Abstract
An increase in moisture during printing can lead to movement of fibres, such as puffing (return of a fibre to its uncollapsed state), twisting, and lifting of fibres out of the paper web. Spruce fibres are especially subject to these movements, contributing to weak bonding and increased surface roughness. The aim of the present study was to treat spruce pulp with enzymes to improve fibre bonding and stability. Spruce chemi-thermo-mechanical pulp was prepared in the laboratory and treated with mannanase, endoglucanase, and with a combination of these enzymes. Strength properties were evaluated before and after wetting of handsheets and their transverse sections were examined by scanning electron microscopy. Handsheet properties before and after rewetting as well as measurement of lumen area of fibres proved to be effective in evaluating fibre movement and puffing. The treatment of pulp with mannanase or endoglucanase improved fibre stability; however, endoglucanase treatment resulted in a loss of strength. Mannanase appeared to modify the cell walls, making them more susceptible to beating and resulting in improved fibre development and inter-fibre bonding. Endoglucanase possibly damaged fibrils, and fibre degradation instead of fibre development occurred during beating. Stability of thin-walled fibres improved more than thick-walled fibres after enzyme treatment.
©2009 by Walter de Gruyter Berlin New York
