MX2008007113A - Multiaxial fabric with strain-responsive viscous liquid polymers - Google Patents

Abstract

The invention concerns multiaxial fabrics comprising a first layer comprising a plurality of first yarns being substantially parallel in a first direction, a second layer comprising a plurality of second yarns being substantially parallel in a second direction and skew or off-set with respect to the first yarns, transverse yarn interlaced transversely within the layers;wherein each layer is coated with a high viscosity polymer that has a Tg in the range of about -40 to about 0°C, and a zero shear viscosity of about 2x106to about 1013poise at 20°C.

Description

MULTIAXIAL FABRIC WITH VISCOUS LIQUID POLYMERS THAT WORK IN RESPONSE TO THE VOLTAGE FIELD OF THE INVENTION The present invention relates to a multi-axial fabric useful in ballistic applications. BACKGROUND OF THE INVENTION Shielding against personal ballistic bodies, particularly vests, helmets, and other articles, is generally formed of materials that serve to prevent the penetration of a bullet or other projectile, and any other object that is forcefully applied to shields, such as a knife. These items are used mainly for the armed forces, but they also have police and civil applications. There is a growing demand to improve the wearability and total effectiveness of the armor systems used by soldiers and police officers in combat environments. The thickness and total weight of the shielding systems can affect the wear resistance, but the reduction of these parameters in the currently known systems can compromise the effectiveness of the shielding against penetration. Known fabrics for ballistic applications include those having at least two layers having unidirectional fibers such that the fibers in the second layer are slid to the fibers in the first layer. See, for example, U.S. patent applications. Nos. 2002/0164911, 2003/0228815, and 2005/0081571. Similar constructions have been impregnated with an agglutination material. See U.S. patent application. No. 2004/0045428 and the U.S. patent. No. 6,238,768. The U.S. patent No. 5,160,776 discloses a composite material having at least one layer which is a network of certain high strength filaments in a matrix material. The U.S. patent No. 4,183,993 discloses the use of laminated materials in a unidirectional reinforcing fabric that includes a knitting yarn per weft formed from a multiplicity of knit stitches per knit and a multiplicity of longitudinally extending warp inserts, parallel , retained in the knitting by weft. The U.S. patent No. 5,935,678 discloses a ballistic laminated structure in the form of a sheet including first and second arrays of fiber bundles oriented unidirectionally. The second array of fiber bundles is folded transversely at an angle with respect to the first array of fiber bundles. In this construction, a polymeric film lies between the first and second transversely folded arrays of fiber bundles to adhere the first and second arrays of the fiber bundles together without substantial penetration of the film into the fiber bundles. The U.S. patent No. 5,677,029 describes a ballistic article having at least one fibrous layer and at least one polymeric layer which is in contact with and which is attached to all or a portion of the fibrous layer. Certain fabrics containing both woven and nonwoven layers are also known. See, U.S. patent application No. 2004/0132368. There is a need for fabrics and ballistic articles with improved performance. BRIEF DESCRIPTION OF THE INVENTION Multiaxial tissues comprising; a first layer comprising a plurality of first yarns that are substantially parallel in a first direction, a second layer comprising a plurality of second yarns that are substantially parallel in a second direction and slid or decentered with respect to the first yarns, a yarn transverse cross-linked within the layers to hold the layers together; wherein each layer is coated with a high viscosity polymer having a Tg in the range of about -40 to about 0 aC, and a zero shear viscosity of about 2xl06 to about 1013 poises at 20 SC. Articles and garments comprising such fabrics and a method of manufacturing such fabrics are also provided. The prior general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as defined in the appended claims. BRIEF DESCRIPTION OF THE FIGURES The modalities are illustrated in the figures that are attached to improve the understanding of the concepts as presented here. Figure 1 includes an illustration of the use of multiple unidirectional layers and cross