Indian Journalof Fibre & Textile Research Vol. 29, December 2004, pp. 483-492 Review Article Development and processing of lyocell R B Chavan Department of Textile Technology, Indian Institute of Technology, New Delhi 110 016, India and A K Patra' The Technological Institute of Textile & Sciences, Bhiwani 127 02 1, India Received 20 June 2003; revised received and accepted December 2003 5 An account of Iyocell, covering the hindsight of its development and available brands has been reported. This wonder fibre surpasses all other cellulosic fibres in terms of properties, aesthetics and. quite importantly. ecology in manufacturing. Among the various names with which Iyocell is available. Tencel and Tencel A 100 are the prominent and widely used. Be­ sides dealing with the various attributes of Iyocell, the options for wet treatment of the fibre with reference to steps of proc­ essing. suitability of dyes and process parameters have also been addressed. Keywords: Fibrillation, Lyocell, Peach-skin effect. Tencel. Tencei A 100 IPC Code: CI. DO 1 F 2/00. D2 1 H 13/08 I nl. 7 1 Introduction solved solids. The viscose rayon manufacturing proc­ ' There has been a growing demand for absorbent fi­ ess is also energy-intensive. Besides this, viscose bres with the need hinging on comfort and fashion. rayon production has high labour demand, mainly due Since cotton production can not go beyond a particu­ to the complexity and number of steps involved in lar level due to limited land availability, the other ob­ converting pulp into rayon fibre. vious options are viscose and the likes. But again, Among the modified viscose fibres, high wet with the increasing awareness of ecofriendly con­ modulus (HWM) rayon involves relatively simple and cepts, viscose is not quite highly rated because its economical manufacturing process, but the zinc used manufacturing plants have inherent problem of efflu­ in this process is a known pollutant. On the contrary, ent generation I . Carbon disulphide, which is used in polynosic fibre does not need zinc but requires for­ significant quantity in viscose manufacturing process, maldehyde for its manufacturing, which again is not is a source of major environmental problem. Sulphur ecofriendly. The quantities of some chemicals used in introduced in this process gets dispersed as sulphur making rayon, HWM and polynosic are shown in compounds (CS2, H2S, COS, S02) in the exhaust Table 1. Utilization of 2,3-hydroxyls in cellulose gases, process baths, solid wastes and product itself. monomer for complex formation with transition met­ About 15% of the CS2 used is converted into H2S in als was another dimension of development in viscose the form of viscose byproduct and sodium trithiocar­ and cuprammonium rayon manufacturing process. But bonate. Recovery of all the sulphur used in the proc­ the toxicity of metals like copper is not quite accept­ 2 ess is not possible and about 50% CS2 reclaim is able . achieved. Moreover, zinc sulphate, a viscose spin-bath com­ Table 1- Material requirements for manufacture of rayon fibres ponent, is often made at the rayon plant by dissolving metallic zinc in sulphuric acid. This chemical is toxic Chemical Regular HWM Polynosic to the aquatic life. Overall process effluents from vis­ NaOH, kg/kg 0.64 0.9 0.7 cose plant have high BOD, COD and total and dis- CS2• kg/kg 0.296 0.35 0.5 H2S04, kg/kg 0.95 1.37 1.1 "To whom all the correspondence should addressed. be ZnO, kg/kg 0.004 0.016 0.0001 Phone: +9 1-981 2094405; E-mail: [email protected] 484 INDIAN J. FmRE TEXT. RES., DECEMBER 2004 As regards various alternative methods proposed Newcell (the filament lyocell), is a Dutch multina­ for manufacturing viscose, ZnCh/water, NaOH/water, tional and has in fact purchased Courtaulds. The fibre O dimethyl acetamide/lithium chloride and carbamate division of both comes under Acordisl • Besides are prominent. In ZnCh/water, the problem is again these, there is a lyocell plant of Alceru Schwarza with the removal of residual zinc. Moreover, the spin­ GmbH at Rudolstadt, Germany. The company is a ning of fine deniers could not be established. Simi­ joint venture between the engineering company Lurgi larly, in NaOHlwater process, strength of the fibres Zimmer AG in Frankfurt and the Thuringion Institute produced was low. In DMAClLiCI process, the costs for Textile and Plastic Research (TITK) in Rudol­ involved in pre-activation of cellulose and recovery of stadtll. Alceru in fact produces the fibre with brand solvents proved to be the major bottlenecks. An alter­ name 'Seacell' using Iyocell technology in which native carbamate process has the problem of high en­ seaweed is incorporated. Among the Asian fibre ergy cost associated with low temperature require­ manufacturers, the acrylic fibre producer Hanil