Steam Processing of Regenerated Cellulose Fabric in Concentrated LiCl/Urea Solutions

Abstract

Regenerated cellulose fibres exhibit strong swelling in concentrated aqueous LiCl/urea solutions. Dependent on treatment temperature and solution composition, fibre diameter increases from 15 µm at room temperature in water to 46 µm in LiCl/urea solution. Treatment in such solution is an alternative to the processing of regenerated cellulose fibres in alkaline solutions. To limit the amount of swelling solution used, the final concentrated solution is formed in a superheated steam atmosphere at 120–130 °C by water evaporation and equilibration. As a result of the treatments the ability of the fibres to hold dye changes and shrinkage of the fabric is observed, while losses in strength and sample weight are not significant.

Cellulose in NaOH–water based solvents: a review

“…Cellulosic materials will swell and hemicellulose will be mostly dissolved, changing the structure of the material such as pore structure (Kasahara et al 2004;Bredereck et al 2003), fibrillation tendency (Zhang et al 2005c) or crystallinity (Colom and Carrillo 2002). Such treatments are thus strongly influencing the accessibility of cellulose chains to small solvent molecules, influencing subsequent chemical treatments (Tatarova et al 2012). An interesting phenomenon, which can further enhance accessibility, is the fact that parts of the fibers can swell more than others due to inhomogeneity of concentration or penetration, creating stress inside the fibres (Öztürk and Bechtold 2008)…”

New Trends in High‐Performance Fibers and Fiber Technology

“…Preparation in this way enabled the Young's modulus to be enhanced and made the hybrid material more attractive for the said target application. Last but not least, Bechtold and co‐workers describe the swelling of regenerated cellulose in aqueous LiCl/urea solutions and the impact of this novel procedure on dyeability, shrinkage, and strength 12…”

Anionically Stabilized Cellulose Nanofibrils through Succinylation Pretreatment in Urea–Lithium Chloride Deep Eutectic Solvent

“…Aqueous urea–LiCl mixtures swell regenerated cellulose fibers by penetrating into the cellulose structure and breaking the inter‐ and intramolecular hydrogen bonds . However, urea–LiCl–water mixtures do not dissolve cellulose, which would result in the destruction of the original cellulose crystalline structure.…”

“…[32] Aqueous urea-LiCl mixtures swell regenerated cellulose fibers by penetrating into the cellulose structure and breaking the inter-and intramolecular hydrogen bonds. [60][61][62] However, urea-LiCl-water mixtures do not dissolve cellulose, which would result in the destruction of the originalc ellulose crystalline structure.I naddition to the urea-salt mixtures, concentrated salt solutions, or so-called molten salt hydrates,f rom LiCl can swell cellulosef ibers, [63,64] andu rea-containing microemulsions have also been reported to disrupt hydrogen bonding and, thus, promote cellulose nanofibril production. [65] Moreover,t he addition of lithium salts (e.g.,L iCl and LiBr) increases the dissolution of cellulose in a1 -butyl-3-methylimidazoliumbased ionic liquid system.…”