Alkaline peroxide mechanical pulping of northeastern hardwoods

The Alkaline Peroxide Mechanical Pulping (APMP) process has been shown to produce high quality pulp commercially from aspen wood. Difficulties have been reported in applying the process to the typical hardwoods in the Northeastern United States due to their higher density and darker color. The objective of this study was to produce strong, bright APMP pulp from maple and birch woods through improved impregnation techniques. In this study, hardwood chips (Betula paperifyra, Acer rubrum, and Populus tremuloides) were pulped using a variation on the APMP process. Control pulps (TMP) were made with no chemicals. Birch, while producing the weakest TMP, showed the greatest response to chemical treatment, with a six-fold increase in tensile index and a seven-fold increase in tear index as compared to birch TMP. Poplar produced stronger TMP but showed a smaller increase in strength on chemical treatment. The increase in pulp strength may be attributed to increased length, flexibility, and bonding ability of the pulp fibers. Brightness of the poplar and birch pulps averaged 81% ISO, while the maple pulps averaged 79% ISO. The greater bleach response of birch wood compensated for its lower initial brightness.