Methods for sizing fiber webs

摘要

Pond sizing, and film sizing with grooved application rods are the most traditional ways to add surface size, most commonly starch, on fiber webs particularly on paper or board webs. In these methods surface size viscosity must be below 100 mPa·s, typically it is between 10-40 mPa·s. This limited viscosity restricts possibilities to increase surface size solids content, which in turn prevents running speed growth if more drying capacity cannot be added to. In these traditional methods the sizing process is typically symmetric for both sides of the fiber web. In these following new methods the sizing agent, preferably starch, is applied with different methods directly to the fiber web or indirectly via roll surface i.e. the sizing agent is applied first on the nip roll surface which transfers the sizing agent into the nip where it is further transferred into fiber web.