CA2261034A1 - Process for preparing storage-stable pesticide dispersion - Google Patents
Process for preparing storage-stable pesticide dispersion Download PDFInfo
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- CA2261034A1 CA2261034A1 CA002261034A CA2261034A CA2261034A1 CA 2261034 A1 CA2261034 A1 CA 2261034A1 CA 002261034 A CA002261034 A CA 002261034A CA 2261034 A CA2261034 A CA 2261034A CA 2261034 A1 CA2261034 A1 CA 2261034A1
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- Prior art keywords
- poly
- surfactant
- water
- dispersion
- aqueous dispersion
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/02—Making microcapsules or microballoons
- B01J13/06—Making microcapsules or microballoons by phase separation
- B01J13/14—Polymerisation; cross-linking
- B01J13/16—Interfacial polymerisation
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- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
- A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
- A01N25/26—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests in coated particulate form
- A01N25/28—Microcapsules or nanocapsules
-
- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
- A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
- A01N25/30—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests characterised by the surfactants
Abstract
Aqueous dispersions of microcapsules containing a high loading of pesticide in the form of supercooled melts or supersaturated solutions are stabilised to crystallisation of the pesticide by ensuring that the volume median particle size of the microcapsules is kept below 6.mu.m, and by employing surfactants which do not form micelles under storage conditions, thereby inhibiting transportation of the pesticide through the aqueous phase.
Description
~PROCESS FOR PREPARING STORAGE-STABLE PESTICIDE DISPERSION
~This invention relates to a process for preparing an aqueous dispersion of polymeric microcapsules containing S a supersaturated solution or supercooled melt of water-insoluble materials. In particular, it is concerned with providing aqueous dispersions of pesticidal material which do not crystallise, so that a product with a high content of active material can be provided which is storage-stable. Storage-stable transportable aqueous dispersions of pesticides are provided which can be applied to crops and the like by conventional spray technlques .
~5It is well known to encapsulate highly water-insoluble pesticidal material in polymeric microcapsules, in order that the pesticidal material can be applied to cr~ps and the like. Such microcapsule formulations are commoniy provided in the form of spray-dried powders, whicn are rewetted prior to application. For example, US-A-~160530 (Griffin) discloses a process for encapsulating pesticides by melting the active material and combining the melted material with a film-forming polymer, such as a polyvinyl alcohol (PVA). The mat~rials are then emulsified together and spray-dried.
A similar method is disclosed in US-A-4244836 (Hoechst).
For some applications, however, liquid concentrates, -particularly aqueous concentrates, have substantial advantages over dry formulations. Aqueous concentrates are generally easier to formulate for field application, and generate reduced possibility of lnhalation by a user.
SU~STI~UTE S~IEET (RU~E 26) It lS known to prepare encapsulated pesticides as wet formulations, i.e. as an aqueous dispersion of microcapsules. However, such aqueous concentrates tend to have a lower loading of active ingredient, and therefore tend to be more costly to store and transport than corresponding dry formulations. For instance, US-A-4938797 includes an example of a wet formulation of microcapsules in which the suspension has an active ingredient content of 46% by weight.
It is known to prepare pesticide-containing dry microcapsules by carrying out the encapsulation process at an elevated temperature, either employing very low amoun~s of solvent (so that when the dispersion cools the pest~cide is encapsulated in the form of a supersaturated solution) or by encapsulating a melt of the pesticide resulting in microcapsules containing a supercooled melt.
~e have ~ound however that concentrated aqueous formulations of microcapsules containing supercooled melts or supersaturated solutions are not storage-stable, since, on storage at ambient temperatures, crystallisation of the pesticide occurs. This renders the formulation unusable.
Surprisingly, it has been discovered that storage-stable aqueous dispersions of microcapsules containing a high loading of active product in the form of supercooled melts or supersaturated solutions can be stabilised against crystallisation by providing that the microcapsules have a volume median particle size of not more than 6~m, preferably not more than 5~m, more preferably not more than 2~m. It has further been discovered that crystallisation of the active product from such dispersions can be reduced by avoiding the use SUBSTITUT~ SHEET (RULE ~6~
CA 0226l034 1999-0l-l8 - of surfactants which form micelles under the conditions of storage (and thereby facilitate transportation of the - water-insoluble material through the aqueous phase, resulting in crystallisation).
WO 95/07614 relates to the use of polymeric stab lisers to alter the chemical potential of emulsion particles in an oil-in-water emulsion, and thereby inhibit Ostwald ripening. The use of such stabilisers in suspension-emulsions is also disclosed, as are a number of aqueous dispersing agents for such dispersions, inc;uding a polyvinyl alcohol/polyvinyl acetate copolymer. This reference also discloses certain mic-ocapsule suspensions. There is no disclosure in WO
95/~7614 however of the desirability of selecting a non-micellising surfactant, and of the need to avoid sur-actants which do form micelles, in order to stabilise pa~ iculate dispersions. In fact, the surfactant used to sta~ilise the dispersions of microcapsules disclosed in ~O ~5/07614 is ATLOX 4991TM, an ethoxylated alcohol which is a micellising surfactant.
PCT/US95/15534 discloses the preparation of dry mic-ocapsules by spray-drying aqueous solutions of mic-ocapsules containing PVA surfactants. There ls no suggestion in PCT/US95/15534 however that the use of such surfactants (or the use of any non-micellising surfactant) is able to improve the long-term stability of aqueous formulations.
Accordingly, in a first aspect of the invention, there is provided a process for preparing a storage-stable aqueous dispersion of a water-insoLuble material, which process comprises emulsifying in water a non-SUBSTITUT~ SHEET (RlJLE 26) .
aqueous phase comprising a solution or a melt of the water-insoluble material, so as to form emulsion particles having a volume median particle size of not more than 6~m, and carrying out a polymerisation process to form from the emulsion particles an aqueous dispersion of microcapsules, the said microcapsules having the said water-insoluble material contained therein in the form of a supersaturated solution or a supercooled melt, and stabilising the dispersion with a non-micellising surfactant, wherein the stabilised dispersion is substantially free of micellising surfactant.
The amount and/or nature of the non-micellising surfactant may be such that the solubility of the water-insoluble material in the aqueous phase is not more thanlOOppm preferably not more than 50ppm, more preferably not more than 5ppm.
The term "non-micellising" as used herein is intended to mean a surfactant which does not form micelles (which facilitate transport of the water-insoluble material through the aqueous phase) under the conditions used to store the stabilised dispersion.
The process of the invention generally includes the step of storing the stabilised dispersion, for example after pac~aging in a closed container.
The condltions of storage may be any conditions appropriate to the particular dispersion and water-insoluble material, but will generally be ambient condi~ions.
SUBSTITUT~ SHEET (RULE 2~) The tendency of a surfactant to form mlcelles increases with the concentration of the surfactant. The point at which micelles are formed is known as the critical micelle concentration (CMC). In order to find the CMC for a particular surfactant, the surface tension of the surfactant is plotted against the log of its concentration. Those surfactants which readily form mlcelles, such as monomeric anionic and nonionic surfactants, typically show a quite rapid reduction in surface tension with concentration, until a specific cor.centration for that surfactant (the CMC) at which the reduction in surface tension ceases.
Such a plot is shown in Figure ~, which is a plot of surface tension against log concentration for an ethoxylated alcohol surfactant (shown as "-") and for a polyv r.yl alcohol (shown as "-"). It can be seen that the ethoxylated aLcohol forms micelles at and above a ConCentratlon of lO-2s ~w/w. By contrast, the curve for t~e DVA shows a gradually reducing surface ~ension with concer,.ration with no clear change in behaviour, indicative that no micelles are formed in this case. A
simple plot of surface tension against concentration can therefore be carried out to determine whether the surfactant forms micelles at the concentrations and under the conditions employed in the formulation.
Most surfactants are such that, under essentially all ~ractical conditions of use, they are "micellising"
and therefore unsuitable. Examples of such surfactants include nonionic surfactants such as fatty alcohol ethoxylates (alkoxylates), such as are employed in WO
9~/07614, fatty acid esters (and alkoxylates of fatty acid esters), alkoxylated amines, ethylene oxide-SUBSTITUT~ SHEET tRULE 26) propylene oxide copolymers, fatty acid alkoxylates (PAG
esters, specifically PEG esters), tall oil and rosin ester alkoxylates, alkyl phenol alkoxylates, substituted phenol alkoxylates; anionic surfactants such as dodecyl benzene sulphonic acid and its salts, alkyl sulphates, nonionic alkoyxlates phosphated or sulphated to produce the corresponding phosphate ester or ether sulphate ' respectively and cationic surfactants such as cetyl trimethyl ammonium chloride. Other micellising surfactants can be found in reference works such as "McCutcheons Emulsifiers & Detergents".
Clearly, there is a balance between the emulsifying e fect and the tendency to form micelles (both of which ncrease with surfactant concentration). It will be appreciated that, between preferred surfactants and unsuitable surfactants, there is a group of surfactants ~hich have some stabilising effect but which are not preferred.
A surfactant may be used which forms micelles under ~he process conditions, provided that it does not form micelles under the conditions of storage, since it is on storage that crystal isation generally takes place.
As indicated above, the "non-micellising surfactant"
is one which is able to stabilise the dispersion such that the dispersed microcapsules remain in suspension on extended storage.
Without wishing to be constrained by theory, it is thought that the surfactants in question inhibit transportation of the water-insoluble material through the aqueous phase, thereby reducing the likelihood of SUBSTITUT~ S~lEET (RULE 26) nucleatlon of the said material and of subsequent crystallisation. By contrast, those surfactants which have a strong ability to form micelles are thought to promote transportation of the water-insoluble material S through the aqueous phase, resulting in crystallisation.
In principle any surfactant can be used which has a sufficient emulsifying effect when employed at a concentration below its critical micelle concentration.
In practice, suitable surfactants tend to be polymeric surfactants of relatively high molecular weight, for example with 2 weight average molecular weight of at leas~ 10,000. Lignosulphates with a weight average molecular weight of at least 2,000 are also suitable.
A preferred stabilising surfactant a poly(vinyl pyrrolidone), a co-poly(vinyl alcohol/acetate~ PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyi pyrrol done/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(ca~boxyalkyl cellulose). A particularly preferred surfactant is a polyvinyl alcohol (~VA).
The aqueous dispersions of the present invention may be packaged in a closed container for shipping and transport purposes.
In a preferred embodiment, the stabilising surfactant is added prior to the polymerising step and, more preferably, prior to the emulsifying step.
SUBSTITUT~ SHEET (RULE ~6~
_ . . .. .
w098/03065 PCT/GB97101951 2article size (vmd) may be measured, for example, using a laser diffraction instrument, for example a Malvern Mastersizer~.
As used herein, the term "water-insoluble material"
means a material which has a solubility in water of not more than lOOppm, more preferably not more than 50ppm, more preferably still not more than 5ppm.
The polymerisable material is preferably polymerised in ar. interfacial reaction, and most preferably in an .nterfacial condensation reaction. In a preferred embodiment, the polymerisable material is a polyisocyanate which is polymerised by means of a condensation reaction with a polyamine.
Alternatively, the polymerisable material may be a crosslinkable material which is used to coat the emulsion par~ -ies by 2 coacervation method, and thereafter crosslinked to form the microcapsules.
