Light weight filter felt
AssigneeE. I. Du Pont de Nemours and Company
InventorHerman H. Forsten
Life of this patent
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Abstract
Nonwoven fabrics of poly(m-phenylene isophthalamide) having a cross-machine modulus greater than 40, and good resistance to abrasion that is useful as a gas filtration substrate, and the process of producing such a fabric by heating an entangled web while stretching the fabric transversely 5 to 15% for a time sufficient to increase the crystallinity index at least about 0.05 units.
Claims3
A fabric consisting essentially of entangled staple fibers of poly(m-phenylene isophthalamide), said staple fibers having a length of 1 to 5 cm, the fibers having a crystallinity index of at least about 0.50, the fabric having a basis weight of between 200 and 350 g/m.sup.2, an air permeability of 12 to 30 m.sup.3 /min/m.sup.2, a cross-machine-direction modulus of greater than 40 Kg/cm.sup.2 and an abrasion resistance such that it will go through at least 500 cycles before failure in the Taber abrasion test.
A process for the production of a non-woven fabric having a high modulus and a high air permeability, and suitable for use in the production of filtration air bags which comprises hydraulically entangling the fibers of a batt consisting essentially of staple fibers having a length of 1 to 5 cm of poly(m-phenylene isophthalamide), said staple fibers having a crystallinity index of at least about 0.4, heating the fabric while the fabric is under low or no compressive forces in the thickness dimension to a temperature in the range of 260.degree. to 360.degree. C. while maintaining the length of the fabric, and while transversely stretching the fabric 5 to 15%, for a time sufficient to increase the crystallinity index at least about 0.05 units.
Dependencies are inferred from the claim text.