PROCESS FOR PREPARING CARBAMIDE-FORMALDEHYDE RESIN Russian patent published in 1997 - IPC

FIELD: wood-working industry, more particularly preparation of low-toxic resins having high dry residue content and higher stability. SUBSTANCE: carbamide- formaldehyde resin is produced by preparing condensation carbamide containing solution followed by condensation thereof in three stages. Condensate is prepared by mixing carbide-containing compounds (carbamide or carbamide-formaldehyde condensate prepared by mixing carbamide and aqueous formaldehyde in alkaline medium at molar ratio of 0.8-2.0:1) and aqueous formaldehyde solution till carbamide to formaldehyde molar ratio of 1.0: 1.7-2.2 is achieved. First condensation stage is carried out at pH of 6.5-9.0, 80-98 C for 30-60 min. Second stage is carried out in alkaline medium at pH of 3.9-5.0, 88-96 C till desired viscosity is attained and mono- or polyhydric alcohols are added in amount of 0.01- 0.2% by weight of monomers. Third condensation stage is carried out by addition of carbamide at carbamide to formaldehyde molar ratio of 1.0:0.95-1.3 at 40-65 C and pH of 7.0-8.5 on completion of drying operation carried out after second condensation stage and cooling of the reaction mixture to 60-85 C in vacuum. EFFECT: improved properties of the carbamide-formaldehyde resin. 10 cl, 2 tbl