WO1999039577A1

WO1999039577A1 - Water-dispersible flake compositions

Info

Publication number: WO1999039577A1
Application number: PCT/GB1999/000282
Authority: WO
Inventors: Herbert Benson Scher; Richard Dulin Offeman; Roger Rachid Djafar; Marius Rodson
Original assignee: Zeneca Limited
Priority date: 1998-02-03
Filing date: 1999-01-27
Publication date: 1999-08-12
Also published as: JO2094B1; GT199900016A; YU50300A; ZA99768B; NO20003938L; SK11732000A3; CN1292640A; PE20000242A1; AU4480699A; TR200002643T2; BR9908781A; HRP20000526A2; HUP0100736A2; BG104661A; EP1051070A1; GEP20022781B; EA200000813A1; NO20003938D0; HUP0100736A3; IL137682A0

Abstract

A water-dispersible flake comprises a plurality of microcapsules or microparticles containing one or more encapsulated ingredients, for example a pesticide such as a herbicide or an insecticide, wherein the microcapsules or microparticles are held together in flake form by spacer material such as a nonencapsulated pesticide and/or one or more surfactants. The flake may be prepared by (a) mixing an aqueous suspension of the microcapsules or microparticles with spacer material and/or a surfactant to form a dispersion (b) drying the dispersion by thin-layer drying on a heated surface and (c) removing the dried product of step (b) from the heated surface to form flakes.

Description

-1-

WATER-DISPERSIBLE FLAKE COMPOSITIONS

Field of the Invention

This invention relates to a water-dispersible flake composition comprising a plurality of microcapsules or microparticles bound together by spacer material. In another aspect, this invention relates to a process for the production of such flakes.

Background of the Invention

There is a recognized need in the agrochemical industry for formulations of active ingredients which are safe, effective and economical. In this regard, it is advantageous to have pesticidal formulations which are in dry foπn and yet which are rapidly dispersible in water.

Dry formulations have the advantage that it is easier and less expensive to dispose of the container in which they are packaged. Thus, it is possible to ship dry pesticidal materials in containers made of paper or water-soluble plastic bags. In addition, dry formulations possess an economic advantage in that the shipping costs associated with the aqueous or organic solvent employed in other types of formulations are reduced or eliminated. Other advantages are that there is a corresponding lower volume of material which must be packed, shipped and loaded, and that spills are generally easier to contain and clean up.

For many active ingredients (both liquids and solids), microencapsulation provides a practical route to solid formulations useful in the production of stable aqueous sprayable suspensions. The use of microencapsulation -2- permits, in many cases, reduced toxicity and/or extended activity of the encapsulated active material. Further, microencapsulation can be effectively used to postpone the decomposition or utilization of pesticides which would otherwise quickly lose their efficacy in the field. In addition, microencapsulation provides a potential means of combining substances that are otherwise incompatible with each other.

True microcapsules are particles which comprise a polymer shell or shells surrounding and enclosing one or more encapsulated ingredients. Another form of encapsulation involves the production of a matrix of polymer which physically includes one or more ingredients dispersed, dissolved or otherwise trapped in the polymer. Smaller particles are obtained by physically breaking up the polymer matrix. The small particles thus obtained are generally termed "microparticles," and are produced in similar size and size ranges to microcapsules. Solid formulations of microencapsulated pesticides include products produced by extrusion or by spray drying. Extrusion, however, can cause breakage of capsules and does not allow for relatively high loading of the active pesticide because of the amount of water which must be present to permit processing. When producing dry formulations, it is also desirable to produce product formulations having sufficient size and structural integrity such that problems associated with dusting are minimized.

U.S. Patents 4,936,901 and 5,354,742 describe generally spherical aggregates composed of microcapsules of encapsulated pesticides. These spherical granules exhibit many desirable economic and safety properties. Nevertheless, production of spray-dried materials can be expensive; in general it would be desirable to produce other solid forms of microencapsulated pesticidally active ingredients

Accordingly, it is an object of this invention to provide a novel dry formulation of a microencapsulated active ingredient or of microparticles containing such an ingredient which provides unexpectedly enhanced economic and safety advantages. The objective of this invention is not limited to products containing pesticides. -3-

Microencapsulation and microparticles are widely used for other materials and dry formulations of these can have similar advantage to pesticidal formulations.

Summary of the Invention

In one aspect, the present invention is directed to a water-dispersible flake comprising a plurality of microcapsules or microparticles containing one or more ingredients, said microcapsules or microparticles being held together in flake form by spacer material and/or one or more surfactants.

In another aspect, this invention is directed to a method for producing water-dispersible flakes, each of said flakes comprising a plurality of microencapsules or microparticles held together in flake form by spacer material and/or one or more surfactants, comprising the steps of:

a) mixing an aqueous suspension of microcapsules or microparticles with a spacer material and/or one or more surfactants to form a dispersion;

b) drying the dispersion by thin-layer drying on a heated surface; and

c) Removing the dried product of step (b) from the heated surface to form flakes.

Because of their flake form the compositions of this invention can be piled with fewer points of contact between the flakes than with generally spherical granules, with the result that they are less likely to compact, i.e., less likely to form solid blocks of material rather than agglomerations of individual particles. -4. Description of the Preferred Embodiments

The present invention is directed to water-dispersible flakes comprising a plurality of microcapsules or microparticles held together by spacer material and/or one or more surfactants.

As is employed herein, the term "flake" relates to a composition having an aspect ratio, i.e., ratio of maximum length to thickness, greater than about 5:1. Typically, the aspect ratio will be from about 5:1 to about 1000:1, preferably from about 10:1 to about 100: 1. In general, the flakes of this invention will have a maximum thickness of from about 0.05 to about 2.0, preferably from about 0.1 to about 1.0, mm.

Microcapsules which are formulated into the flakes of the present invention are comprised of a core liquid active material enclosed within a polymeric shell. The core liquid should be substantially insoluble in or immiscible with water. It may consist of a single liquid material or one or more active liquid or solid materials dissolved and/or suspended in an inert solvent which has at most a slight solubility in water. In the latter case, the Uquid or solid solute must reside preferentially in the organic phase as opposed to water.

