AU672465B2

AU672465B2 - Microcapsule formulations of agricultural chemicals

Info

Publication number: AU672465B2
Application number: AU56813/94A
Authority: AU
Inventors: George Bernard Beestman
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1992-12-04
Filing date: 1993-12-02
Publication date: 1996-10-03
Anticipated expiration: 2013-12-02
Also published as: WO1994013139A1; AU5681394A; JPH08504206A; CA2150920A1; EP0671878A1

Description

TΓΓLE

MICROCAPSULE FORMULATIONS OF AGRICULTURAL CHEMICALS

BACKGROUND OF THE INVENTION

The present invention comprises novel compositions and processes directed to the preparation of microcapsule formulations containing random co- or ter-polymers of vinylpyrrolidone as an emulsifier to form an oil-in-water emulsion.

U.S. 4,208,833 teaches the use of lignosulfonates as useful emulsifiers for high concentration microencapsulated formulations. However, the microcapsules settle out and irreversibly pack in the bottom of spray tanks and in spray lines upon dilution with water. In contrast, the microcapsules of the present invention, which comprise a novel type of emulsifier, readily resuspend upon dilution with water.

SUMMARY OF THE INVENΗON This invention comprises a composition comprising highly concentrated microencapsuled pesticides suspended in an aqueous liquid, said microencapsuled pesticides comprising a liquid, melted solid or solution of an active pesticide in an unreactive water-immiscible solvent within an encapsulating wall of polymeric material wherein:

(a) said active pesticide being present at a concentration ranging from about 480 to about 700 grams per liter of composition; (b) said encapsulating wall of polymeric material is the reaction product of a first shell wall component which is a difunctional or polyfunctional reactant soluble in the active pesticide, and a second shell wall component which is water-soluble and which is a difunctional or polyfunctional reactant and wherein the concentrations of said first and second shell wall components are from about 3.5% to about 21.0% and from about 1.5% to about 9.0%, respectively, by weight relative to the weight of the active ingredient to be encapsulated; and

(c) said aqueous liquid is water comprising

(i) from about 0.5% to about 15% by weight of an emulsifier relative to the weight of said active ingredient to be encapsulated, said emulsifier being a water-soluble random co- or ter-polymer of vinylpyrrolidone, and (ii) optionally, from about 0.01% to about 30% of a formulation adjuvant based on the total weight of the composition. This invention also comprises a process for preparing a highly concentrated composition of particles of a microencapsulated pesticide in water wherein the pesticide is encapsulated in a plastic shell with substantially no agglomeration of the particles, said process comprising (a) mixing a water-immiscible monomer A and an active pesticidal ingredient, in the form of a liquid, melted solid or solution of said active ingredient in an unreactive water-immiscible solvent, said monomer selected from the group consisting of diacid and polyacid chlorides, dichloroformates, polychloroformates, disulfonyl and polysulfonyl chlorides, diisocyanates, polyisocyanate and mixtures thereof, to form a solution of monomer in the active ingredient;

(b) dispersing in water containing an emulsifier, the solution of the monomer and active ingredient, said emulsifier being a water-soluble random co- or ter-polymer of vinylpyrrolidone, to form a water in oil emulsion with droplets in the size range of 1 to 100 microns;

(c) adding to the emulsion of (b) a water-soluble monomer B which will react with monomer A by interfacial polycondensation to form a shell around the pesticidal ingredient, said water-soluble monomer B selected from the group consisting of diamines or polyamines, diols or polyols; or alternatively when monomer A is a diisocyanate, a polyisocyanate or mixtures thereof, optionally including a catalyst in the solution from (a) and heating the emulsion of (b) to hydrolyze monomer A to amine groups whereby the amine groups generated by hydrolysis react with residual isocyanate monomers to generate a shell wall of polyurea;

(d) optionally, adding formulation adjuvant(s); and (e) optionally, drying followed by granulation of the solid residue to form a flowable solid composition.

DETAILED DESCRIPTION OF THE INVENTION This invention comprises compositions containing and processes for producing small or minute capsules containing a water-immiscible pesticidal component. By a process called interfacial polycondensation, a monomeric first shell wall component (monomer A) is dissolved in a water-immiscible pesticide, or solution thereof. The resulting solution is dispersed in water containing an emulsifying polymer selected from co-polymers or ter-polymers of polyvinylpyrrolidone (PVP) to form an oil-in-water (O/W) emulsion. Thereafter, a second monomeric shell wall component (monomer B, usually dissolved in additional aqueous phase liquid) is added to the oil-in-water emulsion whereby the second shell wall component reacts with the first shell wall component to form a polycondensate shell wall about the water-immiscible material at the oil/water interface. High concentration suspensions containing a larger volume of pesticide components inside the microcapsules than the volume of water suspending the microcapsules, are produced by interfacial polycondensation.

