IMPROVED INSECTICIDAL TEXTILE MATERIAL

Field of the Invention

[0001] The field of the invention relates to a textile material such as a fabric, knit goods, netting material, bednet, foil, curtain, tarpaulin or to a wall material that has been impregnated or coated with at least one microencapsulated insecticide to impart wash fastness or residual effect to the insecticide and to maintain bioavailability of the insecticide, methods of producing the material and compositions for treating the material.

Background

[0002] Many infectious diseases (e.g. malaria, dengue and yellow fever, lymphatic fϊlariasis, and leishmaniasis) that are responsible for debilitating or even killing humans and animals in many countries, especially in tropical countries, are transmitted by insects. For example, the mosquito parasite, Plasmodium falciparum, accounts for greater than 25% of childhood mortality outside the neonatal period. In certain parts of Africa, malaria has been ranked first by the World Bank in terms of disability-adjusted life-years lost. Insufficiently developed and financed health services as well as drug resistance have hampered many medical efforts to improve the situation. More recently, efforts have been concentrated on controlling the transmitting insects.

[0003] Methods to control these insects comprise treating surfaces of huts and houses, air spraying and impregnation of curtains and bednets. Insecticide-treated nets and fabrics have been developed since the 1980s as a promising tool for the prevention of malaria in endemic countries. Potent and safe synthetic pyrethroids, such as, permethrin, deltamethrin, lambda-cyhalothrin, alphamethrin, and cyfluthrin, are presently used to treat bednets and curtains by dipping the textile material into emulsions or dispersions of insecticides or spraying them onto the nets.

[0004] The use of pyrethroid insecticides for "impregnation" of mosquito nets and curtains as a means of killing mosquitoes and other flies that settle on the treated materials is well known. This concept is based upon the way that blood-sucking arthropods may contact the insecticide-treated substrate when attracted to a nearby host, eg. a person sleeping under a bednet. This promotes the control of the pests, eg. mosquitoes.

[0005] Because people tend to wash their bednets, curtains, etc. from time to time, it is desirable to enhance the persistence of insecticides on treated materials by making them wash-proof, to some extent. Studies have proven long-lasting insecticide-treated nets (LLITNs) to be more reliable in preventing carrier-borne diseases in comparison with conventional nets, which have to be re-treated or re-impregnated with insecticide after only one or two washings. However

conventional insecticidal compositions do not provide sufficient wash fastness and the present invention is concerned with a solution to this problem.

Summary of the Invention [0006] The present invention provides a microencapsulated insecticide-treated fabric and a method for treating, coating or impregnating the fabric with a composition comprising a microencapsulated insecticide and a polymeric binder. The treated fabric maintains a sufficient amount of microencapsulated insecticide on the fabric surface to kill or repel insects, particularly mosquitoes, even after repeated washings. The fabric can be made into a net, clothing, and the like, for protection against insect-transmitted diseases such as malaria. A microencapsulated insecticide treatment composition containing a polymeric binder for treating fabrics and a field kit comprising a first sachet containing at least one polymeric binder and a second sachet comprising at least one microencapsulated insecticide are also provided.

Description of Specific Embodiments

[0007] While the present invention is susceptible to several embodiments in various forms, there is hereinbelow described in detail certain specific embodiments, with the understanding that the present disclosure is to be considered as merely an exemplification of the present invention, without limitation to the specific embodiments or examples discussed.

[0008] Accordingly, the invention provides an insecticide treatment composition containing at least one polymeric binder and at least one microencapsulated insecticide. In one embodiment, the polymeric binder and the microencapsulated insecticide are provided together in separate sachets and are combined together with water to form an aqueous treatment composition by an end user. In another embodiment, the polymeric binder is an ethyl vinyl acetate copolymer. In one embodiment, the binder is substantially free from polyurethanes such as post-dispersed polyurethanes or water soluble polyurethanes. In a further embodiment, the insecticide is a pyrethroid such as lambda cyhalothrin. In another embodiment, the insecticide is an organophosphate such as pirimiphos-methyl. The microencapsulated insecticide and the polymeric binder bond or interact together to form a coating on the fabric which, in one embodiment, is a partial or discontinuous coating. The fabric is impregnated or partially (discontinuously) coated by immersing the fabric in a treatment composition such as an aqueous composition comprising a dispersion of at least one microencapsulated insecticide and at least one polymeric binder and allowing the wetted fabric to dry with no requirement for high temperature curing. The polymeric binder binds or adheres to the fabric and allows the microencapsulated insecticide to remain attached to the fabric, even after several washes with a detergent and rinses, thereby prolonging the insecticidal effectiveness of the fabric.

