GB2509428A - Herbicidal composition comprises clomazone microcapsules - Google Patents

Abstract

A herbicidal composition comprises microcapsules having a polymer shell and containing therein clomazone and at least one alga. Preferably the shell of the microcapsules comprises polyurea. Also claimed is a method of preparing a herbicide composition, the method comprises the steps of: providing a water immiscible phase comprising clomazone, an alga, an isocyanate and optionally an acetylene carbamide derivative (ACD) cross-linker; providing an aqueous phase comprising one or more surfactants; combining the water immiscible phase and the aqueous phase to form a dispersion of the water immiscible phase in the aqueous phase; thereby forming microcapsules of polyurea containing droplets of the water immiscible phase; and curing the microcapsules.

Description

HERBICIDAL COMPOSITION, A METHOD FOR ITS PREPARATION AND THE

USE THEREOF

The present invention relates to a herbicidal composition comprising clomazone as the active ingredient. The invention further relates to the preparation of the formulation and to its use.

Formulations of clomazone are known and are available commercially. One commercial formulation of clomazone is a solvent-based emusifiable concentrate (EC). The formulation is typically prepared by dissolving the clomazone active ingredient in an inert organic liquid solvent, together with an appropriate emulsifier system. Mixing the resulting combination with water, spontaneously forms an oil in water emulsion of the clomazone/solvent solution.

The commercially available Clomazone formulation currently available is an emulsion concentration. Such a formulation has the following disadvantages: 1. The formulation contains large amounts of organic solvents such as toluene, xylene, the presence of which is a waste of resources and contributes to serious pollution of the environment; 2. Clornazone has a relatively high vapor pressure and is volatile, leading to a low utilization in use, which leads to high dosages being applied in the field and to a high cost; 3. Clomazone is subject to drift away from the locus of application, which harms adjacent sensitive crops to which Clomazone is phytotoxic. To avoid such vapor drift hazards, the mechanical spraying of Clomazone formulations onto the ground needs to be conducted very carefully, in particular at low pressure, using large amounts of water spray, selecting conditions with little or no wind, and spraying twice per day. When applying the formulation, it is necessary to pay attention to the wind direction, wind speed. Particular care is required to avoid sensitive crops, such as fruit trees and vegetables. Aerial spraying of the current Clomazone formulations is not feasible.

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Modern agricultural practice requires improved control in the application of biologically active components to the target plants. This improved control in turn provides for a number of advantages. First, the improved control of the active ingredient allows compounds to be used that have an increased stability over extended periods of time. Further, the improved control leads to a reduction in the environmental hazard presented by the herbicidal composition. In addition, improved control leads to a decrease in the acute toxicity of the composition and allows any incompatibility between ingredients to be accommodated.

It is known that microencapsulation is a technique that offers a number of advantages in improving the control achievable in the delivery of herbicidal formulations, compared with other formulation techniques in the field of agrochemicals. Several basic processes for the preparation of microencapsulation formulations of herbicidally active compounds have been disclosed and are known in the art. In particular, known techniques for microencapsulation include coacervation, interfacial polymerization and in-situ polymerization. Most commercially available CS (microcapsule suspension) formulations are manufactured by interfacial polymerization. Examples of commercial CS formulations prepared in this manner include Chlorpyrifos CS, Lambda-cyhalothrin CS, Fluorochloridone CS, and Methylparation CS. When such formulations are dried, they form water dispersible granules containing microcapsules, with the active ingredient being contained within the microcapsules. The microcapsules act to contain the active ingredient, such that when the formulation is applied, for example as a dispersion in water, the active ingredient is released slowly from the microcapsules and its spread outside the locus of application is limited.

Clomazone, (2-[(2-chlorophenyl)methyl]-4,4-dimethyl-3-isoxazolidinone) is a well-known herbicide for controlling soybean, cotton, cassava, corn, rapeseed, sugar cane, tobacco and other crops. It is known in the art to formulate clomazone by microencapsulation. However, due to the physical properties of clomazone, for example its high volatility, determining the optimum formulation is still highly demanding.

For example, US 6,380,133 discloses a technique to encapsulate clomazone in microcapsules having a shell of a cross-linked polyurea. However, control of the release rate of clomazone is still not satisfactory.

One known method of preparing a CS formulation is by interfacial polymerization. In this method, the active ingredient is dissolved in a solvent, together with monomers and/or prepolymers. The resulting mixture is dispersed into a water phase containing one or more emulsifiers, optionally one or more protective colloids and, optionally, additional prepolymers. A capsule wall is formed around the oil droplets as a result of interfacial polymerization occurring at the oil/water interface in the presence of a catalyst or by heat.

Solvents, although generally inert in the finished formulation, are used in the microencapsulation of active ingredients to perform a number of roles, for example dissolving the active component to allow encapsulation of solid active ingredients, and adjusting the diffusion rate of the active substance through the polymeric wall, in turn aiding in controlling the release of the active ingredients from the microcapsules when the formulation has been applied. In addition, solvents may be selected, in addition to their role of dissolving the active components, to influence the emulsion quality, for example by maintaining a low viscosity during the emulsification and/or polymerization steps.

ER 1 652 433 describes a herbicidal formulation comprising an aqueous liquid composition having suspended therein a plurality of solid microcapsules, the microcapsules having a capsule wall of porous condensate polymer of at least one of a polyurea, polyamide or amide-urea copolymer. The microcapsules are formed to encapsulate clomazone as the active ingredient. Within the capsules, the clomazone is dissolved in a high boiling inert organic solvent, in particular a 1,2-benzenedicarboxylic di-(C3 -C6) branched alkyl ester.

