PT96469A - PROCESS FOR THE PREPARATION OF CONTROLLED LIBERATION GRANULES - Google Patents

Description

PROCESS FOR THE PREPARATION OF CONTROLLED RELEASE GRANULES " PROCESS FOR THE PREPARATION OF CONTROLLED RELEASE BEADS " The present invention relates to a simplified process for the preparation of pesticide release granules.

Release pesticides in the form of granular compositions are known for some time.

GB 2 007 095-A discloses a process for the preparation of controlled release biologically active granules by mixing an active ingredient with a polyisocyanate and one or more compounds having a active hydrogen, followed by granulation. The granulation step requires specialized equipment, such as a fluidized bed or a spray dryer. WO 09 4 223 070 describes a process for the preparation of controlled release granules which comprises coating inert porous granules with a solution of an active organic polyisocyanate followed by the application of an aqueous solution of polymerization catalyst in one step additional. Japanese Patent Application No. 58-82303 (KoKai RS 59-206302) discloses a process which comprises applying a coating of an active component on a granular carrier with an organic compound containing hydroxyl or water, a surfactant non-ion and the " of the formula wherein R represents an alkyl group n is 1 to 120 and X represents a di- or polyisocyanate residue.

However, it is necessary to have improved controlled release granules prepared by a simple process in conventional mixing equipment.

According to the present invention there has been found an improved process for the preparation of controlled release granules, which is much more versatile and convenient than the processes referred to above. No adjuvants or solvents are required in the process of the present invention. It is necessary to carry out a treatment with an aqueous catalyst solution as described in U.S. Patent 4,223,070, and such treatment could lead to a non-uniform polymer coating due to non-uniform wetting. The process of the present invention may be applied to porous or non-porous granules, while the process of U.S. Patent 4,223,070 is only applicable in the first case. Also the process of U.S. Patent 4,223,070 requires the dissolution of the active component in the polyisocyanate, while the process of the present 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.

The present invention relates to a process for the preparation of controlled release granules of pesticides for direct application consisting essentially of coating 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 provide a solid cross-linked polyurea or polyurethane barrier, the term pesticide refers to water-soluble or water-insoluble chemicals commonly known as herbicides , fungicides, insecticides, nema-touched, acaricidal, miticidal, virucidal, algicidal, bae-tericidal, plant growth regulating agents, and the agricultural acceptable salts thereof. Preferred are pesticides which can be directly applied to the soil by themselves. Greater preference is given to herbicides selected from the classes of sulfonylureas, imidazolinones, uracils and herbicidal dinitroanilines; and insecticides selected from the classes of carbamates and insecticidal phosphonates. Especially preferred are the following compounds: methyl 2- (β-dimethoxy-2-pyrimidinyl) -aminocarbonyl] 7-amino-7-sulfonyl] -methylbenzoate (bensulfuron) 5-bromo-3- methyluracil (bromacil); (trifluoromethyl) -2-methylcarbamoyloxyimino-2- (methylthio) acetamide (oxamyl), N, N-diisopropyl-p-toluidine (trifluralin) S-tert-butylthiomethyl (terbufos) diethylphosphorophosphate; and O- (2,2,2-tetrachloroethyl) phosphorothioate.

By granular carrier is meant any porous or non-porous inert solid material, such as sand, aggregate 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 granular carrier designation also includes water dispersible granules of which Grlean 75 DP, Pinnacle DP and Londax are examples. 60 DP, which are products of E.I. du Pont de Nemours and Company, Wilmington, DE. Preferably the granules are in the range of about 150 to 4000 microns, more preferred in the range of 250-2000 microns. The polyhydroxylated compound designation refers to organic chemical compounds which contain two or more. plus free hydroxyl substituents, examples of which are glycols, glycerin or other polyhydroxylated alcohols or mixtures thereof, in the liquid or solid state with a low melting point. Preference is given to ethylene glycol or propylene glycol. The term polyisocyanate refers to any aliphatic, alicyclic or aromatic organic compound having two or more isocyanate (-ICO) substituents which are low melting solids or are in the liquid state at room temperature and at atmospheric pressure. Suitable examples of polyisocyanate include the following; hexamethylene-1,6-diisocyanate; m-phenylene diisocyanate; P-phenylene diisoeianate; 2,4-toluene diisocyanate; 2,6-toluene diisocyanate; 1,5-naphthalene diisocyanate; cyclohexane-2,4-diisocyanate; 1-methylcyclohexyl-2,6-diisocyanate; and toluene-2,4,6-triisocyanate; or mixtures thereof in the liquid state. Methylene-linked polyphenylisocyanates are preferred, examples of which are those sold under the tradenames " Mondur MRS " (Mobay T?

