CA2073689A1 - Process for preparing controlled release granules - Google Patents
Process for preparing controlled release granulesInfo
- Publication number
- CA2073689A1 CA2073689A1 CA002073689A CA2073689A CA2073689A1 CA 2073689 A1 CA2073689 A1 CA 2073689A1 CA 002073689 A CA002073689 A CA 002073689A CA 2073689 A CA2073689 A CA 2073689A CA 2073689 A1 CA2073689 A1 CA 2073689A1
- Authority
- CA
- Canada
- Prior art keywords
- polyisocyanate
- water
- pesticide
- granules
- polymerization catalyst
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
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
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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)
Abstract
Process for preparing controlled release granules of pesticides for direct application consisting essentially of overcoating a granular carrier containing a pesticide and a di- or 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.
Description
W~91/10362 PCT/US91/00015 2~73689 ~ITh~
PROCESS FOR PREPARING CONTEIOLLED RELEASE GRANULES
BACKGROUND OF T~IE INVENTION
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 mi~ing 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. S8-82303 (Kokai No. 59-206302) discloses a process involving coating an active component on a granular carrier with a hydro~yl-containing organic compound or water, a ~non-ionic surfactant" of the formula 30 RO(CH2CH2O)nCONHX where R is Cl-C4 alkyl, n is 1-120, and X is a di- or polyisocyanate residue, and a polyisocyanate.
A need still e2ists, however, for improved controlled release granules prepared by a simple process in conventional mi2iny equipment.
,. . .
' ',.' ~ ~
' ' ' w091/10~2 PCT/US91/00015 According to the instant invention, an improved process for preparing controlled release granules has been found which is much more versatile and convenient than the processes mentioned above. No adjuvants or solvents are required in the process of this invention~ Treatment with aqueous catalyst solution as taught in U.S. 4,223,070 is not required, and such treatment could lead to non-uniform polymeric coatings because of non-uniform wetting.
The process of the present invention can be applied to porous or nonporous granules whereas the process of U.S. 4,223,070 is applicable only to the former.
Also, the process of U.S. 4,223,070 requires that the active component be dissolved in the polyisocyanate whereas the process of this invention does not have this requirement. Many pesticides do not dissolve in polyisocyanates and in some cases, the biologically active material can be destroyed by reaction with the polyisocyanate.
SUMMARY OF THE INVENTION
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 polyhydro~ylated 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.
The term 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 he~bicideal sulfonylureas, imidazolinones, uracils and dinitroanilines; and insecticides selected from the classes of insecticidal carbamates and phosphonates.
Specifically preferred are the following:
methyl 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)-amino]carbonyl]amino]suIfonyl]methyl-benzoate tbensulfuron);
5-bromo-3-sec-butyl-6-methyluracil (bromacil);
~,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin);
N,N-dimethyl-2-methylcarbamoyloxyimino-2-(methylthio)acetamide (o~amyl);
S-tert-butylthiomethyl O,O-diethylphosphoro-dithioate ~terbufos); and O,O-diethyl 0-(l,2,2,2-tetrachloroethyl)-phosphorothioate.
Granular carrier refers to any inert porous or nonporous solid material, e~amples 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, e~amples of which are Glean~ 75 DF, Pinnacle~ DF and Londa~ 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.
.. , , , ' ' , , ~ .
' ' ' -; ' : ' W O 91/10362 P ~ /US91/00015 The term polyhydro~ylated compound refers to organic chemicals containing two or more free hydro~yl substituents, e~amples of which include glycols, glycerin or other polyhydric alcohols or mi~tures thereof which are liquids or low-melting solids. Preferred are ethylene glycol or propylene glycol.
The term polyisocyanate refers to any aliphatic, alicyclic or aro~atic 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. Examples of suitable polyisocyanates include the following:
he~amethylene-1,6-diisocyanate;
m-phenylene diisocyanate;-p-phenylene diisocyanate;
2,4-toluene diisocyanate;
2,6-toluene diisocyanate;
1,5-naphthalene diisocyanate;
cyclohexane 2,4-diisocyanate;
l-methylcyclohexyl 2,6-diisocyanate; and 2,4,6-triisocyanato toluene;
- 25 or mi~tures thereof that are liquids.