EP 0 792 100 describes a process for preparing an encapsulated clomazone formulation. The process involves a step of providing a water immiscible liquid phase consisting of clomazone and polymethylene polyphenyl isocyanate, with or without an aromatic hydrocarbon solvent. ER 0792 100 describes the microencapsulation of clomazone by preparing a water-immiscible phase containing specified amounts of clomazone and polymethylene polyphenyl isocyanate (RMRRI), together with an aromatic solvent. The solvent is indicated to be optional in the case of formulations with high loadings of clomazone. However, the exemplified formulations generally contain a petroleum solvent in an amount of from 4 to 6% by weight.

ER 1 840 145 discloses a microencapsulated formulation of clomazone, in which the clomazone is dissolved in a solvent, in particular cyclohexanone and retained with microcapsules having a shell formed from a polymer prepared by interfacial polymerization involving the reaction of an isocyanate with an acetylene carbamide derivative.

There is a need for an improved clomazone formulation, in particular an improved microencapsulated clomazone formulation.

Surprisingly, it has now been found that the inclusion of algae as a solid carrier together with clomazone and, optionally a liquid carrier, within the microcapsules of a microencapsulated clomazone formulation provides a significant improvement in the properties of the composition, leading to greater control over the clomazone being applied in use.

Accordingly, in a first aspect, the present invention provides a composition comprising microcapsules having a polymer shell and containing therein clomazone and at least one alga.

Clornazone is the common name of 2-[(2-chlorophenymethyl]-4,4-dimethyl - 3-isoxazolidinone, a compound known to be herbicidally active and commercially available. The formulation of the present invention may comprise clomazone as the sole herbicidally active ingredient. Alternatively, one or more further active ingredients may be present in the formulation, either within the microcapsules and/or within the aqueous phase.

The composition of the present invention provides a sustained release microencapsulated formulation of clomazone containing algae as a carrier for the

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clomazone active ingredient. The composition has the advantages of reduced environmental impact, an increase in agricultural production with high efficiency, increased user friendliness, and a reduced toxicity.

It is surprising to find that the inclusion of one or more algae within the microcapsules of the present invention leads to an improved control of the release rate of the active ingredient and allows the active component to be targeted more effectively. In addition, the utilization of the active ingredient is improved, in turn reducing the amount of active component required to be used. It should also be noted that algae is also resource-rich material, which is readily available at a low cost. The process for preparing the composition is also readily applied on a commercial scale.

The formulation may comprise cloniazone in any suitable amount to provide the required level of activity, when applied to a locus for the control of plant growth.

Preferably, the formulation contains clomazone in an amount of at least 10% by weight, more preferably at least 20%, still more preferably at least 40%.

Formulations having at least 50% by weight clomazone are also envisaged in the present invention.

It has been found that clomazone adheres to algae by way of physical adsorption, in turn allowing the algae to be a solid carrier for the clomazone active ingredient within the microcapsules.

Algae are biosorbent. The cell wall of algae is formed by cellulose, which comprises micro fibrils forming a reticular structure. Algae are a source of polysaccharide, pectin, xylose, mannose, alginic acid or lichen acid. Algae are rich in resources, especially the Cyanobacteria, have a strong stress resistance, and are widely available, being widely distributed in the world, including in freshwater, marine and terrestrial environments.

Any suitable algae may be employed in the composition of the present invention, in particular alage that bind with clomazone by way of adsorbtion.

Agae may be oos&y grouped into seven categories: Euglenophyta (eugienoids), Chrysophyta (golden-brown algae), Pyrrophyta (fire algae), Chlorophyta (green algae), Fihodophyta (red algae), Paeophyta (browr. algae), and Xanthophyta (yeflow-green algae). Algae from any of the aforementioned categories may be used in the composition of the present invention. Algal species that may be used in the present invention include Amphora, Anabaena, Anikstrodesmls, Botryococcus, Chaetocoros, Ch/orella Chiorococcurn, Gyciotoila, Gylindrotheca, Duna/iella Em//lana. Eug/ena, Gloss ornas/ix. HCmatOCOCCUS. Isochrysis, Monochrysis. Mono raphidiurn, Nannochloris, Nannoch/oropsis, Na v/cu/a, Nophrochloris, Nephrosc/mis, Nitzsch/ia, Nodular/a, Nostoc, Oochromonas. Oocvstis, Osdiliartoria, Pay/ova, Phaeodactylurn, Picochioris, Platymonas, Pleurochhysis, Porhyra, Pseudoanabaena. Pyramimonas, Scenedesmus. Stichococcus, Synechococcus,, Tetraseirnis, Tha/assiosira, and Trichodesmium. Preferred algal species for use in the compositions of the present invention are Monochrysis, Chlorococcum, Synechocystis, Scenedesmus.

The alga present is present in the microcapsules in sufficient amount to act as a solid carrier for the required amount of clomazone active ingredient. The amount of the one or more algae in the compositions of the present invention can range from about 5% to about 50% by weight, preferably about 10 to about 40% by weight, most preferably about 25% by weight.

