Emerging technology for sustainable production of bleached pulp from recovered cardboard

Post-use corrugated packaging cardboard is commonly known as old corrugated containers (OCC). They are complex and heterogeneous materials composed of various sources of unbleached cellulose pulp derived from several raw material processes which must be revalued due to its functionality, recyclability, and biodegradability. Besides, as recovered pulp have a greater composition of long fiber than short fiber because are mainly manufactured from softwood pulp by the kraft process. OCC are the main category of recovered paper; however, due to their high lignin content and hemicelluloses, additives, pollutants, hornification and degradation of fibers and other problems resulting from the pulp to cardboard conversion processes, their physical properties decrease with each recycling or reprocessing, which justifies evaluating a set of technologies to improve it. The objective of this work was to obtain improved unbleached and bleached OCC pulp more ecologically and economically justifiable than derived from wood chips for higher grade papers using sustainable processes evaluated in pilot scale tests. Mixed OCC were collected as waste from a landfill, cleaned, repulped, and treated with extended delignification with the alkaline soda process, obtaining a pulp with significant physical–mechanical improvements in relation to the original material, such as tensile strength, tearing resistance, bursting strength and folding endurance. The OCC soda pulp was bleached by a sequence totally free of chlorinated compounds (TCF), obtaining bleached pulp with optical and mechanical properties comparable to virgin pulps of annual plants such as bagasse but with improved drainage properties and lower processing costs. According to their properties, it is a competitive pulp obtained with emerging and existing technologies, available for use in various grades of printing and writing paper replacing totally or partially bleached wood pulp.