Preferred are methylene-linked polyphenyl-isocyanates, e~amples 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 carbo~ylic esters.
Preferred catalysts are triethylamine, trimethylamine, triethylenediamine, tri-n-butylamine, N-metAyl-morpholine, triethanolamine, dibutyltin dilaurate, dibutyltin diacetate, tributyltin acetate, WO91/10362 PC~/USgl/0001;
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 polyhydro~ylated compound at ambient temperature or above. The preferred temperature range is about 23C
to 35C. 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 polyhydro~ylated material must be present in an amount sufficient to ensure that all of the polyisocyanate has reacted. Although 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.
DETAILE~_UESCRIPTION OF THE INVENTION
The granular bases used in the process of this invention can be aggregated minerals, clays and other inorganic substances or organic mi~tures prepared by known methods such as granulating, prilling, tableting, e2trusion or compacting. The granular bases can also be naturally occurring granules such as sands. E~amples of suitable inorganic granular bases include kaolinite, bentonite, attapulgite, vermiculite crushed brick and granular salts.
Nonlimiting e~amples of suitable organic granular bases include sugars, urea, potassium carbonate and calcium carbonate. Other suitable materials include granulated corn cobs. The process of this invention WO91/10362 PCT/US91/0001~
is also applicable to commercial water dispersible granules prepared by granulation of powdered premi~es of biol~gically active materials and formulation adjuvants such as binders and dispersants. Preferred are inert a~gregated mineral granules which are impregnated with active material. Preferred granule size is about lS0 to 4000 microns with 250 to 2000 microns being more preferred.
The active material used in the process of this invention can be a mi~ture 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 granuie matri~ 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 mi~ed with or impregnated into the granular matri~ 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 hydro~yl, amino, carbo~ylic acid or other similarly reactive functional groups. Also, by integrating the active material present in or placing it on the granular base before the polymer barrier is formed, superior barrier characteristics are attainable with relatively small amounts of polymer. In this manner, the polymer barrier is not diluted or weakened by the presence of a non-polymeric material. However, when desired, non-volatile organic material or the active material can sometimes be advantageously added to the polyisocyanate for adjustment of release rate.
WO 91/10362 PCI/US91/0001~
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. More preferred are herbicides selected from the classes of sulfonylureas, imidazolinones, uracils and dinitroanilines; and insecticides selected from the classes of carbamates and phosphonates. Specific examples of preferred active materials are the following:
methyl 2-[t[[(4,6-dimethoxy-2-pyrimidinyl)-amino]carbonyl]amino]sulfonyl]methyl-benzoate, 5-bromo-3-sec-butyl-6-methyluracil;
a,~,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine;
N,N-dimethyl-2-methylcarbamoylosyimino-2-(methylthio)acetamide;
S-tert-butylthiomethyl O,O-diethylphosphoro-dithioate; and O,O-diethyl 0-(1,2,2,2-tetrachloroethyl)-phosphorothioate. -.
The term ~polyhydro~yl compound" as used in the contest of this invention is meant to include organic compounds containing at least two free hydroxyl (-OH) substituents. Esamples of suitable polyhydroxyl compounds include glycols, glycerin and other polyhydrosylated alcohols or mi~tures thereof, or mistures thereof with water, which are either liquids or solids. Preferred polyhydrosyl compounds are ethylene glycol and propylene glycol. Water can be WO91/10362 PCT/US91/0001~
2~73689 8 used in place of some or all of the polyhydro~yl compound or mi~ture or polyhydro~yl compounds. While solid polyhydro~yl 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 polyhydro~yl compound.
The term "polyisocyanate" as used in the context of this invention is meant to include any organic co~pound 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~n ~Mobay Chemical Co.) and "PAPI~" (Dow Chemical - 20 Co.); the latter is more preferred.
While 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 carbo~ylic 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, 3~ dibutyltin laurate and dibutyltin maleate. More preferred is dibutyltin dilaurate.
9 ~073689 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 polyhydro~yl compound at ambient temperature or above. The prefer{ed temperature range is about 23C to 35C. 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 ne~t coating is applied. When 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 polyhydro~yl 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 e~cess water or hydroxyl functionality does not normally affect the barrier since such material can be entrapped under the barrier formed. Although reaction time is not critical, it is preferred that the granules can be easily handled (i.e., are nonaggregating) after about 3~ 20 to 30 minutes; a more preferred length of time is about 20 minutes.
