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 shear conditions, and their effect in reducing paper tackiness and increasing internal bonding was confirmed. The maximum reduction in tacky particles count was achieved with SF (2% addition level based on fiber) under mild agitation and 30 min contact time. Remarkably, synergistic effects on the fiber electrostatic charges and paper porosity and formation were observed upon the addition of the soy proteins. The obtained results indicate that residual soy products represent an inexpensive, sustainable, and environmentally benign solution to enhance papermaking performance relative to conventional and more expensive agents that are in current use.

Paper-Based Oil Barrier Packaging using Lignin-Containing Cellulose Nanofibrils

“…One explanation for the observed difference in the mechanical attributes between the two coatings can be in part due to the role of lignin in reducing the number of effective hydrogen bonds within the cellulosic network. Similar effect has been reported for the presence of wood extractives between the cellulosic fibers [36]. Yet, the obtained average tensile values are close to some commercially available cellulose-based films such as cellulose acetate (56 MPa) [37], and cellophane (40-90 MPa) [38,39], that have been used as barrier films in food-related applications [40].…”

Cellulose Nanomaterials—Binding Properties and Applications: A Review

“…[ 3 , 5 , 6 , 21 , 30 ]. The hydrogen bonds between the hydroxyl groups prompt a highly ordered conformation of the cellulose chains in elementary fibrils that further facilitate adhesion with other polymeric components, e.g., with lignin or proteins, to form networks in aqueous media [ 12 , 31 ]. Since an energy-intensive mechanical grinding is required to separate the stacked fibrils, different types of pretreatments, such as alkaline [ 32 , 33 ], radiation [ 32 ], chemical [ 34 , 35 ], and enzymatic [ 36 , 37 ] are typically applied prior to the fibrillation process to remarkably lower the cost and energy.…”

Effect of Nanocellulose on the Properties of Cottonseed Protein Isolate as a Paper Strength Agent

“…Cottonseed protein (CSP) have been used for the formulation of biobased products [18][19][20], as animal feed [21,22], in films, coatings and adhesives [19]. Several proteins have been previously reported as binders and strength agents in paper products, such as soy protein [23][24][25][26][27], gelatin, zein, and hydroxyproline-rich glycoprotein [28] and cottonseed protein [29]. Related work has shown that CSP isolate served as an effective strength agent for nonwovens [30].…”