Effect of Calender and Formulation Variables: A Comparison of "On-Line" Soft Nip and Super Calendering, 1995 Coating Conference Proceedings

B. J. Schultz

Rohm & Haas Company

An extensive "on-line" soft nip calendering pilot matrix was run to quantify the response of optical properties to calender temperature, pressure, and formulation variables in 1wc paper. Appropriate comparisons were made to both "off-line" hot/soft finishing and conventional super calendering. Coating colors, applied by a high speed short dwell coater, included an all mineral pigment control and a system containing synthetic pigment. Performance varied widely, as anticipated, in view of the wide range of conditions employed and the diversity of the formulations. Gloss and smoothness were more easily developed on-line than off-line. In general, the gloss and smoothness of the on-line hot/soft sheets approximated that of the supercalendered controls with indications of better brightness and opacity. Inclusion of the synthetic pigment improved the gloss response, allowing use of lower temperature and/or nip load to achieve target gloss.