The composition of the present invention comprises microcapsules having a capsule wall formed from a polymer. The polymer of the microcapsules is porous, thereby allowing for the controlled release of the clomazone active ingredient from within the microcapsules. The rate of release of the active ingredient from the microcapsules may be controlled in known manner, for example by the appropriate selection of the polymers used to prepare the microcapsules, selection of the size of the microcapsules, the porosity of the polymer, and the presence of components within the microcapsules. Suitable polymer systems for use in the microencapsulation formulation of the present invention are known in the art. The polymer forming the wall of the microcapsules is preferably formed by interfacial polymerization. Examples of suitable polymers to form the microcapsules include porous condensate polymers of one or more of a polyurea, polyamide or amide-urea copolymer.

Polyureas are preferred polymers for the microcapsules. Polyureas may be formed by the interfacial polymerization of an isocyanate, in particular a polyfunctional isocyanate.

The polyisocyanates used as starting components according to the invention may be aliphatic or aromatic polyisocyanates. For example, aromatic polyisocyanates can be 1,3-and/or 1,4-phenylene diisocyanates, 2,4-, 2,6-tolylene dUsocyanates (TDI), crude TDI, 2,4'-, 4,4'-diphenyl methane dUsocyanate (MDI), crude MDI, 4,4'-diisocyanatebiphenyl, 3,3'-dimethyl-4-4'-diisocyanate biphenyl, 3,3'-dimethyl-4,4'diisocyanate diphenylmethane, naphthylene-1,5-diisocyanate, triphenylmethane-4,4', 4"-trUsocyanate, m-and p-isocyanate phenylsulfonyl isocyanate, polyaryl polyisocyanate (PAR), diphenylmethane-4,4'-diisocyanate (PMDI), polymethylene polyphenyl isocyanates (PMPPI) and derivatives and prepolymers of aromatic isocyanates.

Aliphatic polyisocyanates can be ethylene diisocyanate, hexamethylene dUsocyanate (HDI), tetramethylene diisocyanate, dodecamethylene dilsocyanate, 1,6,11-undecan trUsocyanate, 2,2,4-trimethylhexa -methylene diisocyanate, lysine dUsocyanate, 2,6-diisocyanate methyl caproate, bis(2-isocyanate ethyfumarate, bis(2-isocyanate ethyl)carbonate, 2-isocyanate ethyl-2,6-dUsocyanate hexanoate, trimethylhexamethylene dUsocyanate (TMDI), dimer acid dUsocyanate (DDI), isophorone diisocyanate (IPDI), dicyclohexyl dUsocyanate, dicyclohexylmethane dUsocyanate (H-MDI), cyclohexylene diisocyanate, hydrogenated tolylenedUsocyanate (HTDI), bis(2-isocyanate ethyl)-4-cyclohexene-1 2-dicarboxylate, 2,5-and/or 2,6 norbornane diisocyanate, araliphatic polyisocyanates having 8 to 15 Carbon Atoms m-and/or p-xylylene diisocyanate (XDI), alpha-, alpha-, alpha-, alpha-tetramethyl xylylene dUsocyanate (TMXDI), ethylene diisocyanate hexamethylene diisocyanate, (HDI), tetramethylene diisocyanate, dodecamethylene dUsocyanate, 1,6,11 -undecan trUsocyanate, 2,2,4-trimethylhexa methylene dUsocyanate, lysine, diisocyanate, 2,6-diisocyanate methyl caproate, bis(2- isocyanate ethyfumarate, bis(2-isocyanate ethyl)carbonate, 2-isocyanate ethyl-2,6-

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diisocyanate hexanoate, trimethyihexamethylene düsocyanate (TMDI), dimer acid dUsocyanate (DDI) and derivatives and prepolymers of aliphatic isocyanates.

The distillation residues obtained from the commercial production of isocyanates which contain isocyanate groups may also be used, optionally as solutions in one or more of the above mentioned polyisocyanates. Any mixtures of the above mentioned polyisocyanates may also be used.

Suitable isocyanates for forming the polyureas are known in the art and are commercially available, including alpha-, alpha-, alpha-, alpha-tetramethyl xylylene dUsocyanate (TMXDI), hexamethylene dUsocyanate (HDI), HDI derivative (HDI Trimer, HDI Uretdione) which are commercially available Desmodur N3600, XP241 0 and N3400, isophorone diisocyanate (IPDI), polymethylene polyphenyl isocyanates (PMPPI), methylene diphenyl isocyanate (MDI), polyaryl polyisocyanate (PAPI), and toluene diisocyanate (TDI).

As noted above, the size of the microcapsules may be selected to provide the required properties of the formulation, in particular the rate of release of the clomzone active ingredient from the microcapsules. The microcapsules may have a particle size in the range of from 0.5 to 60 microns, more preferably from 1 to 60 microns, still more preferably from 1 to 50 microns. A particle size range of from 1 to microns, more preferably from 1 to 30 microns has been found to be particularly

suitable.

The microcapsules may comprise the polymer in a suitable amount to provide the required properties of the formulation. Preferably, the polymer is present in an amount of from 2% to 25% by weight of the microcapsules, more preferably from 3 to 20%, still more preferably from 5 to 15% by weight. A particularly suitable amount of polymer in the microcapsules is in the range of from 5 to 12% by weight.

The formulation of the first aspect of the present invention may comprise the microcapsules as described above suspended in an aqueous phase. The aqueous phase comprises water, together with other components required to impart the desired properties to the formulation, for example stability of the suspension and dispersibility of the microcapsules. Suitable components for inclusion in the aqueous phase of the formulation are known in the art and are commercially available.

