Production of Multi-ply Paperboard from Old Corrugated Container Pulp and Application of Fine Materials in the Middle Layer

For appropriate use of fines and fiber fractions and how to apply them in paper structure, various multiply boards were made and the effect of fines removal, and their application in the middle layer, or only their removal from the top and bottom layers were investigated. The results showed that by eliminating the fine materials and producing a fine-free three-ply board, the bending resistance and the bending resistance index were increased. However, studying the bulk property and the SEM images of the boards revealed that layers containing no fines were bulky and rough, meanwhile transferring the fines to the middle layer made it too dense. The ash content of fines indicated that significant percentage of the fines were comprised of fillers and minerals. Also it was shown that production of the board with a multi-ply structure did not negatively affect the physical and mechanical properties, but can help the process parameters.