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Issue 05/2017

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Fibres & Textiles Stable

Fibres & Textiles Stable ring spinning process for PLA staple fibre yarns This article presents the current state of the project SPEY which aims to establish poly lactic acid (PLA) staple fibre yarns in home textiles or in technical applications using a methodological approach and process analysis. The goal of the performed process analysis is the avoidance of degradation phenomena during the ring spinning process. At the current state of the project, Ring spinning yarn of 100 % PLA was successfully produced. A production speed of v pr = 23 m/min combined with a twist factor of α m = 100 T/m lead to a stable process without yarn breakage. The resulting yarn count is T t = 25 tex. This article provides an overview of the results from the ring spinning trials with experimental PLA filaments and presents optimised production parameters for the stable production of 100 % PLA ring spinning yarn. Introduction Currently, Europe consumes more than 6 million tonnes of textile fibres 34 % for clothing, 27 % for housing and carpeting, 38 % for other industrial technical usages [1]. The European textile and clothing industry has a longstanding tradition of leadership in terms of innovation, fashion and creativity. Even though the European textile and clothing industry increasingly encounters fierce global competition and significant relocation of manufacturing to low-wage countries - with 165 billion EUR turnover - it continues to represent one of Europe’s major industrial sectors [2]. Today, the European textile industry is challenged to make a radical shift towards innovative and high-value added products to counter the competition with low-wage countries. At the same time, European industry is looking to find links to the environment-concerned customers via the increased use of renewable and recyclable as well as recycled materials. PLA is at the moment produced from starch (corn) or from sugar (sugarbeet). The fibre products are highly smooth and completely non-irritating to the skin, while being 100 % biodegradable and compostable. PLA staple fibres are a possible alternative as a substitution of existing synthetic fibre products. The replacement of oil based polymers by biobased alternatives is a topic that is regarded with high priority in textile innovation programs. PLA offers additional end-of-life possibilities. It is known and demonstrated that PLA can be recycled via melt processing and due to the low melting temperature and the limited water-uptake the process has a low cost and offers high quality products. Also hydrolysis to feedstock (monomers) is possible. In contrast with most oil based polymers, PLA can be composted or used in biogas installations. At medium term, the market potential is estimated to the production of 40,000 t/a for PLA and PLA blended yarns with a volume of appr. 140 Million EUR/a all over Europe when comparable properties of existing yarns are reached. Moreover, there’s not much oil occurrence in Europe but enough area for cultivable land for food and crop for technical use. The industry of agriculture and forestry are offered alternative production and income possibilities. The project Spun EcoYarn (SPEY, AiF Cornet 153 EN) contributes to a greener environment. Depending on the crop used 3.3 up to 6 tonnes of PLA can be produced per hectare crop yield. This is very efficient compared to the production of about 1 tonne of cotton per hectare. During 2012, 190,000 tonnes of PET fibres were produced just in Germany [3]. The total energy consumption to produce PLA is about 50 % lower than for PES (Fig 1., top) and as a consequence also the total emission of greenhouse gases is about 60 % lower for PLA than for PES (Fig. 1, bottom). SPEY aims to establish poly lactic acid (PLA) staple fibre yarns in home textiles e. g. upholstery fabrics, bedding textiles, matrass thickening, in technical applications e. g. work wear and medical textiles using a methodological approach and process analysis, with the goal of avoiding degradation phenomena. The aim of this project is to develop the technology and expertise to economically produce PLA based spun yarns and blended spun yarns with properties comparable to existing PET alternatives. It is targeted to develop in commercially available conditions, high quality bio-based spun yarns with a high durability (long life time). To reach this goal the polymer recipe is modified by additives and process parameters for melt spinning as well as end spinning for high quality yarns are defined. Implementation Aim of the current work package within the SPEY project is the production of staple fibre yarns of commercially available PLA and of experimental PLA by Centexbel. Also, spinning methods for processing PLA are optimised and PLA staple fibre yarns with improved properties are developed. PET (Table 1) based ring yarns will be the benchmark for the development of the PLA staple fibre yarns. The main target is to reach a breaking tenacity in the range of 16 – 30 cN/tex [5]. The experimental PLA filaments are cut and texturated at the user committee member (UCM) of the company Barnet Europe GmbH & Co. KG, Aachen, Germany. Spin finish application is performed by the UCM Bozzetto GmbH, Krefeld, Germany. At ITA the fibres are processed into a sliver and send to the UCM member Schlafhorst, branch office of Saurer Germany GmbH & Co. KG, for ring spinning. 18 bioplastics MAGAZINE [05/17] Vol. 12

