Brightness reversion of mechanical pulps XI: Photostabilization of high-yield pulps by thiosulfinates

A series of eleven cyclic and acyclic thiosulfinates was synthesized and ap plied onto hardwood BCTMP (bleached chemithermomechanical pulp) testsheets. Treated and untreated testsheets were photoaged and their optical property were monitored. The results of these photoaging experiments indicated that cycle thiosulfinates were relatively ineffective at retarding brightness r eversion, whereas most acyclic additives were effective photostabilization agents for BCTMP. The use of acyclic thiosulfinates in combination with UV absorbers provided a very effective means of retarding the photoaging proce ss of mechanical pulps.