METHOD OF PREPARING CARBAMIDOFORMALDEHYDE RESIN Russian patent published in 2000 - IPC

FIELD: technology of manufacture of carbamidoformaldehyde resins used for making wood boards, plywood, wood-working building products, and for gluing furniture components. SUBSTANCE: described is method of preparing carbamidoformaldehyde resin by condensation of carbamide and carbamidoformaldehyde concentrate in several stages in variable acidity medium during heating operation. Condensation is carried out at carbamide to formaldehyde molar ratio of 1:1.85, reaction mixture is heated to 60-70 C, pH is adjusted to 0.2-8.6 and maintained at 70-75 for 25- 30 minutes and pH is then adjusted with 20% ammonium nitrate solution to 5.2-5.4 and reaction-mixture is maintained at 80-82 C for 25-30 minutes, pH is adjusted to 7.3-7.8. Carbamide is added to attain carbamide to formaldehyde molar ratio of 1:1.2-1.22, and reaction mixture is maintained at 55-60 C for 30-40 minutes and pH is then adjusted to 7.5-8.5 and temperature is lowered to 20C. Invention permits eliminating formaldehyde-contaminated sewage, reducing number of process stages, attaining pH fine adjustment in creating acid medium, using less toxic and deficient stock to prepare resin that meets current standards. EFFECT: more efficient preparation method. 4 ex, 3 tbl