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

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.

Modification of the Wheat Gluten Network by Kraft Lignin Addition

“…Second, because of the strong hydrogen bond acceptor character of dioxane and its action on the protonation of hydroxyl and carboxyl groups , radicals caught and stabilized by KL could be released in the medium. Indeed, the possibility in adequate circumstances of a transfer of a radical from a lignin phenoxy to a thiol (Figure ) has been previously shown . Radical destabilization would promote an intense protein cross-linking through the formation of iso-peptidic bonds, as indicated by the large size of the protein extracted in the presence of DTE.…”

Review: Light-Induced Yellowing of Lignocellulosic Pulps – Mechanisms and Preventive Methods

“…The stabilizing effect of sulfur-containing compounds decreases over time, and the unpleasant odor is a serious problem that makes these compounds unsuitable for most applications. However, a group of novel non-odorous thiols, isolated from biomaterials or synthesized, have been found to be effective in retarding the discoloration of aspen CTMP (Beyer et al 2006b). The sulfur-containing inhibitors were found to protect the lignin-containing paper for a long time when combined with an ultraviolet absorber and as part of a coating layer.…”