Identification of recalcitrant stickies and their sources in newsprint production

Deposits from different sections of a newsprint paper mill, using 100% recovered paper, were analyzed following an analytical procedure based on scaning electron microscopy-electron dispersive X-ray and consecutive solvent extraction steps with Fourier-transform infrared spectroscopy (FTIR) analyses of the different fractions. Polyvinyl acetate, polyacrylates, styrene butadiene rubber, and derivatives of fatty acids/resin acids are the main stickies-related components identified in the deposits. The removal efficiency of these contaminants along the deinking line was studied by determining the composition of the dichloromethane extractives in the pulp by FTIR analyses. Although the total stickies content is reduced considerably during the process, some compounds, which are found in the deposits, are not removed selectively in the process, indicating their recalcitrant nature. FTIR analyses of unusable materials coming with the raw material (mainly board and mixed office waste) have demonstrated that these materials are one of the main sources of these types of recalcitrant stickies.