The encapsulated material can be selected from many types of substances which are suitable for encapsulation, such as pharmaceuticals, biocides, personal care products, dyes, inks, hormones, repellants, growth regulators, pesticides and others. For convenience, this invention is described and exemplified in terms of pesticides, but this invention is also applicable to these other substances. If the encapsulated material is a pharmaceutical, the ingredients of the flakes should be suitable for inclusion in pharmaceutical compositions.

Pesticidal liquids and suspended solids suitable for encapsulation or for production of microparticles include chemical-biological agents such as herbicides, insecticides, fungicides, nematocides, bactericides, rodenticides, molluscicides, acaricides, -5- and larvicides. Non-pesticidal materials used for pest control or otherwise in related activities such as agriculture and domestic, commercial or industrial pest control, for which this invention is suitable, include animal, insect, and bird repellents, plant growth regulators, insect growth regulators, fertilizers, pheromones, sex lures and attractants, and flavor and odor compositions.

Illustrative of the herbicides are α-chloro-2',6'-diethyl-N-methoxymethyl acetanilide (alachlor); N-butoxymethyl- α-chloro-2',6'diethylacetanilide (butachlor); 2'- methyl-6'-ethyl-N-( 1 -methoxy-prop-2-yl)-2-chloroacetanilide (metolachlor); 2'-t-butyl-2- chloro-N-methoxymethyl-6'-methylacetanilide; a-chloro-N-(2-methoxy-6-methylphenyl) - N-(l-methylethoxymethyl)-acetamide; a-chloro-N-(ethoxymethyl)-N-[2-methyl-6- (trifluoromethyl)phenyl]-acetamide; α-chloro-N-methyl-N-[2-methyl-6-(3-methylbutoxy) phenyl] acetamide; α-chloro-N-methyl-N-(2-methyl-6-propoxyphenyl)acetamide; N-(2- butoxy-6-methylphenyl)-2-chloro-N-methyl acetamide; N-(2,6-dimethylphenyl)-N-( 1 - pvrazolylmethyl)chloroacetanilide (metazochlor); N,N-diaIlyl-2-chloroacetamide (allidochlor); isobutyl ester of (2,4-dichlorophenoxy)acetic acid; 2-chloro-N- (ethoxymethyl)-6'-ethyl-o-acetotoluidide (acetochlor); 1 -( 1 -cyclohexen- 1 -yl)-3 -(2- fluorophenyl)-l -methyl urea; S-2,3,3-trichloroallyldϋsopropyl thiocarbamate (triallate); S- 2,3-dichloroallyldiisopropylthiocarbamate (diallate); α,α,α-trifluoro-2, 6-dinitro-N,N- dipropyl-p-toluidine (trifluralin), 2-(2-chlorophenyl)methyl-4,4-dimethyl-3 -isoxazolidinone (clomazone); 3,5-pyridine-dicarbothioc add, 2-(difluoromethyl)-4-(2-methylpropyl)-6- (trifluoromethyl)-S,S-dimethylester; 3-pyridinecarboxylic acid; 2-(difluoromethyl)-5-(4,5- dihydro-2-thiazolyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-, methyl ester; 3- pyridinecarboxylic acid; 2-(difluoromethyl)-4-(2-methylpropyl)-5-(lH-pyrazol- 1 - ylcarbonyI)-6-(trifluoromethyl)-, methyl ester; 5-methyl-4-methoxycarbonyl-3-methoxy- carbonylphenoxy)-pyrazole; and 5-methyl-4-methoxycarbonyl-3(3'methoxyphenoxy) pyrazole.

Other herbicides include S-ethyl-N-cyclohexyl-N-ethylthiocarbamate (cycloate); S-ethyl hexahydro-lH-azepine-1-carbothioate (molinate); S-ethyl dipropylthiocarbamate (EPTC); -6-

S-4-chlorobenzyl diethylthiocarbamate (benthiocarb); S-ethyl dϋsobutylthiocarbamate (butylate); S-benzyl di-sec-butylthiocarbamate; S-propyl dipropylthiocarbamate (vernolate); S-propyl butylethylthiocarbamate (pebulate); S-benzyl N-ethyl N-(l,2-dimethylpropyl) thiocarbamate (esprocarb); S-benzyl dipropyl thiocarbamate (prosulfocarb); S-(O,O-diisopropyl phosphorodithioate) ester of N-(2 metcaptoethyl)benzenesulfonamide (bensulide); N-benzyl-N-isopropyltrimethylacetamide (butam); 2-chloroallyl diethyldithiocarbamate (CDEC); 2-sec-butyl-4,6-dinitrophenol (dinoseb); 2,6-dinitro-N,N- dipropylcumidine (isopropalin); N-(cyclopropylmethyl)-α,α,α, -trifluoro-2,6-dinitro-N- propyl-p-toluidine (profluralin); 2-(l ,2-dimethylpropylamino)-4-ethylamino-6-methylthio- 1,3,5-triazine (dimethametryn); 2-ethyl-5-methyl-5-(2-methylbenzyloxy)-l,3 dioxane; 2-(2'- nitro-4'-methylsulfonylbenzoyl)-l,3-cyclohexanedione (mesotrione); and 2-(2-chloro-4- methylsulfonylbenzoyl)-l,3-cyclohexanedione (sulcotrione).

Illustrative of the insecticides are:

