Melt Spinning Line

Poly(lactic acid) Synthesis, Structures, Properties, Processing, and Applications, edited by R. Auras, L.-T. Lim, S. E. M. Selke, and H. Tsuji Copyright 2010 John Wiley Sons, Inc. 

PLA resin can be successfully dried using most standard drying systems [4]. The details of drying PLA resins are described in Chapter 14. 

Once the polymer is filtered, it reaches the distributor. The function of the distributor, as the name suggests, is to ensure 

FIGURE 20.1 Schematic representation of melt spinning setup (1) extruder drive, (2) extruder, (3) hopper, (4) screw, (5) manifold, (6) static mixer, (7) metering pump, (8) metering pump drive, (9) spin pack, (10) mesh filters, (11) distributor, (12) spinneret, (13) cross-flow quench chamber, (14) freshly spun yam, (15) godet, (16) idler roller, (17) friction-driven winder, (18) yarn bobbin. 

(1) Temperatures are only starting points and may need to be altered. Target PLA melt temperatures (after melt pump) should be in the range of 235 5°C. (2) PLA resins should not be processed at temperatures above 250°C due to excessive thermal degradation. 

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Cakmak M, Teitge A, Zachman FI G and White J L 1993 On-line small-angle and wide-angle x-ray scattering studies on melt-spinning poly(vinylidene fluoride) tape using synchrotron radiation J. Polym. Sc/. 31 371- 81... 

Melt or solution spinning of synthetic fibers is a marvel of modern technology. Fiber lubrication, which is of the utmost importance in this high-speed process, is achieved by the application of spin finish—a combination of oils and surfactants. A typical spin line for the production of polyester staple fiber is shown schematically in Figure 2. The number of filaments, which can vary from tens to thousands, come into contact with various parts of the machinery, some of which are heated for proper fiber modification. To replenish the lost finish and to ensure adequate lubrication,... 

Photosensitivity is enhanced by melt oxidation because of dissolved 02 and high melt temperatures, but spin-line oxidation is insignificant. 

Kim, K.H., Cho, H.H., Ito, H., Kikutani, T., 2008. Fiber structure development in high-speed melt spinning of poly(trimethylene terephthalate) (PIT)—on-line measurement of birefringence. J. Polym. Sci. B Polym. Phys. 46, 847 56. 

The metering pumps are precision-made positive-displacement gear pumps, especially designed for melt spinning. They are used to ensure that a precise proportion of the melt from the extruder is delivered to each thread line and that the thread line denier does not vary with time. Modern pressure-feedback-controlled extenders operate remarkably steadily, but not steady enough for multifilament spinning without meter pumps. 

Ziabicki [187] has given an extensive review of studies of the melt-spinning process. Some derivations from this review are discussed briefly. A simple analysis for predicting the effects of process parameters on fiber orientation are also discussed before polypropylene data are presented. To summarize, the properties of spun polypropylene fiber (and other fibers as well) are primarily determined by the stress existing in the spin line at the position of the final diameter, at least at moderate spinning speeds. The stress level is determined largely by ... 

Nadella et al. [79] studied polypropylenes with a broad range of melt flows. Table 3.25 lists the properties of the melts they studied. These melts were spun from a screw extruder at a temperature of 230°C. In the case of H-0060, filaments were also spun at 200 and 260°C. With the exception of H-0042, the polymers were spun through a single capillary at 2.1 g/min. The H-0042 could not be extruded at that rate because of melt fracture this material was extruded at 0.5 g/min. The filaments were quenched in stagnant air at 25°C and were taken up at speeds of 50,100,200,400, and 550 m/min. X-ray and birefringence measurements were taken along the descending spin-line. 

Jaffe studied spun fibers produced at different spin-line stress levels. Figure 3.52 shows DTA traces of fibers spun from Profax 6523 at both a low level and a high level of spin-line stress. Both fibers had been annealed at 140°C prior to melting. The small endotherms at 140°C... 

FIGURE 3.53 Melting peak temperature versus heating rate for three polypropylene fibers spun at different spin-line stress levels. (From Jaffe, M. In Thermal Methods in Polymer Analysis, Shalaby, S.W. ed., Franklin Institute Press, Philadelphia, 1977, p. 93. With permission.)... 

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