WO1999036606A1

WO1999036606A1 - Ballistic-resistant textile articles made from cut-resistant fibers

Info

Publication number: WO1999036606A1
Application number: PCT/US1999/001074
Authority: WO
Inventors: Leslie H. Lanieve, Iii; O. Oakley Etheridge, Jr.
Original assignee: Hna Holdings, Inc.
Priority date: 1998-01-20
Filing date: 1999-01-19
Publication date: 1999-07-22
Also published as: WO1999036606A8; AU2652799A

Abstract

A textile article having improved ballistic-resistance contains multiple layers of a cut-resistant fabric, wherein the cut-resistant fabric is formed from at least one cut-resistant fiber, the cut-resistant fiber being formed from a blend containing: (i) at least one fiber-forming polymer and (ii) an effective amount of at least one hard filler having a Mohs Hardness value of at least about 3.0. Alternatively, a cut-resistant sheat/core fiber may be used comprising a core formed from polymer/filler blend and polymer sheat. In addition to having improved ballistic-resistance, the textile article is also flexible, lightweight and highly mobile and can be composed of relatively inexpensive materials. The ballistic-resistant textile article is used to provide ballistic-protection to a designated site, which is preferably a portion of the human body, e.g., the heart and/or lungs. The ballistic-resistant textile article can be in the form of protective garments (e.g., vests), automobile door panels, aircraft padding, helmets, briefcases, and the like.

Description

BALLISTIC-RESISTANT TEXTILE ARTICLES MADE FROM CUT-RESISTANT FIBERS

BACKGROUND OF THE INVENTION The present invention relates to ballistic-resistant articles. More particularly, this invention relates to ballistic-resistant textile articles made from cut-resistant fibers. Ballistic-resistant articles such as, for example, bulletproof vests, bulletproof jackets, helmets, padding in helicopters and other aircraft, vehicle door panels, briefcases, umbrellas, parachutes and protective garments, are useful in protecting the body and/or other desired objects from bullets, knives, and explosives. Such articles are known in the art. For example, ballistic-resistant garments and the uses thereof are disclosed in, e.g., U.S. Patent Nos. 5,480,706; 4,403,012; 4,457,985; 4,623,574; 4,748,064; 4,737,402; 4,613,535; 4,413,110; 3,516,890; 4,836,084; 4,681,792; and 4,732,803; and in Japanese Kokai Patent Application No. Sho 62[1987]-62198.

Ballistic-resistant articles have been made from metal and ceramic sheets. A problem with these materials is that both metal sheets and ceramic sheets are heavy and lack mobility. Ceramic sheets are further disadvantageous in that when such sheets are shattered by a bullet, knife or explosion, the resulting flying ceramic fragments are dangerous.

Protective articles have also been made from high tenacity nylon fibers, Kevlar® aramid fibers, and/or combinations thereof. High-tenacity nylon and Kevlar® aramid fibers are flexible and can form protective clothing having relatively high mobility. However, these fibers also have drawbacks. For example, high- tenacity nylon fibers offer relatively poor protection against penetration by bullets. Thus, to be sufficiently bullet-proof, a fabric article (e.g., a garment) made from high- tenacity nylon fibers must contain a relatively high number of laminated high-tenacity nylon sheets. This results in increased thickness and weight and reduced mobility. Protective articles made from Kevlar® aramid fibers have adequate protection against bullets, but such structures are easily penetrated with sharp objects such as knives, i.e., such structures are insufficiently cut-resistant. In addition, Kevlar® fibers are relatively expensive materials. A primary object of this invention is to provide an article which has improved ballistic-resistance, i.e., improved resistance to penetration by bullets, sharp objects such as knives, and fragments of explosives.

A further object of this invention is to provide an article having improved ballistic-resistance, wherein the article is also lightweight and has improved flexibility and mobility.

Yet another object of this invention is to provide a lightweight, flexible and mobile article having improved ballistic-resistance, wherein the article is formed of relatively inexpensive materials. A still further object of this invention is to provide an article having the characteristics set forth in the preceding objects, wherein the article is a textile article.

A further object of this invention is to provide a textile article having the characteristics set forth in the preceding objects, wherein the article is in the form of a bulletproof garment (e.g., a vest or a jacket), a helmet, padding in helicopters and other aircraft, a vehicle door panel, a briefcase, an umbrella, or a parachute.

Another object of this invention is to provide a method of using a textile article having the aforementioned characteristics.

These and other objects which are achieved according to the present invention can be discerned from the following description.

SUMMARY OF THE INVENTION The present invention is based on the discovery that a textile article formed from a particular type of cut-resistant fiber will have improved ballistic resistance over a textile article formed from conventional fibers which are typically used to form ballistic articles.

