Technical Field

The present invention relates generally to substrates for emanating vapour active substances such as aroma chemicals or vapour active insecticides. More particularly, the present invention relates to a multifilament polyester or polyamide substrate containing at least one vapour active substance such as, for example, a pyrethroid that is effective in controlling flying insects, particularly mosquitoes.

Background Art

The control of flying insects in an indoor or an outdoor area has traditionally been achieved using articles or devices that liberate insecticide vapours into the atmosphere. Such articles or devices generally burn or heat a liquid or solid substrate to vaporise the active ingredient. For instance, in controlling mosquitoes, coils impregnated with an active ingredient are burnt so that heat from the combustion causes the release of the active ingredient into the atmosphere, candles containing citronella oil are burnt so as to heat the citronella oil and allow it to vaporise into the atmosphere, while electric devices are heated using electricity so that the active ingredient vaporises and is dispersed into the atmosphere. Battery operated, fan driven products are also used to control mosquitoes. The above mentioned products require an energy source in the form of combustion, heat or electricity to release the active ingredient. The function of products such as mosquito coils, candles, liquid vaporisers, battery powered fans and electrically heated mats are essentially independent of the surrounding environment as the driving force for discharge of the active is supplied from within the system.

However, the above mentioned articles and devices used to control mosquitoes have disadvantages. The combustion of mosquito coils requires a safe burning site and results in ash and unpleasant smoke. The burning of candles exposes a naked flame and therefore requires a safe burning site, while the use of electricity to heat an insecticidal device restricts portability and is costly and unreliable in some developing countries

Ambient emanation is a term used to describe the passive evaporation of a substance into the immediate environment under ambient conditions to elicit a beneficial effect. The availability of insecticides that vaporise at ambient conditions lend themselves to being incorporated into ambient emanation products that are designed to control flying insects.

Ambient emanation products designed to control flying insects have many benefits: they are efficient and do not need an internal energy source such as a heater or a fan; they provide long lasting and continuous protection; they do not release unpleasant smoke or odours; there is no burning hazard; they are portable, modern and practical.

Compared to the availability of traditional pest control products that require a heater or a fan, ambient emanation products are uncommon. Some examples include ambient temperature moth repellent products that rely on passive evaporation of the insecticide from a substrate into the environment. However, known ambient temperature pest control products, also have disadvantages. Firstly, many of the prior art products are only effective in small, enclosed spaces and require significant air movement for the insecticide to be effective in a larger area of space. Secondly, there is a short falling in the number of cost-effective products that are able to work efficiently using low doses of insecticide for the control of insects other than moths, such as mosquitoes.

In attempting to address the above short comings, the present inventors have found an effective way for controlling insects, in particular mosquitoes, using a combination of cellulosic based substrate or matrix and a vapour active pyrethroid that allows passive emanation of the pyrethroid from the substrate at dose levels that achieve a minimum effective emanation rate and are cost effective. These findings have previously been described in co-pending application GB Patent Application No. 0326053.6, the entire contents of which are incorporated herein by reference. The present invention provides an alternative to the cellulosic based substrate or matrix for controlling flying insects disclosed in co-pending application GB Patent Application No. 0326053.6.

Disclosure of the Invention

By using a combination of a multifilament polyester or polyamide substrate and a vapour active substance, the present inventors have determined a means by which the passive emanation of the vapour active substance from the substrate at dose levels that achieve a minimum effective emanation rate and that are cost effective is accomplished. In addition, the inventors have determined that the rate of emanation of vapour active pyrethroids from multifilament polyester or polyamide materials is significantly higher than other substrates such as paper or glass. This enables the development of products with considerably reduced emanation surface areas in order to achieve an effective air-borne insecticide concentration. The inventors have also

determined that high passive emanation rates of vapour active substances such as, for example, aroma chemicals, are able to be achieved with the multifilament polyester or poly amide substrates.

In a first aspect, the invention provides an emanator for emanating at least one vapour active substance into surrounding air by passive emanation comprising a multifilament polyester or polyamide substrate coated and/or dosed with the at least one vapour active substance, wherein the multifilament polyester or polyamide substrate is in the form of a netting or is a knitted or woven fibre. Preferably the vapour active substance is a vapour active pyrethroid. In a second aspect, the invention provides an emanation device for emanating a vapour active substance into the air by passive emanation adapted to retain an emanator according to the first aspect.

