Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Patent
1995-04-05
1997-09-09
Levy, Neil S.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
424405, 424409, 424419, A01N 2512
Patent
active
056653697
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to crop protection formulations which are in solid form, for example powder, granules or tablets.
Crop protection agents are formulated in solid or liquid compositions, usually in the form of a concentrate for ease of handling and transportation, which is diluted with water by the user before application. Often a surface active agent is required to facilitate dilution and is incorporated into the formulation.
Liquid formulations in the form of emulsifiable concentrates contain a very high proportion of organic solvent (often up to 80 percent) which are increasingly coming under scrutiny for their effect on the environment; emulsion concentrates have a higher water content but still contain organic solvents. Suspension concentrates, another water-based liquid form, are often viscous giving rise to handling problems and loss of active ingredient through retention in the packaging.
Solid formulations can also have disadvantages; the more common granules and powders in particular can be difficult to measure but more importantly can be dusty and pose inhalation hazards for the formulator and the user. Tablets have not been used extensively because they are often slow to dissolve. In addition, solid formulations have been found generally to possess a lower biological activity than liquid formulations. Also, with unsophisticated mixing techniques at the site of use, usually in a farmer's field, the tendency of solid forms not to disperse immediately can cause not only clogging of spray equipment with undispersed formulation, but also an inadequate application of active ingredient to the crop to be treated.
Thus there is a need for a fast-dispersing solid crop protection formulation which has better handling characteristics and enhanced biological activity over conventional forms, to satisfy both environmental concerns and provide an effective, product for the farmer to use in an unsophisticated manner in the field.
The Applicants have found that a solid formulation prepared by coextruding a crop protection active ingredient with polyvinylpyrrolidone, and subsequently cooling and milling the extrudate, has an exceptionally fast rate of dispersion in water, and maintains the full biological potential of the crop protection active ingredient. For even greater ease of handling, the granular product may be pressed or compacted into tablet form, or agglomerated into larger granular masses.
Polyvinylpyrrolidone (PVP) has been used extensively in the pharmaceutical industry as a binder or carrier for pharmaceutically active ingredients, especially to assist dissolution and use of sparingly soluble active materials. When used as the base matrix for solid solutions, the conventional preparation method is by solvent evaporation: the active component and PVP are dissolved together in a suitable organic solvent and then the solvent is evaporated off to leave the solid in an amorphous form. The drying stage and the solvent recovery (to avoid contamination of the environment) are difficult and expensive processing steps.
There has been little incentive to utilise PVP in the crop protection industry because the dispersion problems have hitherto been resolved by the use of surface-active/emulsifying agents.
Furthermore there is a prejudice against using PVP at the high temperatures generated by extrusion. Technical Bulletin 2550-006 of GAF (Great Britain) Limited, now known as ISP Europe Ltd, entitled "PVP Polyvinylpyrrolidone-physical, chemical physiological and functional properties" advises that exposure to extreme elevated temperatures should be avoided.
The book entitled "PVP-A Critical Review of the Kinetics and Toxicology of Polyvinylpyrrolidone (Povidone)" by Robinson, Sullivan and Borzelleca also notes:
"Under ordinary conditions, PVP is stable as a solid and in solution. The solid tolerates heating in air for 16 hours at 100.degree. C., but darkening and loss in solubility occurs at 150.degree. C."
Because of the apparent tendency to decomposition, the use of PVP, and related polymers, were
REFERENCES:
patent: 4801460 (1989-01-01), Goertz et al.
patent: 5006595 (1991-04-01), Smith et al.
patent: 5073379 (1991-12-01), Klimesch et al.
patent: 5180587 (1993-01-01), Moore
De Lind Van Wijngaarden Gerhard
Wedlock David John
American Cyanamid Company
Levy Neil S.
Mazzarese Joseph M.
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