Accordingly, one aspect of the present invention is directed to a ballistic- resistant textile article containing multiple layers of a cut-resistant fabric, wherein the cut-resistant fabric is formed from at least one cut-resistant fiber, the cut-resistant fiber being formed from a blend comprising (i) at least one fiber- forming polymer and (ii) an effective amount of at least one hard filler having a Mohs Hardness value of at least about 3.0. Non- limiting examples of specific ballistic-resistant textile articles within the scope of the present invention include bulletproof vests and other protective garments, helmets, padding in helicopters and other aircraft, vehicle door panels, briefcases, umbrellas, parachutes and the like. Another aspect of the present invention is directed to a method of using the ballistic-resistant textile article of this invention to protect a designated site. Typically, the designated site is composed of one or more portions of the human body, particularly those portions containing vital organs such as the heart or the lungs. Broadly, the method of this invention involves disposing the ballistic-resistant article relative to the designated site so as to provide such site with ballistic protection.

In addition to having improved ballistic-resistance, the textile article of this invention is also lightweight, highly flexible and highly mobile, and composed of relatively inexpensive materials.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a textile article having improved ballistic- resistance and a method of using such article to protect a designated site.

With respect to the textile article of this invention, the term "ballistic- resistance" as used herein means that the article is resistant to penetration by (i) moving projectiles (e.g., bullets), (ii) sharp objects such as knives, and (iii) fragments generated from explosions (e.g., shell fragments).

The textile article of this invention contains multiple layers of a cut-resistant fabric formed from at least one cut-resistant fiber. With respect to the fabric and fiber(s) used in the present invention, the term "cut-resistant" as used herein means that such fabric and fiber(s) are resistant to cutting by sharp objects, e.g., a knife. In addition, as used herein, the term "fiber" includes not only conventional single fibers and filaments, but also yarns made from a multiplicity of these fibers. In general, yarns are used to make apparel, fabrics and the like.

The cut-resistant fiber(s) used to make the fabric layers in the textile article of this invention is formed from a blend containing (i) at least one fiber- forming polymer and (ii) an effective amount of at least one hard filler having a Mohs Hardness value of at least about 3.0. In preferred embodiments of this invention, the hard filler is distributed uniformly in such polymer/filler blend.

As used herein with respect to the amount of the hard filler, the term "effective amount" means that amount of the hard filler which is sufficient to cause the cut- resistance of the fiber formed from the filler and the fiber- forming polymer(s) to be higher than the cut-resistance of a fiber formed from the fiber-forming polymer(s) in the absence of the hard filler.

In preferred embodiments of this invention, the cut-resistant fiber is that cut- resistant fiber which is disclosed in copending, commonly assigned U.S. Patent Application Serial No. 08/752,297, filed November 19, 1996, which is hereby incorporated by reference herein.

The cut-resistant fiber(s) used in the present invention may be made of any conventional fiber-forming polymer and may be produced by any of the methods conventionally used in making fibers. The fiber-forming polymer is preferably melt- processable, in which case, the cut-resistant fiber is typically made by melt spinning. For polymers that cannot be spun into fibers in the melt, wet spinning and dry spinning may also be used to produce fibers having improved cut resistance. Amorphous polymers, semi-crystalline polymers and liquid crystalline polymers may all be used in this invention. Of these, semi-crystalline and liquid crystalline polymers are preferred.

In one preferred embodiment of this invention, the fiber- forming polymer is an isotropic semi-crystalline polymer. The term "isotropic" means that the polymer is not a liquid crystalline polymer (liquid crystalline polymers are anisotropic). Preferably, the isotropic semi-crystalline polymer is melt processable, i.e., it melts in a temperature range which makes it possible to spin the polymer into fibers in the melt phase without significant decomposition. Semi-crystalline polymers which are highly useful include poly(alkylene terephthalates), poly(alkylene naphthalates), poly(arylene sulfides), aromatic, aliphatic and aliphatic-aromatic polyamides, polyolefins, and polyesters composed of monomer units derived from cyclohexanedimethanol and terephthalic acid.

Non-limiting examples of specific isotropic semi-crystalline fiber- forming polymers include poly(ethylene terephthalate), poly(butylene terephthalate), poly(ethylene naphthalate), poly(phenylene) sulfide, poly(l,4-cyclohexanedimethanol terephthalate) (wherein the 1 ,4-cyclohexanedimethanol is a mixture of cis and trans isomers), nylon 6, nylon 6,6, and nylon 6,10. Polyolefms, particularly polyethylene and polypropylene, are other semi-crystalline polymers that may be used in this invention. Extended-chain polyethylene, which has a high tensile modulus, is already cut-resistant but can be made even more cut-resistant by the addition of particles. Extended-chain polyethylene can be made by the gel spinning or melt spinning of very high or ultrahigh molecular weight polyethylene.

The preferred isotropic semi-crystalline fiber-forming polymer for use in the present invention is poly(ethylene terephthalate).

