Enzymatic pulp modification: an excellent way to expand the raw material base for Lyocell applications?

The potential of enzymatic modification procedures was studied to adjust pulp properties for Lyocell process applications. Cellulases with well-defined activity compositions were identified and tested for pulp treatment. The changes of the pulp properties by such biotechnological modification were investigated especially concerning the resulting average degrees of polymerisation (DP) and the molecular weight distributions (MWD). Several industrial cellulases catalysed endo-splitting on solid cellulose. The selected compositions of the tested enzymes effected the intended decrease of the cellulose DP as suitable adaption of the MWD as well as an improvement of the pulp solubility in NMMO. The DP reduction of tested pulp qualities (paper, viscose and plant pulps) reached 20–35% related to the DP of initial pulp. Depending on the used pulp quality, different changes of the molecular weight distributions with increase or decrease of the polydispersities were detected. Because of improved pulp solubility, spinning dopes with excellent solution qualities could be obtained, even when paper pulps with lower α-cellulose were applied. Exemplary, softwood TCF paper pulp was tested for upscaling in staple fibre. Also filament spinning could be successfully carried out. The prepared fibre samples showed good textile-physical properties. Enzymatic treatment could have a great potential for expansion of raw material base in Lyocell process. It could cause cost savings by applying cheaper cellulose pulps. It also provides options for use of alternative pulps from recycled textile fabrics or annual plants, outside of wood or cotton.