Classifications

• • 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
  • B01J13/18—In situ polymerisation with all reactants being present in the same phase
• • 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

Definitions

• the present invention concerns a icroencapsulated agrochemical, compositions containing it and processes for its production.
• formulations are desirable which optimise the effect of the active ingredient on the target organism whilst at the same time minimising its effect on the environment, particularly with respect to animals and plants which are not targeted.
• One such formulation technique which in recent years has been extensively investigated with respect to agrochemicals is microencapsulation.
• Various techniques for microencapsulation have been known for some time particularly in connection with pharmaceuticals and dyestuffs.
• USP 3,516,941 describes the use of urea-formaldehyde (UF) resins for encapsulating water insoluble fill material including agrochemicals.
• UF urea-formaldehyde
• USP 4,105,823 describes the use of UF and melamine-formaldehyde (MF) precondensates for crosslinking with other soluble polymers to microencapsulate finely divided particulate material.
• MF melamine-formaldehyde
• USP 4,534,783 describes a discontinuous two-phase microencapsulation procedure for water soluble materials including agrochemicals.
• USP 4,557,755 describes microencapsulation of agrochemicals employing a cationic urea resin forming polyco ⁇ densates with UF, MF or thioureaformaldehyde (TUF) prepolymers.
• a particular problem encountered with certain agrochemicals especially herbicides when applied to the soil is their tendency to leach rapidly from the target zone when subjected to rainfall or irrigation particularly in lighter soils which include coarse to moderately coarse texture soils and soils of low organic matter content, e.g. ⁇ 2.0 weight X organic matter.
• This problem usually precludes or restricts the use of such agrochemicals for preemergent application.
• persistence in the soil zone where germination of early weeds occurs can only be achieved, if at all, by repeated application or application at higher rates which increase the risk of damage to young crop plants or is uneconomical and environmentally undesirable.
• the present invention therefore provides a process for microencapsulating a rapidly leaching agrochemical comprising the steps of a) adding to a suspension of the agrochemical in a liquid a urea-, thiourea- or melamine-formaldehyde prepolymer or mixtures thereof and
• This microencapsulation process may be carried out in a single stage or in successive stages by repeating steps a) and b).
• the invention concerns an agricultural composition
• a further aspect of the invention concerns a method of controlling undesirable pests or plant growth which comprises applying to the locus or anticipated locus of said undesirable pests or plant growth an effective amount of a rapidly leaching agrochemical microencapsulated in a crosslinked urea-, thiourea- or melamine-formaldehyde prepolymer or mixed prepolymer.
• a further aspect of the invention concerns new, very sparingly soluble salt forms of rapidly leaching agrochemicals.
• Microencapsulation according to the invention is particularly suited for agrochemicals where the usual locus of the pests or undesired plant growth to be combatted is in the upper layers of the soil. Microcapsules according to the invention can also be used in watery loci such as mosquito breeding areas or paddy fields.
• Microencapsulation according to the invention is especially suited to agrochemicals where rapid leaching ability would normally preclude or restrict pre-emergent long lasting application.
• agrochemicals are those containing a carboxylic acid group.
• Preferred examples of such compounds are herbicides particularly pre-emergent herbicides such as benzoic acid and phenoxycarboxylic acid derivatives e.g. dicamba, MCPA, 2,4-D or as well as other herbicides e.g.
• the agrochemical may be in a solid crystalline or amorphous form or in liquid form, e.g. an oil.
• the agrochemical can be soluble in the liquid in which it is suspended, but in these cases, the agrochemical must be present in excess amount, i.e. the liquid should be super-saturated with agrochemical.
• This application is especially directed, therefore, to salt forms of the aforementioned herbicides which are only sparingly soluble in the liquid, e.g. water, in which they are suspended, e.g. inorganic salts such as sodium, potassium, calcium, copper, iron, aluminium or organic salts such as dimethylamine, aminopropylmorpholine, and the fatty amine organic salts having carbon chains of fourteen or more atoms such as the triamylamine, tridecylamine, dimethyldodecylamine, Adogen* (primary, n-alyl, C 16 ave.) and Primene R (primary tert-alkyl, C ⁇ 4 ave.) salt forms.
