Amylase-Assisted Deinking of Copy Paper - Part 2, 1998 Recycling Symposium Proceedings

Bacterial a-amylase (BAN 120 L, Novo Nordisk) was used to enhance flotation deinking of copy papers. Commercially available copy paper (Yorktown, Union Camp) was used for the initial experiments. After printing a standard pattern with a Sharp FS-8300 copy machine, the paper was subjected to accelerated aging and then pulped under standard conditions. Two enzyme charges (2 and 5 IU per g of pulp) and various mixing speeds (100 to 500 rpm) were studied for the enzymatic treatment. Flotation deinking using a flotation aid (0.15% DI 600, High Point Chemicals) was subsequently performed. Increasing the mixing speed from 100 rpm to 500 rpm increased the reduction of residual toner by 48% when an amylase charge of 2 IU per OD g of pulp was applied The enzyme-assisted deinking was further investigated using pilot-machine papers which contained wet-end starch and/or starch surface sizing. Four different types of copy papers (80 g/m 2 ) were produced. The first type had no starch addition, the second had starch surface sizing but no wet-end starch, the third had wet-end starch but no surface sizing, and the fourth had both wet-end starch and starch surface sizing. After printing, accelerated aging, and hydrapulping, the papers were treated with an amylase charge of 5 lU per g of pulp at a mixing speed of 500 rpm. Flotation deinking was performed with 0.15% flotation aid. The a-amylase pretreatment improved the deinking efficency for all papers containing starch. For example, the residual toner area was reduced by 35% after an a-amylase treatment of the starch surface-sized paper.

The effect of adding a cellulase hemicellulase mixture to the a-amylase treatment was also analyzed. Two different commercially available copy papers (Union Camp and Georgia Pacific) were used. The freeness of the pulp increased (95 mL) but the handsheet strength properties were not significantly affected. A 3-4% increase in deinking ability was achieved with the enzyme combination, primarily because toner particles smaller than 60 pm were removed more effectively.