INDUCED ACCELERATED AUTOCONDENSATION OF POLYFLAVONOID TANNINS FOR PHENOLIC POLYCONDENSATES .2. CELLULOSE EFFECT AND APPLICATION

Polyflavonoid tannin autocondensation was found to be facilitated by t he reaction occurring on cellulose and lignocellulosic substrates. Alt hough the mechanism of polyflavonoid autocondensation induced by cellu lose differs from that induced by the action of Lewis acids, the subse quent reaction of autocondensation appears to be similar. The determin ing step of tannin rearrangement pathways under alkaline conditions in cellulose-induced higher-temperature autocondensation is the favoring of the heterocycle pyran ring opening over the normal interflavonoid bond cleavage and catechinic acid rearrangement. This is caused by rel evant bond weakening and easier cleavage induced by strong attractive forces between flavonoid and cellulosic substrate. Applied bonding of cellulosic substrates by polyflavonoid tannin autocondensation reactio ns appears to be feasible and to occur as predicted from theoretical p redictions. (C) 1995 John Wiley and Sons, Inc.