Patent Description:
Paraquat is a non-selective, non-residual contact herbicide used to control broad-leaved weeds and grasses and inhibits the growth of plant cell membranes. Paraquat is commonly used in the form of the paraquat dichloride salt. <CIT>, <CIT>, and <NPL>, all disclose paraquat-containing herbicidal formulations.

Butafenacil is a pyrimidindione herbicide used to control broad-leaved weeds and grasses through the inhibition of the protoporphrinogen mode of action, and is described for example in <CIT>. Butafenacil has been introduced as a complementary component in the products Logran® B-Power™ (a premix of triasulfuron and butafenacil), for the pre-emergent control of grass and broadleaf weeds in wheat, and Touchdown® BPower™ (a premix of glyphosate and butafenacil), for the knockdown control of grass and broadleaf weeds prior to the sowing of cereals crops.

S-metolachlor is a chloroacetanilide herbicide used to control broad-leaved weeds and grasses through the inhibition of the gibberellin pathway, and is described for example in The Pesticide Manual, sixteenth edition, entry <NUM>, page <NUM>.

It would be preferable to extend the use of butafenacil and S-metolachlor as complementary components to formulations comprising paraquat. However, as paraquat is a strong electrolyte it has a high ionic strength which often leads to problems during formulation and especially complications concerning surfactant compatibility.

A variety of emulsifier systems have been proposed and used in the past in order to overcome the difficulties of formulating oils in paraquat solutions. Common emulsifier systems for oil in water (EW) formulations do not work with paraquat, for example phosphate esters, fatty alcohol ethoxylate or propoxylates, calcium dodecyl benzene sulfonate, blockcopolymers, polymeric amphoteric and non-ionic could not be combined with paraquat and another oil to deliver a stable emulsion.

We have now unexpectedly and surprisingly achieved a stable emulsion in a paraquat solution through the use of an emulsifier package comprising a polyvinylalcohol-acetate copolymer, a sorbitan ester surfactant, and a polymeric ethoxylated sorbitan ester surfactant.

Emulsifier compositions containing polyvinylalcohol-acetate copolymers, a sorbitan ester and a polymeric ethoxylated sorbitan ester are already known. However, applying said emulsifier composition to a highly charged species such as paraquat is unknown.

One of the challenges faced when formulating pesticidal compositions is the compatibility of active ingredients with additional formulation ingredients, such as surfactants. This is especially a challenge when the active ingredient is highly charged. When the emulsifier polyvinylalcohol was formulated as an oil in water emulsion with the charged active ingredients glyphosate and gluphosinate, it was found that the polyvinylalcohol precipitates out of solution. Therefore, it was highly surprising that when polyvinylalcohol was formulated with paraquat, that the polyvinylalcohol readily dissolves in a paraquat dichloride solution.

Such a formulation approach provides both paraquat and an additional pesticidal active ingredient, along with the emulsifier package in a single formulation, which may be applied either directly to a target or may be diluted in a conventional spray tank before being sprayed onto a target. When applied via a spray tank, other conventional adjuvants, may be added to the spray tank prior to spraying. Examples of commercially available tank mix adjuvants include the mineral oil based Nimbus™ and non-ionic wetting agent Activator <NUM>™.

In a first embodiment of the invention there is provided a pesticidal emulsion comprising:.

wherein components (d) and (e) are located at the interface between components (a) and (b).

A disadvantage of this type of emulsion is that it can be susceptible to Ostwald ripening, whereby diffusion through the continuous phase and between the droplets of the dispersed phase can lead to an increase in the median droplet diameter over time. This increase in droplet diameter increases the rate of separation of the dispersed phase driven by density differences. Ultimately this ripening can render the product unfit for use because, for example, it requires re-homogenisation, or because the droplets are too coarse to remain dispersed in the spray tank prior to application to the target, or because the droplets are too large to give an even distribution of the active ingredient when applied to the target.

In a second embodiment of the invention there is provided a use of the pesticidal emulsion in the control of undesired vegetation.