Isotropic polymers that cannot be processed in the melt can also be used, as, for example, rayon and cellulose acetate, which are typically dry spun using acetone as a solvent, and poly[2,2^*-(m-phenylene)-5,5'-dibenzimidazole], generally referred to as polybenzimidazole, which is typically wet spun using N,N'-dimethylacetamide as a solvent. Aromatic polyamides other than the polymer of terephthalic acid and p- phenylene diamine (e.g., polymers of terephthalic acid and one or more aromatic diamines) may be soluble in polar aprotic solvents, such as N-methylpyrrolidone, and can be wet spun with added particles to yield cut-resistant fibers. Amorphous, non- crystalline, isotropic polymers, such as the copolymer of isophthalic acid, terephthalic acid and bisphenol A (polyarylate) may also be filled and utilized in this invention. In another preferred embodiment, the cut-resistant fiber is made from a liquid crystalline polymer (LCP). Liquid crystalline polymers form fibers having very high tensile strength and/or modulus. The liquid crystalline polymer may be processable in the melt (i.e., thermotropic), in which case melt spinning is the preferred method of making the fiber. However, polymers that cannot be processed in the melt may also be used. Thus, polymers that exhibit liquid crystalline behavior in solution can be blended with a hard filler and then can be wet or dry spun to yield cut-resistant fibers in accordance with the present invention. For example, the aromatic polyamide made from p-phenylenediamine and terephthalic acid (as, for example, polymers sold under the KEVLAR® trademark) can be filled and wet spun (i.e., by dry-jet wet-spinning from a concentrated sulfuric acid solution) to yield a cut-resistant fiber, provided that the hard filler does not react with or dissolve in the solvent. Other aromatic polyamides that are soluble in polar aprotic solvents, such as N-methylpyrrolidone, may also be spun into cut-resistant fibers. These may not be liquid crystalline under some or all conditions, but they still yield high modulus fibers. Some may exhibit lyotropic liquid crystalline phases at some concentrations and in some solvents, but isotropic solutions at other concentrations or in other solvents.

The preferred liquid crystalline polymers for use as the fiber-forming polymer in this invention are thermotropic LCPs. Such thermotropic LCPs include, e.g., aromatic polyesters, aliphatic-aromatic polyesters, aromatic poly(esteramides), aliphatic-aromatic poly(esteramides), aromatic poly(esterimides), aromatic poly(estercarbonates), aromatic polyamides, aliphatic-aromatic polyamides and poly(azomethines). The preferred thermotropic liquid crystalline polymers for use in the present invention are aramid polymers, aromatic polyesters, and poly(esteramides) which form liquid crystalline melt phases at temperatures of less than about 360°C and include one or more monomer units derived from terephthalic acid, isophthalic acid, 1,4-hydroquinone, resorcinol, 4,4'-dihydroxybiphenyl, 4,4'-biphenyldicarboxylic acid, 4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 2,6-naphthalenedicarboxylic acid, 2,6-dihydroxynaphthalene, 4-aminophenol, and 4-aminobenzoic acid. Some of the aromatic groups may include substituents which do not react under the conditions of the polymerization, such as, e.g., lower alkyl groups having from 1 to 4 carbon atoms, aromatic groups, fluorine, chlorine, bromine and iodine.

