Inter-Ply Bond Strength Development in Recycled Fiber Formations under Variable Dewatering Pressures
Optimizing shoe press peak pressure and wet-end couch solids maximizes inter-ply bond strength in multi-ply recycled fiber formations.
Recycled Fiber Formations
Sheet Construction
Distribution of reclaimed cellulose fibers during the sheet-forming process of a paper machine determines the mechanical properties and uniformity of the resulting board. Optimizing recycled fiber formations allows papermakers to produce high-strength board from lower-grade raw materials by managing how the fiber network is constructed. This process is key to achieving consistent strength in recycled paperboards.
Fiber Properties
Secondary fibers undergo multiple cycles of wetting and drying, which reduces their natural bonding capability and makes them shorter and less flexible than virgin fibers. Managing recycled fiber formations requires careful control of the headbox dilution and the use of chemical retention aids to ensure that these shorter fibers are distributed evenly throughout the web. Multi-ply forming is frequently used to place high-quality virgin or clean recycled fibers on the surface of the board, while lower-quality fibers are concentrated in the middle layers.
This layering technique provides a smooth printing surface while maintaining the bulk of the sheet.
Runnability Control
Consistent sheet formation is essential for preventing issues such as localized thickness variations and uneven ink absorption during printing. Continuous adjustment of the refining process and the chemistry of the wet end helps maintain these forming conditions. This control ensures that recycled boards can be processed without issues on automated packaging lines.