fibers in the construction of a multi-axial fabric. Skilled artisans will appreciate that the objects in the figure are illustrated for reasons of simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some objects in the figure can be exaggerated in relation to the other objects to help improve the understanding of the modalities. DETAILED DESCRIPTION OF THE INVENTION In some embodiments, the invention relates to a multi-axial fabric comprising; a first layer comprising a plurality of first yarns that are substantially parallel in a first direction, a second layer comprising a plurality of second yarns that are substantially parallel in a second direction and slid or decentered with respect to the first yarns, a yarn transverse cross-linked within the layers to hold the layers together; wherein each layer is coated with a high viscosity polymer having a Tg in the range of about -40 to about 0 2C, and a zero shear viscosity of about 2xl06 to about 1013 poises at 20 aC. In some embodiments, at least a plurality of yarns comprise an aramid fiber. In certain embodiments, at least a plurality of threads comprise a polybispyridazole fiber. A preferred polybispyridazole is poly [2,6-diimidazo [4,5-b: 4,5-e] -pyridinylene-1,4 [2,5-dihydroxy] phenylene. Suitable high viscosity polymers include one or more of a cyanoacrylate adhesive, a urethane adhesive, an epoxy aliphatic amine resin, an epoxy aromatic amine resin, a poly (vinyl propionate), a poly (methacrylate) hexyl) a poly (isopropyl acrylate), and an ethylene / methyl acrylate copolymer.

In some embodiments, the transverse yarn comprises a fiber of polyester, polyethylene, polyamide, aramid, polyarenoazoles, polypyridazoles, or polypyridobisimidazole. In certain embodiments, the fabric further comprises a third layer of threads comprising a plurality of third threads that are substantially parallel in a third direction and that slide or are off-center with respect to the first threads and the second threads. In some embodiments, the fabric further comprises a fourth layer of threads comprising a plurality of fourth threads that are substantially parallel in a fourth direction and that slide or are off-center with respect to the first, second and third threads. Articles and garments comprising a fabric described herein are also provided. The invention also relates to a method of producing a fabric comprising: contacting a first layer comprising a plurality of first yarns that are substantially parallel in a first direction with a second layer, the second layer comprises a plurality of seconds threads that are substantially parallel in a second direction and slid or de-centered with respect to the first threads; and transversely interlacing the threads with the layers to form a multi-axial fabric; wherein each layer is coated with a high viscosity polymer having a Tg in the range of about -40 to about 0 SC, - and a zero shear viscosity of about 2xl06 to about 1013 poises at 20C. The present invention can be more easily understood by reference to the following detailed description of the illustrative and preferred embodiments forming a part of this description. It is to be understood that the scope of the claims is not limited to the specific devices, methods, conditions or parameters described and / or shown herein, and that the terminology used herein is for the purpose of describing particular modalities by way of example only and it is not proposed to be limitative of the claimed invention. Also, when used in the specification including the appended claims, the circular forms "a", "an", and "the" include the plural, and reference to a particular numerical value includes at least this particular value, unless that the context clearly dictates otherwise. When a range of values is expressed, another mode includes from a particular value and / or to another particular value. Similarly, when the values are expressed as an approximation, by the use of the "approximately" antecedent, it will be understood that the particular value forms another modality. All intervals are inclusive and can be combined. When used here, the term "off center" simply means that it is not directly above the top. The term "slipped" when referring to two pluralities of threads means that the pluralities lie at different angles in a related manner. Any angles that provide acceptable performance can be used. An expert in the art is capable of determining the optimum slip for a particular construction. For example, with two layers, the pluralities may be at 0 degrees and 90 degrees. Other examples are 0 