Improving recyclability of chemical pulp by introducing non-charged cross-linked polysaccharide on fiber surface

The effect of spray application of xyloglucan on strength and recyclability of bleached chemical pulp was studied. Xyloglucan alone and with a cross-linking chemical was applied on sheets made of unbeaten never-dried and once-dried virgin pulps. Recyclability of these pulps was evaluated based on the tensile strength of wet and dry handsheets. Dry strength measurements showed that the spray application reduces the loss of strength and bonding ability in recycling. The use of cross-linking chemical was found to be essential in enhancing both the wet and dry strength of the virgin and recycled pulps. The chemical application was efficient with both never-dried and once-dried pulps. Wet web strength results indicate that the amount of web breaks could be decreased in paper and board machines using recovered fibers by having cross-linked xyloglucan layer on fiber surface. Spray application was found to be an effective way to introduce non-charged chemicals into fiber network. As a consequence of improved fiber bonding the need of refining decreases which further improves the recyclability of fibers. In addition to xyloglucan also other polysaccharides, for example those provided by chemical or mechanical pulp mills, could be used for improving the recyclability and extending the lifetime of fiber material.