S-tert-butylthiomethyl O,O-diethyl phosphorodithioate (terbufos); O,O- diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate (diazinon); O,O-diethyl S- 2-ethylthioethyl phosphorodithioate (disulfoton); S-chloromethyl O,O-diethyl phosphorodithioate (chlormephos); O-ethyl S,S-dipropyl phosphorodithioate (ethoprophos); O,O- diethyl S-ethylthiomethyl phosphorodithioate (phorate), O-(4-bromo-2-chlorophenyl) O- ethyl S-propyl phosphorodithioate (prophenofos); S-l,2-di(ethoxycarbonyl)ethyl O,O- dimethyl phosphorodithioate (malathion); O,O,O',O'-tetraethyl S,S'-methylene di(phosphoro dithioate) (ethion); O-(4-bromo-2,5-dichlorophenyl) O,O-diethyl phosphorothioate (bromophos-ethyl); S-4-chlorophenylthiomethyl O,O-diethyl phosphorodithioate (carbophenothion); 2-chloro-l-(2,4-dichlorophenyl)vinyl diethyl phosphate (chloφhenvinphos); O-2,5-dichloro-4-(methylthio)phenyl O,O-diethyl phosphorodithioate (chlorthiophos); O-4-cyanophenyl O,O-dimethyl phosphorothioate (cyanophos); O,O- dimethyl O-2-methylthioethyl phosphorothioate (demephion); O,O-diethyl O-2- ethylthioethyl phosphorothioate (demeton); O-2,4-dichlorophenyl O,O-diethyl phosphorothioate (dichlorofenthion); O-2,4-dichlorophenyl O-ethyl phenylphosphonothioate (EPBP); O,O-diethyl O-5-phenylisoxazol-3-yl phosphorothioate (isoxathion); l,3-di(methoxycarbonyl)-l-propen-2-yl dimethyl phosphate; S,S'-(1,4- dioxane-2,3-di-yl) O,O,O',O'-tetraethyl di(phosphorodithioate) (dioxathion); O,O-dimethyl- O-(4-nitro-m-tolyl) phosphorothioate (fenitrothion); O,O-dimethyl O-4-methylthio-m-tolyl phosphorothioate (fenthion); O-(5-chloro-l-isopropyl-l,2,4-triazol-3-yl) O,O-diethyl phosphorothioate (isazophos); S-2-isopropylthioethyl O,O-dimethyl phosphorodithioate (isothioate); 4-(methylthio)phenyl dipropyl phosphate (propaphos); l,2-dibromo-2,2- dichloroethyl dimethyl phosphate (naled); O,O-diethyl 2-cyanobenzylideneamino- oxyphosphonothioate (phoxim); O,O-diethyl O-4-nitrophenyl phosphorothioate (parathion); O-2-diethylamino-6-methylpyrimidin-4-yl O,O-diethyl phosphorothioate (pirimiphos-ethyl); O-2-diethylamino-6-methylpyrimidin-4-yl O,O-dimethyl phosphorothioate (pirimiphos-methyl); (E)-O-2-isopropoxycarbonyl-l-methylvinyl O- methyl ethylphosphoramidothioate (propetamphos); O,O,O',O'- tetraethyldithiopyrophosphate (sulfotep); O,O,O',O'-tetramethyl 0,0-thiodi-p-phenylene diphosphorothioate (emephos); S-2-ethylthioethyl O,O-dimethyl phosphorodithioate (thiometon); O,O-diethyi O-(l-phenyl-lH-l,2,4-triazol-3-yl) phosphorothioate (triazophos); O-ethyl O-(2,4-5-trichlorophenyl) ethylphosphonothioate (trichloronate); O- ethyl-S-phenyl ethyl phosphonodithioate (fonofos); 3-(phenoxybenzyl)-(±)-cis, trans-3- (2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate (permethrin); (±) α-cyano-3- phenoxybenzyl (+)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylate (cypermethrin); (2,3,5,6-tetrafluoro-4-methylphenyl) methyl-(lα, 3α)-(Z)-(±)-3-(2-chloro- 3,3,3-trifluoro-l-propenyl)-2,2-dimethylcyclopropane carboxylate (tefluthrin); [lα(S*),3α(Z)]-( ^-<^ano-(3-phenoxyben^l)-3-(2-chloro-3,3,3-trifluoro-l-ρropenyl)-2,2- dimethylcyclopropane carboxylate (lambda-cyhalothrin); (S)-α-cyano-3-phenoxybenzyl-3- (2-chloro-3,3,3-trifluoro-l-propenyl)-2,2-dimethylcyclopropane carboxylate (cyhalothrin); (S)-α-cyano-3-phenoxybenzyl (lR,3R)-3- (2,2-dibromovinyl)-2,2-dimethylcyclopropane carboxylate (deltamethrin); α(lR,3S)3[l'RS)(l ',2',2',2'-tetrabromoethyl)]-2,2- dimethylcyclopropane carboxylate (S)-α-cyano-3-phenoxybenzyl ester (tralomethrin); (±)- 3-allyl-2-methyl-4-oxocyclopent-2-enyl (+)-ds,trans-chrysanthemate (allethrin); (±)-3-allyl- 2-methyl-4-oxocyclopent-2-enyl (H )-trans-chrysanthemate (bioallethrin); 3-phenoxybenzyl (+)-cis,trans-chrysanthemate (phenothrin); pyrethrins; 2-(2-butoxyethoxy)ethyl thiocyanate; isobornyl thiocyanoacetate (terpinyl thiocyanoacetate); 2-(4-tert-butylphenoxy)cyclohexyl -8- prop-2-ynyl sulfite (propargite); 4,6-dinitro-6-octylphenyl crotonates (dinocap); and ethyl 4,4'-dichlorobenzilate (chlorobenzilate).

Defoliants include S,S,S-tributyl phosphorotrithioate and tributyl phosphorotrithioite (meφhos).

Fungicides include copper naphthenates; 5-ethoxy-3-trichloromethyl- 1-2,4- thiadiazole (etridiazole); O-ethyl S,S-diphenyl phosphorodithioate (edifenphos); N- trichloromethyl-4-cyclohexene-l,2-dicarboximide (captan); and methyl (E)-2-{2-[6-(2- cyanophenoxy) pyrimidin-4-cyloxy]phenyl}-3-methoxy aerylate (azoxystrobin).

Insect repellents include 6-butoxycarbonyl-2,3-dihydro-2,2-dimethylpyran- 4-one (butopyronoxyl); N,N-diethyl-m-toluamide (deet); dibutyl phthalate; dibutyl succinate; l,5a,6,9,9a,9b-hexahydro-4a(4H)-diber-zofurancarboxaldehyde; and dipropyl pyridine-2,5-dicarboxylate.

The polymeric shell of the microencapsulated particles may be composed of any of those materials typically employed as shell materials in the pesticides field or other industry and which do not melt under the temperatures employed in the drying step. An overview of certain of such materials is provided in Scher, "Controlled Release Pesticides", ACS Symposium, Series 53 (1977), pp. 126-144. Similar polymers may be used in the production of microparticles.

