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Cellulose (2021) 28:10183–10201
Graphic abstract
Keywords Northern bleached softwood kraft pulp Paper strength additive Hemicellulose Locust bean gum Adsorption isotherms Adsorption kinetics
paper strength (Bhaduri et al. 1995; Silva et al. 2010). The earliest paper strength additives were polysac- charides with structural affinity for cellulose such as locust bean gum (LBG) and guar gum (Leech 1953; Lindstro¨m et al. 2005; Most 1957; Russo 1959; Swanson 1950). Leech (1954) concluded that 0.5 wt% LBG dosage doubled the bonding strength of paper. Swanson (1950) reported that tensile strength increased by 33% following sorption of 2 wt% LBG to coniferous sulphite pulp. Burst strength increased 32% with 0.5 wt% LBG in beaten pulp; this corresponded to a 70% reduction in beating time (Swanson 1950). Paper strength enhancement by hemicellulose adsorp- tion results from an increased number of bonds plus increased bonded area and bond strength (Leech 1954). The primary bonding between fibres and between hemicellulose and fibres is hydrogen bonding (Niskanen 1998; Leech 1954; Hannuksela et al. 2002). Many factors have been shown to influence adsorption of hemicellulose onto pulp fibre: adsorp- tion conditions (Russo 1959; Gruenhut 1953; Leech 1953; Most 1957; Swanson et al. 1949), fibre proper- ties (Zakrajsˇek et al. 2009), and hemicellulose prop- erties (Hannuksela et al. 2002, 2004; Lindqvist et al. 2013). Given the multitude of factors and interactions,
Introduction
Paper strength, essential to many applications, relies on the number of interfibre bonds, the strength of the bonds, fibre properties (e.g. fibre strength, length, and coarseness), and the distribution of fibres and bonds (sheet formation) (Niskanen 1998; Lindstro¨m et al. 2005; Leech 1953, 1954). Paper strength can be modified through mechanical refining and the use of additives such as polysaccharides. Softwood grown in the Northern hemisphere (e.g. British Columbia, Canada) produces high-strength bleached kraft pulp; finding ways to further enhance strength properties while reducing refining energy is a key objective for Northern Bleached Softwood Kraft (NBSK) producers. Increasing paper strength through refining con- sumes large amounts of mechanical energy. Strength improvement through application of additives after refining reduces the energy required to achieve target
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