Pulping Wax Containing Old Corrugated Containers with Hardwood Chips in a Kraft Pulping Operation

A strong need exists for the paper industry to develop methods to recycle wax-treated old corrugated containers (WOCC). This research evaluated a process to recycle WOCC by incorporating it into a conventional kraft pulping process. A pilot plant batch digester was used to cook blends of pre-consumer WOCC and hardwood chips. Analysis of the accepted pulps showed that the incorporation of the WOCC in the cooks produced pulps of similar strength and Kappa number at higher yields relative to a 100% virgin hardwood cook. The hexane extractive content of the pulp and the slide angle of resulting handsheets indicated that some, but not all, of the wax was removed from the pulp. A critical parameter affecting the wax removal efficiency was the post-pulping washing procedure. Approximately 95% wax removal was obtained for a digester feed consisting of 25 weight % WOCC and 75% hardwood chips with specific procedures described herein. The resulting pulp had an approximately 1% wax content.