Fibres & Textiles By: Vadim Tenner 1 , Marie-Isabel Popzyk 1 , Yves-Simon Gloy 1 , Raf Van Olmen 2 , Thomas Gries 1 1 Institut für Textiltechnik der RWTH Aachen University, Aachen, Germany 2 Centexbel, Gent, Belgium Fig. 1: Energy consumption and greenhouse gas emission of PLA and PET [4] 100,00 80,00 60,00 40,00 20,00 0,00 Production energy consumption in MJ/kg PES -50% PLA PLA PES 4,00 3,00 2,00 1,00 0,00 100,00 100,00 Results 80,00 60,00 In the following, the results from the laboratory 40,00 analysis 20,00 of the produced ring spinning yarns 0,00 of 0,00 100 % PLA are presented. The used batch PES PES PLA PLA of experimental PLA was not applied with an additional spin finish since spinning trials showed no necessity for a second spin finish. Stable spinning processes for ring spinning are achieved and a factorial design is carried out. Fibre properties after different processing steps are shown in Table 2. The laboratory results show, that the produced sliver contains fibres of 35.99 ± 10.41 mm length. The PET fibres, which are the benchmark, have a 3-times as high tenacity F t = 76.61 cN/tex and only half the elongation at break ε b = 18.55 %. Ring spinning 80,00 60,00 40,00 20,00 Production energy energy consumption in MJ/kg in MJ/kg Ring spinning is performed using a 100 % PLA sliver. The machine settings including a factorial design are shown in Table 3. The ring spinning results have high standard deviations due to manual spinning preparation and no significance is discernible. Owing to limited fibre amounts of around 4-8 kg of each batch an industrial carding machine is not suitable and a laboratory carding machine has to be used. This laboratory carding machine only produces nonwovens and no slivers. The non-wovens are folded to slivers of1 m and a weigth of 30 g. Due to this discontinuous process the sliver pieces have to be joined. Especially within its connecting areas, thick and thins places occur in the final sliver. An autoleveller gillbox can limit thin and thick places in a sliver to a certain amount but the unevenness in the slivers is too high for the autoleveller gill to fully reconcile it. Due to the manual spinning preparation, two rovings were fed in simultaneosly into the drafting unit, in order to increase the evenness of the sliver. The trials were carried out in an air-conditioned hall at a room temperature of T = 25 °C and a relative humidity of ρ = 47 %. Within the trials, it was proved that ring spinning yarn with 100 % PLA is possible at v pr = 10 m/min. Frequent yarn breakage and no stable ring spinning process occurred at a production speed of v pr = 15 m/min and the twist factor α m = 80 T/m. PLA PLA PES PES 4,00 4,00 3,00 3,00 2,00 2,00 1,00 1,00 0,00 0,00 Table 1: Properties of cotton and PES as benchmark Specific gravity [g/cm³] Tenacity [cN/tex] Moisture content [%] Melting point [°C] Elastic recovery [5 % strain] Cotton 1.39 45 – 55 0.2 – 0.4 255 – 265 65 PES 1.52 20 – 40 7 – 8 - 52 Table 2: Fibre properties of Batch 03 after different processing steps Processing step Staple fibre length L sf [mm] Tenacity F f [cN/tex] Elongation at break ε b [%] Filament - 27.94 ± 5.44 40.34 ± 10.41 Cut/crimped 41.53 ± 5.57 23,95 ± 5.15 38.81 ± 13.04 Sliver (carding) 35.99 ± 10.41 24.45 ± 5.75 39.16 ± 10.18 Table 3: Machine and processing parameters for ring yarn from batch 03 (factorial design) Machine Zinser Impact 72 Ring traveller HEL 1 hr EMT SS 1/0 Production rate [m/min] 15 20 25 Twisting factor α m [T/m] 80 100 80 100 80 100 Yarn count T t [tex] 24.8 21.2 24.05 24.4 - 28.2 Tenacity F f [cN/tex] 12.16 12.96 13.78 12.6 - 10.8 Elongation ε [%] 21.3 21.8 22.7 21.6 - 21.6 Evenness CVm Production greenhouse gas gas in CO in 2 CO eg./kg 2 eg./kg PES PES -60% PLA PLA [%] 21.2 23.2 20.2 20.7 - 19.4 Hairiness H - 10.76 8.99 - 8.14 - 8.26 PLA PLA PES PES bioplastics MAGAZINE [05/17] Vol. 12 19

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