In a third aspect, the invention provides an insecticide emanator for emanating a vapour active pyrethroid into surrounding air by passive emanation comprising a multifilament polyester or polyamide substrate coated and/or dosed with the vapour active pyrethroid.

In a fourth aspect, the invention provides an insect control article for emanating an insecticide into the air by passive emanation, the insect control article being adapted to retain an insecticide emanator according to third aspect. In a fifth aspect, the invention provides a method of emanating a vapour active substance into the air by passive emanation comprising: providing a emanator in accordance with the first aspect; exposing the emanator in an environment with non-augmented air movement; and allowing the vapour active substance to passively emanate from the emanator into the air.

In a sixth aspect, the invention provides a method of controlling flying insects comprising the steps of: providing an insecticide emanator in accordance with the third aspect; exposing the emanator in an environment with non-augmented air movement; and allowing the vapour active pyrethroid to passively emanate from the emanator into the air.

In a seventh aspect, the invention provides the use of an emanation device according to the second aspect to passively emanate a vapour active substance into the air.

In an eighth aspect, the invention provides the use of an insect control article according to the fourth aspect to control flying insects.

As used herein, the term, "polyester fibre" or "polyamide fibre" encompasses any woven or knitted fabric or any other mesh fabric such as lace or crochet, that is manufactured from a polyester or polyamide yarn.

According to § 303.7 Generic names and definitions for manufactured fibers from the Rules and Regulations under the United States Textile Fiber Products Identification Act 16 CFR Part 303, a "polyester" is defined as a manufactured fibre in which the fibre-forming substance is any long chain synthetic polymer composed of at least 85% by weight of an ester of a substituted aromatic carboxylic acid, including but not restricted to substituted terephthalate units,

PC-R-O-CO-C ₆ H ₄ -CO-O-),

and para substituted hydroxy-benzoate units,

p(-R-O-C ₆ H ₄ -CO-O-).

Persons skilled in the art, however, will appreciate that this is only one definition of the term "polyester" and other definitions are also encompassed by the invention.

In a preferred embodiment of the invention, the multifilament polyamide fibre substrate is nylon. According to the Federal Trade Commission of the United States, "nylon" is defined as a manufactured fibre in which the fibre-forming substance is a long-chain synthetic polyamide having recurring amide groups as an integral part of the polymer chain.

(-C0-NH-)

An amide group is shown above. Persons skilled in the art, however, will appreciate that this is only one definition of the term "nylon" and other definitions are also encompassed by the invention.

It will be understood that a "substrate" is something which underlies or serves as a basis or foundation which is able to be coated and/or dosed with a vapour active substance from which the vapour active substance may emanate.

In a preferred embodiment, the substrate is a multifilament knitted or woven substrate and more preferably, the multifilament substrate is in the form of a net.

As used herein, the term "net" substrate encompasses any open fibre substrate made of knotting the intersections of the fibres to form meshes. Net can be made in a variety of mesh sizes and weights matched to varying end uses

As used herein, the term "knitted" substrate encompasses a method of constructing fabric by an interlocking series of loops of one or more fibres. The two major classes of knitting are warp knitting and weft knitting. In addition, as used herein, the term "knitted" substrate also encompasses any fibre substrate in which the one or more filaments of a fibre pass through one another as they cross each other. This is opposed to a "woven" substrate wherein the one or more filaments of a fibre pass above and below one another as they cross each other.

Detailed Description of the Invention According to the present invention, the multifilament polyester or polyamide fibre substrate is coated and/or dosed with a solution containing at least one vapour active substance. The substrate is deemed "coated" with the vapour active substance when the substance is either partially or completely distributed within the fibres of the substrate in such a manner that the substance fills all or some of the interstices of the substrate and is directly held within the substrate and supported thereby, but is not absorbed within the individual polyester or polyamide filaments. The substrate is deemed to be "dosed" with the vapour active substance when a specific quantity of the substance is applied to the substrate and either partially or completely coats the substrate as described above.