[0009] Treatment of fabric with the microencapsulated insecticide treatment composition described herein reduces the rate at which the insecticide is removed from the treated net during washings. Fabrics treated with the microencapsulated insecticide and binder composition of the present invention provide longer lasting insect knockdown and mortality effects than fabrics treated using compositions that lack the combination of a microencapsulated insecticide and a polymeric binder. Wall materials treated with the inventive composition exhibit, among other things, higher residual insecticidal effects.

[0010] The method provided herein is a simple process that combines the use of polymeric binders and microencapsulated insecticides to attach insecticides to bed nets and other fabrics. Use of the method described herein results in a product that is superior over presently available bednets and provides a more durable and effective insecticide activity or effect at the surface of the net or fabric. The use of the treated nets and fabrics provided herein results in more effective nuisance and/or vector arthropod control, which is associated with a reduction in disease transmission.

[0011] The insecticide-treated or impregnated fabric can be used in the manufacture of various end-user items such as, but not limited to netting, clothing, bedding, curtains and tents. Alternatively, fabric and existing fabric products can be treated and retreated with the insecticide composition using the method described herein. The insecticide treatment composition of the invention (an aqueous composition comprising at least one microencapsulated insecticide and at least one binder) is also suitable for wall treatments and other residual spray applications. The fabric-impregnating ortreating method, using the insecticide composition, results irra product that is superior in performance, simpler to use, and lower in cost than currently available insecticide-impregnating, treating or coating methods over the lifetime of a particular treated net. Furthermore, the materials used in the method are less hazardous to apply and more environmentally acceptable than some of those currently available. This is particularly due to the active ingredient being microencapsulated and presented in an aqueous-based formulation. This can be particularly important when pesticide compositions such as insecticides are being handled by humans where contact with exposed skin may result in temporary itching, tingling, burning or numbness, called paresthesia. Paresthesia involving the face is also known as "subjective facial sensation" or SFS.

[0012] Accordingly, the present invention provides a method of treating fabrics to impart wash resistant insecticidal properties thereto which comprises treating said fabric with an insecticidally effective amount of a liquid composition comprising at least one microencapsulated insecticidal active ingredient and at least one polymeric binder. In one embodiment, an aqueous treatment composition is employed. The threads of the treated fabric are thus coated or partially coated not

only with the microencapsulated insecticidal active ingredient but also with the polymeric binder. In one embodiment, the partial coating is a discontinuous coating of at least one surface of the substrate such as fabric. Those skilled in the art will appreciate that, although the coating is discontinuous at a, for example, micron level, the average loading of binder and insecticide per square meter of the substrate can be substantially the same or within a statistically acceptable target across the entire treated substrate. The effect of the polymeric binder is to increase the adhesion of the microencapsulated insecticidal substance to the fabric by effectively "sticking" the insecticide-containing microcapsules on to the individual threads of the fabric, in such a manner as to provide wash fastness while maintaining bioavailability of the insecticide. Although not wishing to be bound by theory, it is believed that the interaction between the polymer wall of the microcapsule, the polymeric binder and the fabric increases the wash fastness of the treated fabric.

[0013] The invention thus provides woven or non-woven fabric material the threads of which are coated or partially coated with a film of an adherent polymeric binder incorporating a microencapsulated insecticidally active substance. In one embodiment, the invention provides woven or non- woven fabric material the threads of which are discontinuously coated or partially coated with a polymeric binder and a microencapsulated insecticidally active substance. The fabric may be in the form of furnishing fabrics, such as curtains, bed-linen, bed-nets, furniture covers, or may be incorporated into matting, carpets or other floor or wall covering.

