Polyurethanes Melt
Polyurethanes Melt spinning of CO 2 -based thermoplastic polyurethanes An environmentally friendly approach for the production of elastic yarns T he market of elastic yarns has grown massively over the past years, mainly driven by applications in apparel, sports, and medical textiles. For example, approx. 80 % of all currently circulated apparel textiles contain elastic yarns to provide stretch and comfort. Most of these elastic yarns are produced by dry spinning of thermoset polyurethanes (PU) which causes specific challenges: Production is slow as well as expensive and potentially hazardous solvents have to be used. These challenges may be overcome by switching from dry to melt spinning processes. Thermoplastic polyurethanes (TPU) fulfil the needs of high elasticity and melt spinnability. Additionally, the greenhouse gas CO 2 can be used as one of the resources for TPU production. By this, “Carbon Capture and Utilization” (CCU) can be applied to the textile industry. Motivation: CCU, High Economic Efficiency and Improved Processability TPU are linear and basically structured in hard and soft segments. Soft segments are typically polyols while hard segments are composed of isocyanates and a chain extender [1, 2]. There are three major categories of polyols being applied: polyether, polyester, and polycarbonate polyols [3]. Specific polyols offer a huge potential for increasing the sustainability of TPU. Over the past years and decades, large efforts have been made to enable the use of renewable materials for (thermoplastic) PU production. For example, biobased polyols have been derived from vegetable oils [4, 5]. Besides these biobased approaches, the incorporation of CO 2 as a resource is eligible for the production of polyols. Covestro AG (Leverkusen, Germany) has developed a process for the production of polyether-polycarbonate PU, based on CO 2 containing polyols. The technology involves the reaction of epoxide with CO 2 under the application of selective catalysts. [6] Figure 1: Mission Statement of “CO2Tex” The approach of Carbon Capture and Utilization (CCU) does not only provide the opportunity for the circulation of CO 2 with positive environmental aspects but also offers economic advantages. Allied Market Research (Portland, Oregon, USA), estimated the market volume of elastic filaments to be USD 10.5 billion in 2022, starting from USD 5.8 billion in 2015. This corresponds to a CAGR of 8.8 % over the past seven years. [7] Roughly 80 % of this market is currently being supplied by dry-spun yarns, whose production requires the use of solvents such as dimethylformamide (DMF) [8, 9]. Melt-spun CO 2 -based TPU-filaments can be expected to be 50 to 60 % lower in price than conventional solution-spun PU filaments [10]. The main reasons for this economic advantage can be found in processes as well as facilities. Generally, lower winding speeds of 500 to 2,000 m/min can be achieved in dry spinning in comparison to up to 6,000 m/min in melt spinning [11]. For TPU, melt spinning processes with a winding speed of 2,500 m/min have already been developed on pilot scale [10]. Additionally, solvent evaporation in dry spinning processes is energyintensive but does not need to be applied for melt spinning processes [11]. The main obstacle to the wide use of melt-spun TPU is the strong tackiness of these yarns which especially hampers the unwinding from spools and transport through the machines for fabric production. To reduce this tackiness, different approaches are being developed, investigated, and evaluated in the research project CO 2 Tex. The Research Project CO 2 Tex RWTH Aachen Institut für Textiltechnik (ITA) (Aachen, Germany) is currently conducting the publicly funded research project CO 2 Tex in cooperation with the funded partners W. Zimmermann (Weiler-Simmerberg, Germany), medi (Bayreuth, Germany), Schill+Seilacher (Böblingen, Germany), Oerlikon Textile (Remscheid, Germany), Carbon Minds (Köln, Germany) and adidas (Herzogenaurach, Germany). The Target of this project is the establishment of commercially viable elastic filament yarns made from CO 2 -containing TPU. At the end of the project, these yarns should be processed as easily as possible in existing industrial plants into textile pre – and end products. For the development of at least one stable and reproducible melt spinning process, modifications are made to spinning plants. These modifications include the investigation of spinnerets, filament cooling, godet surfaces, as well as winding technology. Additionally, spin finishes are adapted to the process and tested. All developments are scaled up from pilot to industrial scale. If the production of suitable yarns is possible, the process chain for the production of 48 bioplastics MAGAZINE [02/22] Vol. 17
