New Calendering and Coating Tools to Improve Coated Fine Paper Quality, 2008 PAPERCON Conference

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The effect of precalendering, coating and final calendering conditions on the quality of coated fine paper wasstudied in pilot scale. The study included both conventional and new calendering and coating process technology. Metal belt precalendering prior to coating had major impact on final surface properties and printability. However,precalendering conditions had only minor effect on the final paper bulk, when multinip calendering was used aftercoating. Non-precalendered paper and lightly precalendered paper compress more in the final calendering thanheavily precalendered paper. Higher bulk can be achieved with metal belt precalendering, if the final calendering isdone with a lighter load to a constant smoothness level target. Combined metal belt calendering and multilayercurtain coating gave the highest gloss and least print mottle of all trial points. Multilayer curtain coating gives arougher sheet, compared with blade coating. However, commercially accepted smoothness level is reached, if metalbelt precalendering is used prior curtain coating. For finishing of the coated product, multinip calendering providessuperior gloss and smoothness over two nip soft calendering, but the soft calender gives a higher bulk, opacity andbrightness.