WO1990003111A1

WO1990003111A1 - Chemical formulations

Info

Publication number: WO1990003111A1
Application number: PCT/GB1989/001159
Authority: WO
Inventors: Howard Bernard Dawson
Original assignee: Nc Development, Inc.
Priority date: 1987-03-30
Filing date: 1989-09-29
Publication date: 1990-04-05
Also published as: FI911554A0; NO911243D0; GR1000535B; GB8822937D0; DK56691A; NO911243L; GR890100622A; EP0436651A1; DK56691D0

Abstract

Water-miscible pesticidal formulations whose average particle size is at most 200 nm include water, oil, a surfactant, and a cosurfactant, which comprises a wetting agent such as a polysiloxane-based copolymer such as a polysiloxane-polyether copolymer. Such formulations have particular application in the delivery of pesticides such as insecticides and acaricides, and therefore either the oil may be a pesticide or the formulation may comprise a pesticide dissolved in the oil. The pesticide may be a pyrethroid such as cypermethrin or deltamethrin. The formulations can be molecular solutions, micellar solutions or microemulsions (water-in-oil or oil-in-water) and are generally clear.

Description

CHEMICAL FORMULATIONS

This invention relates to chemical formulations which are useful as water-miscible preparations of compounds which are normally regarded as water-insoluble and to their use as pesticidal formulations.

in particular, the invention relates to formulating water-insoluble oil-soluble substances in water as small particles whose Z average mean size particle size is less than 200 nm. The Z average mean size can be defined as the model free mean of light scattering. such formulations include microemulsions, micellar solutions and molecular solutions.

Microemulsions are in themselves known. They are one of three identified types of dispersion (as distinct from a molecular solution) of oil, water and surfactant. (The term "oil" is used in this specification to mean any non-aqueous solvent in which a substance of interest is soluble and which is immiscible with water.) These three types of dispersion are: microemulsions, micellar solutions and normal emulsions (or macroemulsions) .

Macroemulsions appear white or opaque and are characterised by their property to separate into their two original liquid phases on standing; the average particle diameter will generally be above 200 nm. Microemulsions and micellar solutions are translucent and do not separate. Microemulsions can be considered as having average droplet (or particle) diameters of from 10 to 200 nm, micellar solutions as having average particle diameters of from 2 nm to 10 nm and molecular solutions as having average particle diameters of less than 2 nm. Recent evidence, however, does suggest that microemulsions with droplet diameters below 10 nm are possible.

As with macroemulsions, microemulsions can be of the water-in-oil (w/o) or oil-in-wa^'ter (o/w) type and can be made to invert from one to another.

One of the best means of differentiating between formulations in accordance with the invention and macroemulsions (and between microemulsions, micellar solutions and molecular solutions) is on the basis of particle or droplet size (usually measured as averages) . Average particle or droplet size may be measured with a laser particle sizer, such as the MALVERN AUTOSIZER 2c (Malvern Instruments, Malvern, Hereford & Worcester) using glass cells as sample containers.

Other techniques can be used to determine additional or alternative characteristics of formulations of this invention. These include x-ray studies, electron microscopy, light scattering depolarisation and nmr. In general, nmr measurements are used to resolve theoretical questions regarding the state or location of molecules in microemulsions. The line width for protons in molecules can indicate freedom of the molecules to thermal motion, the broadening of the line indicating greater restriction of motion. The chemical shift of water is different when it is distributed in spheres or in cylindrical or lamellar micelles. Other studies are possible using nmr, in addition.

FR-A-2187226 corresponds to CA-A-1007985 and discloses insecticidal compositions comprising an anionic surfactant and a hydrotrope.

FR-A-1026169 discloses various emulsions, which may be useful in formulating insecticides comprising an alkylsulphonate surfactant and a polar compound such as an alcohol, an amino, a phenol or an acid.

US-A-3954967 discloses "microcolloids" containing a resin and a polar solvent.

