Studying the Effect of Optical Aging by Transitional Elements on Yellowness Property of Newsprint Paper

Metal ions present in chemimechanical pulps lose their brightness upon reaction with lignin of the paper fiber while some of their properties will be increased including yellowness. The objective of this study was to evaluate and determine the amount of variation in yellowness characteristics of chemimechanical papers which were produced in Mazandaran Wood and Paper Company through treatment with some transitional metal ions in addition to relevant techniques to decrease it. Yellowness in pulps produced through mechanical or chemimechanical procedures are desirable due to study their aging content and other brightness parameters related to them as well. Some samples of paper in unbleached mode were prepared from the factory and then, they were treated using two following chemical materials. Firstly, they were wetted using chelating agent of EDTA (Ethylene Diamine Tetraacetic Acid) in various concentration levels. This process will neutralize available ions in samples of CMP (Chemimechanical papers) and the available metal ions which trigger aging and yellowness regimes, will be Neutralized. Secondly, when wetted samples with EDTA are dried, they are wetted again by solutions containing transitional element ions. Results revealed that the most prevalent effect on yellowness improvement was associated with Fe ions while the least considerable one was related to ions of 2 + Al . Al similar to a neutral ion did not show a significant effect on increasing the yellowness. Besides, when 3 3 + + samples are wetted using different EDTA concentrations, there will be a significant decrease in detrimental effects which decrease brightness and increase yellowness contents. In order to improve brightness parameters and prevent unfavorable characteristics such as yellowness, some techniques have been proposed namely methylation [1] and removing yellowness making elements (Kenones) [2].

Hardwood CMP % Transitional metal ions % EDTA % Yellowness % Accelerated optical aging