degrees / 45 degrees / 90 degrees and 0 degrees / 45 degrees / 90 degrees / 45 degrees. The invention relates to multiaxial fabrics comprising a first layer comprising a plurality of first yarns that are substantially parallel in a first direction, and a second layer comprising a plurality of second yarns that are substantially parallel in a second direction and that are slipped with respect to the first threads. The fabrics use the yarn interlaced transversely within the layers. The layers can be arranged in any consecutive order and can optionally be coated with a high viscosity polymer having a Tg in the range of about -40 to about 0 2C., a molecular weight of about 20,000 to 100,000, and a viscosity of about 2x106 up to about 1013 poises at 20 aC. Some additional layers may also be included in the invention. Such layers include a third layer of yarns comprising a plurality of third threads that are substantially parallel in a third direction and that slide with respect to the first yarns and the second yarns. Other layers include a fourth layer of yarns comprising a plurality of fourth yarns that are substantially parallel in a fourth direction and slid with respect to the first, second and third yarns. Examples of fibers suitable for use in the layers include those made of a polymer such as a polyolefin (eg, polyethylene or polypropylene), polyimide, polyester, poly (vinyl alcohol) polybenzezoles, such as polybenzimidazole (PBI), polyaramide , such as poly (paraphenylene terephthalamide) sold by EI du Pont de Nemours and Company (DuPont) Wilmington, DE under the trade name KEVLAR® and polypyridazoles, such as the polypyridobisimidazole available from Magellan Systems International, Richmond VA under the tradename M5®. The tenacity of a fiber must be at least about 900 MPa according to ASTM D-885 to provide superior resistance to ballistic penetration. Preferably, a fiber also has a modulus of at least about 10 GPa. When the polymer is polyamide, aramid is preferred. By "aramid" is meant a polyamide in which at least 85% of the amide bonds (-CO-NH-) are fixed directly to two aromatic rings. Suitable aramid fibers are described in Man-Made Fibers-Science and Technology, Volume 2, the section entitled Aromatic Fiber-forming Polyamides, page 297, W. Black et al., Interscience Publishers, 1968. Aramid fibers are also described in the US patents Nos. 4,172,938; 3,869,429; 3,819,587; 3,673,143; 3,354,127; and 3,094,511. Additives with aramid can be used and it has been found that as much as up to 10 percent by weight of other polymeric material can be combined with the aramid or that the copolymers can be used having at most 10 percent of another diamine substituted for the aramid diamine or at most 10 percent of another diacid chloride substituted by the diacid chloride or aramid. The preferred aramid is a para-aramid and the poly (p-phenylene terephthalamide) (PPD-T) is the preferred para-aramid. By PPD-T is meant the homopolymer resulting from the polymerization of approximately mol per mole of the p-phenylene diamine and terephthaloyl chloride, and also the copolymers resulting from the incorporation of small amounts of other diamines with the p-phenylene. diamine and of small amounts of other diacid chlorides with terephthaloyl chloride. As a general rule, other diamides and other diacid chlorides can be used in amounts of at most about 10 mole percent of p-phenylene diamine or terephthaloyl chloride, or perhaps slightly higher, provided only the other diamines and Diacid chlorides do not have reactive groups that interfere with the polymerization reaction. PPD-T also means copolymers resulting from the incorporation of other aromatic diamides and other aromatic diacid chlorides such as, for example, 2,6-naphthaloyl chloride or chloro- or dichloroterephthaloyl chloride or 3,4'-ether -diaminodiphenyl. When the polymer is the polyolefin, polyethylene or polypropylene are preferred. By polyethylene is meant a predominantly linear polyethylene material preferably of more than one million molecular weight which may contain minor amounts of chain branching or comonomers not exceeding 5 modifying units per 100 carbon atoms of the main chain, and which also may contain in admixture 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 antioxidants, lubricants, ultraviolet light filtering agents, colorants and the like which are commonly incorporated. One such polymer is commonly known as an extended chain polyethylene (ECPE). Similarly, polypropylene is preferably a predominantly linear polypropylene material of more than one