EP-A-0062181 corresponds to US-A-500348 and relates to apparently conventional emulsions containing high HLB surfactants.

EP-A-0107009 corresponds t CA-A-1209361 and relates to a development of the subject matter disclosed in EP-A-0062181; again, emulsions containing high HLB surfactants are disclosed.

EP-A-0149051 corresponds to US-A-4737520 also discloses certain emulsion formulations.

US-A-4567161 discloses liquid active ingredient concentrates for the preparation of microemulsions. The microemulsions are stated to be oil-in-water microemulsions. The coemulsif iers are a particular class of glycerin esters having HLB (Hydrophilic/Lipophilic Balance) values of between 12 and 18. The formulations of US-A-4567161 are said to have special significance for pharmaceutical active substances. However, the active ingredient can be a number of other substances including herbicides (a number of which are listed) , fungicides, insecticides, acaricides, nematocides or plant growth regulators. No specific fungicides, insecticides, acaricides, nematocides or plant growth regulators are disclosed or even suggested.

WO-A-8807326, published on 6th October 1988 and incorporated herein by reference, specifically relates to microemulsions and related compositions comprising an aqueous phase, an oil phase, a surfactant and a cosurfactant which is an ethylene oxide propylene oxide block copolymer (as typified by certain members of the PLURONIC PE or PLURIOL PE range from BASF) .

It has now been found that by incorporating a wetting agent in such formulations it is possible to obtain particularly useful microemulsions and other water-miscible formulations whose average particle size is at most 200 nm, which exhibit good spreading and/or contact properties when applied to various surfaces, particularly plant leaves.

According to a first aspect of the present invention, there is provided a water-miscible formulation whose average particle size is at most 200 nm, the formulation comprising water, oil, a surfactant and a wetting agent. As indicated above, if the formulation is a microemulsion, the microemulsion will generally be clear or translucent, except in the viscoelastic gel phase. Micellar solutions and molecular solutions may additionally be clear. Both phases will usually be liquid.

The water can be tap water, although distilled water can be used. The amount of water in the microemulsion will depend on many factors but typically for w/o microemulsions will be from 20 to 70% w/v and for o/w microemulsions it shall be from 40 to 95% w/v. Some hardness in the water, although not essential, may in practice be beneficial. Between 100 and 200 ppm hardness (as CaC0₃) may be appropriate, particularly around 150 ppm or 160 ppm.

As previously stated, the oil need not merely be an "oil" in the sense of a petroleum^' fraction, although such oils are included; the term "oil" is used to mean any non-aqueous solvent in which a substance of interest is soluble and which is immiscible with water; alternatively, the substance of interest may itself be the oil. Having said that, the oil may be animal, vegetable, mineral or silicone or some other organic solvent which is water-immiscible, such as an optionally halogenated hydrocarbon. The hydrocarbon may be aliphatic or aromatic or have both aliphatic and aromatic moieties. Typical solvents include xylene, naphthalene, kerosene, isoparaffins and halogenated hydrocarbons. The surfactant may be any typical emulsifier as found in most macroemulsion systems. The surfactant may be anionic, cationic, zwitterionic or nonionic. Anionic surfactants are more frequently used. Suitable anionic surfactants include hydrocarbon sulphates, sulphonates and sulphamates, especially compounds wherein the hydrocarbon moiety is an alkyl or alkylaryl group. Soaps (hydrocarbyl carboxylates) can also be used, as can sulphocarboxylic acids such ^"as sulphosuccinic acid. Examples of specific anionic detergents that can be used include alkyl benzene sulphonates and sulphonic acids such as C₈ to C₁₆ alkyl benzene sulphonates and sulphonic acids including dodecyl benzene sulphonic acid (a predominately straight chain mixture of which compounds is sold under the trade mark NANSA SSA) . Anionic surfactants which are acids, as opposed to salts, may in general be found to be preferable.

