5 to 1.5:9.5 to 8.5, most preferably 1.1 to 8.9. Optional Insecticides and Other Ingredients

A wide range of insecticides may be included in the oil phase as required. These include natural pyrethrum and synthetic pyrethroids.

In addition to the optional insecticides, synergists such as MGK-264 and piperonyl butoxide may be included for use in conjunction with pyrethroid insecticides.

The persons skilled in the art will also recognise that a perfume may be readily incorporated in the compositions of the invention to satisfy organoleptic requirements.

In addition, other ingredients such as corrosion inhibitors and preservatives may be used as required. Preparation The compositions of the invention may be prepared by dispersing the particulate insecticide into thickened water therefore suspending the particles. Solvent plus the emulsifier(s) including if required an optional insecticide, is separately prepared. The water phase is added to the solvent phase so as to produce an emulsified concentrate. The concentrate is filled into the aerosol container then gassed with the required level of liquefied propellant gas.

Brief Description of Drawings

Figure 1 shows %knockdown & mortality against weeks since treatment for surfaces treated in accordance with example 2 described below. Examples

In order to better understand the nature of this invention, a number of examples will now be described.

Ingredients and Availability

lmiprothrin 50% Pralle 50% MUP (Sumitomo Chemical)

Deltamethrin 98% Technical grade active constituent (Gulmohar Pty Ltd)

Bayothrin Transfluthrin Tech Grade (Bayer)

Bifenthrin Technical grade (United Phosphorus Limited - UPL)

Esbiothrin Technical grade ( Sumitomo)

Other Constituents

Deionised Water

C10-C13 n-Paraffin N-Paraffin (Sasol Wax)

Emulsogen 607 Polyglycerol Oleate (Clariant)

Cellulose QP Cellulose thickener 100,000 (IMCD)

Triethanolamine Triethanolamine (Redox Pty Ltd)

Laponite Laponite RD (Fernz Specialty Chemicals)

Xanthan Gum 200 Mesh Food Grade ( ADM)

BHT Butylated Hydroxy Toluene (Redox Pty Ltd)

Propellant H46 Propane/butane blend (Origin Energy LPG Ltd)

Each of the examples set out above was prepared according to the method previously described. Efficacy of example 2

In order to demonstrate the efficacy of compositions of the invention, porous terracotta tiles and non porous painted masonite were sprayed from a distance of 25 cm at the rate of 64g aerosol content/m² in line with consumer practice using a semi-automated system. The same type of surfaces were sprayed with an commercially available Propoxur/Cyfluthrin solvent based aerosol as comparison. Treated surfaces were stored horizontally in an outdoor location protected from direct sunlight and direct rainfall. At pre- determined intervals, treated surfaces were placed adjacent to untreated surfaces and ten American cockroaches (Periplaneta americana) were confined by a plastic container placed over the join between the treated and untreated surfaces. Cockroaches could therefore avoid the treated surface if they so chose. Knockdown was noted at various intervals up to and including 48 hours. The same methodology was used to evaluate the formulations performance against Black ants (Ochetellus sp.) and Brown Argentine ants (Linepithema humile) with the knockdown noted at various internals up to and including 24 hours. Results are shown in Figures 1-6.

The particulate aerosol formulation provided effective control up to at least 26 weeks (6 months) after application.

Claims

1. An insecticidal composition in the form of an aerosol water-in-oil emulsion comprising: (a) an effective amount of an aqueous suspension of at least one insecticide, said insecticide being in particulate form or adsorbed onto inert particles;

(b) at least one water soluble or water dispersible thickener in an amount of from 0.01-5% w/w; (c) at least one solvent in an amount of from 1 to 20% w/w;

(e) from 2 to 80% w/w of at least one propellant; (T) optionally from 0.001 to 5% w/w of one or more oil phase soluble insecticides; and (g) the balance being water.

2. An insecticidal composition according to claim 1 wherein the at least one insecticide has a solubility in water of less than 10 mg/L, preferably less than 5 mg/L and more preferably less than 1 mg/L.

