Highly Carboxylated Pulps – A New Approach

The export of market kraft pulp is a significant part of the Canadian forest products industry. Although northern softwood kraft pulps are premium products in the international pulp marketplace, there is interest in producing truly specialty pulps whose properties extend beyond the physical and chemical property boundaries of current pulping and bleaching operations. Whereas the pulping and bleaching literature has for decades focused on improving pulp properties, we know of only a few examples of post-bleaching fiber modification in pulp mills. Instead, the pulp producers leave it to papermakers to tune paper properties with chemical additives in the papermaking processes. Most papermill fiber chemical treatments including sizing additives, dry strength resins, and wet strength resins, involve interactions with the exterior surfaces of pulp fibers. We propose that market pulp mills producing dry, or nearly dry, pulp offer a unique opportunity to influence fiber surface properties by fixing reactive polymers onto fiber surfaces when the pulp is heated on pulp drying machines. The objective of the work described herein was to develop new approaches to modify pulp fiber surfaces at the end of the pulp mill bleaching processes through polymer grafting. This contribution covers the highlights of recent publications [1-4].