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bioplasticsMAGAZINE_1101

Basics others tanning

Basics others tanning agents spud mud cement mineral color dyeing factory dust binder paper additive pesticides chipboard building stones concrete coal briquets animal food 0 10 20 30 40 part of application (%) Figure 5: Applications of lignosulphonates [10] Figure 7: Printed circuit wiring board (green card) from lignin containing epoxy resin [15] Figure 8: EcoPump (Gucci) with heel made from Arboform combination of the methanol and sodium hydroxide routes. The application of acidic agents, especially organic acids like acetic and formic acid, is characteristic for the Acetocelland Formacell processes. The Milox procedure additionally uses oxidants such as hydrogen peroxide in combination with formic acid for lignin degradation. In recent years biorefinery concepts have become most popular. In the context of lignin sourcing, biorefineries using lignocellulose feedstock for cellulose bioethanol production (2nd generation bioethanol) could play an important role in providing sulphur-free and structurally tailored lignins. A current example is provided by the Canadian company Lignol, which is running a biorefinery ready for commercialisation based on the Alcell process [7]. The three main products of wood pulping, i.e. cellulose, lignin, and mixed sugars are converted to fuel ethanol, HP-L TM lignin, and thermal energy, respectively. Larger biorefinery projects for lignocelluloses with a focus on the valorization of lignin have also been set up in the Netherlands (LignoValue [8]) and Germany (CBP Leuna [9]). Applications Lignin is mainly used as an energy supply for the processes run in the pulp mills. However, roughly a million tonnes per year is sold in the form of lignosulphonates for the various applications shown in Fig. 5. The actual uses of isolated lignins apart from lignosulphonates are at a much lower, often pilot scale, level and can be divided into three main categories – energy, materials, and chemicals. Pellets made from lignin can be used as a solid fuel analogous to wood pellets but with a much higher calorific value, as demonstrated with lignin from the LignoBoost process [11]. An example of the use of lignin as a substitute of phenol in phenol-formaldehyde resins is provided by Protobind TM , a sulphur-free lignin from annual plants (10,000 tonnes/a [12]). With the tendency to higher phenol prices, the use of lignin can be an economically viable biobased alternative. The properties of such thermosets and composites loaded with 20-30% of sulphur-free lignin are comparable or marginally better than those of the standard materials as demonstrated by the Dynea company [13]. Similar effects can be anticipated for resins of the same group, i.e. amino and melamine resins. Indulin AT is a commercial Kraft pine lignin from MeadWestvaco and is ideal for use in a wide range of polymeric applications where solid dispersants or adsorption properties are required [14]. In the nineteen-nineties IBM developed a ‘green-card’ (Fig. 7), a printed wiring board made from an epoxy resin containing up to 60% of lignin [15]. Although there was an 56 bioplastics MAGAZINE [01/11] Vol. 6