Illustrative of the microencapsules which may be employed are polyurea materials produced in accordance with the process described in U.S. Patent 4,285,720. These polyurea walls are produced by heating or adding an appropriate catalyst to a water- immiscible material dispersed in an aqueous phase. The water-immiscible material contains one or more aromatic polyisocyanates, such as l-chloro-2,4-phenylene diisocyanate, m- phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-methylenebis (phenyl isocyanate), 2,4-tolylene diisocyanate, tolylene diisocyanate (60% 2,4-isomer, 40% 2,6-isomer), 2,6- tolylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 4,4'-methylenebis (2- -9- methylphenyl isocyanate), 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 2,2',5,5'-tetra- methyl-4,4'-biphenylene diisocyanate, 80% 2,4-and 20% 2,6-isomer of tolylene diisocyanate, or polymethylene polyphenylisocyanate (PAPI).

Another class of materials which may be employed are aminoplast microcapsules prepared in accordance with the process described in U.S. Patent 4,956,129. These microcapsules are prepared by (a) providing an organic solution comprising a substantially water insoluble liquid material and an etherified urea-formaldehyde prepolymer dissolved therein, in which from about 50% to about 98% of the methylol groups of the prepolymer have been etherified with C -Cιo alcohol; (b) creating an emulsion of the organic solution in a continuous phase aqueous solution comprising water and a surface active agent, wherein the emulsion comprises discrete droplets of the organic solution dispersed in the continuous phase aqueous solution, thus forming an interface between the discrete droplets of organic solution and the surrounding continuous phase aqueous solution; and (c) causing in situ self-condensation and curing of the urea-formaldehyde prepolymer in the organic phase of the discrete droplets adjacent to the interface by simultaneously heating the emulsion to a temperature between about 20°C to about 100°C, and adding an acidifying agent and maintaining the emulsion at a pH of between about 0 to about 4 for a sufficient period of time to allow substantial completion of in situ condensation of the resin prepolymers so as to convert the liquid droplets of said organic solution to capsules consisting of solid permeable polymer shells enclosing said liquid material.

A third illustrative class of polymeric walls which may be employed in microcapsules in the flakes of the present composition are those produced by the process described in U.S. Patent 3,577,515. In such process, the encapsulation of materials initially embodied, contained or carried in liquid is effected by interfacial polycondensation between coacting intermediates respectively in immiscible liquids, droplets of one liquid which is to be encapsulated and which contains one intermediate, being first established in a body of the other liquid. Thereafter the second intermediate is incoφorated in the other liquid to -10- produce minute capsules of the first liquid having a skin of polycondensate, e.g., polyamide, polysulfonamide, polyester, polycarbonate, polyurethane or polyurea.

A fourth type of polymer wall is a polyurea wall produced by condensation of an aromatic isocyanate with an amine, as described for instance in U.S. Patent 5,354,742. Still other types of polymeric walls are also described in U.S. Patent 5,354,742.

The spacer present in the flakes of the present invention may comprise any water-soluble or-insoluble solid. If a water-insoluble solid is used as a spacer, it will typically have a particle size of from about 0.01 to about 100 microns, preferably of between about 0.05 and about 15 microns. The spacer performs several functions. First, it serves as a drying matrix which both holds the capsules together to form a flake, yet separates the capsules or particles from one another. Secondly, it serves to promote dispersibility in water, functioning essentially as a wetting agent. Thirdly, it serves as a lubricant in the production of the flakes during drying, as described below, facilitating their removal from the heated surface.

Some substances, notably surfactants, may perform these functions in addition to the surfactant functions described below. If that is the case, a single material may function as both spacer and surfactant. However, for surfactants which cannot perform all functions needed of a spacer, a separate spacer material will be included. Alternatively, a lower priced spacer material could be used in place of a portion of a higher priced surfactant to reduce cost.

For use with pesticides, the spacer may compromise a pesticidally active or pesticidally inactive material. Illustrative of the inactive materials which may be employed are fuller's earth, kaolin clays, bentonite, kieselguhr, dolomite, calcium carbonate, talc, powdered magnesium oxide, gypsum and inorganic salts such as sodium chloride. These or other inactive materials may be suitable as spacers for other types of encapsulated ingredients. -11-

A wide variety of pesticides, especially herbicides, or growth regulants can be used as the spacer component of the compositions of this invention. Such herbicides and growth regulants are from various classes of compounds including various water- soluble and water-insoluble derivatives of ureas, triazines, carbamates and the thio-, dithio- and thiol- variations thereof, acetamides, acetanilides, diphenyl and dinitrophenyl ethers, imidazolidines, N-phosphonomethylglycine (glyphosate), pyrazoles, pyridines, etc. Of particular interest and preference as the non-encapsulated herbicidal or plant growth regulator component of the water-dispersible granules of this invention are the water- soluble salts of glyphosate, particularly the mono-alkali metal, amine or ammonium salts, and the water-insoluble compounds 2-chloro-4-ethylamino-6-isopropylamine-l,3,5-triazine (atrazine), 2-[4,5-dihydro-4-methyl-4-(l-methylethyl)-5-oxo-lH-imidazol-2-yl]-3-quinoline carboxylic acid (imazaquin) and benzoylcyclohexanediones such as 2-(2'-nitro-4'- methylsulfonylbenzoyl)-l,3-cyclohexanedione and metal chelates of them.

Other suitable herbicides useful as the non-encapsulated component of the water-dispersible granules of this invention include, by common name, the following: ametryne, aminotriazole, ammonium sulphamate, barban, bentazone, benzthiazuron, bifenox, bromacil, bromofenoxim, bromophos-ethyl, bromoxynil, bromoxynil octanoate, brompyrazone, butylate, chloramben, chloroxuron, chlorthal-dimethyl, chlorthiamid, chlortoluron, cyanazine, cycluron, dalapon, desmedipham, 2,4-D, desmetryne, dicamba, dichlorbenil, dichloφrop, dinitramine, dinoterb, diquat, diuron, DSMA, EPTC, fenoprop, fenuron, flumeturon, isoproturon, linuron, maleic hydrazide, MCPA, MCPB, metamitron, methabenzthiazuron, methazole, metoxuron, metribuzin, monolinuron, monuron, naptalam, neburon, paraquat, picloram, propanil, propachlor, propazine, pyrazon, siduron, simazine, simetryne and 2,4,5-T.