In a third embodiment of the invention there is provided a pesticidal emulsion according to the first embodiment wherein one of the formulation ingredients also behaves as an Ostwald ripening inhibitor.

Paraquat may be present at a concentration of from <NUM> to <NUM>/l, preferably from <NUM> to <NUM>/l, more preferably from <NUM> to <NUM>/l, even more preferably from <NUM> to <NUM>/l. Preferably, when component (c) is butafenacil, paraquat may be present at a concentration of <NUM>/l. Preferably, when component (c) is S-metolachlor, paraquat may be present at a concentration of <NUM>/l.

When component (c) is butafenacil, component (c) may be present at a concentration of from <NUM> to <NUM>/l, preferably from <NUM> to <NUM>/l, more preferably from <NUM> to <NUM>/l, and more preferably still from <NUM> to <NUM>/l. Most preferably component (c) may be present at a concentration of <NUM>/l.

When component (c) is S-metolachlor, component (c) may be present at a concentration of from <NUM> to <NUM>/l, preferably from <NUM> to <NUM>/l, more preferably from <NUM> to <NUM>/l. Most preferably component (c) may be present at a concentration of <NUM>/l.

When component (c) is butafenacil, the weight ratio of paraquat to component (c) is preferably from <NUM>:<NUM> to <NUM>:<NUM>, more preferably from <NUM>:<NUM> to <NUM>:<NUM>, more preferably still from <NUM>:<NUM> to <NUM>:<NUM>, and most preferably where component (c) is butafenacil, the weight ratio of paraquat to component (c) is <NUM>:<NUM>.

When component (c) is S-metolachlor, the weight ratio of paraquat to component (c) is preferably from <NUM>:<NUM> to <NUM>:<NUM>, more preferably from <NUM>:<NUM> to <NUM>:<NUM>, and most preferably where component (c) is S-metolachlor, the weight ratio of paraquat to component (c) is <NUM>:<NUM>.

The polyvinylalcohol-acetate copolymer may be present at a concentration of from <NUM> to <NUM>/l.

When component (c) is butafenacil, the polyvinylalcohol-acetate copolymer, may be present at a concentration of from <NUM> to <NUM>/l, preferably <NUM> to <NUM>/l, more preferably from <NUM> to <NUM>/l, even more preferably from <NUM> to <NUM>/l, and more preferably still from <NUM> to <NUM>/l. Most preferably, when component (c) is butafenacil, the polyvinylalcohol-acetate copolymer may be present at a concentration of <NUM>/l.

When component (c) is S-metolachlor, the polyvinylalcohol-acetate copolymer, may be present at a concentration of from <NUM> to <NUM>/l, preferably from <NUM> to <NUM>/l, more preferably from <NUM> to <NUM>/l. Most preferably, when component (c) is S-metolachlor, the polyvinylalcohol-acetate copolymer may be present at a concentration of from <NUM> to <NUM>/l.

In a preferred embodiment, the polyvinylalcohol-acetate copolymer has a molecular weight of between <NUM>,<NUM> to <NUM>,<NUM>, preferably between <NUM>,<NUM> to <NUM>,<NUM>, and more preferably between <NUM>,<NUM> to <NUM>,<NUM>.

In one set of embodiments, the polyvinylalcohol-acetate copolymer has a molecular weight of between <NUM>,<NUM> to <NUM>,<NUM>, preferably between <NUM>,<NUM> to <NUM>,<NUM>, and more preferably between <NUM>,<NUM> and <NUM>,<NUM>.

In another set of embodiments, the polyvinylalcohol-acetate copolymer has a molecular weight of between <NUM>,<NUM> and <NUM>,<NUM>, preferably between <NUM>,<NUM> and <NUM>,<NUM>, and more preferably between <NUM>,<NUM> and <NUM>,<NUM>.