Both interfacial and coacervation methods involve the preparation of an oil-in-water emulsion, followed by either a condensation reaction at the oil/water interface to produce a polymeric film, or the production of a coacervate which can then deposit on the oil surface, followed by film forming and hardening, which can take place by a variety of processes. The condensation reaction can for example be a multi-component reaction between, for example:
acid chlorides and polyamines isocyanates and polyamines, SUBSTITUT~ SHEET (RULE 26 rsocyanates and polyols, or mixtures or the above.
Coacervates can be formed by any of the processes t3ught in the art, for example using gelatine/gum arabic The microcapsules in accordance with the invention may be prepared by high shear mixing of a solution or a melt containing the water-insoluble material (e.g.
pesticide), preferably a PVA (as an aqueous solution) to enhance microcapsule formation, and one of the materials for forming the microcapsules (e.g. a polymerisable material for instance an isocyanate or a crosslinkable material). The PVA acts as an emulsifier, and in some systems, no further emulsifier may be required. It is desirable however to add additional emulsifiers, which may be of generally known type in order to produce the desired emulsion of small particle size (provided that tne emulsifiers are non-micellising as defined herein).
When the size of the emulsion is as desired, then the othe~ polymeric cross-linker is added (e.g. polyamine), to complete the interfacial polycondensation.
As indicated above, a preferred reactant for the polycondensation is a polyamine, which is usually a water soluble, reactive polyamine, such as diethylene triamine or tetraethylene pentamine. These amines start to react with the isocyanate at the interface as soon as they are added to the emulsion. More complete control can sometimes be achieved by using either a water-soluble amine salt, or an oil-soluble amine salt, dissolved respectively in the aqueous phase or the oil phase at an early stage in the process (for example, before emulsification). By virtue of the fact that they are SUBSTITUT~ SHEET (RULE 26~
WO 38~!~3~5 PCT/GB97/01951 salts, they do not immediately react with the isocyanate, but do so promptly when the pH is adjusted to liberate the free amine, whereupon cross-linking occurs.
The high shear mixing can be performed on a batch of the ingredients, or may be conducted continuously (in-line). In the former case, the time of addition or release of the reactive amine is governed by the processing time re~uired to form the emulsion with the correct particle size distribution (which clearly is ba~ch size dependent), whilst in the latter case, the interfacial reaction can be better controlled, since the amine can be added/released at any desired time simply by choice of injection point in the process stream, thus giving essentially complete control over the urea/urethane ratio.
In a preferred embodiment, an additional non-micellising surfactant is provided in the aqueous dispersion. The dispersion may also preferably comprise an antifreeze agent, for example an ethylene glycol or a propylene glycol.
The water-insoluble material is preferably a pesticidal material. The term "pesticidal material"
includes but is not limited to insecticidaL, miticidal, herbicidal and fungicidal materials.
Suitable insecticidal materials are:
acrinathrin allethrin alpha-cypermethrin amitraz azinphos-ethyl azinphos-methyl benfuracarb benzoximate beta-cypermethrin betacyfluthrin bifenthrin binapacryl SuBsrl~uT~SHEET(RUL~ ~
W098/03065 PCT/Gss7/o1ssl bicallethrin bioallethrin S bioresmethrin bioresmethrin bromophos bromopropylate - buprofezin butacarboxim butoxycarboxin cambda-cyhalothrin chlordimeform chlorfenvinphos chl~rflurazuron chlormephos chlorobenzilate chlorophoxim chloropropylate chlorpyrifos chlorpyrifos- cyanophos cycloprothrin methyl cyfluthrin cyhalothrin cypermethrin cyphenothrin deltamethrin demeton-S-methyl dichlorvos dicofol dinobuton dioxabenzafos dioxacarb disulfoton ed~fenphos empenthrin endosulfan EPNethiofencarb esfenvalerate ethoprophos etofenprox etrimphos fenamiphos fenazaquin fenitrothion fenobucarb ferpropathrin fenthiocarb fenthion fer.valerate flucythrinate flufenoxuron formothion gamma-HCH hexaflumuron hydroprene isofenphos isoprocarb isoxathion malathion mephospholan methidathion methoprene methoxychlor mevinphos N-2,3-dihydro-3- parathion methyl methyl-1,3-thiazol-2-ylidene-2,4-xylidene permethrin phenothrin phenthoate phosalone phosfolan phosmet pirimiphos-ethyl pirimiphos-methyl profenofos promecarb propaphos propargite propetamphos pyrachlofos quinalphos resmethrin tau-fluvalinate tefluthrin tefluthrin temephos terbufos terbufos tetrachlorinphos tetrachlorinphos SUBS~I~Un SHEET(RUL~ ~) W098/03065 PCT/Gss7/01951 tetradifon tetramethrin tralomethrin tralomethrin tralomethrin triazophos triazophos xylylcarb Suitable fungicidal materials are:
azaconazole benalaxyl biteranol bupirimate carboxin cyproconazole difenoconazole dimethomorph diniconazole ditalimfos dodemorph dodine epoxyconazole ethoxyquin etridiazole fenarimol fenpropidin fenpropimorph fluchloralin flusilazole imibenconazole myclobutanil myclobutanil nuarimol oxycarboxin penconazole prochloraz propiconazole pyrifenox tebuconazole tetraconazole tolclofos-methyl triadimefon triadimenol tridemorph triflumizole Sui~abie herbicidal materials are:
2,4-D esters 2,4-DB esters acetochlor aclonifen alachlor anilophos benfluralin benfuresate bensulide benzoylprop-ethyl bifenox bromoxynil bromoxynil esters butachlor butamifos butralin butylate carbetamide chlornitrofen chlorpropham cinmethylin clethodim clomazone clopyralid esters CMPP esters cycloate cycloxydim desmedipham dichlorprop esters diclofop-methyldiethatyl dimethachlor dinitramine ethalfluralin SUBSTITUl~ SHEET (RULE 26) CA 0226l034 1999-0l-l8 ethofumesate fenobucarb fenoxaprop ethyl fluazifop fluazifop-P fluchloralin flufenoxim flumetralin flumetralin fluorodifen fluoroglycofen fluoroxypyr esters ethyl flurecol butyl flurochloralin haloxyfop ethoxyethyl haloxyfop-methyl ioxynil esters isopropalin MCPA esters mecoprop-P esters metolachlor monalide napropamide nitrofen oxadiazon oxyfluorfen pendimethalin phenisopham phenmedipham picloram esters pretiiachlor profluralin propachlor propanil propaquizafop pyridate quizalofop-P triclopyr esters tridiphane tril~iuralin Par i_ularly suitable pesticidal materials are chlor?yrifos and trifluralin.
The aqueous dispersion may include an addltional pestlcidal material to that contained in the microcapsules. This additional pesticidal material may be present in solution, in the form of emulsion partlcles, as a dispersion of a solid, or contained wlthin microcapsules.
In a second aspect of the invention, there is provided a storage-stable aqueous dispersion of a water-insoluble material, wherein the water-insoluble material is contalned within microcapsules having a volume median par~icle size of not more than 6~m, preferably not more than ~m, more preferably not more than 2~m, in the form of a supersaturated solution or a supercooled melt, SUBSTITUTE SHEET (RULE 26) .
CA 0226l034 l999-0l-l8 WO 98/03065 PCT/GB97/OlgSl wherein the aqueous dispersion additionally comprises a non-micellising surfactant to stabilise the dispersion, and wherein the stabilised dispersion is substantially free from micellising surfactant.
~ referred non-micellising surfactants are described above.
The water-insoluble material (preferably a pesticidal material as described above) preferably constitutes at least 50% by weight of the aqueous dispersion, and most preferably at least 70% by weight.
When in supersaturated solution (such as in xylene or any other suitable solvent known in the art), the amount of tne said material is preferably at least 70% by weight of solution, most preferably at least 80% by weight of solution.
The aqueous dispersion may include an additional pesticide and/or an additional surfactant as described above.
The aqueous dispersion may be provided in a closed container.
In a third aspect of the invention there is provided the use of a non-micellising surfactant (as described above) to inhibit crystallisation of a water-insoluble material from an aqueous dispersion containing the said material, wherein the water-insoluble material is present in the dispersion in the form of microcapsules containing the said material as a supersaturated solution or a supercooled melt.
SUBSTITUT~ SHEET (RULE 26) ..
In a further aspect of the invention, there is provided a method for the control or eradication of a pest, which method comprises diluting an aqueous dispersion as described above to a pesticidally-effective concentration, and applying the resultant dispersion to the pest or to a locus in which the pest is to be cont-olled particularly, without any intervenin~ spray-drying step.
As indicated above, the method o~ the invention is particularly advantageous for the production of microcapsules having a small particle size, for example having a VMD of 6~m or less, particularly 2~m or less.
The chief advantage of such small capsules is that, as the VMD decreases, it is possible to retain the majority of the supercooled/supersaturated active in the liquid form. It is thus possible to produce in a reliable manner liquid core capsules ~ith the minimal use of solvents, which in turn gives environmental advantages, as well as a higher active loading in the final product.
~urther, such small capsules provide a higher surface area to mass ratio than larger particles, and thus give an enhanced release rate and better knock-down. Yet another benefit of such small capsules is that they can penetrate soil or surface grass thatch better than larger capsules, and so are more efficacious in certain applications where such soil or thatch mobility is needed.
The presence of a liquid core in capsules made with a supercooled molten active has several advantages, of which the most significant from point of view of the present invention is that the core does not crystallise, thus causing rupture of the capsules, which can lead both SUBSTITUT~ SHEET (RULE 26) W098/03065 PcT/Gsg7/01951 to premature release, and to formulation instability on storage. A second advantage is that a liquid core will in general release its active more rapidly than will a solid. This, combined with small particle size, gives a significant increase in active release rate. A third advantage of retaining the active in the liquid state is that there is no possibility of producing a biologically less active polymorph during crystallisation - a problem which is addressed in another way in US-A-5160530 (Griffin).
Any water-insoluble solvent may be employed to dissolve the water-insoluble material in the preparation of tr.e microcapsules if a solvent is deemed desirable.
The use of such solvents reduces the tendency of the said material to crystallise. Examples of typical solvents are a~omatic solvents, particularly alkyl substituted be~.zenes such as xylene or propyl benzene fractions, and mixed naphthalene and alkyl naphthalene fractions;
mineral oils; kerosene, dialkyl amides of fatty acids, particularly the dimethyl amides of fatty acids such as the dimethyl amide of caprylic acid; chlorinated aliphatic and aromatic hydrocarbons such as 1,1,1-trichloroethane and chlorobenzene, esters of glycol derivatives, such as the acetate of the n-butyl, ethyl, or methyl ether of diethyleneglycol, the acetate of the methyl ether of dipropyleneglycol, ketones such as isophorone and trimethylcyclohexanone tdihydroisophorone) and the acetate products such as hexyl, or heptylacetate.
The preferred organic liquids are xylene, propyl benzene fractions, alkyl acetates, and alkyl naphthalene fract~ons.
SUBSTITUT~ SHEET (RU~E 26 WO ~1'0~ 5 PCT/GB97/01951 .~aterlals may be employed which are normally solid at amblent temperatures, but which are capable of forming eutectic mixtures with the water-insoluble material. The use of such materials will generally reduce the tendency of the water-insoluble material to crystallise.