million molecular weight. High molecular weight linear polyolefin fibers are commercially available. The preparation of polyolefin fibers is described in U.S. Pat. No. 4,457,985. Polyarenoazole polymers, such as polybenzoles and polypyridazoles, can be made by reacting a mixture of dry ingredients with a solution of phosphoric acid (PPA). The dry ingredients can comprise azole-forming monomers and metal powders. The heavy batches of these dry ingredients can be obtained by using at least some of the preferred embodiments of the present invention. Exemplary azole-forming monomers include 2,5-dimercapto-p-phenylene diamine, terephthalic acid, bis- (4-benzoic acid), oxy-bis- (4-benzoic acid), 2,5-dihydroxyterephthalic acid, isophthalic acid , 2,5-pyridodicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,6-quinolindicarboxylic acid, 2,6-bis (4-carboxyphenyl) pyridobisimidazole, 2,3,5,6-tetraminopyridine, 4,6-diaminoresorcinol, 2,5-diaminohydroquinone, 1,4-diamino-2,5-dithiobenzene, or any combination thereof. Preferably, the azole-forming monomers include 2, 3, 5, 6-tetraaminopyridine and 2,5-dihydroxyterephthalic acid. In certain embodiments, it is preferred that the azole-forming monomers be phosphorylated. Preferably, the phosphorylated azole-forming monomers are polymerized in the presence of polyphosphoric acid and a metal catalyst. The metal powders can be used to help build the molecular weight of the final polymer. Metal powders typically include iron powder, tin powder, vanadium powder, chromium powder, and any combination thereof. The azole-forming monomers and the metal powders are mixed and then the mixture is reacted with polyphosphoric acid to form a polymer solution of polyarenoazole. Additional polyphosphoric acid can be added to the polymer solution if desired. The polymer solution is typically extruded or spun through a die or spinneret to prepare or spin the filament. Polybenzoxazole (PBO) and polybenzothiazole (PBZ) are two suitable polybenzazole polymers. These polymers are described in PCT Application No. WO 93/20400. Polybenzoxazole and polybenzothiazole are preferably composed of repeating units of the following structures: Although the aromatic groups shown attached to the nitrogen atoms may be heterocyclic, they are preferably carbocyclic; and although they may be fused or unfused polycyclic systems, they are preferably single rings of six elements. Although the group shown in the main chain of the bis-azoles is the preferred para-phenylene group, this group can be replaced by any divalent organic group that does not interfere with the preparation of the polymer, or no group in total. For example, this group may be aliphatic of up to twelve carbon atoms, toluene, biphenylene, bis-phenylene ether, and the like. The polybenzoxazole and the polybenzothiazole used to make fibers of this invention must have at least 25 and preferably at least 100 repeating units. The preparation of the polymers and the spinning of these polymers are described in the PCT patent application No. WO 93/20400 mentioned above. The fibers made of the poly (pyridazole) polymers are suitable for use in the present invention. These polymers include poly (pyrimidazole), poly (pyridothiazole), poly (pyridoxazole), poly (pyridobisimidazole), poly (pyridobisthiazole), and poly (pyridobisoxazole). Poly (pyridobisimidazole) is a rigid bar polymer that is high strength. The poly (pyridobisimidazole) fiber can have an inherent viscosity of at least 20 dl / g or at least 25 dl / g or at least 28 dl / g. Such fibers include PIPD fiber (also known as M5® fiber and fiber made of poly [2,6-diimidazo [4,5-b: 4,5] -pyridinylene-1,4 [2, 5] -dihydroxy] phenylene The PIDP fiber is based on the structure: The poly (pyridobisimidazole) fiber can be distinguished from the commercially available, well-known PBI fiber or from the poly (benzimidazole) fiber because this poly (bibenzimidazole) fiber is a poly (bibenzimidazole). The poly (bibenzimidazole) fiber is not a rigid bar polymer and has a low strength fiber and a low stress modulus when compared to the poly (pyridobisimidazoles). PIPD fibers have been reported to have the potential to have an average modulus of approximately 310 GPa (2100 grams / denier) and average tenacities of up to approximately 5.8 GPa (39.6 grams / denier). These fibers have been described by Brew et al., Composers Sci ence and Technolgy 1999, 59, 1109; Van der Jagt and Beukers, Polymer, 1999, 40, 1035; Sikkema, Polymer 1998, 39, 5981; Klop and Lammers, Polymer, 1998, 39, 5987; Hageman, et al., Polymer 1999, 40, 1313. The