Effects of Caustic Extraction on Properties of Viscose Grade Dissolving Pulp

Viscose, a cellulose-based commodity fibre, is produced by pulping and bleaching of wood, yielding a high quality “dissolving pulp” which is then spun. During pulping and bleaching, effective hemicellulose extraction is required to allow fibre production. We present a design of experiments (DoE) approach to optimise caustic extraction in a total chlorine free (TCF) bleaching sequence (O-CE-Z-P) of beech wood sulphite pulp. Temperature and sodium hydroxide concentration were varied to identify highest xylan extraction yield, and a maximum xylan removal of 83% was achieved at 20 °C and 120 g/L NaOH. Additionally, caustic extraction conditions were derived from the DoE model that led to pulps with high yield, high alpha cellulose content or uniform cellulose molecular weight distribution. Pulps from verification experiments exhibited good reactivity in viscose application tests. Hence, the presented O-CE-Z-P bleaching sequence can be considered as suitable for integrated viscose fibre production. We assume that the presented caustic extraction model will be useful for pulp and biorefinery researchers who work on caustic biorefinery processes involving hardwood feedstocks.

Research on the Qualities of Cellulosic Yarn

Cellulosic fibre is a kind of renewable fibre that has attracted more and more attention in textile processing recently. Yarn spinning is the first fundamental process in textile processing. Therefore, in this paper, taking viscose fibre and tencel fibre as examples, the qualities of cellulosic yarn were studied. Three kinds of pure viscose and tencel yarn: 14.6 tex (40S), 9.7 tex (60S) and 7.3 tex (80S), were spun on a ring spinning system modified with lattice apron compact spinning (LACS) and complete condensing spinning (CCS), respectively. The spun yarn qualities, yarn evenness, breaking strength and hairiness, were tested and comparatively analysed. Then two kinds of cellulosic blend yarn including 14.6 tex, 9.7 tex and 7.3 tex JC/R 60/40 yarn, and 14.6 tex, 9.7 tex and 7.3 tex JC/T 70/30 yarns were spun on a ring spinning system modified with CCS. The spun yarn evenness, breaking strength and hairiness were tested, and the cross sections of the spun yarns were presented using a Y172 Hardy’s thin cross-section sampling device. The results show that for both the pure viscose and tencel yarn, compared with LACS, CCS has better yarn evenness, a little lower yarn breaking strength and a little more hairiness, while the uniformity of yarn qualities are all improved. For the cellulosic blend yarn, compared with the pure cellulosic yarn, yarn evenness is worse, especially for the cotton and tencel blend yarn.