Influence of pulp characteristics on the properties of alkali cellulose
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ORIGINAL RESEARCH
Influence of pulp characteristics on the properties of alkali cellulose Catharina Fechter Thomas Heinze
. Steffen Fischer . Felix Reimann . Harald Brelid .
Received: 3 December 2019 / Accepted: 6 April 2020 Ó The Author(s) 2020
Abstract Alkali extraction of cellulose material is a common treatment for several industrial processes— especially the viscose process, which produces fibers for textile applications. This study investigated different generic dissolving wood pulps by means of alkali extraction (10–18 wt% aq. NaOH at 20–50 °C). The regenerated residue of the pulps was characterized for its chemical composition, molecular structure, and cellulose conformation. The investigated pulps had in common that glucan was most intensely extracted at low temperature and low concentration of aqueous alkali, xylan was most intensely extracted at high temperature and high concentration of aqueous alkali, and mannan was most intensely extracted at a concentration of aqueous alkali [ 14 wtwt% at all temperatures applied. The degree of transformation via alkali cellulose to cellulose II as determined with
Raman spectroscopy was found to be maximized for all pulps at high alkali concentration and temperature had no major influence. Maximum yield for all investigated pulps was found when extraction was done with 18 wt% aq. NaOH. The importance of temperature differed for the investigated pulps. The reason for the differences in extraction behavior or different absolute levels of resulting properties was found to be related to differences in the homogeneity and purity of the pulps. A conclusion of interest for industrial applications was that extracting the pulps with 18 wt% aq. NaOH led to an optimal alkalization result for yield, purity, and conversion. The steeping temperature chosen was found to be important to balance the yield and the purity of xylan-containing pulps.
C. Fechter (&) T. Heinze Center of Excellence for Polysaccharide Research, Institute of Organic Chemistry and Macromolecular Chemistry, Friedrich-Schiller-University of Jena, Humboldtstraße 10, 07743 Jena, Germany e-mail: [email protected] S. Fischer F. Reimann Wood and Plant Chemistry, Technische Universita¨t Dresden, Pienner Str. 19, 01737 Tharandt, Germany H. Brelid So¨dra Skogsa¨garna Ekonomisk Fo¨rening, 43286 Va¨ro¨backa, Sweden
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Cellulose
Graphic abstract
Keywords Dissolving wood pulp Viscose Alkalization Raman Lattice transformation R18
Introduction The demand for viscose fibers is increasing because of the increase in world population, prosperity as well as demand for fashion and other related consumer products. More than 90% of today’s seven million tons of viscose fiber are produced using dissolving pulp derived from wood (DWP). Accordingly, this increasing demand is met by an extension of global DWP capacity. This capacity has almost doubled from 2008 to 2018 (Young 2018). The first process step in producing viscose is the alkalization (steepi
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