It is one aspect of this invention that certain of the above-mentioned water- insoluble herbicides used as the non-encapsulated component may be used in alternative embodiments as the encapsulated component of the water-dispersible granules and vice- versa. The capsules may contain two pesticidal ingredients, with a third pesticide employed as a spacer. For instance, the encapsulated material may comprise a solid pesticide -12- suspended in a second liquid pesticide, while a third pesticide may be used as the spacer material. When the overall product contains more than one pesticide, the pesticides may have similar activity (e.g., all may be herbicides) or may have different activity (e.g., the product may contain various combinations such as herbicide and fungicide, herbicide and insecticide, fungicide and insecticide and insect growth regulator, etc.).

Certain solid herbicides, e.g., N-(3,4-dichlorophenyl)-N¹-methoxy-N'- methyl-urea (linuron) or 4-amino-6-tert-butyl-3-(methylthio-as-triazine-5-(4H)one (metribuzin) when used as the encapsulated component, cannot be encapsulated directly, but can be solubilized by or suspended in the water-insoluble co-pesticide(s) or solvent and the mixture then encapsulated.

Representative insecticidal pesticides which are non-encapsulated but may be included together with the encapsulated water-insoluble herbicide include, e.g., the following: abamectin, aldicarb, acephate, aldrin, aminocarb, azinphos, bendiocarb, carbaryl, chlormephos, DDT, dicofol, diflubenzuron, endothion, fenvalerate, heptachlor, methiocarb, methomyl, methyl-and ethyl-parathion, permethrin, cypermethrin, pyrethrin, terbufos, etc.

Representative fungicidal pesticides which are non-encapsulated but may be included with the above encapsulated herbicides and/or insecticides include the following: anilazine, benodanil, benomyl, butacarb, captafoL, captan, carboxin, chloranil, chlorbromuron, chloroneb, chlorthalonil, chlorquinox, dazomet, dichlofluanid, diclone, dichloraphen, dichloran, dithianon, dodine, ferbam, folpet, mancozeb, maneb, tbiabendazole, thiram, zineb, ziram, etc. Other fungicides which are low-melting may be included together with low-melting insecticides and herbicides or plant growth regulants as the microencapsulated component of the water-dispersible granule. Examples of such fungicides are dinocat, edifenphos and pyrazophos. -13-

Representative nematicides which may serve as the encapsulated component herein include, e.g., terbufos, fensulfothion, carbofuran, ethoprop, fenamiphos, dichloro- propen, aldicarb and oxamyl.

Representative miticides which may be used in the encapsulated component of the present water-dispersible granules include, e.g., formetanate hydrochloride, omite, profenofos dimethoate, ethion, dinocapdicofol, amitraz, oxythioquinox, cyhexatin, fenbutatinoxide, oxamyl and phosalone.

Representative safeners (antidotes) for use with herbicides which are specifically contemplated as being suitable for use in the water-dispersible granules of this invention include, e.g., 5-thiazolecarboxylic acid, 2-chloro-4-(trifluoromethyl), (phenylmethyl) ester, (flurazole); N-dichloroacetyl-l-oxa-4-azaspiro [4,5] decane (AD-67); N-dichloroacetyl-N-N-diallyl acetamide (R-25788); N-dichloroacetyl-2,2-dimethyl-l,3- oxazolidine; N-dichloroacetyl-2,2,5-trimethyl-l,3-oxazolidine (R-29148); 2-[(cyano- methoxy)imino]benzenacetonitrile; 2-[(l,3-dioxypyran-2-yl-methoxy)-imino] benzeneacetonitrile; ethanone; 2,2-dichloro-l-(l,2,3,4-tetrahydro-l-methyl-2-isoquinolyl)-, and the like.

Representative plant growth regulants contemplated herein primarily for use as the non-encapsulated component in water-dispersible granules include: chlormequat chloride, calcium arsenate, diaminozide, ethofumesate, ancymidol, dikegulac sodium, ethephon, XE 1019, maleic hydrazide, flmprimidol, mefluidide, paclobutrazol, fluridamidel, amidichlor, sulfometuron methyl.

The water-dispersible granules of this invention may comprise mixtures of an encapsulated pesticide or microparticles containing a pesticide, and a non-encapsulated safener, or mixture of safeners.

The flakes of this invention may be prepared by (a) mixing an aqueous dispersion of the microcapsules or microparticles with spacer material(s) and/or one or -14- more water-soluble solid surfactants to form a dispersion; and (b) drying the dispersion by thin-layer drying.

The surfactant(s) employed in the present invention may be nonionic, anionic, cationic or amphoteric, and must be selected from those which are in liquid or molten form at the temperatures utilized in drying or removal of the dried product. Care should be taken to avoid using surfactants which are so hydrophobic so as to be able to extract the encapsulated material.

Suitable surfactants of the cationic type include, for example, quaternary ammonium compounds, for example, cetyltrimethyl ammonium bromide. Suitable surfactants of the anionic type include, for example, soaps, salts or aliphatic monoesters of sulfuric acid, for example, sodium lauryl sulfate, salts of sulfonated aromatic compounds, for example, sodium dodecylbenzenesulfonate, sodium, calcium or ammonium lignosulfonate, or butylnaphthalene sulfonate, and a mixture of the sodium salts of diisopropyl- and triisopropylnaphthalene sulfonates. Suitable surfactants of the nonionic type include, for example, the condensation products of ethylene oxide with fatty alcohols such as oleyl alcohol or cetyl alcohol, or with alkyl phenols such as octyl phenol, nonylphenol and octyl cresol. Other nonionic surfactants include ethylene oxide-propylene oxide block copolymers, partial esters derived from long chain fatty acids and hexitol anhydrides, and condensation products of these partial esters with ethylene oxide.

Typically the aqueous dispersion to be dried will contain from about 25 to about 70 weight percent of solids (microcapsules and spacer and/or surfactant material), with the weight ratio of spacer and/or surfactant material to microcapsules ranging from about 1:20 to about 20:1, preferably from about 1:15 to about 1:3. Typically, from about 1 percent to about 90 percent by weight, preferably from about 3 to about 15 percent by weight, on a dry product basis, of surfactant will be included.

