Technical Lignins and Their Utilization in the Surface Sizing of Paperboard

Abstract

Technical lignins, which are the coproducts of the pulping industry, have a high potential for use in surface sizing of paperboard. We investigated the use of kraft lignin and lignosulfonate in surface sizing of paperboard with the target of understanding the influence of lignins on the development of strength and hydrophobicity. Prior to surface sizing, the lignins are purified by ultrafiltration and precipitation respectively. Strength properties and hydrophobicity of lignin-sized paperboard were measured and compared with references as well as with unsized paper. An increase in the strength properties of lignin-sized samples was observed, which was in the same range as references and at least 10% higher compared to unsized paperboard. Moreover, air permeability, hydrophobicity, and water absorptiveness were affected, and depending on the lignin art, an improvement was achieved. These results encourage partial or total substitution of conventional surface-sizing chemicals by technical lignins.

Per‐ and polyfluoroalkyl substances and their alternatives in paper food packaging

“…Chitosan has been the focus of general reviews (Bakshi et al., 2020; Bellich et al., 2016) and reviews focusing on papermaking and coating applications (Khwaldia et al., 2010; Kopacic et al., 2018; Song et al., 2018). It is usually extracted from seafood wastes, such as shrimp or crab shells, by treatment with acids to remove minerals and then with sodium hydroxide to deacetylate chitin to chitosan.…”

“…Costs of alginates are rather high ($5 to 10/lb), so high‐volume industrial applications have not become widespread. Paper coated with sodium alginate at 6 g/m 2 was found to have good to excellent grease resistance (Kit values 7 to 12) and near zero air transmittance, indicating a continuous coating was achieved (Kopacic et al., 2018). WVTR was reduced by only about 35% to 45% after coating, reflecting the high permeability of sodium alginate to water.…”

“…Kraft lignin coatings were found to improve the water resistance of paperboard (Kopacic et al., 2018), while coatings composed of lignin with aluminum salts and cellulose nanofibers gave good water and oil resistance (Krigstin et al., 2017). Shellac, a natural resin derived from the lac insect, has long been used as a water‐resistant protective coating for wood, paper, foods, and pharmaceuticals (Hagenmaier & Shaw, 1991; Hult et al., 2010), but its use is rather small due to high cost and limited availability.…”

Hydrophobic copolymers added with starch at the size press of a paper machine: A review of findings and likely mechanisms

“…Han and Cho (2016) showed related results by adding black liquor (from kraft pulping) together with alum to size-press starch. More recently, Kopacic et al (2018) studied a series of technical lignins and showed that kraft lignin held considerable promise as a hydrophobic agent for surface sizing. Besides, the results showed that the lignin-sized specimens had improved strength properties, which were at least 10% higher compared to unsized paperboard, in addition to improvements related to air permeability, hydrophobicity, and water absorptiveness (Kopacic et al 2018).…”

“…More recently, Kopacic et al (2018) studied a series of technical lignins and showed that kraft lignin held considerable promise as a hydrophobic agent for surface sizing. Besides, the results showed that the lignin-sized specimens had improved strength properties, which were at least 10% higher compared to unsized paperboard, in addition to improvements related to air permeability, hydrophobicity, and water absorptiveness (Kopacic et al 2018). Recently it has been shown that crude wood rosin and derivatives have potential as hydrophobic surface additives with cationic starch in size press application (Bildik Dal et al 2020).…”