Fibre Content
Recycled paperboard utilizes secondary furnish to manage the ratio of recovered post-consumer fibres against virgin pulp supplies. This term describes a specific input stream comprised of de-inked or refined waste paper that mills introduce during the wet end forming stage. Papermakers adjust this volume to balance surface strength requirements with cost targets and environmental specifications.
The resulting sheet gains density from the varied fibre lengths present in these recycled sources.
Process Requirement
Mechanical cleaners and screens separate contaminants from the slurry before it reaches the headbox. Heavy rejects such as plastic fragments or metal staples exit the flow loop through centrifugal force. Fine screens remove smaller particles like adhesives or synthetic pigments that withstand standard washing.
Operators monitor the freeness of the mixture because these short fibres retain water differently than virgin cellulose.
Structural Impact
Final board properties depend upon the proportion of these secondary fibres contained within the inner plies of a multi-ply sheet. Higher concentrations reduce the burst strength and folding endurance of the package compared to a purely virgin substrate. Precise mill control over the refining stage improves the bond between disparate fibre types and mitigates the loss of stiffness.
Consistent monitoring of the drainage rate ensures that the machine speed remains stable during production runs.