In a particularly preferred embodiment, the polyvinylalcohol-acetate copolymer is Mowiol® <NUM>-<NUM>, a water-soluble hydrocolloid mucoadhesive, which comprises <NUM>% polyvinylalcohol, e.g. available from Sigma-Aldrich, UK.

In a second particularly preferred embodiment, the polyvinylalcohol-acetate copolymer is SELVOL™ <NUM>, e.g. available from Sekisui, USA.

One of the further advantages of utilising a polyvinylalcohol-acetate copolymer having the above molecular weights, is that the copolymer also acts as a formulation thickener, and therefore it is unnecessary to add a conventional thickener such as xanthan to the formulation. This is of particular relevance when formulating paraquat as conventional thickeners such as xanthan disrupt the paraquat dilution.

The sorbitan ester (d) may be present in the form of a monolaurate ester, a monopalmitate ester, a monostearate ester or a monooleate ester. Preferably, (d) is present as a monolaurate ester or a monopalmitate ester. When component (c) is butafenacil, the sorbitan ester (d) is present as a monopalmitate ester.

Preferably, when component (c) is S-metolachlor, the sorbitan ester (d) is present as a monolaurate ester.

In one preferred embodiment, the sorbitan ester (d) is selected from SPAN™ <NUM> and SPAN™ <NUM>, e.g. available from Croda, UK. Preferably, when component (c) is butafenacil, the sorbitan ester (d) is SPAN™ <NUM>. Preferably, when component (c) is S-metolachlor, the sorbitan ester (d) is SPAN™ <NUM>.

The polymeric ethoxylated sorbitan ester (e) may be present in the form of a monolaurate ester, a monopalmitate ester, a monostearate ester or a monooleate ester. Preferably, (e) is present as a monolaurate ester or a monopalmitate ester. When component (c) is butafenacil, the polymeric ethoxylated sorbitan ester (e) is present as a monopalmitate ester. Preferably, when component (c) is S-metolachlor, polymeric ethoxylated sorbitan ester (e) is present as a monolaurate ester.

The polymeric ethoxylated sorbitan ester (e) may contain a mean value of from <NUM> to <NUM> ethylene oxide groups, preferably from <NUM> to <NUM> ethylene oxide groups. In particular the polymeric ethoxylated sorbitan ester (e) may contain a mean value of <NUM>, <NUM>, <NUM>, <NUM> or <NUM> ethylene oxide groups. Preferably, when component (c) is butafenacil, the polymeric ethoxylated sorbitan ester (e) contains a mean value of <NUM> ethylene oxide groups. Preferably, when component (c) is S-metolachlor, the polymeric ethoxylated sorbitan ester (e) contains a mean value of <NUM> ethylene oxide groups.

In one preferred embodiment, the polymeric ethoxylated sorbitan ester (e) is selected from TWEEN™ <NUM>, TWEEN™ <NUM> and TWEEN™ <NUM>, e.g. available from Croda, UK. Preferably, when component (c) is butafenacil, the polymeric ethoxylated sorbitan ester (e) is TWEEN™ <NUM>. Preferably, when component (c) is S-metolachlor, the polymeric ethoxylated sorbitan ester (e) is TWEEN™ <NUM>.

The dispersed oil phase (b) comprises a heavy aromatic hydrocarbon solvent. The heavy aromatic hydrocarbon solvent is typically a mixture of heavy aromatic hydrocarbons. Preferably, the heavy aromatic hydrocarbon solvent comprises a mixture of naphthalenes substituted by alkyl groups, wherein said alkyl groups contain from <NUM> to <NUM> carbon atoms in total.

More preferably, the naphthalenes substituted by alkyl groups may be present from <NUM>% to <NUM>% by weight of the heavy aromatic hydrocarbon solvent, preferably from <NUM>% to <NUM>%, and more preferably from <NUM>% to <NUM>%, by weight of the heavy aromatic hydrocarbon solvent. In one embodiment, the heavy aromatic hydrocarbon solvent has a low content of naphthalene (i.e. unsubstituted naphthalene); and preferably contains from <NUM>% to <NUM>% or from <NUM>% to <NUM>% of naphthalene by weight of the heavy aromatic hydrocarbon solvent, more preferably from <NUM> % to <NUM>% of naphthalene, and even more preferably from <NUM> % to <NUM>% of naphthalene, by weight of the heavy aromatic hydrocarbon solvent; this is typically called a "naphthalene-depleted" heavy aromatic hydrocarbon solvent.

