MONOCHROMATIC IRRADIATION OF GLUCOSE-DERIVED CHROMOPHORES ON CELLULOSE PULPS
Ingegerd Forsskåhl1, Henrik Tylli2, Anu Seisto1 and Carola Olkkonen2
1The Finnish Pulp and Paper Institute, Paper Science Centre, P.O.Box 70, FIN-02151 Espoo, Finland
2Department of Chemistry, University of Helsinki, P.O.Box 55, FIN-00014 Helsinki, Finland
A mixture of phenolic and enolic compounds extracted from an heated aqueous alkali solution of glucose and impregnated on pure cellulose behaves very similarly in light-induced reactions as an untreated unbleached high-yield pulp, which is discoloured photochemically. The same mixture of compounds, containing typically phenols, hydroquinones and cyclopentenolones, undergoes different reactions depending on the wavelength distribution of the light source used. Irradiation with monochromatic light at 290 nm causes mainly yellowing, whereas irradiation with light at 360 nm causes an increase in reflectance in the UV region but a decrease in the reflectance (yellowing, discoloration) in the visible region. The study clearly shows that the decrease in reflectance at 370 nm, which is characteristic for the light-induced reaction of high-yield pulps, and often assigned to the lignin part e.g. the coniferaldehyde group, can in fact, instead partly be caused by degradation and rearrangement products of carbohydrates such as glucose.
Keywords: cellulose, glucose, irradiation, carbohydrates, fluorescence spectroscopy, groundwood, high-yield pulp, hydroquinone, monochromatic, UV-visible reflectance spectroscopy