METHOD OF SYNTHESIS OF CARBAMIDOFORMALDEHYDE RESIN Russian patent published in 1997 - IPC

FIELD: chemical technology. SUBSTANCE: carbamidoformaldehyde resin is synthesized by step-by-step condensation of carbamide and formaldehyde aqueous solution in media at variable acidity, at heating, in the presence of modifying agent - sodium chloride waste of polyethylenepolyamines production. Waste has 90% sodium chloride, polyethylenepolyamines chlorohydrate (5-7%), mineral impurities and water. Waste is used at amount 2-10% of carbamide mass the first portion. The first stage of condensation is carried out at pH = 7.0-9.2, at 92-98 C and mole ratio carbamide and formaldehyde = 1:2. The second stage - at pH = 4.0-5.0, at 92-98 C followed by neutralization, drying and cooling the obtained reaction mass. Then the additional carbamide portion is added and additional polycondensation is carried out at pH = 7.0-7.5, at 58-62 C followed by resin cooling and stabilization. Alkaline agent: alkaline metal or ammonium hydroxide aqueous solutions; acid agent: solutions of ammonium chloride, benzenesulfoacid or sulfuric acid. Synthesized modified resins exhibit decreased toxicity, content of formaldehyde is 0.04-0.2%. EFFECT: improved method of synthesis, improved quality and safety, decreased net cost. 7 cl, 2 tbl