The potential of replacing the starch with soda and formacell lignins in surface sizing and evaluation of physical and mechanical properties of produced liner papers

In this research, the physical and mechanical properties of the surface sizing liner papers with starch formulation with soda and formacell lignins have been investigated. The soda and formacell lignins from the remaining black liquor were separated and then was replaced with anionic starch in 30, 50, 70, and 100 ratios. In addition, 0.3 g/m2 alum as a cationic agent was charged to the suspension. The results of this study show that even by 100 % replacing starch with both types of lignins, the physical characteristics (air resistance, cobb, coarseness) and mechanical properties of surface-sized paper have been improved compared with control paper. According to the results, 50/50 lignin/starch ratio improved the mechanical and physical properties better and was determined as optimum level. For soda lignin without alum, tensile (36.21 N.m/g) and burst (1.58 Kpa.m2/g) indices increased by 55 and 35 % respectively, compared with the control in the optimum level. For formacell, lignin/starch in 50/50 ratio without alum, the tensile and burst indices were increased 47 and 27% respectively, compared with the control sample. According to the results, it is possible to replace at least 50% of starch with the above-mentioned lignins, which will play an important role in food security and add value for pulp mills.