Emulsifiable concentrate formulation

This application is the National Phase of International Application PCT/AU2013/000164 filed Feb. 25, 2013 which designated the U.S. and which claims priority to Australia Application Serial No. 2012900731 filed Feb. 27, 2012. The noted applications are incorporated herein by reference.

The invention relates to an emulsifiable concentrate (EC) formulation of agrochemical active ingredients utilising an improved solvent system comprising benzyl acetate as a primary solvent in combination with other co-solvents. More preferably, the improved solvent system provides a substantially storage-stable and dilution-stable emulsifiable concentrate (EC) formulation.

In the art of formulating agrochemicals, it is often necessary to dissolve the agrochemical active ingredient in a solvent and then dilute it in a larger volume of water in order for it to be broadcast in the form of a fine spray. In still other cases, it is necessary to dilute the active ingredient in a solution and apply it to a seed or other solid carrier. While some active ingredients, which are usually in the form of a salt, can be simply dissolved and then diluted in water, the majority of agrochemical active ingredients are hydrophobic and are therefore not water-soluble. In the case of active ingredients that are not water-soluble, it is normally necessary to dissolve the formulation in a water-immiscible solvent and add one or more surfactants, so that the solution will form an oil-in-water emulsion, when added to water. Such a formulation is called an Emulsifiable Concentrate (EC) formulation. Alternatively, the water-immiscible solution comprising active ingredient can be pre-emulsified in water in a concentrated form. Such a formulation is called an Emulsion-in-Water (EW) formulation. A special sub-class of EW formulations is the so-called Microemulsion (ME) formulation, where the emulsion particle size is such that the formulation does not scatter light and has a clear or translucent appearance.

Water-immiscible solvents commonly used for EC and EW formulations include, but are not limited to, aromatic hydrocarbons such as the SOLVESSO® series, paraffinic hydrocarbons such as the EXXSOL® range, ester solvents such as the EXXATE® range, all of which are manufactured by EXXONMOBIL, and ester solvents such as methyloleate. Further, solvents which are water-immiscible at high concentration include cyclic hydrocarbons, such as cyclohexanone and isophorone.

In more recent times, solvents which exhibit improved toxicity and reduced flammability profiles have been used. These include the dibasic ester solvents of long chain di-acids having from 8-16 carbon units, which are usually methyl ester derivatives, and fatty acid amide solvents, examples of which are the dimethylamide and morpholineamide derivatives of C 6 -C 16 fatty acids. Mono-alkylene carbonates such as ethylene, propylene and butylene carbonates, also find use as co-solvents.

Combinations of water-immiscible solvents with highly polar water-miscible co-solvents such as N-methyl pyrrolidinone, dimethylsulphoxide, dimethylisosorbide, monoethylene glycol, monopropylene glycol and various glycol ethers have been used in the past to achieve physical stability of the EC formulation, particularly if crystallisation of the active ingredient occurs at below ambient temperature. However, the use of such solvent combinations often leads to the problem of crystallisation in the diluted formulation.

There is a particular need for low toxicity and low flammability polar solvents, which can dissolve the more polar active ingredients, but which are not so polar as to have significant water-solubility problems resulting in crystallisation of the active ingredient upon dilution. In particular, it is desirable to be able to dissolve certain problematic agrochemical active ingredients in high concentration for use in emulsifiable concentrate formulations. High concentration ECs have significant advantages in terms of the reduced costs involved in shipping and handling. Such active ingredients include, but are not limited to, pyridine-based herbicides such as clopyralid and diflufenican; diphenylether herbicides such as oxyfluorfen; anilide herbicides such as propanil; triazole fungicides such as triadimenol; dinitroaniline herbicides such as oryzalin; carbamate insecticides such as propoxur; oxadiazine insecticides such as indoxacarb; synthetic pyrethroid insecticides such as bifenthrin; and neonicotinoid insecticides such as imidacloprid and thiocloprid.

While many of the dibasic ester and fatty amide-based solvents can dissolve some of the active ingredients in the polarity range of these solvents, there are limitations on the amount of active ingredient that can be dissolved. Further, not all of these classes of solvents have desirable toxicity profiles. In addition, significant effort and expense can be involved in the manufacture and, in particular, the purification of these solvents.

While mono-short chain alkylene carbonate solvents have an overall excellent toxicity profile and reduced flammability, their major limitation is that they are generally water-miscible upon dilution and do not fully dissolve many of the active ingredients described above.

