CHEMISTRY OF NOVOLAC RESINS .2. REACTION OF MODEL PHENOLS WITH HEXAMETHYLENETETRAMINE

It is proposed that the reactions of hexamethylenetetramine (HMTA) wit h 2,4-xylenol and with 2,6-xylenol occur by different pathways. The ra te of reaction and the final product distribution depend on the initia l xylenol : HMTA ratio and are different in the two systems. Measured by HMTA consumption, with 2,4-xylenol the reaction rate increased with increasing xylenol : HMTA ratios, whereas with 2,6-xylenol the rate o f reaction decreased with increasing 2,6-xylenol : HMTA ratio. In syst ems which contain both 2,4- and 2,6-xylenol, a strong preference for r eaction of the HMTA with the ortho site of 2,4-xylenol was noted. This preference was apparent even in mixtures in which 2,6-xylenol was pre sent in greater amounts than 2,4-xylenol. (C) 1997 John Wiley & Sons, Inc.