Multifilament polyester or polyamide fibre substrate

It will be appreciated that a polyester or polyamide fibre substrate may be composed of a number of filaments and hence be termed "multifilament" polyester or polyamide or be composed of a single filament and hence be termed "monofilament" polyester or polyamide. The present invention relates to the use of multifilament polyester or polyamide fibre substrates. The inventors have found that the use of multifilament polyester or polyamide fibre substrates results in increased emanation rates compared to other substrates including cellulosic based substrates such as 18gsm tissue paper. In general, the multifilament aspect also provides for an increase in emanation surface area compared to monofilament materials due to an increased number of filaments present to construct the fibres. In addition, the multifilament

character of the multifilament polyester or polyamide substrates enhances the wetting properties of the substrate. Ease of wetting is an important aspect as it allows for the rapid distribution of a vapour active substance such as, for example, a vapour active pyrethroid throughout the substrate simply by applying droplets of a solution containing the vapour active substance to the substrate and allowing it to spread by capillary action. Generally, monofilament polyesters or polyamides do not wet easily and are therefore unsuitable for use in this invention, particularly when using a dosing technique that relies on the distribution of the vapour active solution throughout the substrate by capillary action. Another associated advantage with multifilament polyester or polyamide substrates is that vapour active substances such as pyrethroids will vapourise to a point where there is no residual substance remaining on the substrate. When multifilament polyester or polyamide substrates are dosed with, for example, vapour active pyrethroids in a carrier solvent, they evaporate to completion. This is contrary to what is observed with cellulosic based substrates whereby a small amount of the pyrethroid remains absorbed to the substrate and is unavailable for release under ambient conditions.

The multifilament polyester or polyamide substrate in accordance with preferred embodiments of the invention is a woven or knitted fabric. In the case of a woven multifilament substrate, any type of weave is suitable and may include plain, twill or satin weaves for example which have their usual meanings in the art. Alternatively, knitted fabrics may include both warp and weft knitting for example which have their usual meanings in the art. The multifilament polyester or polyamide (also referred to as a "polyester or polyamide thread" or " polyester or polyamide yarn") may be zero-twist, twisted or plaited or any other form suitable for weaving or knitting and may be manufactured from a continuous filament or from staple fibres.

The multifilament polyester or polyamide fibre substrate has a filament count per thread greater than one however counts of about 10-40 are preferred.

Preferably also the multifilament polyester or polyamide fibre substrate has a filament diameter of about 10-30 μm and may be circular, trilobal, hollow or any other suitable cross-sectional shape suitable for knitting or weaving.

The multifilament polyester or polyamide fibre substrates may have a hole size greater than about 0.05 mm ² , preferably at about, or above, 0.5 mm ² .

Preferably also, the multifilament polyester or polyamide fibre substrates have a porosity (ratio of the void area contained within the boundaries of the fabric or material

to the total area (solid matter and voids) expressed as a percentage) of more than about 30% however, substrates with a porosity of more than about 40% are preferred.

The multifilament polyester or polyamide fibre substrates may have an air permeability (expressed in centimetres per second and measured according to Australian Standard AS 2001.2.34-90 (Determination of Permeability of Fabrics to Air) of more than about 400 cm/s, however substrates having an air permeability of more than about 444 cm/s are preferred.

Vapour active substance

(i) Vapour active pyrethroids

It will be understood that vapour active pyrethroids are those that vaporise at ambient temperature (ie. about 18-4O ⁰ C) without heat or combustion. The vapour active pyrethroids are preferably selected from the group consisting of metofluthrin (1.9 mPa/ 25°C), transfmthrin (0.40 mPa/20°C), empenthrin (14 mPa/23.6°C), methothrin, tefluthrin (8.4 mPa/20°C,), and fenfluthrin (1.0 mPa/20°C), or combinations thereof. The vapour pressures of these compounds are given in parentheses. It will be appreciated that one or more vapour active pyrethroids may be employed in the present invention. Preferably, the vapour active pyrethroid is metofluthrin. Metofluthrin has high potency against mosquitoes, flies, and moths. The chemical name of metofluthrin is 2,3,5,6-tetrafluro-4-(methoxymethyl)benzyl-(EZ)- (lRS^RSilRS^S^^^-dimethyl-S-φrop-l-enyOcyclopropanecarboxyl ate. Metofluthrin is available from the Sumitomo Chemical Company.

