A mill in Southeast Asia running cultural and packaging grades had just moved off acid rosin sizing to neutral AKD. The switch made sense on paper, but on the machine they hit a wall: sizing degree came in low, and the sheet took far too long to cure once off-machine. Below is the key technical consultation.
Why Leave Rosin Behind
Q: We switched from acid rosin to neutral AKD. Was that the right call, and what are we actually gaining?
A: The move is worth making, and the gains show up in more than just water resistance. AKD runs neutral, so it does not corrode equipment and it extends the life of your wires and felts. The sheet comes out stronger, and it resists yellowing and ageing in storage - which matters if your paper sits in a warehouse before it is converted. Filler utilization goes up, and finished smoothness and print compatibility are clearly better than what acid rosin sizing delivers.
When Curing Lags
Q: Sizing degree is coming in low and the sheet cures slowly after the machine. What's going wrong?
A: Slow curing and weak sizing degree almost always trace back to the AKD molecule not getting the chance to crosslink properly. The usual suspects are insufficient drying temperature, too little dwell time in the dryer section, system pH running low, overdosed filler, or an additive package that fights the sizing. Any of these leaves the reaction unfinished, so curing drags on long after the sheet is reeled. Before raising dosage, check those five - in most cases the fix is in the process, not in the drum.
Getting Application Right
Q: How should we be adding it?
A: You have two workable routes. Add it into the mixing tank and blend thoroughly with the furnish, then use that mixture within two hours - don't let prepared stock sit around. Or feed it continuously online with a metering pump, which suits mills wanting tighter control. Keep the system in the neutral to weakly alkaline band where AKD works, and screen the product through an 80–100 mesh filter before use. That last step is not optional: it is what keeps potential sheet defects off your paper.
What It Delivers
Q: What should we expect once it is running correctly?
A: Low dosage with high retention, fast on-machine curing, and water resistance that holds up over time rather than fading in storage - that combination is what brings the overall cost down. It suits cultural paper, packaging paper, specialty grades, and pulp molding alike. And if the process side is already in good shape, the sizing effect stays stable batch after batch.
If your mill is fighting slow curing, low sizing degree, or is still weighing the move from rosin to neutral AKD, our technical team can review your process conditions and grade mix before you touch the dosage.
