Effect of various pulp properties on the solubility of cellulose in sodium hydroxide solutions

Abstract

The dissolution of pulps with varying characteristic properties, for example cellulose chain length or content of hemicellulose, has been investigated in two alkaline solvent systems [sodium hydroxide (NaOH)/urea/thiourea (8:8:6.5 by wt.) and NaOH/zince oxide (ZnO) (9:0.5 by wt.)]. One standard paper pulp, two dissolving pulps and three pretreated pulps were selected for this study. The dissolution parameters in focus were the fi ber dimensions, average degree of poly merization (DP), polydispersity, water retention value and content of hemicelluloses. The solubility was not infl uenced by the fi ber dimensions. The only signifi cant properties, according to variable importance plot, were DP and composition of the hemicelluloses. It was also established that mass transfer effects during the dissolution stage plays an important role in the dissolution of cellulose derived from pulp fi bers.

Cellulose dissolution in aqueous NaOH–ZnO: effect of pulp pretreatment at macro and molecular levels

“…Cellulose dissolution with aqueous sodium hydroxide (NaOH) has a strong industrial potential due to the rapid, non-toxic, low cost and environmentally friendly process. The process has been known already since the early 1900s (Davidson 1934(Davidson , 1936 and it continues attracting a lot of interest (Cai et al 2008;Egal et al 2007;Hagman et al 2017;Huh et al 2020;Kihlman et al 2012;Medronho and Lindman 2015). The dissolution takes place at low temperature (\ 0°C) and hence there is no evaporation of chemicals during the process.…”

“…However, even with the addition of ZnO, dissolution of wood fibers is poor without a pretreatment, or ''activation'', prior to the dissolution process (Cuissinat and Navard 2006;Kihlman et al 2012;Väisänen et al 2021). The high DP of cellulose has been shown to be one of the most important factors hindering its dissolution in the alkaline system (Isogai and Atalla 1998;Yamashiki et al 1990;Yang et al 2011).…”

Potential of all‐cellulose composites in corrugated board applications: Comparison of chemical pulp raw materials

“…Many cellulose solvents share the drawbacks of high cost, toxicity, and low biodegradability, including ionic liquids that are regarded to be to some extent “green.” NaOH‐based cellulose solvents is an interesting group for their low cost and environmental impact. Additives, such as urea, thiourea, and ZnO can be added to aqueous NaOH solution to increase its effectiveness.…”

“…24,25 NaOH-based cellulose solvents is an interesting group for their low cost and environmental impact. Additives, such as urea, [26][27][28][29] thiourea, 27 and ZnO 30 can be added to aqueous NaOH solution to increase its effectiveness.…”

Enzyme pretreatment of dissolving pulp as a way to improve the following dissolution in NaOH/ZnO

“…In this context, several chemical, enzymatic, and mechanical pretreatments have been investigated (Rahkamo et al 1996(Rahkamo et al , 1998Ciechanska et al 2005;Kihlman et al 2011, Kihlman et al 2012. The beneficial effect of relatively small amounts of ZnO to concentrated NaOH solutions has been observed by, among others, Borgin and Stamm (1950) and Vehvilainen et al (2008).…”