A Comparison of Metering Elements for Producing Double-Coated Paperboard

摘要

Uniform fiber coverage and low surface roughness are typical characteristics of premium-coated paperboard.rnIn a competitive market situation, papermakers have to make the best compromise between these two characteristics,rnsince the former requires contour coating and the latter demands a more leveling coating process.rnThis article demonstrates the possibility to obtain substantial improvements in print quality by simply changing therncoating leveling elements (rods or blades) on a conventional coating head, without any costly investments.rnThe most common leveling elements for coating of paperboard, namely smooth rods and steel blades (running inrnbent mode), are here compared to soft-tipped DUROBLADE® and systematically evaluated in differentrncombinations for pre-coat and topcoat operations.rnThe measurement results of coating surface roughness, gloss and brightness have been evaluated and compared withrnthe actual print quality. Somewhat astonishingly, and perhaps unexpected for many in the paper industry, thernrelationship between measured PPS, gloss and/or brightness is quite a poor indicator for the rating of printability andrnof the visual appreciation of the printed sheets.rnThe used materials and methods, together with the trial conditions and resulting values are all described andrnpresented in this article.