Che mical Co., Ltd., PAPI "(Dow Chemical Co.); giving greater preference to the last mentioned. Organic tertiary amines and alkyl tin carboxylic esters are suitable as polymerization catalysts. Preferred catalysts are triethylamine, trimethylamine, triethylenediamine, tri-n-butylamine, N-methylmorpholine, triethanolamine, dibutyl tin dilaurate, dibutyltin diacetate, tetanetyl acetate, laurate of dibutyltin and dibutyltin maleate. More preferred is dibutyl tin dilaurate, the process consists in adding the polyisocyanate and the polymerization catalyst containing the pesticide and water or the polyhydroxylated compound , at room temperature or at a higher temperature. Preferably the temperature is from about 23 ° C to 35 ° C.

The amounts of polyisocyanate and polymerization catalyst used in the reaction are from about 1 to 20% and from 0 to 5% by weight, respectively; preferably the amount of catalyst is comprised between 0.05 and 1%. More than 20% by weight of polyisocyanate may be added to the granule if this is to be compounded in steps, for example in layers. The water or the polyhydroxy compound should be present in an amount sufficient to ensure the reaction of the entire polyisocyanate. Although the reaction time is not critical, it is preferred that the granules can be easily handled (i.e. not aggregated) after about 20 or 30 minutes; most preferably this time is about 20 minutes.

DETAILED DESCRIPTION OF THE INVENTION

The granular bases used in the process of the present invention may be aggregated minerals, clays and other inorganic substances or organic mixtures prepared by known methods, such as granulation, prilling, compression, extrusion, / F "" and pacing. Granular bases may also be naturally occurring granules, such as sands. Examples of suitable inorganic granular bases include kaolinite, bentonite, attapulgite, vermieulite ground bricks and granular salts. Non-limiting examples of suitable organic granular bases include sugars, urea, potassium carbonate and calcium carbonate. Other suitable materials include granulated corn kernels. The process of the present invention is also applicable to commercial water dispersible granules prepared by granulating pulverized premixes of biologically active compounds and formulation aids such as binders and dispersants. Inert aggregate mineral granules impregnated with active ingredient are preferred. Preferably the granules have sizes in the range of about 150-4000 microns, more preferred in the range 250-2000 microns. The active ingredient used in the process of the present invention may be a mixture of compounds or an individual compound and may be in the form of a solid or a liquid. The active ingredient may form an integral part of the granule matrix or may be added at any time during processing, as is apparent to those skilled in the art. Preferably, the active ingredient will be a component of the granular material used or will be mixed or impregnated into the granular matrix prior to coating with the polymer. An advantage of the prior embodiment is that there is less possibility of an active ingredient reacting with the polyisocyanate when the active ingredient is a hydroxide, amino,

carboxylic acid or other equally reactive functional groups. Furthermore, by integrating the active ingredient present in or by placing it on the granular base, prior to the formation of the polymer barrier, better barrier characteristics are obtained with relatively small amounts of polymer. Thus, the polymer barrier does not thin nor weaken due to the presence of non-polymeric material. However, if necessary, it may sometimes be advantageous to add non-volatile organic substance or the active ingredient to the polyisocyanate to adjust the rate of release.

