Dissolving-grade pulp and lyocell fibers prepared from cotton stalks

Abstract

Dissolving-grade wood pulp is one of the crucial raw materials to produce lyocell fiber. Benefit from the environmentally friendly production process of lyocell spinning and excellent comprehensive performance of lyocell fiber, the lyocell fiber’s industrialization has been rapidly developed in recent years. Limited to the shortage of wood resources, the development and expansion of alternative non-wood pulp raw materials are quite important and valuable. Herein, newly dissolving-grade pulp was developed from cotton stalks (CSs) by alkali pretreatment, kraft cooking and following post processing procedures. From orthogonal experiments, it was found that the factors affecting Kappa number and degree of polymerization (DP), from strongest to weakest, were cooking temperature, alkali dosage, cooking time, and sulfidity. Three preferred cooking schemes (A₃B₃C₃D₃, A₃B₃C₃D₁ and A₂B₃C₃D₃) were developed to prepare the final dissolving-grade CS pulp (CSP) with DP of 466, 522, and 568. FT-IR spectroscopy and the related component analyses showed that hemicellulose was substantially removed during the pretreatment process, and lignin was substantially removed during the cooking process. The corresponding dissolution and spinning experiments further illustrated that all the three kinds of dissolving-grade CSPs had good dissolution ability and spinning stability. The mechanical performance of the corresponding lyocell fibers was improved as the rising of pulp DP. Also, the CSP568 induced by a more appropriate cooking scheme showed quite similar dissolving properties, lyocell spinnability and lyocell fiber performance to that of the commercial wood pulp. Related explorations are expected to expand the high value and green utilization of crop residues and the material sources for dissolving-grade pulp, thus promoting the development of lyocell fiber industrialization.

Graphical abstract