The use of benzyl acetate as a solvent for agrochemical active ingredients is known. Japanese Patent Application No. JP 2009173569A teaches the use of benzyl acetate and butylacetoacetate in combination with a water-miscible co-solvent, 1,3-dimethyl-2-imidazolidinone and an aromatic hydrocarbon to prepare emulsion compositions of various hydrophobic agrochemical active ingredients up to 50 weight/volume %. International Patent Publication No. WO 2011/017480 teaches the use of benzyl acetate as a suitable solvent for dissolving certain active ingredients in preparation for forming microcapsule compositions.

There is, however, still a need for polar, water-miscible solvent combinations having an improved toxicity and flammability profile.

The present invention seeks to provide an improved solvent system for high concentration emulsifiable concentrate formulations that at least ameliorates certain disadvantages associated with previously known solvent systems.

According to one aspect of the present invention, there is provided an emulsifiable concentrate (EC) formulation comprising a least one agrochemical active ingredient; at least one surfactant emulsifier; optionally, a stabiliser; and a primary solvent system, wherein the solvent system comprises a combination of benzyl acetate and a sufficient amount of at least one polar, substantially water-miscible co-solvent.

The present inventors have now surprisingly found that when benzyl acetate is used in combination with other substantially water-miscible co-solvents described herein as the primary solvent system, storage-stable and dilution-stable formulations of certain problematic active ingredients can be achieved at higher loadings than could previously be achieved with alternative solvent combinations. Such a primary solvent system has an improved toxicity and flammability profile.

In particular, it has been found that when used with polar, substantially water-miscible co-solvents, for example, N-methyl pryrrolidinone and dimethylsulphoxide, benzyl acetate is able to afford formulations, which are both stable in concentrate form and stable to crystallisation upon dilution in water. That is, benzyl acetate is able to substantially overcome the problem of crystallization on dilution which is often associated with using polar, substantially water-miscible solvents as co-solvents to achieve the desired solubility in the concentrate.

The ratio of benzyl acetate to the water-miscible co-solvent is preferably in the mixing range of from 99.9:0.1 to 40:60 and more preferably, in the range of from 90:10 to 60:40.

The at least one substantially water-miscible co-solvent is preferably selected from the group of N-methylpyrrolidinone (NMP); dimethylsulphoxide (DMSO); dimethylformamide (DMF); dimethylisosorbide (DMI); isophorone; acetophenone; cyclohexanone; 1,3-dimethyl-2-imidazolidonone; ethylene, propylene and butylene carbonates; lactate esters; dimethyl and diethylcarbonates; alkylglycol ethers; glycols including propylene glycol, ethylene glycol and polyethylene glycols; alcohols including methanol; ethanol; iso-propanol; n-propanol; n-butanol; iso-butanol; and tert-butanol; or mixtures thereof.

The active ingredient is preferably selected from a pesticide or an herbicide, such as from pyridine-based herbicides; diphenylether herbicides; anilide herbicides; dinitroaniline herbicides; triazole fungicides; carbamate insecticides; oxadiazine insecticides; and neonicotinoid insecticides; or mixtures thereof.

More preferably, the active ingredient is selected from clopyralid, diflufenican, oxyfluorfen, propanil, triadimenol, oryzalin, propoxur, bifenthrin, indoxacarb, imidacloprid and thiacloprid, or mixtures thereof.

In a most preferred form, the active ingredient is diflufenican present at greater than 2% weight/volume. In a further preferred form, the formulation of the present invention further comprises a phenoxyacid ester herbicide.

In a preferred form, the at least one surfactant emulsifier used in the EC formulation is selected from the group comprising alkoxylated alcohols; alkoxylated alkylphenols; ethoxylated fatty acids; ethoxylated vegetable oils; ethoxylated tristyrylphenol; fatty acid esters of sorbitol and ethoxylated derivatives thereof; ethoxylated amines and condensates of glycerol; sulfonated alkylbenzenes in the range C 11 -C 16 and salts thereof; alkylether sulphates; alkyletherphosphates; alkylphenoletherphosphates; or combinations thereof; salts of phosphate esters of ethoxylated tristyrylphenol; salts of sulphated ethers of ethoxylated tristyrylphenol; or a catanionic system, wherein a cationic amine is present in combination with an alkylsulphonate, an alkylethersulphonate, an ether sulphate, or an ether phosphate such as an alkyletherphosphate.

The EC formulation of the present invention preferably further comprises a stabiliser, selected from butylated hydroxytoluene (BHT) and epoxidized soybean oil (ESBO). The stabiliser is preferably present in a concentration of up to 3% weight/volume and is more preferably added to the formulation once the active ingredient is dissolved in the solvent system.

