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AssigneeCouncil of Scientific and Industrial Research
InventorsParshuram Gajanan Shukla, Swaminathan Sivaram, Natarajan Rajagopalan
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The present invention relates to a process for the preparation of polyurethane microcapsules containing monocrotophos, which comprises of preparing a solution of diol or polyol having a molecular weight in the range of 200-2000, crosslinker, monocrotophos and a catalyst selected from amino or organometallic compounds; dispersing this solution into a dilute solution of stabilizer which consists of a block copolymer having the general formula A!.sub.n -B!.sub.m where A and B are chemically and compositionally dissimilar segments where n and m segments are in between 30-115 and 10-60 units respectively, such that the sum of n and m does not exceed 175 units, in an aliphatic hydrocarbon; adding an isocyanate dropwise to this dispersion; agitating the mixture at 1000-1400 revolutions per minute for the first 6-8 hours and then at 500-800 revolutions per minute for an additional period of 14-18 hours at a temperature between 30.degree. to 40.degree. C. to permit the formation of polyurethane microcapsules; heating the dispersion for an additional period of 1-2 hours at a temperature not exceeding 50.degree. C.; filtering the microcapsules; washing the microcapsules with lower aliphatic hydrocarbon and drying the microspheres under vacuum at temperature between 20.degree. to 35.degree. C.
A process which is conducted in two immiscible non-aqueous phases, for the preparation of polyurethane microcapsules containing monocrotophos which comprises preparing a solution by mixing a diol or a polyol having a molecular weight in the range of 200-2000, with a crosslinker, monocrotophos and a catalyst selected from amino or organometallic compounds;
Dependencies are inferred from the claim text.
No related US applications are recorded in the indexed filing history.
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In coated particulate form: microcapsules or nanocapsules
Having phosphorus-to-oxygen bonds or phosphorus-to-sulfur bonds: containing acyclic or cycloaliphatic radicals
Preservation of bodies of humans or animals or plants or parts thereof
Term ended 30 Mar 2018 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates to a process for the microencapsulation. The invention, particularly, relates to a process for the microencapsulation of a pesticide, especially monocrotophes (dimethyl (E)-1-methyl-2-(methylcarbamoyl) vinyl phosphate). The process involves using polyurethane as a wall material. Microcapsules or the microspheres which are obtained by the process of the present invention range in size from one micron to hundred microns.
Monocrotophos is both a systemic and contact pesticide, useful for a wide range of pests (Monocrotophos, In: The Pesticide Manual, ED. Worthing C. R. and Walker S. B., British Crop Protection Council, 1983, p 384). Pure monocrotophos is a colorless, crystalline material melting at 55.degree. C. Technical monocrotophos having a purity of approximately 78% is semi solid to solid at room temperature. Monocrotophos is freely soluble in water and also in any organic solvents except aliphatic hydrocarbons. It is thermally unstable at temperature greater than 38.degree. C. It decomposes in moist conditions and in the presence of short chain alcohols. It has acute oral lethal dose (LD).sub.50 (rat) 14 mg/kg and acute dermal LD.sub.50 (rat) 336 mg/kg. Technical monocrotophos and its formulations like 40% and 25% solution come under WHO class 1B i.e. `highly hazardous` class. Owing to its highly hazardous nature, there is a great need to encapsulate monocrotophos using a suitable polymer to reduce its oral toxicity. The present invention is, therefore, specifically pertains to a process for the preparation of polyurethane microcapsules containing monocrotophos.
Conventional pesticide formulations are generally available in the form of emulsifiable concentrate for foliar spray, granules for soil broadcast or wettable powder for seed-coat application. These conventional pesticide formulations, have certain drawbacks such as high mammalian toxicity, phytotoxicity and poor persistence due to environmental degradation which leads to its excessive applications. Therefore, a need exists for improving the formulation and application technology for existing pesticides in order to fulfill the needs of both the user and the environment.
This invention is further illustrated by the following examples which should not be construed to limit the scope of the invention.
A solution is prepared by dissolving 0.0052 g diaminobicyclooctane, 1.20 g trimethylolpropane 9.7 g of monocrotophos and 3.0 g of diethylene glycol by heating the mixture at 50.degree. C. for 10 minutes.
The stabilizer (50 mg), namely, a block copolymer of butadiene with ethylene oxide wherein the ratio of number average molecular weight of butadiene segment to ethylene oxide segments is 2.5 is dissolved in 10 g of paraffin oil.