,~, WO 91/103~i2 PCr/US~l~OnO15 ` 2~73689 lo Where 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. Where a polyhydro~yl compound is used, a polyurethane is produced as barrier. When the polyhydro2yl or polyisocyanate compounds have more than two hydroxyl or isocyanate groups, cross-linked polymeric barrier coatings are formed.
If a mi~ture of water and at least one organic polyhydroxyl compound is used, the polymeric barrier lS 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 hydro~yl or isocyanate groups to process cross-linking and using no diluents.
In the E~amples below, which are further illustrative of the process of this invention, release rates were measured in pH 7 buffered water at - room temperature under static conditions. In all cases, sufficient water was used to greatly e~ceed 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. The concentration of active was measured by HPLC. Percentages are meant to be weight percentages unless otherwise indicated.
W091/10362 PCT/US91/0001~
~XA~PLE 1 Granules of the insecticide O,O-diethyl 0-(1,2,2,2-tetrachloroethyl)phosphorothioate (4.08 g) containing 4% propylene glycol and 10% of the active ingredient were mi~ed with 1.0 9 of a solution of 0.01 9 dibutyltin dilaurate in PAPI~ 901 (Dow Chemical Co.). After 30 minutes, the granules were free-flowing. The volatility of O,O-diethyl 0-(1,2,2,2-tetrachloroethyl)phosphorothioate in these coated granules was compared with unmodified granules at 45C-60C in an air oven. After 44 hours, the overcoated granules lost 0.12 g active ingredient while the uncoated sample lost 0.27 g thereby showing that the polymeric coating retarded volatilization of the active ingredient.
Water-dispersible granules containing 60~ of methyl 2-t[~4,6-dimetho~y-2-pyrimidinyl)amino]-carbonyl]amino]sulfonyl]methylbenzoate (9.0 g;
Londa~ 60 DF; E. I. du Pont de Nemours and Company) were mi~ed 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.
The granules were added to 500 mL water and were allowed to stand 3 days. The granules maintained their integrity while slowly releasing some of the active ingredient: 12% in 21 hours, 31% in 46 hours, and 100% in 300 hours. The uncoated granules completely disintegrated in e~cess water in about 2 minutes and released 100% of the active in under 2 hours.
,, WO91/10~2 PCT/US91/00015 2o'73689 E~eLE 3 Flore~ LVM 8-16 mesh attapulgite granules (Flore~ LVM) (Floridin Co.) were preimpregnated with polymer, to reduce porosity, by mi~ing 120 9 of the material with 5 9 propylene glycol followed by 10 9 of PAPI~ 901 containing 0.5% dibutyltin dilaurate.
After allowing 1 hour for curing to a crosslinked polyurethane containing, 16.6 g of the precoated granules were mixed with 0.627 g technical 2-[[[[9,6-dimetho~y-2-pyrimidinyl)amino]carbonyl~-amino]sulfonyl]methylbenzoate (95.7%), 0.39 g propylene glycol followed by 0.8 g PAPI~ 901 (Dow Chemical Co.) containing 0.02 9 dibutyltin dilaurate. The sample was allowed to cure in an open vessel giving a product having 3% active ingredient with crosslinked polyurethane urea overcoat. The release rate in excess pH 7 buffered water was 15% in 162 hours and 24% in 451 hours.
EXA~LE 4 Sand (76.4 g, diameter 250 to 840 microns) was mixed with 0.2 g propylene glycol followed by 0.6 9 PAPI~ 9Dl containing 0.063 9 dibutyltin dilaurate.
Then 2.5 9 of 2-[tt[4~6-dimethoxy-2-pyrimidinyl)-amino]carbonyl]amino]sulfonyl]methylbenzoate powder was added with stirring to give a mi~ture 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.
E~ample 4 was repeated, e~cept that the PAPI~
901 solution was added last, giving granules that released somewhat slower, 35% in 114 hours and 74% in 525 hours.
W091/l0362 PCT/US91/00015 ~,~
Example 4 was repeated e cept 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.