Combinations of benzyl acetate with polar, substantially water-miscible co-solvents have been found to have good utility with certain crystalline active ingredients including, but not limited to, pyridine-based herbicides such as clopyralid and diflufenican; diphenylether herbicides such as oxyfluorfen; anilide herbicides such as propanil; triazole fungicides such as triadimenol; dinitroaniline herbicides such as oryzalin; carbamate insecticides such as propoxur; oxadiazine insecticides such as indoxacarb; and neonicotinoid insecticides such as imidacloprid and thiacloprid. It was been found that these active ingredients can be formulated at a sufficiently high loading to produce stable and more commercially desirable formulations, while at the same time, maintaining an acceptable toxicity profile and low flammability.

The scope of the present invention also extends to methods of formulating agrochemical active ingredients without using either further harmful or high odour solvents. In a second aspect, the present invention is directed to a method of making an emulsifiable concentrate (EC) formulation of at least one agrochemical active ingredient comprising the following steps of either firstly forming a mixture of the agrochemical active ingredient in a polar, substantially water-miscible co-solvent and then adding benzyl acetate; or alternatively forming a mixture of the agrochemical active ingredient in benzyl acetate and then adding a polar, substantially water-miscible co-solvent; or alternatively forming a mixture of the agrochemical active ingredient in a combination of benzyl acetate and a polar, substantially water-miscible co-solvent; or alternatively combining the agrochemical active ingredient, benzyl acetate and a polar, substantially water-miscible co-solvent; followed by adding at least one suitable emulsifier/s and/or at least one stabilizer/s to make an EC formulation, whereby the active ingredient is substantially soluble at 0° C. on storage in the presence of seed crystals.

The present invention is also directed to a method of making an emulsion-in-water (EW) formulation comprising at least one agrochemical active ingredient, the method comprising the following steps of either firstly, forming a mixture of the agrochemical active ingredient in a polar, substantially water-miscible co-solvent and then adding benzyl acetate; or alternatively forming a mixture of the agrochemical active ingredient in benzyl acetate and then adding a polar, substantially water-miscible co-solvent; or alternatively forming a mixture of the agrochemical active ingredient in a combination of benzyl acetate and a polar, substantially water-miscible co-solvent; or alternatively, combining the agrochemical active ingredient, benzyl acetate and a polar, substantially water-miscible co-solvent; followed by adding at least one suitable surfactant emulsifier/s and/or at least one stabilizer/s to make an emulsifiable formulation; and then contacting the composition with water, whereby the active ingredient is substantially soluble at 0° C. on storage in the presence of seed crystals.

A further advantage in using benzyl acetate solvent is that it is relatively cheap compared to many of the specialty solvents, which may be able to achieve high loading formulations of similar strength. An additional advantage is that benzyl acetate has a low odour.

Further, it has been found that benzyl acetate together with other co-solvents can usefully be emulsified together with one or more desired active ingredients using conventional surfactants known to be useful as emulsifiers for agrochemical formulations, such as EC formulations. In other words, the benzyl acetate solvent does not require any specialized emulsifier systems to achieve a stable emulsion upon dilution.

It can be seen from the physical properties of benzyl acetate, which are summarized in Table 1 below, that this solvent shows relatively low volatility and flammability.

The toxicological properties of benzyl acetate are summarized in Table 2 as follows:

Benzyl acetate shows relatively low toxicity.

In order for a solvent to be effective for an agrochemical formulation, such as an EC or EW, it is necessary for the active ingredient to be sufficiently soluble, such that no crystallisation of it is observed in the temperature range of from 0° C. to 54° C. and more preferably, in the temperature range of from −5° C. to 54° C. A number of polar, substantially water-miscible co-solvents have been found to be useful with problematic agrochemical active ingredients in achieving stability of the formulation concentrate to crystallisation. Such solvents include, but are not limited to: N-methylpyrolidinone (NMP), dimethylsulphoxide (DMSO), dimethylformamide (DMF), dimethylisosorbide (DMI), isophorone, acetophenone and cyclohexanone and various lactate ester derivatives. A major difficulty with using these types of polar solvents is that while the problem of crystallisation can be solved, the stability of the diluted formulation and resulting emulsion is inadequate regarding crystallisation of the active ingredient.