The most preferred liquid crystalline polyester comprises monomer repeat units derived from 4-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, as taught in U.S. Patent No. 4,161,470, which is hereby incorporated by reference herein. Preferably, monomer units derived from 4-hydroxybenzoic acid comprise from about 15% to about 85% of the polymer on a mole basis, and monomer units derived from 6-hydroxy-2-naphthoic acid comprise from about 85% to about 15% of the polymer on a mole basis. Most preferably, the polymer comprises about 73% monomer units derived from 4-hydroxybenzoic acid and about 27% monomer units derived from 6- hydroxy-2-naphthoic acid, on a mole basis. This polymer is available in fiber form under the VECTRAN® trademark from Hoechst Celanese Corporation, Charlotte, North Carolina. Other preferred liquid crystalline polyesters or poly(esteramides) comprise the above-recited monomer units derived from 6-hydroxy-2-naphthoic acid and 4- hydroxybenzoic acid, as well as monomer units derived from one or more of the following monomers: 4,4'-dihydroxybiphenyl, terephthalic acid and 4-aminophenol. A preferred polyester comprising these monomer units is derived from 4- hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 4,4'-biphenol and terephthalic acid, as taught in U.S. Patent No. 4,473,682, which is hereby incorporated by reference herein, with the polymer comprising these monomer units in a mole ratio of about 60:4: 18:18 being particularly preferred. A preferred poly(esteramide) comprises monomer units derived from 4- hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 4,4'-biphenol and 4-aminophenol, as taught in U.S. Patent No. 5,204,443, which is hereby incorporated by reference herein; a highly preferred composition comprises these monomer units in a mole ratio of about 60:3.5:18.25:13.25:5. High strength fiber-forming polymers such as aramid and high modulus ultra high molecular weight polyethylene are particularly preferred for use in this invention because they permit construction of lighter weight, more flexible structures with higher ballistic limits. These polymers can be filled with the hard particles described hereinbelow to improve the ballistic limits of the materials. Distributed within the blend containing the fiber- forming polymer is a hard filler which imparts cut-resistance to the fiber. The hard filler may be a metal, such as an elemental metal or metal alloy, or nonmetallic, e.g., ceramic or crystalline materials. Generally, any filler may be used that has a Mohs hardness value of about 3 or more. Particularly suitable fillers have a Mohs Hardness value of greater than about 4, and preferably greater than about 5. Suitable metals include, e.g., tungsten, copper, brass, bronze, aluminum, steel, iron, monel, cobalt, titanium, magnesium, silver, molybdenum, tin and zinc. Suitable metal compounds include metal oxides, such as aluminum oxide, metal carbides, such as tungsten carbide, metal nitrides, metal sulfides, metal silicates, metal suicides, metal sulfates, metal phosphates, and metal borides. Other suitable fillers include silicon dioxide and silicon carbide. Non- limiting examples of suitable crystalline materials include baddeleyite, chloritoid, clinozoisite, chondrodite, euclasite, petalite, sapphire, spodumene, staurolite, and clay. Suitable ceramic materials include, e.g., glass and alumina. Most preferably, the hard filler used in the fiber- forming polymer is calcined aluminum oxide.

The hard filler is preferably used in the form of particles, which are preferably distributed uniformly in the polymer/filler blend used to form the cut-resistant fiber(s). A powder form of the hard filler is generally suitable. The filler particles may be in the form of flat particles (i.e., platelets), elongated particles (i.e., needles), round particles or irregularly shaped particles. Preferably, the particles are in the form of platelets.

The particle size, particle size distribution, and the quantity of particles are all important parameters in obtaining good cut-resistance while preserving fiber mechanical properties.

For flat or elongated particles, the particle size refers to the length along the long axis of the particle (i.e., the long dimension of an elongated particle or the average diameter of the face of a platelet). Selection of an appropriate particle size depends on the processing and on the fiber diameter. The filler particles should be small enough to easily pass through the spinneret apertures. The particles should also be small enough that the fiber tensile properties do not appreciably deteriorate. For textile fibers, (i.e. fibers having a denier in the range of about 1.5 to about 15 dpf), the particles should be filtered or sieved in such a way that particles larger than about 6 microns are excluded. In general, the particles should have an average diameter of less than about 20 microns, preferably in the range of about 0.05 to about 5 microns and in specific cases, about 0.2 to about 2 microns. For elongated particles, the long dimension should fit through the spinneret holes. Therefore, the average particle length of an elongated particle should be less than about 20 microns, and preferably is in the range of about 0.05 to about 5 microns and in specific cases, about 0.2 to 2 microns.

The hard filler particles used in the present invention preferably have an average particle size of from about 1 to about 5 microns, more preferably from about 1 to about 3 microns. As mentioned previously herein, the effective amount of the hard filler in the polymer/filler blend is that amount which will increase the cut-resistance of the fiber formed from the blend as compared to the cut-resistance of a fiber formed from the fiber-forming polymer in the absence of the hard filler. Specifically, the effective amount of hard filler used in the fiber- forming polymer/filler blend is preferably that amount which will increase the cut resistance of the fiber by at least 10%, as determined by ASTM F1790 (also known as the "Ashland Cut Protection Performance Test") or other tests generally accepted in the industry. More preferably, the amount of hard filler used in the polymer/filler blend is that amount which will increase the cut resistance of the fiber by at least 20%, even more preferably by at least 35% and most preferably by at least 50%, as measured by the aforementioned tests, particularly ASTM F1790. The amount of hard filler used in the fiber- forming polymer/filler blend should not be such as to decrease the tensile properties of the fiber (tenacity and modulus) by more than about 50%. More preferably, the amount of filler used should not decrease the tensile properties of the fiber by more than about 25%. Most preferably, the amount of hard filler used should be such that there will not be a significant change in the fiber's tensile properties (i.e., less than about 10% decrease in properties).

