Effects of Caustic Extraction on Properties of Viscose Grade Dissolving Pulp

Cindy Friebel,Ireen Gebauer,Gabriele Schild,Karin Fackler,Robert Bischof

doi:10.3390/pr7030122

Abstract

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.

Highlights

Every year 100 million tons of fibres are produced globally to make textiles and technical products that serve human well-being
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
Dissolving pulp in outstanding purity was obtained from sulphite beech pulp by application of an O-CE-Z-P bleaching sequence

Summary

Introduction

Every year 100 million tons of fibres are produced globally to make textiles and technical products that serve human well-being. Less than half of these fibres are currently made from renewable resources such as cotton or wood [1]. Wood as raw material for cellulose fibre production is beneficial in terms of reduced irrigation water requirements and ecotoxicity, as compared to cotton [1]. Wood chips are initially converted to “brown-stock” pulp using either the kraft or the sulphite process that remove a high amount of non-cellulosic wood constituents such as hemicellulose and lignin. The pulp is further purified by a suitable sequence of bleaching stages to the dissolving pulp quality required by the respective fibre process [3,4]. Dissolving pulp is a type of pulp having a high cellulose content (>90%), high purity, brightness, cellulose reactivity, and a uniform molecular weight distribution [3]

Methods

Results

Conclusion