Use of Superheated Steam Drying to Increase Strength and Bulk of Papers Produced from Diverse Commercial Furnishes

Studies from this laboratory have documented significant changes in properties when paper is dried in superheated steam rather than, as in all current processes, in air. Extending these investigations to additional important pulp types, to recycled pulps and to filled papers, using commercial furnishes from mills, has identified further grades of paper for which drying in superheated steam enhances key properties. For bleached chemithermomechanical pulps and blends with kraft pulp as used for tissue and toweling, strong paper resulted, with 10% higher bulk. Linerboard from 100% recycled old corrugated containers (OCC) is obtained with various strength properties increased by up to 21% with no densification, actually a 4% increase in bulk. Linerboard from high-yield (55-67%) virgin kraft pulps show 23 to 37% increase in strength and toughness. Filled papers containing 0-10% clay can be produced with the same brightness but about 23% higher tensile index when dried in superheated steam.