A further advantage of the encapsulation method in accordance with the invention is that it permits the production of aqueous compositions containing two or more active materia~s, where the materials are such that direct formulation of the materials (i.e., without encapsulation of one or both of them) would lead to a product which is chemically or physically unstable. In one aspect, the said actives may be separately encapsulated, but in an alternative and preferred embodiment, one or mor~ of the active materials (or some portion of a single active material) may be encapsulated by the method in accordance with the invention, and the balance not encapsulated, for example, simply dispersed in the aqueous phase. In this way, the un-encapsulated active material is immediately biologically available upon application, whereas the encapsulated material is released more slowly. The amount of each material employed in such different forms will vary dependent upon the particular application but in general terms, each such material may constitute from 0.1 to 99.9~ by weight of the total of the encapsulated material.
Compositions of the invention may also include a stabiliser of the kind disclosed in WO95/07614.
Other conventional additives may also be incorporated into the formulation such as emulsifiers, dispersants, and film-forming polymers (provided that SUBSrl~U~ SHEEt (RULE 263 CA 0226l034 l999-0l-l8 such additives do not form micelles under storage conditions).
A number of preferred embodiments of the invention are described in the following Examples.
The following materials were used in the Examples:
Trade Name Nature of Material Atlox 4913 nonionic surfactant Solvesso 200 aromatic solvent Sopro~an T-36 anionic copolymer Voranate M-220 isocyanate Voranate M-229 isocyanate PAPI 135 isocyanate Hyvis 30 poly~iso butylene) ~yvis 04 poly(iso butylene) Goherseran L-3266 anionically modified PVA
~orwe~ EFW anionic surfactant blend Gohsenol GH20 PVA 88% hydrolysed, high MW
Gohsenol GL05 PVA 88% hydrolysed, intermediate MW
Gohsenol GL03 PVA 88% hydrolysed, low MW
Example l: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (30g) and emulsified into 460g water containing lOg Gohsenol GH20 (an aqueous PVA solution) and lOg Gohsenol GL05 (an aqueous PVA solution) at 50~C.
An emulsion of about 2~m vmd was produced. To this was added a solution of diethylenetriamine (lOg), Atlox 4913 (20g) ln water (70g) to produce an encapsulated product containing a~out 600g/l chlorpyrifos. This product S'UBS~TUTE SHEET (RULE 26~
CA 0226l034 1999-0l-l8 showed no significant crystallisation after 2 weeks storage. A comparative example made by emulsification of the same quantity of chlorpyrifos into the same surfactant solution but without encapsulation, crystallised on standing overnight at laboratory temperature.
Example 2: Molten trifluralin at 50~C (615g) was mixed with PAPI 135 (30g) and emulsified into 365g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 50~C. An emulsion of about 3~m vmd was produced. To this was added a solution of diethylenetriamine (lOg~, Atlox 4913 (20g) in water (70g) to produce an encapsulated product containing about 600g/l trifluralin.
This product showed no significant crystallisation after 2 weeks storage. A comparative example made by emulsificatlon of the same quantity of trifluralin into the same surractant solution crystallised on standing overnight at laboratory temperature.
Example 3: The composition of Example 2 was repeated but emulsified at about 1.5~m and diluted to 500g/l.
This product also showed no significant crystallisation after 2 weeks storage.
~xample 4: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (30g) and emulsified into 440g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 50~C. An emulsion of about 2.5~m vmd was produced. To this was added a solution of diethylenetriamine (lOg), Atlox 4913 (20g) in water ~70g~ to produce an encapsulated product containing about 600g/l chlorpyrifos with a particle size of about 1.29~m. This product SUBSTITU~ SHEET (RUL~ 26) -WO 981'~3C65 PCT/GB97/01951 showed no signlficant crystallisation after 2 weeks s~orage.
Example 5: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (30g) and dioctyl phthalate (50g) and emulsified into 380g water containing lOg Gohsenol GH20 and lOg Gohsenol GL 0 5 at 50~C. An emulsion of about 1.4~m vmd was produced. To this was added a solution of diethylenetriamine (lOg), Atlox 4913 (20g) in water (70g) to produce an encapsulated product containing about ~OOg/1 chlorpyrifos with a particle size of about 1.38~m.
This product showed no significant crystallisation after 2 wee~s storage.
Exam~le 5: Molten chlorpyrifos at 55~C (462g) was mixed with Voronate M-220 (32g) and emulsified i~to 400g water containing 40g Poval 203 (PVA 88~ hydrolysed supplied by Kuraray) at 50~C. An emulsion of about 1.84~m vmd was produced. To this was added a solution of diethylenetriamine (8g) in water (98g) to produce an encapsulated product containing about 46% w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Example 7: Molten chlorpyrifos at 45~C (615g) was mixed with PAPI 135 (lOg) and emulsified into 440g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 45~C. An emulsion of about 1.4~ vmd was produced. To this was added a solution of diethylenetriamine (3.5g), Atlox 4913 (20g) in water (70g) to produce an encapsulated product containing about 600g/1 chlorpyrifos with a particle size of about 1.4~m. This product showed no significant crystallisation after 2 weeks storage.
SUBS~ SltEET (RULE 26) CA 0226l034 l999-0l-l8 ExzmDie 8: Molten chlorpyrifos at 45~C (615g) was mixed with PAPI 135 (20g) and emulsified into 440g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 45~C. An emulsion of about 1.4~m vmd was produced. To this was added a solution of diethylenetriamine (7g~, Atlsx 4913 (ZOg) in water (79g) to produce an encapsulated product containing about 600g/l chlorpyrifos with a particle size of about 1.4~m. This product showed no significant crystallisation after 2 weeks storage.
~xam?'e 9: Molten chlorpyrifos at 95~C (615g) was ml~e~ wl h PAPI 135 (lOg) and emulsified into 440g wate-con,-_n~ng lOg Gohsenol GH20 and lOg Gohsenol GL05 at 45~~. An emulsion of about 1.4~m vmd was produced. To this was added a solution of tetraethylenepentamine (3g), At'~x 4913 (20g) in water (70g) to produce an enca_su'ated product containing about 600g/l chlorpyrifos wi -. ~ particle size of about 1.4~m. This product showed no s-~n~fican~ crystallisation after 2 weeks storage.
Example 10: Molten chlorpyrifos (615g) at 50~C was mixed with PAPI 135 (20g) and Solvesso 200 (200g) and emu s fied into 390g water containing 20g Atlox 4991 at 50~C. An emulsion of about 1.5~m vmd was produced. To thls was added a solution of diethylenetriamine (7g), A. ox 4913 (20g) in water (130g) to produce an encapsulated product containing about 45~ w/w chlorpyrifos with a particle size of about l.~m. This product showed no significant crystallisation after 2 weeks storage. A comparative example made by emu'slf1cation of the same quantity of chlorpyrifos and Solvesso 200 into the same surfactant solution but wi,:~o~t encapsulation crystallised on storage at laDo~atory temperature.
SUBSTITUT~ SHEE~ (RULE 26) .
CA 0226l034 1999-0l-l8 Example 11: Molten chlorpyrifos at 45~C (615g) was mixed with PAPI 135 (30g) and emulsified into 430g water containing 20g of a 10,000 mol wt 88% hydrolysed polyvinyl alcohol (PVA) and 20g Atlox 4913 at 45~C. An emulsion of about 1.65~m vmd was produced. To this was added a solution of diethylenetriamine ~10g) in water (70g) to produce an encapsulated product containing about 600g/l chlorpyrifos with a particle size of about 1.63~m.
This product showed no significant crystallisation after 4 weeks storage.
Example 12: Molten trifluralin at 50~C (462g) was mixed with PAPI 135 (7.4g) and emulsified into 430g water containing 60g polystyrene sulphonate (Sodium salt) a.
5C~C. .~n emulsion of about 6~m vmd was produced. To th s was added a solution of diethylenetriamine (2.5g) in warer (lOOg) to produce an encapsulated product conta ning about 45% w/w trifluralin. This product sr.owed no slgnificant crystailisation after 2 weeks storage. A comparative example made by emulsification of the same quantity of trifluralin into the same surfactant solution crystallised on standing overnight at laboratory temperature.
Example 13: Molten trifluralin at 50~C (515g) was mixed with PAPI 135 (8.2g) and emulsified into 380g water containing 67g polystyrene sulphonate (Sodium salt) at 50~C. An emulsion of about 9~m vmd was produced. To this was added a solution of diethylenetriamine (2.7g) in water (lOOg) to produce an encapsulated product containing about 45% w/w trifluralin. This product showed no significant crystallisation after 2 weeks storage. A comparative example made by emulsification of SUBSrITUT~ SHEET (RULE 26) CA 0226l034 l999-0l-l8 the same quantity of trlfluralln into the same surfactant solution crystallised on standing overnight at laboratory temperature.
S ExamPle 14: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (lOg) and emulsified into 450g water containing 80g polystyrene sulphonate (Sodium salt) at 50~C. An emulsion of about 4.2~m vmd was produced. To this was added a solution of diethylenetriamine (2.7g) in wate~ (lOOg) to produce an encapsulated product containing about 50~w/w chloripyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamPle 15. Molten chloripyrifos at 50~C (615g) was mixed with PAPI 135 (lOg) and emulsified into 450g water containing 125g PVP K-30 at 50~C. An emulsion of about 1.49~ vmd was produced. To ~his was added a solution of diethylenetriamine (2.7g) in water (lOOg) to produce an enca~sulated product containing about 50~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Exam~le 16. Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (lOg) and Hyvis 30 (30g) and emulsified into 450g water containing lOOg Sopropon T-36 at 50~C.
An emulsion of a~out 1.2~m vmd was produced. To this was added a solution of diethylenetriamine (2.5g) in water (lOOg) to produce an encapsulated product containing about 50~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Example 17. Molten chlorpyrifos at 50~C was mixed with Voronate M-220 (20g) and emulsified into 550g water YJBS~lTUTE SHEE~ (RULE 2S) .
CA 0226l034 1999-0l-l8 containing 100g Sopropon T-36 at 50~C. An emulsion of about 1.8~m vmd was produced. To this was added a solution of diethylenetriamine ~5g) in water (lOOg) to produce an encapsulated product containing about 47~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Example 18. Molten chlorpyrifos at 50~C (615g) was mixed with Voronate M-220 (30g) and emulsified into 400g water containing 40g Gohsenol GL03 at 50~C. An emulsion of about 1.84~m was produced. To this was added a solution of diethylenetriamine (lOg) in water (120g) to produce an encapsulated product containing about 51.5~wiw chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Exam~le 19 Molten chlorpyrifos at 50~C (615g) was mixed with Voronate M-220 (lOg) and emulsified into 300g water containing 20g Gohsenol GLO3 and Morwet EFW (5g) and 50~C. ~n emulsion of about 1.7~m vmd was produced. To this was added a solution of diethylenetriamine (3g) in water (250g) to produce an encapsulated product containing about 51~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamDle 20 Chlorpyrifos-methyl (42g) was dissolved in methyl oleate (20g) at 35~C and then added to 3g Voronate M-229. This oil phase was emulsified into 40g of water containing 4g Gohsenol GL03 at about 35~C to produce an emulsion of about 2.4~m vmd. To this was added lg diethylenetriamine in 10g water to produce an encapsulated product containing about 35% chlorpyrifos-methyl (about 53~ encapsulated oil).
SUBSrl~UT~ SltEE~ (RULE 26) W098/03065 pcTlGs97lol95 ExamPle 21 Chlorpyrifos-methyl was dissolved in Solvesso 200 (ZOg) at 35~C and then added to 3g Voronate M-229.
