Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1999-10-27
2000-12-05
Edwards, Newton
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
428370, 428221, 428395, 139383A, 28246, 28240, D01F 600
Patent
active
061564265
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a 100-400 dtex tyre cord fabric weft yarn comprising a heat-protected nylon-6,6 multifilament and to a process for producing a weft yarn.
Weft yarn for tyre cord fabric and a process for making it from polyester POY are known (WO-A-96/2391). The yarns produced from polyester POY filaments have very low thermal stability. Lower spinning speeds do not yield any improvement. The filament yarn turns brittle on the relaxation heater at 220.degree. C., losing a large proportion of its strength and residual elongation at break.
It is an object of the present invention to provide a PA 66 tyre cord fabric weft yarn having high thermal stability, a defined reversibility limit, adequate tenacity and slip resistance and also a high ultimate tensile stress elongation.
It is a further object to provide a process for producing tyre cord weft yarns which, following impregnation, exhibit an ultimate tensile stress elongation which ensures spreading of the cord threads in tyre manufacture without weft thread breakages.
This object is achieved according to the invention when the base yarn combines the following features:
Such a yarn has the advantage of facilitating homogeneous warp thread distribution in tyre construction due to pronounced flow characteristics in the fabric. In addition, this yarn constitutes a single-component weft yarn which does not give rise to unpleasant and harmful dust in weaving, as is customary with the use of natural fibres. It is additionally intended to withstand high thermal stress during the impregnating step, to exhibit hardly any widthwise contraction and, in the construction of a tyre, to facilitate very homogeneous cord warp thread spreading and so be universally useful for tyre cord fabrics based on nylon, polyester and aramid.
At an extension of 80%, preferably 90-150%, a load of 6 cN/tex to 12 cN/tex, preferably 6-10 cN/tex, is advantageous. Loads higher than 12 cN/tex at the stated extension have the disadvantage of inhomogeneous warp thread distribution when the radial tyre expands on the tyre construction machine. Loads below 6 cN/tex at the stated extension lead, not only under uniform but also under local loads, for example in the course of storage of fabric bales, to irreversible weft thread stretching and so to inadequate stability with regard to warp thread parallelity. This gives rise to poor or unusable tyre carcasses.
An ultimate tensile stress elongation of <300%, preferably 180-280%, is advantageous. Ultimate tensile stress elongations of more than 300% lead to excessively high stretching under customary loads in the production of tyre cord fabrics; an ultimate tensile stress elongation of less than 150%, by contrast, leads to insufficient extensibility reserve, resulting in insufficient weft deformation or even weft yarn breakages in the fabric. In both cases, the resulting tyre carcasses are inhomogeneous and so the tyres which are manufactured therefrom are as well.
It is advantageous for the weft yarn to have a tenacity of at least 14 cN/tex in order that the peak stresses containing during the various processing steps cannot lead to weft yarn breakages.
A reversibility limit of 5 to 10 cN/tex is particularly advantageous. A reversibility limit of less than 5 cN/tex means that there is no way of ensuring dimensional stability on weft insertion or fabric width stability until processing into the tyre. If the reversibility limit is greater than 10 cN/tex, the force which results during the vulcanization step is not sufficient to spread the individual cord threads uniformly.
A thermal shrinkage force of 0.15 to 0.8 cN/tex has the advantage of virtually no widthwise contraction occurring during the impregnating step and hence of ensuring a homogeneous cord warp thread distribution, especially in the case of fabrics having weft yarn laid-in selvages, during this step as well; a thermal shrinkage force of greater than 0.8 cN/tex will, despite the forces applied by spreading rolls to the weft threads during the impregnating step, result in t
REFERENCES:
patent: 5634249 (1997-06-01), Ballarati
patent: 5657798 (1997-08-01), Krummheuer et al.
Lang Bruno
Schaffner Paul
Edwards Newton
Rhodia Filtec AG
Striker Michael J.
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