(57) A process is described for the production of high strength polyester yarn wherein
the conventional spin draw process has been modified. Yarn having a tenacity of at
least 7.5 g/d and an elongation of at least 9% may be spun using this process at a
speed of at least 1900 meters per minute. The yarn may be used in tire cord and other
industrial applications.
Figures 1 and 2 illustrate in schematic form the general process steps of spinning
and drawing respectively. Polyester in the form of melt extrudable polyethylene terephthalate
(PET) is charged to a hopper 12 which empties into a screw extruder 14 which thereupon
mixes and heats the polyester to a temperature of about 287°C.
The now molten polyester is pressure fed by the extruder to a spinnarette 16 having
a plurality of capillaries 17 through which the polyester is extruded. The number
of capillaries can vary from about 50 to over 100. The extruded filaments are maintained
at a temperature near the melting point of PET by a quench delay collar 20 often referred
to simply as a quench collar. The filaments are then quenched by an inert gas or air
stream 22 of ambient temperature before passing though a chute 24. The filaments 18
are now in a solid state.
At the end of the chute 24 is a tray and kiss roll 26 which applies a conventional
spin finish compound to the filaments. The filaments are then converged at point 28
into yarn 30, which is thereafter transported by a pretension godet 32, godets 34
and guide rolls 36 to winder 38, where the yarn is wound and may be either stored
for future drawing or may be used as feed immediately to the drawing process in continuous
fashion.
The drawing process is illustrated in Figure 2. Yarn 30 from winder 38 passes between
pretention rolls 42 and over guide roll 44 to top godet 46. The yarn then travels
around draw pin 50 which localizes the draw at a point just below top godet 46. The
amount of draw is governed by the relative rotational speeds of top godet 46 and a
bottom godet 56, the latter rotating at a high speed than top godet 46.
After passing over draw pin 50, the yarn 30 passes over a platen 52 before being wound
on the bottom godet 56. Rolls 48 and 58 separate the wraps and keep them from rubbing
against each other. Platen 52 is heated to a temperature of about 215°C. to about
230°C. From the bottom godet, the now drawn yarn passes through guide loops 60 and
is wound onto a spool 62. The yarn is now ready for use at this point.
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