UREA-FORMALDEHYDEHYDE RESIN PRODUCTION PROCESS Russian patent published in 2001 - IPC

FIELD: polymer production. SUBSTANCE: invention relates to large-scale production of urea-formaldehyde resins, including modified ones, and can be used at potassium industry enterprises, for example at flotation plants where resins are used as depressants. Urea-formaldehyde resins are prepared by stepped ureaformaldehyde condensation in variable- acidity media (first in alkaline medium and then in acidic medium) at heating in presence of modifying agent containing polyethylenepolyamine in acidic condensation step and with extra urea added in alkaline condensation step. According to invention, 40-45% polyethylenepolyamine solution in 20% sulfuric acid is used as modifying agent in amounts 25% of the weight of carbamide involved in condensation process. Initial and final urea-to- formaldehyde molar ratios are 1: (2.2- 2.35) and 1:(2.0-2.2), respectively. Alkaline condensation is carried out at pH 8.5-9.1 and 74-78 C for 30 min, and acidic condensation at pH 4.2-6.1 and 70-80 C. EFFECT: reduced toxicity of resins at lower cost. 1 tbl, 5 ex