Comparison of cooking technologies for production of softwood kraftliner pulp

Kraftliner, used as the top and bottom layers in corrugated board, is one of the major paper products in the United States and worldwide and is a long-term growth business area for the pulp and paper industry. However, for many years pulping development for kraftliner has been limited. The lack of development may be because corrugated board standards in many countries have specified basis weight and not strength demands on the corrugated board. With the modifications of Item 222/Rule 41, the situation in the United States has changed. Recently, a new cooking technology has been developed enabling defibration of softwood pulps at considerably higher kappa number with low reject content. Pulp quality as a function of kappa number has been evaluated for this new cooking technology compared to pulp produced using a conventional kraftliner cooking technology. Lower H-factor demands and increased strength, measured as tensile energy absorption, were the most important differences found between the two cooking systems in this study.