Softcalendering: Effect of Temperature, Pressure and Speed on Sheet Properties, 1995 Finishing and Converting Conference Proceedings

Toshiharu Enomae

Ting Huang

Pierre LePoutre

University of Maine

Rolls of wood-containing basestock, coated grades, and of wood-free basestock were soft-calendered with two nips at two levels of roll temperature (120 and 177 ºC), nip load (175 and 350 kN/m ) and web speed (760 and 1220 m/min ). The results of a 2(3) factorial design experiment have been analyzed with ANOVA over the ranges studied. Temperature had the largest effect on gloss and PPS roughness on the 3 papers. Nip load had the largest effect on thickness and air resistance. Mechanical properties were not much affected. Comparison between soft- and supercalendering on the wood-containing coated grade showed that softcalendering achieved higher gloss for the same bulk reduction.

With regard to roughening by water, the results indicate that, under the conditions examined, softcalendering at the higher temperature was superior, though modestly, to supercalendering. Overall, temperature had the largest effect, in that all samples softcalendered at the higher temperature had a lower roughness and a higher gloss than the supercalendered sheets and kept their advantage after contact with water. The concordance between surface changes and bulk changes upon contact with water suggests that roughening is mainly associated with bulk phenomena. The greater the bulk reduction during calendering, the greater the roughening. The advantage of softcalendering would therefore stem from the lower bulk reduction achieved for a given gloss or roughness level rather than from thermally induced stress relaxation.