GB2509427A

GB2509427A - Herbicidal composition comprises clomazone microcapsules

Info

Publication number: GB2509427A
Application number: GB1405434.0A
Authority: GB
Inventors: James Timothy Bristow; Yifan Wu
Original assignee: Rotam Agrochem International Co Ltd
Current assignee: Rotam Agrochem International Co Ltd
Priority date: 2014-03-26
Filing date: 2014-03-26
Publication date: 2014-07-02
Anticipated expiration: 2034-03-26
Also published as: GB2509427B; CN106061266B; FR3018999A1; EP3122189A4; GB201405434D0; WO2015143975A1; CN106061266A; EP3122189A1; FR3018999B1

Abstract

A herbicidal composition comprises microcapsules, the microcapsules having a capsule wall of a porous condensate polymer, wherein the microcapsules contain clomazone and a solvent comprises rosin and/or a rosin derivative. In one embodiment the microcapsules are in an aqueous suspension. Also claimed is a method of preparing a herbicidal composition, the method comprises the steps of: providing a water immiscible phase comprising clomazone, an isocyanate and optionally an acetylene carbamide derivative (ACD) cross-linker, dissolved in a rosin solvent system comprising rosin and/or a rosin derivative; providing an aqueous phase comprising one or more surfactants; combining the water immiscible phase and the aqueous phase to form a dispersion of the two phases; 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.

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

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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 -C) branched alkyl ester.

ER 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 (RMPRI), 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 been found that particularly effective microencapsulated formulations of clomaozne may be prepared using rosin and/or rosin derivatives as solvents. In particular, it has been found that the use of rosin and/or rosin derivatives provides the clomazone with a high dispersability, while still allowing the formulation to be readily suspended in water during the process for forming the microcapsules.

Further, the formulation exhibits a low wet sieve residue that is a high degree of retention of the clomazone active ingredient in the microcapsules. It has also been found that the rosin and/or rosin derivatives exhibit a lower toxicity than solvents used in the prior art formulations, in particular the 1,2-benzenedicarboxylic di-(C3-C6) branched alkyl esters and the aromatic hydrocarbon and petroleum solvents of the

prior art compositions and described above.

Accordingly, in a first aspect, the present invention provides a herbicidal composition comprising an aqueous suspension of microcapsules, the microcapsules having a capsule wall of a porous condensate polymer, wherein the microcapsules contain a solution of clomazone in a rosin solvent system comprising rosin and/or a rosin derivative.

Surprisingly, it has been found that microencapsulating clomazone in a solvent comprising rosin and/or a rosin derivative provides a significantly improved formulation, in particular having the properties of a high dispersibility, ease of forming and maintaining in suspension, and a low wet sieve residue. A further advantage is that the rosin and rosin derivatives used as solvents for the clomazone are significantly less toxic than the solvents known and used in the prior art formulations.

The clomazone formulation of the present invention comprises microcapsules suspended in an aqueous phase. The microcapsules contain a solution of clomazone in a solvent phase comprising rosin and/or a rosin derivative, such that the clomazone in the formulation is retained within the microcapsules.

Clomazone is the common name of 2-[(2-chlorophenyl)methyl]-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.

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The formulation may comprise clornazone 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.

In the formulation of the present invention, clomazone is retained in solution in an organic solvent system within the microcapsules. The solvent comprises rosin and/or a rosin derivative. Other solvents may be present within the microcapsules.

However, it is preferred that the solvent consists essentially of rosin and/or one or more rosin derivatives. Rosin and its derivatives are insoluble in water. Rosin and its derivatives are known in the art and are commercially available. Rosin derivatives that may be used as or included in the solvent system of the formulation include any derivative that is a liquid under ambient conditions and in which Clomazone is soluble. Suitable derivatives include hydrogenated rosin, polymerized rosin, esters of rosin or hydrogenated rosin, in particular lower alkyl esters (that is C1 to C4 alkyl esters), especially methyl esters of rosin or of hydrogenated rosin, glycerol esters of rosin or hydrogenated rosin, triethylene glycol esters of rosin or hydrogenated rosin and pentaerythratol esters of rosin or hydrogenated rosin.

The microcapsules may contain a solution consisting essentially of rosin and/or a rosin ester and Clomazone. Other components may be included in the solvent system, as required. Other components that may be present in the solution 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 in more detail below, 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 be controlled by a number of factors in the preparation of the composition of this invention. 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 rosin solvent system within the microcapsules contains the solvent, in particular the rosin and/or rosin derivatives, in sufficient amount to dissolve the required amount of clomazone. Preferably, the weight ratio of clomazone to rosin solvent is from 1:10 tol 0:1, more preferably from 1:5 to 5:1, still more preferably from 2:5 to 5:2.

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.

The rosin and/or rosin derivative solvent is preferably present in the liquid within the microcapsules in an amount of at least 10% by weight, more preferably at least 20% by weight, still more preferably at least 30% by weight.

