UREA-FORMALDEHYDE RESIN PRODUCTION PROCESS

FIELD: polymer production. ^ SUBSTANCE: invention relates to technology of producing urea-formaldehyde resins appropriate for manufacturing wood particle boards, fiberboards, plywood, and joiner's building parts, and also for joining furniture parts. Urea-formaldehyde resin production process comprises multistage condensation of urea with urea-formaldehyde concentrate in aqueous solution in a medium having variable acidity at specified temperature conditions. Low-alkalinity condensation is carried out at formaldehyde-to-urea molar ratio (1.8-2.2):1 at 20-95°C and pH 7.3-8.6. Condensation solution is then kept for 10-20 min at 99-95°C and acidified to pH 5.0-5.6. Low-alkalinity condensation product is cooled to 83-87°C and acid condensation is carried out to simultaneously achieve relative viscosity of reaction mixture 90 to 189 sec (VZ-3 viscosimeter) and limiting miscibility between 1:6 and 1:3. Formaldehyde-to-urea molar ratio after loading of the second additional urea portion is (1,2-1,45):1 and final molar ratio after loading of the last portion of urea is (1.1-1,3):1. Finished resin is cooled and packaged. Above-mentioned urea-formaldehyde concentrate is a low-methanolic urea-formaldehyde concentrate containing no more than 0.3 wt % methanol. Advantage of the present process consists in that it allows ensuring controllability of the process, reproducibility of technical characteristics of resin, achievement of specified limiting miscibility value, reduced methanol emission, improved sanitary conditions during properties and processing of resin, and production of resin meeting requirements of existing standards. ^ EFFECT: enhanced process efficiency and reduced production expenses due to use of inexpensive low-methanolic urea-formaldehyde concentrate. ^ 2 cl, 3 tbl, 10 ex