In some instances, the second shell wall forming component is unnecessary. By a process called in situ microencapsulation, isocyanate monomers are dissolved in the water-immiscible pesticidal component, and the solution is dispersed in water containing an emulsifying polymer selected from co-polymers or ter-polymers of vinylpyrrolidone. Amine groups generated by hydrolysis react with residual isocyanate monomers, generating a shell wall of polyurea. A catalyst that will speed the hydrolysis of the isocynate may be included in the monomer in the active ingredient solution. These are well known in the art. One such catalyst is dibutyltin dilaurate. Heat is applied to also speed the hydrolysis. Generally, when a catalyst is used a temperature of 20° to 60°C is sufficient to carry out the hydrolysis in one hour. However, if the catalyst is not used a temperature of 58-75°C will require several hours, e.g., 12 hours for the hydrolysis. Microencapsulation is especially useful for making high concentration solid formulations of liquid pesticides. Without microencapsulation, unencapsulated liquids must first be absorbed onto inert carriers to create dry powders which can be granulated to dry solid water-dispersible formulations. With large amounts of inert carrier required to absorb liquids, solid dry formulations of unencapsulated liquids are necessarily dilute. Without microencapsultation, maximum quantities of unencapsulated liquid in dry solid formulations is about 40%. By contrast, microcapsules contain at least 90% liquid and can be formulated to dry solid formulations which may contain more than 70% liquid pesticide.

Once encapsulated, the liquid or other form of agricultural product (e.g., meltable solids) is preserved until it is released by some means or instrumentality that breaks, crushes, melts, dissolves, or otherwise removes the capsule skin or until release by diffusion is effected under suitable conditions. Microencapsulation reduces acute toxicity of pesticides, improves biological efficacy, may reduce leaching into groundwater, and can isolate incompatible pesticides from each other within the same formulation.

Despite these advantages, microencapsulation is not extensively utilized because early processes produced dilute compositions. Colloid stabilizers utilized to disperse the oil phase are effective only if the continuous aqueous phase is a larger volume than the dispersed oil phase. When colloid stabilizers are utilized for high concentration microencapsulation, microcapsule aggregates are produced.

We have discovered that certain emulsifiers, random co-polymers and ter- polymers of vinylpyrrolidone, can be advantageously used in the process of microencapsulation using an interfacial polycondensation reaction between reactive monomers within the oil and water phases, or in the process of in situ microencapsulation with isocyanate monomers contained in the oil phase. After dilution into water the settled microcapsules prepared by these processes are readily resuspended and do not agglomerate. The present invention provides new encapsulation processes which are effective to encapsulate high concentrations of water-immiscible agricultural products to provide high concentration suspensions of microcapsules, or dry dispersible formulations prepared by drying and granulation of the resulting solid microcapsules. A critical feature of the present invention is the use of the specific type of emulsifiers to form sufficiently stable oil-in-water emulsions so that a concentrated amount of agricultural product is present in the water-immiscible phase and is therefore encapsulated. Generally, there is greater than 480 grams of agricultural product or agricultural product solution per liter of total aqueous composition. Dry solid formulations contain greater than 70% liquid water-immiscible material in dry water- dispersible form.

The microcapsules of the present invention may contain dyes, inks, chemical agents, pharmaceuticals, flavoring materials, pesticides, biological agents, plant growth regulators, and the like. Any liquid, oil, meltable solid, or solvent soluble material into which shellwall monomers can be dissolved and which are nonreactive with the monomers may be encapsulated.

In the practice of the preferred embodiment of the present invention, the material to be encapsulated is a water-immiscible agricultural chemical. As indicated above, the agricultural chemical component is any liquid, oil, or meltable solid, to which the first shellwall monomeric component is unreactive. In addition, a water-immiscible agricultural chemical can comprise a solution of an agricultural chemical in an unreactive water-immiscible solvent.

