Classifications

• • 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

Definitions

• This invention relates to a simplified process for preparing controlled release granules of pesticides.
• Controlled release pesticides in granular formulations have been well known in the art for quite some time.
• U.K. Patent Application No. 2,007,095-A discloses a process for making slow release biologically active granules by mixing an active with a polyisocyanate and one or more compounds having an active hydrogen atom and then granulating.
• the granulation operation requires specialized equipment such as a fluidized bed or spray dryer.
• U.S. 4,223,070 discloses a process for making slow release granules involving overcoating inert porous granules with a solution of active and an organic polyisocyanate followed by applying an aqueous solution of polymerization catalyst as an additional step.
• Japanese Patent Application No. 58-82303 Korean Patent Application No. 58-82303 (Kokai No.
• 59-206302 discloses a process involving coating an active component on a granular carrier with a hydroxyl-containing organic compound or water, a "non-ionic surfactant" of the formula RO(CH 2 CH 2 0) n CONHX where R is C ⁇ alkyl, n is 1-120, and X is a di- or polyisocyanate residue, and a polyisocyanate.
• This invention relates to a process for preparing controlled release granules of pesticides for direct application consisting essentially of overcoating a granular carrier containing a pesticide and a polyhydroxylated compound or water with a liquid polyisocyanate and a polymerization catalyst, optionally at elevated temperatures, resulting in interfacial polymerization to a solid cross-linked polyurethane or polyurea barrier.
• pesticide refers to water-soluble or water-insoluble chemicals commonly known as herbicides, fungicides, insecticides, nematocides, acaricides, miticides, virucides, algicides, bactericides, plant growth regulants, and their agriculturally suitable salts. Preferred are those pesticides which lend themselves to direct soil application. More preferred are herbicides selected from the classes of herbicideal sulfonylureas, imidazolinones, uracils and dinitroanilines; and insecticides selected from the classes of insecticidal carbamates and phosphonates.
• Granular carrier refers to any inert porous or nonporous solid material, examples of which include sand, aggregated clays such as kaolinite, bentonite and attapulgite, vermiculite and granular salts or organic compounds such as sugars, urea, potassium or calcium carbonate, ammonium nitrate, and other granular fertilizers.
• the term granular carrier also includes water-dispersible granules, examples of which are Glean® 75 DF, Pinnacle® DF and Londax® 60 DF, products of E. I. du Pont de Nemours and Company, Wilmington, DE.
• Preferred granule size is about 150 to 4000 microns with 250 to 2000 microns being more preferred.
• polyhydroxylated compound refers to organic chemicals containing two or more free hydroxyl substituents, examples of which include glycols, glycerin or other polyhydric alcohols or mixtures thereof which are liquids or low-melting solids. Preferred are ethylene glycol or propylene glycol.
• polyisocyanate refers to any aliphatic, alicyclic or aromatic organic compound with two or more isocyanato substituents (-NCO) present, which is either a low-melting solid or is a liquid at ambient temperature and pressure.
• polyisocyanates examples include the following: hexamethylene-1,6-diisocyanate; m-phenylene diisocyanate; p-phenylene diisocyanate; 2,4-toluene diisocyanate; 2,6-toluene diisocyanate;
• 1,5-na ⁇ hthalene diisocyanate 1,5-na ⁇ hthalene diisocyanate; cyclohexane 2,4-diisocyanate; 1-methylcyclohexyl 2,6-diisocyanate; and 2,4,6-triisocyanato toluene; or mixtures thereof that are liquids.
• methylene-linked polyphenyl- isocyanates examples of which include those sold under the trade names "Mondur MRS®” (Mobay Chemical Co.) and “PAPI®” (Dow Chemical Co.); the latter is more preferred.
• Suitable polymerization catalysts are organic tertiary amines and alkyltin carboxylic esters. Preferred catalysts are triethylamine, trimethylamine, triethylenediamine, tri-n-butylamine, N-methyl-morpholine, triethanolamine, dibutyltin dilaurate, dibutyltin diacetate, tributyltin acetate, dibutyltin laurate and dibutyltin maleate. More preferred is dibutyltin dilaurate.
• the process is carried out by adding the polyisocyanate and polymerization catalyst to the granules containing the pesticide and water or polyhydroxylated compound at ambient temperature or above.
• the preferred temperature range is about 23°C to 35°C.
• the amounts of polyisocyanate and polymerization catalyst employed in the reaction are about 1 to 20% and 0-5% by weight, respectively; a more preferred amount of catalyst is 0.05-1%. More than 20% by weight of the polyisocyanate can be added to the granule if it is applied stepwise, e.g., in layers.
• the water or polyhydroxylated material must be present in an amount sufficient to ensure that all of the polyisocyanate has reacted.
• reaction time is not critical, it is preferred that the granules can be easily handled (i.e., are nonaggregating) after about 20-30 minutes; a more preferred length of time is about 20 minutes.
• the granular bases used in the process of this invention can be aggregated minerals, clays and other inorganic substances or organic mixtures prepared by known methods such as granulating, prilling, tableting, extrusion or compacting.
• the granular bases can also be naturally occurring granules such as sands.
• suitable inorganic granular bases include kaolinite, bentonite, attapulgite, vermiculite crushed brick and granular salts.
• suitable organic granular bases include sugars, urea, potassium carbonate and calcium carbonate.
• Other suitable materials include granulated corn cobs.
• the process of this invention is also applicable to commercial water dispersible granules prepared by granulation of powdered premixes of biologically active materials and formulation adjuvants such as binders and dispersants.
• Preferred are inert aggregated mineral granules which are impregnated with active material.
• Preferred granule size is about 150 to 4000 microns with 250 to 2000 microns being more preferred.
• the active material used in the process of this invention can be a mixture of compounds or a single compound, and can be in the form of a solid or liquid.
• the active material can be an integral part of the granule matrix or can be added at any time during the processing as will be apparent to one skilled in the art. It is preferred that the active material be a component of the granular material used or be mixed with or impregnated into the granular matrix prior to overcoating with polymer.
• One advantage of pre-incorporation is that there would be less opportunity for the active material to react with the polyisocyanate in cases where the active material is a compound containing hydroxyl, amino, carboxylic acid or other similarly reactive functional groups.
