The Challenge of Recycled Fibers
The paper and board industry is increasingly turning to recycled fibers to promote sustainability. However, recycled fibers often exhibit reduced bonding strength, leading to weaker cartonboard products. To address this, manufacturers incorporate strength-enhancing agents, such as starch or bio-based binders, during the production process. The effectiveness of these agents largely depends on their penetration depth into the fiber network.
Traditional Film Sizing at KCL
KCL offers a versatile pilot dispersion coating line equipped with various application stations, including a traditional film size press. This method applies a thin film of sizing agent onto the surface of the board, enhancing surface properties and providing a degree of strength improvement. However, the penetration of the sizing agent into the internal fiber network is limited, which may not suffice for boards made predominantly from recycled fibers.
Introducing Hard Nip Sizing Technology
To overcome the limitations of traditional sizing methods, KCL has introduced the hard nip sizer into its pilot line. This advanced technology employs higher nip pressures (up to 120 kN/m) to press the sizing agent deeper into the fiber network, significantly enhancing both surface and internal strength properties of the board. The hard nip sizer operates by applying starch onto the rolls, which then transfer the starch into the nip where it is further pressed into the paper web. At KCL we can apply the starch on the rolls with different technologies like rod or spray.
Advantages of Hard Nip Sizing
- Enhanced Strength: By increasing the density of fibers and promoting better starch penetration, hard nip sizing improves the bond strength within the fiber network, leading to stronger cartonboard products.
- Material optimisation: Improvement in strength of recycled liner and fluting materials enables lighter packaging materials for converters and end-users
- Operational Efficiency: The design of the hard nip sizer, comparable to calendering systems, offers improved smoothness and runnability, reducing maintenance costs and improving overall production efficiency.
KCL’s Comprehensive Pilot Services
Beyond sizing technologies, KCL provides a range of pilot and laboratory services to support product development and process optimization.
At KCL, dispersion coating trials can be scaled up from laboratory to semi-pilot and full industrial pilot scale. In semi-pilot scale pilot lines, the application technologies available are roll, gravure, reverse gravure and spray. On a full scale KCL pilot coating line the application technologies available today are film size press, hard nip sizer, roll and jet application, spray coating and curtain coating stations.
KCL’s accredited testing laboratory can assist in the testing of coated materials and their properties. Commonly requested tests today include barrier properties, recyclability, compostability, strength and structural properties of paper and board.
For more information or to schedule a pilot trial, contact: Mikko Mensonen, Head of Coating, Printing, Finishing, mikko.mensonen@kcl.fi, +358 40 522 6005