fabrics, articles, garments, and the like may have additional layers or may have the tissues described herein adjacent to other tissues or sheets. High-performance fiber structures can take many forms such as a knitted fabric, a woven fabric, single-fabric structures, unidirectional sheets, multi-directional sheets (those, for example, that have fibers that cross over an angle between approximately 20 and 90 degrees), a non-woven layer (for example, felt), or even as single fibers. The fiber structure may take the form of more than 10, 20, 40, or 60 layers of the individual fiber structures of this invention. Some layers can be treated with a polymer. The treated layers can be placed in the back, away from the point of impact, or they can be placed in the middle part, or in any other way to optimize the functioning in the armor for the body. The concentration of the polymer can be the same for each of the treated layers, or it can vary from layer to layer to provide a desired variation of the stiffness through the packaging. The treated layers can be used in a package consisting of the types of fabric structures that can vary from layer to layer. The protective shield for the body is a main application of this invention. The high performance fiber structure can be manufactured in a body armor by a manufacturing process of a vest, standard, such as by stitching. Body armor is built by manufacturers to meet penetration resistance, closed trauma, and other requirements as established by the National Institute of Justice through NIJ 100-98. According to NIJ 100-98, the manner in which the ballistic panels are assembled into a single unit differs from one manufacturer to another. In some cases, the multiple layers are knitted in a deviated manner around the full edge of the panel; in others, the layers are adhered by knitting together in several locations. Some manufacturers assemble fabrics with a number of vertical or horizontal knit rows; some can still cushion the complete ballistic panel. There is no evidence that knitting alters the ballistic resistant properties of a panel. Instead, knitting tends to improve overall performance, especially in cases of closed trauma, depending on the type of tissue used. In some embodiments of this invention, one or more, high viscosity polymeric adhesives with low glass transition temperatures are coated on or impregnated in a fiber structure. The high viscosity polymer adhesive can be referred to variably as a polymer or an adhesive. Also, when the impregnated term is used, it should be understood that it is also proposed to encompass a coating. The excellent ballistic resistance is preserved while the resistance to a closed trauma is improved. The deformation of the posterior face (BFD) is an indicator of closed trauma, that is, the lower the BFD, the less trauma a person using a protective device could be sustained. A liquid adhesive impregnated in one. Fiber structure at low levels is believed to act. essentially as a friction improver by modifying the sliding friction of the filaments in the fabric under the conditions of ballistic impact. In addition, such materials provide a reduction in the deformation of the back face, while the ballistic resistance to penetration in an article such as a body shield is retained or slightly improved. The BFD is expressed in millimeters (mm). In some embodiments, the present invention is also an article comprising one or more layers of a high performance fiber structure impregnated (or coated) with about 1 to 15 weight percent of a high viscosity adhesive with a Tg between about -40 SC and 0 BC. Vitreous transition temperatures were measured using differential scanning calorimetry (DSC) at heating rates of 10 2C / minute. The central point of the transition was chosen as Tg. The Tg is expressed in SC from beginning to end of this specification. In general, liquid adhesives are preferred compared to solid adhesives. The matrices of solid adhesives can lead to a reduced ballistic penetration resistance, because they make the other additives more rigid and as well as systems that are too rigid or too high in friction due to the presence of about 15% by weight or more of the adhesive additive. As described below, such behavior is expected for very high friction and stiffness in impregnated fabrics as when multiple layers are impacted by high velocity projectiles. With respect to the response of tissues with adhesives of a low Tg during the impact, it is important to consider the dependence of the tension rate of these systems. One way to understand