ACCELERATION OF THE CURE OF PHENOLIC RESIN ADHESIVES .4. KINETICS OF THE CONDENSATION REACTION OF 2,4,6-TRIMETHYLOLPHENOL

The kinetics of the condensation reaction of 2,4,6-trimethylolphenol (TMP) as a model for phenolic resin was investigated by use of a computer simulation technique. The experimental rates of condensation of TMP in alkaline media were compared with those calculated according to a theory which assumed ten basic reactions going through a S(N)2 mechanism. The analyses revealed the following features of the reaction: 1) the rate constants of the reactions between a dissociated TMP molecule and an un-dissociated TMP molecule are about 6.5 times greater than the corresponding rate constants of the reactions between two un-dissociated TMP molecules and are about 13 times greater than those for the reactions between two dissociated TMP molecules at 110-degrees-C, 2) acceleration of the reaction occurs in the real reaction systems of low alkali/phenol molar ratios as the condensation progresses, and this acceleration can be ascribed to free formaldehyde accumulating in the systems, 3) the rate constants for the formation of para-para methylene bonds are about 3.3 times greater than the corresponding ones for the formation of ortho-para methylene bonds and about ten times greater than those for the formation of ortho-ortho methylene bonds at the temperature of 110-degrees-C.