The main objective of this study was to evaluate and determine the variation in brightness characteristics of chemimechanical papers, which were produced by Mazandaran Wood and Paper Company through treatment with some transitional metal ions in addition to relevant techniques to decrease it. The existing metal ions in chemi-mechanical pulps lose their brightness upon reaction of the paper fiber with lignin. Although some of their properties will be increased, including yellowness, the brightness of the pulps produced through mechanical or chemi-mechanical procedures are preferred according to investigations on the aging degree and other relevant brightness parameters. Some unbleached samples of paper were prepared at the factory and then, they were treated using following two chemical materials. Firstly, they were wetted using EDTA (Ethylene Diamine Tetraacetic Acid) as chelating agent, at various levels of concentration. The process neutralized available ions in the samples of CMP (chemi-mechanical papers) and also the existing metal ions, which can trigger aging and yellowness regimes. Secondly, after EDTA-wetted samples were dried, they were wetted again by solutions containing transitional element ions. The obtained results revealed that the most prevalent effect on brightness improvement was associated with Fe2+ ions, while the least considerable one was related to ions of Al3+. Similar to a neutral ion, Al3+ did not show a significant effect on decreasing the brightness. Besides, when the samples were wetted using different concentrations of EDTA, a significant decrease occurred in detrimental effects, reducing the brightness and increasing the yellowness degrees.
کلید واژگان :accelerated optical aging, brightness, EDTA, hardwood CMP, transitional metal ions
ارزش ریالی : 600000 ریال
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