By Jan Thiel, Henning Löcken, Lukasz Debicki, and Thomas Gries RWTH Aachen Institut für Textiltechnik Aachen, Germany sports and medical textiles is investigated and adapted. This includes the processes of covering, knitting, and finishing. Finally, the use of TPU yarns containing CO 2 is evaluated ecologically as well as economically and compared to conventional dry-spun yarns. The mission statement of CO 2 Tex is displayed in Figure 1. After a first benchmark definition, first melt spinning trials are about to start at the ITA on pilot and technical scale before being upscaled to industrial scale at Oerlikon. Acknowledgement The authors would like to thank the German Federal Ministry of Education and Research for funding the research project within the innovation space BioTexFuture (funding code: 031B1207A). Bibliography [1] Fabricius, M.; Gries, T, Wulfhrost, B.: Fibre Tables: Elastane Fibres (spandex) Frankfurt am Main, Schwenk & Co. GmbH, 1995 [2] Prisacariu, C.: Polyurethane elastomers: From morphology to mechanical aspects. Wien [a.o.]: Springer, 2011 [3] Zhu, R.; Wang, Y.; Zhang, Z.; Ma, D.; Wang, X.: Synthesis of polycarbonate urethane elastomers and effects of the chemical structures on their thermal, mechanical and biocompatibility properties. Heliyon 2 (2016), pp. 1-17 [4] Javni, I.; Petrović, Z.S.; Guo, A.; Fuller, R.: Thermal stability of polyurethanes based on vegetable oils. Journal of Applied Polymer Science 77 (2000), No. 8, pp. 1723-1734 [5] Lligadas, G.; Ronda, J.C.; Galià, M.; Cádiz, V.: Oleic and undecylenic acids as renewable feedstocks in the synthesis of polyols and polyurethanes. Polymers 2 (2010), No. 4, pp. 440-453, doi:10.3390/polym2040440 [6] Gürtler, C.: “Dream production” : CO2 as raw material for polyurethanes. Brussels, 07.06.2013 [7] Allied Market Research: Spandex fibre market by type of production method and application – global opportunity analysis and industry forecast, 2014-2022. Pune, India, 2016: URL www.alliedmarketresearch.com/spandexfibre-market , Accessed on March the 09th, 2022 [8] Koslowski, H.-J.: Chemiefaser-Lexikon. Begriffe – Zahlen – Handelsnamen. 12. erw. Auflg.: Frankfurt am Main: Deutscher Fachverlag GmbH, 2008 [9] Gries, T.; Veit, D.;Wulfhorst, B.: Textile Fertigungsverfahren: Eine Einführung. München: Carl Hanser Verlag, 2014 [10] Manvi, P.: Melt spinning of carbon di-oxide based thermoplastic polyurethane. Aachen [Diss.], Shaker, 2018 [11] Gupta, V.B., Kothari, V.K. (Eds.): Manufactured fibre technology London [u.a.]: Chapman & Hall, 1997 Polyurethanes www.ita.rwth-aachen.de 23–25 May • Siegburg/Cologne 23–25 May • Siegburg/Cologne (Germany) renewable-materials.eu The brightest stars of Renewable Materials The unique concept of presenting all renewable material solutions at one event hits the mark: bio-based, CO2-based and recycled are the only alternatives to fossil-based chemicals and materials. ORGANISED BY NOVA-INSTITUTE SPONSORED BY COVESTRO1 RENEWABLE MATERIAL OF THE YEAR 2023 First day • Bio- and CO2-based Refineries • Chemical Industry, New Refinery Concepts & Chemical Recycling Second day • Renewable Chemicals and Building Blocks • Renewable Polymers and Plastics – Technology and Markets • Innovation Award • Fine Chemicals (Parallel Session) Third day • Latest nova Research • The Policy & Brands View on Renewable Materials • Biodegradation • Renewable Plastics and Composites INNOVATION AWARD Call for Innovation Submit your Application for the “Renewable Material of the Year 2023” Organiser Award Sponsor Contact Dominik Vogt Conference Manager dominik.vogt@nova-institut.de bioplastics MAGAZINE [02/22] Vol. 17 49
