METHOD OF CARBAMIDOFORMALDEHYDE RESIN (VARIANTS) Russian patent published in 1998 - IPC

FIELD: chemical industry. SUBSTANCE: carbamidoformaldehyde resins are prepared by three-step condensation of carbamide and formaldehyde, first in alkaline medium at carbamide to formaldehyde molar ratio of 1:1.75-2.1 (first step) and then in acid medium while heating till viscosity of reaction mixture reaches at least 9.5 sq.mm/s at 20 C, followed by cooling, drying and further condensation with additional portion of carbamide in alkaline medium at carbamide to formaldehyde molar ratio of 1:1-2, cooling and stabilization of resin. In cooling stage up to 70 wt % of additional carbamide portion is introduced from third step. Resins have increased adhesiveness, reduced content of formaldehyde and lower toxicity of resin-based wood materials. EFFECT: more efficient preparation method. 3 cl, 2 tbl