| abstract |
The invention relates to a coated granular fertilizernhaving a film covering fertilizer granules. This film comprisesna polyurethane resin prepared by a method comprising the stepsnof (a) reacting an aromatic polyisocyanate with a first polyolncomponent (i.e., castor oil or a castor oil derivative), thereby tonobtain a prepolymer having terminal isocyanate groups in thenmolecule; and (b) reacting the prepolymer with a second polyolncomponent (i.e., castor oil or a castor oil derivative) and a thirdnpolyol component which is an amine having at least twonhydroxyl groups in the molecule, thereby to cure the prepolymernand thus to prepare the polyurethane resin. The inventionnrelates to another coated granular fertilizer having a filmncovering fertilizer granules. This film comprises a urethanenresin and aqueous-fluid-absorbing particles having a particlendiameter of from 1 to 200 µm. This urethane resin may be thenabove polyurethane resin. This coated granular fertilizer cannbe produced by a method comprising the steps of (a) applying annaromatic polyisocyanate, a polyol component (i.e., castor oil or ancastor oil derivative), an amine, and the aqueous-fluid-absorbingnparticles, at the same time or separately in no specialnorder, while the fertilizer granules are kept fluidized or rolled,nthereby to form a precursory film on the fertilizer granules; andn(b) curing the precursory film into the film. Each coatedngranular fertilizer is substantially superior in regulation of thenrelease of plant nutrient elements therefrom. |