Plant protecting and regulating compositions – Plant growth regulating compositions – Plural active ingredients
Reexamination Certificate
2002-02-14
2004-03-30
Clardy, S. Mark (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Plural active ingredients
C504S128000, C504S118000, C504S365000, C504S363000
Reexamination Certificate
active
06713433
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions useful in agriculture comprising at least two herbicidal active ingredients, one of which is an oil-soluble herbicide and the other of which is a water-soluble herbicide. More particularly, the present invention relates to stable liquid concentrate compositions of such herbicidal active ingredients.
BACKGROUND OF THE INVENTION
As a means of killing or otherwise controlling unwanted plants, e.g., weeds, in agriculture and related endeavors, it is desirable to treat such plants or the locus thereof with chemical herbicides. A common method of herbicidal treatment in agricultural endeavors is to treat a field to remove or control unwanted vegetation as preparation for planting a crop plant, a method otherwise known as “burndown.” However, single herbicides typically lack the weed control spectrum, e.g., the range of weed species effectively controlled by the herbicide, to fully control the diversity of weeds in a field. Therefore, it is common to apply two or more herbicides simultaneously in order to achieve the desired spectrum of control. To facilitate the simultaneous application of two or more herbicides, it is common to package the different herbicides separately as concentrate formulations, which can be admixed with water in a spray tank by the end user, a method also known as tank-mixing. More conveniently, however, the different herbicides can be coformulated in a single concentrate formulation, requiring only dilution in water by the end user prior to application by spraying. Such a formulation is often known as a package-mix.
Further, applying combinations of two or more herbicides simultaneously to a field may be necessary or desired for synergistic effects other than an increased control spectrum. For example, many water-soluble herbicides such as N-(phosphonomethyl)glycine have prolonged visual symptomology, that is, it takes a relatively long period of time (i.e., up to two weeks or more) for susceptible plants to show the visual effects of treatment. Generally, such extended periods without any visual indication of herbicidal effectiveness detracts from the commercial value of a herbicidal product. Therefore, it is often beneficial to combine two or more herbicides in a tank mix or a package-mix that will provide for more rapid burndown and earlier visual symptomology, thus improving the value of the overall herbicidal product.
Package-mix formulations present numerous challenges to the formulator of agricultural chemicals such as herbicides. For example, the formulation should contain the herbicidal active ingredients at as high a total concentration as possible, for maximum convenience to the end user and to minimize packaging and shipping costs, while keeping the active ingredients within the desired weight ratios with respect to each other. Most importantly, the package-mix formulation must exhibit sufficient physical and chemical stability to have an effective shelf life of at least a few months, preferably at least a year, and ideally at least two years.
Where the package-mix formulation contains a first herbicide that is oil-soluble and that undergoes chemical degradation, even at a slow rate, in water, and a second herbicide that is water-soluble, the challenge of providing a storage-stable liquid concentrate formulation is particularly acute. Water used as the solvent for the second herbicide acts as a degradation medium for the first herbicide. Typically, hydrolysis is the most common water-mediated degradation mechanism; however, package-mix formulations with chemically unstable active ingredients are also subject to oxidation, dehalogenation, bond cleavage, Beckmann rearrangement and other forms of degradation.
Liquid concentrate coformulations of two herbicidal active ingredients, one of which is water-soluble and the other of which is oil-soluble, are known in the art in the form of emulsions, most commonly oil-in-water type emulsions having a discontinuous oil phase dispersed in a continuous aqueous phase with the aid of one or more emulsifying agents. The water-soluble active ingredient is contained predominantly in the aqueous phase and the oil-soluble active ingredient is contained predominantly in the oil phase. The individual oil particles can be large enough to interfere with the transmission of light, giving rise to a cloudy or milky emulsion known as a macroemulsion. However, where the individual oil particles are so small as to allow light to be transmitted without noticeable scattering, the emulsion is clear, i.e., transparent, and is known as a microemulsion. Microemulsions offer a number of practical advantages, one of the most important being that they typically remain homogeneous without agitation for long periods of time. In this respect, a microemulsion formulation can be handled by an agricultural technician or other user with the same ease and convenience as a simple aqueous solution. However, selecting excipient ingredients for the preparation of a microemulsion is not necessarily straightforward or easy.
Difficulties in preparing stable microemulsions suitable for effective weed control and good crop safety are compounded when the active ingredients to be coformulated are a water-soluble herbicide and an oil-soluble herbicide. For example, one challenge is that water-mediated chemical degradation, e.g., hydrolysis, of the oil-soluble herbicide must be minimized. Minimizing hydrolysis is especially difficult in microemulsions, where the oil particles containing the oil-soluble herbicidal active are extremely small and therefore present a very large interfacial area with the aqueous phase.
Another challenge is that microemulsions must contain surfactants, which tend to facilitate transfer of the oil-soluble herbicidal active across the large interface between the oil and aqueous phases, increasing the potential for chemical degradation. However, surfactants are important to the microemulsion composition, functioning as emulsifying agents to physically stabilize the microemulsion, as dispersants to prevent aggregation of oil particles when the microemulsion is diluted in water for application to plants, and as adjuvants to enhance herbicidal efficacy of one or both active ingredients, for example by improving retention on or adhesion to foliar surfaces of the applied composition or by improving penetration of the active ingredient(s) into or through the cuticles of the plant foliage.
SUMMARY OF THE INVENTION
Among the several features of the invention, therefore, may be noted the provision of a novel liquid concentrate herbicidal composition useful in agriculture wherein at least two herbicidal active ingredients, one of which is a water-soluble herbicide and the other of which is an oil-soluble herbicide, can be coformulated; the provision of such a novel composition comprising a continuous aqueous phase having a discontinuous oil phase dispersed therein; the provision of such a novel composition having a broader weed control spectrum; the provision of such a novel composition that exhibits rapid burndown and early visual symptomology; the provision of such a novel composition that allows for higher loading of herbicidal active ingredients; and the provision of such a novel composition which has prolonged storage stability and is relatively easy to use.
Briefly, therefore, the present invention is directed to a liquid concentrate herbicidal emulsion composition comprising a water-soluble herbicide in water and an oil-soluble herbicide. The water-soluble herbicide and the oil-soluble herbicide are independently present in a concentration that is biologically effective when the composition is diluted in a suitable volume of water and applied to the foliage of a susceptible plant. The composition further comprises a stabilizing amount of one or more water-soluble chlorides selected from hydrochloric acid, alkali metal chlorides, ammonium chloride, low molecular weight organic ammonium chlorides and quaternary ammonium chloride surfactants sufficient to inhibit subst
Clardy S. Mark
Monsanto Technology LLC
Schaper Joseph A.
Senniger Powers Leavitt & Roedel
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