Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Patent
1997-02-06
1997-12-02
Bell, James J.
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
139421, 2807431, 442184, B60R 2120
Patent
active
056933924
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an uncoated fabric with linen or ripstop binding of a polyamide filament yarn with a fibril titer of 1.5 to 7 dtex, a strength of 50 to 80 cN/tex and an elongation of 15 to 30%, for producing an impact gas bag (airbag), and to a process for producing it.
Uncoated fabrics of polyamide 6.6 are known (European Patent Application EP-A 0 436 950). To attain low air permeability, it is evidently necessary for use in the fabric to use a filament with a hot air shrinkage of 6 to 15%, measured at 160.degree. C. The grey cloth is then shock-shrunk in an aqueous bath in a temperature range between 60.degree. and 140.degree. C. By the known process, with a known linen binding, however, air permeabilities of only 3 l/dm.sup.2 /min and more at 500 Pa are attained. Such intrinsically low air permeabilities, which are demanded by airbag system manufacturers, are adequate for many applications; because of the high thermal shrinkage and the attendant high windup tension, however, the yarns required for this can be made by the stretch-spinning process only with great difficulty, if at all. When yarns with high shrinkage (over 6%) are used, special precautions must be taken in their manufacture so as to fix the thermal shrinkage by severe, uniform cooling, without causing differences in tension. Either the stretching must be done by yarn sheet with yarn-tension-controlled cooling, or it is typically done by cop winding with vertical single-yarn stretching. In practice, such yarns require rewinding from cop to cylinder or in fact require yarn sheet stretching with tension-controlled cooling.
The object of the invention is to furnish a fabric that has an air permeability which is nearly equivalent to that of a coated fabric and that can be manufactured in a simple and thus also economical way. The air bag fabric should have a very low air permeability, a high dimensional stability, and a high tear propagation strength.
Another object is to find a replacement of uncoated fabric instead of coated fabric for producing an air bag fabric. Not only is coating a complicated process step that increases the expense, but the resultant fabric also has a foldability that is poorer by approximately 10% to 15%, and has a large packing volume.
The object according to the invention is attained in that the fabric simultaneously has an air permeability of <1/dm.sup.2 /min, a residual boiling shrinkage of <2%, and a tear propagation strength in warp and weft of >110N. It is expedient if the air permeability is from 1 to 3 1/dm.sup.2 /min.
It is expedient if the fabric, in the 5 cm fabric strip test, has a tear strength of >2500N. This assures the integrity of the fabric in the airbag upon impact.
For the process for producing the uncoated fabric, a polyamide multifilament yarn produced in a stretch-spinning process with a fibril titer of 1.5 to 7 dtex has proved especially advantageous. It is particular advantageous if the polyamide filament has a hot air shrinkage of <6%, measured at 160.degree. C. in air and at a bias of 0.5 cN/tex, and a minimum shrinkage force of 0.20 cN/tex, and is later treated in fabric form in a closed container at a temperature of 80.degree. to 160.degree. C. and a relative humidity of 90 to 100%.
Surprisingly, it has been found that even with a reduced-shrinkage starting material, very low air permeabilities are attainable. Air permeabilities above 3 l/dm.sup.2 /min are moreover only limitedly tolerable even for modern tripping systems having fewer and finer particles; air permeabilities below 3 l/dm.sup.2 /min and preferably below 2.5 l/dm.sup.2 /min and less have proved to be excellent for air bag fabric.
The air permeability of the fabric is measured by DIN 53887 at an air pressure of 500 Pa.
The thermal shrinkage and the boiling shrinkage were measured by DIN 53866; in the thermal shrinkage, the air temperature was 160.degree. C. and the bias was 0.5 cN/tex. The tear propagation strength was measured by DIN 53859 T2; the tear strength and elongation to rupture were measured by
Bergen Eberhard
Lalonde Remi
Lang Bruno
Bell James J.
Rhone-Poulenc Viscosuisse S.A.
Striker Michael J.
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