Alternatively the fabrics may be made up for use in packaging, such as sacks for the storage and transport of materials, including foodstuffs subject to spoilage by insect pests. In addition, floor materials such as carpet or wall materials such as a wall board treated with the material are provided with increased residual control of insects by application of such composition comprising at least one polymeric binder and at least one microencapsulated insecticide.

[0014] In this regard, in another embodiment, the present invention provides a method of combating insect pests in a dwelling which comprises applying an insecticidally effective amount of a liquid composition comprising at least one microencapsulated insecticidal active ingredient and at least one polymeric binder to a wall or floor surface of such dwelling.

[0015] Fabrics or netting to be treated may be made of natural fibres such as cotton, raffia, jute, flax, sisal, hessian, or wool, or synthetic fibres such as polyamide, polyester, polypropylene, polyacrylonitrile or the like. The polyesters are particularly suitable.

[0016] The impregnated, treated, coated or partially or discontinuously coated netting or fabric according to the present invention may comprise the active ingredient in an amount from about 0. 001 % w/w to 95 %, w/w by weight, of the insecticide. In general, the pyrethroid insecticides

such as lambda cyhalothrin are used in an amount of 0. 025% w/w to 0.33% w/w (weight of insecticide/weight of fabric). In another embodiment, the insecticide active ingredient is applied to the target fabric in an amount of from 10 to 100 mg a.i./m ² (approximate netting weight of 30- 40g/m ² ).

[0017] The method of the invention may be practised using liquid compositions comprising any suitable microencapsulated insecticide which is effective against the pests to be controlled, particularly adult mosquitoes and flies.

[0018] Particularly suitable polymeric binder materials for use in the invention are the Atlox ^™ SemKote range of polymers available from Uniqema such as the ethyl vinyl acetate copolymers (E-100, E-105, E-115, etc.), the polyvinyl acetate homopolymers (P-140, P145); as well as the acrylic and vinyl acrylic materials. Specific features of suitable polymeric binders used are that (1) it is compatible with the microencapsulated insecticide composition employed (in particular the polyurea walled capsules), (2) it is sufficiently miscible with water to enable standard aqueous-based application methods (By way of example, binders with suitable miscibility are those which are miscible with water in an amount of at least 10% by weight; more particularly, at least about 30% by weight), (3) it has a glass transition temperature that allows simple air drying without the need for a heat curing process (typically 0-15 ⁰ C) and (4) it is capable of being employed in an amount sufficient to impart suitable adhesion properties of the microencapsulated to the substrate to provide the desired wash fastness of the treated fabric, while maintaining bioavailability of the insecticide.

[0019] Optimum rates of application of the a particular binder as specified above, for a particular microencapsulated insecticide, a particular target substrates and set of insect pressure conditions, can be determined easily and without undue experimentation by simple ranging studies carried out in target substrates or fabrics such as polyester bed nets. Use of such optimum rates in treating a target substrate such as a fabric or wall generally resulted in a partial or discontinuous binder coating, while at the same time achieving a target loading of the active ingredient per square meter of substrate. Overloading of the binder to achieve a continuous coating or film of the binder can result in fabric stiffness and loss of bioavailability of the insecticide.

[0020] For example, it has been found that a target loading of 25 - 950mg of actual solid polymer binder per square meter of fabric provides this important balance of wash fastness to bioavailability while preserving serviceability of the fabric such as a net. More particularly, a target loading of 25 - 600mg of actual solid polymer binder per square meter of fabric; more specifically from 100 to 400mg; or from 125 to 350mg is employed. A binder loading of 100 to

400 nig per square meter, more particularly about 350 mg, is particularly suitable for the polyesters.

[0021] If it is desirable, the polymeric binders described herein can be compounded with, or have mixed therein, other known ingredients such as plasticizers, emulsifiers, surface active agents, stabilizers (including UV light protectants), fillers, antioxidants, fungicides, antimicrobials, antifoaming agents, drying adjuvants, levelling agents, pigments, or other compounding aids. Furthermore, thickeners or bodying agents may be added to the polymer binder so as to control the viscosity of the binder and thereby achieve the proper flow properties for the particular application desired. Such materials are well known in the art.