The selection of an appropriate surfactant can be made by one of skill in the art without undue experimentation. As a guiding principle, it should be borne in mind that it is highly preferable to match, in a chemical sense, the structure of the surfactant with the structure of the oil. For example, if the oil is aromatic, such as xylene or naphthalene, it is preferred to use a surfactant having an aromatic moiety, for example an alkyl benzene sulphonate or an alkyl naphthalene sulphonate. If the oil is aliphatic, an aliphatic surfactant is preferred such as an alkyl sulphonate or a dialkyl sulphosuccinate (such as dioctyl sulphosuccinate) or a soap. Another factor in determining the choice of surfactant is the type of microemulsion (w/o or o/w) to be produced. Low HLB surfactants (for example having an HLB of from 4 to 9 , part i cul arly 4 to 7 ) tend to stab i l i s e w/ o microemulsions and should therefore for preference be used for w/o microemulsions and high HLB surfactants ( f or exampl e having an HLB of f rom 9 to 20 , particularly 9 to 20 ) tend to stabi l i se o/w microemulsions and should thus be used for o/w microemulsions . HLB values may be measured by standard techniques .

After having made the initial selection (eg on the basis of HLB) , further selection of the surfactant can be achieved be comparing the hydrophobic portion of the surfactant with the structure of the oil, as discussed above. Polar groups on the surfactant also play an important role and should be considered in the matching process.

An alternative or additional surfactant selection system is based on the phase inversion temperature (PIT) and can therefore be referred to as the PIT system. This system is based upon the temperature at which a surfactant causes an o/w emulsion to invert into a w/o emulsion. It provides information concerning the types of oils, phase volume relationships and the concentration of surfactant which could be used. This system is established on the proposition that the HLB of a nonionic surfactant changes with temperature; the inversion of an emulsion type occurs when the hydrophilic and lipophilic tendencies of the surfactant just balance. No emulsion forms at this temperature. Emulsions stabilised with nonionics tend to be o/w types at low temperatures and w/o types at high temperatures. From the microemulsion standpoint, the PIT system has a useful feature in that it can throw light on the chemical type of surfactant preferred to match a given oil.

Wacer-miscible formulations in accordance with the first aspect of the invention include a wetting agent.

As is well known in the art, wetting agents are surface active agents which lower the surface tension of water by a considerable amount, although they may be present only in very low concentration. It is well within the competence of those skilled in the art to determine whether a particular surface active agent (surfactant) is a wetting agent or not. Preferred wetting agents are those for which a 1% (v/v if liquid or w/v if solid) solution in water have a surface tension at 25°C of less than 50 mN.m^"1, particularly less than 40 mN.m^-1 and preferably below 35 or 30m N.m^"1. (Pure water has a surface tension of 73 mN.m^" at 25°C.)

Preferred wetting agents include polysiloxane-based copolymers. Polysiloxane-polyether-copolymers are particularly preferred such as the TEGOPLANT WT series available from Th. Goldschmidt AG, Essen, West Germany. (The word TEGOPLANT is a trade mark.) The copolymers TEGOPLANT WT 10 and TEGOPLANT WT 25 are especially preferred, with TEGOPLANT WT 10 being the most preferred. A 1% (v/v) solution of TEGOPLANT WT 10 has a surface tension at 20.3 mN.m^"1 at 25°C and a 1% (v/v) solution of TEGOPLANT WT 25 has a surface tension of 22.6 mN.m^"1 at 25°C. The HLB of the polysiloxane-based copolymer may be below 10 and possibly below 5. The wetting agent may constitute the cosurfactant or the formulation may contain one or more additional cosurfactants. Two classes of additional cosurfactants are normally preferred for use, although others may be used. Aliphatic alcohols (particularly primary aliphatic alcohols) are a first preferred class. They may have a carbon content of from 5 to 12 or more carbon atoms. Lower homologues (for example C₅ to C₇ alcohols) are used to stabilise certain formulations, including w/o microemulsions and alcohols above C₈ (optionally including C_g) tend to be used to stabilise other formulations, including o/w microemulsions.

