Urea-formaldehyde fertilizer preparation, including addition of hexamethylene tetramine and/or tetramethylene diamine to precondensate before final condensation to release ammonia for neutralization in situ

摘要

In the preparation of a urea-formaldehyde fertilizer (I), by adjusting a precondensate (obtained from an aqueous solution of formaldehyde, urea and/or methylol urea, in the form of monomers and low-molecular polymers) to pH less than 4 by adding acid then neutralizing and drying the condensate obtained as reaction product, the precondensate is mixed with hexamethylene tetramine (HMT) and/or tetramethylene diamine (TMD) before addition of acid.