Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Woven fabric – Woven fabric is characterized by a particular or...
Reexamination Certificate
2000-01-14
2003-03-18
Morris, Terrel (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Woven fabric
Woven fabric is characterized by a particular or...
C442S134000, C442S135000, C442S243000, C442S324000, C442S326000, C442S209000, C428S911000, C002S002500
Reexamination Certificate
active
06534426
ABSTRACT:
BACKGROUND OF THE INVENTION
There is a need for protective garments exhibiting improved penetration resistance from knife blades, and more particularly, for garments which are flexible, soft and comfortable to be worn for protection from knife-stab threats such as stiletto, kitchen knife, butterfly knife and boning knife. This invention relates to composites that protect from such penetration, such as by stabs or thrusts from such knives or knife blades.
U.S. Pat. No. 5,622,771, issued Apr. 22, 1997 on the application of Chiou, Foy, and Miner, discloses a penetration resistant article made from tightly woven aramid yarn having a low linear density.
U.S. Pat. No. 5,185,195, issued Feb. 9, 1993 on the application of Harpell et al., discloses a penetration resistant construction wherein adjacent layers of woven aramid or linear polyethylene fabric are affixed together by regular, close, paths. The affixing is preferably by means of stitching.
European Patent Application No. 769,671, published Apr. 23, 1997 discloses an anti-stab material made from woven fabrics using metallic and non-metallic components without disclosed regard for tightness of weave.
SUMMARY OF THE INVENTION
This invention relates to a flexible, matrix-resin-free composite especially resistant to penetration by knife stab comprising a plurality of layers of fabric wherein the areal density of the fabric layers is at least 3.0 kg/m
2
and the fabric is made from continuous filament yarns having a tenacity of at least 10 grams per dtex and a tensile modulus of at least 150 grams per dtex woven with a fabric tightness factor of 0.2 to 0.65. The invention also relates to such a penetration resistant composite wherein the layers are joined only at edges of the composite in a manner such that adjacent layers of the fabric are free to move relative to each other.
DETAILED DESCRIPTION
The protective composite of this invention was specially developed to provide protection from penetration by knife blade stabs or thrusts as opposed to protection from ice pick threats. There has been considerable effort expended in the past on improvement of protection from penetration by knife stabs; and the assumption has been that improved stab resistance will be obtained from use of fabrics that are more tightly woven. The inventor herein has found that assumption to be incorrect insofar as knife stabs are concerned. He has discovered that a woven fabric composite with a loose weave, quite surprisingly, exhibits improved resistance to penetration by knife stabs.
The inventor herein has discovered that the knife stab penetration resistance of a fabric composite is dramatically improved when yarns used to make the fabric of the article are woven to a tightness factor of less than 0.65. It is believed that a tightness factor as low as 0.20 will provide improved knife stab resistance. Up to the present invention, penetration resistant fabrics were tightly woven or impregnated by a matrix resin or both. In efforts completely opposite to the current technical understanding, the inventor herein, discovered that matrix-resin-free fabrics with a low fabric tightness factor exhibit improved knife stab penetration resistance. While any fabrics with any reduced tightness factor are expected to exhibit some improvement, the most improvement is found at a tightness factor of less than 0.65. As the tightness factor is further reduced, knife stab resistance is further improved until the tightness factor reaches about 0.20, where the fabric weave is so loose that an unacceptably high areal density would be required for effective protection.
Ballistic garments are generally made using several layers of protective fabric and the several layers are nearly always fastened together in a way to hold faces of the adjacent layers in fixed position relative to each other. It has been found that knife stab penetration resistance is improved if adjacent layers in a protective composite are not held together; but are free to move relative to each other. When adjacent layers are stitched closely together, knife stab penetration resistance is decreased.
The invention herein is constructed entirely of woven fabric without rigid plates or platelets and without matrix resins impregnating the fabric materials. The articles of this invention are more flexible, lighter in weight, softer to the touch, more comfortable to be worn, and more pliable than penetration resistant constructions of the prior art offering comparable knife-stab protection.
Fabrics of the present invention are made, in whole or in part, from yarns having a tenacity of at least 10 grams per dtex and a tensile modulus of at least 150 grams per dtex. Such yarns can be made from aramids, polyolefins, polybenzoxazole, polybenzothiazole, and the like; and, if desired, the fabrics can be made from mixtures of such yarns.
By “aramid” is meant a polyamide wherein at least 85% of the amide (—CO—NH—) linkages are attached directly to two aromatic rings. Suitable aramid fibers are described in Man-Made Fibers—Science and Technology, Volume 2, Section titled Fiber-Forming Aromatic Polyamides, page 297, W. Black et al., Interscience Publishers, 1968. Aramid fibers are, also, disclosed in U.S. Pat. Nos. 4,172,938; 3,869,429; 3,819,587; 3,673,143; 3,354,127; and 3,094,511.
Additives can be used with the aramid and it has been found that up to as much as 10 percent, by weight, of other polymeric material can be blended with the aramid or that copolymers can be used having as much as 10 percent of other diamine substituted for the diamine of the aramid or as much as 10 percent of other diacid chloride substituted for the diacid chloride of the aramid.
Para-aramids are the primary polymers in aramid yarn fibers of this invention and poly(p-phenylene terephthalamide) (PPD-T) is the preferred para-aramid. By PPD-T is meant the homopolymer resulting from mole-for-mole polymerization of p-phenylene diamine and terephthaloyl chloride and, also, copolymers resulting from incorporation of small amounts of other diamines with the p-phenylene diamine and of small amounts of other diacid chlorides with the terephthaloyl chloride. As a general rule, other diamines and other diacid chlorides can be used in amounts up to as much as about 10 mole percent of the p-phenylene diamine or the terephthaloyl chloride, or perhaps slightly higher, provided only that the other diamines and diacid chlorides have no reactive groups which interfere with the polymerization reaction. PPD-T, also, means copolymers resulting from incorporation of other aromatic diamines and other aromatic diacid chlorides such as, for example, 2,6-naphthaloyl chloride or chloro- or dichloroterephthaloyl chloride or 3,4′-diaminodiphenylether. Preparation of PPD-T is described in U.S. Pat. Nos. 3,869,429; 4,308,374; and 4,698,414.
By “polyolefin” is meant polyethylene or polypropylene. By polyethylene is meant a predominantly linear polyethylene material of preferably more than one million molecular weight that may contain minor amounts of chain branching or comonomers not exceeding 5 modifying units per 100 main chain carbon atoms, and that may also contain admixed therewith not more than about 50 weight percent of one or more polymeric additives such as alkene-1-polymers, in particular low density polyethylene, propylene, and the like, or low molecular weight additives such as anti-oxidants, lubricants, ultra-violet screening agents, colorants and the like which are commonly incorporated. Such is commonly known as extended chain polyethylene (ECPE). Similarly, polypropylene is a predominantly linear polypropylene material of preferably more than one million molecular weight. High molecular weight linear polyolefin fibers are commercially available. Preparation of polyolefin fibers is discussed in U.S. Pat. No. 4,457,985.
Polybenzoxazole and polybenzothiazole are preferably made up of mers of the following structures:
While the aromatic groups shown joined to the nitrogen atoms may be heterocyclic, they are preferably carbocyclic; and while they may be fused
E. I. du Pont de Nemours and Company
Guarriello John J.
Morris Terrel
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