In-plane Tensile Properties of Paper - Comparison between Shoe Blade and Blade Hybrid Formers

摘要

In this paper, the main interest was to study the impact of two different hybrid formers on in-plane tensile properties of paper, such as tensile strength and CD tearing resistance. A comparison was done between the shoe blade hybrid former (ValFormer) and the conventional blade hybrid former. With the shoe blade former, the top surface dewatering begins in a gentle manner, and this makes it possible to use higher headbox flows and thus lower ingoing (into the twin wire area) consistencies compared to those of the blade hybrid former. Doing so, both MD tensile strength and CD tearing resistance improve at the same time. Formation improves as well, and a positive correlation between formation and the aforementioned tensile properties can be drawn. A plausible explanation for the significant improvement at CD tearing when approaching the optimum operation point (formation, strength) could be related to the improvements (symmetry) at the Z-direction structure of fiber orientation. With the shoe blade hybrid former, the orientation structure starts to become symmetrical and, in this regard, starts to resemble typical Z-profiles achieved with a modern gap former. This can be considered an advantage for paper web runnability.