The pesticidal component is selected from the group consisting of herbicides, insecticides, acaricides, fungicides, nematocides, bactericides, biological pest control agents, herbicide safeners and plant growth regulants. Examples of suitable agricultural chemicals include: herbicides such as acetochlor, acifluorfen, alachlor, asulam, atrazine, bensulfuron methyl, bentazon, bromoxynil, butachlor, hydroxybenzonitrile, chloramben, chlorimuron ethyl, chloroxuron, chlorsulfuron, chlorotuluron, clomazone, cyanazine, dazomet, desmediphan, dicamba, dichlorbenil, dichlorprop, diphenamid, dipropetryn, diuron, thiameturon, fenac, fluometuron, fluridone, fomesafen, glyphosate, imazamethabenz, imazaquin, imazethapyr, ioxynil, isoproturon, isouron, isoxaben, karbutilate, triallate, diallate, trifluralin, linuron, lenacil, MCPA, MCPB, mefluidide, methabenzthiauron, methazole, metolachlor, metribuzin, metsulfuron methyl, monuron, naptalam, neburon, nitralin, norflurazon, oryzalin, perfluidone, phenmedipham, prometryn, pronamide, propazine, pyrazon, rimsulfuron, siduron, simazine, sulfometuron methyl, tebuthiuron, terbacil, terbuthylazine, terbutryn, triclopyr, 2,4-D, 2,4-DB, triasulfiiron, tribenuron methyl, primisulfiiron, pyrazosulfuron ethyl, N-[[(4,6- _imeΛoxy-2-pyrin_tic_iιιyl)an-^ sulfonamide, nicosulfuron, 2^l-t-butyl-2-chloro-N-methoxymethyl-6'-methylacetanilide, α- chloro-N-(2-methoxy-6-methylphenyl)-N-( 1 -methylethoxymethyl)acetamide, α-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)-α-chloro-N-methyl-acetamide, isobutyl (2,4-dichlorophenoxy)acetate, 1 -( 1 -cyclohexen-1 -yl)-3-(2-fluorophenyl)- 1 - methyl urea, and ethametsulfuron methyl; fungicides such as carbendazim, thiuram, dodine, chloroneb, cymoxanil, captan, folpet, thiophanate-methyl, thiabendazole, chlorothalonil, dichloran, captafol, iprodione, vinclozolin, kasugamycin, thiadimenol, flutriafol, flusilazol, hexaconazole, and fenarimol; bactericides such as oxytetracycline dihydrate; acaricides such as hexathizox, oxythioquinox, dienochlor, and cyhexatin; insecticides such as carbofiiran, carbyl, thiodicarb, deltamethrin, methyl and ethyl parathion, pyrethrin, permethrin, fenvalerate, and tetrachlorvinphos; and herbicide safeners such as 5-thiazolecarboxylic acid.

The material to be encapsulated need not consist of only one pesticide, but may be a combination of two or more agricultural chemicals. For example, such a combination may be a herbicide with another active herbicide or a herbicide and an insecticide. Also contemplated is a water-immiscible material to be encapsulated which comprises an active ingredient, such as a herbicide, and a non-pesticidal ingredient such as an adjuvant or inert material to achieve some special property.

The water-immiscible agricultural product when in liquid form may act as the solvent for the first shellwall component, or especially when the agricultural product is a solid, the use of a water-immiscible organic solvent such as methylene chloride, alkanes, benzene, toluene, xylenes, etc., may be used. The use of a liquid agricultural product without additional organic solvent allows for a concentrated amount of active ingredient in the final encapsulated product. The water-immiscible agricultural product and first shellwall component are added simultaneously to the aqueous phase in a pre-mixed state. That is, the water-immiscible material and first shellwall component are pre-mixed to obtain a homogeneous organic liquid phase before addition to, and emulsification in, the aqueous phase to form the oil-in-water emulsion.

The concentration of water-immiscible agricultural product initially present in the water-immiscible phase should be sufficient to provide at least about 480 grams of water- immiscible agricultural product per liter of total aqueous composition. In practice, as is recognized by those skilled in the art, the use of extremely high concentrations of water- immiscible agricultural product results in undesirably thick suspensions of microcapsules. In general, the concentration of water-immiscible agricultural product ranges from about 480 grams to about 700 grams per liter of total aqueous composition. The preferred range is from about 480 grams to about 600 grams per liter of total aqueous composition.

The shellwall of polycondensate may be a polyurea, polyamide, polysulfonamide, polyester, polycarbonate, polyurethane or mixtures thereof. The following are specific instances of polycondensation reactions to which the present encapsulation process is applicable. Diamines or polyamines in the water phase react with diacid or polyacid chlorides in the organic phase liquid to yield capsule walls consisting of poly amides. Diamines or polyamines in the aqueous liquid condense with dichloroformates or polychloroformates in the organic liquid to form a polyurethane capsule skin. Diamines or polyamines in the aqueous liquid react with disulfonyl or polysulfonyl chlorides in the organic liquid to produce a polysulfonamide capsule skin. Diamines or polyamines in the aqueous phase liquid and a dϋsocyanate or polyisocyanate in the organic phase liquid react to form a polyurea skin. With diols or polyols in the aqueous liquid and diacid or polyacid chlorides in the organic phase liquid, polyester shellwalls are produced. When bischloroformates or polychloroformates are used in the organic liquid, the capsule skins are polycarbonates.

It will further be appreciated that not only are there other complementary intermediates which react to form polycondensates in a manner useful in the interfacial polycondensation process of encapsulation, but various mixtures of intermediates, i.e., mixtures of shellwall components, may be employed in either or both of the aqueous and organic phases. For example, mixtures of diols and diamines in the aqueous liquid and acid chloride(s) in the orgamc liquid are useful to achieve polyester olyamide condensation copolymers. Also, diamines or polyamines in the aqueous liquid and mixtures of diacid or polyacid chlorides and diisocyanates or polyisocyanates in the organic liquid produce a polyamide^>olyurea skin.