• Preferred salt forms are those which are only sparingly water soluble and are stable under hydrolytic conditions, e.g. the aluminium, iron, copper and calcium salts.
• aluminium and iron i.e. the Al(III) and Fe(III) salt forms of dicamba, MCPA and 2,4-D are the preferred salt forms. It is believed that the aluminium salt of MCPA and the Fe(III) salt of MCPA and dicamba are novel.
• Such salt forms can be prepared according to conventional and known procedures for preparing aluminium or iron salts of compounds that bear a carboxylic acid group, e.g. by combining the compound with a desired metal e.g. FeCl 3 or A1C1 3 in solution. In some situations, metal complexes of the compounds will be formed.
• This application is also especially directed to herbicides which are only sparingly soluble in water, e.g. alachlor, acetochlor, metolachlor and 2-chloro-N-[l-methyl-2-methoxy]-N-(2,4-dimethyl- thien-3-yl)acetamide.
• Suitable liquids for suspending the agrochemical are inert and are typically selected such that the agrochemical is only sparingly soluble therein while the prepolymer or prepolymer mix is miscible therein.
• the liquid will be water, although organic liquids that are inert and in which the prepolymer or prepolymer mix is miscible are also envisaged.
• urea- or melamine-formaldehyde resins and prepolmyers or mixtures thereof that are miscible in the liquid in which the agrochemical is suspended
• melamine-formaldehyde resins and prepolymers being especially preferred optionally mixed with urea-formaldehyde prepolmyers.
• MF melamine-formaldehyde
• UF urea-formaldehyde prepolymers
• the agrochemical in sparingly soluble form e.g. preferably in a form that is less than 2 X by weight soluble in the liquid in which it is suspended, more preferably less than 1 % by weight soluble.
• agrochemicals capable of forming salts with bases for example crystalline salts with heavier metals such as aluminium or iron are preferred.
• the desired particle size of the material to be encapsulated will vary according to the nature of the material, its intended use and prepolymer employed. As a rule satisfactory results are obtained with crystal particle sizes from 1 to 20 ⁇ , preferably 1 to 5, more preferably 2 or 3, especially ca. 2 ⁇ .
• microcapsules The desired particle size and active ingredient content of the finished microcapsules will also depend on intended applications. Satisfactory results are obtained with microcapsules of between 1 and 120 y, especially 10 to 50 ⁇ , particularly 10 to 25 ⁇ having active ingredient content of 10 to 60 X a.i. especially 25 to 35 X for use in crops. Considerably lower a.i. content of e.g. 1 to 2.5 X may also be employed for example where use in home gardens or lawns is envisaged or where the active ingredient is highly active at low concentrations.
• the desired particle size can be achieved by milling of finished agglomerated microencapsulate product or preferably by controlled crosslinking by employing multi-step addition/curing of prepolymers.
• the material to be encapsulated is suspended or slurried in a liquid, preferably water. It is a property of rapidly leaching agrochemicals that they exhibit relatively high solubility in water. Thus when practising the process of the invention it is desirable to have the agrochemical in a form which is of reduced solubility in order to provide an optimal amount of material available for microencapsulation. More soluble salt forms may be also used but are subject to stricter control of solvent amount or repeated recycling to obtain a higher percent content of a.i. if desired.
• the suspension of a.i. may be encapsulated to be not too strongly acid at the initiation of polymerization, e.g. to have a pH of >4, especially >5.0.
• a pH of >4 especially >5.0.
• the desired pH is achieved by having the a.i. in a crystalline form which upon suspension in the desired solvent results in the pH desired, e.g. in the form of the aluminium or iron salt.
• the suspension may optionally contain further additives such as dispersants, surfactants, antifoaming agents, etc., e.g. those based on naphthalene sulphonates or acetylenic diols.
• further additives such as dispersants, surfactants, antifoaming agents, etc., e.g. those based on naphthalene sulphonates or acetylenic diols.
• the suspension is preferably in the form of a slurry which may be wet-milled, e.g. by pebble milling.