This oil phase was emulsified into 40g of water containing 4g Gohsenol GL03 at about 35~C to produce an emulsion of about l.9~m. To this was added lg diethylenetriamine in lOg water to produce an encapsulated product containing about 35~ chlorpyrifos-methyl (about 53~ encapsulated oil).
ExamPle 22 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) and Hyvis 30 (3g) at 35~C and then added to 3g Voronate M-229. This oil phase was emulsified into 40g of water containing 4g Gohsenol GLO3 at about 35~C to produce an emulsion of about 2.25~m vmd.
To this was added lg diethylenetriamine in lOg water to produce an encapsulated product containing about 34 chlorpyrifos-methyl (about 55~ encapsulated oil).
ExamPle 23 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) at 35~C and then added to lg Voronate M-229. This oil phase was emulsified into 40g of water containing 4g Gohsenol GLO3 at about 35~C to produce an emulsion of about 2.98~m vmd. To this was added 0.33g diethylenetriamine in lOg water to produce an encapsulated product con~aining about 35~ chlorpyrifos-methyl (about 53~ encapsulated oil).
Example 24 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) at 3S~C and then added to lg Voronate M-229. This oil phase was emulsified into 40g of water containing 8g Gohsenol GLO3 at about 35~C to produce an emulsion of about 0.69~m vmd. To this was added 0.33g dlethylenetriamine in lOg water to produce an SUBSTITUI~ SHEET (RULE 26) . .
CA 0226l034 1999-0l-l8 W098/03065 PCT/Gs97/01951 encapsulated product containing about 35% chlorpyrifos-methyl (about 55~ encapsulated oil).
ExamPle 25 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) at 35~C and then added to lg Voronate M-229. This oil phase was emulsified into 40g of water containing 6g Gohsenol GL03 at about 35~C to produce an emulsion of about 1.38~m vmd. To this was added 0.33g diethylenetriamine in lOg water to produce an encapsulated product containing about 35~ chlorpyrifos-methyl (about 55~ encapsulated oil).
Samples from examples 20-25 all stored for 2 weeks at -5~C showed no crystallisation whereas emulsions prepared from the same oil and aqueous phases showed crystallisation typical of supersaturated oil phases.
Exam~le 26 Chlorpyrifos (300g) and Lindane (120g) were dissolved in Trimethylcyclohexanone and Solvesso 100.
57g CL this oil phase was mixed with PAPI 135 (20g).
This was emulsified into 300g water containing Anonaid HF
(lOg) and Atlox 4991 (20g) to produce an emulsion of abou~ 0.62~m vmd. To this was added 7g diethylenetriamine and 30g Atlox 4913 in 150g water to produce a product containing 300g/1 chlorpyrifos and 120g/1 Lindane. This product was stored at -5~C for 1 week and then tested by dilution into cold water (5~C) and being passed through a 45~m sieve. No crystals were observed. A parallel study with an emulsion prepared by the same route resulted in gross crystallisation of both chlorpyrifos and Lindane in the same time period.
Exam~le 27 Molten chlorpyrifos (480g) was mixed with Voronate M-220 (25g), Solvesso 200 (107g) and Hyvis 04 SUBS~I~UT~ SHEE~ (RULE 26) (25g) and emulsified into 400g water containing 50g Gohsenol GL03. An emulsion of about 1.64~m vmd was produced. To this was added a solution of diethylenetriamine (18g) and propylene glycol (40g) in water (lOOg total) to produce an encapsulated product containing about 480g/1 chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamPle 28 Molten chlorpyrifos (480g) was mixed with Voronate M-220 (25g), Solvesso 200 (107g) and Hyvis 04 (25g) and emulsified into 400g water containing 45g Gohsenol GL03 and 30g Gohseran L-3266. An emulsion of about 0.82~m vmd was produced. To this was added a solution of diethylenetriamine (18g) and propylene glycol (40g) in water (lOOg total) to produce an encapsulated product containing about 480g/1 chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamDle 29 Trifluralin (55.9g) and ethalfluralin (11.3g) as a eutetic mixture were melted at 40~C and 7.5g of methylene diisocyanate was added thereto. This oil phase was added to water (60g) containing sodium polyacrylate (1.5g) at 40~C with high shear. An emulsion was produced of approximately 5~m vmd. To this was added diethylenetriamine (5g) in water (8.5g). The mixture was stirred at 40~C for thirty minutes. The capsules produced were storage stable.
SUBSTITUTE SHEET (RULE 26)
~This invention relates to a process for preparing an aqueous dispersion of polymeric microcapsules containing S a supersaturated solution or supercooled melt of water-insoluble materials. In particular, it is concerned with providing aqueous dispersions of pesticidal material which do not crystallise, so that a product with a high content of active material can be provided which is storage-stable. Storage-stable transportable aqueous dispersions of pesticides are provided which can be applied to crops and the like by conventional spray technlques .
~5It is well known to encapsulate highly water-insoluble pesticidal material in polymeric microcapsules, in order that the pesticidal material can be applied to cr~ps and the like. Such microcapsule formulations are commoniy provided in the form of spray-dried powders, whicn are rewetted prior to application. For example, US-A-~160530 (Griffin) discloses a process for encapsulating pesticides by melting the active material and combining the melted material with a film-forming polymer, such as a polyvinyl alcohol (PVA). The mat~rials are then emulsified together and spray-dried.
A similar method is disclosed in US-A-4244836 (Hoechst).
For some applications, however, liquid concentrates, -particularly aqueous concentrates, have substantial advantages over dry formulations. Aqueous concentrates are generally easier to formulate for field application, and generate reduced possibility of lnhalation by a user.
SU~STI~UTE S~IEET (RU~E 26) It lS known to prepare encapsulated pesticides as wet formulations, i.e. as an aqueous dispersion of microcapsules. However, such aqueous concentrates tend to have a lower loading of active ingredient, and therefore tend to be more costly to store and transport than corresponding dry formulations. For instance, US-A-4938797 includes an example of a wet formulation of microcapsules in which the suspension has an active ingredient content of 46% by weight.
It is known to prepare pesticide-containing dry microcapsules by carrying out the encapsulation process at an elevated temperature, either employing very low amoun~s of solvent (so that when the dispersion cools the pest~cide is encapsulated in the form of a supersaturated solution) or by encapsulating a melt of the pesticide resulting in microcapsules containing a supercooled melt.
~e have ~ound however that concentrated aqueous formulations of microcapsules containing supercooled melts or supersaturated solutions are not storage-stable, since, on storage at ambient temperatures, crystallisation of the pesticide occurs. This renders the formulation unusable.
Surprisingly, it has been discovered that storage-stable aqueous dispersions of microcapsules containing a high loading of active product in the form of supercooled melts or supersaturated solutions can be stabilised against crystallisation by providing that the microcapsules have a volume median particle size of not more than 6~m, preferably not more than 5~m, more preferably not more than 2~m. It has further been discovered that crystallisation of the active product from such dispersions can be reduced by avoiding the use SUBSTITUT~ SHEET (RULE ~6~
CA 0226l034 1999-0l-l8 - of surfactants which form micelles under the conditions of storage (and thereby facilitate transportation of the - water-insoluble material through the aqueous phase, resulting in crystallisation).
WO 95/07614 relates to the use of polymeric stab lisers to alter the chemical potential of emulsion particles in an oil-in-water emulsion, and thereby inhibit Ostwald ripening. The use of such stabilisers in suspension-emulsions is also disclosed, as are a number of aqueous dispersing agents for such dispersions, inc;uding a polyvinyl alcohol/polyvinyl acetate copolymer. This reference also discloses certain mic-ocapsule suspensions. There is no disclosure in WO
95/~7614 however of the desirability of selecting a non-micellising surfactant, and of the need to avoid sur-actants which do form micelles, in order to stabilise pa~ iculate dispersions. In fact, the surfactant used to sta~ilise the dispersions of microcapsules disclosed in ~O ~5/07614 is ATLOX 4991TM, an ethoxylated alcohol which is a micellising surfactant.
PCT/US95/15534 discloses the preparation of dry mic-ocapsules by spray-drying aqueous solutions of mic-ocapsules containing PVA surfactants. There ls no suggestion in PCT/US95/15534 however that the use of such surfactants (or the use of any non-micellising surfactant) is able to improve the long-term stability of aqueous formulations.
Accordingly, in a first aspect of the invention, there is provided a process for preparing a storage-stable aqueous dispersion of a water-insoLuble material, which process comprises emulsifying in water a non-SUBSTITUT~ SHEET (RlJLE 26) .
aqueous phase comprising a solution or a melt of the water-insoluble material, so as to form emulsion particles having a volume median particle size of not more than 6~m, and carrying out a polymerisation process to form from the emulsion particles an aqueous dispersion of microcapsules, the said microcapsules having the said water-insoluble material contained therein in the form of a supersaturated solution or a supercooled melt, and stabilising the dispersion with a non-micellising surfactant, wherein the stabilised dispersion is substantially free of micellising surfactant.
The amount and/or nature of the non-micellising surfactant may be such that the solubility of the water-insoluble material in the aqueous phase is not more thanlOOppm preferably not more than 50ppm, more preferably not more than 5ppm.
The term "non-micellising" as used herein is intended to mean a surfactant which does not form micelles (which facilitate transport of the water-insoluble material through the aqueous phase) under the conditions used to store the stabilised dispersion.
The process of the invention generally includes the step of storing the stabilised dispersion, for example after pac~aging in a closed container.
The condltions of storage may be any conditions appropriate to the particular dispersion and water-insoluble material, but will generally be ambient condi~ions.
SUBSTITUT~ SHEET (RULE 2~) The tendency of a surfactant to form mlcelles increases with the concentration of the surfactant. The point at which micelles are formed is known as the critical micelle concentration (CMC). In order to find the CMC for a particular surfactant, the surface tension of the surfactant is plotted against the log of its concentration. Those surfactants which readily form mlcelles, such as monomeric anionic and nonionic surfactants, typically show a quite rapid reduction in surface tension with concentration, until a specific cor.centration for that surfactant (the CMC) at which the reduction in surface tension ceases.
Such a plot is shown in Figure ~, which is a plot of surface tension against log concentration for an ethoxylated alcohol surfactant (shown as "-") and for a polyv r.yl alcohol (shown as "-"). It can be seen that the ethoxylated aLcohol forms micelles at and above a ConCentratlon of lO-2s ~w/w. By contrast, the curve for t~e DVA shows a gradually reducing surface ~ension with concer,.ration with no clear change in behaviour, indicative that no micelles are formed in this case. A
simple plot of surface tension against concentration can therefore be carried out to determine whether the surfactant forms micelles at the concentrations and under the conditions employed in the formulation.
Most surfactants are such that, under essentially all ~ractical conditions of use, they are "micellising"
and therefore unsuitable. Examples of such surfactants include nonionic surfactants such as fatty alcohol ethoxylates (alkoxylates), such as are employed in WO
9~/07614, fatty acid esters (and alkoxylates of fatty acid esters), alkoxylated amines, ethylene oxide-SUBSTITUT~ SHEET tRULE 26) propylene oxide copolymers, fatty acid alkoxylates (PAG
esters, specifically PEG esters), tall oil and rosin ester alkoxylates, alkyl phenol alkoxylates, substituted phenol alkoxylates; anionic surfactants such as dodecyl benzene sulphonic acid and its salts, alkyl sulphates, nonionic alkoyxlates phosphated or sulphated to produce the corresponding phosphate ester or ether sulphate ' respectively and cationic surfactants such as cetyl trimethyl ammonium chloride. Other micellising surfactants can be found in reference works such as "McCutcheons Emulsifiers & Detergents".