this experiment is to apply frequency-dependent dynamic mechanical methods. For the test, the inert glass support fabrics are impregnated with either poly (vinyl propionate) (PVP) or with poly (hexyl methacrylate) (PHM). The PHM is deposited out of the solution with toluene and the toluene is removed. These samples are used in dynamic mechanical analysis dependent on frequency (DMA). The experiments and the equipment are standard and are described in "Use of a Dynamical Mechanical Analyzer to Study Supported Polymers" Starweather, H. Giri, M., R., J. Appl. Polym. Soc. 1982, 27, 1243. The vitreous transitions dependent on the frequency are resolved as a maximum in the lost signal. Taking the extremes of the frequency, at 0.1 Hz and 30 Hz the Tg in PHM varies from -18.5 SC to -2 BC, respectively. Over the same frequency range, the Tg for PVP varies from 3 SC to 12.5 BC. This corresponds to the activation energies of 40 kcal / mol and 65 kcal / mol for PHM and PVP, respectively. Very high deformation rates of ballistic events contribute to a high equivalent frequency of deformation (>; > 105 Hz). This high deformation rate easily converts PVP and PHM from the liquid phase to the vitreous solid phase. For example, at 105 Hz, the Tg based on this activation energy for PHM could be shifted to 25 2C. This value shows that even PHM is well inside the vitreous phase at room temperature under the high deformation rates induced by the ballistic impact.

The Tg of the high viscosity adhesive used in this invention falls in the range of about -40 to about 0 aC and preferably in the range of about -35 to about -10 SC. For these materials, the high deformation rates of the ballistic event are sufficient to displace this Tg dependent on the frequency above the ambient temperature, converting the viscous adhesives into rigid vitreous solids. Because of the low Tg and the "fluid" nature, these adhesives provide the flexible fabrics for making protective vests that are comfortable under static conditions. If the vitreous transition is below -40 ° C, the deformation rates are not high enough to convert the system into a vitreous phase. As noted above, in some preferred embodiments, the adhesives must be polymeric fluids of high viscosity. They should not be elastic solids, polymers of very high molecular weight, semicrystalline elastic solids, or cross-linked elastic solids. Polymers, such as these, can reduce the resistance to penetration and will be stiffer, resulting in a reduction in comfort. In addition, solid adhesives applied at low levels, especially, will not be self-regenerating and will lose effectiveness once the fabric is substantially deformed. These high viscosity adhesives impart moderate to relatively high friction. For high viscosity adhesives having a Tg in the range of about -40 ° C to about 0 ° C, the high friction on a dry tissue control sample correlates well with BFD and contributes to an operating advantage. The viscosity of the impregnated additive also correlates with the rigidity of the fabric. In addition to the Tg, the adhesives used in this invention can also be characterized by their molecular weight (Mw) and viscosity. The molecular weights are averages by weight and are typically determined by gel permeation chromatography. The molecular weight of the viscous fluid polymer can be, for example, in the range of about 20,000 to 400,000 g / mol (20,000 to 100,000 in some embodiments). The viscosity range desired for the viscous fluid polymers is from about 2 × 10 6 to about 1013 poises. The viscosity is typically measured at room temperature, but in general, the viscosities of the subject adhesives as provided herein are too high at room temperature to be measured by standard techniques. In this case, the viscosity is estimated by extrapolation from the viscosity of the molten material at high temperature, the characterization of the flow index of the molten material or other qualitative rheological characterization. A typical method applied for the characterization of the zero shear viscosity of polymeric fluids is cone and plate rheometry or capillary viscosimetry. A low viscosity outside the above range will typically reduce performance, such as in the case of siloxane fluids with a low Tg, even those with high Mws. These materials reduce the friction due to lubrication. This has been correlated with poor ballistic performance as described by Briscoe, B. J., Motamedi, F. "The ballistic impact characteristics of aramid fabrics: the influence of interface friction", Wear 1992 158 (1-2), 229). Liquid adhesives