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4 Rieter . LINK 52 . 1 /2008 TECHNOLOGY Processing SPV viscose using Rieter R 40 rotor spinning technology The combination of SPV viscose fibers with Rieter R 40 rotor spinning technology enables rotor speeds of 130 000 rpm and delivery speeds of 175 m/min to be achieved with Ne 30/1 yarns while maintaining very good running properties and optimum yarn structure for downstream processing of the yarn. The twist factor for processing SPV viscose is ideally within the αm 100-110 range. A mean twist factor of αm 105 can be recommended for weaving and knitting applications. Fig. 1 Moisture distribution in the cross-section of the different cellulose fibers. Source: Autex Textile Conference 2005. 1. Cotton 2. TENCEL® 3. Modal 4. Viscose Alternative to cotton Cellulose fibers such as viscose, Modal and Tencel® are very good alternatives to cotton and play a major role on the textile market, especially for fashionable clothing, bed linen, towels and underwear. Raw materials made from cellulose are even better than cotton in certain clothing functions, for example softness and antibacterial properties. Cellulose is therefore either blended with cotton or used 100% in clothing that comes into direct contact with the skin. In the case of extremely high functional requirements, multi-component textile fabrics can also 1 2 3 4 be called for. The use of two-ply weaves in different raw materials is a trend-setting feature here. A combination of different knitted or woven fabrics can be of advantage in leisurewear and sportswear, where dealing with body perspiration is an important aspect. The skin can be prevented from cooling off if body moisture is absorbed by the viscose/cotton blend and transported into the atmosphere through the polyester surface. The polyester surface also protects the skin against external environmental influences. Properties of cellulose fibers Cellulose fibers have the best antibacterial properties compared with polyamide, polyester, polypropylene and cotton. They also absorb moisture very readily and distribute it very effectively, depending on type. For example, Tencel® absorbs as much as 50% more moisture than cotton. Moisture distribution is illustrated by the adjoining photographs, in which the dark areas indicate moisture and the light areas the fiber raw material. In the case of Tencel® it is apparent that moisture distribution occurs over a very wide area and that moisture is absorbed very uniformly compared with cotton (Fig. 1). High-performance spinning In addition to the major advantages of cellulose fibers in the garment industry, the type of viscose and the spinning process, such as ring, rotor or air-jet, and the optimum machine configuration play a crucial role. Ultimately, these parameters are decisive not only for the properties of the textile product, but also the economics of yarn manufacture. Test parameters A 1.3 dtex SPV viscose with 38 mm cut staple was used, together with another Asian viscose with the same specifications for comparison. These were processed on the latest Rieter high-performance machines: • C 60 card • SB-D 15 drawframe • RSB-D 40 drawframe • R 40 rotor spinning machine.
Fig. 2 Fiber cross-section structure of the SPV fiber and the Asian fiber. 1. SPV viscose 2. Asian viscose Processing viscose on rotor spinning machines is especially attractive. Ring-spun yarns made from viscose generally produce a very soft and pliable fabric hand. By contrast, rotor-spun yarns produce a rather harder hand due to their belly-band structure. The combination of viscose and the rotor-spun yarn structure ultimately results in an ideal fabric hand with very good pilling properties in the textile fabric and is very economical by virtue of the high delivery speed due to rotor spinning technology. Intermediate product results Both types of viscose used display distinct differences in fiber length, despite having the same staple length specification of 38 mm. The figure for SPV viscose is significantly higher in this respect, which is reflected in a mean staple length approx. 3 mm longer up to the card intake. Long fibers increase after the card due to fiber parallelization and de-crimping. On the other hand, mean fiber length decreases slightly after the card due to a higher short fiber content. The short fiber content increases as a function of fiber loading and fiber strength on the card. Use of SPV fiber results in a minimal increase in short fibers of only 1.5% in absolute terms, whereas the short fiber content increases by 4.5% in absolute terms with the Asian viscose. The higher overall short fiber content and its significantly greater increase after carding will have a negative impact on yarn tenacity and elongation. It can be concluded from the higher fiber strength and elongation in the case of SPV viscose that this is at least one reason for the minimal increase in short fibers of only 1.5% after the C 60 card. A fiber of lower strength and elongation, such as the Asian viscose, is also more sensitive to fiber shortening in light of the fiber loading occurring in the spinning process. It can be concluded from this that the carding output of 80 kg/h can certainly be increased further in the case of SPV fiber. The fiber cross-section structure of the two types of viscose differs significantly, which can also result in differing processing properties and yarn qualities (Fig. 2). 1 2 Rieter . LINK 52 . 1 /2008 TECHNOLOGY Closer examination of the raw material has already shown that distinct differences exist between the types, despite the same raw material specification, such as fiber count and fiber length. Differences in processing properties must therefore also be expected on the final spinning machine, as well as in yarn quality and the final quality of the textile fabric. Yarn results Yarn properties are determined essentially by yarn structure and thus the final spinning process as well as raw material and fiber preparation. As has already been pointed out, the combination of viscose raw material and the rotor spinning process offers considerable potential in terms of yarn properties and economics. The question now arises of the extent to which settings on the rotor spinning machine and the choice of technology elements influence yarn quality and productivity. 5
Page 1 and 2: The customer magazine of Rieter Spu
Page 3: It has become clearly apparent in r
Page 7 and 8: Fig. 4 Maximum work load vs. rotor
Page 9 and 10: The new SB-D 11 compact drawframe T
Page 11 and 12: Large product diversity with ComfoR
Page 13 and 14: Fig. 3 AEROpiecing® technology on
Page 15 and 16: Fig. 3 Spinning rings of up to 54 m
Page 17 and 18: Enhanced user-friendliness with ori
Page 19 and 20: Rieter’s 80 years in China Rieter
Page 21 and 22: Fig. 3 In addition to building fact
Page 23 and 24: Fig. 2 The C 60 card was on show

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