The emanation or release of the vapour active pyrethroids from multifilament polyester or polyamide fibre substrates into the surrounding environment may be referred to as the emanation rate or release rate and will be understood to mean the depletion of an amount of vapour active pyrethroids from the multifilament polyester or polyamide fibre substrate over a certain period of time and has a unit of measurement of mg/h. The emanation rate is a measure of efficacy in controlling flying insects. The inventors have found that, apart from environmental factors such as temperature and airflow, the emanation rate is primarily affected by the air permeability and porosity of the multifilament polyester or polyamide fibre substrate for any given surface area. The amount of the vapour active pyrethroid coated and/or dosed onto the substrate will determine the duration of the emanation of the pyrethroid. The present inventors have found that emanation of a vapour active pyrethroid, preferably metofluthrin, from a multifilament polyester or polyamide fibre substrate

into the atmosphere at a rate of at least about 0.040 mg/h, more preferably at least about 0.075 mg/h, is required to effectively control flying insects, particularly mosquitoes and moths at a temperature in the range of about 18-4O ⁰ C, more preferably, 21-35 ⁰ C. Throughout the specification, the emanation rate of about 0.040 mg/h may be referred to as the minimum effective emanation rate (MEER). This MEER may be achieved by controlling a variety of parameters including but not limited to the type of multifilament substrate; the available emanation surface area and the folding of the multifilament substrate; temperature, and air flow. The possibility of achieving emanation of the vapour active pyrethroid from the multifilament polyester substrates according to the present invention at low temperatures in the range of about 18-21 ⁰ C contributes to the commercial viability of the various aspects of the invention.

It will be understood that an environment with non-augmented air movement refers to natural air movement that passes over and/or through the multifilament polyester substrate, thereby allowing the vapour active insecticide to passively emanate into the atmosphere. It excludes the use of fans, heat and other mechanical means of increasing air movement Suitable environments include but are not limited to enclosed rooms and open volumes of space, such as patios and the like, with air movement provided by natural causes such as breeze entering through windows or people moving around in a room. Throughout the specification, the term "passive emanation" is used to describe the process by which the vapour active pyrethroid emanates from the multifilament polyester substrate into the atmosphere without the application of external energy.

As noted above, the emanation rate of the vapour active pyrethroid from the multifilament polyester substrate is affected by a number of parameters, apart from environmental factors such as temperature and airflow, including, air permeability and porosity. This in turn means that products effective in killing and/or repelling insects over different time periods, such as for 8 h and 300 h, could be different.

Some air movement is required in order for the pyrethroid to emanate from the substrate into the atmosphere. The rate of emanation increases with increased air flow. A minimal air flow, such as the movement of people or open windows and/or doors, is sufficient to allow a minimum emanation rate of about 0.040 mg/h, and the preferred emanation rate of about 0.075 mg/h.

The vapour active pyrethroid may be applied to the multifilament polyester or polyamide fibre substrate by any method known to persons skilled in the art, for example, a solution of the pyrethroid could be applied by droplets, spraying or dipping.

(U) Aroma chemicals

In one embodiment of the invention, the polyester or polyamide fibre substrates may be coated and/or dosed with natural or synthetically derived aroma chemicals. These include substances preferably having a boiling point range of about 60-250°C (e.g. monoterpenes and sesquiterpenes, including monoterpene and sesquiterpene alcohols, aldehydes, ketones, esters, oxides and hydrocarbons such as linalool, geraniol, citronellal, citral, geranial, menthone, linalyl acetate, bornyl acetate, 1,8-cineole and limonene); and essential oils.

The term "essential oils" will be understood to mean a volatile and aromatic liquid which is isolated by a physical process from an odoriferous plant of a single botanical species. The oil bears the name of the plant from which it is derived; for example rose oil or lavender oil. These essential oils obtained from plants may be extracted by distillation, steam distillation, expression or by extraction with fats or organic solvents. It will be understood that "aroma chemicals" are natural isolates or synthetics which have an aroma. The natural isolates are removed mechanically (eg by distillation) or chemically (eg hydrolysis or salt formation) from a natural essential oil. The isolates are further modified. For example rose and lavender oils may be distilled to produce linalool, which may then be acetylated to make linalyl acetate. Aroma chemicals are the main constituents of essential oils. These constituents are generally monoterpenes and sesquiterpenes, including but not limited to alcohols, aldehydes, ketones, esters, oxides and hydrocarbons. Preferably, the natural or synthetically derived aroma chemicals have a boiling point in the range of approximately 60-250 ⁰ C.

The aroma chemicals may be applied to the multifilament polyester or polyamide fibre substrate by any method known to persons skilled in the art, for example, a solution of the aroma chemical could be applied by droplets, spraying or dipping.

(in) Carrier solvent According to the invention, the multifilament polyester or polyamide fibre substrate may be coated and/or dosed with the vapour active pyrethroid, preferably metofluthrin, dissolved in a carrier solvent. The carrier solvent may be any solvent or combination of solvents in which the vapour active pyrethroid is soluble.

