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Using recycled fiber as part of the stuff for papermaking has been a necessity. The application of recycled fiber, however, would affect the final strength properties of the products due to the drying and rewetting of the fibers. Starch, especially cationic starch was thus used to mitigate the defect. The objectives of this study are to evaluate the effect of the cationic starch dosage and the adoption of recycled mixed office waste (MOW) fiber on the retention and handsheet properties in the currently mainstreamed neutral papermaking system.
The results showed that the size fastness increased with increasing AKD and cationic starch dosages no matter MOW fibers were added or not. The cationic potato starch showed better size fastness than that of cationic tapioca starch. The size fastness was controlled by AKD and cationic starch dosage, and decreased with increasing charge of MOW pulp.
The strength of MOW recycled fiber was improved by an appropriate beating to a CSF of 280ml. The burst and tensile indices of the handsheet were improved with the addition of cationic starch. The strength of handsheet increased with the increasing application of MOW recycled fiber mainly due to its better fiber length distribution than that of the LBKP’s.
The overall first pass retention and first pass fines retention were more than 97% and 90% respectively, with the addition of cationic potato starch. The figures were 90% and 70% respectively for the laboratory modified cationic tapioca starch. The first pass retention decreased with increasing cationic starch dosage, due to over cationic demand. The specific charge density of the stock changed sensitively with the addition of potato starch. The ultimate potential of the stock reached to a near isoelectric point after all the designed additives were applied, showing that the sequence of addition is applicable in the neutral papermaking system.
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