Examples of suitable difunctional acid-derived shellwall components suitable as monomeric components for the organic phase are sebacoyl chloride, ethylene bischloroformate, phosgene, terephthaloyl chloride, adipoyl chloride, azelaoyl chloride (azelaic acid chloride), dodecanedioic acid chloride, dimer acid chloride, and 1,3- benzenesulfonyl dichloride. Polyfunctional compounds of this character are exemplified by trimesoyl chloride, 1,2,4,5-benzene tetracid chloride, 1,3,5-benzene trisulfonyl chloride, trimer acid chloride, citric acid chloride, and 1,3,5-benzene trischloroformate. Monomers similarly useful in the orgamc phase include diisocyanates and polyisocyanates, for example, toluene diisocyanate, hexamethylene diisocyanate, methylene diphenylisocyanate and polymethylene polyphenylisocyanate.

Examples of suitable diols for use as monomers in an aqueous phase are bisphenol A [2,2 bis-(p, '-dihydroxy diphenyl)propane], hydroquinone, resorcinol, catechol, and various glycols such as ethylene glycol, pentanediol, hexanediol, dodecanediol, 1,4-butanediol and the like. Polyfunctional alcohols of this character, e.g., triols and polyols, are exemplified by pyrogallol (1 ,2,3-benzenetriol), phloroglucinol dihydrate, pentaerythritol, trimethylolpropane, 1, 4,9, 10-tetrahydroxy anthracene, 3,4-dihydroxyanthranol, diresorcinol and tetrahydroxyquinone. Suitable diamines and polyamines for use as monomers in an aqueous phase, usually selected as water-soluble per se or in water-soluble salt form, are ethylene diamine, phenylene diamine, toluene diamine, hexamethylene diamine, diethylene triamine and piperazine. Amines which are effective as polyfunctional reactants, are, e.g., 1,3,5- benzene triamine trihydrochloride, 2,4,6-triamino toluene trihydrochloride, polyethylene imine, 1,3,6-triaminonaphthalene, 3,4,5-triamino-l,2,4-triazole, melamine, and 1,4,5,8- tetramino anthraquinone. Amines which have greater than 2 but less than 3 amine functionalities and which may provide a degree of crosslinking in the shellwall are the polyalkylene polyamines of the type

R R

I I

H₂N(CH₂)_mCH — HΝ(CH₂)_nC»— H₂

wherein R equals hydrogen or CH3, m is 1-5 and n is 1-5, e.g., tettaethylene pentamine, pentaethylene hexamine, and the like.

In interfacial polycondensation, the amount of first shell wall component and second shell wall component used in the process determines the percent shell wall content produced. Generally, there is present in the reaction from about 3.5% to about 21.0% first shell wall component, and from about 1.5% to about 9.0% second shell wall component, relative to the weight of the water-immiscible material. A stoichiometric amount pr excess of second shell wall component may be used. The shell wall content of the capsules which results varies from about 5% to about 30%, preferably 8 to 20% and more particularly, 10% by weight, based on the weight of the active ingredient to be encapsulated.

Representative of isocyanate monomers suitable for in situ microencapsulation are the following: 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'-methylenbis(2-methylphenyl isocyanate), 3 ,3'-dimethoxy-4,4'-biphenylene diisocyanate, 2,2',5,5'-tetramethyl-4,4'-biphenylene diisocyanate, 80% 2,4- and 20% 2,6- isomer of tolylene diisocyanate, polymethylene polyphenylisocyanate (PAPI®), and mixtures thereof. The amount of organic polyisocyanate used in the in situ microencapsulation process determines the shellwall content of the capsules formed therein. The preferred range is from about 5.0% to about 30.0% relative to the weight of active ingredient to be encapsulated. Most preferred is about 10% relative to the weight of active ingredient to be encapsulated. What is meant by an imulsifier is a copolymer or teipolymer of vinylpyrrolidone wherein the vinylpyrrolidone is present in sufficient amount to provide the copolymer of teipolymer with the properties described below. The emulsifiers of the invention are copolymers and teipolymers composed of any non-aromatic water soluble monomers polymerized with vinylpyrrolidone to produce water soluble copolymers and teφolymers which are capable of forming a stable oil-in-water emulsion under the reaction conditions described herein. Any polymer combination which includes sufficient vinylpyrrolidone to render the whole polymer combination to be water soluble is expected to be useful as an emulsifier of the present invention. This includes copolymers, teφolymers of vinylpyrrolidone wherein the copolymer and teipolymer includes any number of different polymers in combination with vinylpyrrolidone that results in the copolymers and teφolymers being water soluble and capable of producing a stable oil-in-water emulsion under the present conditions. Preferred copolymers include VP copolymerized with 1) vinyl acetate, 2) dimethylaminomethylmethacrylate, and 3) quartemerized dimethylaminoethylmethacrylate. The weight percent VP in the copolymers is 20-95%, preferably 50-85%. Preferred teφolymers include VP copolymerized with caprolactam and dimethylaminomethacrylate. The weight percent VP in the teφolymers is 10-80%, preferably 15-50%. Specific commercially available VP copolymers are Agrimer® DA-10, Agrimer® DA-1, Agrimer® DAQ-300, Agrimer® DAQ-2000 and Agrimer® VA-6. Agrimer® DAVC is representative of teφolymers which are also effective for use in practice of the invention. These polymers are manufactured by International Specialty Products, 1361 Alps Road, Wayne, New Jersey, 07470. Preparation of these polymers is described in U.S. 4,520,179; U.S. 4,520,180; U.S. 4,554,311; U.S. 4,554,312; U.S. 3,691,125; and U.S. 4,521,404. The range of emulsifier concentration found most acceptable in the system will vary from about 0.5% to about 15% and preferably 2% to 6%, based upon weight of the active ingredient to be encapsulated.

