Regenerated Cellulose Fibers

Keywords

Biomass • Lignin • Cellulose • Cellulose dissolution • Fiber • Fiber properties

Conventional approach of producing regenerated cellulose through ionic liquids is based on using pulp (>90 % cellulose) obtained from various sources. Recently, attempts have been made to directly use the biomass containing cellulose, hemicel — lulose, and lignin and produce composite fibers. Such an approach would avoid the need to produce pulp and substantially reduce the cost of the fiber and the use of chemicals. Biomass from oak, bagasse, and pine was used with and without pretreatment to produce fibers using 1-ethyl-3-methylimidazolium acetate as the solvent. Type and composition of biomass, conditions used for pretreatment, and dissolution and composition and properties of the fibers obtained and compared in Table 20.1. Fiber production conditions varied depending on the type of pulp, and it was found that fibers containing higher amounts of cellulose had higher strength and elongation [11Sun]. Also, pretreatment resulted in higher cellulose content and therefore better properties. Bagasse could be dissolved and made into fibers using low — or high-temperature dissolution, whereas wood cellulose required the use of high temperatures but shorter time. The ability to directly dissolve lignocellulosic sources and produce fibers could lead to novel fibers and also significant cost reductions. However, the viability of commercial-scale production of this process and the properties of the fibers that can be obtained is not known. In addition, the presence of lignin and hemicellulose could affect further processing (dyeing, etc.) of the fibers, and the properties of the fibers could be adversely affected.

Ionic liquids have been studied as greener alternatives to produce viscose from biomasses [13Cas]. 1-Allyl-3-methylimidazolium chloride (Amimcl) was used to dissolve wood (4 % w/w) obtained from pine (Pinus radiata) and eucalyptus (E. globulus) in a microwave at 110 °C for 10 min and later at 120 °C for 20 min. The dissolved wood cellulose was added into dimethyl sulfoxide (11/3)

Table 20.1 Sources and dissolution conditions of biomass and composition and mechanical properties of the resulting fibers Biomass composition Tensile properties Fiber composition Biomass Cellulose [%] Lignin [%] Dissolution condition Stress [g/den] Strain [%] Cellulose [%] Lignin [%] Oak 79 23.8 175 °С, 30 min 0.8 4 — — Oak 79 23.8 175 °С, 30 min 0.3 2 — — Bagasse 57.8 22.7 185 °С, 10 min 1.0 6 63.6 25.3 Bagasse 57.8 22.7 110 °С, 16 h 0.7 8 57.3 22.3 Pulp DP 1056 100 0 90 °С, 30 min 1.7 10 — — Mixture 44.2 31.8 90 °С, 30 min 1.0 1 — — Pine 44.2 31.8 175 °С, 30 min 0.4 2 55.9 32.4 Pretreated pine 56.9 30.3 175 °С, 30 min 1.7 13 63.2 30.6 Reproduced from [11 Sun]

to help in the filtration of the dissolved substances. Later, the dissolved cellulose was added into dry methanol and stirred at 300 rpm and 40 °C for 10 min to regenerate the cellulose. About 16 % cellulose from pine and 11 % of cellulose were reported to be regenerated from pine and eucalyptus, respectively [13Cas].

References

[11Sun] Sun, N., Li, W., Stoner, B., Jiang, X., Lu, X., Rogers, R. D.: Green Chem. 13, 1159 (2011)

[13Cas] Casas, A., Alonso, M. V., Oliet, M., Santos, T. M., Rodriguez, F.: Carbohydr. Polym. 92, 1946 (2013)