| 摘要 |
PROBLEM TO BE SOLVED: To provide a manufacturing method for an ultra-slow-acting nitrogen fertilizer of urea-formaldehyde condensates whose elution ratio into hot water can be adjusted to a desired one and whose decomposition characteristics are excellent. SOLUTION: In the manufacturing method for the nitrogen fertilizer, urea (U) and formaldehyde (F) are subjected to a methylolation reaction in an aqueous medium at >=70 deg.C in the presence of an alkaline catalyst and then a reaction solution resultant from the methylolation reaction is subjected to a methylenation reaction by adding a strong acid thereto. The nitrogen fertilizer has the elution ratio into hot water of <=15 mass% (on the anhydride basis).
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