The microcapsules of the present invention require no additional treatment such as separation from the aqueous liquid, and may be directly utilized. The aqueous suspensions are suitable for many applications depending on the water-immiscible material which is encapsulated. For example, an aqueous suspension of miscrocapsules containing a herbicide may be combined with liquid fertilizers, insecticides, or the like to form aqueous solutions which may be conveniently applied for agricultural uses.

Often it is most convenient to bottle or can the aqueous suspension containing the encapsulated water-immiscible material, in wliich case it may be desirable to add formulation ingredients to the aqueous solution of microcapsules. Formulation adjuvants such as density balancing agents, thickeners, biocides, surfactants, dispersants, salts, anti¬ freeze agents, and the like can be added to improve suspension stability and the ease of application. If a formulation adjuvant is added to the aqueous suspension of microcapsules such ingredients are preferably added at a concentration of from about 0.01% to about 30% by weight of the suspension.

If it is desired to adjust the pH of the finished microcapsule formulation as, for example, when the aqueous solution of finished microcapsule is combined with other pesticides, conventional reagents for adjustment of acidity or alkalinity, may be used. For example, suitable substances are hydrochloric acid, sodium hydroxide, sodium carbonate, and sodium bicarbonate.

Thus the pesticidal composition may be in liquid form comprising the suspension which results after the microencapsulation reaction. Alternatively, the pesticidal composition may be in solid form by drying the suspension which results after microencapsulation and then granulating by using well-known techniques to afford a dry microencapsulated granule composition.

In practicing the process of the present invention, the temperature should be maintained above the melting point of the pesticide if used neat, or the unreactive solvent if a pesticide solution is used. The temperature should also be kept below the point at which the water-immiscible monomer hydrolyzes or otherwise decomposes. For example, where it is desired to encapsulate a solid herbicide without solvent, it will be necessary to heat the herbicide to its molten state. Alachlor herbicide, for example, melts at 39.5-41.5°C and the temperature of the process should accordingly be maintained above about 41.5°C.

The agitation employed to establish the dispersion of water-immiscible droplets in the aqueous phase may be supplied by any means capable of providing suitably high shear. That is, any variable shear mixing apparatus, e.g., a blender, a homogenizer, etc. can be employed to provide the desired agitation.

The particular size of the microcapsules will range from about 1 micron up to about 100 microns in diameter. A preferred range is about 1 to about 50 microns. From about 1 to about 10 microns is an optimum diameter range.

The present invention is further explained by the following Examples which are illustrative and not limiting in nature. Unless otherwise indicated, the interfacial polycondensation Examples which follow were performed as follows: the water- immiscible material, containing the first shellwall component(s) dissolved therein, was emulsified into water containing the emulsifier; the emulsion was formed with the aid of high shear. The second shell wall component(s), usually dissolved in an additional amount of aqueous phase liquid, was thereafter added to the emulsion and after a short period of time, the shear rate was reduced. Shear was continued for varying periods of time and thereafter salt or a suspending aid was added if necessary to stabilize the suspension. The formulation was then bottled. In the process of in situ microencapsulation, the isocyanate monomers were dissolved in the water-immiscible phase along with a catalyst. An emulsion was made and slower shear was continued and the temperature raised to speed the shell wall forming reaction. The shellwall component is formed by the reaction of the amine hydrolysis product and residual isocyanate.

EXAMPLE 1 This Example shows the use of Agrimer® DAQ-300 (vinyl- pyrrolidone/quaternarized dimethylaminoethyl methacrylate co-polymer 300,000 molecular weight) to emulsify an acetanilide herbicide at elevated temperature for microencapsulation.