Suitable active ingredients are selected from the group consisting of herbicides, fungicides, fungicides, nematicides, nematicides, acaricides, miticides, virulants, algicides, bactericides and plant growth regulators, and their agriculturally acceptable salts. Preference is given to those active ingredients which can themselves directly be applied to the soil. Greater preference is given to the herbicides selected from the classes of sulfonylureas, imidazolinones, uracic and dinitroanilines; and the intranetants chosen in the classes of the carbamates and phosphonates. Specific examples of preferred active ingredients are the following: methyl 2- [2-hydroxy-4,6-dimethoxy-2-pyrimidinyl) amino] carbonyl] amino] sulfonyl] methylbenzoate; 5-bromo-3-sec-butyl-6-methyluracil; , trifluor-2,6-dinitro-], D-dipropyl-β-toluidine; N, N-dimethyl-2-methylearbamoyloxyimino-2- (methylthio) acetamide; Ο, Ο-S-tert-butylthiomethyl diethylphosphorosteate; and 0- (1,2,2-tetrachloroethyl) -phosphorothioate. The designation " polyhydroxylated compound " as used in the context of the present invention includes organic compounds which contain at least two free hydroxyl substituents (-OH). Examples of suitable polyoxyhydroxylated compounds include glycols, glycerol and other polyhydroxylated alcohols or mixtures thereof, or mixtures thereof with water, both of which are in the liquid or solid state. Preferred polyhydroxylated compounds are ethylene glycol and propylglycol. Water may be used instead of part or all of the polyhydroxy compound or the mixture of the polyhydroxylated compounds. While solid polyhydroxy compounds are useful in the process of the present invention, preference is given to their use in liquid form by dissolution in a second liquid polyhydroxy compound. The term " polyisocyanate " as used in the context of the present invention means any organic compound containing at least two isocyanate (-NOCO) substituent groups. When solid polyisoanates are used in the process of the present invention, they should preferably be pre-dissolved in a second liquid polyisocyanate.

Preferred polyisocyanates are methylene-linked polyphenyl isocyanates, the non-limiting examples of which are polyisocyanates.

include those sold under the tradenames " Mondur MRS-M (Mobay Chemical Co.) " PAPI5, " (Dow Chemical Co.); giving greater preference to the latter.

Although it is not necessary to use catalyst in the polymerization reaction which can be accelerated solely by heating, the process is preferably completed in less than 60 minutes, more preferably up to 30 minutes at room temperature. To achieve this result, the polymerization reaction can be accelerated by addition of known catalysts for the preparation of ureas and urethanes, such as organic tertiary amines or alkyl tin ester carboxylic esters, to the polyisocyanate prior to application to the granular substrate. Preferred catalysts are triethylamine, trimethylamine, triethylene diamine, tri-n-butylamine, N-methylmorpholine, triethanolamine, dibutyltin dilaurate, dibutyltin diacetate, tributyltin acetate, dibutyl tin laurate and matteate of dibutyltin. Dibutyl tin dilaurate is more preferred. The process of the present invention is to add the optional polyisocyanate and polymerization catalyst to the granules containing the active ingredient and water or the polyhydroxylated compound at or above room temperature. Preferably, the temperature is from about 23 ° C to 35 ° C. The amount of polyisocyanate used in the process is from about 1 to 20% by weight based on the amount of granular material. More than 20% by weight of polyisocyanate may be added to the granules when applied in sequential layers, leaving sufficient time to allow each layer to polymerize before the next coating layer is applied. When a polymerization catalyst is used, preferably its amount is up to about 5% by weight relative to the amount of polyisocyanate; more preferably, the amount of catalyst is comprised between 0.05 and 1%, the catalyst is most advantageously applied in solution with the polyisocyanate or the polyhydroxylated compound to obtain a uniform polymerization reaction. The water or the polyhydroxylated compound must be present in amounts sufficient to ensure the reaction of the entire polyisocyanate. The barrier formation reaction occurs at the interface between the upper layer of the isocyanate phase and the water or hydroxylated material and generally continues until the entire isocyanate function is consumed. The presence of excess of oxygen or hydroxyl function does not normally affect the barrier, since these compounds may be trapped under the formed barrier. Although the reaction time is not critical, "the granules should preferably be readily handled (i.e., not aggregated) after about 20 to 30 minutes; most preferably this time is about 20 minutes.

When water is used as a co-reactant with the polyisocyanate, some isocyanate groups undergo hydrolysis to form an amine function, followed by self-polycondensation by reaction with the unreacted isocyanate groups. Under these conditions, a polyurea is formed. When a polyhydroxylated compound is used, a polyurea is formed as a barrier. When the polyhydroxylated compounds pu Ψ w

% Polyisocyanates have more than two hydroxyl or isocyanate groups, cross-linked polymer barrier coatings are formed. If a mixture of water and at least one organic polyhydroxy compound is used, the obtained polymer barrier is a polyurea-urethane ·

Reduction of the release rate is generally achieved by the use of aromatic polyisocyanates instead of aliphatic polyisocyanates or by increasing the amount of polymer forming ingredients (which controls layer thickness). The rate of release can also be achieved increasing the degree of cross-linking by using reagents containing more than two hydroxyl or isocyanate groups to effect cross-linking and not using diluents.