On a weight basis, the fiber-forming polymer/filler blend contains preferably from about 80.0% to about 99.95% of the polymer and from about 0.05% to about 20% of the filler, more preferably from about 80% to about 99.9% of the polymer and from about 0.1% to about 20% of the filler. On a volume basis, the blend preferably contains from about 97% to about 99.99% of the polymer and from about 0.01% to about 3.0%) of the filler, more preferably from about 97% to about 99.97% of the polymer and from about 0.03% to about 3.0% of the filler, with the proviso that the amount of filler is within the weight ranges stated previously. Thus, for a dense filler, such as tungsten powder, in poly(ethylene terephthalate), the amount of filler corresponding to the volume percentages stated above but expressed on a weight basis, is preferably in the range of from about 0.14% to about 20% by weight, more preferably in the range of from about 0.42% to about 20% by weight, and most preferably in the range of from about 0.7% to about 14% by weight. For PET, good cut-resistant properties are obtained with about 0.7% by volume of tungsten filler, corresponding to about 10% by weight of tungsten filler. For thermotropic liquid crystalline polymers, improved cut resistance can be obtained with from about 0.07% to about 0.14%) by volume of tungsten filler, corresponding to about 1% to about 2% by weight of the filler.

The cut-resistant fiber(s) used in the present invention is preferably made in accordance with the methods taught in copending, commonly assigned U.S. Patent Application Serial No. 08/752,297, filed November 19, 1996, which was previously incorporated by reference herein.

The hard filler may be added to the fiber-forming polymer by any of the standard methods of adding a filler to a resin. For example, the combining of the hard filler and the fiber-forming polymer can be conveniently effected in an extruder, e.g., a twin screw extruder, by mixing the hard filler with molten polymer under conditions sufficient to provide a uniform distribution of the filler in the polymer. The hard filler may also be present during the manufacture of the fiber- forming polymer or may be added as the fiber- forming polymer is fed into the extruder of fiber-spinning equipment, in which case the blending and spinning steps are nearly simultaneous. When the filler particles are distributed uniformly in the polymer melt, the filler particles will also generally be distributed uniformly throughout the fiber, except that elongated and flat particles are oriented to some extent because of the orientation forces occurring during fiber spinning. Some migration of the particles to the surface of the fiber may also occur. Thus, while the distribution of particles in the fibers is described as "uniform", the word "uniform" should be understood to include non- uniformities that occur during the processing (e.g., melt spinning) of a uniform polymer blend. Such fibers would still fall within the scope of this invention.

The cut-resistant fiber(s) will preferably have a denier in the range of from about 1 to about 50 dpf, more preferably in the range of from about 2 to about 20 dpf, and most preferably from about 3 to about 15 dpf.

The cut-resistant fiber(s) used in the present invention may be a monocomponent fiber or a multicomponent fiber such as, e.g., a bicomponent fiber. A preferred cut-resistant bicomponent fiber for use in this invention has a sheath/core structure. The sheath component of such bicomponent fiber preferably contains at least one unfilled fiber-forming polymer, and the core component preferably contains the blend composed of the at least one fiber- forming polymer and the at least one hard filler described previously herein. More preferably, the bicomponent fiber will contain from about 10% to about 60% by volume of the sheath component and from about 40%) to about 90% by volume of the core component. Most preferably, the bicomponent fiber will contain about 50% by volume of the sheath component and about 50%) of the core component. Preferably, the sheath component will contain 100% by weight of the unfilled fiber- forming polymer(s). The core component will preferably contain from about 80% to about 98%> by weight of the fiber-forming polymer(s) and from about 2% to about 20%> by weight of the filler. More preferably, the core component will contain about 88%o by weight of the fiber- forming polymer(s) and about 12% by weight of the filler. The fiber- forming polymer(s) in the sheath component and the fiber-forming polymer(s) in the core component may be the same or different. Any of the previously recited fiber-forming polymers may be used in the sheath and core components of the bicomponent fiber. In addition, any of the previously recited hard fillers may be used in the core component of such bicomponent fiber. The preferred hard filler is alumina. The cut-resistant fiber(s) may also be a monofilament or multifilament wound or connected in a conventional fashion.

The layers of cut-resistant fabric can be made from the cut-resistant fiber(s) by subjecting the cut-resistant fiber(s) to a fabric-forming process. Suitable fabric- forming processes including weaving and knitting. The cut-resistant fabric may also be in the form of a non-woven fabric. The fabric made from the cut-resistant fiber(s) will have improved cut-resistance in comparison with the same fabric made using fiber manufactured from the same polymer but without a filler. Generally, the cut- resistance will be improved by at least 10%) when measured using tests generally accepted in the industry for measuring cut resistance (the Ashland Cut Protection test), and preferably will be improved by at least 20%>, 35% or even 50%>.

To form the ballistic-resistant article of this invention, multiple layers of the fabric may be arranged in parallel arrays and/or incorporated into laminates or composites. Ballistic-resistant articles within the scope of this invention may also be formed by sewing a plurality of the fabric layers together. Ballistic-resistant garments within the scope of this invention can be prepared from the cut-resistant fabric layers in accordance with conventional methods for forming ballistic-resistant garments from layers of fabric or other materials. Suitable methods are disclosed, e.g., in U.S. Patent Nos. 5,479,659; 4,850,050; 5,443,883; 5,635,288; 5,547,536; and 5,443,882; each of the foregoing references being hereby incorporated by reference herein.