Nonionic surfactants form a more versatile group of additional cosurfactants. They can be balanced with the primary surfactant to give systems that are stable as micellar solutions and as both w/o and o/w microemulsions. A whole range of nonionics can be used, including ethylene oxide propylene oxide block copolymers (as typified by the PLURONIC PE or PLURIOL PE range from BASF) and alcohol ethoxylates (as typified by the DOBANOL range from Shell) .

The HLB of the additional cosurfactant may be less than 10 or even less than 5. For example, one nonionic cosurfactant is the ethylene oxide propylene oxide block copolymer containing 10% ethylene oxide sold under the trade mark PLURONIC PE 6100 or PLURIOL PE 6100, which has an HLB of 3.0. Other suitable HLB values for cosur actants are less than 3, for example about 2 or even about 1. Choosing an appropriate additional cosurfactant, if required to be formulated with a surfactant and the other components of microemulsions in accordance with the invention, is possible to one of skill in the art without undue experimentation. The methods previously discussed in relation to the choice of surfactant can also be of assistance in the final choice of cosurfactant and optional additional cosurfactant. Further or in the alternative, the technique of cosurfactant partitioning can be of assistance in the preparation of microemulsions. This approach rests on the premise that the condition responsible for the spontaneous formation and stability of microemulsions came about with a zero (or transiently negative) interfacial tension. The total interfacial tension was given by the formula:

^Yl - *(o/w⁾ ^

Where

i ^{= total} interfacial tension

₍o/w_. ⁼ interfacial tension before addition of stabilising agents and

■• = two dimensional spreading pressure in the monolayer of adsorbed species.

It was then proposed that the initial zero or negative value of the total interfacial tension was the result not so much of a high value of the two dimensional spreading pressure but of the large depression in the value of ( γ _o/w)_a, so that V_A = ( Jf(₀/w₎a ~ ^' ^where ( Y ₀/_W)a) is the interfacial tension after the addition of stabilising agents.

Since most microemulsions appear to form much more readily in the presence of a cosurfactant which is oil soluble, it has been assumed that this material distributed itself between the oil phase and the interface and subsequently changed the composition of the oil so that its interfacial tension was reduced to ( ^₀/_w)_a- This provides a formula with a useful aid to help match emulsifiers (surfactants and cosurfactants) to oils for microemulsification. From an economic standpoint, it is of course desirable only to use a minimum of cosurfactant which is suitable for use in any formulation of the invention under consideration.

Using the cosurfactant partitioning technique, it has been discovered that for any given surfactant, a short chain cosurfactant will tend to produce a w/o system, whereas a long chain cosurfactant will tend to promote an o/w system. In the case of soaps, the larger the size of the (hydrated) cation, the more effective that particular soap will be in promoting an o/w microemulsion.

From the point of view of the present invention, it is immaterial whether the zero interfacial argument as a prerequisite for microemulsion stability is correct. The argument has simply been given as an illustration of how the cosurfactant may be selected. It is accepted that the use of the film balance equation is an over-simplification. From the practical formulator's point of view, however, the expression ()fo/w)a ^{can be} valuable.

The relative proportions of the various ingredients of the formulations in accordance with the present invention can vary widely. For w/o microemulsions, micellar solutions and molecular solutions, broad and preferred ranges of the ingredients may be as follows:

Ingredient Broad w/v Preferred w/v

Oil (including dissolved substance if any) 20 to 50% 30 to 40%

Surfactant l to 20% l to 5%

Cosurfactant 1 to 20% 1 to 5%

Water 20 to 70% 50 to 70%

In general the amounts of surfactant and cosurfactant should be kept as low as possible and the amount of water should be kept as high as possible. The above is subject always to the proviso that the total number of percentage parts of the ingredients cannot exceed 100.