[0022] Microencapsulated insecticide active ingredients suitable for use in the treatment compositions and coated fabrics according to the invention are prepared with any suitable technique known in the art. For example, various processes for microencapsulating material have been previously developed. These processes can be divided into three categories-physical methods, phase separation and interfacial reaction. In the physical methods category, microcapsule wall material and core particles are physically brought together and the wall material flows around the core particle to form the microcapsule. In the phase separation category, microcapsules are formed by emulsifying or dispersing the core material in an immiscible continuous phase in which the wall material is dissolved and caused to physically separate from the continuous phase, such as by coacervation, and deposit around the core particles. In the interfacial reaction category, microcapsules are formed by emulsifying or dispersing the core material in an immiscible continuous phase and then an interfacial polymerization reaction is caused to take place at the surface of the core particles. The concentration of the insecticidal active ingredient present in the microcapsules can vary from 0.1 to 60% by weight of the microcapsule. In general, suitable microencapsulated insecticides are particles with diameters between 0.1 and 1000 μm.

[0023] In one aspect, suitable microcapsule wall materials are selected from the polyureas, aminoplasts, polyurethanes and polyamides.

[0024] In one embodiment, polyurea microcapsules containing a suitable insecticide are prepared as exemplified in U.S. Pat. No. 4,285,720, which involves the use of at least one polyisocyanate such as polymethylene polyphenylisocyanate (PMPPI) and/or tolylene diisocyanate (TDI) as the prepolymer. In the creation of polyurea microcapsules, the wall- forming reaction is initiated by heating the emulsion to an elevated temperature at which point the isocyanate polymers are hydrolyzed at the interface to form amines, which in turn react with unhydrolyzed polymers to form the polyurea microcapsule wall.

[0025] The present invention relates to but are not limited to the following active insecticides for use in the treatment compositions and fabrics include those selected from the group comprising pyrethrins and synthetic pyrethroids; azoles, bisamides, oxadizine derivatives; chloronicotinyls; nitroguanidine derivatives; triazoles; organophosphates; pyrrols; pyrazoles; phenyl pyrazoles; diacylhydrazines; biological/fermentation products such as macrolides including emamectin or abamectin; plant essential oils such as d-limonene and eugenol; carbamates and combinations of these types of compounds.

[0026] Thus specific microencapsulated insecticides include carbamate such as propoxur or bendiocarb, or an organophosphorus insecticide such as malathion, pirimiphos-methyl or fenitrothion, or a pyrethrin or pyrethroid insecticide such as allethrin, bioallethrin, S-bioallethrin, neopynamin, fenvalerate, permethrin, cypermethrin, alphamethrin, deltamethrin, cyhalothrin or lambda-cyhalothiin. Mixtures of insecticides may be employed for enhanced effect and for resistance management reasons. In one embodiment, a mixture of a microencapsulated insecticide with a non-microencapsulated insecticide may be used. One specific example is a mixture of microencapsulated lambda cyhalothrin with non-microencapsulated deltamethrin.

[0027] In one aspect, suitable microencapsulated insecticides for use in the inventive treatment compositions and treated fabrics include tefluthrin, permethrin, lambda cyhalothrin, resmethrin, deltamethrin, cypermethrin, cyphenothrin, cyfluthrin, deltamethrin, chlorpyrifos, fenoxycarb, diazinon, dichlorophen, methyl isothiocyanate, pentachlorophenol, tralomethrin, chlorfenapyr, fipronil, neonicotmoids and combinations of these compounds. Examples of suitable neonicotinoids include, but are not limited to, thiamethoxam, nitenpyram, imidacloprid, clothianidin, acetamiprid, and thiacloprid. One specific class of pesticides for use in the microcapsules are the class of cyhalothrins including lambda cyhalothrin and gamma cyhalothrin. The microencapsulated insecticides are employed at rates dependent on their activity levels for the desired end use. In one embodiment, suitable rates for the insecticide are the existing rates given on the current product labels for pesticide products containing such insecticides. For example, ICON ^® CS brands of microencapsulated lambda cyhalothrin available from Syngenta have been found to be suitable.

