Optimum Paper Performance Through New Calendering Technology, 2000 Coating Conference Proceedings

A. Hiorns, M. Julin--New multi-nip calendering technology uses polymer rolls that are resilient to high temperatures and roll weight compensation to allow much faster speeds to be achieved. The results in this paper show that paper quality similar to or better than that produced by a traditional supercalender can be produced at speeds of at least 1500 m/min, with the newest multi-nip calenders designed for speeds up to 2000 m/min. This allows the concept of on-line supercalendering to be considered. Measured differences in coating structure have been shown to a significant effect on the thermo-softening properties and hence quality of the final calendered paper. It was shown that a coating structure which is more open can be produced by using a blend of platy clay and blocky ground calcium carbonate (GCC) compared to using just an ultra-fine GCC. The increased micro-roughness of the open structure resulted in relatively low sheet gloss generation at low temperatures, but at higher temperatures the gloss levels produced were comparable to that of the ultra-fine GCC. The multi-nip calender gives benefits in terms of the gloss and smoothness with density relationship. Improvements in print gloss as well as micro-scale profilometer roughness were also observed.

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