Sand (17.3 9), 0.627 g 2-[[[[9,6-dimetho~y-2-pyrimidinyl)amino]carbonyl~amino]sulfonyl]methyl-benzoate and 0.46 propylene glycol were mi~ed and 2.02 9 technical toluene diisocyanate (80% 2,9-isomer and 20% 2,6-isomer) containing 0.039 9 dibutyltin dilaurate was added. The cured product contained 2.9% active ingredient. The release rates were 10%
in 162 hours and 16% in 451 hours. Similar results were obtained when 2.0 g of a solution of 50%
technical toluene-2,4-diisocyanate and PAPI~ 901 was - used instead of technical toluene-2,4-diisocyanate alone.
Krovar~ I (9.0 g) water-dispersible granules (E. I. du Pont de Nemours ~ Co.), containing 40%
bromacil and 40% diuron, was treated successively 25 with 0.2 g propylene glycol and 0.51 g PAPI~ 901 containing 0.4% dibutyltin dilaurate. The release rate of the bromacil in the granules in e~cess water was 76% in 21 hours and 83% in 46 hours. The granules maintained their integrity over one month in excess water while continuing to release bromacil.
The uncoated control granules disintegrated and released all of their bromacil in less than one hour.
.
~ ' ,
PROCESS FOR PREPARING CONTEIOLLED RELEASE GRANULES
BACKGROUND OF T~IE INVENTION
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 mi~ing 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. S8-82303 (Kokai No. 59-206302) discloses a process involving coating an active component on a granular carrier with a hydro~yl-containing organic compound or water, a ~non-ionic surfactant" of the formula 30 RO(CH2CH2O)nCONHX where R is Cl-C4 alkyl, n is 1-120, and X is a di- or polyisocyanate residue, and a polyisocyanate.
A need still e2ists, however, for improved controlled release granules prepared by a simple process in conventional mi2iny equipment.
,. . .
' ',.' ~ ~
' ' ' w091/10~2 PCT/US91/00015 According to the instant invention, an improved process for preparing controlled release granules has been found which is much more versatile and convenient than the processes mentioned above. No adjuvants or solvents are required in the process of this invention~ Treatment with aqueous catalyst solution as taught in U.S. 4,223,070 is not required, and such treatment could lead to non-uniform polymeric coatings because of non-uniform wetting.
The process of the present invention can be applied to porous or nonporous granules whereas the process of U.S. 4,223,070 is applicable only to the former.
Also, the process of U.S. 4,223,070 requires that the active component be dissolved in the polyisocyanate whereas the process of this invention does not have this requirement. Many pesticides do not dissolve in polyisocyanates and in some cases, the biologically active material can be destroyed by reaction with the polyisocyanate.
SUMMARY OF THE INVENTION
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 polyhydro~ylated 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.
The term 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 he~bicideal sulfonylureas, imidazolinones, uracils and dinitroanilines; and insecticides selected from the classes of insecticidal carbamates and phosphonates.
Specifically preferred are the following:
methyl 2-[[[[(4,6-dimethoxy-2-pyrimidinyl)-amino]carbonyl]amino]suIfonyl]methyl-benzoate tbensulfuron);
5-bromo-3-sec-butyl-6-methyluracil (bromacil);
~,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin);
N,N-dimethyl-2-methylcarbamoyloxyimino-2-(methylthio)acetamide (o~amyl);
S-tert-butylthiomethyl O,O-diethylphosphoro-dithioate ~terbufos); and O,O-diethyl 0-(l,2,2,2-tetrachloroethyl)-phosphorothioate.
Granular carrier refers to any inert porous or nonporous solid material, e~amples 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, e~amples of which are Glean~ 75 DF, Pinnacle~ DF and Londa~ 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.
.. , , , ' ' , , ~ .
' ' ' -; ' : ' W O 91/10362 P ~ /US91/00015 The term polyhydro~ylated compound refers to organic chemicals containing two or more free hydro~yl substituents, e~amples of which include glycols, glycerin or other polyhydric alcohols or mi~tures thereof which are liquids or low-melting solids. Preferred are ethylene glycol or propylene glycol.
