Dry spreadable carrier for pesticides

Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants

Reexamination Certificate

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C424S405000, C424S406000, C424S409000, C424S417000, C424S418000, C424S419000, C424S420000

Reexamination Certificate

active

06416775

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to dry spreadable compositions; their use as carriers of bioactive materials; and methods for preparing and using said compositions. More specifically, the invention relates to surfactant-diatomaceous earth compositions for agricultural use in the form of dry spreadable granules and methods of preparing same, and even more specifically for their use in the broadcast delivery of pesticides to the soil.
2. Description of Prior Art and Problems
An organic pesticide is a bioactive material which destroys or inhibits the action of plant or animal pests. The general term pesticide includes insecticides, herbicides, fungicides, plant growth regulators, rodenticides, and miticides.
Organic pesticides are widely used in soil and turf by both consumers and commercial operators. Pesticide compounds may be used alone; however, usually they are formulated into conventional forms such as dust, granule, microgranule, wettable powder, flowable powder, emulsion, microcapsule, oil, aerosol, etc., using techniques well known in the art. To improve or stabilize the effects of the pesticide, the pesticide is blended with suitable adjuvants and then used as such or after dilution if necessary. Examples of adjuvants include carriers, diluents, spreaders, emulsifying agents, wetting agents, dispersion agents, or fixing agents.
The present invention is directed towards dry spreadable diatomaceous earth granules, and towards methods of preparing such granules, which can be applied with a dry spreader to a target area and, when exposed to water via, for example, rain or irrigation, will not only readily disintegrate, but actively spread on solid substrates so as to achieve disintegration area diameter to original granule diameter ratios larger than that heretofore realized. These dry spreadable granules are primarily used as carriers for bioactive materials such as pesticides and are easy to formulate, ship, store, and apply.
SUMMARY OF THE INVENTION
This invention provides dry spreadable compositions; their use as carriers of bioactive materials; and methods for preparing and using said compositions. Specifically, the invention relates to surfactant-diatomaceous earth compositions in the form of dry spreadable granules and methods of preparing same, and more specifically to their use in the broadcast delivery of pesticides to the soil.
The granules utilize, in addition to the diatomaceous earth, a surfactant composition designed to provide binding, rewetting and disintegration properties to the granules.
DETAILED DESCRIPTION OF THE INVENTION
The instant invention relates to the discovery of a granule which can function as a carrier for pesticides or fertilizers in a broadcast or dry spreading application. Granules for such a use have to possess certain specific characteristics which are not necessary or critical in compositions designed for admixing in large volumes of water such as tank mixes and ultimately sprayed upon sites to be treated. Bioactive-carrier compositions are often referred to as wettable powders, water dispersible granules, etc. as opposed to the dry spreadable or broadcast granules of the instant invention. Characteristics which are specific to dry spreadable granules include hardness and an ability to maintain integrity upon normal, commercial handling in a dry spreading operation and yet be capable of quickly disintegrating or scattering upon what may be a minimal exposure to water, such as, for example, a light rain.
This ability to disintegrate or scatter on a solid substrate can be primarily measured by the “Disintegration” test, as described herein, which measures what happens to a typical granule when a drop of water lands on it. Essentially, the disintegration is observed and recorded by measuring the area covered by the granule composition after being exposed to a drop or drops of water compared to the area covered by the original dry granule. Of course, the higher the ratio, the more efficacious the delivery of the bioactive that is being carried by the granule.
Once the granule has been disintegrated or scattered by the droplet, the characteristics common with the water dispersible products also come into play such as the composition's ability to disperse in large volumes of water and this property can be measured via tests such as the “Breakup” test as also described herein.
The instant invention relates to the discovery of a dry spreadable diatomaceous earth granule which, when exposed to water on a solid substrate, has a high disintegration area diameter to original granule diameter ratio. As a result, when the granules of this invention are broadcast upon the locus to be treated, e.g., soil, and then water treated, the area affected by the granule formulation is much enhanced over that realizable when the dry spreadable granules of the prior art are similarly broadcast.
By diatomaceous earth is meant a silica material characterized by a large surface area per unit volume. This is the result of an enormous number of fine pores within the structure. Diatomaceous earth is a naturally occurring material and consists mainly of accumulated shells or frustules of intricately structured amorphous hydrous silica secreted by diatoms. Diatoms are single-celled golden brown algae of the Bacillariophyceae class. The enhanced absorption/adsorption properties of the diatomaceous earth result from the very large internal surface area.
The effective diatomaceous earth of this invention has a surface area in the range of from greater than about 5 square meters per gram to less than about 90 square meters per gram, preferably from greater than about 10 to less than about 60 square meters per gram and a pore volume in the range of from greater than about 2 cubic centimeters(cc)per gram, to less than about 5 cc per gram, preferably from greater than about 3 cc per gram to less than about 4 cc per gram. Natural diatomaceous earth is preferred for this invention.
Diatomaceous earth is present in the granule composition at from about 35 to about 95 weight percent, preferably from about 50 to about 95 weight percent of the total diatomaceous earth, surfactant, and pesticide granule composition.
The surfactant composition of the present invention is present at from about 5 to about 40 weight percent, preferably from about 5 to about 20 weight percent of the total diatomaceous earth/surfactant/pesticide granule composition. The surfactant composition provides three essential properties to the dry spreadable granules.
First, the surfactant composition must act as a binder for the particles in the granule so that after the processing and agglomerating water used in the initial preparation of the granule has been driven off, residual surfactant will act as a binder to form a reasonably hard, easily handleable, i.e., a non-dusty, dry spreadable granule.
Second, the surfactant composition must possess a good rewetting ability such that when the granule is applied to the site to be treated and subsequently exposed to water, the surfactant composition will enable the water to easily penetrate the interstices of the individual diatomaceous earth particles quickly, i.e., “wet” the internal surface areas of the particles. It is theorized that this rapid rewetting of the internal surfaces results in a displacement of the air initially entrapped within the particles which then provides an additional scattering mechanism for the granules of this invention.
Third, the surfactant composition must be able to aid in the breaking up and rapid spreading of the particles initially in the granule.
In summary, the surfactant composition should possess the characteristic properties of being a good binder, rewetting agent, and disintegration aid. These properties could, of course, be found to a limited extent in a single component surfactant composition, but preferably at least a two-component composition is utilized. As will be noted below, polymeric dispersants, i.e., those with repeating units or bulky dispersants often can function a

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