Effect of size press coating of cationic starch/ nanofibrillated cellulose on physical and mechanical properties of recycled papersheets

Abstract

This study aimed to evaluate the effect of size press coating on two types of recycled papers using different types of nanofibrillated cellulose (NFC) and cationic starch (CS) on physical and mechanical properties. Wheat straw was used as a cellulose source, and NFC was obtained through oxidative and enzymatic pretreatments. Recycled fluting and coreboard papers were coated with cationic starch/NFC blends at various concentrations of NFC (0.5%, 1%, 2%, 3%, and 4%) using a three-time repetitive size press application, followed by one-time drying section, and compared to uncoated papers. The application of a coating suspension containing 4% periodate-oxidized NFC on both paper surfaces resulted in a significant improvement in the tensile index, burst index, and internal bond strength of the papersheets, with increases of up to 60.6%, 96.3%, and 119.9%, respectively. Furthermore, significant decreases in air permeability were also observed with reductions of 75% and 81.6% for coreboard and fluting papers, respectively. Compared to other pretreatment methods, periodate oxidation resulted in higher viscosity values in NFC samples. Therefore, the application of periodate-oxidized NFC with a size press resulted in a significant improvement in the mechanical and barrier properties of papers made from recycled pulps.

Potential use of nanofibrillated cellulose-loaded cationic starch solutions as coating formulation for recycled fluting papers

“…Additionally, Fidan et al (2021) noted a substantial 110.9% improvement in internal bond strength following the surface sizing of 90 g/m 2 fluting papers using CS/CNF suspensions. Similarly, Tozluoğlu and Fidan (2023) reported 119.9% increase in internal bond strength of 110 g/m 2 recycled fluting paper sheets after size press of CS+4% CNF. In comparison to the previous findings, this gradual increase can be explained by the use of untreated control samples rather than CS surface sized samples that were evaluated in the previous study.…”

Size press practices and formulations affecting paper properties and process efficiency: A Review

“…The default base-sheet (corrugating medium) was compared with versions treated at the 0.5%, 1%, 2%, 3%, and 4% levels with NFC. As shown, the tensile index increased by a factor of about 1.4 and the air permeability fell to about 0.17 times its initial value as the level of nanocellulose was raised from zero to 4% (Tozluoglu and Fidan 2023). The most important downside of using nanocellulose at the size press is likely to be its strong contribution to viscosity.…”

“…Fidan et al (2021) showed that inclusion of NFC in a size press formulation was able to increase tensile and burst strength values by 52% and 194%, respectively. In follow-up work, Tozluoglu and Fidan (2023) showed that a combination of cationic starch and NFC applied to the surface was able to increase the tensile strength and internal bond strength of corrugating medium.…”

“…Examples of paperboard strength and resistance to air permeation increases achieved by inclusion of nanocellulose at the levels shown included with 4% solids corn starch solution at the size press. A: Tensile index (N•m/g); B: Air permeability (m 3 /min); Data replotted from Tozluogluand Fidan (2023)…”