Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1996-09-20
1998-10-06
Ryan, Patrick
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428364, 264103, 57 3, 57243, 57282, 57310, 57902, B32B 2734
Patent
active
058174176
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a method for the continuous production of a multifilament stretchable weft yarn from polyester-POY-filaments for tire cord fabrics, as well as a weft yarn produced in accordance with the method.
A polyester-POY (partially oriented yarn) is understood to mean a yarn produced by the melt spinning of polyester at 2,800 to approximately 4,200 m/min.
Methods for the production of weft yarns for tire cord fabrics which have a rough non-slip surface and meet the high thermal and mechanical load requirements encountered in the manufacture of, are known. Apart from the methods for producing coated weft yarns, methods are also known for producing uncoated polyester weft yarns. In the known methods, the non-slip strength is either achieved by wrapping with natural fibres or by the twisting of a yarn of polyester-POY and subsequent heat treatment (EP-A-0 223 301). On air nozzle machines, a wrapped yarn leads to an unacceptable fibre flight. A twisted stretchable weft yarn is produced in at least two production steps that are technically labor intensive; an additional swirling would add a further step to the labor-intensive method. In the state of the art, the possibility of swirling effected in the winding up zone is admittedly mentioned, but a method of technical action is not indicated. The combination of swirling/twisting serves no purpose per se, since a worse method for obtaining a yarn finish is combined with a better method and hence the first step of the method becomes superfluous. A reversal of this step, that is to say, twisting/swirling is not expedient, since a twisted, and hence largely closed, yarn bundle can only be insufficiently swirled.
If the swirling is effected on its own, it is usually effected before the spooling, that is to say, after all other steps of the method have been completed. In the present case, that of swirling shrunk POY, this process leads to a non-homogeneous yarn with many projecting filament bends which impede proper unspooling.
SUMMARY OF THE INVENTION
It is the object of the invention to provide a technologically simple and economic method for producing a highly stretchable polyester weft yarn for tire cord fabrics.
A further object is to provide a weft yarn with a high elongation which also remains preserved after an extreme thermal loading. At the same time, the yarn is to show very low thermal shrinkage and as large a running length as possible per unit weight.
These objects are attained by a method for making a weft yarn according to the invention, in which the polyester-POY-filament with an initial titre of dtex 170-260 is swirled by means of a pressurized gas and is shrunk immediately thereafter with an overfeed of 40-80% at 230.degree.-240.degree. C.
The titre range of 170-260 dtex, in particular 170-210 dtex preferably 170-190 dtex, has proved particularly advantageous, since titres exceeding 260 dtex are unsuitable for reasons of weaving technology for tire cords and since with an elongation of 80% they require too high a force. The threads have to lie as flat as possible in the cord fabric, so that at the warp/weft crossing points there do not occur any undesirable raised portions which are unevenly coated in the dipping process. At a titre below 170 dtex, the tenacity is too low and the reversibility is inadequate. It has, moreover, proved to be expedient to effect a temperature treatment directly after the swirling, in which arrangement, an inadequate triggering of shrinkage occurs at temperatures below 230.degree. C., and over 240.degree. C., the polymer is already damaged. At the same time, an overfeed of 40-80%, in particular of 50-70% is expedient.
It has also proved expedient to effect the swirling in a swirling nozzle, in particular in a closed swirling nozzle at 0.5 to 3 bar, in particular at 1 to 2 bar. In an open swirling nozzle, a reliable swirling is not always ensured at low yarn tensions (only the running off tension) and at the applied pressure, since the filaments may be blown out of the nozzle.
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Fischer Klaus
Schaffner Paul
Gray J. M.
Rhone-Poulenc Viscosuisse SA
Ryan Patrick
Striker Michael J.
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