For o/w microemulsions, the broad and preferred concentration ranges of the ingredients can be as follows: Ingredient Broad w/v Preferred w/v

Oil (including dissolved substance if any) 1 to 20% 1 to 10%

Surfactant 1 to 10% 1 to 5%

Cosurfactant 1 to 10% 1 to 5%

Water 40 to 95% 70 to 90%

Again, the above is subject always to the proviso that the total number of percentage parts of the ingredients cannot exceed 100.

A water-insoluble oil-soluble substance which it is desired to formulate may be dissolved in the oil, although it is clear that the oil may itself be the water-insoluble oil soluble substance. This "substance of interest" can be anything which is convenient to be formulated in this manner (including other solvents) . As previously stated, pesticides (in particular insecticides and/or acaricides) such as synthetic pyrethroids and fungicides and herbicides are particular candidates for formulation by means of the present invention.

One synthetic pyrethroid is deltamethrin, which is the common name for 3- (2 , 2-dibromoethenyl) -2 , 2-dimethyl- cyclopropane carboxylic acid cyano (3-phenoxyphenyl) - methyl ester. Deltamethrin is a potent synthetic pyrethroid pesticide, the preparation of the racemic mixture of which is described in DE-A-2439177. Deltamethrin is insoluble in water, but is soluble in organic solvents such as ethanol, acetone, dioxane, xylene and certain petroleum fractions.

Other synthetic pyrethroids include cypermethrin (3- (2 , 2-dichloroethenyl) -2 , 2 -dimethyl eye lop ropane- carboxylic acid cyano(3-phenoxyphenyl} -methyl ester) , permethrin (3- (2, 2-dichloroethenyl) -2, 2-dimethylcyclo- propanecarboxylic acid ( 3 -phenoxypheny 1 ) -methyl ester) and fenvalerate (4-chloro-alpha- ( 1-methylethyl) - benzeneacetic acid cyano( 3 -phenoxyphenyl) methyl ester. Cypermethrin may be prepared as described in DE-A-2326077, permethrin may be prepared as described in DE-A-2437882 and DE-A-2544150 , and fenvalerate may be prepared as described in DE-A-2335347.

Apart from the synthetic pyrethroids, natural pyrethroids, organophosphorus compounds and carbamates are examples of other pesticides us,eful in the present invention. Such other pesticides include non-pyrethroid insecticides and acaricides (such as organophosphorus compounds) and herbicides and fungicides. Organophosphorus compounds include chlorpyritos (Q_.,0- diethyl-O-3 , 5 , 6-trichloro-2-pyridyl phosphorothioate) , chlorpyrif os-methyl (0,0-dimethyl-0-3,5,6-trichloro-2- pyridyl phosphorothioate) , fenitrothion ( _,0-dimethyl- 0-4-nitro-m-tolyl phosphorothioate) and pirimiphos- methyl (0-2-diethylamino-6-methylpyrimidin-4-yl-0,0- dimethyl phosphorothioate) .

Mixtures of pesticides (for example mixtures of pyrethroids or mixtures of pyrethroi ( s ) and organophosphorus compound(s)) may be particularly suitable for some applications. Cypermethrin is an example of a liquid which can function both as the oil and as a water-insoluble oil-soluble substance.

Therefore, in preferred embodiments of the invention, either the oil is a pesticide or the formulation comprises a pesticide dissolved in the oil. When the oil is a pesticide the formulation may be free of an oily solvent for the pesticide^ It is preferred that the cosurfactant has an HLB of less than 12. The pesticide may be a pyrethroid or any other insecticide, acaricide, herbicide or fungicide.

Pesticidal formulations in accordance with the invention can show enhanced activity not only compared to conventional (macroemulsion) formulations but also when compared with other microemulsion formulations, because of the presence of the wetting agent.