Clearly, there is a balance between the emulsifying e fect and the tendency to form micelles (both of which ncrease with surfactant concentration). It will be appreciated that, between preferred surfactants and unsuitable surfactants, there is a group of surfactants ~hich have some stabilising effect but which are not preferred.
A surfactant may be used which forms micelles under ~he process conditions, provided that it does not form micelles under the conditions of storage, since it is on storage that crystal isation generally takes place.
As indicated above, the "non-micellising surfactant"
is one which is able to stabilise the dispersion such that the dispersed microcapsules remain in suspension on extended storage.
Without wishing to be constrained by theory, it is thought that the surfactants in question inhibit transportation of the water-insoluble material through the aqueous phase, thereby reducing the likelihood of SUBSTITUT~ S~lEET (RULE 26) nucleatlon of the said material and of subsequent crystallisation. By contrast, those surfactants which have a strong ability to form micelles are thought to promote transportation of the water-insoluble material S through the aqueous phase, resulting in crystallisation.
In principle any surfactant can be used which has a sufficient emulsifying effect when employed at a concentration below its critical micelle concentration.
In practice, suitable surfactants tend to be polymeric surfactants of relatively high molecular weight, for example with 2 weight average molecular weight of at leas~ 10,000. Lignosulphates with a weight average molecular weight of at least 2,000 are also suitable.
A preferred stabilising surfactant a poly(vinyl pyrrolidone), a co-poly(vinyl alcohol/acetate~ PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyi pyrrol done/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(ca~boxyalkyl cellulose). A particularly preferred surfactant is a polyvinyl alcohol (~VA).
The aqueous dispersions of the present invention may be packaged in a closed container for shipping and transport purposes.
In a preferred embodiment, the stabilising surfactant is added prior to the polymerising step and, more preferably, prior to the emulsifying step.
SUBSTITUT~ SHEET (RULE ~6~
_ . . .. .
w098/03065 PCT/GB97101951 2article size (vmd) may be measured, for example, using a laser diffraction instrument, for example a Malvern Mastersizer~.
As used herein, the term "water-insoluble material"
means a material which has a solubility in water of not more than lOOppm, more preferably not more than 50ppm, more preferably still not more than 5ppm.
The polymerisable material is preferably polymerised in ar. interfacial reaction, and most preferably in an .nterfacial condensation reaction. In a preferred embodiment, the polymerisable material is a polyisocyanate which is polymerised by means of a condensation reaction with a polyamine.
Alternatively, the polymerisable material may be a crosslinkable material which is used to coat the emulsion par~ -ies by 2 coacervation method, and thereafter crosslinked to form the microcapsules.
Both interfacial and coacervation methods involve the preparation of an oil-in-water emulsion, followed by either a condensation reaction at the oil/water interface to produce a polymeric film, or the production of a coacervate which can then deposit on the oil surface, followed by film forming and hardening, which can take place by a variety of processes. The condensation reaction can for example be a multi-component reaction between, for example:
acid chlorides and polyamines isocyanates and polyamines, SUBSTITUT~ SHEET (RULE 26 rsocyanates and polyols, or mixtures or the above.
Coacervates can be formed by any of the processes t3ught in the art, for example using gelatine/gum arabic The microcapsules in accordance with the invention may be prepared by high shear mixing of a solution or a melt containing the water-insoluble material (e.g.
pesticide), preferably a PVA (as an aqueous solution) to enhance microcapsule formation, and one of the materials for forming the microcapsules (e.g. a polymerisable material for instance an isocyanate or a crosslinkable material). The PVA acts as an emulsifier, and in some systems, no further emulsifier may be required. It is desirable however to add additional emulsifiers, which may be of generally known type in order to produce the desired emulsion of small particle size (provided that tne emulsifiers are non-micellising as defined herein).
When the size of the emulsion is as desired, then the othe~ polymeric cross-linker is added (e.g. polyamine), to complete the interfacial polycondensation.
As indicated above, a preferred reactant for the polycondensation is a polyamine, which is usually a water soluble, reactive polyamine, such as diethylene triamine or tetraethylene pentamine. These amines start to react with the isocyanate at the interface as soon as they are added to the emulsion. More complete control can sometimes be achieved by using either a water-soluble amine salt, or an oil-soluble amine salt, dissolved respectively in the aqueous phase or the oil phase at an early stage in the process (for example, before emulsification). By virtue of the fact that they are SUBSTITUT~ SHEET (RULE 26~
WO 38~!~3~5 PCT/GB97/01951 salts, they do not immediately react with the isocyanate, but do so promptly when the pH is adjusted to liberate the free amine, whereupon cross-linking occurs.
The high shear mixing can be performed on a batch of the ingredients, or may be conducted continuously (in-line). In the former case, the time of addition or release of the reactive amine is governed by the processing time re~uired to form the emulsion with the correct particle size distribution (which clearly is ba~ch size dependent), whilst in the latter case, the interfacial reaction can be better controlled, since the amine can be added/released at any desired time simply by choice of injection point in the process stream, thus giving essentially complete control over the urea/urethane ratio.
In a preferred embodiment, an additional non-micellising surfactant is provided in the aqueous dispersion. The dispersion may also preferably comprise an antifreeze agent, for example an ethylene glycol or a propylene glycol.
The water-insoluble material is preferably a pesticidal material. The term "pesticidal material"
includes but is not limited to insecticidaL, miticidal, herbicidal and fungicidal materials.
Suitable insecticidal materials are:
acrinathrin allethrin alpha-cypermethrin amitraz azinphos-ethyl azinphos-methyl benfuracarb benzoximate beta-cypermethrin betacyfluthrin bifenthrin binapacryl SuBsrl~uT~SHEET(RUL~ ~
W098/03065 PCT/Gss7/o1ssl bicallethrin bioallethrin S bioresmethrin bioresmethrin bromophos bromopropylate - buprofezin butacarboxim butoxycarboxin cambda-cyhalothrin chlordimeform chlorfenvinphos chl~rflurazuron chlormephos chlorobenzilate chlorophoxim chloropropylate chlorpyrifos chlorpyrifos- cyanophos cycloprothrin methyl cyfluthrin cyhalothrin cypermethrin cyphenothrin deltamethrin demeton-S-methyl dichlorvos dicofol dinobuton dioxabenzafos dioxacarb disulfoton ed~fenphos empenthrin endosulfan EPNethiofencarb esfenvalerate ethoprophos etofenprox etrimphos fenamiphos fenazaquin fenitrothion fenobucarb ferpropathrin fenthiocarb fenthion fer.valerate flucythrinate flufenoxuron formothion gamma-HCH hexaflumuron hydroprene isofenphos isoprocarb isoxathion malathion mephospholan methidathion methoprene methoxychlor mevinphos N-2,3-dihydro-3- parathion methyl methyl-1,3-thiazol-2-ylidene-2,4-xylidene permethrin phenothrin phenthoate phosalone phosfolan phosmet pirimiphos-ethyl pirimiphos-methyl profenofos promecarb propaphos propargite propetamphos pyrachlofos quinalphos resmethrin tau-fluvalinate tefluthrin tefluthrin temephos terbufos terbufos tetrachlorinphos tetrachlorinphos SUBS~I~Un SHEET(RUL~ ~) W098/03065 PCT/Gss7/01951 tetradifon tetramethrin tralomethrin tralomethrin tralomethrin triazophos triazophos xylylcarb Suitable fungicidal materials are:
azaconazole benalaxyl biteranol bupirimate carboxin cyproconazole difenoconazole dimethomorph diniconazole ditalimfos dodemorph dodine epoxyconazole ethoxyquin etridiazole fenarimol fenpropidin fenpropimorph fluchloralin flusilazole imibenconazole myclobutanil myclobutanil nuarimol oxycarboxin penconazole prochloraz propiconazole pyrifenox tebuconazole tetraconazole tolclofos-methyl triadimefon triadimenol tridemorph triflumizole Sui~abie herbicidal materials are:
2,4-D esters 2,4-DB esters acetochlor aclonifen alachlor anilophos benfluralin benfuresate bensulide benzoylprop-ethyl bifenox bromoxynil bromoxynil esters butachlor butamifos butralin butylate carbetamide chlornitrofen chlorpropham cinmethylin clethodim clomazone clopyralid esters CMPP esters cycloate cycloxydim desmedipham dichlorprop esters diclofop-methyldiethatyl dimethachlor dinitramine ethalfluralin SUBSTITUl~ SHEET (RULE 26) CA 0226l034 1999-0l-l8 ethofumesate fenobucarb fenoxaprop ethyl fluazifop fluazifop-P fluchloralin flufenoxim flumetralin flumetralin fluorodifen fluoroglycofen fluoroxypyr esters ethyl flurecol butyl flurochloralin haloxyfop ethoxyethyl haloxyfop-methyl ioxynil esters isopropalin MCPA esters mecoprop-P esters metolachlor monalide napropamide nitrofen oxadiazon oxyfluorfen pendimethalin phenisopham phenmedipham picloram esters pretiiachlor profluralin propachlor propanil propaquizafop pyridate quizalofop-P triclopyr esters tridiphane tril~iuralin Par i_ularly suitable pesticidal materials are chlor?yrifos and trifluralin.
The aqueous dispersion may include an addltional pestlcidal material to that contained in the microcapsules. This additional pesticidal material may be present in solution, in the form of emulsion partlcles, as a dispersion of a solid, or contained wlthin microcapsules.
In a second aspect of the invention, there is provided a storage-stable aqueous dispersion of a water-insoluble material, wherein the water-insoluble material is contalned within microcapsules having a volume median par~icle size of not more than 6~m, preferably not more than ~m, more preferably not more than 2~m, in the form of a supersaturated solution or a supercooled melt, SUBSTITUTE SHEET (RULE 26) .
CA 0226l034 l999-0l-l8 WO 98/03065 PCT/GB97/OlgSl wherein the aqueous dispersion additionally comprises a non-micellising surfactant to stabilise the dispersion, and wherein the stabilised dispersion is substantially free from micellising surfactant.
~ referred non-micellising surfactants are described above.
The water-insoluble material (preferably a pesticidal material as described above) preferably constitutes at least 50% by weight of the aqueous dispersion, and most preferably at least 70% by weight.
When in supersaturated solution (such as in xylene or any other suitable solvent known in the art), the amount of tne said material is preferably at least 70% by weight of solution, most preferably at least 80% by weight of solution.
The aqueous dispersion may include an additional pesticide and/or an additional surfactant as described above.
The aqueous dispersion may be provided in a closed container.
In a third aspect of the invention there is provided the use of a non-micellising surfactant (as described above) to inhibit crystallisation of a water-insoluble material from an aqueous dispersion containing the said material, wherein the water-insoluble material is present in the dispersion in the form of microcapsules containing the said material as a supersaturated solution or a supercooled melt.
SUBSTITUT~ SHEET (RULE 26) ..
In a further aspect of the invention, there is provided a method for the control or eradication of a pest, which method comprises diluting an aqueous dispersion as described above to a pesticidally-effective concentration, and applying the resultant dispersion to the pest or to a locus in which the pest is to be cont-olled particularly, without any intervenin~ spray-drying step.
As indicated above, the method o~ the invention is particularly advantageous for the production of microcapsules having a small particle size, for example having a VMD of 6~m or less, particularly 2~m or less.