Particularly suitable methods for forming a ballistic-resistant garment, e.g., vest, within the scope of this invention are disclosed in the above-cited U.S. Patent No. 5,479,659 (Bachner, Jr.). For example, at least two layers of the cut-resistant fabric in woven form can be arranged in the form of panels as taught in U.S. Patent No. 5,479,659, followed by assembling at least two of such panels, stitching a plurality of stitches into both panels in the manner taught in the Bachner, Jr. patent, and then placing the panels in overlying relationship and adjacent to one another. A particularly preferred ballistic-resistant garment within the scope of the present invention is a protective vest. The vest may be in the form of any of the known ballistic-resistant vests. Non-limiting examples of suitable vests include those disclosed in U.S. Patent Nos. 5,479,659; 4,850,050; 5,443,883; 5,635,288; 5,547,536; and 5,443,882; each of which were previously incorporated by reference herein.

Particularly suitable ballistic-resistant vests within the scope of the present invention generally have the same shape and form as the Second Chance® SUPERfeatherlite® series of vests.

The ballistic-resistant articles of this invention can be used in both military and civilian applications.

For example, an early ballistic-resistant vest worn by ground troops was made from fabric in the form of a 2x2 basket weave prepared from 5 plies of 200 denier nylon, each having 34 filaments. Twelve plies of this fabric were preferably stitched or spot-bonded to make the vest, which has an areal density of 167 ounces per square yard weighing about 4 kg. Such vest has a ballistic limit of 373 meters/sec, i.e., the ability to stop a 1.1 gram missile with a velocity of 373 meters/sec.

High strength fibers such as aramid permit lighter weight, more flexible structures with higher ballistic limits. The U.S. Army personal armor system for ground troops (PASGT) specification utilizes 13 plies of Kevlar® 29, 0.4747 kg/m² (13.97 oz/sq.yd) each ply. A modern fabric construction for civilian use is represented by a plain weave of 36 x 36 ends of 400 denier aramid yarn weighing 3.6 oz sq.yd. A ballistic-resistant vest for civilian use can be made from such a fabric. The number of plies (i.e., layers) of the fabric in such civilian-type ballistic-resistant vest will depend on the degree of ballistic protection needed. To form the vest, the plies of fabric can be cross-laminated and stitched together as in a quilt or as described in U.S. Patent No. 5,479,659, which was previously incorporated by reference herein. The number of fabric layers in the ballistic-resistant articles of this invention is preferably that number which provides a desired balance between ballistic-resistance on the one hand and light weight, flexibility and mobility on the other hand. Such number of plies, which depends on the degree of ballistic protection needed, can be determined by routine experimentation. Generally, the articles of this invention can comprise at least 2 layers of fabric, preferably at least 10 layers of fabric, more preferably from about 20 to about 80 layers, and most preferably from about 20 to about 40 layers of fabric.

The present invention is also directed to a method of providing ballistic protection to a designated site. Such method broadly involves disposing the ballistic- resistant article relative to the designated site so as to provide such site with ballistic protection. Preferably, the ballistic-article is disposed so as to cover the designated site, such as, e.g., by wearing the article over such site.

Typically, the designated site is composed of one or more portions of the human body, particularly those portions containing vital organs such as the heart or the lungs. For example, an individual may provide ballistic protection to his or her heart and/or lungs by wearing a ballistic-resistant vest within the scope of the present invention such that the vest covers the chest and back of such individual.

As discussed previously herein, the presence of the hard filler particles in the polymer/filler blend used to form the cut-resistant fiber(s) from which the article of this invention is made increases the ballistic limit of such article by at least about 10% to 20%). In other words, the ballistic limit of the article of this invention is at least about 10%) to 20%) higher than that of an article which is identical to the article of this invention except that hard filler particles were not present in the fiber- forming polymer composition. The resistance of the article of this invention to penetration by knives or low velocity fragments will be similarly improved. Furthermore, while the ballistic-resistant textile articles of this invention are lighter weight constructions than prior art ballistic-resistant articles using ceramic or metal sheets, the textile articles of this invention provide the same or higher ballistic-resistance than such prior art articles.

EXPERIMENTAL Example 1 and Control Example A

Example 1 and Control Example A respectfully illustrate the ballistic resistance of a textile article made from a cut-resistant fiber in accordance with the present invention and the ballistic-resistance of a textile article made from a fiber conventionally used to form ballistic-resistant articles.