• Suitable active materials are selected from the group consisting of herbicides, fungicides, insecticides, nematocides, acaricides, miticides, virucides, algicides, bactericides and plant growth regulants, and their agriculturally suitable salts. Preferred are those active materials which lend themselves to direct soil application.
• herbicides selected from the classes of sulfonylureas, imidazolinones, uracils and dinitroanilines; and insecticides selected from the classes of carbamates and phosphonates.
• preferred active materials are the following: methyl 2-t[[[(4,6-dimethoxy-2-pyrimidinyl)- amino]carbonyl]amino]sulfonyljmethyl- benzoate; 5-bromo-3-sec-butyl-6-methyluracil; ⁇ , ⁇ , ⁇ -trifluoro-2,6-dinitro-N,N-dipropyl-p- toluidine; N,N-dimethyl-2-methylcarbamoyloxyimino-2-
• polyhydroxyl compound as used in the context of this invention is meant to include organic compounds containing at least two free hydroxyl (-OH) substituents.
• suitable polyhydroxyl compounds include glycols, glycerin and other polyhydroxylated alcohols or mixtures thereof, or mixtures thereof with water, which are either liquids or solids.
• Preferred polyhydroxyl compounds are ethylene glycol and propylene glycol. Water can be used in place of some or all of the polyhydroxyl compound or mixture or polyhydroxyl compounds. While solid polyhydroxyl compounds are operable in the process of this invention, it is preferred that they be used in liquid form by dissolution in a second, liquid polyhydroxyl compound.
• polyisocyanate as used in the context of this invention is meant to include any organic compound containing at least two isocyanato (-NCO) substituents. When solid polyisocyanates are employed in the process of this invention, it is preferred that they be pre-dissolved in a second, liquid polyisocyanate.
• Preferred polyisocyanates are methylene-linked polyphenylisocyanates, nonlimiting examples of which include those sold under the trade names "Mondur MRS®” (Mobay Chemical Co.) and “PAPI®” (Dow Chemical Co.); the latter is more preferred.
• the polymerization reaction requires no catalyst and can be accelerated solely by heating, it is preferred that the process be completed in under 60 minutes, most preferred under 30 minutes at room temperature.
• the polymerization reaction can be accelerated to provide this result by addition of known catalysts for preparing ureas and urethanes, such as organic tertiary amines or alkyltin carboxylic esters to the polyisocyanate before application to the granular substrate.
• Preferred catalysts are triethylamine, trimethylamine, triethylenediamine, tri-n-butylamine, N-methylmorpholine, triethanolamine, dibutyltin dilaurate, dibutyltin diacetate, tributyltin acetate, dibutyltin laurate and dibutyltin maleate. More preferred is dibutyltin dilaurate.
• the process of this invention is carried out by adding the polyisocyanate and optional polymerization catalyst to the granules containing the active material and water or polyhydroxyl compound at ambient temperature or above. The preferred temperature range is about 23°C to 35°C.
• the amount of polyisocyanate employed in the process is about 1 to 20% by weight based on the amount of granular material. Greater than 20% by weight of polyisocyanate can be added to the granules if it is applied in sequential layers wherein sufficient time is allowed for each layer to polymerize before the next coating is applied.
• a polymerization catalyst is used, the preferred amount is up to about 5% by weight relative to the amount of polyisocyanate; a more preferred amount of catalyst is 0.05 to 1%.
• the catalyst is most advantageously applied in solution with the polyisocyanate or polyhydroxyl material to achieve a uniform polymerization reaction.
• the water or polyhydroxyl compound must be present in an amount sufficient to insure that all of the polyisocyanate has reacted.
• the barrier-forming reaction occurs at the interface between the top layer of the isocyanate phase and the underlying water or hydroxyl material and generally continues until all the isocyanate functionality is consumed.
• the presence of excess water or hydroxyl functionality does not normally affect the barrier since such material can be entrapped under the barrier formed.
• reaction time is not critical, it is preferred that the granules can be easily handled (i.e., are nonaggregating) after about 20 to 30 minutes; a more preferred length of time is about 20 minutes.
• water is the coreactant with the polyisocyanate, some of the isocyanate groups hydrolyze to form amino functionality, followed by self-polycondensation by reaction with the unaffected isocyanate groups. Under these conditions, a polyurea is formed.
• a polyurethane is produced as barrier.
• the polyhydroxyl or polyisocyanate compounds have more than two hydroxyl or isocyanate groups, cross-linked polymeric barrier coatings are formed. If a mixture of water and at least one organic polyhydroxyl compound is used, the polymeric barrier produced is a polyurea-urethane.
• Reduction of the release rate is generally achieved by use of aromatic polyisocyanates instead of alphatic polyisocyanates or by increasing the amount of polymer forming ingredients (which governs the thickness of the shell) .
• Reduction of release rate can also be achieved by increasing the degree of cross-linking by using reactants containing more than two hydroxyl or isocyanate groups to process cross-linking and using no diluents.
• release rates were measured in pH 7 buffered water at room temperature under static conditions. In all cases, sufficient water was used to greatly exceed the quantity needed to dissolve all the active material. The water was agitated just prior to sampling to insure an even concentration of dissolved active.
• EXAMPLE 1 Granules of the insecticide 0,0-diethyl 0-(l,2,2,2-tetrachloroethyl)phosphorothioate (4.08 g) containing 4%. propylene glycol and 10% of the active ingredient were mixed with 1.0 g of a solution of 0.01 g dibutyltin dilaurate in PAPI® 901 (Dow Chemical Co.). After 30 minutes, the granules were free-flowing. The volatility of 0,0-diethyl
• EX MPL 2 Water-dispersible granules containing 60% of methyl 2-[[[[4,6-dimethoxy-2-pyrimidinyl)amino]- carbonyl]amino]sulfonyl]methylbenzoate (9.0 g; Londax® 60 DF; E. I. du Pont de Nemours and Company) were mixed with 0.3 g propylene glycol followed by a solution of 1.0 g PAPI® 901 (Dow Chemical Co.) and 0.01 g dibutyltin dilaurate. After standing in an open beaker for about 30 minutes, the somewhat sticky mixture became free-flowing, indicating that polymerization to polyurethane coating had occurred.
• EXAMPLE 4 Sand (76.4 g, diameter 250 to 840 microns) was mixed with 0.2 g propylene glycol followed by 0.6 g PAPI® 901 containing 0.063 g dibutyltin dilaurate. Then 2.5 g of 2-[[[[4,6-dimethoxy-2-pyrimidinyl)- amino]carbonyl]amino]sulfonyl]methylbenzoate powder was added with stirring to give a mixture containing 3% active ingredient. After curing had occurred, the release rate in excess pH 7 buffered water was found to be 42% in 67 hours and 96% in 499 hours.
• Example 4 Example 4 was repeated except for the substitution of propylene glycol by 0.16 g water. Release rates for the polyurea coating were 63% in 305 hours and 100% in 665 hours.

