METHOD FOR PRODUCING UREA-FORMALDEHYDE RESINS Russian patent published in 2024 - IPC C08G12/12 

FIELD: urea-formaldehyde resins.

SUBSTANCE: invention relates to a method for the production of urea-formaldehyde resins intended for use in the woodworking industry, mainly in the production of plywood products and can be used in both the chemical and woodworking industries. The method consists in producing urea-formaldehyde resins by polycondensation of urea with formaldehyde in an environment with variable acidity, first in slightly alkaline or neutral, and then in acidic and slightly acidic environments when heated with the introduction of an additional portion of urea at the initial and final ratio of urea and formaldehyde 1: 1.9-2 .15 and 1:1.05-1.25 in mols, respectively, while in order to maintain the high wet stickiness of the finished resin with a low content of total formaldehyde, an additional portion of urea is introduced in two doses, first a part of the additional portion of urea is introduced to the ratio of urea to formaldehyde 1 to 1.50-1.70 in moles and continue the process at a temperature of 65-80°C and pH of the reaction medium in the range of 6.20-6.90 for 30-60 minutes, then the residual part of additional urea is introduced and the synthesis is continued at a temperature of 55-65°C and pH of the reaction medium are in the range of 7.50-8.50 for 35-45 minutes, and 5-10 minutes before the completion of the synthesis, ammonia water is introduced in an amount of 0.01-0.02 mol per mol of urea.

EFFECT: method for producing urea-formaldehyde resins, which allows minimizing the content of free formaldehyde in the finished resin without reducing its wet stickiness.

1 cl, 1 tbl, 11 ex