Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Shaping by extrusion
Patent
1996-12-02
1998-06-16
Tentoni, Leo B.
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Shaping by extrusion
264237, 425 71, 425 722, 425464, D01D 5088, D01D 5092
Patent
active
057665338
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a process to cool melt-extruded filaments made of thread-forming polymers, as well as a device to carry out the process.
Filament yarns and extruded fibers made of thread-forming polymers such as polyester, polyamide or polyolefine are conventionally produced in the melt-extrusion process. In this process, a molten mass of polymer is fed to a viscose pump which conveys the molten mass through the extrusion nozzles in the so-called extrusion block. The molten mass emerging from the nozzles in the form of liquid filaments congeal as they emerge in a cooling shaft. Subsequently simultaneous preparation, i.e. humidification of the equipment with an antistatic preparation and similar products also takes place before the filaments are conveyed to a further process. Cooling of the liquid filaments emerging from the extrusion nozzle has here a great influence on the titer uniformity (Ust value) and on the technological textile properties of the fiber and yarn in the end products. In some applications, e.g. with high individual titers, the yarn strength drops off as the production speed is increased (g/min/hole) (U.S. Pat. No. 4,973,236). The reason for this, among other things, is insufficient cooling of the molten stream coming out of the nozzle opening.
As a rule air, but sometimes also water is used as the cooling medium.
Air cooling has the advantage that the air exerts little friction on the emerging filaments so that undesirable drafting is avoided. However, the insufficient cooling action of the air is a disadvantage, so that a long cooling distance is necessary. However, a long cooling distance means slow cooling. Slow cooling favors the formation of crystallite in the yarn, and this causes problems in subsequent drafting. A high through-put capacity (g/min/opening) or thicker individual filaments require an especially long cooling distance, since the cooling speed is low. As mentioned above, this involves the danger of crystal formation in particular with this spun material.
Cooling is usually effected by blowing across the filaments. The air stream must be relatively free of turbulence here, and must move at a uniform speed over the funnel width so that every filament may be subjected to the same amount of cooling at the same time and location. Perforated metal sheets or sieve webs in combination with honeycombs are used in order to produce the required flow conditions. It is also possible to provide a speed profile over the height of the cooling funnel. In spite of these measures, which are expensive at this time, even cooling of all individual filaments is not ensured in case of a high number of filaments per surface. With lateral blowing, a temperature gradient is produced from filament to filament, so that the number opening rows provided for in the air stream is limited.
From U.S. Pat. No. 4,425,293 it is also known to use water as the cooling medium. The advantage of water cooling is rapid removal of the heat and therefor avoidance of extrusion crystallization. However a high degree of friction between water and filament is a disadvantage in water cooling. This may lead to undesirable drafting of the filaments. It has already been tried to calculate and design the undesirable drafting during water cooling so that a desired drafting takes place (U.S. Pat. No. 5,268,133 and WO 91/181 133). However such measures have been shown to be complicated and not without problems.
OBJECTS AND SUMMARY OF THE INVENTION
It is a principal object of the present invention to create a process which improves the cooling of the molten extrusion mass emerging from the nozzles and thereby to also make the spinning of stronger filaments at higher speed possible without crystal formation in these filaments which would have a disadvantageous influence on the subsequent drafting or drafting/extruding process. Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may b
REFERENCES:
patent: 4425293 (1984-01-01), Vassilators
patent: 4973236 (1990-11-01), Hasegawa et al.
patent: 5268133 (1993-12-01), Cuculo
International Search Report, Jun. 6, 1996.
Abstract of Japan 6-330,403 (Published Nov. 29, 1994).
Czase Erich
Kretzschmar Willi
Mears Ronald
Rieter-Automatik GmbH
Tentoni Leo B.
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