With water-in-oil microemulsions, micellar solutions and molecular solutions, it is generally possible to get a higher concentration of the substance of interest (for example deltamethrin or another synthetic pyrethroid or other pesticide) . However, o/w formulations may give a perfectly adequate concentration for end use or even for concentrates for dilution before use.

In principle, formulations in accordance with the invention can be made very simply. Therefore, according to a second aspect of the present invention, a formulation in accordance with the first or second aspect is prepared by mixing the ingredients. Depending on the thermodynamic favourability of the system, the ingredients will tend to form a microemulsion, micellar solution or molecular solution. In practice, however, kinetic considerations may dictate that some agitation is preferably used to assist the mixing. Agitation may be by magnetic or mechanical means or in some cases ultrasonic.

Once a desired and correctly balanced formulation has been arrived at, it will be found that the order of addition of the ingredients is not normally critical. However, for w/o microemulsions, micellar solutions and molecular solutions, it is preferred to add the ingredients to a vessel in the following order:

1. Add the oil to a vessel

2. Add any additives such as solid deltamethrin dissolved in further oil

3 . Add the surfactant , wetting agent and additional cosurfactant, if any, and dissolve them in the oil

4. Add water to give a clear formulation (eg a w/o microemulsion)

Although the above procedure may be found to be suitable for o/w microemulsions, there is a possibility that upon addition of the water, the system could move into the yiscoelastic gel region (which can be almost solid) and this could cause practical mixing problems. Consequently, the following procedure is preferred for the preparation of o/w microemulsions:

1. The oil is added to the vessel

2. Additives (such as solid deltamethrin) is dissolved in the oil

3. The surfactant is added and dissolved in the oil

4. Water is added and agitated to give a homogeneous macroemulsion

5. The wetting agent and additional cosurfactant, if any, is added and the system is agitated to produce a clear o/w microemulsion.

Routine modifications, such as the ^"application of heat or altering the degree of agitation can be made to these basic processes to suit the system in use.

It has been stated above that the preferred pyrethroid or other pesticidal microemulsion formulations have been found to have enhanced pesticidal activity. Therefore, according to a third aspect of the present invention there is provided a method of controlling pests, the method comprising applying a pesticide in a formulation whose average particle size is at most 200 nm and which comprises water, a pesticidal oil, a surfactant and a cosurfactant comprising a polysiloxane based copolymer. The formulation may be a microemulsion, a micellar solution or a molecular solution; the microemulsion may be an o/w or a w/o formulation. Oil-in-water microemulsion formulations are preferred. Pyrethroid or other pesticides formulated in this way can be used to control pests in an agricultural environment.

Applications of such pyrethroid or other (for example, organophosphorus) pesticide formulations are not confined to agriculture: public health formulations may be commercially important. Agricultural formulations in accordance with the invention may have a further advantage in that they use less potentially harmful solvent (such as xylene) per dose than certain conventional formulations, thereby posing less of a threat to the crop being treated, the handler and to the environment in general.

The concentration of the substance of interest (for example, deltamethrin) in the formulations of the invention may range from as little as 0.1 ppm, 0.01 g/1 or 0.1 g/1 up to 100 or 200 g/1 or more. High concentrations of pesticide may range from 10 to 300 g/1, for example 25 to 200 g/1, such as 25 or 100 g/1. For agricultural use of deltamethrin or another pyrethroid pesticide 10 to 50 g/1 or 100 g/1 final concentration may be found to be suitable. For public health or stored grain use, a formulation containing from 0.1 ppm or 0.05 g/1 to 5 g/1, for example 0.1 g/1 to 1 g/1 may be found to be acceptable.

The invention will be illustrated by the following examples. . Example 1

A f ormul ation was prepared from the fol l owing ingredients :

Xylene/cypermethrin ' ¹' 400ml/l TEGOPLANT WT 10 ^{( 2 )} 20 g/1 PLURIOL PE 6100 (³ ) 130 g/1 NANSA SSA ^ ⁴ ) 130 g/1 Water _. 345 g/1

Note : (1) 100 g cypermethrin (technical) made up to 400 ml with xylene.

