METHOD OF PRODUCING UREA FORMALDEHYDE RESIN Russian patent published in 2015 - IPC C08G12/12 C08G12/40 

FIELD: chemistry.

SUBSTANCE: method is carried out in multiple steps in a medium with variable acidity. The method comprises weakly alkaline condensation of carbamide and carbamide-formaldehyde concentrate in an aqueous solution at 20-95°C and pH 7.2-9.2, wherein molar ratio of formaldehyde to carbamide is (1.8-2.2):1; holding the condensation solution for 10-20 minutes at 85-99°C; acidifying the condensation solution to pH 4.7-5.5 with aqueous glyoxal solution with concentration of basic substance of not more than 50 wt % in amount of 1-20% with respect to formaldehyde. Further, polycondensation of the reaction mass is carried out in an acidic medium, followed by neutralisation to pH 7.5-8.5 and simultaneous cooling to 70-75°C. Pre-condensation of the reaction mass is carried out with additional supply of carbamide to the final molar ratio of formaldehyde to carbamide of (1.0-1.25):1. The finished resin is cooled and packed.

EFFECT: invention reduces content of free formaldehyde in the finished urea formaldehyde resin and wood chipboard based thereon.

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