Plant protecting and regulating compositions – Plant growth regulating compositions – Designated nonactive ingredient containing
Reexamination Certificate
1999-09-03
2001-05-08
Clardy, S. Mark (Department: 1616)
Plant protecting and regulating compositions
Plant growth regulating compositions
Designated nonactive ingredient containing
C504S367000, C514S944000, C514S947000, C424S409000
Reexamination Certificate
active
06228811
ABSTRACT:
This invention relates to a solid or structured gel formulation and in particular to a solid or structured gel formulation of a water-soluble or water-dispersible material suitable for aqueous spray application after dispersion or dissolution in water. The invention further relates to a method of reducing sludge formation in the course of spraying a solution or dispersion of a water-soluble or water-dispersible solid or structured gel formulation.
Floating granules are known and used for example in paddy water treatments to provide a slow dispersion of material over a passage of time. Such granules are applied directly to the paddy field, as opposed to being tank mixed, and in consequence do not give rise to sludge problems.
In Zasso Kenkyu (1995), 40 (2), 80-6 there is disclosed a study of a naproanilide formulation taking the form of a wettable powder housed in a water-soluble bag and containing hollow glass floating carrier particles. The water-soluble bag containing the formulation is intended for direct application to paddy water. It was concluded that when the concentration of the carrier was high, the formulation floated on the water surface until the wettable powder completely diffused into water and the amount of naproanilide released from the formulation into water was large. If the concentration of the carrier was low, the entire body of the formulation sank soon after the film dissolved in water resulting in low release of naproanilide. In tests of biological activity it was concluded that a wettable powder packed in a water soluble film containing 20% floating carrier has potential as a formulation which could reduce the labour of herbicide application in paddy fields but that when the carrier content was less than 14%, little amount of naproanilide diffused in the water and the herbicidal efficacy was extremely low.
The present invention is applicable to any solid or structured gel formulation suitable for aqueous spray application after tank mix dispersion or dissolution. Whilst the present invention is not restricted to any one particular field, such solid or structured gel formulations are typically used for aqueous sprays in agriculture, public health and animal health. Thus the active ingredient may for example be a herbicide, insecticide, nematocide, fungicide or plant growth regulator. Alternatively the granule may be used to carry an auxiliary agent such as a wetter or other adjuvant.
Active ingredients or auxiliary agents suitable for application by means of an aqueous spray may be formulated in a wide variety of ways. The present invention relates to solid water-soluble or water-dispersible formulations such as granule formulations (sometimes also referred to as water-soluble or water-dispersible grain formulations or wettable granules). The present invention is not however limited to granule formulations its advantages may also be apparent in other forms of solid formulation such as “cast tapes” (as described for example in International application No 96/02947 and in GB 2095558), flakes, wettable powders or tablets. The present invention also relates to structured gel formulations, for example structured gel formulations suitable for incorporation in a water-soluble bag and containing solid water-dispersible material.
Such solid or structured gel formulations (and in particular structured gel formulations when housed in a water-soluble bag) have a number of advantages as compared with liquid formulations. Such advantages include for example reduced transport costs, reduced operator exposure and reduced residue contamination of containers. A solid formulation or water-soluble bag containing a structured gel formulation may reduce residue formation to the extent that the use of a disposable container is acceptable.
A wettable, dispersible or water-soluble solid or structured gel formulation normally consists of an agrochemical or other ingredient suitable for application by aqueous spray incorporated with a solid inert filler which may be water-soluble or water-dispersible. The agrochemical or other ingredient may be a solid or liquid and may be water-soluble or water-dispersible. Auxiliary agents such as surfactants, activity enhancers, anti-foams and stabilisers are frequently used and may be incorporated in the same solid or structured gel formulation with the active ingredient or may be formulated separately or may be added at the tank mix stage.
Solid or structured gel formulations such as granules may be formed by a variety of techniques, including for example pan granulation, spray drying, agglomeration and extrusion. Techniques for providing solid “cast tapes” are illustrated in GB 2095558 and in our International application No 96/02947. Techniques for providing structured gel formulations are illustrated for example in WO 96/03871.
In use, the solid or structured gel formulation is added to water to form a solution or dispersion which is then applied as a spray, for example as a spray application to plants. In agrochemical use for example, the solid or structured gel formulation is typically mixed immediately prior to spraying with water in a tank containing from about 20 liters for a knapsack sprayer to about 100 to 2000 liters of water for a commercial spray tank. The structured gel formulation may conveniently be housed in a water-soluble bag prior to addition to water. Solid formulations are more normally added directly to the water but may also be housed in a water-soluble bag if desired. Whilst such spray tanks are generally provided with some means of agitation, such as mechanical stirring or pumped circulation of the water, the degree of mixing within the tank may be relatively inefficient or the solid or structured gel formulation itself may be inherently difficult to disperse, particularly for example if the formulation has been allowed to age. In particular there may be specific zones within the tank (“dead zones”) in which the level of agitation is especially poor. In practice therefore effective dispersion of insoluble or partially or slowly soluble materials may not be achieved and an insoluble solid sludge may build up in such dead zones within the tank during the time-scale of spray application. Once a sludge is allowed to start to build up, it may become compacted and much harder to re-disperse, even with the application of effective agitation. Even if the sludge is re-dispersed, it may still form relatively large agglomerates of particles which may tend to block the spray nozzles or filters. Furthermore, the formation of a sludge represents a removal of active material from the aqueous phase leaving the spray nozzle. Thus even if the sludge is eventually dispersed and leaves no residue, the concentration of active material in the spray will be less in the initial stages than in the later stages when the sludge is beginning to break up and pass through the nozzle. Sludge formation can therefore lead to uneven distribution of the active ingredient in the spray and poor biological utilisation of active material. Sludge left in the spray tank after spraying is completed may cause contamination and disposal problems. In general the formation of sludge in the spray tank is a well-recognised problem which may be associated with the use of solid or structured gel formulations. One solution to this problem would of course be to provide more efficient agitation within the mixing tank but the cost involved makes this unattractive and a solid or structured gel formulation having reduced sludge formation in conventional spray tanks is to be preferred.
We have now found that the problem of sludge formation may be mitigated if the density of the solid or structured gel formulation is reduced by the incorporation therein of a solid particle hang a density of less than one. Since the solid particle should not block the nozzle it should have a diameter less than that of the spray nozzle. Furthermore since in use the spray nozzle is generally protected from blockage by a suitable filter, the particle should preferably have a diameter of less t
Clardy S. Mark
Savitsky Thomas R.
Zeneca Limited
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