(2) Trade mark for polysiloxane-based copolymer (wetting agent) .

(3) Trade mark for ethylene oxide propylene oxide block copolymer (additional cosurfactant) .

(4) Trade mark for dodecyl benzene sulphonic acid - predominantly straight chain (anionic surfactant) .

20 g cypermethrin were made up to 80 ml with xylene, and the resulting mixture was placed in a 250 ml beaker. The TEGOPLANT WT 10 and PLURIOL PE 6100 cosurfactants and NANSA SSA surfactant were then slowly dissolved into this and the appropriate amount of water (69.0 is) added slowly from a burette while stirring. The formulation was confirmed to be a micellar solution by conductivity measurements. The average particle size of a 1/400 dilution was measured by a MALVERN AUTOSIZER 2c laser particle sizer to be 40.2 + 6.9 nm, showing the diluted formulation to be a microemulsion.

Example 2

A formulation was prepared from the following ingredients:

Xylene/deltamethrin^¹) 400 ml/1 TEGOPLANT WT 25⁽²⁾ 20 g/1 PLURIOL PE 6100(³) 130 g/1 NANSA SSA^⁴) 130 g/1 Water 345 g/1

Note: (1) 25 g/1 deltamethrin (technical) made up to 400 ml with xylene .

(2) Trade mark for polysiloxan_^e-based copolymer (wetting agent) .

5g deltamethrin were made up to 80 ml with xylene, and the resulting mixture was placed in a 250 ml beaker. The TEGOPLANT WT 10 and PLURIOL PE 6100 cosurfactants and NANSA SSA surfactant were then slowly dissolved into this and the appropriate amount of water (69.0 mis) added slowly from a burette while stirring. The formulation was confirmed to be a micellar solution by conductivity measurements. The average particle size of a 1/400 dilution was measured by a MALVERN AUTOSIZER 2c laser particle sizer to be about 40 nm, showing the diluted formulation to be a microemulsion.

Comparison Example 1

A formulation was prepared as in Example 1, except that the TEGOPLANT WT 10 wetting agent was omitted.

Biological Example A

The activity of the formulation of Example 1, diluted appropriately with water, was tested against Rl Mvzus persicae by spraying the aphids direct from a Potter tower. As a comparison a standard AMBUSH C e ulsifiable concentrate, also diluted with water. (The word AMBUSH is a trade mark for a conventional cypermethrin formulation.)

Percentage mortalities from about 30 aphids were derived; all data were corrected for control mortality using Abbott's formula. Results are shown in Tables la, lb and lc below.

Table la - Percentage mortalities at 24 hours:

Cypermethrin (ppm) 100 50 25 12.5 6.25 3.125

100 100 65 35 15 9

Table lb - Percentage mortalities at 48 hours:

Cypermethrin (ppm) 100 50 25 12.5 6.25 3.125

Example 1 100 100 100 100 84 64 AMBUSH 100 100 - 36 41

Table lc - Percentage mortalities at 72 hours:

Cypermethrin (ppm) 100 50 25 12.5 6.25 3.125

Example 1 100 100 100 100 97 67 AMBUSH 100 100 - - 36 41

The results show that greater mortality resulted from a composition in accordance with the invention than from a conventional emulsifiable concentrate. The results also show that the composition in accordance with the invention had greater persistence than the conventional formulation as the pesticidal effect lasted beyond 48 hours.