Syn­ ment for dissolution3. thetic Fibre Co. in Seoul, South Korea, sells Iyocell Thus, a good man-made water-absorbent fibre with fibres with the brand name 'CoceI'. In Taiwan, the convenient and ecofriendly manufacturing process viscose fibre producer, Formosa Chemicals & Fibre was long overdue. After years of research, lyocell fi­ Corporation (Taipei) started production of Iyocell sta­ bre was developed and it was claimed to be the first ple fibres but is no more in the business now. In India, new fibre in 30 years. It provides the comfort of natu­ the Birla Group, a major viscose fibre producer, had 4 ral fibre coupled with excellent aesthetics . Lyocell is initially shown some interest for developing Iyocell the generic name for a regenerated cellulosic fibre fibre, but didn't pursue it further. obtained by spinning of dissolved wood pulp in an 5 1.1.1 Tellcei organic solvent . The solvent spinning technique so Within the lyocell category, Acordis brought out 6. adopted is an environmentally responsible process the first commercial product ii1 1988 and brand named The fabric made out of this fibre gets very good value it as 'Tencel'. The fibre had an initial commercial addition when processed with requisite care. success in Japan, mainly in indigo denim and special­ ity niche products. Now, it is of course found in vol­ 1.1 Background 2 ume markets 1 . The fabric manufacturers have to reg­ The name lyoceU, given in 1989 for solvent-spun ister with Acordis while using its Iyocell fibre. The fibres owes its genesis to the Greek word Iyein 7, company gets into partnership with fabric manufac­ (meaning dissolve) from which comes Iyo and to cell turers using Tencel. The fabric maker buys lyocell from cellulose. This name was recognized as the ge­ fibre from the company and gets technical support neric name by BISFA (lnterm.. tional Bureau for the from Acordis for developing the requisite fabric 13.The Standardization of Rayon and Synthetic Fibres, Brus­ fabric after being made is sent to Acordis for testing sels) and the Federal Trade Commission (USA)8. This and if it passes the various physical tests, the fabric is fibre which took 16 years for its development with branded as Tencel. The fabric maker has to get sepa­ investment of US 500 million is now being pro­ $ rate approval for each of the different fabric qualities duced by different fibre manufacturers under different it makes, if he wishes to label them as Tencel. Same names. also holds good for processors and the Tence1 Quality PJOminent among the registered brand names of Number is given to each quality of woven or knitted Iyocell are Tencel (Acordis), Lenzing Lyocell (Lenz­ fabric. Clothings madt with Tencel fabrics carry trade ing) and Newcell (Akzo Nobel). Newcell is a filament mark swing tags and sewn-in-Iabels issued by Cour­ 9 while the other two are staple fibres . The two Tencel taulds (Acordis) as proof of authenticity and qualityl4. manufacturing units of Acordis (previously Cour­ Otherwise, the fabric is called Iyocell only. Perhaps taulds) - one in Mobile, Alabama (USA) and another that is why it is said that lyocell fibre from Acordis is relatively new one in Grimsby (UK)--have a produc­ termed 'Tencel' when used for apparel applications tion capacity of 40,000 tons/year each: Lenzing AG and called 'Iyocell' when used for technical or indus­ has its lyocell fibre produced by Lenzing Lyocell trial applications. The trade mark of Tencel is in the GmbH in Heiligenkreuz, Austria. It started the manu­ form of triple "X". This is also applicable for blended facturing process after taking a license for the basic fabrics, but the blend should have at least 40% patents from Akzo. Akzo Nobel, manufacturer of Tencel15• CHA V AN & PATRA: DEVELOPMENT AND PROCESSING OF LYOCELL 485 1.4 WOOD PULP OXIDE Tencel is available in two fibre counts of and AMINE 1.7 dtex as standard qualities. The staple fibre of 1.1, 2.4 and 3.3 dtex are also available for special applica­ tions. Most of the Tencel fibres are bright, but a matt fibre type is also available. i 2 Fibre Manufacturing The starting material for lyocell and viscose are the same, i.e. wood pulp, but the manufacturing processes 6 . are dl· f:Cerent3.4.7,S, 1 , 17 . N ce11 u 1ose d"envatlve i l' 0 IS EVAPORATE formed in the former, while viscose rayon manufac­ turing involves formation of intermediate derivative. Lyocell is manufactured by a direct dissolving process using an organic cyclic polar solvent, namely N­ PURITYi methyl morpholine-N- oxide (NMMO). This solvent is non-toxic and is easily regenerated. NMMO has higher cellulose dissolving capacity than the other organic polar solvents, like DMSO, DMF, DMAC, NOMA, HMPA, etc. The NMMO solution used is a CRIMP 1-1 TENCEL FIBRE 50:50 (w/w) mixture of solvent and water.