In one preferred embodiment, the heavy aromatic hydrocarbon solvent comprises Solvesso™<NUM> ND, e.g. available from Exxon, Europe. Solvesso™<NUM> ND typically has a low percentage (e.g. ca. <NUM>%) of (unsubstituted) naphthalene (ND = naphthalene depleted), and comprises also varying percentages of other (e.g. higher) aromatic hydrocarbons, and in particular typically comprises naphthalenes substituted by alkyl groups, wherein said alkyl groups contain from <NUM> to <NUM> carbon atoms in total.

In an alternative preferred embodiment, the heavy aromatic hydrocarbon solvent comprises Aromatic™<NUM> ND, e.g. available from Exxon, USA. Aromatic™<NUM> ND typically has a low percentage (e.g. ca. <NUM>% to <NUM>%) of (unsubstituted) naphthalene (ND = naphthalene depleted), and comprises also varying percentages of other (e.g. higher) aromatic hydrocarbons, and in particular typically comprises naphthalenes substituted by alkyl groups, wherein said alkyl groups contain from <NUM> to <NUM> carbon atoms in total.

The dispersed oil phase (b) may further comprise a paraffinic solvent or an alcohol solvent. The paraffinic solvent is typically an isoparaffinic solvent. In one preferred embodiment, the paraffinic solvent is ISOPAR™ M, e.g. available from Exxon, Europe.

The paraffinic solvent may be present at a concentration of <NUM> to <NUM>/l, preferably from <NUM> to <NUM>/l, more preferably from <NUM> to <NUM>/l, and more preferably still from <NUM> to <NUM>/l. In a particularly preferable embodiment, the paraffinic solvent may be present at a concentration of <NUM>/l.

The alcohol solvent is preferably cis-<NUM>-hexenol which is also used as an alerting agent in the formulation. The alcohol solvent may be present at a concentration of <NUM> to <NUM>/l, preferably from <NUM> to <NUM>/l, more preferably from <NUM> to <NUM>/l, and more preferably still from <NUM> to <NUM>/l.

As used herein, the term "alerting agent" refers to an olfactory or stanching agent which is used to alert the user that the substance should not be ingested.

The pesticidal emulsion of the present invention may also comprise one or more antifoam emulsions, such as a silicone antifoam emulsion, for example SAG <NUM>.

The pesticidal emulsion of the present invention may further comprise a dye, such as a triarylmethane dye.

The pesticidal emulsion of the present invention may also comprise further alerting or stanching agents, such as pyridine or pyrimidine compounds.

When component (c) is butafenacil, the dispersed oil phase is present as droplets or particles, and said particles have a median diameter (Dv(<NUM>)) of <NUM> or less, preferably <NUM> or less, and even more preferably <NUM> or less, as measured by light scattering.

When component (c) is S-metolachlor, the dispersed oil phase is present as droplets or particles, and said particles have a median diameter (Dv(<NUM>)) of <NUM> or less, preferably <NUM> or less, and even more preferably <NUM> or less, as measured by light scattering.

The parameter Dv(<NUM>) signifies the point in the size distribution, up to and including which, <NUM> % of the total volume of material in the sample is 'contained', i.e. wherein <NUM> % of the sample's mass is comprised of particles with a diameter less than the value of Dv.

Ostwald ripening inhibitors, for use in the present invention, are soluble or miscible in the dispersed oil phase, or themselves serve as the dispersed oil phase containing the at least one substantially water-insoluble pesticidally active ingredient. Suitable Ostwald ripening inhibitors include Ostwald ripening inhibitor solvents such as liquid hydrocarbon solvents. A particularly preferred Ostwald ripening inhibitor of the present invention is ISOPAR™ M.