In Example 1, the article to be evaluated is made from a cut-resistant fiber in the form of a 400 denier 120 filament aramid yam filled with 6% aluminum oxide particles of 2 micron average particle size. In Control Example A, the article is made from a fiber in the form of a 400 denier 120 filament aramid yam which is unfilled. The filled yam in Example 1 and the unfilled yam in Control Example A are each subjected to a weaving process to form a woven fabric. Each fabric is a plain weave of 36 fibers per inch of the 400 denier yam for the warp by 36 ends per inch of the yam for the fill. Each fabric has an areal density of 3.6 ounces per square yard. In both Example 1 and Control Example A, the ballistic-article to be tested is in the form of a test pad of 12 inches square. Each test pad is made by stacking the fabric formed in the examples. A test pad containing 20 layers of the fabric has an areal density of 0.5 pound per square foot, and a test pad containing 40 layers of the fabric has an areal density of 1.0 pound per square foot. Two types of ballistic rounds are used to evaluate the ballistic-resistance of the test pads of Example 1 and Control Example A. The first type is a 9 mm 124 grain FMJ Remington from a 4-inch barrel which is an NIJ (National Institute of Justice) certified round for civilian Threat Level IIA. The second type of ballistic round is a 17 grain 22 caliber military round. Penetration of the test pads of Example 1 and Control Example A by the two types of rounds described above forms a basis for comparison of the ballistic- resistance of the different fibers used to form the test pads. The ballistic-resistance of each of the test pads of Example 1 and Control Example A was measured in terms of the test pad's ability to stop each of the rounds of ammunition described above. The 9 mm round will have a striking velocity of 332 meters/sec, and the military round will have a striking velocity of 397 meters/sec. The resistance to ballistic penetration of the filled-aramid test pad of Example 1 is at least 10%> higher than that of the unfilled-aramid test pad of Control Example A.

Example 2

There is a need for resistance to stabbing as well as ballistics resistance for protective clothing used in certain police and correctional applications. The protective clothing industry is using stab tests with a standard ice pick and sharp edge knife blade. Fabrics with tighter weaves show improved resistance to stabbing, and fabrics have been designed which are not penetrated by the ice pick, which bends rather than penetrating the fabric at high energy loading. These fabrics are high-count, at 71x71 yams per inch, and require lower denier feed yams of about 200 denier. These high- count fabrics provide higher resistance to stabbing with a sharp knife but further improvement is still needed.

Two 200/75 denier/fils aramid yams, produced using the same aramid polymer as described in the previous example, were evaluated. Yam #1 is an aramid control, having about 20 gpd tenacity. Yam #2 is a similar aramid yam containing 6% by weight hard aluminum oxide particles of average diameter of 2 microns and a disk like shape with aspect ratio of about 8. The cut resistance of 13 OSY fabrics of these respective yams as measured by ASTM F1790 is 850 g for yam #1 and 1700 g for yarn #2. To make stab resistant fabrics, the yams are woven in a flat weave at 71x71 yams/inch. The resulting fabrics have an areal density of about 3.65 OSY. Test panels are made by layering 12x12 inch squares of these stab resistant fabrics. Panels of 40 and 60 layers of fabric weigh about 1 and 1.5 lb, respectively. The panels are submitted for impact with a double-edge, sharp knife propelled by air cannon. The backing is ballistic gelatin. This test is a British standard and is known as the PSDB (Police Scientific Development Branch) standard. This test is believed by the industry to best represent the human stab condition. This is a pass/fail test with depth of penetration of greater than 5 mm the criterion for failure. The test is run in the US by H.P. White Laboratories and requires 4 shots on a test panel with each of two blades: a 3" #1 blade and a 6" #5 blade. The energy range for the 4 shots is 20-65 J. The particle filled yam #2 compared with the control #1 provides improved resistance to puncture from the knife by more than 10%>.

Claims

WHAT IS CLAIMED IS:

1. A ballistic-resistant textile article, comprising multiple layers of a cut- resistant fabric, wherein the cut-resistant fabric is formed from at least one cut- resistant fiber, the cut-resistant fiber being formed from a blend comprising (i) at least one fiber-forming polymer and (ii) an effective amount of at least one hard filler having a Mohs Hardness value of at least about 3.0.

2. An article according to Claim 1 , wherein the hard filler is uniformly distributed in the blend of the fiber-forming polymer and the hard filler.

3. An article according to Claim 1, wherein the hard filler is in the form of particles.

4. An article according to Claim 3, wherein the hard filler is in the form of platelet particles.

5. An article according to Claim 3, wherein the hard filler particles have an average diameter of from about 1 to about 5 microns.

6. An article according to Claim 5, wherein the hard filler particles have an average diameter of from about 1 to about 3 microns.

7. An article according to Claim 1 , wherein the hard filler has a Mohs Hardness value of at least about 4.0.

8. An article according to Claim 8, wherein the hard filler has a Mohs Hardness value of at least about 5.0.

9. An article according to Claim 1 , wherein the hard filler is selected from the group consisting of ceramic materials, metals, metal alloys and crystalline minerals.