Biological Example B

Adult black vine weevils, Otioryhnchus sulcatus. were collected from a heavily infested commercial black currant plantation near Canterbury, Kent, England, and placed in 14cm plastic petri dishes in batches of 10 individuals. An aqueous solution of each of the cypermethrin formulations to be tested (see Table 2) was sprayed directly onto three replicate batches of adult weevils (each batch receiving one treatment only) using the Potter tower 3.0ml of spray solution was applied to each dish. The weevils were then transferred to clean petri dishes and supplied with a strawberry leaf for food. After 24 hours and 7 days each individual weevil in each dish was examined and scored into one of three categories: 'healthy' apparently unaffected by insecticide; 'weak' immobile, lying or dorsum but still moving at least when prodded; 'dead' - immobile and unresponsive.

The numbers dead at the 7 day assessment were analysed by fitting generalised linear models with extra-binomial errors. This method of analysis provided approximate standard errors for the average percentage killed per treatment. The other data could not be validly analysed. Percentage mortalities and approximate standard errors are given in Table 2.

Table 2 - Mean percentage mortality of vine weevil adults 7 days after treatment.

Cypermethrin Product Concentration Mortality Approx (g ai/hl) (%) S.E. (%)

Untreated Controls

Water - 3 4

Unsprayed - 10 6 The formulation of Example 1 is significantly more active than the conventional AMBUSH formulation at a comparable concentration of active ingredient. Further, the formulation of Example 1 is more active than the formulation of Comparative Example l, which although it is a microemulsion formulation does not contain a wetting agent.

Claims

1. A water-miscible formulation whose average particle size is at most 200 nm, the formulation comprising water, oil, a surfactant and a cosurfactant comprising a wetting agent.

2. A formulation as claimed in claim 1, wherein the oil comprises a pesticide.

3. A formulation as claimed in claim 2, wherein the pesticide is an insecticide and/or acaricide.

4. A formulation as claimed in claim 2 or 3 , wherein the oil consists substantially only of a pesticide.

5. A formulation as claimed in claim 1, wherein the wetting agent comprises a polysiloxane-based copolymer.

6. A formulation as claimed in claim 5, wherein the polysiloxane-based copolymer comprises a polysiloxane- polyether-copolymer.

7. A formulation as claimed in claim 6, wherein the polysiloxane-polyether-copoly er comprises material substantially the same as that sold under the trade mark TEGOPLANT WT 10.

8. A formulation as claimed in claim 6, wherein the polysiloxane-polyether copolymer comprises material substantially the same as that sold under the trade mark TEGOPLANT WT 25.

9. A formulation as claimed in claim 1, wherein the cosurfactant comprises an additional cosurfactant, as well as the wetting agent.

10. A formulation as claimed in claim 1, wherein the additional cosurfactant has an HLB of less than 12.

11. A formulation as claimed in claim 1, wherein the surfactant comprises an anionic surfactant.

12. A formulation as claimed in claim 10, wherein the additional cosurfactant comprises a nonionic surfactant or an aliphatic alcohol.

13. A formulation as claimed in claim 1,. which comprises on a w/v basis: oil (20 to 50%) , surfactant (1 to 20%) , cosurfactant comprising a wetting agent (1 to 20%) and water (20 to 70%) , provided that the total number of percentage parts of the ingredients cannot exceed 100.

14. A formulation as claimed in claim 1, which comprises on a w/v basis: oil (1 to 20%) , surfactant (1 to 10%) , cosurfactant comprising a wetting agent (1 to 10%) and water (40 to 95%) , provided that the total number of percentage parts of the ingredients cannot exceed 100.

15. A process for the preparation of a water-miscible formulation whose average particle size is at most 200 nm, the formulation comprising water, oil, a surfactant and a cosurfactant comprising a wetting agent, the process comprising admixing the ingredients.

16. A method of controlling pests, the method comprising treating the pests, or a locus for the pests, with a water-miscible formulation whose average particle size is at most 200nm, the formulation comprising water, oil comprising a pesticide, a surfactant and a cosurfactant comprising a wetting agent.

17. A method as claimed in claim 16, wherein the oil includes a dissolved pesticide.

18. A method as claimed in claim 16, wherein the oil consists substantially only of a pesticide.