The term polyisocyanate refers to any aliphatic, alicyclic or aro~atic 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. Examples of suitable polyisocyanates include the following:
he~amethylene-1,6-diisocyanate;
m-phenylene diisocyanate;-p-phenylene diisocyanate;
2,4-toluene diisocyanate;
2,6-toluene diisocyanate;
1,5-naphthalene diisocyanate;
cyclohexane 2,4-diisocyanate;
l-methylcyclohexyl 2,6-diisocyanate; and 2,4,6-triisocyanato toluene;
- 25 or mi~tures thereof that are liquids.
Preferred are methylene-linked polyphenyl-isocyanates, e~amples 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 carbo~ylic esters.
Preferred catalysts are triethylamine, trimethylamine, triethylenediamine, tri-n-butylamine, N-metAyl-morpholine, triethanolamine, dibutyltin dilaurate, dibutyltin diacetate, tributyltin acetate, WO91/10362 PC~/USgl/0001;
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 polyhydro~ylated compound at ambient temperature or above. The preferred temperature range is about 23C
to 35C. 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 polyhydro~ylated material must be present in an amount sufficient to ensure that all of the polyisocyanate has reacted. Although 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.
DETAILE~_UESCRIPTION OF THE INVENTION
The granular bases used in the process of this invention can be aggregated minerals, clays and other inorganic substances or organic mi~tures prepared by known methods such as granulating, prilling, tableting, e2trusion or compacting. The granular bases can also be naturally occurring granules such as sands. E~amples of suitable inorganic granular bases include kaolinite, bentonite, attapulgite, vermiculite crushed brick and granular salts.
Nonlimiting e~amples of suitable organic granular bases include sugars, urea, potassium carbonate and calcium carbonate. Other suitable materials include granulated corn cobs. The process of this invention WO91/10362 PCT/US91/0001~
is also applicable to commercial water dispersible granules prepared by granulation of powdered premi~es of biol~gically active materials and formulation adjuvants such as binders and dispersants. Preferred are inert a~gregated mineral granules which are impregnated with active material. Preferred granule size is about lS0 to 4000 microns with 250 to 2000 microns being more preferred.
The active material used in the process of this invention can be a mi~ture 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 granuie matri~ 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 mi~ed with or impregnated into the granular matri~ 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 hydro~yl, amino, carbo~ylic acid or other similarly reactive functional groups. Also, by integrating the active material present in or placing it on the granular base before the polymer barrier is formed, superior barrier characteristics are attainable with relatively small amounts of polymer. In this manner, the polymer barrier is not diluted or weakened by the presence of a non-polymeric material. However, when desired, non-volatile organic material or the active material can sometimes be advantageously added to the polyisocyanate for adjustment of release rate.
WO 91/10362 PCI/US91/0001~
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. More preferred are herbicides selected from the classes of sulfonylureas, imidazolinones, uracils and dinitroanilines; and insecticides selected from the classes of carbamates and phosphonates. Specific examples of preferred active materials are the following:
methyl 2-[t[[(4,6-dimethoxy-2-pyrimidinyl)-amino]carbonyl]amino]sulfonyl]methyl-benzoate, 5-bromo-3-sec-butyl-6-methyluracil;
a,~,-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine;
N,N-dimethyl-2-methylcarbamoylosyimino-2-(methylthio)acetamide;
S-tert-butylthiomethyl O,O-diethylphosphoro-dithioate; and O,O-diethyl 0-(1,2,2,2-tetrachloroethyl)-phosphorothioate. -.
The term ~polyhydro~yl compound" as used in the contest of this invention is meant to include organic compounds containing at least two free hydroxyl (-OH) substituents. Esamples of suitable polyhydroxyl compounds include glycols, glycerin and other polyhydrosylated alcohols or mi~tures thereof, or mistures thereof with water, which are either liquids or solids. Preferred polyhydrosyl compounds are ethylene glycol and propylene glycol. Water can be WO91/10362 PCT/US91/0001~
2~73689 8 used in place of some or all of the polyhydro~yl compound or mi~ture or polyhydro~yl compounds. While solid polyhydro~yl 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 polyhydro~yl compound.
The term "polyisocyanate" as used in the context of this invention is meant to include any organic co~pound 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~n ~Mobay Chemical Co.) and "PAPI~" (Dow Chemical - 20 Co.); the latter is more preferred.
While 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 carbo~ylic 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, 3~ dibutyltin laurate and dibutyltin maleate. More preferred is dibutyltin dilaurate.