3. An insecticidal composition according to claim 1 wherein the at least one insecticide is selected from the group consisting of pyrethroid ester insecticides, oxadiazine insecticides, juvenile hormone mimics, chitin synethsis inhibitors and mixtures thereof.

4. An insecticidal composition according to claim 3 wherein the at least one insecticide is selected from the group consisting of bifenthrin, cyfluthrin, beta- cyfluthrin, lambda-cyhalothrin, cypermethrin, alpha-cypermethrin, deltamethrin, esfenvalerate, permethrin, tralomethrin, indoxacarb, fenoxycarb, diflubenzuron, triflumuron, hexaflumuron, lufenuron and mixtures thereof.

5. An insecticidal composition according to claim 3 wherein the at least one insecticide is selected from pyrethroid ester insecticides bifenthrin, cyfluthrin, beta-cyfluthrin, lambda-cyhalothrin, cypermethrin, alpha-cypermethrin, deltamethrin, esfenvalerate, permethrin and tralomethrin.

6. An insecticidal composition according to claim 5 wherein the at least one insecticide is deltamethrin.

7. An insecticidal composition according to any one of claims 1 to 6 wherein the particle size is in the range of from >2 to <500 microns, preferably from 3 to 250 microns, more preferably from 5 to 200 microns and most preferably from 5 to 30 microns.

8. An insecticidal composition according to any one of claims 1 to 7 wherein the aqueous suspension contains an amount of insecticide sufficient to provide an effective concentration of insecticide in the composition of from 0.001 to 5%w/w, preferably from 0.001 to 2.5%w/w and more preferably from 0.001 to 1 %w/w.

9. An insecticidal composition according to any preceding claim wherein the at least one thickener is selected from the group consisting of: synthetic thickeners such as acrylic acid esters; natural or modified natural thickening agents of vegetable origin such as algin or methyl cellulose; natural or modified natural thickening agents of mineral origin such as bentonite or hectorite; natural or modified natural thickening agents of animal origin such as gelatine; and mixtures thereof.

10. An insecticidal composition according to claim 9 wherein the at least one thickener is a derivatised cellulose thickener.

11. An insecticidal composition according to claim 10 wherein the at least one thickener is methyl cellulose included in an amount of from 0.02 to 0.05% w/w.

12. An insecticidal composition according to any preceding claim wherein the at least one solvent is selected from the group consisting of liquid hydrocarbon solvents, n-paraffins, iso-paraffins and mixtures thereof.

13. An insecticidal composition according to claim 12 wherein the at least one solvent is selected from the group consisting of liquid n-paraffins, liquid isoparaffins, cycloalkanes, naphthene-containing solvents, white spirit, kerosene, aromatic solvents, mineral turpentine, ester solvents, silicone solvents or oils, turpenes, fatty acids, linear alkylbenzene , dialkyl phthalates, C5-C11 alcohols, fatty alcohols and mixtures thereof.

14. An insecticidal composition according to any preceding claim wherein the at least one solvent is included in an amount of from 1 to 20%w/w, preferably from 2 to 10%w/w, more preferably about 5%.

15. An insecticidal composition according to any preceding claim wherein the at least one emulsifier is included in an amount of from 0.5 to 8%w/w, preferably from 1 to 5%w/w, more preferably from 1 to 2%w/w such as about 1.2%w/w.

16. An insecticidal composition according to any preceding claim comprising a first emulsifier selected from polyoxyethylene sorbitan ester and a second emulsifier selected from either mono-, di- and tri-sorbitan esters or mono- and poly-glycerol esters.

17. An insecticidal composition according to claim 16 wherein the w/w ratio of the polyoxyethylene sorbitan ester to mono-, di- and tri-sorbitan esters or mono- and poly-glycerol esters is from 0.5 to 3:9.5 to 7, preferably 0.5 to 1.5:9.5 to 8.5, most preferably 1.1 to 8.9.

18. A method of killing insects that contact a surface, the method comprising applying to the surface an insecticidal composition as claimed in any one of claims 1 to 17.