An EC formulation is preferably diluted in water at rates ranging from 0.1 to 20% w/v and more preferably, in the range of 0.5 to 5% w/v. In order for an EC formulation to be useable, it should not show crystallisation in the diluted emulsion before spraying and it must be stable for the time allowed between dilution and spraying. Typical time standards for dilution stability of active ingredients are set out by the Food and Agriculture Organization of the United Nations (FAO) and may be found in the various technical monographs prepared by them. For emulsion stability, it is expected that a formulation upon dilution would be substantially free of crystals for more than 2 hours, and more preferably, for more than 24 hours.

Accordingly, it has been surprisingly found that if a sufficient amount of benzyl actetate is used in combination with a sufficient amount of at least one polar, substantially water-miscible co-solvent such as, for example, NMP, DMI or DMSO, as the primary solvent system, sufficient solubility to certain crystalline active ingredients is afforded to maintain stability of the emulsifiable concentrate (EC) formulation, whilst also affording stability on dilution in water regarding crystallisation.

The term “primary solvent” as used herein is a solvent or combination of solvents which must be present to dissolve the active ingredient. The term “non-primary solvent” as used herein is a solvent which may optionally also be present in the solvent system, but which is not required for the purposes of dissolving the active ingredient. A non-primary solvent may incidentally be present in emulsifier blends, or as an agent, which adds additional features or characteristics, such as colour, stability or viscosity to the overall formulation. In general, if less than about 10% of a non-primary solvent is present, such a solvent will not function as part of the primary solvent system.

The polar, substantially water-miscible co-solvents useful in the present invention preferably include, but are not limited to: N-methylpyrrolidinone (NMP); dimethylsulphoxide (DMSO); dimethylformamide (DMF); dimethylisosorbide (DMI); isophorone; acetophenone; cyclohexanone; 1,3-dimethyl-2-imidazolidonone; ethylene, propylene and butylene carbonates; dimethyl and diethylcarbonates; alkylglycol ethers; glycols such as propylene glycol, ethylene glycol and polyethylene glycols; alcohols such as methanol, ethanol, iso-propanol, n-propanol, n-butanol, iso-butanol and tert-butanol. In order to be considered substantially water-miscible, the solvent should have at least substantially, preferably, complete water-solubility at the anticipated dilution rates of the EC formulation, which are typically greater than 1 part in 1,000.

The terms “agrochemical active” or “agrochemically active” as used herein are intended to also cover all the related uses of the EC formulations, such as in animal health, public health, water treatment, wood treatment, home garden and domestic vector control. The agrochemical active ingredients useful in the present invention preferably include those as listed in The Pesticide Manual of the British Crop Protection Council (14 th Edition), which are soluble in polar, substantially water-immiscible solvents.

The active ingredient/s and EC formulation's, wherein there is advantageous dilution performance in regard to a lack of crystallisation than would otherwise be observed in the absence of benzyl acetate, preferably include/s, but is/are not limited to, diflufenican alone or diflufenican in the presence of phenoxyacid ester herbicide, oxyfluorfen, propanil and/or imidacloprid.

Benzyl acetate is preferably used with the substantially water-miscible co-solvent in a ratio range of from 99.9:0.1 to 40:60, more preferably, in the range of from 90:10 to 60:40, as the primary solvent system.

The present invention may further comprise one or more substantially water-immiscible or partially water-immiscible co-solvent/s as a non-primary solvent, so long as such a solvent is not present in sufficient quantity to re-induce crystallisation of the active ingredient upon dilution in water or storage. Typically, the water-immiscible co-solvent is present at no more than 10% w/v in the total formulation used.

The agrochemical formulations of the present invention are preferably applied to plant leaves as foliar sprays, or to plant shoots and the surrounding soil. Such formulations may also be applied to animals, either topically, orally or as injectables. They may also be applied directly to insects, acarina, fungi, molluscs, nematodes and helminths, to wood and wood products and as a component of mixtures applied as coatings for buildings, insect protection nets and so on.

The composition of the active ingredient/s made using the primary solvent combination is preferably formulated as an emulsifiable concentrate (EC), or also as an oil-in-water emulsion (EW) made from such a concentrate. In order to make an EC formulation, other additives such as emulsifiers and stabilisers are preferably used. Such additives may add or subtract from the total solubility level of the active ingredient/s depending upon what is used. For example, surfactant emulsifiers containing a salt of dodecylbenzene sulphonate, such as the calcium salt or one or more amine salts, preferably contain additional solvents, like short chain alcohols, which enhance overall solubility. However, in other situations, the addition of emulsifiers may dilute the total level of the active ingredient in the formulation.

