Mini-Encyclopedia of Papermaking Wet-End Chemistry
Additives and Ingredients, their Composition, Functions, Strategies for Use


Composition: Four main components of "old corrugated container" (OCC) pulps are unbleached softwood kraft pulp (mainly from the linerboard), semi-chemical hardwood pulp (from the fluted medium), starch (as an adhesive), and water (often 8% or more).

Function: OCC pulp is often used for the production of linerboard. It is worth noting that the high-yield hardwood from the corrugated layers of boxes is not ideal for making linerboard, since the fibers are not as long and they don't bond as well as softwood kraft.

Strategies for Use: Papermakers employ such steps as hydropulping, high-density hydrocyclone cleaning, thermal dispersion, flotation, and washing or thickening to remove contaminants. The pulp is refined and cationic starch is added as needed to achieve the target strength properties. The expected slower drainage of recycled furnish, especially after the repeated refining treatments, may require changes to the forming section of the machine, e.g. the addition of a top-wire section to a Fourdrinier machine. Alternatively, inadequate dewatering can be addressed by use of drainage aids. Wax-containing corrugated boxes (for fruits, chickens, etc.) should be separated from the incoming supply to avoid contamination.

Cautions: Recycled unbleached kraft fibers and slurries of these fibers may contain hazardous contaminants.

Appearance of corrugated container cut edge   The net fiber composition of typical OCC pulp collected in the U.S. can be traced to its origins in two different kinds of plies.

PLEASE NOTE: Users of the information contained on these pages assume complete responsibility to make sure that their practices are safe and do not infringe upon an existing patent. There has been no attempt here to give full safety instructions or to make note of all relevant patents governing the use of additives. Please send corrections if you find errors or points that need better clarification.


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This page is maintained by Martin Hubbe, Associate Professor of Wood and Paper Science, NC State University, .