200 Grams of technical alachlor (93.8%) containing 13.9 grams of PAPI® 2027 (a polymethylene polyphenylisocyanates from the PAPI series by Dow Chemical Company) was emulsified into 152.38 grams of water containing 10 grams of Agrimer® DAQ-300. All materials were maintained at 50°C. The emulsion was formed with a Waring blender operating at high shear. To the emulsion, after 1 min., was added

13.9 grams of 43.37% hexamethylenediamine and shear was reduced to a stirring shear. After 5 min. of stirring, 32.8 grams of sodium chloride and 22 grams of 1% Kelzan®, a xanthan gum thickener, were added. Stirring continued for 15 min. and the formulation was bottled. Discreet spherical microcapsules 1 to 40 microns in diameter were observed microscopically. The formulation was stable through accelerated aging at 54°C and after several weekly temperature cycles between -4° and +54°C.

EXAMPLE 2 This Example shows microencapsulation of alachlor at elevated temperature using Agrimer® DA-10 (vinylpyrrolidone/dimethylaminoethyl methacrylate co-polymer) as emulsifier.

200 Grams of technical alachlor (93.8%) containing 13.9 grams of PAPI® 2027 was emulsified into 152.38 grams of water containing 6 grams of Agrimer® DA- 10. All materials were maintained at 50°C. The emulsion was formed with a Waring blender operating at high shear. To the emulsion, after 1 min., was added 13.9 grams of 43.37% hexamethylenediamine and shear was reduced to a stirring shear. After 5 min. of stirring, 32.8 grams of sodium chloride and 22 grams of 1% Kelzan®, a xanthan gum thickener, were added. Stirring continued for 15 min. and the formulation was bottled. Discreet spherical microcapsules 1 to 50 microns in diameter were observed microscopically. The formulation was stable through accelerated aging at 54°C and after several weekly temperature cycles between -4° and +54C. EXAMPLE 3 This Example shows microencapsulation of alachlor at elevated temperature using Agrimer® DAQ-2000 (vinylpyrrolidone/quaternarized dimethylaminoethyl methacrylate co-polymer 2,000,000 molecular weight) as emulsifier. 200 Grams of technical alachlor (93.8%) containing 13.9 grams of PAPI® 2027 was emulsified into 150.38 grams of water containing 4 grams of Agrimer® DAQ-2000. All materials were maintained at 50°C. The emulsion was formed with a Waring blender operating at high shear. To the emulsion, after 1 min., was added 13.9 grams of 43.37% hexamethylenediamine and shear was reduced to a stirring shear. After 5 min. of stirring, 32.8 grams of sodium chloride and 22 grams of 1% Kelzan®, a xanthan gum thickener, were added. Stirring continued for 15 min. and the formulation was bottled. Discreet spherical microcapsules 1 to 25 microns in diameter were observed microscopically. The formulation was stable through accelerated aging at 54°C and after several weekly temperature cycles between -4° and +54°C. EXAMPLE 4

This Example shows microencapsulation of alachlor at elevated temperature using Agrimer® DAVC (vinylpyrrolidone/vinylcaprolactam/dimethylaminoethyl methacrylate ter-polymer) as emulsifier.

200 Grams of technical alachlor (93.8%) containing 13.9 grams of PAPI® 2027 was emulsified into 160.38 grams of water containing 8 g of Agrimer® DAVC. All materials were maintained at 50°C. The emulsion was formed with a Waring blender operating at high shear. To the emulsion, after 1 min., was added 13.9 grams of 43.37% hexamethylenediamine and shear was reduced to a stirring shear. After 5 min. of stirring, 22 grams of 1% Kelzan®, a xanthan gum thickener, was added. Stirring continued for 15 min. and the formulation was bottled. Discreet spherical microcapsules 1 to

15 microns in diameter were observed microscopically. The formulation was stable through accelerated aging at 54°C and after several weekly temperature cycles between -4° and +54°C.

COMPARATIVE EXAMPLE A This Comparative Example shows microencapsulation of alachlor at elevated temperature using Reax® 88B (a lignosulfonate emulsifier).

200 Grams of technical alachlor (93.8%) containing 13.9 grams of PAPI® 2027 was emulsified into 150.38 grams of water containing 4 grams of Reax® 88B. All materials were maintained at 50°C. The emulsion was formed with a Waring blender operating at high shear. To the emulsion, after 1 min., was added 13.9 grams of 43.37% hexamethylenediamine and shear was reduced to a stirring shear. After 5 min. of stirring, 32.8 grams of sodium chloride and 22 grams of 1% Kelzan®, a xanthan gum thickener, were added. Stirring continued for 15 min. and the formulation was bottled. Discreet spherical microcapsules 1 to 20 microns in diameter were observed microscopically. The formulation was stable through accelerated aging at 54°C and after several weekly temperature cycles between -4° and +54°C.

Resuspendability of settled solids from diluted formulations prepared in Examples 1-4 and Comparative Example A was tested as follows: Into 95 grams of tap water in Nessler® tubes was added 5 grams of the formulation. The Nessler® tubes were inverted several times and shaken to thoroughly suspend the formulations, and then left undisturbed for 3 days at room temperature. The Nessler® tubes were then slowly inverted and the number of inversions required to resuspend the settled microcapsules was recorded. Data are shown in Table 1.