Suitable components are those that improve and maintain the dispersibility and suspension of the microcapsules, and include one or more surfactants, stabilizers, emulsifiers, viscosity modifiers, protective colloids, and the like.

In addition, the aqueous phase may comprise one or more pH adjusters, for

example citric acid.

The aqueous phase may make up any suitable amount of the formulation, provided the microcapsules arc well dispersed and maintained in suspension.

Typically, the aqueous phase will comprise from 15 to 50% by weight of the formulation, more preferably from 20 to 40%, still more preferably from 25 to 30%.

The formulation of the present invention may be used in known manner to control the growth of plants. In particular, the formulation may be diluted with water to the required concentration of active ingredient and applied to a locus in known manner, such as by spraying.

It has also been found that the formulation of the present invention may also be prepared in a dried form that is without the microcapsules being suspended in an aqueous phase.

The formulation of this aspect of the invention, in use, is typically mixed with water to the required level of dilution to form a suspension of microcapsules in an aqueous phase, which may then be used and applied in known manner, as described above.

The formulations of the present invention may be prepared in a manner analogous to the preparation of known microencapsulation formulations. In general, the reactants forming the polymer of the walls of the microcapsules are dispersed between an organic liquid phase and an aqueous liquid phase, such that polymerization takes place at the interface between the two phases. For example, in the case of microcapsules formed from polyurea, the isocyanate, optionally with a cross-linking agent, such as an acetylene carbamide derivative (ACD) cross-linker, is dispersed in the organic rosin solvent system, together with the clomazone active ingredient, while the adjuvent is dispersed in the aqueous phase. The two phases are then mixed, to allow the polymer to form at the interface.

Acetylene carbamide derivatives (ACD) useful as cross-linking agents are known in the art, for example as disclosed in US 2011/0269063. Suitable ACD5 are also known as glycoluril resins and include those represented by the following formula: \ Ri wherein Ri, R2, R3. and R4 each independently represents a hydrogen atom or an alkyl with, for example, 1 to about 12 carbon atoms, 1 to about 8 carbon atoms, 1 to about 6 carbon atoms, or with 1 to about 4 carbon atoms.

The glycoluril resin can be water soluble, dispersible, or indispersible.

Examples of the glycoluril resin include highly alkylated/alkoxylated, partially alkylated/alkoxylated, or mixed alkylated/alkoxylated, and more specifically, the glycoluril resin can be methylated, n-butylated, or isobutylated. Specific examples of the glycoluril resin include CYMEL® 1170, 1171 and 1172. CYMEL® glycoluril resins are commercially available from CYTEC Industries, Inc. The normally liquid, substantially fully mixed-alkylated, substantially fully methylolated acetylene carbamides are a class of cross-linking agents, the starting material of which is acetylene carbamide, per se, which is also known as acetylene diurea which is prepared by reacting two moles of urea with one mole of glyoxal. The precise chemical name for acetylene carbamide is tetrahydroimidazo-(4, 5-d) imidazole 2, 5(1 H. 3H)-dione. The acetylene carbamide can be fully methylolated by reacting one mole of acetylene carbamide with four moles of formaldehyde. The resulting product is identified as tetramethylol acetylene carbamide. The tetramethylol acetylene carbamide is then reacted with a selected amount of methanol so as to partially methylate the fully methylolated acetylene carbamide which is then followed by alkylation with a higher aliphatic monohydric alcohol containing from two to four carbon atoms. These monohydric alcohols may be primary or secondary alcohols. These higher monohydric aliphatic alcohols containing from two or four carbon atoms may be ethanol, n-propanol, isopropanol, n-butanol, isobutanol and the like. It is sometimes advantageous to fully methylate the tetramethylol acetylene carbamide and then by use of a transetherification reaction incorporate the desired measure of ethanol, propanol or butanol into the acetylene carbamide derivative.

These fully etherified, fully methylolated acetylene carbamide derivatives are not considered to be resinous materials since they are, as individual entities, simple pure compounds or mixtures of simple pure compounds but they are potential resin- forming compounds which enter into chemical reaction with certain ionic water-dispersible, non-gelled polymeric materials when subjected to heat and particularly when subjected to heat under acidic conditions. The concept of the degree of methylation or more broadly alkylation, on average, and the concept of the degree of methylolation, on average, will be discussed herein below in order that this concept may be fully understood.

Theoretically, it is possible to methylolate acetylene carbamide fully, that is, to produce tetramethylol acetylene carbamide. However, frequently, in a commercial composition purporting to be tetramethylol acetylene carbamide, when analyzed, may show a fractional degree of methylolation. It is well recognized that fractional methylolation is not considered to be possible. As a consequence, when a composition contains on analysis a degree of methylolation of 3.70, 3.80, or 3.90, it has to be recognized that this is an average degree of methylolation of the acetylene carbamide compound and establishes logically that the aforementioned methylol composition is composed of a mixture of a preponderant amount of tetramethylol acetylene carbamide with comparatively minor amounts of trimethylol acetylene carbamide and, perhaps, insignificant amounts including traces of such derivatives as dimethylol acetylene carbamide and even monomethylol acetylene carbamide.

