| The objective of this project is to determine the mechanisms of retention of fines in a laboratory twin-wire sheet former with polyethylene oxide, the retention aid studied in this project, to model the retention process and to possibly maximize retention of fines on a paper machine. To this end, an apparatus measuring the degree of disentanglement of PEO during preparation and storage was developed. The sensor was designed to measure the loss of pressure of a solution passing through a narrow capillary. A strong correlation between the measurement of pressure drop (or the PEO state of entanglement) and the efficiency of the PEO to retain the fines was also found.; The apparatus used to find this correlation is the laboratory twin-wire sheet former of the Pulp and Paper Research Center of McGill University. The evaluation of the capacity of this former to study retention systems was verified. It was found that the experiments are reproducible and give precise results. This conclusion was obtained by performing mass balances.; Lastly, with the objective of gaining a good knowledge of the fines retention process in paper using polyethylene oxide, a study of the variables which influence this retention was undertaken. An experimental statistical plan was performed on the laboratory twin-wire sheet former while varying the 4 factors most likely to affect the retention of fines in the paper: PEO dosage, PEO/Cofactor ratio, PEO concentration, and time of stirring during PEO preparation. The PEO dosage and the PEO/Cofactor ratio were identified as the two parameters having the most impact on fines retention. Finally, a model linking the 4 parameters was developed. (Abstract shortened by UMI.)... |