The thin-layer drying (also known as "thin-film drying") used to produce the products of this invention may be any of such techniques known in the art. In such -15- processes the material to be dried is fed to a heated surface in the form of a relatively thin film, and the liquid (e.g., water) is removed by the heat generated and/or by a stream of air or inert gas.

A preferred method of thin-layer drying utilized in this invention is drum or roll drying, particularly one in which the capsule or microparticle suspension is fed onto and between two drums, rotating inward towards each other. The emulsion forms a film on the surfaces of the drums, which passes through the space between them and is dried on the drum surfaces. Other forms of drum or roll drying such as single-roll drying, in which the suspension is taken over the heated roll by immersion or is fed or sprayed onto the roll from above, may also be employed. Other techniques may be used, for example, spreading the suspension onto a flat heated surface or a heated moving belt, or wiped-film evaporation.

The product flakes are recovered from the heated surface by scraping, shaking, etc., at a temperature at which any surfactant used is still in liquid or molten form. The removal may be done continuously (for example, using continuously scraped drum dryers) or batchwise (for example, by scraping or vibrating a heated flat surface). Similarly, the drying step may be carried out continuously or batchwise.

The thin layer or film can have any dimensions which will serve to produce the desired flakes using the particular equipment selected. Preferably the film will have a thickness of up to about 3 times the maximum desired thickness of the product flakes, or a thickness of from about 0.075 to about 6 mm.

The drying temperature will depend on the nature of the encapsulated or microparticle material and spacer/surfactant materials, and should be such as to produce economic and efficient drying without causing decomposition or degradation of the encapsulated material. Generally, temperatures of from about 20°C to about 200°C, preferably from about 50°C to about 150°C, most preferably from about 70°C to about 100°C, may be used. The aforementioned temperatures refer to the temperature of the product rather than that of the surrounding environment. If the encapsulated material is -16- heat-sensitive, the process may be carried out at lower pressures by employing a vacuum outside the drum. In general, the pressure may range from atmospheric to below atmospheric (under vacuum).

One advantage of this process is that it can produce dried dispersible microcapsule or microparticle products from more concentrated or more viscous suspensions than may be used in spray-drying processes, so long as the viscosity of the suspension is not so high as to interfere with the formation of the thin layer or film on the heated dryer surface.

The flakes of this invention typically will be less likely to agglomerate when subject to compaction forces. Such flakes also tend to be less dusty than spherical formulations and more readily dispersible than extruded formulations.

The following examples are intended to further illustrate the invention and are not intended to limit the scope of the invention in any manner whatsoever.

EXAMPLE 1

In a 1 liter vessel with a blade disperser, the following formulations (listed below 1 A to E) were prepared and stirred at medium speed (2,000 to 3,000 φm) until the solutions were homogenized. Formulations 1 A - IE contained polyurea microcapsules containing about 80 weight % alachlor produced by Monsanto Company under the trademark Lasso® Micro-Tech®.

The formulations were processed, in turn, over a laboratory atmospheric double drum dryer. The laboratory unit was a 6" dia.x7 5/8" long model. The drums were arranged to turn inward and down through the pinch. They were driven by a motor to give a drum speed of 0.5 to 13 rpm. The drums were rotating at a rate of from 0.75-3.5 rpm with a gap of 1.1 mm. The steam supply was set at pressures from 15 to 20 psig, providing a surface temperature ranging from 120° to 126° C. -17-

FORMULA A B C D E

Microcapsules in water (60 wt%) 500 500 500 500 500 Daxad 23 (Dispersant) 20 15 10 5 Talcum (Lubricant) 5 5 5 5 Pluronic F108 (Nonionic Surfactant) 5 5 10

Total (grams) 520 520 520 520 520

Steam Pressure (psig) 15 15 16 19 20

Drum Speed (φm) 0.75 0.75 0.75 1.0 1.0

Gap (mils) 7 7 7 7 10

The slurries were fed into the gap between the drums with a variable speed peristaltic pump. The flow of liquid was increased progressively into the gap until a uniform film was obtained on the surface of the drums. The dried film was scraped with knives and collected in receiving pans. The dried products were obtained in a non-dusty form with particles shaped in thin flakes. The flakes had sizes ranging from 1 to 10 mm in length with thickness of between 0.05 to 2.0 mm.

The flakes produced from each run were tested for their dispersibility as follows:

In a dispersion tube (250 ml) with tapered, graduated bottom and stopper filled with 200 grams of water, 2 grams of the product (preweighed) were poured into the water, then the tube was quickly stoppered. The tube was then immediately inverted at a 180-degree angle, held for 5 seconds, and returned to normal. The inversions were repeated up to 20 full cycles. The tube was left standing up for about 5 minutes and checked for sedimentation.

No sedimentation was observed for any sample. The solution was sampled and observed under a microscope. Observations showed no damaged capsules. Samples were rated for redispersibility by visual inspection of the material in the dispersion tube and inspection of that material under a microscope. -18-

Evaluations of products obtained in example 1 showed redispersion of all samples in water.

EXAMPLE 2

An aqueous suspension of aminoplast microcapsules containing the herbicide acetochlor (66.6 wt. %) and safener dichlormid (R-25788) (11.4 weight %), plus adjuvants, was prepared. The capsule suspension contained 58.50 wt. % microcapsules and 41.50 wt. % water and dissolved materials. The following formulations 2A-2E were then prepared in a 1 liter vessel, and were stirred at 2000-3000 rpm until they were homogenized.

The formulations were processed, in turn, over a laboratory atmospheric double drum dryer as described in Example 1.

