SYMMETRICAL POLYUREA-URETHANE FERTILIZER ENCAPSULATION

摘要

This invention relates to processes for the production of symmetrical polyurea-urethane coated granular fertilizer products, and to the symmetrical polyurea-urethane coated granular fertilizer products produced by these processes. These processes comprise coating fertilizer granules with compounds which react to form urethane coatings which contain terminal isocyanate groups, followed by polymerization of these urethanes to form symmetrical polyurea-urethanes. Suitable compounds comprise a) an organic polyisocyanate component, and b) an alkanol-amine component containing at least one tertiary amine group and at least one hydroxyl group. These compounds are present in sufficient quantities that the molar ratio of isocyanate groups to isocyanate-reactive groups is from about 1.6:1.0 up to about 10.0:1.0 in each encapsulating layer. It is necessary that sufficient amounts of these compounds are applied to the fertilizer granules such that the symmetrical polyurea-urethane coated granular fertilizer particles contain from about 0.5 to about 15% by weight of polyurea-urethane, based on the total weight of the encapsulated fertilizer particles.