PROCESS FOR THE PREPARATION OF UREA-FORMALDEHYDE CONDENSATES TO BE USED AS FERTILIZERS

摘要

Fertilizers with a slow and controlled release of nitrogen are obtained by condensing urea with formaldehyde in three condensation stages carried out under well-determined conditions of pH, temperature and formaldehyde/urea molar ratio and up to well-determined viscosities of the resulting product. The first stage is carried out in the presence of methanol, the second stage after addition of formic acid and the third stage after neutralization and addition of a further amount of urea. The condensation stages are followed by a terminal heat-treatment at 200-400.degree.C for 0.5 to 5 minutes. The method described allows the control of the struc ture and molecular weight of the condensate, and the obtaining of a condensate having values of IA, Win and HWin ranging from 48 to 58, from 20 to 24 and from 10 to 12, respectively.