Effect of pH and enzymes on strength of recycled fibers during refining

Abstract

Recycled fiber-based papermaking in America is experiencing a persistent reduction in the strength of the incoming fiber. To maintain paper strength properties, paper mills respond by increasing basis weight, dry strength, etc. On average, the fiber cost component in recycled paper is approximately 40% of the total manufacturing cost. Increased fiber weight results in higher operating cost and has a negative effect on production rate, especially on dryer-limited paper machines. Increased pH and use of certain enzymes can improve strength during subsequent refining. The ProLab refiner was used to generate laboratory refining curves to evaluate changes in fiber bonding. The effect of pH and enzymes pretreatment on the strength development and change in drainage of recycled fibers with refining was evaluated.