Feasibility of Anionic Waxy Maze Starch as a Coating Cobinder

This project will demonstrate the potential of incorporating a 100% waxy maze, anionic starch into a paper coating. This has been done in the past using oxidized starches as a primary binder, and has been met with a great deal of success with respect to rheological improvements as well as improved runnability in coating operations. The primary drawback to the use of oxidized starches in coatings was the negative impact that they had when introduced to the wet end of the paper machine as broke. The anionic properties of the starch decreased retention of fines and fillers on the fourdrinier wire. The negative charge also carried through to wastewater treatment, causing increased turbidity of clarified effluent. This thesis considered a different starch chemistry (sultanate and carboxylate versus high carboxylate for oxidized starches) as well as a different starch functionality. This study focused on using anionic starch as a cobinder. A cobinder is generally considered as an additive or rheology modifier. By using the starch as a cobinder, less anionic charge would be introduced to the sheet, thereby minimizing the deleterious effects in paper machine wet end chemistry as well as wastewater clarification processes. Anionic waxy maze starch was evaluated by comparing its performance to a nonionic waxy maze starch. Rheological properties were assessed as well as coated sheet properties. Rheological benefits were defined as an improvement, in other words, lower shear stress at a given shear rate. Rheologically, the anionic starch did not show any benefits relative to the nonionic starch when used at addition rates of 0.2, and 1.0 pph in conjunction with 10.0 pph of DOW 620 latex. When the starches were used at 4.0 pph without latex, the anionic starch actually had a deleterious effect on rheology. Very little distinction could be made between the anionic and nonionic starches with respect to brightness, opacity, scattering coefficient, absorption coefficient, coefficient of static friction, coefficient of kinetic friction, and IGT pick. Parker print surf was consistently lower for the anionic starch, which may suggest better printability. Overall, it was decided that the anionic starch did not demonstrate enough advantages over the nonionic starch to become a suitable coating additive alternative. It is assumed that this is due to a chemical incompatibility associated with the sultanate chemistry of RediBOND 3030