METHOD FOR PRODUCTION OF STABILIZED UREA-FORMALDEHYDE RESIN Russian patent published in 1997 - IPC

FIELD: gluing of woody materials in chemical and wood processing industry. SUBSTANCE: urea-formaldehyde resins are prepared by condensation of urea and formaldehyde in aqueous medium, their molar ratio being 1:1.9-2.1. Initially the process is carried out in acid medium till product having viscosity 75-150 MPa s is prepared, then vacuum drying takes place till coefficient of refraction is 1.438-1.458. The process is followed by adding of diphenylpropane, its quantity being 0.005-0.075 moles per 1 mole of formaldehyde. Thus prepared resin is stabilized within 10-30 min at 65-95 C. Then additional amount of urea is added till molar ratio of urea and formaldehyde is 1:0.95-1.05 and complete condensation takes place. Stabilized resins have decreased content of formaldehyde, namely, 0-0.01 mass %. EFFECT: improved quality of product; decreased amount of supernatant water during production of resin.