Basics advanced product development market transfer was not accomplished. A lot of attempts have been made to use lignin as polyols for polyurethanes (PU) [16]. Depending on the PU-forming isocyanates, the material properties range between very brittle and soft. Most typical applications are foams. In nature lignin acts also as a protecting agent and neutralises aggressive intermediates like free radicals [17]. These effects are interesting to protect polymers of PE-, PPor PVC-type. Blending of such polymers with lignin give hope for longer life cycles of the ensuing products [18]. In general, material development using lignin is a challenging area where well-defined and adapted lignin properties are required. From the branched complex chemical structure, applications in and for cross linking systems, i.e. resins and thermosets, seem to be the natural choice. However, thermoplastic applications have also been attempted with remarkable success. Thermoplastic lignin-containing products are produced by the German company Tecnaro GmbH [19] with an annual capacity of 3000 tonnes for their three production lines Arboform ® , Arboblend ® , and Arbofill ® (see page 22). Mixtures of lignin and natural fibres are thermoplastically processed in a similar way to conventional thermoplastics for their ‘liquid wood’ Arboform. Sectors of application are jewellery, toys, souvenirs, furniture, consumer articles, automotive interiors, and even Gucci shoes (Fig. 8). Presently, there is a strong market demand for carbon fibres, mainly driven by the aircraft and automotive industries. The usual precursor, apart from cellulose and mesophase pitch, is polyacrylonitrile (PAN) [20]. The possibilities of using lignin to produce a precursor fibre have been studied intensively by several groups. However, the carbon fibre’s mechanical properties achieved so far [21] are in the range of high performance cellulose fibres, such as rayon tire cord yarn. One prominent example for the conversion of lignin, lignosulphonates, or Kraft lignins into a pure chemical substance is vanillin (s. Figure 6) [22]. The production capacity is in an order of magnitude of 1500 tonnes/a. Degradation of lignin and further transformation steps to vanillin are achieved by chemical reactions. Biotechnological processes are also possible but there is no industrial scale production at the moment [23]. The efficiency of lignin as bio-based feedstock depends not only on its application as oligomer and polymer but also success in lignin degradation and the production of platform chemicals and building blocks with defined structures and high degree of purity complete the material concept. Just this combination has the high potential to stimulate lignin utilization today and in the future. Figure 5: Structure of vanillin CHO OH OCH 3 References [1] ACS Symposium Series 742 Lignin: Historical, Biological, and Materials Perspectives; edited by: W. G. Glasser, R. A. Northey, and T. P. Schultz, American Chemical Society, Washington, DC, 2000. [2] Freudenberg, K. und A.C. Neish (1968): „Constitution and Biosynthesis of Lignin.” Springer Verlag. Heidelberg-Berlin-New York [3] Toland J, Galasso L, Lees D, Rodden G, in Pulp Paper International, Vol. Paperloop, 2002, p. 5. [4] http://www.metso.com/pulpandpaper/recovery_boiler_prod. nsf/WebWID/WTB-090513-22575-6FE87 [5] http://www.innventia.com/templates/STFIPage____8733. aspx [6] http://gruberscript.net/Zellstoffscript/14Alternative_ Aufschlussverfahren.pdf [7] http://www.lignol.ca [8] http://www.biobased.nl/lignovalue [9] http://www.igb.fraunhofer.de/www/gf/cbp-leuna/start. en.html [10] K.H. Kleinemeier in O.Faix und D. Meier (Hrsg) 1st European Workshop on Lignocellulosics and Pulp, 1990, Verlag M. Wiedebusch, Hamburg 1991 [11] http://www.innventia.com/templates/STFIPage_8734.aspx [12] http://www.indiamart.com/alm-pvtltd [13] Elke Fliedner, Wolfgang Heep und Hendrikus W. G. van Herwijnen, „Verwendung nachwachsender Rohstoffe in Bindemitteln für Holzwerkstoffe”,. Chemie Ingenieur Technik 2010, 82, 1161-1168 [14] www.mwv.com [15] Lora, Jairo H., and W. G. Glasser. 2002. Recent Industrial Applications of Lignin - A Sustainable Alternative to Nonrenewable Materials. Journal of Polymers and the Environment 10 (1/2), 39-48. [16] C. Ciobanua, M. Ungureanua, L. Ignata, D. Ungureanub and V. I. Popa; “Properties of lignin–polyurethane films prepared by casting method”, Industrial Crops and Products 20 (2004) 231–241 [17] XUEJUN PAN,* JOHN F. KADLA, KATSUNOBU EHARA, NEIL GILKES, AND JACK N. SADDLER, ” Organosolv Ethanol Lignin from Hybrid Poplar as a Radical Scavenger: Relationship between Lignin Structure, Extraction Conditions, and Antioxidant Activity”, J. Agric. Food Chem. 2006, 54, 5806-5813 [18] Nitz et al., Kunststoffe 91 (2001), 98-101 [19] www.tecnaro.de [20] E. Bittmann, “Das schwarze Gold des Leichtbaus”, Kunststoffe 2006, 76-82 [21] J.F. Kadla et al., „Lignin-based carbon fibers for composites fiber applications“; Carbon40 (2002) 2913-2920) [22] Hocking, M. B., J. Chem. Educ., (1997) 74, 1055 [23] https://noppa.tkk.fi/noppa/kurssi/ke-40.9920/luennot/KE- 40_9920_vanillin_from_lignin.pdf www.iap.fraunhofer.de bioplastics MAGAZINE [01/11] Vol. 6 57

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