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• Life Sciences & Earth Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Pest Control & Pesticides (AREA)
• Plant Pathology (AREA)
• Agronomy & Crop Science (AREA)
• Engineering & Computer Science (AREA)
• Dentistry (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Environmental Sciences (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Medicinal Preparation (AREA)

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Cited By (6)

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Citations (2)

• 1991
  • 1991-01-08 WO PCT/US1991/000015 patent/WO1991010362A1/en not_active Application Discontinuation
  • 1991-01-08 AU AU71750/91A patent/AU7175091A/en not_active Abandoned
  • 1991-01-08 CA CA002073689A patent/CA2073689A1/en not_active Abandoned
  • 1991-01-08 JP JP3502957A patent/JPH05503697A/ja active Pending
  • 1991-01-08 EP EP91901981A patent/EP0513027A1/en not_active Ceased
  • 1991-01-08 KR KR1019920701646A patent/KR927002910A/ko not_active Application Discontinuation
  • 1991-01-10 NZ NZ236736A patent/NZ236736A/en unknown
  • 1991-01-10 IL IL96916A patent/IL96916A0/xx unknown
  • 1991-01-11 PT PT96469A patent/PT96469A/pt not_active Application Discontinuation
  • 1991-01-11 CS CS9158A patent/CS5891A3/cs unknown
  • 1991-01-11 ZA ZA91237A patent/ZA91237B/xx unknown

Patent Citations (2)

Non-Patent Citations (3)

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