• the UF/TUF/MF resins or mixtures thereof are employed in the form of prepolymers. This has the advantage of allowing elimination of undesirable traces of unpolymerized urea, thiourea, melamine and formaldehyde prior to use in the microen ⁇ capsulation process.
• the prepolymer or prepolymer mix is preferably added in the same liquid used to form the slurry and is miscible in such liquid, usually water.
• miscible is meant that the prepolymer or prepolymer mix is capable of mixing or dissolving in the liquid such that it surrounds the suspended agrochemical when polymerization is initiated.
• Addition of the desired amount of prepolymer can be carried out in one aliquot or in a series of lesser aliquots with curing after each addition. This latter procedure facilitates careful control of the particle size of the finished microcapsules and is preferred.
• prepolymer can be formed in situ according to known methods e.g. as referenced above, and the active ingredient then added.
• the ratio of prepolymer to active ingredient will vary according to the nature of the a.i. and the prepolymer themselves as well as the desired properties of the finished product. For some applications of finished product, satisfactory results are obtained with an excess of prepolymer e.g. a 1.5 to 6 fold, preferably 2 to 5 fold, especially 2 to 4 fold. For other applications of finished product, satisfactory results are obtained with an equivalent to excess amount of active ingredient, e.g. a weight ratio of prepolymer to active ingredient of 1:1 to 1:2. Thus, the weight ratio of prepolymer to active ingredient employed to prepare a finished product suitably varies from 6:1 to 1:2. Moreover, for some applications, the finished product may consist of a mixture of microcapsules having various prepolymer to active ingredient weight ratios.
• dicamba In cases where dicamba is employed as a.i., it is preferably employed in iron or aluminium salt form.
• Melamine-formaldehyde and urea-formaldehyde are preferred prepolymers and are preferably employed in a weight ratio of prepolymer to dicamba salt of 4:1 to 1:2, more preferably 2:1 to 1:1.
• Curing of the prepolymer or prepolymer mix can be accomplished in conventional manner, e.g. by warming or acid catalysis or both.
• curing is carried out by lowering pH with an acid, preferably a mild acid such as citric acid or fumaric acid to a pH below about 6, e.g. pH about 3-6, depending on the particular prepolymer and reaction conditions and warming to ca. 35° to 50°C for 2 to 10 hours with optional additional stirring at room temperature for ca. 24 hours.
• the pH is about 5 at the initiation of polymerisation and can subsequently be lowered to, e.g. 3.
• Microencapsulation may be accomplished in a single stage or in repeated stages, e.g. two, three, four or more stages depending on the desired release rate of agrochemical and/or particle size. Each successive stage is carried out by repeating the steps mentioned above, i.e. by adding a quantity of prepolymer to the reaction mixture and curing by warming or acid catalyst or both.
• microcapsules may be isolated from the reaction mixture in conventional manner e.g. by filtration and/or drying.
• microcapsules of the invention may be formulated in conventional manner, e.g. as dusts, granules, solutions, emulsions, wettable powders or flowables, suspensions and the like with conventional carriers and optionally other adjuvants. To prevent premature release of a.i. solid formulations are preferred.
• Such formulated microcapsules may be prepared in conventional manner e.g. by mixing, spray-drying and the like.
• microcapsules of the present invention is made according to conventional procedure to the weeds or pests or their locus using an effective equivalent amount of active ingredient.
• the effective amount will be based on the a.i. content and release profile of the microcapsules to correspond to the known effective application rate e.g. in the case of dicamba 0.05 to 2 lb/ac (approximately 0.055 to 2.2 kg/ha), especially 0.1 to 1 lb/ac (approximately 0.11 to 1.1 kg/ha).
• the optimum usage of the microcapsules of the present invention is readily by one of ordinary skill in the art using routine testing such as greenhouse testing and small plot testing.
• a half-life of from 30-45 days would be desirable (time required for 50 X of a.i. to be released from the microcapsule).