FORMULA 2A 2B 2C 2D 2E

Microcapsule Feed

(58.5 wt % in water) 780 780 780 780 780

Morwet IP (dispersant) 20 20 20 20 40

Pluronic F108

(nonionic surfactant) — 10 10 10 —

Zeofree 80 (silica) — 10 — — —

Talcum — — ~ 10 —

TOTAL (grams) 800 820 810 820 785

Drum Speed (rpm) 4.5 4.5 2.5 2.5 2.5

Surface Temp. (C) 132 132 132 132 132

Gap (mils) 7 8 8 8 8

The dried products were non-dusty and the size of the flakes ranged from 1.0 to 5 mm in length with thickness of between 0.05 to 1.0 mm. All examples redispersed in water. -19- EXAMPLE 3

The following formulations (listed below 3 A to 3E) were prepared from the same microcapsule suspension used in Example 2, and were stirred at medium speed (2,000 to 3,000 φm) until homogenized.

FORMULA 3A 3B 3C 3D 3E

Microcapsule Feed

(58.5 wt % in water) 725 560 560 560 650

Morwet IP (dispersant) 20 12.5 ~ ~ —

Pluronic F108

(nonionic surfactant) 29 — « — —

Carbowax 8000 NF

(wetting agent) — 20 20 20 —

Daxad 23 — — 12.5 — 12

Reax 85 (dispersant) — — — 12.5 ~

Sodium Chloride 20 15 15 15 —

Calcium Chloride 20 15 15 15 —

Talcum ~ — - — _ 5

Water (viscosity reducer) 100 200 100 100 —

TOTAL (grams)

Drum Speed (φm) 3.0 2.5 2.5 2.5 3.0

Surface Temp. (C) 125 125 125 125 120

Gap (mils) 8 8 8 8 8

The dried products were non-dusty and the size of the flakes ranged from 1.0 to 5 mm in length with thickness of between 0.05 to 1.0 mm. All examples redispersed in water.

EXAMPLE 4

The following acetochlor formulations (listed below 4A to E) were prepared from the same microcapsule suspension used in Example 2, and stirred at medium speed (2,000 to 3,000 rpm) until homogenized. -20-

FORMULA A B C D E

Microcapsule Feed

(58.5 wt % in water) 685 555 555 555 555

Morwet IP (dispersant) 12.5 10 10 10 10

Igepal DM970

(nonionic surfactant) — 20 20 20 ~

Carbowax 8000 NF

(wetting agent) 20 — — — —

Sodium Chloride 15 20 — 12.5 10

Calcium Chloride 15 ~ 25 12.5 15

TOTAL (grams) 147 605 610 610 600

Drum Speed (φm) 2.5 1.5 1.5 1.5 1.5

Surface Temp. (C) 125 125 125 125 125

Gap (mils) 8 6 6 6 6

The dried products were non-dusty and the size of the flakes ranged from 1.0 to 5 mm in length with thickness of between 0.05 and 1.0 mm. All examples redispersed in water.

The flakes were analyzed for acetochlor and R-25788 contents and results are shown below:

FLAKES FROM EXAMPLE 4A 4B 4C 4D 4E

Acetochlor Assay Wt % 57.8 57.6 58.9 58.3 61.3

R-25788 Assay Wt % 9.8 9.8 10.1 10.0 10.5 -21- BIOLOGICAL EVALUATION

Products obtained from Examples 4A - 4E were tested for biological efficacy in comparison with an acetochlor product produced by spray-drying similar microcapsules, four samples of dispersions prepared from aqueous suspensions of polyurea microcapsules containing acetochlor which had not been dried, and one liquid product (emulsifiable concentrate) containing acetochlor without a safener.

The products were diluted with water and applied preemergence to containers seeded respectively with corn and with soybeans and in which seeds of the following weeds had also been planted: morning glory (Ipomoea sp., IPOSS), white proso millet (Panicum miliaceum. PANMI), shattercane (Sorghum bicolor. SORVU), bamyardgrass (Echinochloa crusgalli. ECHCG) and wooly cupgrass (Eriochloa villosa. ERBVI).

All products were appropriately diluted and applied to the flats at application rates (of acetochlor) ranging from 1.56 to 6400 grams per hectare as listed below in the following Tables 1 and 2. Weed control and injury to com and soybeans was rated twice — at 9 days after application of the acetochlor (Table 1) and at 20 days after application (Table 2).

-22-

TABLE I - 9 DAYS AFTER APPLICATION

Acetochlor CORN SOY IPOSS PANMI SORVU ECHCG ε/ha

Capsule 1.56 3 0 0 5 5

Suspension 6.25 5 0 5 0 30

Sample I 25 2 5 3 20 23 93

100 4 3 20 85 85 95

400 4 18 10 85 93 99

1600 4

6400 4

Capsule 1.56 3 0 0 0 0

Suspension 6.25 1 10 3 1 8

Sample II 25 4 0 15 18 23 97

100 5 3 5 90 93 97

400 1 35 43 85 95 99

1600 1

6400 4

Capsule 1.56 0 18 0 0 0

Suspension 6.25 3 18 0 0 5

Sample III 25 2 3 5 8 25 90

100 1 13 15 93 88 97

400 3 23 30 88 95 99

1600 2

6400 8

Capsule 1.56 3 18 0 0 0

Suspension 6.25 3 18 5 0 55

Sample IV 25 5 3 13 53 45 93

100 1 5 15 97 90 95

400 8 33 23 88 9 99

1600 1

6400 8

Invention 1.56 3 18 0 0 0

Example 4A 6.25 3 18 0 0 0

25 4 3 13 5 5 90

100 3 3 15 80 68 97

400 0 5 23 97 90 98

1600 1

6400 1

Invention 1.56 0 8 0 0 0

Example 4B 6.25 3 8 0 0 5

25 4 3 5 23 5 85

100 1 23 0 78 78 97

400 1 3 20 95 95 98

1600 3

6400 5

Invention 1.56 3 10 5 0 0

Example 4C 6.25 3 8 0 0 0

25 4 0 18 0 0 93

100 1 3 15 38 75 97

400 2 10 23 95 93 98

1600 1

6400 13

(Continued) -23-

TABLE I (Continued)