10. An article according to Claim 1 , wherein the hard filler is selected from the group consisting of tungsten, copper, brass, bronze, aluminum, steel, iron, monel, cobalt, titanium, magnesium, silver, molybdenum, tin, zinc, aluminum oxide, tungsten carbide, metal nitrides, metal sulfides, metal silicates, metal suicides, metal sulfates, metal phosphates, metal borides. silicon dioxide, silicon carbide, baddeleyite. chloritoid, clinozoisite, chondrodite, euclasite, petalite, sapphire, spodumene, staurolite, clay, glass, and alumina.

11. An article according to Claim 1 , wherein the hard filler is calcined aluminum oxide.

12. An article according to Claim 1. wherein the fiber- forming polymer is melt-processable.

13. An article according to Claim 12, wherein the fiber-forming polymer is selected from the group consisting of amorphous polymers, semi-crystalline polymers, and liquid crystalline polymers.

14. An article according to Claim 13. wherein the fiber- forming polymer is selected from the group consisting of polyethylene terephthalate. polyethylene naphthalate, polyamide. aramid. high modulus polyethylene, polypropylene, and thermotropic liquid crystalline polymers.

15. An article according to Claim 14. wherein the fiber- forming polymer is poly(ethylene terephthalate).

16. An article according to Claim 14. wherein the fiber-forming polymer is an aramid polymer.

17. An article according to Claim 1. wherein the fiber-forming polymer is poly(ethylene terephthalate) and the hard filler is calcined aluminum oxide.

18. An article according to Claim 1, wherein the fiber- forming polymer is an aramid polymer and the hard filler is calcined aluminum oxide.

19. An article according to Claim 1. wherein the cut-resistant fiber comprises from about 80%) to about 99.99%) by volume of the fiber-forming polymer and from about 0.01% to about 20.0% by volume of the hard filler.

20. An article according to Claim 19, wherein the cut-resistant fiber comprises from about 97% to about 99.91% by volume of the fiber-forming polymer and from about 0.03%> to about 3.0%> by volume of the hard filler.

21. An article according to Claim 1 , wherein the cut-resistant fiber is a bicomponent fiber having a sheath/core structure.

22. An article according to Claim 21, wherein the sheath/core bicomponent fiber comprises a sheath component and a core component, wherein the sheath component comprises at least one unfilled fiber-forming polymer, and said core component comprises said blend of the at least one fiber-forming polymer and the hard filler.

23. An article according to Claim 22. wherein the fiber- forming polymer in the sheath component and the fiber-forming polymer in the core component are identical polymers.

24. An article according to Claim 22. wherein the fiber-forming polymer in the sheath component and the fiber-forming polymer in the core component are different polymers.

25. An article according to Claim 22, wherein said sheath/core bicomponent fiber comprises about 10% to about 60%) by weight of the sheath component and from about 40%> to about 90% by weight of the core component.

26. An article according to Claim 25. wherein said sheath/core bicomponent fiber comprises about 50%> by weight of the sheath component and about 50%) by weight of the core component.

27. An article according to Claim 25. wherein said core component comprises from about 80%> to about 98%> by weight of the fiber-forming polymer and from about 2% to about 20%> by weight of the hard filler.

28. An article according to Claim 27. wherein said core component comprises about 88%> by weight of the fiber-forming polymer and about 12%> by weight of the hard filler.

29. An article according to Claim 1. wherein the fabric is a knitted or woven fabric.

30. An article according to Claim 1, wherein the fabric is a non-woven fabric.

31. An article according to Claim 1. wherein the article comprises at least

2 layers of said cut-resistant fabric.

32. An article according to Claim 1. wherein the article comprises at least 10 layers of said cut-resistant fabric.

33. An article according to Claim 1. wherein the article comprises from about 20 to about 80 layers of said cut-resistant fabric.

34. An article according to Claim 1. wherein the article comprises from about 20 to about 40 layers of said cut-resistant fabric.

35. An article according to Claim 1 , wherein the article is selected from the group consisting of automobile door panels, aircraft padding, garments, helmets, briefcases, umbrellas and coverings.

36. An article according to Claim 35, wherein the article is a protective garment.

37. An article according to Claim 36, wherein the protective garment is a vest.

38. A method of providing ballistic-protection to a designated site, comprising disposing the ballistic-resistant textile article of Claim 1 relative to the designated site so as to provide such site with ballistic protection.

39. A method according to Claim 38, wherein the designated site comprises at least one portion of a human body.

40. A method according to Claim 39, wherein the designated site comprises the lungs and/or heart of said body.

41. A method according to Claim 40, wherein said ballistic-resistant article is a protective garment, and said method comprises placing said garment on said body so as to cover the heart and/or lungs of such body.

42. A method according to Claim 41 , wherein said garment is a vest.