The same concept of averages is also applicable to the alkylation or etherification of the tetramethylol acetylene carbamide composition. There cannot be, based on present reasoning, a fractional alkylation and, as a consequence, when on analysis, a given composition shows that the degree of methylation is, on average, between about 0.9 and 3.60 and that the higher alkylation has an average degree of ethylation, propylation and/or butylation, on average, correspondingly between about 2.80 and 0.40, it must be concluded that there is present in such a composition a plurality of the mixed ethers of the tetramethylol acetylene carbamide. For example, there may be present some monomethyl ether, triethyl ether of tetramethylol acetylene carbamide, some dimethyl ether, diethyl ether of tetramethylol acetylene carbamide, some trimethyl ether, monoethyl ether of tetramethylol acetylene carbamide. There may even be traces of the tetramethyl ether of tetramethylol acetylene carbamide. There may also be present with the varying methyl ethers of tetramethylol acetylene carbamide varying mono, di and tn ethyl ethers, mono, di and tn propyl ethers and mono, di and tn butyl ethers of tetramethylol acetylene carbamide. It is possible to produce a monomethyl ether, monoethyl ether, monopropyl ether, monobutyl ether of tetramethylol acetylene carbamide which could be classed as a tetramixed-alkylated derivative. It is generally preferred, however, to make use of only one higher monohydric alcohol containing from two to four carbon atoms with the methyl alcohol in making a mixed full ether of the tetramethylol acetylene carbamide. The dimixed-alkylated products are, therefore, preferred, although the trimixed-alkylated derivatives as well as the tetramixed-alkylated derivatives may also be used.

Regarding ACDs preferred are the ACDs of the Powderlink 1174 and Cymel® type commercial products, more preferably Cymel® 1171 (that is a highly alkylated glycouril resin) and Cymel® 1170 (that is a butylated glycoluril resin). The use of prepolymers of Cymel-type has been found to result in a more irregular reaction course when compared with the use of Powderlink® 1174. Therefore the most preferred ACD is Powderlink® 1174 (that is tetrakis (methyoxymethyl) glycoluril, CAS No. 17464-88-9). It should be noted that the commercial products may have compounds other than the monomers referred in the label (for example, Powderlink® 1174 may contain oligomers).

The selection of the cross-linking agent and the amount present may be used to control the porosity of the polymer wall of the microcapsules. Preferably, the composition comprises the cross-linking agent in an amount of from 0.1 to 20%, more preferably from 0.5 to 15% by weight of the microcapsules.

In a further aspect, the present invention provides a method for preparing a herbicide composition, the method comprising the steps of: providing a water immiscible phase comprising clomazone, an alga, an isocyanate and optionally an ACD cross-linker; providing an aqueous phase comprising one or more surfactants; combining the water immiscible phase and the aqueous phase to form a dispersion of the water immiscible phase in the aqueous phase; thereby forming microcapsules of polyurea containing droplets of the water immiscible phase; and curing the microcapsules.

The method comprises combining a water immiscible phase and an aqueous phase. This is carried out under conditions, such as with agitation, to form a dispersion of the water immiscible phase in the aqueous phase.

The aqueous phase contains at least one surfactant or emulsifier, to assist in forming the dispersion of the water immiscible phase in the aqueous phase. Other components required to impart the desired properties to the final composition, as noted above, may be included in the aqueous phase.

The microcapsules are formed by interfacial polymerization reactions of the isocyanate, and then cross-linked by the ACD resin, if present. The polymerization reaction is preferably allowed to proceed while the dispersion is being agitated.

The microcapsules once formed are cured, preferably by heating, to harden the polymer walls of the microcapsules. Curing typically takes place at a temperature of from 30 to 60C, more preferably from 40 to SOt, for a suitable length of time, typically from ito 5 hours, more typically from about 2 to 4 hours.

The resulting composition is preferably then filtered, after cooling, to provide a suspension of the microcapsules in the aqueous phase. The resulting product is a CS formulation of clomazone suitable for use and application as described above, in particular by dilution with water and application by spraying, using techniques known in the art. Should it be required to prepare dry microcapsules, the resulting composition is subject to a drying stage, to remove the aqueous phase. Any suitable drying techniques may be employed, with spray drying being particularly effective.

The composition may be prepared with microcapsules formed from other polymers, as noted hereinbefore, using the appropriate wall-forming reagents in an analogous manner to the above procedure.

The microcapsules may contain only the active ingredient and one or more algae. More preferably, the active ingredient, in particular clomazone, and one or more algae are present in the microcapsules together with a liquid carrier.

The liquid carrier is immiscible with water. The liquid carrier preferably comprises one or more fatty acid esters of C1-C4alkanols. Preferably, the fatty acid esters are present in an amount such that the one or more fatty acid esters of C1-C4 alkanols amount to about 10 to about 50% by weight of the final composition. The liquid carrier can further comprise one or more additional formulating ingredients such as other substances used as liquid carriers.

The fatty acid portions of the fatty acid esters consist of a carboxylate moiety bound to a hydrocarbon chain, which can be unbranched or branched, but is typically unbranched in natural sources. The hydrocarbon chain can be saturated or unsaturated. Typically the hydrocarbon chain is saturated (that is an alkyl chain) or contains 1 or 2 carbon-carbon double bonds (that is an alkenyl chain). Fatty acid esters formed from fatty acids containing an odd number of carbon atoms (that is an even number of carbon atoms in the hydrocarbon chain) are useful in the compositions of the present invention, as well as fatty acid esters formed from fatty acids containing an even number of carbon atoms (that is an odd number of carbon atoms in the hydrocarbon chain). However, fatty acids obtained from natural sources typically contain an even number of carbon atoms, and therefore esters of fatty acids containing an even number of carbon atoms are preferred for reason of commercial availability and cost. Fatty acid compositions obtained from natural sources (for example, seed oils) typically consist of fatty acids having a range of chain lengths and different degrees of unsaturation. Fatty acid ester compositions derived from such fatty acid mixtures are generally useful in the compositions of the present invention without the need to first separate the fatty acid esters.