• Suitable formulations contain from 0.01 to 99 X by weight of active ingredient, from 0 to 20 % of surfactant and from 1 to 99.99 X of solid or liquid diluent(s). Higher ratios of surfactant to active ingredient are sometimes desirable and are achieved by incorporation into the formulation or by tank mixing.
• Application forms of a composition generally contain between 0.01 and 25 X by weight equivalent of active ingredient. Lower or higher levels of active ingredient can, of course, be present depending on the intended use, the physical properties of the microcapsules and the mode of application.
• Concentrate forms of a composition intended to be diluted before use generally contain between 2 and 90 X, preferably between 5 and 81 X by weight equivalent of active ingredient.
• microcapsules can be combined with a cyclodextrin to make a cyclodextrin inclusion complex for application to the pest or its locus.
• Agriculturally acceptable additives may be employed in the composition to improve performance and to reduce foaming, caking and corrosion, for example.
• surfactant as used herein means an agriculturally acceptable material which imparts emulsifiability, spreading, wetting, dispersibility or other surface-modifying properties.
• surfactants are sodium lignin sulfonate and lauryl sulfate.
• Dusts or granules means a liquid or solid agriculturally acceptable material used to dilute a concentrated material to a usable or desirable strength.
• talc kaolin or diatomaceous earth
• liquid concentrate forms for example a hydrocarbon such as xylene or an alcohol such as isopropanol
• microcapsule formulations may optionally contain further active ingredient such as herbicide, insecticides, acaricides, fungicides and the like.
• microcapsules according to the invention may be advantageous to formulate microcapsules according to the invention together with the same or other active ingredient in unencapsulated form to achieve initial control prior to the onset of controlled release from the microcapsules.
• unencapsulated material can for example be applied in the form of a spray dried coating on the microcapsules.
• premix or tank-mix of unencapsulated with encapsulated material can be appropriate.
• Combinations of unencapsulated and encapsulated material should be formulated in amounts and applied at rates sufficient to achieve initial weed control without causing undue crop damage.
• Dicamba satisfactory results are achieved when the unencapsulated form is applied at a rate ranging from abut 0.125 to 0.25 lb/ac (about 0.138 to 0.28 kg/ha) whilst the encapsulated form is applied at a rate of about 1.0 lb a.i./ac (about 1.1 kg a.i./ha).
• suitable weight ratios for formulations containing unencapsulated and encapsulated Dicamba range from 1:8 to 1:4 unencapsulated: encapsulated a.i.
• a formulation may consist of a mixture of microcapsules having various prepolymer to a.i. weight ratios.
• Combinations mentioned above can allow for effective, continuous control over periods as long as 1 to 75 days.
• the wet filter-cake of example la (dica ba-Al content ca. 40 g) is slurried with 50 ml of deionized water and 2.0 g of Morwet D425 (Sodium Naphthalene Formaldehyde Condensate - Petrochemicals Company, Inc.) was pebble milled for 9 hrs, a further 20 ml of deionized water and 0.5 g of Morwet D425 are added and milling continued for a further 2 hrs. to give a final median particle size of 3.7 ⁇ . This slurry is diluted with deionized water to 188 g.
• Morwet D425 Sodium Naphthalene Formaldehyde Condensate - Petrochemicals Company, Inc.
• urea-formaldehyde prepolymer prepared by refluxing 24 g of urea and 48 g of formaldehyde for 1 hr at 70° with stirring and diluting the result with 100 ml of deionized water
• 40 g of CYMEL R 385 Resin methylated melamine-formaldehyde resin formulation containing approximately 80 X by weight active resin, M.W. approximately 250, - American Cyanamid Company
• 2 g of citric acid dropping the pH of the slurry from 6.0 to 5.1.
• the temperature is slowly raised to 50° with a water bath. After stirring for 2% hrs the pH is 4.1.
• 110.5 g of technical dicamba acid are added with stirring to a mixture of 62.35 g of 45 X aq KOH and 95.65 g of deionized water.
• a mixture of 60.35 g of A1C1 3 -6H 2 0 in 125 g of deionized water is then added with stirring over a 5 minute period followed by further 10 g of deionized water.
