Soy Proteins As a Sustainable Solution to Strengthen Recycled Paper and Reduce Deposition of Hydrophobic Contaminants in Papermaking: A Bench and Pilot-Plant Study

Abstract

Hydrophobic contaminants (stickies) incorporated with recycled fibers cause severe papermaking processing and product quality problems, which lead to low runnability and increased production cost. Stickies negatively affect paper strength and many other properties. In this work, we propose a sustainable approach by the application of soy protein isolate (SPI), soy flour (SF), and soybean lipoxygenase (LOX) as agents to combat hydrophobic contaminants. Tests at the bench and pilot-plant scales and under conditions similar to industrial operations demonstrated the reduction of associated challenges and the improvement of a paper’s dry strength. The soy agents were applied to aqueous dispersions of lignin-free recycled fibers (dosage levels of 1–2% based on the fiber dry weight), which contained additives typically used in papermaking (fillers, sizing agent, and others). Talc, a common detackifier, was applied in similar systems that were used as reference. The proteins were added under both high and low she...