Fatty acids contain at least 4 carbon atoms and are limited to about 22 carbon atoms from natural sources. Although esters of lower fatty acids (for example, containing as few a 4 carbon atoms) are useful for the composition of the present mv ention, esters of fatty acids having at least 8, more preferably at least 10, carbon atoms are preferred because of favorable physical properties (for example, low volatility). Esters of lower fatty acids can be mixed with esters of higher fatty acids to decrease polarity, water solubility and volatility. As fatty acids obtained from natural sources typically contain 8 to 22 carbon atoms, more typically 10 to 22 carbon atoms, esters of these fatty acids are preferred for reason of commercial availability and cost. The C10-C22 fatty acid esters with an even number of carbon atoms are, for example, erucic acid, lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid and linolenic acid. Preferably the one or more fatty esters in the compositions of the present invention comprise at least about 10%, more preferably at least 15%, by weight of esters of fatty acids containing 8 to 22 carbon atoms, preferably 12 to 20 carbon atoms and more preferably 16 to 18 carbon atoms.

Fatty acid compositions obtained from natural sources (for example, seed oils) typically consist of fatty acids having a range of chain lengths and different degrees of unsaturation. Fatty acid ester compositions derived from such fatty acid mixtures can be useful in the compositions of the present invention without need to first separate the fatty acid esters. Suitable fatty acid ester compositions obtained from plants include seed and fruit oils of sunflower, rapeseed, olive, corn, soybean, cotton and linseed. Of note is a composition of the present invention wherein the one or more fatty acid esters comprise fatty acid methyl esters derived from seed oils of sunflower, soybean, cotton or linseed. Of particular note is a composition of the present invention wherein the one or more fatty acid esters comprise fatty acid methyl esters derived from soybean oil (also known as methylated soybean oil or methyl soyate).

Fatty acid esters of alkanols and methods for their preparation are well known in the art. For example, biodiesel" typically comprises fatty acid esters of ethanol or more commonly methanol. Two principal routes used to prepare fatty acid alkanol esters are transesterification starting with another fatty acid ester (often a naturally occurring ester with glycerol) and direct esterification starting with the fatty acid. A variety of methods are known for those carrying out these synthesis routes. For example, direct esterification can be accomplished by contacting a fatty acid with an alkanol in the presence of a strong acid catalyst such as sulfuric acid.

Transesterification can be accomplished by contacting a starting fatty acid ester with the alcohol in the presence of a strong acid catalyst such as sulfuric acid but more commonly a strong base such as sodium hydroxide.

Alkylated seed oils are the transesterification products of seed oils with an alkanol. For example methylated soybean oil, also known as methyl soyate, comprises methyl esters produced by the transesterification of soybean oil with methanol. Methyl soyate thus comprises methyl esters of fatty acids in the approximate molar ratio that the fatty acids occur esterified with glycerol in soybean seed oil. Alkylated seed oils such as methyl soyate can be distilled to modify the proportion of methyl fatty acid esters.

The weight ratio of the liquid carrier to the active ingredient, within the capsules is preferably from 1:2 to 1:99, more preferably from 1:4 to 1:99. In one preferred composition, there are present 1 to 20 parts by weight of liquid carrier and to 99 parts by weight of the clomazone.

Other components that may be present in the water immiscible liquid phase and encapsulated within the finished microcapsules are known in the art and include surfactants, stabilizers and the like. In particular, antioxidants may be included in the solvent system within the microcapsules. As described above, preparation of the formulation may require heating of the formulation to cure the polymers walls of the microcapsules. Heating the formulation may increase the rate of oxidation of the active components. Accordingly, one or more antioxidants may be included.

Suitable antioxidants are known in the art and are commercially available. Examples include butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). The antioxidant may be present in any suitable amount to reduce or prevent oxidation of the active ingredient and maintain its stability. The amount of antioxidant may be in the range of from 0.005 to 1.0% of the weight of the microcapsules, more preferably from 0.01 to 0.05% by weight.

The size of the microcapsules may controlled by a number of factors in the preparation of the composition of this invention, as noted above. In particular, the size of the microcapsules may be controlled by including on or more further components in the water-immiscible liquid phase within the microcapsules, in particular one or more surfactants. The hydrophile-lipophile balance (HLB) of the surfactants employed can influence the size of the microcapsules formed in the composition, with surfactants or surfactant combinations having a lower HLB giving rise to microcapsules having a lower diameter. Suitable oil-soluble surfactants are known and available commercially, for example Atlox 4912, an A-B-A block copolymer surfactant having a low HLB of about 5.5. Other block copolymer surfactants may be used, in particular those composed of polyglycol, for example polypropylenglycol, and hydroxylated polyfatty acids. The surfactants may be present in any suitable amount to impart the required particle size to the microcapsules during preparing of the composition. A preferred concentration in the water-immiscible phase is from 1 to 30%, more preferably about 5 to 25% by weight of the microcapsules.

