Plant protecting and regulating compositions – Plant growth regulating compositions – Organic active compound containing
Reexamination Certificate
2000-06-28
2002-09-17
Clardy, S. Mark (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Organic active compound containing
C504S365000
Reexamination Certificate
active
06451735
ABSTRACT:
This invention relates to a glyphosate formulation and in particular to a high-strength aqueous concentrate formulation of glyphosate.
N-phosphonomethylglycine (referred to herein by the common name glyphosate) is a well-known herbicide which is generally used in the form of its salts. Glyphosate may be formulated in a wide variety of liquid and solid compositions designed to cover a range of commercial applications. This invention concerns liquid concentrate formulations which are designed to be diluted prior to use. Many such liquid concentrates are sold commercially but there are strong commercial and environmental reasons for seeking to increase the concentration of glyphosate in the aqueous formulation beyond that which is commonly available. It is readily apparent that a high-strength aqueous concentrate formulation provides a given dose of glyphosate in a smaller liquid volume, resulting in significant advantages in terms of reduced transport, storage and handling costs and reduced and more convenient container disposal.
It is well understood that in commercial practice it is necessary to enhance the activity of glyphosate by the use of one or more surfactants and many effective individual surfactants or mixed surfactant systems have been published in the literature. It is possible to add a desired surfactant system separately into a tank mix at the same time that the aqueous glyphosate concentrate is diluted, and the surfactant system may thus be omitted from the concentrate and added separately at the tank mix stage. Clearly however the addition of a separate component at the tank mix stage constitutes and additional step prior to spraying the herbicide and requires the user to undertake accurate measurement of mixing volumes to ensure the correct proportions in the final product. There is a need therefore for high-strength glyphosate concentrates in which an effective proportion of a surfactant system is “built-in” to the composition. It is this factor which has hitherto limited the practical realisation of effective high-strength glyphosate concentrates containing surfactant, since such concentrates have to be physically stable over extended storage at the possible extremes of ambient temperatures likely to be encountered in commercial usage. It is exceptionally difficult to “build-in” effective levels of conventional surfactant systems to high-strength formulations, for example formulations containing glyphosate salts at a concentration of greater than 400 or 450 g/l based on glyphosate acid.
A still further problem which is encountered in highly concentrated systems incorporating both a salt of glyphosate and a surfactant system is that of viscosity. The advantages of having a low-volume, high-strength composition will to a greater or lesser extent be negated in practice if the composition is too viscous to be poured conveniently from the container or is too viscous for residues to be washed rapidly from the container. This is of particular importance if the product is to be supplied in bulk for large-scale users.
Many salts of glyphosate are disclosed in the literature, but extensive commercial use has only been made of liquid concentrates containing the trimethylsulphonium salt and the isopropylamine salt. The ammonium or sodium salt is used in some solid formulations. We have now found that the potassium salt of glyphosate is especially well suited to the provision of a high-strength aqueous concentrate of glyphosate since it is readily soluble in water to form relatively high density solutions (about 1.45 g/cc). Extensive investigation of conventional surfactant systems has shown however that it is exceptionally difficult to build-in effective levels of surfactant to provide a physically stable high-strength composition containing salts of glyphosate such as the potassium salt.
According to the present invention there is provided a high-strength aqueous glyphosate concentrate comprising the potassium salt of glyphosate, an alkylglycoside surfactant and an alkoxylated alkylamine surfactant.
As used herein, the term “high-strength” aqueous glyphosate concentrate indicates a concentrate in which the glyphosate concentration is greater than 400 g/l and more particularly greater than 440 g/l based on glyphosate acid content. It should be noted that, unless otherwise stated, all concentrations of glyphosate are given herein in terms of the percentage by weight of glyphosate acid even when the glyphosate is present as a salt. In general a practical upper limit of the glyphosate concentration will be determined by viscosity considerations. As discussed below, viscosity modifying agents may be required if the concentration is much in excess of 500 g/l, whilst formulations in which the concentration is in excess of 550 g/l will tend to be too viscous for effective commercial usage using conventional equipment. Compositions of the present invention wherein the glyphosate content is from about 440 gl/l to about 540 g/l are especially effective.
Preferably the total content of the alkylglycoside and alkoxylated alkylamine surfactant system in the aqueous concentrate is from about 160 to 300 g/l, for example from about 200 to 270 g/l. Whilst additional surfactants other than the alkylglycoside and the alkoxylated alkylamine may be used if desired, the presence of such additional surfactants may adversely affect the formulation stability when used at the upper limit of concentration of alkylglycoside and alkoxylated alkylamine.
The ratio of alkylglycoside to alkoxylated alkylamine in the surfactant system is preferably from about 1 part by weight of alkylglycoside per 1 part by weight of alkoxylated alkylamine to about 5 parts by weight of alkylglycoside per 1 part by weight of alkoxylated alkylamine. An especially preferred ratio is from about 1.5 or more preferably 2 parts by weight of alkylglycoside per 1 part by weight of alkoxylated alkylamine to about 4 parts by weight of alkylglycoside per 1 part by weight of alkoxylated alkylamine.
Whist the scope of the present invention is not to be taken as being limited by any one particular theory and whilst the mode of action of surfactants is extremely complex, it is believed that the alkylglycoside and the alkoxylated alkylamine function by different general mechanisms and are able to work together to provide the maximum adjuvant effect together with the optimum capacity to be built-in to the high-strength formulation without loss of physical stability of the formulation. Specifically, the alkylglycoside is believed to operate essentially passively, being located largely on the leaf surface and moderating the physical properties of the spray solution as it dries to ensure effective uptake. One phenomenon which is believed to be a consequence of this mode of action is that if the loading of alkylglycoside is increased past a particular optimum range, the enhancement of activity is no longer proportional to the loading of alkylglycoside. Addition of further alkylglycoside then has relatively little effect. Alkoxylated alkylamines on the other hand are believed to operate by a more active mechanism in which the alkoxylated alkylamine penetrates the leaf cuticle and provides enhancement of biological activity by facilitating penetration of the active ingredient into the plant system.
Thus whilst it would be possible to incorporate a relatively high loading of alkylglycoside into a high-strength potassium glyphosate formulation, the enhancement of biological activity would tend to be less than optimum and in addition the viscosity of the resultant solution would tend to be undesirably high. Alkoxylated alkylamines on the other hand have a relatively low compatibility threshold in high-strength glyphosate concentrates. We have found however that the claimed glyphosate composition combines the high-strength capability of the potassium salt with the optimum “passive” enhancement of activity by the alkylglycoside and the “penetrant” enhancement provided by relatively low levels of alkoxylated alkylamine which are compatible with the
Bean Michael John
Formstone Carl Andrew
Hopkins Derek John
Ottaway Alan Victor
Clardy S. Mark
Hale and Dorr LLP
Syngenta Limited
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