The chief advantage of such small capsules is that, as the VMD decreases, it is possible to retain the majority of the supercooled/supersaturated active in the liquid form. It is thus possible to produce in a reliable manner liquid core capsules ~ith the minimal use of solvents, which in turn gives environmental advantages, as well as a higher active loading in the final product.
~urther, such small capsules provide a higher surface area to mass ratio than larger particles, and thus give an enhanced release rate and better knock-down. Yet another benefit of such small capsules is that they can penetrate soil or surface grass thatch better than larger capsules, and so are more efficacious in certain applications where such soil or thatch mobility is needed.
The presence of a liquid core in capsules made with a supercooled molten active has several advantages, of which the most significant from point of view of the present invention is that the core does not crystallise, thus causing rupture of the capsules, which can lead both SUBSTITUT~ SHEET (RULE 26) W098/03065 PcT/Gsg7/01951 to premature release, and to formulation instability on storage. A second advantage is that a liquid core will in general release its active more rapidly than will a solid. This, combined with small particle size, gives a significant increase in active release rate. A third advantage of retaining the active in the liquid state is that there is no possibility of producing a biologically less active polymorph during crystallisation - a problem which is addressed in another way in US-A-5160530 (Griffin).
Any water-insoluble solvent may be employed to dissolve the water-insoluble material in the preparation of tr.e microcapsules if a solvent is deemed desirable.
The use of such solvents reduces the tendency of the said material to crystallise. Examples of typical solvents are a~omatic solvents, particularly alkyl substituted be~.zenes such as xylene or propyl benzene fractions, and mixed naphthalene and alkyl naphthalene fractions;
mineral oils; kerosene, dialkyl amides of fatty acids, particularly the dimethyl amides of fatty acids such as the dimethyl amide of caprylic acid; chlorinated aliphatic and aromatic hydrocarbons such as 1,1,1-trichloroethane and chlorobenzene, esters of glycol derivatives, such as the acetate of the n-butyl, ethyl, or methyl ether of diethyleneglycol, the acetate of the methyl ether of dipropyleneglycol, ketones such as isophorone and trimethylcyclohexanone tdihydroisophorone) and the acetate products such as hexyl, or heptylacetate.
The preferred organic liquids are xylene, propyl benzene fractions, alkyl acetates, and alkyl naphthalene fract~ons.
SUBSTITUT~ SHEET (RU~E 26 WO ~1'0~ 5 PCT/GB97/01951 .~aterlals may be employed which are normally solid at amblent temperatures, but which are capable of forming eutectic mixtures with the water-insoluble material. The use of such materials will generally reduce the tendency of the water-insoluble material to crystallise.
A further advantage of the encapsulation method in accordance with the invention is that it permits the production of aqueous compositions containing two or more active materia~s, where the materials are such that direct formulation of the materials (i.e., without encapsulation of one or both of them) would lead to a product which is chemically or physically unstable. In one aspect, the said actives may be separately encapsulated, but in an alternative and preferred embodiment, one or mor~ of the active materials (or some portion of a single active material) may be encapsulated by the method in accordance with the invention, and the balance not encapsulated, for example, simply dispersed in the aqueous phase. In this way, the un-encapsulated active material is immediately biologically available upon application, whereas the encapsulated material is released more slowly. The amount of each material employed in such different forms will vary dependent upon the particular application but in general terms, each such material may constitute from 0.1 to 99.9~ by weight of the total of the encapsulated material.
Compositions of the invention may also include a stabiliser of the kind disclosed in WO95/07614.
Other conventional additives may also be incorporated into the formulation such as emulsifiers, dispersants, and film-forming polymers (provided that SUBSrl~U~ SHEEt (RULE 263 CA 0226l034 l999-0l-l8 such additives do not form micelles under storage conditions).
A number of preferred embodiments of the invention are described in the following Examples.
The following materials were used in the Examples:
Trade Name Nature of Material Atlox 4913 nonionic surfactant Solvesso 200 aromatic solvent Sopro~an T-36 anionic copolymer Voranate M-220 isocyanate Voranate M-229 isocyanate PAPI 135 isocyanate Hyvis 30 poly~iso butylene) ~yvis 04 poly(iso butylene) Goherseran L-3266 anionically modified PVA
~orwe~ EFW anionic surfactant blend Gohsenol GH20 PVA 88% hydrolysed, high MW
Gohsenol GL05 PVA 88% hydrolysed, intermediate MW
Gohsenol GL03 PVA 88% hydrolysed, low MW
Example l: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (30g) and emulsified into 460g water containing lOg Gohsenol GH20 (an aqueous PVA solution) and lOg Gohsenol GL05 (an aqueous PVA solution) at 50~C.
An emulsion of about 2~m vmd was produced. To this was added a solution of diethylenetriamine (lOg), Atlox 4913 (20g) ln water (70g) to produce an encapsulated product containing a~out 600g/l chlorpyrifos. This product S'UBS~TUTE SHEET (RULE 26~
CA 0226l034 1999-0l-l8 showed no significant crystallisation after 2 weeks storage. A comparative example made by emulsification of the same quantity of chlorpyrifos into the same surfactant solution but without encapsulation, crystallised on standing overnight at laboratory temperature.
Example 2: Molten trifluralin at 50~C (615g) was mixed with PAPI 135 (30g) and emulsified into 365g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 50~C. An emulsion of about 3~m vmd was produced. To this was added a solution of diethylenetriamine (lOg~, Atlox 4913 (20g) in water (70g) to produce an encapsulated product containing about 600g/l trifluralin.
This product showed no significant crystallisation after 2 weeks storage. A comparative example made by emulsificatlon of the same quantity of trifluralin into the same surractant solution crystallised on standing overnight at laboratory temperature.
Example 3: The composition of Example 2 was repeated but emulsified at about 1.5~m and diluted to 500g/l.
This product also showed no significant crystallisation after 2 weeks storage.
~xample 4: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (30g) and emulsified into 440g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 50~C. An emulsion of about 2.5~m vmd was produced. To this was added a solution of diethylenetriamine (lOg), Atlox 4913 (20g) in water ~70g~ to produce an encapsulated product containing about 600g/l chlorpyrifos with a particle size of about 1.29~m. This product SUBSTITU~ SHEET (RUL~ 26) -WO 981'~3C65 PCT/GB97/01951 showed no signlficant crystallisation after 2 weeks s~orage.
Example 5: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (30g) and dioctyl phthalate (50g) and emulsified into 380g water containing lOg Gohsenol GH20 and lOg Gohsenol GL 0 5 at 50~C. An emulsion of about 1.4~m vmd was produced. To this was added a solution of diethylenetriamine (lOg), Atlox 4913 (20g) in water (70g) to produce an encapsulated product containing about ~OOg/1 chlorpyrifos with a particle size of about 1.38~m.
This product showed no significant crystallisation after 2 wee~s storage.
Exam~le 5: Molten chlorpyrifos at 55~C (462g) was mixed with Voronate M-220 (32g) and emulsified i~to 400g water containing 40g Poval 203 (PVA 88~ hydrolysed supplied by Kuraray) at 50~C. An emulsion of about 1.84~m vmd was produced. To this was added a solution of diethylenetriamine (8g) in water (98g) to produce an encapsulated product containing about 46% w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Example 7: Molten chlorpyrifos at 45~C (615g) was mixed with PAPI 135 (lOg) and emulsified into 440g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 45~C. An emulsion of about 1.4~ vmd was produced. To this was added a solution of diethylenetriamine (3.5g), Atlox 4913 (20g) in water (70g) to produce an encapsulated product containing about 600g/1 chlorpyrifos with a particle size of about 1.4~m. This product showed no significant crystallisation after 2 weeks storage.
SUBS~ SltEET (RULE 26) CA 0226l034 l999-0l-l8 ExzmDie 8: Molten chlorpyrifos at 45~C (615g) was mixed with PAPI 135 (20g) and emulsified into 440g water containing lOg Gohsenol GH20 and lOg Gohsenol GL05 at 45~C. An emulsion of about 1.4~m vmd was produced. To this was added a solution of diethylenetriamine (7g~, Atlsx 4913 (ZOg) in water (79g) to produce an encapsulated product containing about 600g/l chlorpyrifos with a particle size of about 1.4~m. This product showed no significant crystallisation after 2 weeks storage.
~xam?'e 9: Molten chlorpyrifos at 95~C (615g) was ml~e~ wl h PAPI 135 (lOg) and emulsified into 440g wate-con,-_n~ng lOg Gohsenol GH20 and lOg Gohsenol GL05 at 45~~. An emulsion of about 1.4~m vmd was produced. To this was added a solution of tetraethylenepentamine (3g), At'~x 4913 (20g) in water (70g) to produce an enca_su'ated product containing about 600g/l chlorpyrifos wi -. ~ particle size of about 1.4~m. This product showed no s-~n~fican~ crystallisation after 2 weeks storage.
Example 10: Molten chlorpyrifos (615g) at 50~C was mixed with PAPI 135 (20g) and Solvesso 200 (200g) and emu s fied into 390g water containing 20g Atlox 4991 at 50~C. An emulsion of about 1.5~m vmd was produced. To thls was added a solution of diethylenetriamine (7g), A. ox 4913 (20g) in water (130g) to produce an encapsulated product containing about 45~ w/w chlorpyrifos with a particle size of about l.~m. This product showed no significant crystallisation after 2 weeks storage. A comparative example made by emu'slf1cation of the same quantity of chlorpyrifos and Solvesso 200 into the same surfactant solution but wi,:~o~t encapsulation crystallised on storage at laDo~atory temperature.
SUBSTITUT~ SHEE~ (RULE 26) .
CA 0226l034 1999-0l-l8 Example 11: Molten chlorpyrifos at 45~C (615g) was mixed with PAPI 135 (30g) and emulsified into 430g water containing 20g of a 10,000 mol wt 88% hydrolysed polyvinyl alcohol (PVA) and 20g Atlox 4913 at 45~C. An emulsion of about 1.65~m vmd was produced. To this was added a solution of diethylenetriamine ~10g) in water (70g) to produce an encapsulated product containing about 600g/l chlorpyrifos with a particle size of about 1.63~m.
This product showed no significant crystallisation after 4 weeks storage.
Example 12: Molten trifluralin at 50~C (462g) was mixed with PAPI 135 (7.4g) and emulsified into 430g water containing 60g polystyrene sulphonate (Sodium salt) a.
5C~C. .~n emulsion of about 6~m vmd was produced. To th s was added a solution of diethylenetriamine (2.5g) in warer (lOOg) to produce an encapsulated product conta ning about 45% w/w trifluralin. This product sr.owed no slgnificant crystailisation after 2 weeks storage. A comparative example made by emulsification of the same quantity of trifluralin into the same surfactant solution crystallised on standing overnight at laboratory temperature.
Example 13: Molten trifluralin at 50~C (515g) was mixed with PAPI 135 (8.2g) and emulsified into 380g water containing 67g polystyrene sulphonate (Sodium salt) at 50~C. An emulsion of about 9~m vmd was produced. To this was added a solution of diethylenetriamine (2.7g) in water (lOOg) to produce an encapsulated product containing about 45% w/w trifluralin. This product showed no significant crystallisation after 2 weeks storage. A comparative example made by emulsification of SUBSrITUT~ SHEET (RULE 26) CA 0226l034 l999-0l-l8 the same quantity of trlfluralln into the same surfactant solution crystallised on standing overnight at laboratory temperature.