The inventors have identified two important physical properties of solvents that may be used to characterise and classify preferred carrier solvents. The first is the boiling point and the second is the evaporation rate according to the ASTM D3539-87.

Preferably, the carrier solvent has a boiling point in the range between about 33- 285°C, more preferably, about 50-265 ⁰ C.

The carrier solvent may be selected from, but not limited to, chlorinated hydrocarbons (e.g. 1,1,1-trichloroethane, dichloromethane, chloroform); alcohols (e.g. methanol, ethanol, n-propanol); ketones (e.g. acetone); alcohol and ketone mixtures

(e.g. acetone/ethanol (1 :1 by volume)); normal paraffins with a boiling point range of about 155-276 ⁰ C (e.g. Norpar 12); dearomatised aliphatic hydrocarbons and their blends in the boiling point range of about 33-265°C (e.g. pentane, heptane, hexane,

Exxsol D40, Exxsol D80 and Exxsol DlOO); isoparaffins in the boiling point range of about 150-285 ⁰ C (e.g. Isopar G, and Isopar M); glycol ethers in the boiling point range of about 120-243 ⁰ C; natural or synthetically derived aroma chemicals as discussed above. The Norpar, Exxsol and Isopar solvents are all available from Mobil Exxon.

The inventors have found that the use of low boiling point solvents with high evaporation rates will be effective as carrier solvents. The inventors have also found that the use of higher boiling point solvents with lower evaporation rates leads to a preferred embodiment of the invention.

The multifilament polyester or polyamide fibre substrate is coated and/or dosed with the vapour active pyrethroid, preferably metofluthrin in a carrier solvent.

The vapour active pyrethroid, preferably metofluthrin, is dissolved in the carrier solvent and the resulting solution is applied to the multifilament polyester or polyamide fibre substrate such that the vapour active pyrethroid is distributed, preferably evenly, throughout the multifilament polyester or polyamide fibre substrate. The carrier solvent used is preferably a solvent that does not evaporate within about 10 minutes after application onto the multifilament polyester or polyamide fibre substrate and more preferably is characterised by having a high boiling point and a low evaporation rate.

However, the evaporation rate of the carrier solvent is required to be faster than that of the vapour active pyrethroid.

Preferably, the carrier solvent has a boiling point in the range of about 120- 285 ⁰ C, more preferably about 150-265 ⁰ C, and may be selected from known solvents including but not limited to normal paraffins with a boiling point range of about 155- 276 ⁰ C, such as Norpar 12; dearomatised aliphatic hydrocarbons and their blends in the boiling point range of about 150 -265°C such as Exxsol D40, Exxsol D80 and Exxsol DlOO; isoparaffins in the boiling point range of about 150-285 ⁰ C such as Isopar G and Isopar M and glycol ethers in the boiling point range of about 120-243 ⁰ C.

In a preferred embodiment, the carrier solvent used has an evaporation rate according to ASTM D3539-87 of less than about 1.0, a boiling point in the range of about 120-285 ⁰ C, preferably about 150-265°C.

It will be understood that solvents used for applying a vapour active pyrethroid to the multifilament polyester or polyamide fibre substrate may be employed as carrier solvents in all aspects of the present invention that require a carrier solvent.

While the use of carrier solvents is discussed with particular reference to vapour active pyrethroids, it will be understood that the use of carrier solvents as described above is contemplated in connection with the application of any vapour active substance to the multifilament polyester or polyamide fibre substrate requiring the presence of a carrier solvent.

Insect control

The multifilament polyester or polyamide fibre substrate, insecticide emanators and the insect control devices of the present invention are used in one embodiment to control flying insects. The flying insects may be selected from but not limited to biting Dipterous pests (Order Diptera) such as mosquitoes (Family Culicidae), biting midges (Family Ceratopogonidae), black flies (F. Simulidae), sandflies (certain Psychodidae) and biting flies (various families eg Muscidae and Tabanidae) and non-biting Dipterous insects (e.g. flies and midges of various families including, but not limited to Muscidae, Calliphoridae, Drosophilidae, Chironomidae and Psychodidae) and certain moths (Order Lepidoptera). Preferably, the multifilament polyester substrate and the insect control devices of the present invention are used to control mosquitoes.

It will be understood that "control" of the flying insect population includes but is not limited to any one of or a combination of killing, repelling (bite inhibition) or knocking down a flying insect. It will be appreciated that a typical way of measuring the performance of an insecticide is in the form of "knockdown" or by using "bite inhibition" studies.