In the examples which follow and which further illustrate the process of the present invention, release rates were measured in buffered water at pH T at room temperature under static conditions. In all cases, a sufficient amount of water was used to exert to a large extent the amount necessary to dissolve the active ingredient. The water was stirred immediately prior to sampling to ensure a uniform concentration of dissolved active ingredient. The concentration of active ingredient was measured by HPLC. The percentages mean percentages by weight, unless otherwise indicated. EXAMPLE 1

Granules of 0.08% diethyl insecticide 0- (1,2,2-tetrachloroethyl) phosphorothioate (4.08 g) containing A% propylene glycol and 10% active ingredient were mixed with 1.0 g of a solution of 0.01 g of dibutyltin dilaurate in PAPI® 901 (Dow Chemical Ca). After 30 minutes, the granules flow freely. The volatility of the O- (1,2,2,2- tetrachloroethyl) phosphorothioate in these coated granules with the unmodified granules at a temperature of 45-60 ° C in an oven with an air atmosphere. After 44 hours, the coated granules lost 0.12 g of active ingredient while the uncoated sample lost 0.27 g, which shows that the polymer coating retarded the volatilization of the active ingredient. EXAMPLE 2

9.0 g of water dispersible granules containing 60% methyl 2- [7,7,7,6-dimethoxy-2-pyrimidinyl] amino] carbonyl] amino] sulfonyl] methylbenzoate (Londax 60 DP; EI du Pont de Nemours and Company), with 0.3 g of propylene glycol followed by a solution of 1.0 g of PAPIR 901 (Dow Chemical Co.) and 0.01 g of dibutyl tin dirauto. After being allowed to stand in an open cup for about 30 minutes, the somewhat sticky mixture becomes frankly flowing, indicating that the polyurethane coating polymerization has occurred. The granules were added to 500 ml of water and allowed to stand. ο for 3 days. The granules retain their integrity, although they slowly lose some active ingredient: 12% in 21 hours, 31% in 46 hours, and 100% in 300 hours. The uncoated granules completely disintegrate in excess of water after about 2 minutes and lose 100% of the active ingredient in less than 2 hours. EXAMPLE 3

In order to reduce the porosity, the previous polymer impregnation of Flores attapulgite granules is carried out? LVM 8-16 mesh (Florex LVM, Floridin Co), by mixing 120 g of the material with 5 g of propylene glycol followed by 10 g of PAPIR 901 containing 0.5% dibutyltin diraurate. After curing for 1 hour to obtain a polyurethane-containing crosslinked product, 16.6 g of precoated granules are mixed with 0.627 g of 2- [2- (2,274-, 6-dimethoxy-2-pyrimidinyl] amino] -hexahydroxy] (95.7%), 0.39 g of propylene glycol, followed by 0.8 g of PAPI-901 (Dow Chemical Co.) containing 0.02 g of dibutyltin diraurate. The sample is allowed to cure in an open vessel to give a product of 3% active ingredient with a cross-linked polyurethane-urea coating. The rate of excess release of buffered water at pH 7 is 15% at 162 hours and 24% at 451 hours. EXAMPLE 4

76.4 g of sand (diameter 250 to 840 microns) were mixed with 0.2 g of propylene glycol, followed by 0.6 g of PAPIR 901 containing 0.063 g of dibutyltin dilaurate. Thereafter, 2.5 g of 2- [4,4,6-dimethoxy-2-pyridinyl] amino] carbonyl] amino] sulfonyl] -methyl benzoate, with stirring to give a mixture containing 3% active ingredient. After curing, the rate of excess release of buffered water at pH 7 is 42% at 67 hours and 96% at 499 hours. EXAMPLE 5

The procedure of Example 4 is repeated with

R except that PIPI 901 solution was added last to give granules with a slower release rate: 35% in 114 hours and 74% in 525 hours. EXAMPLE 6

The procedure of Example 4 is repeated for the purpose of replacing the propylene glycol with 0.16 g of water. The release rates for polyurea coating are 63% in 305 hours and 100% in 665 hours. EXAMPLE 7

17.3 g of sand, 0.627 g of 2- [4,4,6-dimethoxy-2-pyrimidinyl] amino] carbonyl] amino] sulfonyl] methylbenzoate and 0.46 g of propylene glycol were added and 2.02 g of technical grade toluene-di- cyanate (80% isomer 2,4 and 20% isomer 2,6) containing 0.039 g of dibutyltin dilaurate. The cured product contains 2.9% active ingredient. The release rates are 10% at 162 hours and 16% at 451 hours. Similar results are obtained when using 2.0 g of a solution

