Brightness stabilisation of bleached high-yield pulps by novel sulfur-containing inhibitors

Abstract

Abstract The stabilisation of a peroxide-bleached chemothermomechanical pulp against light-induced yellowing by novel sulfur-containing radical-scavenging compounds was investigated. Substances were identified that lack the unpleasant odour typical for compounds containing thiol groups. High inhibition effects were observed when the sulfur compounds were combined with small amounts of hindered amines and UV absorbers. A novel group of thiols isolated from biomatter was among the sulfur-containing inhibitors. Photoyellowing could be avoided for 3 years in real conditions when the inhibitors were applied as part of a coating. The ability of the thiol compounds to scavenge phenoxy radicals was demonstrated by ESR spectroscopy of irradiated chemithermomechanical pulp sheets. The results are encouraging for efficient brightness stabilisation of high-yield pulps.