Articles for retaining the emanator of the invention

While it is envisioned that the emanator comprising the multifilament polyester or polyamide fibre substrate is a self supporting structure, this is not always the case.

In configurations in which the emanator is not self-supporting, an article capable of retaining' and supporting the emanator will be required. Accordingly, the present invention also provides an insect control article and an emanation device for retaining the emanator or insecticide emanator as described herein. It will be appreciated that the

insect control article or emanation device of the present invention may take on any form provided it is able to retain the emanator or insecticide emanator as described herein so as to achieve emanation of the vapour active substance into the air. In one embodiment, the emanation device or the insect control article is in the form of the packaging means as described in GB Application No. 0326056.9 (PCT/GB2004/004369), the entire contents of which are incorporated herein. In this form, the emanator, or the insecticide emanator, comprising the multifilament polyester or polyamide fibre substrate will have at least two ends which are attached to two backing boards made from, or lined with, protective material into which the vapour active substance is unable to migrate or be absorbed. Figure 5 shows an emanator 1 according to one embodiment of the invention comprising a multifilament polyester net substrate 3 having two ends that are attached to two backing boards 5, 7. The two backing boards are then able to be retained within a packaging means comprising a top, base and a longitudinal member extending therebetween as described in GB Application No. 0326056.9 (PCT/GB2004/004369). The emanator comprising a multifilament polyester or polyamide fibre substrate when retained in the insect control article or emanation device in accordance with the various aspects of the invention may be collapsed between an open form and a closed form such that it is an expandable and re-closable arrangement This means that when emanation of the vapour active substance is not required, the multifilament polyester or polyamide fibre substrate/insect control article may be closed and stored in a form which minimises the surface area exposed to the environment containing the vapour active substance. Conversely, when emanation of the vapour active substance is required, the multifilament polyester or polyamide fibre substrate/insect control article may be expanded into an open form thereby increasing the surface area of multifilament polyester or polyamide fibre substrate containing the vapour active substance that is exposed to the atmosphere allowing the vapour active substance to emanate into the atmosphere.

It will also be appreciated that once the multifilament polyester or polyamide fibre substrate is coated/dosed with, for example, the vapour active pyrethroid, it may need to be stored for significant periods of time. It is therefore important that the packaging material or protective material is effective in minimising the release/emanation rate of the vapour active pyrethroid from the multifilament polyester or polyamide fibre substrate into the atmosphere. This is most successfully achieved when the packaging material or protective material is a material through which the vapour active pyrethroid will not migrate and/or be absorbed.

Preferably, the packaging/protective material used in the present invention is selected from but not limited to glass, metal foil, preferably aluminium foil, and laminates thereof; polyester, metalised polyester, heat sealable polyester film, polyester based film and formed sheet, such as amorphous PET and crystalline PET, and laminates thereof; and acrylonitrile-methyl acrylate copolymers and laminates thereof.

It has been found that when the multifilament polyester or polyamide fibre substrate is packed in the presence of a significant amount of carrier solvent, a greater range of packaging and protective materials may be used than when the multifilament polyester substrate or polyamide fibre substrate is packed in the absence, or in the presence of only a small amount, of the carrier solvent.

In order to better understand the invention, a number of examples will now be described with reference to the following figures.

Brief Description of the Figures Figure 1 is a graph showing the amount (mg) of metofluthrin emanated from a multifilament polyester substrate as a function of time. Paper (18gsm) is used as a control.

Figure 2 shows photographs of multifilament polyester or polyamide fabrics (#1 to 8, 11, 19 and 22) as tested and discussed in Example 3. All photographs are taken to the same scale.

Figure 3 shows a photograph of a woven monofilament polyester substrate that is outside the scope of the present invention.

Figure 4 is a bar graph showing bioefficacy results as discussed in Example 4. Figure 5 is a perspective view of an emanator in accordance with an embodiment of the invention.

As previously described, the polyester or polyamide substrates of the invention relate to multifilament (figure 2), as opposed to monofilament (figure 3), polyester or polyamide fibre substrates. The present inventors have found that high rates of emanation of vapour active substances are able to be achieved with multifilament polyester or polyamide fibre substrates compared to other substrates such as paper or glass. Without wishing to be bound by theory, this is likely due to increased substrate porosity and air permeability.

Examples

Example 1 - Determination of the emanation rate of metofluthrin from a range of substrates A range of multifilament polyester fabrics (as described in Table 1) of size 625 cm ² (equivalent to the size of an A4 sheet of paper), were dosed with metofluthrin (50 mg) to determine the emanation rate from these substrates.