R to 50% technical grade toluene-2,4-diocyanate and PAPI 901, instead of technical grade toluene-2,4-diisocyanate alone. EXAMPLE 8

9.0 g of water-dispersible granules of Krovar I (Ξ.Ι. du Pont de Nemours & Co.), containing 40% bromacil and 40% diuron, are treated successively with 0.2 g of propylene glycol and 0.51 g PAPI 901 containing 0.4% dibutyltin dilaurate. The rate of release of the brommacil in the excess granules of water is 76% in 21 hours and 83% in 46 hours. The granules retain their integrity for over a month in excess of water, although they continue to release brommacil. Uncoated control granules disintegrate and release all of their brommacil content in less than 1 hour.

Claims (17)

-7- A process for the preparation of controlled release granules of pesticides, for direct application, characterized in that a granular carrier is coated with a pesticide and a polyhydroxylated compound, mixtures of compounds polyhydroxy compounds or mixtures of water and at least one polyhydroxylated compound, or water alone, with a liquid polyisocyanate or a mixture of polyisocyanates and, optionally, a polymerization catalyst, resulting in a polymerization reaction interfacial bond, to provide a solid, cross-linked polyurethane or polyurea barrier. -18 2. A process according to claim 1, characterized in that it is carried out at a high temperature. 3. A process according to claim 1, characterized in that the pesticide is a herbicide or an insecticide. 4. Process of. according to claim 3, characterized in that the herbicide is selected from sulphonyl ureas, imidazolinones, uracils and dinitroanilines and the insecticide is one. phosphorothioate. 5. A process according to claim 1, characterized in that: the granular vehicle is chosen from sand and aggregate clays. 6. A process as claimed in claim 5, wherein the granular carrier has particle sizes of from about 150 to 4000 microns. 7. A process according to claim 1, wherein the polyhydroxylated compound is selected from ethylene glycol and propylene glycol. A method according to claim 1, characterized in that It is characterized in that the polyisocyanate is a methylene-linked polyphenylisocyanate. 9. A process according to claim 1, wherein the polyisocyanate is a toluene diisocyanate. 10. A process according to claim 1, characterized in that the polyisocyanate is a mixture of a methylene-linked polyphenylisocyanate and a toluene-2,4-diisocyanate. 11. A process as claimed in claim 1, wherein the polymerization catalyst is selected from organic tertiary amines and alkyl tin carboxyl esters. 12. A process according to claim 1 for the preparation of controlled release granules of pesticides for direct application. characterized in that a polyisocyanate or a mixture of polyisocyanates and a polymerization catalyst is added to granules containing a pesticide and water or polyhydroxylated compounds or mixtures thereof at a temperature at least equal to room temperature in that the amount of polyisocyanate and the polymerization catalyst used is between about 1% and 20% and% and 5% by weight, respectively, resulting in an interfacial polymerization reaction, to obtain a solid, crosslinked polyurethane or polyurethane barrier, the amount of water or polyhydroxylated product being sufficient to react with the entire polyisocyanate. 13. A process according to claim 10, characterized in that the reaction time is from about 20 to 30 minutes. 14. A process as claimed in claim 10, wherein the pesticide is a herbicide. 15. A process as claimed in claim 12, wherein: if desired the herbicide is selected from sulfonyl ureas, imidazolinones, uracils or dinitroanilines. 16. The composition according to claim 10, wherein the pesticide is an insecticide. A process according to claim 10, wherein the insecticide is a phosphorothioate. 18. A composition according to claim 10, wherein the granular carrier is selected from sand and aggregate clays. 19. A process as claimed in claim 14, wherein the granular carrier has a particle size of from about 4,000 to about 4,000 microns. 20. A process according to claim 10, wherein the polyhydroxylated compound is selected from ethylene glycol and propylene glycol. 2.1. - Process of. according to characterized in that the polyisocyanate is a methylene linked polyphenylisocyanate or a toluene diisocyanate or mixtures thereof, 22. Process according to claim 1, Claim 10, characterized in that the polymerization catalyst is selected from organic tertiary amines and alkyl tin carboxyl esters. Lisbon, January 11, 1991 The Official Agent of Property Industry * < »