9 ~073689 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 polyhydro~yl compound at ambient temperature or above. The prefer{ed temperature range is about 23C to 35C. 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 ne~t coating is applied. When 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 polyhydro~yl 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 e~cess water or hydroxyl functionality does not normally affect the barrier since such material can be entrapped under the barrier formed. Although reaction time is not critical, it is preferred that the granules can be easily handled (i.e., are nonaggregating) after about 3~ 20 to 30 minutes; a more preferred length of time is about 20 minutes.
,~, WO 91/103~i2 PCr/US~l~OnO15 ` 2~73689 lo Where 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. Where a polyhydro~yl compound is used, a polyurethane is produced as barrier. When the polyhydro2yl or polyisocyanate compounds have more than two hydroxyl or isocyanate groups, cross-linked polymeric barrier coatings are formed.
If a mi~ture of water and at least one organic polyhydroxyl compound is used, the polymeric barrier lS 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 hydro~yl or isocyanate groups to process cross-linking and using no diluents.
In the E~amples below, which are further illustrative of the process of this invention, release rates were measured in pH 7 buffered water at - room temperature under static conditions. In all cases, sufficient water was used to greatly e~ceed 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. The concentration of active was measured by HPLC. Percentages are meant to be weight percentages unless otherwise indicated.
W091/10362 PCT/US91/0001~
~XA~PLE 1 Granules of the insecticide O,O-diethyl 0-(1,2,2,2-tetrachloroethyl)phosphorothioate (4.08 g) containing 4% propylene glycol and 10% of the active ingredient were mi~ed with 1.0 9 of a solution of 0.01 9 dibutyltin dilaurate in PAPI~ 901 (Dow Chemical Co.). After 30 minutes, the granules were free-flowing. The volatility of O,O-diethyl 0-(1,2,2,2-tetrachloroethyl)phosphorothioate in these coated granules was compared with unmodified granules at 45C-60C in an air oven. After 44 hours, the overcoated granules lost 0.12 g active ingredient while the uncoated sample lost 0.27 g thereby showing that the polymeric coating retarded volatilization of the active ingredient.
Water-dispersible granules containing 60~ of methyl 2-t[~4,6-dimetho~y-2-pyrimidinyl)amino]-carbonyl]amino]sulfonyl]methylbenzoate (9.0 g;
Londa~ 60 DF; E. I. du Pont de Nemours and Company) were mi~ed 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.
The granules were added to 500 mL water and were allowed to stand 3 days. The granules maintained their integrity while slowly releasing some of the active ingredient: 12% in 21 hours, 31% in 46 hours, and 100% in 300 hours. The uncoated granules completely disintegrated in e~cess water in about 2 minutes and released 100% of the active in under 2 hours.
,, WO91/10~2 PCT/US91/00015 2o'73689 E~eLE 3 Flore~ LVM 8-16 mesh attapulgite granules (Flore~ LVM) (Floridin Co.) were preimpregnated with polymer, to reduce porosity, by mi~ing 120 9 of the material with 5 9 propylene glycol followed by 10 9 of PAPI~ 901 containing 0.5% dibutyltin dilaurate.
After allowing 1 hour for curing to a crosslinked polyurethane containing, 16.6 g of the precoated granules were mixed with 0.627 g technical 2-[[[[9,6-dimetho~y-2-pyrimidinyl)amino]carbonyl~-amino]sulfonyl]methylbenzoate (95.7%), 0.39 g propylene glycol followed by 0.8 g PAPI~ 901 (Dow Chemical Co.) containing 0.02 9 dibutyltin dilaurate. The sample was allowed to cure in an open vessel giving a product having 3% active ingredient with crosslinked polyurethane urea overcoat. The release rate in excess pH 7 buffered water was 15% in 162 hours and 24% in 451 hours.
EXA~LE 4 Sand (76.4 g, diameter 250 to 840 microns) was mixed with 0.2 g propylene glycol followed by 0.6 9 PAPI~ 9Dl containing 0.063 9 dibutyltin dilaurate.
Then 2.5 9 of 2-[tt[4~6-dimethoxy-2-pyrimidinyl)-amino]carbonyl]amino]sulfonyl]methylbenzoate powder was added with stirring to give a mi~ture 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.
