ALKALINE PF RESINS LINEAR EXTENSION BY UREA CONDENSATION WITH HYDROXYBENZYLALCOHOL GROUPS

The linear increase of phenol-formaldehyde (PF) resins by reaction und er alkaline conditions of the ortho- and para-hydroxybenzylalcohol gro ups of the PF resin with small molar percentages of urea was followed by model compounds reactions. Apparent rate constants of the reactions of urea with o- and p-hydroxybenzylalcohols were obtained. Both the o rtho- and para-isomerides appeared to react faster with urea than for their autocondensation. The ortho-isomeride appears to react faster wi th urea than the para-isomeride, under alkaline conditions. Autoconden sation under alkaline conditions instead appears to be faster in the c ase of p-hydroxybenzylalcohol. The properties of PF resins prepared wi th the addition of small amounts of urea appear to be consistent with what is observed in the model compounds reactions: Their gel times bec ome faster and viscosity increases with increasing amounts of urea add ition. (C) 1993 John Wiley and Sons, Inc.