Plant protecting and regulating compositions – Plant growth regulating compositions – Organic active compound containing
Reexamination Certificate
2001-11-23
2004-05-11
Clardy, S. Mark (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Organic active compound containing
C504S355000
Reexamination Certificate
active
06734141
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of improving the performance of agricultural compositions particularly with respect to rainfastness, run-off properties and efficacy under conditions of low humidity, by using silicone surfactants that reduce the surface tension to less than about 30 mN/m in 0.10% (w/w) aqueous solution thereof without concomitant spreading of the spray solution.
2. Description of the Related Art
Foliar-applied pesticidal and plant growth modifying chemicals are widely used in agricultural, industrial, recreational and residential areas worldwide. These chemical agents illustratively include insecticides, fungicides, herbicides, plant growth regulators and plant nutrients among other chemicals. Such chemicals are typically applied by spraying on the foliage of vegetation to be protected, controlled, killed or modified, but other methods such as rope-wick application are known. Some of these agents show contact action, killing, controlling or modifying the growth of target organisms at the site of deposition. Other chemicals are systemic, translocating within the plant to a site of action remote from the site of deposition. Still other chemicals show both contact and systemic action.
Surfactant formulations are commonly used in forestry, agriculture, and horticulture as agricultural adjuvants to improve the efficacy of agrochemical active ingredients such as micronutrients, growth regulators, biologicals, pesticides such as herbicides, fungicides, insecticides, acaracides and miticides. Surfactants are often used as dispersants, wetting and spreading agents, and emulsifiers in a formulated product or package or in a tank mix. Prior art identifies spreading of spray solution on the weed leaf as an essential criterion for surfactant efficacy. Surfactants have been used to improve herbicide performance since organic herbicides were first developed in the 1940s. Spreading the spray solution on weed leaves has always been a major reason for the inclusion of surfactants. This is clearly expressed in the preface to “Adjuvants for Herbicides” Weed Science Society of America Monograph Series Number 1, 1988, R. H. Hodgson (ed). It includes the statement “Experience shows that successful weed control often depends on the appropriate use of adjuvants in herbicide sprays to ensure uniform application and target coverage”.
Herbicides commonly have been formulated with surfactants. Organosilicone surfactants provide surface tension values significantly lower than other commonly used surfactants. For example, the use of an organosilicone surfactant such as BREAK-THRU® S240, Goldschmidt Chemical Corp., or Silwet® L-77, Crompton Corp., in combination with a pesticide results in increased foliar uptake of the pesticide and, hence, increased efficacy of the pesticide in control of weed growth.
Among the numerous studies of the foliar uptake of the herbicide glyphosate combined with such silicone surfactants are those reported by Field & Bishop in Pesticide Science, 1988, Vol. 24, pp. 55-62; Stevens et al. in Pesticide Science, 1991, Vol. 33, pp. 371-82; Gaskin & Stevens in Pesticide Science. 1993, Vol. 38, pp. 185-92; and Gaskin & Stevens in Pesticide Science, 1993. Vol. 38, pp. 193-200. An extensive review of 160 references relating to the use of organosilicones as adjuvants for agrochemicals was provided by Stevens in Pesticide Science, 1993, Vol. 38, pp. 103-22. It is well recognized in the art that trisiloxane ethoxylate surfactants with no more than about 10 ethylene oxide units have the ability to impart the property of superspreading to agricultural spray mixtures. The term “superspreading” means the ability of a drop of the mixture to spread to a diameter at least 9 times as great as a drop of distilled water on a hydrophobic surface such as the leaf of a plant.
The fact that superspreading has been considered an essential attribute of such silicone surfactants is confirmed by the fact that various patents have been issued with improved spreading as the main objective. For example, U.S. Pat. No. 5,104,647 to Policello and U.S. Pat. No. 5,558,806 to Policello and Murphy have as main objective maintaining the superspreading capability of organosilicone/organic surfactant blends.
U.S. Pat. No. 5,017,216 to Dow Corning discloses postemergent herbicide compositions containing silicone glycol adjuvants, comprising blends of trisiloxane surfactants of the structure Me
3
SiO—SiMeR′—O—SiMe
3
wherein R′ is a short-chain polyether radical with typically 4.6 ethylene oxide units, in combination with siloxane dispersants.
WO 89/12394, WO 99/40785, U.S. Pat. No. 6,051,533, U.S. Pat. No. 6,040,272 and EP 0483095, all to Monsanto, disclose various herbicide compositions comprising silicone surfactants in combination with other adjuvants like humectants, oils, glycol esters and organic cosurfactants. For the silicone surfactants claimed to be useful in these inventions, the inventors disclose a very broad structural range and provide little direction to those skilled in the art about which of these siloxane surfactants are to be advantageously used to enhance the efficacy of herbicide compositions. However, the examples used in these inventions are trisiloxanes like Silwet® L77 or Silwet® 408, having typical structures like Me
3
SiO—SiMeR′—O—SiMe
3
wherein R′ a radical —(CH
2
)
3
—(CH
2
CH
2
O—)
8
—Z wherein Z is hydrogen or methyl. It is well known to a person skilled in the art that trisiloxane surfactants of that type convey superspreading properties to aqueous solutions thereof, as long as the polyether chain length does not exceed about 10 ethylene oxide units. The fact that only such superspreading siloxanes have been chosen to exemplify the invention shows that the inventors were following the common belief that enhanced spreading is an essential attribute for silicone surfactants to be useful as adjuvants in herbicide compositions for most applications.
It is equally well-known to the practitioner of the art that silicone surfactants can have antagonistic effects on the efficacy on herbicides on certain plant species. Gaskin, et al., (Pestic. Sci. 1993, 38, 185-192) demonstrated that some trisiloxane ethoxylates (TSE), such as Silwet® L-77 surfactant (available from Crompton), can antagonize cuticular penetration of a herbicide into grasses, when compared to the herbicide alone. The term antagonism is used to indicate that the treatment of herbicide plus adjuvant is less effective than the comparative herbicide treatment. This tendency to antagonize the activity of glyphosate on some species in the absence of rain can be mitigated by the addition of a humectant such as glycerin to the spray solution, as disclosed in WO 89/12394. This addition prevents rapid drying of the spray solution which commonly is experienced when using superspreading silicone surfactants under conditions of low humidity, such as, for example, a relative humidity of 30% or less.
Gaskin, et al., (Pest. Sci. 1993, 38, 192-200) also studied the antagonism of glyphosate by trisiloxane surfactants with 8 to 40 ethylene oxide units and found that the antagonism is reduced when using surfactants with increased ethylene oxide content. However, no information was provided on rainfastness, and run-off behaviour of the glyphosate compositions, or on efficacy under conditions of low humidity.
It is also common knowledge that surfactants with high content of ethylene oxide groups usually have melting points above common use temperatures and thus are impractical to handle during application. Therefore it is usually desirable to use adjuvants which are liquid at room temperature.
Great Britain Pat. No. 1,255,249 to Dow Corning Corporation, published Dec. 1, 1971, discloses herbicide compositions employing silicone glycol copolymers. Here, general utility of a large number of adjuvants is professed, as exemplified by two generic silicone glycol formulas which embrace structures having both diorganosiloxane units and alkyl-glycol siloxane units.
Humble Geoffrey David
Kennedy Michael Wayne
Simpelkamp Jörg
Clardy S. Mark
Frommer & Lawrence & Haug LLP
Goldschmidt AG
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