METHOD OF SYNTHESIS UREAFORMALDEHYDE RESIN Russian patent published in 1995 - IPC

FIELD: chemical industry. SUBSTANCE: polycondensation of urea with formaldehyde at their initial and final mole ratio 1:(1.9-2.1) and 1:(1.1-1.6), respectively, is carried out firstly in weak alkaline or neutral medium in the presence of ammonia, then in weak acid medium by dosing catalytic addition to the reaction medium at the stage of condensation in weak acid medium. Addition consists of formaldehyde, sodium hydroxide and sulfuric acid at the mole ratio 1:(0.4-0.5):(0.1-0.3), respectively. Quantity of catalytic addition is 0.27-2.7% of parental formaldehyde used for polycondensation. Catalytic addition ensures to stabilize pH value deviation at the condensation stage in weak acid medium and also quality indices of synthesized ureaformaldehyde resins. EFFECT: improved method of synthesis. 1 tbl