S ExamPle 14: Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (lOg) and emulsified into 450g water containing 80g polystyrene sulphonate (Sodium salt) at 50~C. An emulsion of about 4.2~m vmd was produced. To this was added a solution of diethylenetriamine (2.7g) in wate~ (lOOg) to produce an encapsulated product containing about 50~w/w chloripyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamPle 15. Molten chloripyrifos at 50~C (615g) was mixed with PAPI 135 (lOg) and emulsified into 450g water containing 125g PVP K-30 at 50~C. An emulsion of about 1.49~ vmd was produced. To ~his was added a solution of diethylenetriamine (2.7g) in water (lOOg) to produce an enca~sulated product containing about 50~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Exam~le 16. Molten chlorpyrifos at 50~C (615g) was mixed with PAPI 135 (lOg) and Hyvis 30 (30g) and emulsified into 450g water containing lOOg Sopropon T-36 at 50~C.
An emulsion of a~out 1.2~m vmd was produced. To this was added a solution of diethylenetriamine (2.5g) in water (lOOg) to produce an encapsulated product containing about 50~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Example 17. Molten chlorpyrifos at 50~C was mixed with Voronate M-220 (20g) and emulsified into 550g water YJBS~lTUTE SHEE~ (RULE 2S) .
CA 0226l034 1999-0l-l8 containing 100g Sopropon T-36 at 50~C. An emulsion of about 1.8~m vmd was produced. To this was added a solution of diethylenetriamine ~5g) in water (lOOg) to produce an encapsulated product containing about 47~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Example 18. Molten chlorpyrifos at 50~C (615g) was mixed with Voronate M-220 (30g) and emulsified into 400g water containing 40g Gohsenol GL03 at 50~C. An emulsion of about 1.84~m was produced. To this was added a solution of diethylenetriamine (lOg) in water (120g) to produce an encapsulated product containing about 51.5~wiw chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
Exam~le 19 Molten chlorpyrifos at 50~C (615g) was mixed with Voronate M-220 (lOg) and emulsified into 300g water containing 20g Gohsenol GLO3 and Morwet EFW (5g) and 50~C. ~n emulsion of about 1.7~m vmd was produced. To this was added a solution of diethylenetriamine (3g) in water (250g) to produce an encapsulated product containing about 51~w/w chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamDle 20 Chlorpyrifos-methyl (42g) was dissolved in methyl oleate (20g) at 35~C and then added to 3g Voronate M-229. This oil phase was emulsified into 40g of water containing 4g Gohsenol GL03 at about 35~C to produce an emulsion of about 2.4~m vmd. To this was added lg diethylenetriamine in 10g water to produce an encapsulated product containing about 35% chlorpyrifos-methyl (about 53~ encapsulated oil).
SUBSrl~UT~ SltEE~ (RULE 26) W098/03065 pcTlGs97lol95 ExamPle 21 Chlorpyrifos-methyl was dissolved in Solvesso 200 (ZOg) at 35~C and then added to 3g Voronate M-229.
This oil phase was emulsified into 40g of water containing 4g Gohsenol GL03 at about 35~C to produce an emulsion of about l.9~m. To this was added lg diethylenetriamine in lOg water to produce an encapsulated product containing about 35~ chlorpyrifos-methyl (about 53~ encapsulated oil).
ExamPle 22 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) and Hyvis 30 (3g) at 35~C and then added to 3g Voronate M-229. This oil phase was emulsified into 40g of water containing 4g Gohsenol GLO3 at about 35~C to produce an emulsion of about 2.25~m vmd.
To this was added lg diethylenetriamine in lOg water to produce an encapsulated product containing about 34 chlorpyrifos-methyl (about 55~ encapsulated oil).
ExamPle 23 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) at 35~C and then added to lg Voronate M-229. This oil phase was emulsified into 40g of water containing 4g Gohsenol GLO3 at about 35~C to produce an emulsion of about 2.98~m vmd. To this was added 0.33g diethylenetriamine in lOg water to produce an encapsulated product con~aining about 35~ chlorpyrifos-methyl (about 53~ encapsulated oil).
Example 24 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) at 3S~C and then added to lg Voronate M-229. This oil phase was emulsified into 40g of water containing 8g Gohsenol GLO3 at about 35~C to produce an emulsion of about 0.69~m vmd. To this was added 0.33g dlethylenetriamine in lOg water to produce an SUBSTITUI~ SHEET (RULE 26) . .
CA 0226l034 1999-0l-l8 W098/03065 PCT/Gs97/01951 encapsulated product containing about 35% chlorpyrifos-methyl (about 55~ encapsulated oil).
ExamPle 25 Chlorpyrifos-methyl (42g) was dissolved in Solvesso 200 (20g) at 35~C and then added to lg Voronate M-229. This oil phase was emulsified into 40g of water containing 6g Gohsenol GL03 at about 35~C to produce an emulsion of about 1.38~m vmd. To this was added 0.33g diethylenetriamine in lOg water to produce an encapsulated product containing about 35~ chlorpyrifos-methyl (about 55~ encapsulated oil).
Samples from examples 20-25 all stored for 2 weeks at -5~C showed no crystallisation whereas emulsions prepared from the same oil and aqueous phases showed crystallisation typical of supersaturated oil phases.
Exam~le 26 Chlorpyrifos (300g) and Lindane (120g) were dissolved in Trimethylcyclohexanone and Solvesso 100.
57g CL this oil phase was mixed with PAPI 135 (20g).
This was emulsified into 300g water containing Anonaid HF
(lOg) and Atlox 4991 (20g) to produce an emulsion of abou~ 0.62~m vmd. To this was added 7g diethylenetriamine and 30g Atlox 4913 in 150g water to produce a product containing 300g/1 chlorpyrifos and 120g/1 Lindane. This product was stored at -5~C for 1 week and then tested by dilution into cold water (5~C) and being passed through a 45~m sieve. No crystals were observed. A parallel study with an emulsion prepared by the same route resulted in gross crystallisation of both chlorpyrifos and Lindane in the same time period.
Exam~le 27 Molten chlorpyrifos (480g) was mixed with Voronate M-220 (25g), Solvesso 200 (107g) and Hyvis 04 SUBS~I~UT~ SHEE~ (RULE 26) (25g) and emulsified into 400g water containing 50g Gohsenol GL03. An emulsion of about 1.64~m vmd was produced. To this was added a solution of diethylenetriamine (18g) and propylene glycol (40g) in water (lOOg total) to produce an encapsulated product containing about 480g/1 chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamPle 28 Molten chlorpyrifos (480g) was mixed with Voronate M-220 (25g), Solvesso 200 (107g) and Hyvis 04 (25g) and emulsified into 400g water containing 45g Gohsenol GL03 and 30g Gohseran L-3266. An emulsion of about 0.82~m vmd was produced. To this was added a solution of diethylenetriamine (18g) and propylene glycol (40g) in water (lOOg total) to produce an encapsulated product containing about 480g/1 chlorpyrifos. This product showed no significant crystallisation after 2 weeks storage.
ExamDle 29 Trifluralin (55.9g) and ethalfluralin (11.3g) as a eutetic mixture were melted at 40~C and 7.5g of methylene diisocyanate was added thereto. This oil phase was added to water (60g) containing sodium polyacrylate (1.5g) at 40~C with high shear. An emulsion was produced of approximately 5~m vmd. To this was added diethylenetriamine (5g) in water (8.5g). The mixture was stirred at 40~C for thirty minutes. The capsules produced were storage stable.
SUBSTITUTE SHEET (RULE 26)
Claims
1. A process for preparing a storage-stable aqueous dispersion of a water-insoluble material, which process comprises emulsifying in water a non-aqueous phase comprising a solution or a melt of the water-insoluble material, so as to form emulsion particles having a volume median particle size of not more than 6µm, and carrying out a polymerisation process to form from the emulsion particles an aqueous dispersion of microcapsules, the said microcapsules having the said water-insoluble material contained therein in the form of a supersaturated solution or a supercooled melt, and stabilising the dispersion with a non-micellising surfactant, wherein the stabilised dispersion is substantially free of micellising surfactant.
2. A process as claimed in Claim 1, including the step of storing the stabilised dispersion.
3. A process as claimed in Claim 1 or Claim 2, including the step of packaging the said aqueous dispersion in a closed container.
4. A process as claimed in any one of the preceding claims, wherein the said volume median particle size is not more than 5µm.
5. A process as claimed in Claim 4, wherein the said volume median particle size is not more than 2µm.
5. A process as claimed in any one of the preceding claims, wherein the surfactant is added prior to the said polymerisation process.
7. A process as claimed in any one of the preceding claims, wherein the surfactant is added prior to the said emulsification step.
8. A process as claimed in any one of the preceding claims, wherein the surfactant is a polymeric surfactant with a weight average molecular weight of at least 10,000.
9. A process as claimed in any one of the preceding claims, wherein the surfactant is a poly(vinyl pyrrolidone), a co-poly(vinyl alcohol/acetate) PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyl pyrrolidone/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(carboxyalkyl cellulose).
10. A process as claimed in any one of Claims 1 to 7, wherein the surfactant is a lignosulphonate with a weight average molecular weight of at least 2,000.
11. A process as claimed in any one of the preceding ciaims, wherein the microcapsules are formed by polymerising a polymerisable material in an interfacial reaction or by coating the emulsion particles with a crosslinkable material by a coacervation method, and thereafter crosslinking the said crosslinkable material.
12. A process as claimed in Claim 11, wherein the interfacial reaction is a condensation reaction.
13. A process as claimed in any one of the preceding claims, wherein the water-insoluble material is a pesticidal material.
14. A process as claimed in Claim 13 wherein the aqueous dispersion includes an additional pesticidal material.
15. A process as claimed in Claim 14, wherein the said additional pesticidal material is present in solution, in the form of emulsion particles, as a dispersion of a solid, or is contained within microcapsules.
16. A process as claimed in any one of the preceding claims, wherein the aqueous dispersion includes an additional non-micellising surfactant.
17. A process as claimed in any one of the preceding claims, wherein the aqueous dispersion includes an antifreeze agent.
18. A storage-stable aqueous dispersion of a water-insoluble material, wherein the water-insoluble material is contained within microcapsules having a volume median particle size of not more than 6µm in the form of a supersaturated solution or a supercooled melt, wherein the aqueous dispersion additionally comprises a non-micellising surfactant to stabilise the dispersion, and wherein the stabilised dispersion is substantially free from micellising surfactant.
19. An aqueous dispersion as claimed in Claim 18, which is packaged in a closed container.
20. An aqueous dispersion as claimed in Claim 18 or Claim 19, wherein the surfactant is a polymeric surfactant with a weight average molecular weight of at least 10,000.
21. An aqueous dispersion as claimed in any one of Claims 18 to 20, wherein the surfactant is a polylvinyl pyrrolidone), a co-poly(vinyl alcohol/acetate) PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyl pyrrolidone/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(carboxyalkyl cellulose).
22. An aqueous dispersion as claimed in any one of Claims 18 or 19, wherein the surfactant is a lignosulphonate with a weight average molecular weight of at least 2,000.
23. An aqueous dispersion as claimed in any one of Claims 18 to 22, which includes an additional non-micellising surfactant.
24. An aqueous dispersion as claimed in any one of Claims 18 to 23, wherein the water-insoluble material is a pesticidal material.