The solution of clomazone in the rosin solvent system is contained within the microcapsules. The microcapsules may be formed from any suitable 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 diisocyanates (TDI), crude TDI, 2,4'-, 4,4'-diphenyl methane diisocyanate (MDI), crude MDI, 4,4'-diisocyanatebiphenyl, 3,3'-dimethyl-4-4'-diisocyanate biphenyl, 3,3'-dimethyl-4,4'diisocyanate diphenylmethane, naphthylene-1,5-dUsocyanate, triphenylmethane-4,4', 4"-trhsocyanate, m-and p-isocyanate phenylsulfonyl isocyanate, polyaryl polyisocyanate (PAR), diphenylmethane-4,4'-düsocyanate (PMDI), polymethylene polyphenyl isocyanates (PMPPI) and derivatives and prepolymers of aromatic isocyanates.

Aliphatic polyisocyanates can be ethylene diisocyanate, hexamethylene diisocyanate (HDI), tetramethylene düsocyanate, dodecamethylene diisocyanate, 1,6,11-undecan trUsocyanate, 2,2,4-trimethylhexa -methylene diisocyanate, lysine dUsocyanate, 2,6-diisocyanate methyl caproate, bis(2-isocyanate ethyfumarate,

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bis(2-isocyanate ethyl)carbonate, 2-isocyanate ethyl-2,6-düsocyanate hexanoate, trimethyihexamethylene dUsocyanate (TMDI), dimer acid dhsocyanate (DDI), isophorone diisocyanate (IPDI), dicyclohexyl dUsocyanate. dicyclohexylmethane diisocyanate (H-MDI), cyclohexylene dUsocyanate, hydrogenated tolylenediisocyanate (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 dUsocyanate (XDI), alpha-, alpha-, alpha-, aipha-tetramethyl xylylene dUsocyanate (TMXDI), ethylene diisocyanate hexamethylene dUsocyanate, (HDI), tetramethylene dUsocyanate, dodecamethylene dUsocyanate, 1,6,11 -undecan triisocyanate, 2,2,4-trimethylhexa methylene dUsocyanate, lysine, diisocyanate, 2,6-diisocyanate methyl caproate, bis(2- isocyanate ethyl)fumarate, bis(2-isocyanate ethyl)carbonate, 2-isocyanate ethyl-2,6-dUsocyanate hexanoate, trimethylhexamethylene diisocyanate (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.

Preferred isocyanates for forming the polyureas are known in the art and are commercially available, including alpha-, alpha-, alpha-, alpha-tetramethyl xylylene diisocyanate (TMXDI), hexamethylene diisocyanate (HDI), HDI derivative (HDI Trimer, HDI Uretdione) which are commercially available Desmodurt N3600, XP2410 and N3400, isophorone diisocyanate (IPDI), polymethylene polyphenyl isocyanates (PMPPI), methylene diphenyl isocyanate (MDI). polyaryl polyisocyanate (PAPI), and toluene dUsocyanate (TDI).

The microcapsules of the present invention may be further formed from a polyfunctional amine. Suitable amines for use have two or amine groups. Examples of suitable amines for use in the present invention are diamine and higher polyamine reactants, including ethylene diamine, phenylene diamine, toluene diamine, hexamethylene diamine, diethylene triamine, piperazine, 1,3,5-benzenetriamine trihydrochloride, 2,4,6-triaminotoluene trihydrochloride, tetraethylene pentamine, pentaethylene hexamine, polyethylene imine, 1,3,6-triaminonaphthlene, 3,4,5-triamino-1,2,4-triazole, melamine, and 1,4,5,8-tetraminoanthraquinone.

Preferred amines for forming the polyureas are known in the art and are commercially available, including ethylenediamine (EDA), diethyltriamine (DETA), triethylenetetramine (TETA), and 1,6-hexanediamine (HDA).

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 clomazone 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 comprises 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.

The aqueous phase may make up any suitable amount of the formulation, provided the microcapsules are 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 be prepared in a dried form that is without the microcapsules being suspended in an aqueous phase.

Accordingly, in a further aspect, the present invention provides a herbicidal composition comprising microcapsules, the microcapsules having a capsule wall of a porous condensate polymer, wherein the rnicrocapsules contain clomazone and a solvent comprising rosin and/or a rosin derivative.

Details of the microcapsules and their composition are as hereinbefore described.

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 ACDs 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 rnethylol 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 isocyanate and optionally an ACD cross-linker, dissolved in a rosin solvent system comprising rosin and/or a rosin derivative; 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. 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 Sot, more preferably from 40 to 50CC, for a suitable length of time, typically from 1 to 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. 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.

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.

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 50.Og PAPI (ex. Dow Chemicals) 3.50g Methyl ester of hydrogenated rosin 20.Og Powderlink® 1174 2g Water phase Atlox 4913 0.Bg (ethoxylated methyl methacrylate surfactant; ex. Croda International) Citric acid 0.14g Water 25.51g The PAPI, clomazone, powderlink® 1174 and rosin derivative 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 50C 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 a rosin solvent system for the clomazone active ingredient, exhibit significantly improved properties compared with the prior art formulations.