The metofluthrin was dissolved in Norpar 12 and dosed on to the substrate using a pipette. A volume of 0.8 mL of the metofluthrin in Norparl2 solution was required to achieve complete wetting of all the polyester fabrics examined. The samples were hung and aged in a chamber at 28 ⁰ C with low airflow for up to a maximum of 50 hours. The amount of metofluthrin remaining on the samples was measured at various intervals during the ageing period.

Figure 1 shows an example of a plot obtained from one of these experiments performed using multifilament polyester (7) having a density of 51 gsm and a porosity of 60%. The amount of metofluthrin released from the sample is plotted as a function of time. The line of best fit generated is used to calculate the release rate from the sample. In all of the experiments 18 gsm paper (A4 flat) was used as a control.

A summary of the relative emanation rates obtained for metofluthrin is shown in Table 1.

Table 1

a Density (gsm) is de ne as the mass (g) of the substrate per unit area m b Porosity (%) is defined as the ratio of the volume of air or void contained within the boundaries of a material to the total volume (solid matter plus air or void) expressed as a percentage.

From the above results, it is concluded that increased emanation rates are achieved from many of the polyester fabrics examined compared to 18 gsm paper. The results also demonstrate that essentially linear release kinetics are observed for metofiuthrin emanating from all the samples tested.

Example 2 - Determination of the emanation rate of metofiuthrin from various substrates in relation to the air permeability of the substrates

The air permeability of a range of multifilament polyester and other substrates (randomly assigned sample codes, Table 2) was investigated to determine the effect of the air permeability on the evaporation rate of a vapour active substance from the substrates.

The air permeability was tested using the Australian Standard test method AS 2001.2.34-90. Air permeability is used in evaluating and comparing the "breathability" of various fabrics for end uses such as raincoats, tents, and specialised clothing. The principle of the test is that air is drawn through a specified area of fabric. The rate of airflow is adjusted until a specified pressure difference between the two fabric surfaces (face and back) is achieved. The airflow is measured and the air permeability is calculated.

The emanation (evaporation) rate of a solvent (Norpar 12) from the samples in Table 2 was also determined by measuring the weight loss from the substrates against time. Approximately 0.5g of the solvent was sprayed evenly onto a specified area of the substrate (625 cm ² ) which was then placed on a specially designed lightweight metal jig. The jig was positioned on an electronic balance so that the weight loss over time could be recorded. The substrate remained in a flat and fully extended state throughout the experiment so that the solvent could evaporate under ambient conditions. All samples were measured under the same conditions in order to compare the evaporation of the solvent from each substrate. The results are expressed in terms of a relative evaporation rate. The relative evaporation rate is expressed as the the half- life of the Norpar 12 as it evaporated from the substrate divided by the half-life of Norpar 12 as it evaporated from 18 gsm paper. As an example, it is understood that a substrate with a relative evaporation rate of 2 will have a solvent evaporation rate at twice the rate of evaporation from 18gsm paper under ambient conditions.

A summary of the air permeability and relative evaporation data is shown in Table 2.

Table 2

a Density (gsm) is defined as the mass (g) of the substrate per unit area (m ) b Porosity (%) is defined as the ratio of the volume of air or void contained within the boundaries of a material to the total volume (solid matter plus air or void) expressed as a percentage. c Non-porous substrate where the evaporation surface is independent of the porosity or the density.

From these results it is concluded that the evaporation rate of a substrate is clearly dependent on the air permeability of the substrate. Substrates having an air permeability greater than 444 cm.s ^'1 (which is the limit of the measurement) show dramatic increases in evaporation rate compared to those substrates with reduced air permeability. In addition, based on the emanation of metofluthrin from multifilament polyester substrates (see Example 1) where the sample (polyester (1) multifilament woven voile) had an emanation rate of 1.5 compared to 1.0 for 18 gsm paper, it is concluded that a minimum air permeability of about 400 cm.s ^'1 , more particularly, 424

cm.s ^"1 is required to achieve faster emanation rates of metofluthrin than 18 gsm paper under ambient conditions.

