ATTEMPTS TO PHOTOSTABILIZE PAPER MADE FROM HIGH-YIELD PULP BY APPLICATION OF UV SCREENS CONTAINING GROUPS TO AID THEIR COMPATIBILITY WITH CELLULOSE AND LIGNIN

2,4-dihydroxybenzophenone (DHB) is known to be a reasonably efficient UV screen for preventing the colour reversion of papers made from high-yield pulps. Attempts have been made to improve the performance of this material by increasing its compatibility with cellulose and by the introduction of cationic groups which will help it to locate in lignin-rich areas. The latter has proved successful and the results show that, on a molar basis for the 2,4-dihydroxybenzophenone nucleus, the efficiency is increased by the introduction of ammonium and thiouronium groups. An interesting finding was that a 2,4-dialkyloxyderivative of benzophenone showed similar protective power to that observed for DHB.