Importance

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Abstract

An attrition resistant controlled release fertilizer comprising: NH.sub.2 -containing water soluble central particles such as urea, surrounded and chemically bonded with a base coating, consisting of substituted ureas, formed by reacting a molecular excess of polyfunctional isocyanate with the NH.sub.2 groups of the central particles, and a water insoluble layer, surrounding and chemically bonded with the base coating, formed by the reaction and polymerization of the excess isocyanate with anhydrous organic polyols. If desired, 1 to 10 water insoluble coatings may surround the sealing layer. The base coating's substituted ureas may be effectively formed with diphenylmethane diisocyanate and the sealing layer, with polyethyleneterephthalate polyester polyols containing triethanolamine or melamine catalyst. Central particles effectively coated include: urea, biuret, ureaform, guanidine, melamine, and ammonium salts. A preparation method is provided.

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First Claim