TABLE 1 Number of Inversions Required to Resuspend Settled Microcapsules after 3 Days

Required vigorous shaking to resuspend the settled microcapsules. We consider 30 inversions to be the commercially acceptable cut off.

COMPARATIVE EXAMPLE B This comparative example shows attempted microencapsulation of alachlor at elevated temperature using Agrimer® ST (vinylpyrrolidone/styrene copolymer).

200 Grams of technical alachlor (93.8%) containing 13.9 g of PAPI 2027 was emulsified into 152.38 g of water containing 10 g of Agrimer® ST. All materials were maintained at 50°C. The emulsion was formed with a Waring blender operating hexamethylenediamine. Upon addition of diamine, instant solidification occurred. No useful microcapsules were obtained.

EXAMPLE 5 This Example shows microencapsulation of a liquid cineole herbicide, cinmethylin, with Agrimer® DA- 10.

80.00 Grams of cinmethylin containing 5.56 grams PAPI® 2027 was emulsified into 62.61 grams water containing 1.6 grams Agrimer® DA-10. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added 5.56 grams of 43.37% hexamethylenediamine. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-50 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

COMPARATIVE EXAMPLE C This example shows the attempted microencapsulation of a liquid cineole herbicide, cinmethylin, with Agrimer® ST (vinylpyrrolidone/styrene copolymer).

Example 5 was repeated exactly as described except that 1.6 g of Agrimer® ST was used in place of 1.6 g of Agrimer® DA-10. The emulsion formed well, however, when diamine was added to the emulsion it became a pastey material. Microscopically it appeared that microcapsules may have formed, however, they were highly aggregated and the entire composition was not a useful suspension of discreet microcapsules.

EXAMPLE 6 This Example shows microencapsulation of a liquid cineole herbicide, cinmethylin, with Agrimer® VA-6 (vinlypyrrolidone/vinyl acetate random copolymer having 60% pyrrolidone and 40% acetate by weight). 80.00 Grams of cinmethylin containing 5.56 grams PAPI® 2027 was emulsified into 62.61 grams water containing 1.6 grams Agrimer® VA-6. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added 5.56 grams of 43.37% hexamethylenediamine. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-15 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

EXAMPLE 7 This Example shows microencapsulation of a liquid cineole herbicide, cinmethylin, with Agrimer® DAQ-2000. 80.00 Grams of cinmethylin containing 5.56 grams PAPI® 2027 was emulsified into 62.61 grams water containing 1.6 grams Agrimer® DAQ-2000. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added 5.56 grams of 43.37% hexamethylenediamine. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-50 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

EXAMPLE 8 This Example shows microencapsulation of a liquid cineole herbicide, cinmethylin, with Agrimer® DAVC. 80.00 Grams of cinmethylin containing 5.56 grams PAPI® 2027 was emulsified into 60.21 grams water containing 4 grams Agrimer® DAVC. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added 5.56 grams of 43.37% hexamethylenediamine. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-10 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

The following Examples X and Y illustrate advantages of the invention in various solvents even though they are carried out in the absence of any pesticidal ingredient.

EXAMPLE X This Example shows microencapsulation of a high density organic solvent, chloroform, with Agrimer® DA- 10 as emulsifier.

90.00 Grams of chloroform containing 5.56 grams PAPI® 2027 was emulsified into 60.21 grams water containing 4 grams Agrimer® DA-10. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added 5.56 grams of 43.37% hexamethylenediamine. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-5 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended widi time.

EXAMPLE Y This Example shows microencapsulation of a low density organic solvent, toluene, with Agrimer® DA-10 as emulsifier.

80.00 Grams of toluene containing 5.56 grams PAPI® 2027 was emulsified into 60.21 grams water containing 4 grams Agrimer® DA-10. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added 5.56 grams of 43.37% hexamethylenediamine. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-20 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

EXAMPLE 9 This Example shows microencapsulation of a fungicide solution in organic solvent, with Agrimer® DA-10 as emulsifier.

80.00 Grams of flusilazole in xylene (50%) containing 5.56 grams PAPI® 2027 was emulsified into 60.21 grams water containing 4 grams Agrimer® DA-10. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added 5.56 grams of 43.37% hexamethylenediamine. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-10 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

EXAMPLE 10 This Example shows microencapsulation of a liquid cineole herbicide, cinmethylin, with Agrimer® DAQ-2000, as emulsifier, producing a polyester shellwall. 80.00 Grams of cinmethylin containing 17.77 grams sebacoyl chloride was emulsified into 60.21 grams water containing 4 grams Agrimer® DAQ-2000. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added a solution containing 6.33 grams 1,6-hexanediol, 1.71 grams 1,3,5-benzenetriol, and 12.00 grams 50% aqueous NaOH. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules and some irregular shaped microcapsules 1-50 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

EXAMPLE 11 This Example shows microencapsulation of a liquid cineole herbicide, cinmediylin, by in situ microencapsulation, with Agrimer® DA-10 as emulsifier.

