Certain N-hydrocarboyl phosphoroamidothioates and phosphoroamidodithioates .have high insecticidal activity. A particularly important commercial insecticide within these classes of compounds is the insecticide ORTHENE.RTM., which can be systemically taken up by a plant so that insects which feed and/or live on the plant are killed, in addition to those insects which directly ingest or are contacted by the insecticide. See U.S. Pat. Nos. 3,716,600, 3,845,172 and 3,914,417. ORTHENE.RTM. is commercially produced as technical grade chemical of about 97 to 99.5% purity. One method of formulating technical grade ORTHENE.RTM. for commercial use is to mix the technical grade powder with an anti-caking agent, such as fumed silica, and a wetting agent. The wetting agent is utilized to wet the ORTHENE.RTM. and the anti-caking agent is used to prevent agglomeration of the ORTHENE.RTM. in its container.
The wetting agent is utilized to improve the spread-out of ORTHENE.RTM. when it is applied to crops as a spray solution, or when applied as a dust, after exposure to moisture via rain, dew, or irrigation. The powdered commercial forms of ORTHENE.RTM. are available in dilutions referred to as ORTHENE.RTM. 90S, ORTHENE.RTM. 75S, ORTHENE.RTM. 50S, and in other commercial dilutions.
The powder form allows formulations of ORTHENE.RTM. to relatively high concentrations, e.g., ORTHENE.RTM. 90S. Other, lower concentrate formulations are targeted to discrete markets using a soluble powder signified as -xxS. In most cases, the application of ORTHENE.RTM. xxS to the crop is via a water solution spray. The anti-caking agents, while promoting product flowability during the solution/mixing process, do not enhance the solution method of application. On the other hand, inherent to all powders, handling difficulties due to dust make this form of product less desirable than liquids and agglomerate forms. Furthermore, ORTHENE.RTM. has a characteristically objectionable odor (believed to be organothio compounds) which is compounded by the problems with dust.
ORTHENE.RTM. is available in liquid form, which minimizes or eliminates airborne contamination due to dust. However, due to storage stability limitations of solutions, its concentration is limited to a maximum of 25%, the balance being solvent and adjuvants. ORTHENE.RTM. in a liquid formulation has a solvent and packaging expense as well as a container disposal requirement that makes it less attractive to the consumer on the basis of price and empty container disposal requirements.
An agglomerate form of ORTHENE.RTM. which also minimizes airborne contamination due to dust, has been constrained to dilute concentrations of ORTHENE.RTM. applied to large particles by spraying and then dried, or as a dilute concentration of ORTHENE.RTM. combined with binders and anti-caking agents to form agglomerates via processes known to those skilled in the art, such as, pan granulation, extrusion, fluid granulation, pelletizing. The concentration of ORTHENE.RTM. via these methods has heretofore been limited to a concentration no greater than about 36% to 50%, with known commercial products typically no more than 5% ORTHENE. The limit on concentration of ORTHENE.RTM. was due to the melt property of ORTHENE.RTM. limiting the feasible operability of this form of product. Concentration of active ingredient is further limited by the ability of binding agents to form agglomerates, i.e. a minimum amount of any particular binding agent is required in order to meet physical properties of attrition resistance, crush strength and bulk density. In the case where liquid ORTHENE.RTM. solutions were sprayed on agglomerates and then dried, the limitation of concentration was due to the practical wetting ability of the receiving agglomerate. Too much liquid applied would form a mud. At these low levels of ORTHENE.RTM. concentration, commercial products require more handling and are less attractive formulations for applications of ORTHENE.RTM. made via solution spraying.
The ORTHENE.RTM. xxS formulations have problems due to the anti-caking agent ingredients. Anti-caking agents are not soluble in water (the typical application spray solvent) or other normal solvents. Due to their insolubility, they can settle in the applicator's spray tank. The settled anti-caking agents plug spray nozzles which detracts from the marketability of the ORTHENE.RTM. xxS product line. This spray nozzle plugging problem can occur when ORTHENE.RTM. xxS products are tank mixed with other commercial pesticides, which is a normal farming industry practice. While methods to minimize the occurrence of anti-caking agent settling have evolved, they require special procedures to avoid nozzle plugging conditions, which adds to the inconvenience of using ORTHENE.RTM. xxS.
Furthermore, anti-caking agent segregates in the manufacturing process equipment during material handling procedures and forms insoluble bits of anti-caking agent which can cause nozzle plugging.
Therefore, alternative forms to ORTHENE.RTM. powders, that resolve problems characteristic of dusts are desired by both the manufacturer and the marketplace. One possible alternative to a powdered ORTHENE.RTM. is in the form of a pellet: a cylindrically shaped solid. Pellets practically eliminate the dust problems and reduce the surface area-to-weight ratio which mitigates the odor problem.
However, currently available ORTHENE.RTM. pellets, as mentioned above, contain relatively small amounts of ORTHENE.RTM. typically no more than 5% active ingredient. Attempts to manufacture technical assay (approximately 97% active ingredient) ORTHENE.RTM. pellets from the dry ORTHENE.RTM. technical powder have been unsuccessful. The anti-caking agents and binders needed to make the currently available ORTHENE.RTM. pellets add to product cost, can cause excess wear and tear on equipment, and by dint of being a major fraction of the product formula, require more bulk product than the concentrated powders in order to deliver effective amounts of ORTHENE.RTM. to the protected crop.
Additionally, the anti-caking agents and binders used to form the currently available ORTHENE.RTM. pellets have the same water insolubility problem that the anti-caking agent has in ORTHENE.RTM. powdered formulae. Because of that, commercial ORTHENE.RTM. pellet products are limited to use by direct application to the crop; i.e., placing individual pellets on or around each plant, which is impractical for most commercial farming ventures.
It is thus an object of the present invention to provide pelletized forms of insecticidal N-hydrocarboyl phosphoroamidothioates and phosphoroamidodithioates containing high concentrations of insecticidal active ingredient.
It is a further object of the present invention to provide methods for making such pelletized compositions.
These and other objects of the invention will be apparent from the following description and from the practice of the invention.