[0028] In one aspect, target pests include including insects belonging to the order Diptera (covering mosquitoes, gnats, black flies, tsetse flies and other biting flies), Hemiptera (covering bed bugs) and Siphonaptera (covering fleas). Among target pests there may also be mentioned, Dictyoptera (covering cockroaches), Coleoptera (covering pests of stored grain) Lepidoptera (covering moths) and Arachnids (covering mites and ticks). The present invention is particularly suited for controlling flying pests such as mosquitoes.

[0029] The treatment compositions used in the invention may also contain wetting emulsifying or dispersing agents, which may be of the cationic, anionic or non-ionic type. Suitable agents of the cationic type include, for example, quaternary ammonium compounds, for example, cetyltrimethyl ammonium bromide. Suitable agents of the anionic type include, for example, soaps, salts of aliphatic monoesters or sulphuric acid, for example, sodium lauryl sulphate, salts of sulphonated aromatic compounds, for example, sodium dodecylbenzene-sulphonate, sodium, calcium or ammonium lignosulphonate, or butylnaphthalene sulphonate, and a mixture of the sodium salts of diisopropyl- and triisopropylnaphthalene sulphonates. Suitable agents of the non- ionic type include, for example, the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol or cetyl alcohol, or with alkyl phenols such as octyl phenol, nonyl phenol and octyl cresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, the condensation products of the said partial esters with ethylene oxide, and the lecithins.

[0030] In one embodiment, the fabric treatment compositions which are to be used in the form of aqueous dispersions or emulsions are generally supplied in the form of a concentrate containing a high proportion of the active ingredient or ingredients, the said concentrate to be diluted with water before use (There may be mentioned capsule suspensions, for example). These concentrates are often required to withstand storage for prolonged periods and after such storage, to be capable of dilution with water to form aqueous preparations which remain homogenous for a sufficient time to enable them to be applied by dipping or by conventional spray equipment.

[0031] In another embodiment, a separate sachet of the polymeric binder is provided along with a separate package or sachet containing the microencapsulated insecticidal composition (such as Icon 10 CS, Icon 2.5 CS or the like). These materials are then combined with water in a treatment container or tank to form a final treatment composition.

[0032] Accordingly, the invention further provides a field kit for treating or retreating a fabric material to impart wash resistant insecticidal properties thereto which comprises a first sachet containing a premeasured amount of at least one polymeric binder, and a second sachet containing a premeasured amount of an insecticidal composition comprising at least one microencapsulated insecticide. As noted above, these materials are then diluted by combining with water in a treatment container or tank to form a final treatment composition. Fabrics are treated with the treatment composition to impart wash resistant insecticidal properties thereto by spraying, dipping or soaking the fabric in the treatment composition.

[0033] In one embodiment, the final treatment compositions may contain from 1 to 70% by weight of the insecticidal active ingredient in microencapsulated form, and more specifically from 5 to 50% by weight. They may also contain from 1 to 70% by weight of the polymeric binder, and more specifically from 1 to 25% by weight.

[0034] Where the composition is diluted with water before use it may be applied to the fabric by direct spraying, or by dipping or soaking the fabric in a bath containing the diluted composition. The fabric may be finished and made up fabric, such as curtains (particularly net curtains), bed- linen, furniture covers or the like, or may be new fabric. In the latter case the microencapsulated insecticide treatment may be carried out at the end of the manufacturing process, by placing the microencapsulated insecticidal composition in the final treatment bath.

[0035] The leaching of insecticides from fabrics during the washing process not only reduces the insecticidal effectiveness of the deposit on the fabric, but also allows the insecticides to pass into the wash water. By the use of the methods and compositions of the present invention

(microencapsulated insecticide plus a polymeric binder) the wash-fastness of the insecticide on treated fabric may be significantly improved as shown by the residual knock-down and mortality effects on target insects that come into contact with the treated fabric.

[0036] The invention is illustrated by the following Examples. The examples illustrating compositions of particular active ingredients may be considered as exemplifying also compositions in which the active ingredient is replaced by others of similar effectiveness.