200 Grams of cinmethylin containing 15 grams PAPI® 2027, 15 grams of toluenediisocyanate, and 0.1 grams of dibutyltin dilaurate catalyst, was emulsified into 154 grams water containing 6 grams Agrimer™ DA-10. An emulsion was formed at high shear with a Waring blender for 5 min. The temperature was raised to 50°C, and slow shear continued for 1 h. Discreet, individual microcapsules 1-7 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

EXAMPLE 12 This Example shows microencapsulation of a liquid cineole herbicide, cinmethylin, with Agrimer® DA- 10 as emulsifier, producing a mixed polyurea polyamide shell wall.

80.00 Grams of cinmethylin containing 2.8 grams PAPI® 2027, 1.4 grams sebacoyl chloride, and 1.2 grams trimesoyl chloride, was emulsified into 60.21 grams water containing 4 grams Agrimer® DA-10. An emulsion was formed at high shear with a Waring blender. To the emulsion, after 1 min. of shear was added a solution containing 7 grams of 43.37% hexamethylenediamine and 2.5 grams 50% aqueous NaOH. After an additional 15 min. of slow shear stirring the formulation was bottled. Discreet, individual microcapsules 1-10 microns in diameter were observed microscopically. The formulation remained fluid and readily resuspended with time.

Claims

What is claimed is:

1. A process for preparing a highly concentrated composition of particles of a microencapsulated pesticide in water wherein the pesticide is encapsulated in a plastic shell with substantially no agglomeration of the particles, said process comprising (a) mixing a water immiscible monomer A and an active pesticidal ingredient in the form of a liquid, melted solid or solution of said active ingredient in an unreactive water-immiscible solvent, said monomer selected from the group consisting of diacid and polyacid chlorides, dichloroformates, polychloroformates, disulfonyl and polysulfonyl chlorides, diisocyanates, polyisocyanate and mixtures thereof, to form a solution of the monomer in the active ingredient to be encapsulated;

(b) dispersing in water containing an emulsifier the solution of the monomer and active ingredient, said emulsifier being a water-soluble co- or ter-polymer of vinylpyrrolidone, to form a water-in-oil emulsion with said droplets in the size range of 1 to 100 microns; (c) adding to the emulsion of (b) a water-soluble monomer B which will react with monomer A by interfacial polycondensation to form a shell around the pesticidal ingredient, said water-soluble monomer B selected from the group consisting of diamines or polyamines, diols or polyols; or alternatively when monomer A is a diisocyanate, a polyisocyanate or mixtures thereof, optionally including a catalyst in the solution from (a) and heating the emulsion of (b) to hydrolyze monomer A to amine groups whereby the amine groups generated by hydrolysis react with residual isocyanate monomers to generate a shell wall of polyurea;

(d) optionally, adding formulation adjuvant(s); and

(e) optionally, drying followed by granulation of the solid residue to form a flowable solid composition.

2. The process of Claim 1 wherein interfacial polycondensation is to be achieved using monomer B.

3. The process of Claim 1 wherein monomer A is a diisocyanate, a polyisocyanate or mixtures thereof and monomer A is hydrolyzed in the presence of a catalyst and heated to form an amine that will react with residual isocyanate monomers.

4. The process of Claim 2 wherein and die concentration of emulsifier is from about 0.5% to about 15.0% by weight, the concentration of monomer A is from about 3.5% to about 21.0% by weight, and the concentration of monomer B is from about 1.5% to about 9.0% by weight, such that all weights are relative to the weight of active ingredient to be encapsulated.

5. A composition comprising highly concentrated microcapsuled pesticides suspended in an aqueous liquid, said microcapsuled pesticides comprising a liquid, solid or solution of an active pesticide in an unreactive water-immiscible solvent within an encapsulating wall of polymeric material wherein:

(a) said active pesticide being present at a concentration ranging from about 480 to about 700 grams per liter of composition; (b) said encapsulating wall of polymeric material is the reaction product of a first shell wall component which is a difunctional or polyfunctional reactant soluble in the active pesticide, and a second shell wall component which is water-soluble and which is a difunctional or polyfunctional reactant and wherein the concentrations of said first and second shell wall components are from about 3.5% to about 21.0% and from about 1.5% to about 9.0%, respectively, by weight relative to die weight of the active ingredient to be encapsulated; and

(c) said aqueous liquid is water containing

(i) from about 0.5% to about 15% by weight of an emulsifier relative to the weight of said active ingredient to be encapsulated, said emulsifier being a water-soluble co- or ter-polymer of - vinylpyrrolidone, and (ii) optionally, from about 0.01% to about 30% of a formulation adjuvant based on d e total weight of the composition.

6. The composition of Claim 5 wherein the concentration of the active pesticide s 480 grams to 600 grams per liter of aqueous solution.