Preferably the total agrochemical concentration in the composition is from <NUM>% to <NUM>% by weight, more preferably from <NUM>% to <NUM>%. When component (c) is butafenacil, the total agrochemical concentration in the composition is preferably from <NUM>% to <NUM> % by weight, more preferably from <NUM>% to <NUM>%. When component (c) is S-metolachlor, the total agrochemical concentration in the composition is preferably from <NUM>% to <NUM>% by weight, more preferably from <NUM>% to <NUM>% by weight.

The Examples which follow service to illustrate the invention. It will be appreciated that modification of detail may be made without departing from the scope of the invention.

Examples of formulations prepared according to Formulation Example <NUM> are shown in Table <NUM> below.

Table <NUM> shows the formulations where the complete emulsifier package (Mowiol® <NUM>-<NUM>/ SPAN™ <NUM>/ TWEEN™ <NUM>) was not used. In these cases the emulsion concentrates did not form.

For formulations comprising paraquat and butafenacil, particle size, and physical stability in terms of phase separation were studied over a wide range of temperatures. The results of which are shown in Table <NUM>, below. Crystal growth of butafenacil was also studied as butafenacil crystal growth has been observed in other mixtures of paraquat and butafenacil, due to the recrystallization of butafenacil in aqueous media. The results clearly show that the formulations of this invention do not promote butafenacil crystal growth.

The viscosity of the formulations of the invention were also assessed. Any formulation that contains more than <NUM>% w/w aromatic hydrocarbon must have a viscosity greater than <NUM><NUM>/sec at <NUM> (OECD <NUM> Test Method).

An example of the formulation prepared according to Formulation Example <NUM> is shown in Table <NUM> below.

The following Tables <NUM> to <NUM> provide further example compositions of the ranges listed above in Table <NUM>.

Example formulations comprising paraquat and S-metolachlor, were tested over a wide range of temperature and time periods for changes in serum, pH, viscosity and particle size. The results of this study are shown in Table <NUM>, below.

Table <NUM> shows that significant separation (recorded in Table <NUM> under the title 'Serum') of the formulation was not seen. For some of the samples, especially at higher temperatures, a creaming layer was seen, but this readily mixed back into the formulation.

Table <NUM> details the maximum ratio of polyvinylalcohol-acetate copolymer (Mowiol® <NUM>-<NUM>) to glufosinate and water at which the polyvinylalcohol-acetate copolymer does not precipitate. Above these ratios the polyvinylalcohol-acetate copolymer does precipitate, and glufosinate cannot be formulated as an oil-in-water emulsion (EW) at a commercially acceptable concentration using the Mowiol® <NUM>-<NUM>/SPAN™ <NUM> and TWEEN™ <NUM> system.

Table <NUM> details the maximum ratio of polyvinylalcohol-acetate copolymer (Mowiol® <NUM>-<NUM>) to glyphosate and water at which the polyvinylalcohol-acetate copolymer does not precipitate. Above these ratios the polyvinylalcohol-acetate copolymer does precipitate, and glyphosate cannot be formulated as an EW at a commercially acceptable concentration using the Mowiol® <NUM>-<NUM>/SPAN™ <NUM> and TWEEN™ <NUM> system.

Claim 1:
A pesticidal emulsion comprising:
(a) an aqueous continuous phase comprising paraquat at a concentration of from <NUM> to <NUM>/l, and at least one polyvinylalcohol-acetate copolymer;
(b) a dispersed oil phase comprising a heavy aromatic hydrocarbon solvent;
(c) at least one pesticidal active ingredient selected from butafenacil and S-metalochlor dissolved in the dispersed oil phase;
(d) a sorbitan ester surfactant; and
(e) a polymeric ethoxylated sorbitan ester surfactant;
wherein components (d) and (e) are located at the interface between components (a) and (b).