[0037] EXAMPLES EXAMPLE 1 -

[0038] A treated polyester net is prepared in the-following way:

[0039] A 60x60 swatch of a polyester net material was treated in the laboratory using a 1 litre treatment solution volume. The composition of the 1 litre treatment solution was as follows:

16.2g Icon IOCS* 30.Og Atlox SemKote E-105** (55% solid binder)

953 g De-ionised water

[0040] The solution is prepared in a plastic bottle, the swatch of netting is carefully folded and rolled and placed into the solution and the cap of the bottle secured. The bottle is then rolled for 5 minutes, after which time the net is carefully removed. Excess liquid is removed using absorbent paper and the net is then hung up to dry for 24 hours under ambient conditions.

[0041] Target loading is 50 mg a.i./square meter (i.e. 0.5g Icon IOCS , as 10% formulation) 350 mg solid polymer (i.e. 0.63g Semkote E105, as 55% solution)

* The target loading of lambda-cyhalothrin is 50mg a.i. per square meter of net, but due to losses incurred in the lab application process the solution is "overloaded" with Icon.

** Binder retention studies have shown that this level of binder in the solution for this method of application results in a retention of only around 0.35% solid binder per square meter.

EXAMPLE 2 - Nets prepared in accordance with procedures of example 1 are used in the following procedure except that the "Iconet" nets lack the binder. Washing and bioassay cycles were undertaken following similar protocols to that published in the document

WHO/CDS/WHOPES/GCDPP/2005.11. Percent knockdown and mortality of Aedes aegypti following 3 minute exposure to experimental net formulation containing Icon CS and polymer binder are shown below:

TABLE l

EXAMPLE 3 -

[0042] Treated polyester net is prepared in the-following way:

[0043] Whole polyester mosquito nets (75 denier, 130xl80xl50cm) were treated with Icon 2.5CS (25g/L lambda-cyhalothrin) and polymer binder via a hand dipping process as set out below.

[0044] The required amount of insecticide (target dose 50mg ai/m2) and binder was weighed out and pre-mixed. The mixture was then added to 500ml de-ionised water, ensuring that all of the formulation and binder was in solution. One whole mosquito net was then added to the solution and turned. After approximately 3 minutes turning, the net was removed without wringing and laid flat on the floor of the laboratory. Following a drying period of 12-16 hours, the nets were folded and stored in aluminium foil.

EXAMPLE 4 -

[0045] Efficacy of nets prepared following the procedures of Example 3 were assessed using similar methods to those recommended in "Guidelines for laboratory and field testing of long lasting insecticide treated mosquito nets" (W.H.O./CDS/W.H.O.PES/GCDPP/2005.11.), except that the "Icon CS only" nets lack a binder and the insecticide in KO-Tab is not microencapsulated.

Table 2. Percent knockdown of Aedes aegypti after 3 minutes exposure to netting treated with Icon CS (50mgs ai /m2) and Semkote El 05

Assessment after 60 minutes

K KOO TTaabb 112233: 25mgs ai/m ² deltamethrin + binder, net treated following manufacturers instructions.

Table 3. Percent mortality of Aedes aegypti after 3 minutes exposure to netting treated with Icon CS (50mgs ai /m ² ) and Semkote E 105

• Assessment after 24 hours

EXAMPLE 5 - [0046] Following known procedures, microencapsulated pirimiphos methyl can be prepared by dissolving the insecticide in a suitable solvent, forming and aqueous based emulsion of the desired droplet size, using appropriate emulsifϊcation and dispersion aids and including suitable monomers in the oil and /or aqueous phased, and performing an interfacial polymerisation at the emulsion interface. This results in a mobile solution of active ingredient being encapsulated within polymer shelled microcapsules suspended in an aqueous-base continuous phase.

[0047] Nets are prepared following the procedures of example 3, except that 20 ml of a pirimiphos methyl 300g/l CS formulation, with 2Og Semkote E 105 in 500ml treatment water. This provides a net having 517mg a.i. and 948mg solid binder per square meter net.

[0048] The foregoing description and examples are for the purpose of illustration only and does not limit the scope of protection which should be accorded this invention.