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Green chemicals and technologies for the wood-to-textile value chain

Periodic Reporting for period 3 - GRETE (Green chemicals and technologies for the wood-to-textile value chain)

Reporting period: 2022-05-01 to 2023-04-30

The GRETE project tackles the increased global demand for sustainable textile fibres by offering new technological breakthroughs for the wood-to-textile value chain. Production and use of man-made cellulosic fibres are estimated to grow steadily in the future, partly as a reaction to sustainability issues related to cotton: although cotton is a renewable resource, its cultivation requires irrigation water, arable land, fertilizers and pesticides that increase its negative environmental impact
Currently the raw material base for the production of man-made cellulose fibres from wood is limited. GRETE introduced technologies that enable the use of paper grade pulps from softwood and hardwood as raw materials for man-made textile fibres. The use of standard paper-grade wood pulp for cellulosic fibre production results in lower environmental impact and reduced production steps.
The common solvent systems for commercial man-made cellulosic fibres are far from optimal being based on toxic and explosive chemicals. In GRETE, innovative green chemicals for man-made cellulosic fibres manufacturing that are based on novel liquid salts were developed. The GRETE solvent system increases safety, sustainability and economic viability of a bio-based textile fibre production.
Textile production and finishing typically involve numerous wet processes, even when using commercial man-made cellulosic fibres. However, the GRETE project has developed innovative treatments that can be applied to the pulp or to the spun fibre, resulting in high-quality man-made cellulosic textile fibres with customized properties that can withstand water-scarce finishing treatments. By adopting these novel techniques, the textile industry can reduce its environmental impact significantly and become more sustainable.
GRETE developed novel superbase ionic liquids (ILs) that perform excellent in dissolution of wood pulps and are stable in conditions required for recycling of the solvent in the fibre production process. Furthermore, the target was to find ILs that can be synthesized economically from inexpensive and available starting materials and that can be safely used in the wood-to-textile value chain. During the project, three novel non-toxic superbase IL structures were synthetized with good properties for textile fibre spinning meaning good cellulose dissolution power and good stability for recycling.
Spinning of textile fibres from paper-grade pulp requires a pretreatment to enable preparation of a spinnable dope. The aim of the pretreatment step was to lower the degree of polymerization of cellulose in the pulp to enable subsequent pulp dissolution in high yield to enable a spinnable dope with high cellulose content. In GRETE, four pretreatments were tested and finally two of them, mild sulfuric acid pretreatment and enzymatic pretreatment with endoglucanase, were thoroughly analysed in textile fibre production. Two types of paper grade pulp, bleached eucalyptus kraft pulp from Portugal and bleached softwood kraft pulp from Finland, were used..
Chemical functionalisation of the final regenerated fibres was tested by developing chemical modifications for the pulp raw materials.
The GRETE project demonstrated successfully that textile fibres with good mechanical properties can be spun using pre-treated paper grade pulps from eucalyptus and softwood paper grade pulps. A dissolution method was developed where it was possible to avoid drying of the pulps after pretreatment, and dissolve wet pulps into novel superbase ionic liquid. In GRETE with the optimized dissolution and spinning procedures for high hemicellulose kraft pulps, it was possible to improve the fibre tenacity up to over 10 cN/dtex without impairing elongation (>10%). Additionally, it was shown that regenerated fibres from pretreated kraft pulps had comparable mechanical properties with fibres from dissolving grade pulp.
Chemical post-treatments were developed for regenerated textile fibres to enhance the performance of man-made cellulosic textile fibres.
In GRETE a novel hemicellulose characterization method based on immunolabelling of xylan was successfully developed for regenerated fibres and the results suggest that xylan is not only found from the surface of the regenerated fibres but is also distributed throughout the fibre structure.
Efficient recycling of the ionic liquid solvent is a prerequisite for an economically viable textile fibre process. The recovery and purification of superbase ionic liquids (IL) from the spinning bath using different approaches was evaluated. The results demonstrate that aqueous two-phase system separation method can be considered as a way to remove water. The results also showed that the liquid-liquid extraction method can be improved by using parallel structure, with both solvents showing similar efficiency.
Two of GRETE concepts showed higher profitability compared to the reference concept (Lyocell) suggesting that textile fibre production using ionic liquids and paper grade pulp can be economically viable.
Environmental impacts of the selected GRETE concepts were assessed by following a Cradle-to-Gate LCA approach using mass and energy balance data generated by the simulation model. The results of the assessment showed that a textile fibre production concept utilising eucalyptus paper grade pulp and ionic liquid as solvent led to the most competitive environmental performance. The GRETE concepts were analysed also from a social and socioeconomic perspective. The results showed that the same concept that was competitive from environmental perspective was also the most effective in terms of generating social value.
The GRETE project has resulted in 3 master theses, 5 peer revied publications, 3 manuscripts that are under review in peer-review journals. In addition to these papers, 5 more manuscripts are currently under preparation. These papers contain the scientific novelty of the project that spans from novel ionic liquid structures to the techno-economics of man-made cellulosic textile fibres. The partners have introduced the GRETE project in 51 onsite or online events, including 17 oral and 16 poster presentations that have been given based on GRETE results. Also, events targeted for the Stakeholder Group (SHG) have been organized.
GRETE has revolutionized the cellulosic textile fibre field by introducing solid evidence that the use of superbase ionic liquids as solvent enable the use of hemicellulose-rich paper grade pulp as raw material for textile fibre production.
The scientific work carried out in GRETE shows novelty and scientific progress. For instance, the developed superbase structures are not commercially available nor known in the literature.
New information concerning the enzymatic modification of kraft pulps, recycling of the superbase ILs have been obtained that pave the way for industrial exploitation of the technologies.
The technologies defined in the GRETE project widen the raw material base for man-made cellulosic fibres manufacturing while increasing safety and economic viability of a sustainable wood-to-textile value chain. The industrial exploitation of the achieved results is expected to happen throughout the next decade.