Method and apparatus for calendering a paper or board web

摘要

In the inventive method and apparatus for calendering a surface of a paper or board web, a temperature difference is created between the web surfaces so that the surface to be calendered is cooler than the opposite surface. In addition, moisture within the web is transferred using the so-called heat pipe effect toward the cooler surface while substantially preventing evaporation of moisture from the web so as to create a predetermined moisture profile transversely through the web and decrease the glass transition temperature of the web at the relatively cooler surface to be calendered. Finally, the web having the predetermined moisture profile is advanced into the calendering nip so that the relatively cooler and moister surface of the web is pressed against the heated roll of the nip to thereby calender that web surface.