Chromophores in lignin-free cellulosic materials belong to three compound classes. Chromophores in cellulosics, XII

Authors: KORNTNER, PHILIPP - University Of Natural Resources & Applied Life Sciences - Austria; HOSOYA, TAKASHI - University Of Natural Resources & Applied Life Sciences - Austria; DIETZ, THOMAS - Evonik Degussa Gmbh; EIBINGER, KLAUS - Zellstoff Pöls Ag; REITER, HEIDEMARIE - Mondi Uncoated Fine & Kraft Paper Gmbh; SPITZBART, MARTIN - Mondi Uncoated Fine & Kraft Paper Gmbh; RODER, THOMAS - Lenzing Ag; KREINER, WOLFGANG - Sappi Papier Holding Gmbh; KAI MAKLER, ARNULF - Sappi Papier Holding Gmbh; WINTER, HERIBERT - Sappi Papier Holding Gmbh; GROISS, YVONNE - Austropapier, Özepa; FU, A - South China University Of Technology; WONG, A - South China University Of Technology; FRENCH, ALFRED - Retired ARS Employee; HENNINGS, UTE - University Of Natural Resources & Applied Life Sciences - Austria; POTTHAST, ANTJE - University Of Natural Resources & Applied Life Sciences - Austria; ROSENAU, THOMAS - University Of Natural Resources & Applied Life Sciences - Austria

Submitted to: Cellulose
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary: Items made from cellulose such as cotton fabric and paper turn yellow as they get older. Sometimes, the yellow color develops more rapidly than other times, sometimes even before the cotton fibers or wood pulp are turned into finished products. The yellowing is bad on its own, but it is even worse because it is often accompanied by loss of strength of the material. The research described in this paper addresses the chromophores, the specific molecules that cause the color of aged cellulose. Although there are numerous such molecules, all at very low concentrations, there are three main types of molecules, with each type represented by a single molecule. Therefore, efforts to study the development and removal of color can concentrate on just three molecules. This research should be of interest to scientists studying bleaching and the development of color in cellulosic materials, including cotton fiber and fabric.

Technical Abstract: The CRI (chromophore release and identification) method isolates well-defined chromophoric substances from different cellulosic matrices, such as highly bleached pulps, cotton linters, bacterial cellulose, viscose or lyocell fibers, and cellulose acetates. The chromophores are present only in extremely low (ppm to ppb) concentrations. The concept of primary and secondary chromophores is introduced, with primary chromophores arising only from the polysaccharides inherent to cellulosic materials. Secondary chromophores also include atoms from the chemicals used to process the cellulose. Most primary chromophores belong to one of three compound classes: hydroxy-[1,4]-benzoquinones, hydroxy-[1,4]-naphthoquinones, and hydroxyacetophenones. Among them, three individual compounds dominate: 2,5-dihydroxy-[1,4]-benzoquinone, 5,8-hydroxy-[1,4]-naphthoquinone, and 2,5-dihydroxyacetophenones, amounting to more than 80% of the total isolated chromophores in most cases. In lignin-free cellulosics, these three compounds can thus be regarded as key chromophores. The prevalence of these molecules is due to both exceptionally strong resonance stabilization, as reflected in delocalized double bonds, and their ready reformation from carbohydrate degradation products by recondensation reactions. The findings that a) most chromophores in lignin-free cellulosic materials belong to only three compound classes and that b) three chromophore compounds make up the bulk of the chromophore mixtures are foundational for future bleaching research: Based on this knowledge, specific searches for optimized bleaching conditions can now concentrate on these compounds and still cover the vast majority of chromophores.