E~ample 4 was repeated, e~cept that the PAPI~
901 solution was added last, giving granules that released somewhat slower, 35% in 114 hours and 74% in 525 hours.
W091/l0362 PCT/US91/00015 ~,~
Example 4 was repeated e cept 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.
Sand (17.3 9), 0.627 g 2-[[[[9,6-dimetho~y-2-pyrimidinyl)amino]carbonyl~amino]sulfonyl]methyl-benzoate and 0.46 propylene glycol were mi~ed and 2.02 9 technical toluene diisocyanate (80% 2,9-isomer and 20% 2,6-isomer) containing 0.039 9 dibutyltin dilaurate was added. The cured product contained 2.9% active ingredient. The release rates were 10%
in 162 hours and 16% in 451 hours. Similar results were obtained when 2.0 g of a solution of 50%
technical toluene-2,4-diisocyanate and PAPI~ 901 was - used instead of technical toluene-2,4-diisocyanate alone.
Krovar~ I (9.0 g) water-dispersible granules (E. I. du Pont de Nemours ~ Co.), containing 40%
bromacil and 40% diuron, was treated successively 25 with 0.2 g propylene glycol and 0.51 g PAPI~ 901 containing 0.4% dibutyltin dilaurate. The release rate of the bromacil in the granules in e~cess water was 76% in 21 hours and 83% in 46 hours. The granules maintained their integrity over one month in excess water while continuing to release bromacil.
The uncoated control granules disintegrated and released all of their bromacil in less than one hour.
.
~ ' ,
Claims (22)
1. 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, mixtures of polyhydroxylated compounds, or mixtures of water and at least one polyhydroxylated compound or water alone with a liquid polyisocyanate or mixture of polyisocyanates and, optionally, a polymerization catalyst, resulting in an interfacial polymerization reaction to a solid cross-linked polyurethane or polyurea barrier.
2. The process of Claim 1 which takes place at elevated temperature.
3. The process of Claim 1 wherein the pesticide is a herbicide or insecticide.
4. The process of Claim 3 wherein the herbicide is selected from sulfonylureas, imidazolinones, uracils, dinitroanilines and the insecticide is a phosphorothioate.
5. The process of Claim 1 wherein the granular carrier is selected from sand or aggragated clays.
6. The process of Claim 5 wherein the granular carrier size is about 150 to 4,000 microns.
7. The process of Claim 1 wherein said polyhydroxylated compound is selected from ethylene glycol or propylene glycol.
8. The process of Claim 1 wherein the polyisocyanate is a methylene-linked polyphenylisocyanate.
9. The process of Claim 1 wherein the polyisocyanate is a toluene diisocyanate.
10. The process of Claim 1 wherein the polyisocyanate is a mixture of methylene-linked polyphenylisocyanate and a toluene-2,4-diisocyanate.
11. The process of Claim 1 wherein the polymerization catalyst is selected from organic tertiary amines and alkyltin carboxylic esters.
12. A process for preparing controlled release granules of pesticides for direct application consisting essentially of adding a polyisocyanate or polyisocyanate mixture and a polymerization catalyst to granules containing a pesticide and water or polyhydroxylated compounds or mixtures thereof at at least about ambient temperature wherein the amount of polyisocyanate and polymerization catalyst employed are about 1 to 20% and 0 to 5% by weight, respectively, resulting in an interfacial polymerization reaction to a solid cross-linked polyurethane or polyurea barrier whereby the amount of said water or polyhydroxylated material is present in an amount to insure that all of the polyisocyanate has reacted.
13. The process of Claim 10 wherein the reaction time is about 20 to 30 minutes.
14. The process of Claim 10 wherein the pesticide is a herbicide.
15. The process of Claim 12 wherein the herbicide is selected from sulfonylureas, imidazolinones, uracils or dinitroanilines.
16. The process of Claim 10 wherein the pesticide is an insecticide.
17. The process of Claim 10 wherein the insecticide is a phosphorothioate.
18. The process of Claim 10 wherein the granular carrier is selected from sand or aggregated clays.
19. The process of Claim 14 wherein the granular carrier size is about 150 to 4,000 microns.
20. The process of Claim 10 wherein said polyhydroxylated compound is selected from ethylene glycol or propylene glycol.
21. The process of Claim 10 wherein the polyisocyanate is a methylene-linked polyphenyl-isocyanate, or a toluene diisocyanate or mixtures thereof.