Acetochlor CORN SOY IPOSS PANMI SORVU ECHCG g/ha

Invention 1.56 5 18 0 0 3

Example 4D 6.25 3 0 13 0 0 0

25 0 0 8 10 0 88

100 0 5 15 63 73 97

400 4 13 13 95 90 97

1600 5

6400

Invention 1.56 0 5 0 0 0

Example 4E 6.25 0 8 0 0 0

25 5 3 8 15 13 93

100 0 8 8 75 90 97

400 1 35 28 97 93 98

1600 1

6400 3

Spray Dried 1.56 3 10 0 0 3

Capsules 6.25 0 13 0 0 0

25 4 10 8 0 0 88

100 3 8 3 38 73 97

400 6 10 10 95 90 97

1600 1

6400 5 —

Emulsifiable 1.56 8 3 0 0 3

Concentrate, 6.25 5 13 0 0 10

No Safener 25 0 0 25 28 45 93

100 2 15 15 45 90 97

400 2 40 5 93 95 98

1600 10

6400 10

-24-

TABLE π - 20 DAYS AFTER APPLICATION

Acetochlor CORN SOY BPOSS PANMI SORVU ECHCG ERBVI g ha

Capsule 1.56 0 0 0 0 0 0

Suspension 6.25 0 0 5 0 0 5

Sample I 25 0 0 0 15 8 100 15

100 0 0 0 97 94 100 65

400 0 13 0 93 100 100 99

1600 3

6400 0

Capsule 1.56 0 0 0 0 0 0

Suspension 6.25 0 0 0 0 0 0

Sample II 25 0 0 0 10 20 99 5

100 0 0 0 94 100 100 93

400 3 43 0 88 100 100 83

1600 0

6400 1

Capsule 1.56 0 0 0 0 0 0

Suspension 6.25 0 0 0 0 0 0

Sample III 25 0 0 0 10 0 98 0

100 0 0 0 99 97 100 73

400 0 18 0 90 100 100 97

1600 4

6400 8

Capsule 1.56 0 0 0 0 0 0

Suspension 6.25 0 0 0 0 63 0

Sample IV 25 0 0 0 38 33 97 0

100 0 0 0 100 97 100 93

400 4 13 0 95 100 100 93

1600 2

6400 2

Invention 1.56 0 0 0 0 0 0

Example 6.25 0 0 0 0 0 0

4A 25 0 0 0 0 0 93 0

100 0 0 0 83 48 100 60

400 1 15 0 100 88 100 93

1600 5

6400 4

Invention 1.56 0 0 0 0 0 0

Example 4B 6.25 0 0 0 0 0 0

25 0 0 0 0 0 88 0

100 0 15 0 80 80 100 65

400 0 0 0 98 98 100 95

1600 0

6400 1

Invention 1.56 0 0 0 0 0 0

Example 4C 6.25 0 0 0 0 5 0

25 0 0 0 0 0 95 0

100 0 0 0 43 75 99 95

400 0 18 0 100 100 100 97

1600 3

6400 4

(Continued) -25-

TABLE II (Continued)

Acetochlor CORN SOY DPOSS PANMI SORVU ECHCG ERBVI g/ha

Invention 1.56 0 0 0 0 0 0

Example 4D 6.25 0 0 0 0 0 0

25 0 0 0 0 0 75 0

100 0 5 0 60 78 100 88

400 0 5 0 100 100 100 95

1600 16

6400 0

Invention 1.56 0 0 0 0 0 0

Example 4E 6.25 0 0 0 0 0 0

25 1 0 0 0 0 95 0

100 0 0 0 78 95 100 88

400 0 25 0 100 100 100 95

1600 0

6400 1

Spray Dried 1.56 0 0 0 0 0 0

Capsules 6.25 0 0 0 0 0 0

25 0 0 0 0 0 75 0

100 0 0 0 30 68 98 93

400 0 8 0 100 95 100 93

1600 2

6400 1

Emulsifiable 1.56 0 0 0 0 0 0

Concentrate, 6.25 5 0 0 0 10 0

No Safener 25 0 0 0 43 35 97 15

100 1 18 0 33 83 100 90

400 1 28 0 100 100 100 95

1600 4

6400 10

Although the invention has been described with reference to preferred embodiments and examples thereof it is not intended that the present invention be limited to only those described embodiments. The description of the preferred embodiments contained herein is intended in no way to limit the scope of the invention. As will be apparent to a person skilled in the art, modifications and adaptations of the above-described invention will become readily apparent without departure from the spirit and scope of the invention, the scope of which is defined and circumscribed by the appended claims.

Claims

-26- CLAIMS

1. A water-dispersible flake comprising a plurality of microcapsules or microparticles containing one or more encapsulated ingredients, said microcapsules or microparticles being held together in flake form by spacer material and/or one or more surfactants.

2. A flake according to Claim 1 containing microcapsules, wherein the shells of the microcapsules are composed of a polyurea material.

3. A flake according to Claim 1 containing microcapsules, wherein the shells of the microcapsules are composed of an aminoplast material.

4. A flake according to Claim 1 wherein the encapsulated ingredients comprise one or more pesticides.

5. A flake according to Claim 4 wherein the encapsulated ingredients comprise one or more herbicides.

6. A flake according to Claim 5 wherein the encapsulated ingredients comprise acetochlor.

7. A flake according to Claim 4 wherein the encapsulated ingredients comprise one or more insecticides.

8. A flake according to Claim 7 wherein the encapsulated ingredients comprise a pyrethroid.

9. A flake according to Claim 8 wherein the pyrethroid is lambda- cyhalothrin. -27-

10. A flake according to Claim 1 wherein the spacer material comprises one or more nonencapsulated pesticides.

11. A flake according to Claim 10 wherein the spacer material comprises atrazine.

12. A flake according to Claim 1 in which the microcapsules or microparticles are held together by a spacer and one or more surfactants.

13. A method for producing a water-dispersible flake comprising a plurality of microcapsules or microparticles containing one or more encapsulated ingredients, said microcapsules or microparticles being held together by spacer material and/or one or more surfactants, comprising the steps of:

a) mixing an aqueous suspension of said microcapsules or microparticles with spacer material and/or a surfactant to form a dispersion; and

b) drying the dispersion by thin-layer drying on a heated surface; and

14. A method according to Claim 13 in which at least one of steps (b) and (c) is conducted continuously.

15. A method according to Claim 13 in which one or more solid surfactants which are in molten form at the temperature of step (b) is utilized.

16. A method according to Claim 13 in which step (b) is conducted at a temperature of from about 20┬░ C to about 200┬░ C.