• a further 31.16 g of 45 X aq. KOH and 10.33 g of deionized water are then added and the resulting mixture refluxed for 2 hours with stirring at 80°. The resulting mixture is then filtered.
• a slurry of the wet filter cake from Example 2a) (Dicamba-Al content ca. 30 g) is pebble milled with 115 g of deionized water 4 g of MORWET D425 and 3 drops of SURFYN0L R TG-E to a median particle size of 1.8 ⁇ .
• To this slurry is added 20 g of CYMEL 385 in 40 g of deionized water and 1 g of citric acid to pH 5.4 and the temperature raised (water bath) over a 2 hr period to ca. 40°. After cooling to ca 25° a further 20 g of CYMEL 385 in 50 g of deionized water are added and the temperature again raised to ca 40° over 1 hr. This procedure is repeated with a further 20 g of CYMEL 385 in 44 g of deionized water. After final cooling the mixture is filtered and the microcapsules dried at 54° to yield a median particle size 18.9 ⁇ .
• the active ingredient content of the microcapsules is determined by heating the capsules with concentrated HCl, diluting the resultant solution, and analysing by HPLC with external standard quantitation.
• the a.i. content of the capsules of Examples 1, 1.1, 2 and 3 is 33, 18.8, 33 and 31 X respectively.
• Aerosol 0TB American Cyanamid - Dioctylester of Na-Sulfosuccinic acid: 3 X and
• the inerts are preground before mixing with microcapsules to avoid capsule breakage.
• Velvetleaf, red root pigweed and morningglory seeds are planted and tilled ca. 2 inches (5.1 cm) deep and corn seed then sown.
• the microcapsules of Examples 1, 2 and 3 (as wettable powders) and Banvel R (dimethylamine salt of Dicamba - Sandoz Crop Protection Corporation) are then applied to the soil surface by spraying aqueous tank mix at a rate of 1 lb per acre (about 1.1 kg/ha dicamba acid equivalent) with 3 replications.
• 1 lb per acre about 1.1 kg/ha dicamba acid equivalent
• One inch (2.54 cm) of water is applied immediately after application followed by 1.25 inches (3.2 cm) 2 days later. Weed control and corn injury are evaluated 2 weeks after treatment.

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• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Pest Control & Pesticides (AREA)
• Environmental Sciences (AREA)
• Toxicology (AREA)
• Engineering & Computer Science (AREA)
• Dentistry (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Plant Pathology (AREA)
• Agronomy & Crop Science (AREA)
• Organic Chemistry (AREA)
• Dispersion Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Manufacturing Of Micro-Capsules (AREA)

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Citations (10)

• 1990
  • 1990-09-24 AU AU64207/90A patent/AU641694B2/en not_active Ceased
  • 1990-09-24 EP EP90914385A patent/EP0445266A1/en not_active Withdrawn
  • 1990-09-24 HU HU911930A patent/HUT56998A/hu unknown
  • 1990-09-24 KR KR1019910700533A patent/KR920700535A/ko not_active Application Discontinuation
  • 1990-09-24 BR BR909006932A patent/BR9006932A/pt unknown
  • 1990-09-24 CA CA002040418A patent/CA2040418A1/en not_active Abandoned
  • 1990-09-24 JP JP2513127A patent/JPH04502016A/ja active Pending
  • 1990-09-24 WO PCT/EP1990/001618 patent/WO1991004661A2/en not_active Application Discontinuation
  • 1990-09-26 PT PT95429A patent/PT95429A/pt not_active Application Discontinuation
  • 1990-09-26 MY MYPI90001660A patent/MY106614A/en unknown
  • 1990-09-26 IL IL95801A patent/IL95801A0/xx unknown
  • 1990-09-27 PL PL28707590A patent/PL287075A1/xx unknown
  • 1990-09-27 CN CN90108132A patent/CN1050483A/zh active Pending
  • 1990-09-27 IE IE347090A patent/IE903470A1/en unknown
  • 1990-09-27 YU YU182890A patent/YU182890A/sh unknown
  • 1990-09-28 ZA ZA907807A patent/ZA907807B/xx unknown

Patent Citations (10)

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