Pectinase in papermaking: solving retention problems in mechanical pulps bleached with hydrogen peroxide

Treatment with the enzyme pectinase has been reported to lower the cationic demand of thermomechanical pulp (TMP) bleached with alkaline peroxide in t he laboratory. We have extended this discovery to bleached TMP produced ind ustrially, and shown that commercial enzyme preparations can treat pulp wit hin 15 min at the temperature and pH values prevalent in paper mills. About half of the cationic demand in the bleached pulp can be destroyed by pecti nase. Dynamic drainage jar experiments show that the enzyme treatment impro ves the effectiveness of several cationic polymers to increase retention of fines and filler particles. It does not increase retention in the absence of retention aids or with nonionic polymers, and does not damage the streng th properties of the pulp. Pectinase could be easily incorporated into pape r machine stock preparation systems to lower the charges of cationic retent ion aids needed in furnishes containing peroxide-bleached mechanical pulp. (C) 2000 Elsevier Science Inc. All rights reserved.