Melt spinning

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Melt spinning ( English melt spinning ) is a spinning method for such synthetic fibers whose raw materials are made to spin by melting of air. Common synthetic polymers for this are those with hetero chains ( polyester (especially PET = polyethylene terephthalate ), polyamide ) and some with carbon chains such as. B. polypropylene . In melt spinning systems, either the granulate (and in rare cases also powder), prepared ready for spinning, is melted in extruders or the melt is fed directly from the finisher to a continuous polycondensation system. The thread-forming elements then generally consist of mixing and homogenizing elements, filters, metering pumps and spinnerets, which are connected by lines for the correspondingly high pressure. The polymer melts are pressed through spinnerets at temperatures from 30 to 60 ° C above the melting point (depending on the polymer) and the resulting melt jets are then solidified using various post-treatment methods. When using a spinneret with only one nozzle bore, usually of a larger diameter, a so-called monofilament is created , while spinnerets with several nozzle holes create a multi- filament . It is also possible to spun several polymers in one filament in a defined geometry simultaneously, for which the bicomponent melt spinning process is used.

A stable melt spinning process requires a corresponding flow behavior of the melted polymer . The polymers used are generally linear and may only be present in a certain molecular weight range. As the fibers are wound up after exiting the nozzle, the polymer chains are partially oriented in the direction of the fibers. When the polymer solidifies during cooling, amorphous and crystalline areas are formed in the fiber . The ratio of amorphous and crystalline areas and the crystal structures formed depend heavily on the polymer and the take-off speed. With increasing take-off speed (typically in the range from 1000 to 6000 m / min), the orientation of the polymer chains improves. A distinction is made between high oriented yarn (HOY), low oriented yarn (LOY) and partially oriented yarn (POY).

On the other hand, melt spinning is also understood as a process for the rapid cooling of melts , in which the melt is blown onto a rotating wheel. This is an incorrect translation from English, which describes this process as " melt spinning ". " Spin " in this case does not mean " spider " in terms of " fibers twisted together " but " quick turn " or " fling ". A better term for the process is therefore melt spinning : The melt that has solidified on the rotating wheel is usually thrown away immediately by the rapid rotation.

Individual evidence

  1. ↑ Hans-J. Koslowski: Chemical fiber lexicon. 12th, expanded edition. Deutscher Fachverlag, Frankfurt am Main 2009, ISBN 978-3-87150-876-9 , p. 199.
  2. ↑ Zakhar Aleksandrovič Rogowin: Man-made fibers: chemistry - technology. Georg Thieme Verlag, Stuttgart / New York 1982, ISBN 3-13-609501-4 , p. 19.
  3. ↑ Franz Fourné: Synthetic fibers: production, machinery, Features: Manual for system planning, machine design and operation. Carl Hanser Verlag, Munich / Vienna 1995, ISBN 3-446-16058-2 , p. 273.

literature

  • Hubert Graefen (Ed.): Lexicon of materials technology. Springer Verlag, Berlin / Heidelberg 1993, ISBN 3-642-51733-1 .
  • Wolfgang Kaiser: plastics chemistry for engineers. 3. Edition. Carl Hanser Verlag, Munich 2011, ISBN 978-3-446-43047-1 .

See also

Web links