22. The process of Claim 10 wherein the polymerization catalyst is selected from organic tertiary amines and alkyltin carboxylic esters.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US46443490A | 1990-01-12 | 1990-01-12 | |
| US07/464,434 | 1990-01-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2073689A1 true CA2073689A1 (en) | 1991-07-13 |
Family
ID=23843943
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002073689A Abandoned CA2073689A1 (en) | 1990-01-12 | 1991-01-08 | Process for preparing controlled release granules |
Country Status (11)
| Country | Link |
|---|---|
| EP (1) | EP0513027A1 (en) |
| JP (1) | JPH05503697A (en) |
| KR (1) | KR927002910A (en) |
| AU (1) | AU7175091A (en) |
| CA (1) | CA2073689A1 (en) |
| CS (1) | CS5891A3 (en) |
| IL (1) | IL96916A0 (en) |
| NZ (1) | NZ236736A (en) |
| PT (1) | PT96469A (en) |
| WO (1) | WO1991010362A1 (en) |
| ZA (1) | ZA91237B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5560768A (en) * | 1993-05-06 | 1996-10-01 | Haifa Chemicals South Ltd. | Method for preparing an encapsulated slow-release particulate fertilizer |
| JP3761649B2 (en) * | 1996-12-11 | 2006-03-29 | 住友化学株式会社 | Method for producing granular agrochemical composition |
| US5851261A (en) * | 1996-12-30 | 1998-12-22 | Bayer Corporation | Process for the production of polyurea encapsulated fertilizer particles and the encapsulated fertilizer particles produced by this process |
| AU756668B2 (en) * | 1997-12-24 | 2003-01-23 | Kiwitech Limited | Substantially water-insoluble matrix containing bioactive substances for slow release |
| JP4655606B2 (en) * | 2003-12-04 | 2011-03-23 | 住友化学株式会社 | Agrochemical granules |
| EP1864573B1 (en) | 2005-03-28 | 2016-06-01 | Sumitomo Chemical Company, Limited | Agricultural-chemical composition |
| US10556841B2 (en) | 2014-04-28 | 2020-02-11 | Basf Se | Method of forming an encapsulated fertilizer |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4223070A (en) * | 1978-05-04 | 1980-09-16 | Stauffer Chemical Company | Impregnated porous granules with slow release pore membranes and process therefor |
| DE2743485C3 (en) * | 1977-09-28 | 1980-09-04 | Hoechst Ag, 6000 Frankfurt | Process for the production of biologically effective granulates |
-
1991
- 1991-01-08 KR KR1019920701646A patent/KR927002910A/en not_active Application Discontinuation
- 1991-01-08 CA CA002073689A patent/CA2073689A1/en not_active Abandoned
- 1991-01-08 AU AU71750/91A patent/AU7175091A/en not_active Abandoned
- 1991-01-08 EP EP91901981A patent/EP0513027A1/en not_active Ceased
- 1991-01-08 WO PCT/US1991/000015 patent/WO1991010362A1/en not_active Application Discontinuation
- 1991-01-08 JP JP3502957A patent/JPH05503697A/en active Pending
- 1991-01-10 NZ NZ236736A patent/NZ236736A/en unknown
- 1991-01-10 IL IL96916A patent/IL96916A0/en unknown
- 1991-01-11 CS CS9158A patent/CS5891A3/en unknown
- 1991-01-11 PT PT96469A patent/PT96469A/en not_active Application Discontinuation
- 1991-01-11 ZA ZA91237A patent/ZA91237B/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05503697A (en) | 1993-06-17 |
| CS5891A3 (en) | 1992-06-17 |
| IL96916A0 (en) | 1992-03-29 |
| PT96469A (en) | 1991-10-15 |
| NZ236736A (en) | 1993-03-26 |
| KR927002910A (en) | 1992-12-17 |
| WO1991010362A1 (en) | 1991-07-25 |
| EP0513027A1 (en) | 1992-11-19 |
| AU7175091A (en) | 1991-08-05 |
| ZA91237B (en) | 1992-09-30 |
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| FZDE | Discontinued |