Example 3 - Determination of the emanation rate of metofluthrin in relation to various parameters as tested on a number of substrates

The air permeability, evaporation half life, relative evaporation rate and metofluthrin release rate (relative to the metofluthrin release rate on 18 gsm paper = 1) was determined for a number of polyester and polyamide fibre substrates as shown in Table 3. Photographs of the actual fabrics are shown in Figure 2. The results demonstrate that good metofluthrin release rates are achieved with all of the multifilament polyester and polyamide fibre substrates. The results also demonstrate that as the air permeability (measured as described in Example 2), of the various multifilament polyester and polyamide fibre substrates approaches and surpasses 400 cm.s ^"1 , increased evaporation and metofluthrin release rates are achieved for the multifilament polyester and polyamide fibre substrates relative to the evaporation rate as measured on 18 gsm paper. The results further demonstrate that increased evaporation and metofluthrin release rates are achieved for the multifilament polyester and polyamide fibre substrates compared to 18 gsm paper as the substrate porosity approaches and surpasses 30%. Also observed is a decrease in the evaporation half-life (min) of a C12 hydrocarbon solvent with increasing substrate air permeability and porosity which suggest that the evaporation of a vapour active substance (in this case a C 12 hydrocarbon solvent) is dependent on the . substrate porosity and air permeability. For instance, a significant decrease in the evaporation half-life of the C12 hydrocarbon solvent is observed for substrates having a porosity above about 30% and an air permeability above about 400 cm.s ^"1 .

The results further confirm that of all the multifilament polyester and polyamide fibre substrates tested, the best results were achieved with the multifilament netting substrates; that is, with the knitted polyester netting (in terms of the highest relative metofluthrin release rate), the knitted nylon netting and the knitted polyester netting (in terms of the highest relative evaporation rate).

Table 3

* Evaporation half-life based on C12 hydrocarbon solvent ** Relative to 18 gsm paper = 1 ***Relative to 18 gsm paper = 1

Example 4 -Bioeffϊcacy example

10 In this example, the mosquito bite inhibition properties of insecticide-treated multifilament woven polyester fabric was compared to insecticide-treated paper. The surface area / dose response relationship of these two substrates was also investigated.

Various pieces of multifilament woven polyester fabric and 18 gsm paper were dosed with metofluthrin according to the following table, the metofluthrin being

15 previously dissolved in 0.8 ml of a normal paraffin solvent (boiling range 189 - 218 ⁰ C).

Table 4

The amount of active was reduced proportional to the progressive reduction in geometric surface area of the substrate. As a result, the amount of active per unit area remains constant for each treatment. Two separate trials were compared to evaluate each substrate. It is important to understand though, that the geometric surface area of the substrate and not the amount of metofluthrin present determines the release rate. In this regard, the inventors have verified that the emanation rate is independent of metofluthrin concentration.

The treated substrates were, in turn, suspended from the centre of the ceiling of a 40 m ³ purpose built, test chamber, the chamber being maintained at a temperature range of 26-28 ⁰ C and a relative humidity range of 50-70%.

After 15 minutes had elapsed, 100 female Aedes aegypti mosquitoes were introduced into the test chamber.

An assessment of bite inhibition was conducted at 5 minutes after the mosquito release. In this assessment a human forearm was introduced into the chamber via a vent in the wall of the chamber. The number of mosquitoes landing and attempting to bite were counted over a 2-minute period and the procedure was repeated using a second vent and second arm so as to give a total exposure of 4 minutes during the assessment time.

This procedure was repeated to give a total of three (3) replicates per test formulation, an untreated control being also conducted in order to establish mosquito bite density. Percent mosquito repellency for the respective treatments was then calculated against the untreated control.

As can be seen from Figure 4, for mosquito bite inhibition from 18 gsm paper, as the surface area of the substrate is reduced there is a clear drop in effectiveness.

However, good bite inhibition results are observed for all of the surface areas examined for the polyester knitted fabric. The emanation rate studies presented in Example 2, have shown that the release of metofluthrin from certain polyester knitted fabrics is faster than that from 18 gsm paper. The bite inhibition results in this example support the conclusion that the absolute emanation rate of metofluthrin is dependent on the substrate and subsequently this rate is proportional to the surface area of the substrate. In the current study and in the case of the smaller surface area 18 gsm paper, the emanation rate is reduced to an extent that it is no longer effective against mosquitoes.

However for the polyester fabric it is shown that although the emanation rate is reduced on the smaller surface area samples the amount of metofluthrin emanated under these conditions is still effective against mosquitoes. The polyester knitted fabric reaches an effective vapour concentration (as measured by % mosquito repellency) of metofluthrin faster than 18 gsm paper due to its higher overall release rate from this substrate.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.