Lyocell fibers for textile processing derived from organically grown hemp

Abstract

Because of world-wide persistent demand for cellulose man-made fibers suitable in textile processing and application and the predicted stagnation of cotton production, there is a strong need for innovative approaches to safeguard the future availability of dissolving pulps for cellulose fiber production. The paper will present the results of a national network project, which was focused on the development of an integrated process chain for the manufacturing of novel fabrics produced of man-made Lyocell fibers derived from organically grown hemp (OG hemp). The whole process line was established within the process studies starting from hemp cultivation, machine-aided harvesting and automatic peeling to isolate hemp bast stripes (HBS) from stems, pulp manufacturing and transfer into fibers by solution spinning up to processing to yarns and dyed and finished fabrics.More representative, the paper will specifically describe the transfer of almost free of shives extracted, retted hemp fibers and dried HBS into dissolving pulp by means of a specific adjusted pulp cooking process. The main challenges in that step were identification as well as practical development of suitable process approaches for degumming, DP adjustment and purification from contained light and heavy metal traces. Furthermore, the pulp had to be assessed for its usability in direct dissolution process. For that purpose dopes were prepared and characterized regarding optimal DP adjustment, the insoluble parts in dopes and the thermal dope stability at elevated temperatures. After identification and application of most favored process parameters the dissolved pulps could be converted into Lyocell fibers by solution spinning applying the most suitable dry-wet shaping procedure conditions. Manufactured fibers exhibit comparable properties in fineness, tensile strength, elongation and loop tenacity like common Lyocell fibers made of conventional wooden pulp. In project R&D activities obtained fibers had been further processed into yarns, fabrics and apparel demonstrators applying conventional processing parameter. The manufactured LyohempTM clothes offer excellent product qualities as well as wearing properties.