THE CHEMISTRY OF NOVOLAC RESINS - PART-8 - REACTIONS OF PARA-HYDROXYBENZYLAMINES WITH MODEL PHENOLS

The reactions of 2,4-xylenol and 2,6-xylenol, with bis- and tris(4-hyd roxy-3,5-dimethylbenzyl)amines derived from the reaction of 2,6-xyleno l with hexamethylenetetramine (HMTA) were studied as models for the cu ring of novolac resins. The structural changes during the process were examined by C-13 and N-15 n.m.r. spectroscopy. The results indicate t hat reactions between bis- and tris(4-hydroxy-3,5-dimethylbenzyl)amine s and 2,4-xylenol (containing an ortho reactive sites) produce para-pa ra, ortho-para, and ortho-ortho methylene linkages between phenolic ri ngs via a number of reaction pathways. Heating bis- and tris(4-hydroxy -3,5-dimethylbenzyl)amines with 2,6-xylenol only produces para-para me thylene linkages, but the reactions occur at relatively low temperatur es compared to those of the thermal decomposition of the bis- and tris (4-hydroxy-3,5-dimethylbenzyl)amines. Numerous side-products were obse rved during the process, but most of these can be further reacted or o xidised to form methylene linkages, and only minor amounts remain afte r heating to 205 degrees C. Reaction mechanisms and possible reaction pathways are postulated based on structural changes. (C) 1998 Elsevier Science Ltd. All rights reserved.