1. Reducing Paper Strength:
The negative effect of acidic sizing is that it reduces fiber swelling and the ability of fiber fibrillation, thus decreasing almost all strength indices of the finished paper, especially those strength indices that require high hydrogen bonding, such as interlayer bonding.
2. Systemic Corrosion:
For some acidic sizing systems, adding aluminum sulfate to achieve an extremely low pH (e.g., anionic rosin sizing systems, where the pH needs to be controlled within 4.5±0.5) exposes the paper machine system to severe corrosion.
3. Increased Filler Costs:
After adding aluminum sulfate, the system often becomes acidic or weakly acidic. To reduce costs, fillers need to be changed from inexpensive calcium carbonate to talc powder, etc., resulting in increased filler costs.
4. Excessive Dosage Reduces Dewatering Efficiency:
A reasonable dosage of aluminum sulfate can improve paper dewatering efficiency. However, according to practical experience, excessive use of aluminum sulfate (usually over 15 kg per ton of pulp) often leads to difficult dewatering of the finished paper, which instead reduces dewatering efficiency and shortens the service life of the felt.