The liquid phase within the microcapsules preferably contains at least 20% by weight clomazone, more preferably at least 30%, still more preferably at least 50% by weight clomazone. clomazone may be present in the encapsulated material in an amount of from 1% to 95% by weight, more preferably from 1% to 90%, still more preferably from 5% to 90% by weight.

To prepare the composition of the present invention, the algae may be pre-treated, for example by washing, preferably in water, and then drying, for example by centrifugation and/or spray drying. The algae may be treated by a final drying stage, for example heating to a temperature sufficient to dry the algae without denaturing the algae, such as to a temperature of from 50 to 70°C for a period of from 4 to 7 hours.

In one embodiment of the method of the present invention, the composition is prepared as follows: 1. Algae pretreatment: wash fresh algae in water and then remove water by centrifugation, remove impurities, spray dry to remove further water, finally dry the processed algae at 50 to 70 °C for 4 to 7 hours; 2. Water immiscible phase: mix dry pretreated algae, clomazone, an isocyanate, ACD cross-linker, in an organic solvent; 3. Aqueous phase: mix one or more surfactants and other adjuvant in water; 4. Combine the water immiscible phase and the aqueous phase to form a dispersion of the water immiscible phase in the aqueous phase; 5. Cure the microcapsules by heating.

In a further aspect, the present invention provides the use of a clomazone formulation as hereinbefore described in the control of plant growth.

In a still further aspect, the present invention provides a method of controlling plant growth at a locus, the method comprising applying to the locus a formulation of microencapsulated clomazone as hereinbefore described.

Embodiments of the present invention will now be described, for illustration only, by way of the following examples.

EXAMPLES

Example 1

Preparation of a formulation of microencapsulated clomazone A water immiscible phase and an aqueous phase were prepared having the following composition (with amounts of the components expressed in % weight of the final composition): Water immiscible phase clomazone 60.Og pretreated Algae (Synechocystis) 38.0 g PAPI (ex. Dow Chemicals) 5.50g C16C16 fatty acid methyl ester 20.Og Powderlink® 1174 3g Aciueous phase Atlox 4913 (surfactant; ex. Croda International) 0.6g Citric acid (pH adjuster) 0.14g Water 24.51g The algae was pretreated by washing in water, centrifuging to remove water, spray drying and finally heating a temperature of from 50 to 7000 for about 5 hours.

The pretreated algae, PAPI, clomazone, powderlink® 1174 and organic solvent were combined with stirring to form a uniform water immiscible liquid mixture.

A solution of Atlox 4913 in water was heated in a Warning blender cup to about 50C.

The solution was agitated while the water immiscible liquid mixture was slowly added, to form a uniform emulsion of the water immiscible phase dispersed evenly throughout the continuous aqueous phase, upon which interfacial polymerization occurred, producing microcapsules having a particle size of from 1 to 30 microns.

Once the polymerization reaction had finished, the resulting composition was cured by heating to 50CC for 2 hours. The resulting product was cooled and filtered, to obtain an agriculturally suitable CS formulation of microencapsulated clomazone.

The resultant product was tested for dispersibility and suspensibility of the microcapsules, and the wet sieve residue. It was found that the formulation had a suspensibility of greater than 90%, a dispersibility of greater than 90% and a wet sieve residue of less than 0.1%.

The results show that the formulations of the present invention, by employing an alga as a solid carrier for the clomzaone active ingredient, exhibit significantly improved properties compared with the prior art formulations.

Claims (28)