Claims

CLAIMS1. A herbicidal composition comprising an aqueous suspension of microcapsules, the microcapsules having a capsule wall of a porous condensate polymer, wherein the microcapsules contain a solution of clomazone in a rosin solvent system comprising rosin and/or a rosin derivative.
2. The composition according to claim 1, wherein clomazone is present in the composition in an amount of at least 20% by weight.
3. The composition according to claim 2, wherein clomazone is present in the composition in an amount of at least 50% by weight.
4. The composition according to any preceding claim, wherein the rosin solvent system consists essentially of rosin and/or a rosin derivative.
5. The composition according to any preceding claim, wherein the rosin solvent system comprises a rosin derivative selected from hydrogenated rosin, polymerized rosin, esters of rosin or hydrogenated rosin.
6. The composition according to claim 5, wherein the rosin solvent system comprises a rosin derivative selected from methyl esters of rosin or of hydrogenated rosin, glycerol esters of rosin or hydrogenated rosin, triethylene glycol esters of rosin or hydrogenated rosin and pentaerythratol esters of rosin or hydrogenated rosin.
7. The composition according to any preceding claim, wherein the microcapsules further contain one or more surfactants, stabilizers or a mixture thereof.
8. The composition according to any preceding claim, wherein the weight ratio of clomazone to rosin solvent is from 1:10 tolO:1.
9. The composition according to claim 8, wherein the weight ratio of clomazone to rosin solvent is from 1:5 to 5:1.
10. The composition according to claim 9, wherein the weight ratio of clomazone to rosin solvent is from 2:5 to 5:2.
11. The composition according to any preceding claim, wherein the liquid phase within the microcapsules contains at least 20% by weight clomazone.
12. The composition according to claim 11, wherein the liquid phase within the microcapsules contains at least 30% by weight clomazone.
13. The composition according to claim 12! wherein the liquid phase within the microcapsules contains at least 50% by weight clomazone.
14. The composition according to any preceding claim, wherein clomazone is present in the encapsulated liquid phase in an amount of from 1% to 95% by weight.
15. The composition according to claim 14! wherein clomazone is present in the encapsulated liquid phase in an amount of from 5% to 90% by weight.
16. The composition according to any preceding claim, wherein the rosin and/or rosin derivative is present in the liquid within the microcapsules in an amount of at least 10% by weight.
17. The composition according to claim 16. wherein the rosin and/or rosin derivative is present in the liquid within the microcapsules in an amount of at least 20% by weight.
18. The composition according to claim 17! wherein the rosin and/or rosin derivative is present in the liquid within the microcapsules in an amount of at least 30% by weight.
19. The composition according to any preceding claim, wherein the walls of the microcapsules are formed from a porous condensate polymer of one or more of a polyurea, polyamide or amide-urea copolymer.
20. The composition according to claim 19! wherein the walls of the microcapsules are formed from a polyurea formed by the interfacial polymerization of an isocyanate and, optionally, an ACD cross-linking agent.
21. The composition according to claim 20, wherein the isocyanate is selected from alpha-, alpha-, alpha-, alpha-tetramethyl xylylene dUsocyanate (TMXDI), hexamethylene diisocyanate (HDI), an HDI derivative, isophorone dhsocyanate (IRDI), polymethylene polyphenyl isocyanates (PMPPI), methylene diphenyl isocyanate (MDI), polyaryl polyisocyanate (PAR), and toluene dUsocyanate (TDI).
22. The composition according to either of claims 20 or 21, wherein the ACD crosslinker is selected from tetrakis (methyoxymethyl) glycoluril or an alkylated glycoluril resin.
23. The composition according to any preceding claim, wherein the microcapsules have a particle size in the range of from 0.5 to 60 microns.
24. The composition according to claim 23! wherein the microcapsules have a particle size in the range of from 1 to 50 microns.
25. The composition according to claim 24, wherein the microcapsules have a particle size in the range of from 1 to 30 microns.
26. 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.
27. The composition according to claim 26! wherein the polymer is present in the microcapsules in an amount of from 5 to 15% by weight.
28. The composition according to any preceding claim, wherein the aqueous phase comprises one or more surfactants, stabilizers, viscosity modifiers, or protective colloids.
29. The composition according to any preceding claim, wherein the aqueous phase comprises from 15 to 50% by weight of the formulation.
30. A herbicidal composition comprising microcapsules, the microcapsules having a capsule wall of a porous condensate polymer, wherein the microcapsules contain clomazone and a solvent comprising rosin and/or a rosin derivative.
31. A method for preparing a herbicidal composition, the method comprising the steps of: providing a water immiscible phase comprising clomazone, an isocyanate and optionally an ACD cross-linker, dissolved in a rosin solvent system comprising rosin and/or a rosin derivative; 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.
32. The method according to claim 31, further comprising drying the resulting composition to remove the aqueous phase.
33. A herbicidal composition substantially as hereinbefore described.
34. The use of a composition according to any of claims 1 to 30 or claim 33 in the control of plant growth.
35. 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 30 or claim 33.
36. A method for controlling plant growth substantially as hereinbefore described.