In order to prepare a preferred EC formulation, the active ingredient/s is/are dissolved in the benzyl acetate/substantially water-miscible co-solvent combination and surfactant emulsifiers are added in the range 3-20% w/v and the formulation made up to the required volume. Optionally, prior to making the formulation up to the required volume, further co-solvents which may be substantially water-miscible or partially water-miscible may be added. Such optional co-solvents preferably include, but are not limited to, a cyclic hydrocarbon/s such as cyclohexanone and isopherone; mono-alkylene carbonates, such as ethylene, propylene and butylene carbonates; or dibasic esters.

Emulsifiers for the EC formulations preferably include, but are not limited to, non-ionic surfactants, such as alkoxylated alcohols and alkoxylated alkylphenols; ethoxylated fatty acids; ethoxylated vegetable oils such as ethoxylated castor oil; ethoxylated tristyrylphenol; fatty acid esters of sorbitol and ethoxylated derivatives thereof; ethoxylated amines, and condensates of glycerol. Anionic surfactants such as salts of sulphonated dodecylbenzene and other alkylbenzenes in the range C 11 -C 16 and salts thereof; alkylether sulphates; and ether phosphates including alkyletherphosphates; alkylphenoletherphosphates; or combinations thereof; salts of phosphate esters of ethoxylated tristyrylphenol and salts of sulphated ethers of ethoxylated tristyrylphenol, can be used as emulsifiers. Catanionic systems, where a cationic amine is present in combination with an alkylsulphonate, an alkylethersulphonate, an ether sulphate or an ether phosphate such as alkyletherphosphate, can also be useful.

The emulsifiers for EC formulations can be selected from the group of castor oil ethoxylates, in particular TERMUL® 1284 emulsifier; alkoxylated alcohols, in particular TERMUL® 5459 emulsifier; alkoxylated alkylphenols, in particular TERMUL® 200 emulsifier; ethoxylated amines, in particular TERWET® 3784 and TERIC® 16M15 emulsifiers; ethoxylated tristyrylphenol, in particular TERMUL® 3150 emulsifier; alcohol ethoxylates in particular TERIC® 12A7, 13A9 and 17A2 emulsifiers; fatty acid ethoxylates such as TERIC® OF6 emulsifier; sorbitan ester ethoxylates, such as ECOTERIC® T85 emulsifier; a sulphosuccinate, such as TERMUL® 3665 emulsifier, amine and calcium salts of dodecylbenzene sulphonate, such as the NANSA® EVM range of products; salts of phosphate esters of ethoxylated tristyrylphenol, in particular TERSPERSE® 2202; salts of sulphated ethers of ethoxylated Tristyrylphenol, in particular TERSPERSE® 2218; all of which are available from Huntsman Corporation.

The EC formulation should, upon dilution, give a stable emulsion free of crystallisation for a sufficient time period, preferably at least two hours, to allow convenient use. Such emulsion stability is usually determined visually by measuring the amount of cream or sediment which forms in a diluted solution of the active ingredient after the required time period. The tests required to determine the internationally acceptable standards for stability of EC formulations may be found in the Handbooks as provided by the Collaborative International Pesticides Analytical Council (CIPAC). A typical test method used would be CIPAC MT36.3. The internationally acceptable standard of emulsion stability, as determined by the CIPAC methods, for various active ingredients are provided by the Food and Agriculture Organization of the United Nations (FAO) and may be found in the various technical monographs prepared by them.

The use of benzyl acetate together with substantially water-miscible co-solvents in EC formulations of the present invention is demonstrated with reference to the following non-limiting Examples.

Cold Storage Stability

Example formulations were seeded with at least one crystal of the active ingredient being investigated and stored at 0° C. for 7 days as per the cold storage stability testing methodology outlined in CIPAC MT39.1 (CIPAC Volume F, p128). On completion of the 7 day storage, the formulations were assessed for visible signs of crystal growth.

Accelerated Storage Stability

Example formulations were stored at 54° C. for 14 days as per the accelerated storage stability testing methodology outlined in CIPAC MT46.1.3 (CIPAC Volume F, p150). Following 14 days storage, the formulations were assessed for stability, paying particular note to sedimentation or separation.

Emulsion Stability Test

Example formulations were evaluated according to CIPAC MT36.1.1 (CIPAC volume F, p108) at ambient temperature. The volume percent of cream and the presence or otherwise of crystals after 0.5, 1, 2, and 24 hours was observed and recorded for a 5 in 100 parts dilution. The emulsion tubes were subsequently inverted 10 times and a final reassessment was made at 24.5 hours.

The purpose of the emulsion test in this instance is to look for the development of crystals upon dilution. An effort was not made to fully optimize the emulsion performance with respect to cream and oil separation.