1. CLAIMS1. A herbicidal composition comprising microcapsules having a polymer shell and containing therein clomazone and at least one alga.
2. 2. The composition according to claim 1, wherein clomzone is present in the composition in an amount of at least 20% by weight.
3. 3. The composition according to claim 2, wherein clomazone is present in the composition in an amount of at least 50% by weight.
4. 4. The composition according to any preceding claim, wherein the alga is selected from Amphora, Anabaena, Anikstrodesmis, Botryococcus, Ghaetoceros, Chlore/la, Chlorococcum, Cyc/ote/la, Cy/indrotheca, Duna/ie//a, Emiliana, Eug/ena, Glossomastix, Hematococcus, /sochrysis, Monochiysis, Mon oraphidium, Nannoch/oris, Nannoch/oropsis, Na v/cu/a, Nephroch/or/s, Nephrose/mis, N/tzschila, Nodular/a, Nostoc, Oochromonas, Oocystis, Oscillartoria, Pa v/ova, Phaeodacty/um, Picochloris, P/a tymonas, P/eurochiys/s, Porhyra, Pseudoanabaena, Pyram/monas, Scenecjesmus, Stichococcus, Synechococcus,, Tetrase/mis, Tha/assios/ra, Trichodesm/um, and mixtures thereof.
5. 5. The composition according to claim 4, wherein the alga is selected from Monochrysis, Ch/orococcum, Synechocystis, Scenedesmus and mixtures thereof.
6. 6. The composition according to any preceding claim, wherein the alga is present in the composition in an amount of from 5% to 50% by weight.
7. 7. The composition according to any preceding claim, wherein the microcapsules shell comprises polyurea.
8. 8. The composition according to claim 7, wherein the polyurea shell is formed by the interfacial polymerization of an isocyanate.
9. 9. The composition according to claim 8, wherein the isocyanate is a polyisocyanate.
10. 10. The composition according to claim 9, wherein the polyisocyanate is selected from one or more of 1,3-and/or 1,4-phenylene dhsocyanates, 2,4-, 2,6-tolylene dUsocyanates [Dl), crude TDI, 2,4'-, 4,4'-diphenyl methane dUsocyanate (MDI), crude MDI, 4,4-diisocyanatebiphenyl, 3,3'-dimethyl-4-4-diisocyanate biphenyl, 3,3'-dimethyl-4,4'diisocyanate diphenylmethane, naphthylene-1,5-dUsocyanate, triphenylme!hane-4,4', 4"-triisocyana!e, m-and p-isocyanate phenylsulforyl isocyanate, polyaryl polyisocyanate (PAPI), diphenylmethane-4,4'-diisocyanate (PMDI), polymethylene polyphenyl isocyanatos (PMPPI) and derivatives and prepolymers thereof; or ethylene diisocyanate, hexamethylene diisocyanate (HDI), tetramethylene dilsocyanate, dodecamethylene dilsocyanate, 1,6,11 -undecan trUsocyanate, 2,2,4-trimethylhexa -methylene diisocyanate, lysine diisocyanate, 2,6-dUsocyanate methyl caproate, bis(2-isocyanate ethyl)fumarate, bis(2-isocyanate ethyl)carbonate, 2-isocyanate ethyl-2,6-diisocyanate hexanoate, trimethylhexamethylene dUsocyanate [MDI), dimer acid dhsocyanate (DDI), isophorone diisocyanate (IRDI), dicyclohexyl dhsocyanate, dicyclohexylmethane dUsocyanate (H-MDI), cyclohexylene diisocyanate, hydrogenated tolylenedilsocyanate (HIDI), bis(2-isocyanate ethyl)-4-cyclohexene-1 2-dicarboxylate, 2,5-and/or 2,6 norbornane diisocyanate, araliphatic polyisocyanates having 8 to 15 Carbon Atoms m-and/or p-xylylene diisocyanate (XDI), alpha-, alpha-, alpha-, alpha-tetramethyl xylylene diisocyanate (TMXDI), ethylene düsocyanate hexamethylene diisocyanate, (HDI), tetramethylene diisocyanate, dodecamethylene dUsocyanate, 1,6,11 -undecan triisocyanate, 2,2,4-trimethylhexa methylene dUsocyanate, lysine. diisocyanate, 2,6-diisocyanate methyl caproate, bis(2- isocyanate ethyl)tumarate, bis(2-isocyanate ethyl)carbonate, 2-isocyanate ethyl-2,6-dUsocyanate hexanoate, trimethylhexamethylene diisocyanate (TMDI), dimer acid dUsocyanate (DDI) and derivatives and prepolymers thereof.
11. 11. The composition according to claim 10, wherein the polyisocyanate is selected from alpha-, alpha-, alpha-, alpha-tetramethyl xylylene diisocyana!e (TMXDI), hexamethylene dUsocyanate (HDI), HDI derivative (HDI Trimer, HDI Urctdione) which arc commercially available Desmodur® N3600, XP241 0 and N3400, isophorone düsocyanate (IPDI), polymethylene polyphenyl isocyanates (PMPPI), methylene diphenyl isocyanate (MDI), polyaryl polyisocyanate (PAPI), toluene dhsocyanate (TDI) and mixtures thereof.
12. 12. The composition according to any of claims 7 to 11, wherein the walls of the microcapsules are formed from a polyurea formed by the interfacial polymerization of an isocyanate and an ACD cross-linking agent.
13. 13. The composition according to claim 12, wherein the ACD crosslinker is selected from tetrakis (methyoxymethyl) glycoluril or an alkylated glycoluril resin.
14. 14. The composition according to any preceding claim, wherein the microcapsules have a particle size in the range of from 0.5 to 60 microns.
15. 15. The composition according to claim 14, wherein the microcapsules have a particle size in the range of from 1 to 50 microns.
16. 16. The composition according to any preceding claim, wherein the polymer is present in the microcapsules in an amount from 2% to 25% by weight of the microcapsules.
17. 17. The composition according to claim 16, wherein the polymer is present in the microcapsules in an amount of from 5 to 15% by weight.
18. 18. The composition according to any preceding claim, wherein the microcapsules further contain a water immiscible solvent.
19. 19. The composition according to claim 18, wherein the solvent is a methyl ester of one or more fatty acids.
20. 20. The composition according to any preceding claim, wherein the microcapsules are suspended in an aqueous medium.
21. 21. The composition according to claim 20, wherein the aqueous phase comprises from 15 to 50% by weight of the composition.
22. 22. The composition according to any preceding claim, wherein clomazone is present within the microcapsules in an amount of from 1% to 95% by weight of the contents of the microcapsules.
23. 23. A method for preparing a herbicide composition, the method comprising the steps of: providing a water immiscible phase comprising clomazone, an alga, an isocyanate and optionally an ACD cross-linker; providing an aqueous phase comprising one or more surfactants; combining the water immiscible phase and the aqueous phase to form a dispersion of the water immiscible phase in the aqueous phase; thereby forming microcapsules of polyurea containing droplets of the water immiscible phase; and curing the microcapsules.
24. 24. The method according to claim 23, further comprising drying the resulting composition to remove the aqueous phase.
25. 25. A herbicidal composition substantially as hereinbefore described.
26. 26. The use of a composition according to any of claims 1 to 22 or claim 25 in the control of plant growth.
27. 27. A method of controlling plant growth at a locus, the method comprising applying to the locus a composition according to any of claims 1 to 22 or claim 25.
28. 28. A method for controlling plant growth substantially as hereinbefore described.