High consistency mechano-enzymatic pretreatment for kraft fibres: effect of treatment consistency on fibre properties

Jenni Rahikainen,Stina Grönqvist,Outi Mattila,Anna Suurnäkki,Kristiina Kruus,Thaddeus Maloney,Ville Lovikka

doi:10.1007/s10570-020-03123-8

Abstract

Fibre reactivity is essential for cellulose dissolution and derivatisation and a porous fibre structure is one key determinant for a highly reactive pulp. Mechanical and enzymatic treatments are known to improve fibre reactivity and more recently, the combination of mechano-enzymatic treatment has been shown to synergistically enhance the beneficial effect. The aim of this work was to do a systematic study on the effect of dry matter content during enzymatic modification of fibres and define the conditions that optimally improve fibre porosity. The combined mechano-enzymatic treatments at 15–25 w% consistency had the most pronounced effect on fibre porosity and morphology analysed by solute exclusion technique, nitrogen sorption and scanning electron microscopy. Light microscopy imaging confirmed that the combined mechano-enzymatic treatment at high consistency (> 10 w%) resulted in extensive fibrillation of the treated fibres which was not observed after sole mechanical or enzymatic treatments.

Highlights

Environmental concerns have raised interest in products made of renewable raw materials in a sustainable manner
The effect of mechanical treatment (M) on fibre properties was studied after mixing softwood kraft pulp in a farinograph mixer at three consistencies 10%, 20% and 30% (w/w)
The higher the dry matter during mixing the more pronounce was the effect on the molecular weight (Mw) and viscosity of the pulp

Summary

Introduction

Environmental concerns have raised interest in products made of renewable raw materials in a sustainable manner. The most abundant biopolymer on the Earth has versatile properties for various material applications. Utilisation of cellulosics, especially in the areas of textiles and cellulose derivatives, has been an active area of research. Compared to the volumes in paper and board manufacture, the use of cellulose in high-value products is still low. Improved accessibility and reactivity of cellulosic fibres for dissolution and chemical modifications would enable the use of cellulose in a wider scale. Harsh chemistry is used for cellulose dissolution and modification and environmentally benign fibre pretreatments that improve the accessibility and reactivity of cellulose would enable the development of processes with more sustainable solvent systems

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