METHOD FOR PRODUCTION OF CARBAMIDE-FORMALDEHYDE RESIN Russian patent published in 1996 - IPC

FIELD: production of synthetic polymer materials. SUBSTANCE: solution of carbamide-containing materials is prepared by mixing carbamide with formaldehyde at their molar ratio 1.2-2.0:1.0 or by mixing 11.4-20.0 % of carbamide, 24.9-33.1 % of methylene urea 4.2-9.2 % of dimethylol urea, 1.9-2.4 % of formaldehyde and water. At the first step of condensation thus obtained aqueous solution of carbamide-containing materials is mixed by heating with formaldehyde, the process is carried out till molar ratio of carbamide and formaldehyde is 1.0:1.75-2.1. At the second step condensation thus prepared solution in slightly acid medium followed by cooling and evaporation is carried out. At the third step into thus obtained condensation product additional portion of carbamide or condensation solution is added. The process takes place till molar ratio of carbamide and formaldehyde is 1.0:1.20-1.15. Then additional condensation followed by cooling and by stabilization of resin takes place. EFFECT: improves efficiency of method. 3 cl, 3 tbl