Solns. of melamine-urea-formaldehyde resins - with low viscosity are prepd. partic. for decorative laminate prodn.

摘要

The resin solns. (I) are prepd. by (1) adjusting pH of HCHO soln. contg. 5-11.5 wt.% MeOH with triethanolamine (II), NaOH or NH4OH to 7.5-8.1; (2) adding NaOH to pH 8.7-10, partic. 8.7-9.3; (3) adding melamine and urea in molar ratio 1:1.3-2 at below 50, pref. at 35-45 deg.C. such that molar ratio amino cpds. to HCHO is 1:1.5-1.9; (4) condensing at 90-100 deg.C. to water tolerance 1:1-2, whereby pH in first 15-25 minutes of condensation, adjusted to 9.3-8.7 by stepwise or continuous addn. of NaOH, falls to 8.2-8.0 and condensation is finished at pH 8.0-7.5. USE/ADVANTAGE - Impregnation of paper sheets in mfr. of decorative and technical laminates, including laminates with postforming properties by adding 1-5% glycol to impregnating soln., and for coating surfaces. (I) are low mol., low viscosity, and reactive, and are obtd. in short reaction times, method is economical, laminates have high eleasticity and water resistance.