Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Patent
1997-12-18
2000-02-08
Levy, Neil S.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
424409, 424410, 424412, 424489, A01N 2508
Patent
active
060225521
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to blends of pesticidal granules in various cylindrical shapes that are nonsegregating.
Pesticidal granules that are water-dispersible granules disintegrate in spray tank water to form a fine dispersion of primary particles, which then can be applied to crops by spraying. Pesticidal granules can also be totally water soluble. Pesticidal granules can also be applied dry.
In agriculture, more than one pesticide is often needed to treat a particular crop. In such a case, granules can be prepared which contain a combination of pesticides or alternatively separate granules prepared for each pesticide. It is desirable to apply a combination of pesticides simultaneously in one pass when spraying crops rather than making separate passes over the field with each pesticide.
In the use of two or more water dispersible granules each granule is added to the same spray tank whereupon they disintegrate and become homogeneous in water which can be sprayed on to the crop. However, adding individual pesticides to the spray tank is not entirely satisfactory because it is inconvenient to have to measure out separate products and there is increased risk of mismeasurement. A single product containing all the necessary pesticides is preferred.
Pesticide mixture products in which each granule contains more than one pesticide are commercially available. However, for various markets, the pesticides are needed in different combinations and ratios. This proliferates the number of products and leads to complicated manufacturing and stockage issues. It would be advantageous to produce pesticide granules with a single active ingredient which can be combined with a different granular pesticide to form a mixture of granules in the desired ratio as a physical mixture before addition to a spray tank.
Physical mixtures of individual granules of mismatched sizes present a risk of segregation and therefore misapplication when dispensed in part. One solution to the segregation problem as regards water dispersible granules is to package the mixture as a "unit pack" where the entire content of the package is used in the spray tank. An example of a unit pack is a water-soluble bag which is simply tossed into a spray tank full of water whereupon the bag dissolves releasing the contents. Another example of a unit package is a bottle containing only one dose.
Although the unit package is one method to address the problems associated with granule mixtures, such a package lacks flexibility in dosage as the entire contents of the package must be emptied at once.
Most water dispersible granules currently produced are "isodimensional", meaning they are approximately spherical and are produced by granulation methods such as fluid bed, pan or disc, high shear, spray drying and the like, and also paste extrusion wherein the extrudate is post treated to give an isodimensional shape (e.g., WO 89/00079). Granules produced by these methods tend to have a high variability in granule size distribution but can be sized by sieving. To maximize productivity, the product size range is as broad as possible and granules outside the desired product size distribution can be recycled or reworked. Even with the same process equipment, there tends to be batch to batch and product to product variations in size distribution of granules.
It has been suggested in FR 2,704387 that to obtain a nonsegregating mixture of granules, the ratio of median diameters of two categories of granules must be 10 or less. The normal product size distribution of the disclosed granulation techniques typically fall within that range. However, to achieve the preferred ratio of 2 or less, extensive post production separation of the granules is required. Data shows that even when the diameter ratio is less than 2, significant inhomogeneity can result from size segregation. It would be advantageous for a normal product size distribution to be suitable for adnixture into nonsegregating mixtures without further size separation.
SUMMARY OF THE I
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Brown Philip Alexander
Pugh Luann Marshall
E. I. Du Pont de Nemours and Company
Levy Neil S.
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