25. An aqueous dispersion as claimed in Claim 24, additionally comprising an additional pesticidal material dispersed in the aqueous phase.
26. The use of a non-micellising surfactant to inhibit crystallisation of a water-insoluble material from an aqueous dispersion containing that material, wherein the water-insoluble material is present in the dispersion in the form of microcapsules containing the said material as a supersaturated solution or a supercooled melt.
27. The use as claimed in Claim 26, wherein the surfactant is a poly(vinyl pyrrolidone), a copoly(vinyl alcohol/acetate) PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyl pyrrolidone/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(carboxyalkyl cellulose).
28. A method for the control or eradication of a pest, which method comprises diluting an aqueous dispersion as claimed in Claim 24 or Claim 25 to a pesticidally-effective concentration, and applying the resultant dispersion to the pest or to a locus in which the pest is to be controlled.
29. A method of treating a pest using an aqueous dispersion of a pesticidal material as claimed in Claim 24 or Claim 25 which is packaged in a closed container, comprising removing the said dispersion from the container, diluting the said dispersion to a pesticidally-effective concentration, and applying the resultant dispersion to the pest.
2. A process as claimed in Claim 1, including the step of storing the stabilised dispersion.
3. A process as claimed in Claim 1 or Claim 2, including the step of packaging the said aqueous dispersion in a closed container.
4. A process as claimed in any one of the preceding claims, wherein the said volume median particle size is not more than 5µm.
5. A process as claimed in Claim 4, wherein the said volume median particle size is not more than 2µm.
5. A process as claimed in any one of the preceding claims, wherein the surfactant is added prior to the said polymerisation process.
7. A process as claimed in any one of the preceding claims, wherein the surfactant is added prior to the said emulsification step.
8. A process as claimed in any one of the preceding claims, wherein the surfactant is a polymeric surfactant with a weight average molecular weight of at least 10,000.
9. A process as claimed in any one of the preceding claims, wherein the surfactant is a poly(vinyl pyrrolidone), a co-poly(vinyl alcohol/acetate) PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyl pyrrolidone/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(carboxyalkyl cellulose).
10. A process as claimed in any one of Claims 1 to 7, wherein the surfactant is a lignosulphonate with a weight average molecular weight of at least 2,000.
11. A process as claimed in any one of the preceding ciaims, wherein the microcapsules are formed by polymerising a polymerisable material in an interfacial reaction or by coating the emulsion particles with a crosslinkable material by a coacervation method, and thereafter crosslinking the said crosslinkable material.
12. A process as claimed in Claim 11, wherein the interfacial reaction is a condensation reaction.
13. A process as claimed in any one of the preceding claims, wherein the water-insoluble material is a pesticidal material.
14. A process as claimed in Claim 13 wherein the aqueous dispersion includes an additional pesticidal material.
15. A process as claimed in Claim 14, wherein the said additional pesticidal material is present in solution, in the form of emulsion particles, as a dispersion of a solid, or is contained within microcapsules.
16. A process as claimed in any one of the preceding claims, wherein the aqueous dispersion includes an additional non-micellising surfactant.
17. A process as claimed in any one of the preceding claims, wherein the aqueous dispersion includes an antifreeze agent.
18. A storage-stable aqueous dispersion of a water-insoluble material, wherein the water-insoluble material is contained within microcapsules having a volume median particle size of not more than 6µm in the form of a supersaturated solution or a supercooled melt, wherein the aqueous dispersion additionally comprises a non-micellising surfactant to stabilise the dispersion, and wherein the stabilised dispersion is substantially free from micellising surfactant.
19. An aqueous dispersion as claimed in Claim 18, which is packaged in a closed container.
20. An aqueous dispersion as claimed in Claim 18 or Claim 19, wherein the surfactant is a polymeric surfactant with a weight average molecular weight of at least 10,000.
21. An aqueous dispersion as claimed in any one of Claims 18 to 20, wherein the surfactant is a polylvinyl pyrrolidone), a co-poly(vinyl alcohol/acetate) PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyl pyrrolidone/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(carboxyalkyl cellulose).
22. An aqueous dispersion as claimed in any one of Claims 18 or 19, wherein the surfactant is a lignosulphonate with a weight average molecular weight of at least 2,000.
23. An aqueous dispersion as claimed in any one of Claims 18 to 22, which includes an additional non-micellising surfactant.
24. An aqueous dispersion as claimed in any one of Claims 18 to 23, wherein the water-insoluble material is a pesticidal material.
25. An aqueous dispersion as claimed in Claim 24, additionally comprising an additional pesticidal material dispersed in the aqueous phase.
26. The use of a non-micellising surfactant to inhibit crystallisation of a water-insoluble material from an aqueous dispersion containing that material, wherein the water-insoluble material is present in the dispersion in the form of microcapsules containing the said material as a supersaturated solution or a supercooled melt.
27. The use as claimed in Claim 26, wherein the surfactant is a poly(vinyl pyrrolidone), a copoly(vinyl alcohol/acetate) PVA, a co-poly(vinyl pyrrolidone/acetate), a co-poly(vinyl pyrrolidone/acetate/alcohol), a co-poly(acrylic acid/graft polyethyleneoxide), a co-poly(alkyl(meth)acrylate), a lignosulphonate, a co-poly(maleic anhydride/methyl vinyl ether), a co-poly(maleic anhydride/diisobutylene), a carboxylated PVA, a poly(styrene sulphonate), a poly(alkyl cellulose) or a poly(carboxyalkyl cellulose).
28. A method for the control or eradication of a pest, which method comprises diluting an aqueous dispersion as claimed in Claim 24 or Claim 25 to a pesticidally-effective concentration, and applying the resultant dispersion to the pest or to a locus in which the pest is to be controlled.
29. A method of treating a pest using an aqueous dispersion of a pesticidal material as claimed in Claim 24 or Claim 25 which is packaged in a closed container, comprising removing the said dispersion from the container, diluting the said dispersion to a pesticidally-effective concentration, and applying the resultant dispersion to the pest.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GBGB9615158.4A GB9615158D0 (en) | 1996-07-19 | 1996-07-19 | Process for preparing storage-stable pesticide dispersion |
| GB9615158.4 | 1996-07-19 | ||
| PCT/GB1997/001951 WO1998003065A1 (en) | 1996-07-19 | 1997-07-18 | Process for preparing storage-stable pesticide dispersion |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2261034A1 true CA2261034A1 (en) | 1998-01-29 |
Family
ID=10797159
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002261034A Abandoned CA2261034A1 (en) | 1996-07-19 | 1997-07-18 | Process for preparing storage-stable pesticide dispersion |
Country Status (10)
| Country | Link |
|---|---|
| EP (1) | EP0915649A1 (en) |
| JP (1) | JP2000514819A (en) |
| KR (1) | KR20000067905A (en) |
| CN (1) | CN1228675A (en) |
| AU (1) | AU3554497A (en) |
| BR (1) | BR9710499A (en) |
| CA (1) | CA2261034A1 (en) |
| GB (1) | GB9615158D0 (en) |
| IL (1) | IL128137A0 (en) |
| WO (1) | WO1998003065A1 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW561064B (en) * | 1998-03-05 | 2003-11-11 | Sumitomo Chemical Co | Method for microencapsulating of a solid substance |
| GB9817354D0 (en) * | 1998-08-11 | 1998-10-07 | Agrevo Env Health Ltd | Liquid formulation |
| KR100722839B1 (en) * | 1999-06-18 | 2007-05-30 | 다우 아그로사이언시즈 엘엘씨 | A method to produce pesticide suspension concentrates |
| EP2001910B1 (en) * | 2006-03-30 | 2017-05-17 | Solvay USA Inc. | Reactive monomeric surfactants |
| BRPI1013359A8 (en) * | 2009-03-04 | 2016-09-20 | Dow Agrosciences Llc | MICROENCAPSULATED INSECTICIDE FORMULATIONS. |
| CN103998102A (en) | 2011-10-19 | 2014-08-20 | 罗门哈斯公司 | Encapsulation of personal care actives |
| EP3137206B1 (en) * | 2014-04-29 | 2019-11-27 | Basf Se | Process for producing microcapsules |
| EA202191202A1 (en) * | 2018-11-13 | 2021-07-27 | Ариста Лайфсайенс Инк. | PROCESS AND PRODUCT OF CYCLOHEXANDIONES |
| CN111972422B (en) * | 2019-05-21 | 2022-10-25 | 江苏龙灯化学有限公司 | Weeding composition containing microcapsules and preparation method and application thereof |
| CN111972415A (en) * | 2019-05-21 | 2020-11-24 | 江苏龙灯化学有限公司 | Weeding composition containing microcapsules and preparation method and application thereof |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4280833A (en) * | 1979-03-26 | 1981-07-28 | Monsanto Company | Encapsulation by interfacial polycondensation, and aqueous herbicidal composition containing microcapsules produced thereby |
| EP0214936B1 (en) * | 1985-09-13 | 1992-07-08 | Ciba-Geigy Ag | Process for producing microcapsules |
| US5160530A (en) * | 1989-01-24 | 1992-11-03 | Griffin Corporation | Microencapsulated polymorphic agriculturally active material |
| EP0551796B1 (en) * | 1992-01-03 | 1997-08-13 | Novartis AG | Microcapsule suspension and a process for its preparation |
| WO1994013139A1 (en) * | 1992-12-04 | 1994-06-23 | E.I. Du Pont De Nemours And Company | Microcapsule formulations of agricultural chemicals |
| KR100313589B1 (en) * | 1993-02-09 | 2002-11-29 | 노바티스 아게 | Process for the preparation of microcapsules |
| GB9319129D0 (en) * | 1993-09-15 | 1993-11-03 | Dowelanco Ltd | Storage and dilution of stable aqueous dispersions |
| GB9414318D0 (en) * | 1994-07-15 | 1994-09-07 | Dowelanco Ltd | Preparation of aqueous emulsions |
| GB9501017D0 (en) * | 1995-01-19 | 1995-03-08 | Dowelanco | Microencapsulation process and product |
-
1996
- 1996-07-19 GB GBGB9615158.4A patent/GB9615158D0/en active Pending
-
1997
- 1997-07-18 JP JP10506692A patent/JP2000514819A/en active Pending
- 1997-07-18 WO PCT/GB1997/001951 patent/WO1998003065A1/en not_active Application Discontinuation
- 1997-07-18 BR BR9710499A patent/BR9710499A/en unknown
- 1997-07-18 EP EP97931965A patent/EP0915649A1/en not_active Withdrawn
- 1997-07-18 IL IL12813797A patent/IL128137A0/en unknown
- 1997-07-18 CA CA002261034A patent/CA2261034A1/en not_active Abandoned
- 1997-07-18 KR KR1019997000360A patent/KR20000067905A/en not_active Application Discontinuation
- 1997-07-18 CN CN97197515A patent/CN1228675A/en active Pending
- 1997-07-18 AU AU35544/97A patent/AU3554497A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| AU3554497A (en) | 1998-02-10 |
| GB9615158D0 (en) | 1996-09-04 |
| IL128137A0 (en) | 1999-11-30 |
| EP0915649A1 (en) | 1999-05-19 |
| BR9710499A (en) | 1999-09-24 |
| JP2000514819A (en) | 2000-11-07 |
| KR20000067905A (en) | 2000-11-25 |
| WO1998003065A1 (en) | 1998-01-29 |
| CN1228675A (en) | 1999-09-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |