Cotton waste recycling: Quantitative and qualitative assessment

Available online at www.sciencedirect.com Resources, Conservation and Recycling 52 (2008) 785 791 Cotton waste recycling: Quantitative and qualitative assessment Mohamed Taher Halimi, Mohamed Ben Hassen, Faouzi Sakli Textile Research Unit of ISET Ksar-Hellal, B.P 68 Ksar Hellal 5070, Tunisia Received 31 May 2007; received in revised form 7 November 2007; accepted 18 November 2007 Available online 30 January 2008 Abstract The waste produced in a cotton textile mill is an important factor in determining the operating cost and therefore in influencing mill profits. In this paper, we examine the waste percentage and the good fibre fraction for two cleaning machines and a card. The cleaning behaviour in spinning preparation, of each waste, is predicted by determining the trash content and the preparatory processing. The quality of recovered fibres is discussed and compared to other virgin cotton. In order to appreciate these fibres, we study the effect of cotton wastes on the rotor yarn quality. The results indicate that generated wastes contain about 50% good fibre. This secondary raw material showed good cleanability and characteristics; therefore it can be blended in a proportion between 15 and 25% without hardly noticeable changes in rotor yarn quality. 2007 Elsevier B.V. All rights reserved. Keywords: Cotton wastes; Recovered fibre; Cleaning behaviour; Quality 1. Introduction Environment protection and waste recycling have become two of the most important challenges facing the scientific and industrial community. In the textile industry, the different textile processes create various waste materials in different stages such as fibre, sliver, yarn and woven. Textile production and consumption are continually increasing. Generally, waste recycling requires accounting technical and economic considerations. Environment studies have to address these two interests and suggest solutions to persuade manufacturers to treat waste. In spite of the considerable technical improvements achieved in blowroom machines, the generated waste in cotton spinning contains a high portion of fibres (Paul, 1994; Leifeld, 1996). Raw material prices, energy and labour costs have been continuously rising for many years. Therefore, manufacturers attempt to improve the exploitation of the raw material by recovering fibres from waste and providing high cleaning efficiency in blowrooms and cards. The recovered fibres from cotton waste can be used to produce blended yarns (cotton waste/virgin fibres) in different portions. Corresponding author. Tel.: +216 97 367 690; fax: +216 73 475 163. Co-corresponding author. Tel.: +216 73 475 900; fax: +216 22 930 424. Corresponding author. Tel.: +216 73 475 900; fax: +216 73 502 288. E-mail addresses: taheeer@yahoo.fr (M.T. Halimi), benrayen@yahoo.fr (M.B. Hassen), technopole.monastir@serst.rnrt.tn.fr (F. Sakli). Moreover, they are used in the carded non-woven industry. In spinning, when dealing with the blend (cotton waste/virgin fibres), we are faced with a problem which has many facets and which can only be optimized by taking account of several parameters at the same time. The evaluation of recovered fibre characteristics allows the spinner to optimize the recovered fraction of good fibre. In addition to fibre properties, the cleaning behaviour in spinning preparation is very important for achieving the following benefits: evaluation of optimum blend (cotton waste/virgin fibre), optimization of machine setting in view of fibre/machine interaction and the elimination of quality problems before they appear in the final product (Stefan and Kuschel, 1995). There are many published papers that have discussed the cleaning behaviour of virgin cotton and its characteristics. Nevertheless, there are only a few published papers about recovered fibres quality and there are no published studies about cleaning behaviour of cotton waste. These kinds of studies are crucial to encourage manufacturers to treat cotton waste. Peter Artz and Dipl-Ing (1995) considered the cleanability as the easiness or the difficulty for cotton to get rid of its impurities. Simultaneous research from the machinery industry quantified five variables which could perfectly affect the cleaning behaviour. These are: the initial trash and dust content, cotton characteristics, the type of machinery, production rate and cotton moisture content (Leifeld, 1993; Steadman, 1997). On the other hand, the preparatory processing is defined as the necessary 0921-3449/$ see front matter 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.resconrec.2007.11.009

786 M.T. Halimi et al. / Resources, Conservation and Recycling 52 (2008) 785 791 spinning preparation to lead the cotton for given trash levels. It mainly depends on the trash content and the cotton cleanability (Peter Artz and Dipl-Ing, 1995). In addition, the use of second raw material is related to the spinning process, the quality of fibre and the yarn to be produced (Paul, 1994; Leifeld, 1996). Many published papers have discussed the reuse of recovered fibres in spinning. Bruggeman (1982) confirmed that these fibres can be reused for the open end spinning. The requirements of quality imposed on the finished products allow only the addition of tiny quantities of recovered fibres. Therefore the proportion of secondary raw material blended with primary material must be carefully studied. In a study consecrated to the rotor spinning process, Wulfhorst (1984) concluded that up to 20% of recovered fibres can be blended with primary raw material without noticeable changes in quality. All those studies have provided some insight into the reuse of cotton waste in a spinning mill, but there remains a need for more quantitative analysis to identify the potential of changes in yarn s properties. In order to encourage spinners to treat cotton wastes, we study in this paper its cleaning behaviour and we try to appreciate the recovered fibre quality. On the other hand, we evaluate the ratio effect of recovered fibre on the quality parameters of the open end yarn, such as: tenacity, regularity and elongation. 2. Materials and methods 2.1. Waste characteristics In this study, we are interested in cotton waste of different origins, and collected from four Trützschler sections. The waste collected from four different machines is considered in this analysis: two Trützschler cleaners (AXI-FLO and CVT4), Rieter card flats, and under cards. Under card wastes include motes and fly removed material. The control device Micro Dust Trash Analyser, MDTA3 is used to determine fibres and trash content in each waste sample. Several methods are used to determine the cleanability C (%) (Schlichter and Kuschel, 1995). The simplest of them consists of determining the relationship between the percentage of trash, eliminated after one passage T 1 of the sample in the control device Micro Dust Trash Analyser MDTA3, and the total T total of this same sample (Peter Artz and Dipl-Ing, 1995). C-Factor depends on successive passages of the control device Uster- MDTA 3, more the quantity of trash T 1 collected in the first passage is raised more the cleanability of the waste is better. Thus, the cleanability (C%) can be determined according to C(%) = T 1 100 (1) T total In order to appreciate waste cleaning behaviour, we have to determine the preparatory processing and the trash content. In this work, we considered the preparatory processing as the number of passages necessary to lead the sample of waste to trash content under 5%. This is because trash typically accounts for 1 5% of baled cotton. A trash tester Shirley Analyser (consid- Fig. 1. The spinning process.

M.T. Halimi et al. / Resources, Conservation and Recycling 52 (2008) 785 791 787 Table 1 Spinning parameters and setting Spinning parameters Value/setting Rotor speed (tr/min) 52,500 Twist factor (α) 160 Yarn count (tex) 100 Rotor type T40 Opening roller speed (tr/min) 8800 Table 2 Waste and fibre content for an AXI-FLO cleaner Line Waste (%) Fibre content in waste sample (%) 1 2.50 0.21 41.83 1.29 2 2.00 0.20 43.22 2.37 3 1.80 0.26 40.48 2.67 4 2.21 0.31 41.98 2.76 5 1.61 0.30 42.56 1.87 6 1.80 0.21 45.40 2.43 1.99 42.58 0.32 1.65 ered as a single roll cleaner) was used as a reference machine. After that, the number of passage is determined in order to compare wastes cleaning behaviours. Once the waste fibre properties are analysed, important information can be gained as far as the machine setting and quality of the end product. The recovered fibres from different cotton wastes were tested on both Uster HVI (Hight Volume Instrument) and AFIS testers (Advanced Fiber Information System). 2.2. Spinning parameters In order to study the effect of cotton waste on the rotor yarn quality, yarns with a count of 100 tex are produced with different waste portion. In total, the waste percentage (Wp) in yarn takes eight levels varying from 0 to 100%. After this, the mechanical properties of yarns were tested by the USTER TENSORAPID and analysed. Fig. 2. Trützschler cleaners (AXI-FLO). (1) Feeding mechanism, (2) roller cleaner, and (3) waste separator. Table 3 Waste and fibre content for CVT4 cleaner Line Waste (%) Fibre content in waste sample (%) 1 0.52 0.12 49.5 1.58 2 0.50 0.11 50.79 1.47 3 0.34 0.07 45.39 2.40 4 0.39 0.09 41.98 3.44 5 0.45 0.06 42.56 2.29 6 0.39 0.05 44.20 2.3 0.43 45.74 0.07 3.64 The processing steps and machinery used are shown in Fig. 1. The blend was processed after carding at the first passage in the drawing frame. Another passage was used in order to improve the homogeneity of the blend. The linear density of the second drawing sliver was 4.45 ktex. Slivers were used to produce yarns on a Schlafhorst Autocorro rotor spinning machine. Ten spindles were used for each blend, these being selected at random within the machine. Spinning parameters are given in Table 1. Fig. 3. Trützschler cleanomat (CVT4). (1) Feeding roller, (2) cotton, (3) roll clothed with pins, (4) roll with finer clothing, and (5) knife of separation.

788 M.T. Halimi et al. / Resources, Conservation and Recycling 52 (2008) 785 791 Fig. 4. Location of card waste. 3. Results and discussion 3.1. Waste rate 3.1.1. AXI-FLO waste The main functions of the opening and cleaning machines are the further separation of the fibre flocks and the removal of contamination particles and dust from the cotton. The AXI-FLO cleaner is designed to eliminate large trash particles at the first stage of the blowroom (Fig. 2). Table 2 shows the waste and fibre contents of the AXI-FLO cleaner. Six cleaning lines were used in the analysis and each data point shown in Table 2 is the mean of 10 waste samples. For this machine, waste represents 2% of treated material, while the fibre rate is about 42%. The waste produced in the blowroom and carding sections of a Tunisian cotton textile mill was about 850,000 kg in 2005. In this mill, waste mixture was passed into a filter in order to reduce impurity which will be then compacted into bales. Typically, recoverable fibre from AXI-FLO cleaner was about 130,800 kg. 3.1.2. CVT4 waste The Cleanomat CVT4 has four rollers cleaner consequently it has a high cleaning efficiency and it s designed to eliminate small trash particles (Fig. 3). Results illustrated in Table 3 indicate that CVT4 wastes are about 0.43% of treated material. From these wastes, we can recuperate 45% of good fibres. Typically, recoverable fibres from AXI-FLO cleaner were about 32,700 Kg. These results confirm that generated wastes contain considerable rate of fibres (Table 3). 3.1.3. Cards waste The main card tasks are the removal of dirt particles and short fibres, fibre alignment and sliver formation. The major part of the carding action is accomplished between the tambour and the flats whose teeth are positioned toward each other for carding action (Fig. 4). This causes separation into single fibres and the parallelization of the fibres. At the same time, contaminants and short fibres are removed. In this work, under card waste include motes and fly removed material. Six carding lines are concerned. Results illustrated in Table 4 indicate that the sum of card wastes are about 4% of treated material. In flat and under card wastes, we can recover respectively 65 and 56% of fibre. Typically, recoverable fibres from AXI-FLO cleaner were about 261,600 Kg. In spite of the technical improvements in cards, these results confirm that wastes generated contain a large fraction of good fibres. Table 4 Waste and fibre content for card Card Flats a Under card a Flats b Under card b C1 2.6 0.12 2.2 0.13 65.95 2.9 45.39 1.31 C2 2.4 0.30 2.3 0.19 64.43 2.52 50.26 1.37 C3 2.2 0.18 2 0.25 67.25 1.25 69.39 1.01 C4 2.8 0.13 1.8 0.15 60.02 2.85 57.87 1.85 C5 3.2 0.37 1.9 0.21 59.67 1.28 48.99 1.94 C6 3 0.22 1.7 0.11 73.5 2.28 64.49 2.23 2.70 1.98 65.14 56.07 0.37 0.23 5.13 9.48 a Waste (%). b Fibre content in waste sample (%).

M.T. Halimi et al. / Resources, Conservation and Recycling 52 (2008) 785 791 789 Fig. 8. length (mm) of wastes and initial cotton. Fig. 5. Relationship between T% and passage number for under card and flat wastes. Values presented as mean ± S.D. based on eight experimental measurements. ties and the trash content are the main factors that reduce card wastes cleanability and change the processing stages of spinning preparation. Thus, these wastes need a more intense opening and cleaning than other wastes. 3.3. Comparison of wastes cleanability Fig. 6. Comparison between the cleaning factors (C%) of machine waste and commercial cottons. 3.2. Preparatory processing comparison In this study, we are interested in determining the number of passages necessary to produce a waste sample with under 5% trash content. Each point in Fig. 5 represents the mean of eight waste samples. In addition, AXI-FLO and CVT4 wastes need only one passage on the mono-cylinder cleaner to have a trash content of 4.3%. While card wastes need two passages, as shown in Fig. 5. These results can be explained by the fact that card wastes contain more small particles (seed-coat fragments) which hang up fibres. Consequently, it is too hard to eliminate by only one passage. However, the cleaner wastes (AXI-FLO and CVT4) contain larger particles which separate easily during the first passage. From these results it seems that fibre proper- The different waste cleanability are compared to some commercial cotton one, by using the cleanability factor C (%). Fig. 6 indicates that card wastes, after two passages on the Shirley Analyser, the best cleanability factor (60%), was closer to the Greek and Syrian cottons. Card wastes seem to contain less seedcoat fragment than CVT4 and AXI-FLO wastes. This results can be explained by the doubled passage of card waste in the trash tester (Shirley Analyser). The practical interest of cleanability factor determination is to avoid blending waste and virgin cotton with different cleaning behaviour. 3.4. Recovered fibres quality The neps count, mean length, short fibre content, and fibre maturity are the most important parameters that indicate cotton quality. The measure of these properties is very important to determine: the recovered fibres usefulness and their proportion in the end product. Obviously, primary raw material has better properties than recovered fibres as given in Figs. 7 10. In fact, the comparison of properties indicates that AXI-FLO and CVT4 wastes are very close to the initial cotton properties especially for mean length, short fibre content and maturity. These data are in agreement Fig. 7. Neps count (g) of wastes and initial cotton. Fig. 9. Short fibre count (%) of wastes and initial cotton.

790 M.T. Halimi et al. / Resources, Conservation and Recycling 52 (2008) 785 791 Fig. 10. Maturity of wastes and initial cotton. with published literature (Bruggeman, 1982; Wulfhorst, 1984; Klein, 1993), which suggests that these fibres can be reused for the open-end spinning. Fig. 12. Effect of waste portion on rotor yarn irregularity. 3.5. Comparison of yarn quality Tenacity, elongation and irregularity are the most important parameters which indicate the yarn quality. Fig. 11 shows that the tenacity decreased by 26.3% when the waste content of the yarn was increased to 100%. Obviously, the high short fibres count and the low maturity of recovered fibres degrade mechanical properties. On the other hand, the tenacity decreased by 11.6% when the waste content was increased to 25%. The yarn irregularity can be estimated by the coefficient of variation (CV%) of the yarn count. The effect of waste content on the yarn irregularity is shown in Fig. 12. The yarn irregularity was not affected by the waste content of the cotton when it was below 25%. However, when the waste content of the cotton was above 25%, the effect on the yarn irregularity was considerable (Fig. 12). In agreement with published literature (Klein, 1993; Jackowski et al., 2002), the yarn elongation is mainly related on raw material properties. As shown in Fig. 13, increasing the waste content of the cotton to 25% decreased the yarn elongation by 1.6%. It can be concluded that the introduction of 15 and 25% waste fibre into the cotton will not affect the tenacity, the irregularity and the rotor yarn elongation. 4. Conclusions Fig. 13. Effect of waste portion on rotor yarn elongation. This study mainly emphasizes the critical importance of evaluating the fibre wastes and its characteristics through the preparatory stage. In spite of the technical evolution of different blowroom machines, the generated wastes contain a large fraction of good quality fibre. Results indicate that recovered fibres have a good cleanability which allows its blend with virgin fibres. AXI-FLO and CVT4 wastes contain fibres with neps, maturity, short count and mean length close to those of initial cotton. In addition, the study of waste influence on the quality of the open end yarn indicates that the introduction of 25% of waste does not alter the tenacity, the irregularity and the yarn elongation. Acknowledgements The authors acknowledge the International company of textile SITEX Tunisia, the technical advice and support received from Mr. Romdan Bouchraeit at the same company. References Fig. 11. Effect of waste portion on rotor yarn tenacity. Bruggeman J-P. Traitements mécaniques des déchets et des cotons charges. L industrie textile No. 1128; 1982. p. 1049 51.

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