with appropriate properties can be formed in many ways including those such as suspension, emulsion or melt polymerization and in the form of a mixture or a copolymer. Examples of the polymers useful as high viscosity adhesives herein include poly (vinyl propionate) poly (hexyl methacrylate), poly (isopropyl acrylate), and a copolymer ethylene / methyl acrylate (wherein the ethylene content is 38 weight percent and the methyl acrylate content is 62 weight percent). The high viscosity adhesives with different flow properties and modulus of the solid elastomers were impregnated in ballistic fabrics. A desirably high level of both resistance to ballistic penetration and deformation of the back face (a measure of closed trauma) was found in the range of from about 1 to about 15% by weight of the level of the additive in the polyaramide fabric depending of how many layers were treated. It is believed that this type of system could provide approximately 20-30% savings in weight compared to the density of the area needed to provide satisfactory protection against closed trauma in the vests knitted currently in use. The high viscosity adhesives as used in this invention have a glass transition temperature Tg which makes it possible for them to provide the desirable liquid adhesive performance in this invention., and that control the deformation of the back face through the effects of viscosity and friction in a fiber structure. For the purposes herein, the term "fiber" is defined as a microscopically homogeneous, relatively flexible body having a high ratio of length to width across its cross-sectional area perpendicular to its length. The cross section of the fiber may be of any shape, but is typically round. Here, the term "filament" or "continuous filament" is used interchangeably with the term "fiber". When used herein, the term "staple fibers" refers to fibers that are cut to a desired length or to fibers that are naturally present with or which naturally have a low length to width ratio. of its cross-sectional area perpendicular to its length when compared to the filaments. The length can vary from 0.254 cm (0.1 inch) to several feet. In some embodiments, the length is from 0.254 cm (0.1 inches) to approximately 20.32 cm (8 inches). The man-made staple fibers are cut to a length suitable for processing into the spinning equipment of a cotton, woolen, or yarn thread. The staple fibers may have: (a) a substantially uniform length, (b) a variable or random length, or (c) subsets of the staple fibers that have a substantially uniform length and the staple fibers in the other subsets have different lengths, with the staple fibers in the mixed sub-assemblies which together form a substantially uniform distribution. In some embodiments, suitable staple fibers have a length of 1 to 30 centimeters. The staple fibers made by short shear processes lead to a fiber length of 1 to 6 centimeters. The staple fibers can be made by any process. The staple fibers can be formed by stretching to the rupture of the continuous fibers leading to staple fibers with deformed sections that act as curls or hooks. The staple fibers can be cut from the continuous straight fibers using a rotary cutter or a guillotine cutter leading to staple fibers (ie, without curls), or additionally cut from the continuous fibers with curls, which have a curl shaped sawtooth along the length of the cut fiber, with a curl frequency (or repeating bending) no greater than 8 curls per centimeter. The staple fibers obtained by stretch-to-tear can be made by breaking a bundle or bundle of continuous filaments during a stretching operation until the rupture has one or more rupture zones that are at a prescribed distance creating a mass random variable of fibers that have an average cut length controlled by the adjustment of the rupture zone. The staple fibers of this invention can be converted into yarns using traditional short and long staple fiber ring spinning processes which are well known in the art. For the spinning of a short staple fiber cotton system, fiber lengths from 1.9 to 5.7 cm (3/4 inches to 2-1 / 4 inches) are typically used. For spinning in a yarn or wool system, of long staple fibers, fibers up to 16.5 cm (ie 6-1 / 2 inches) are typically used, however, this is not intended to be limiting of the ring spinning because the yarns can also be spun using spinning with an air jet, the spinning of open ends, and many other types of spinning that convert the staple fibers into usable yarns. The staple fibers obtained by stretch-to-tear typically have a length of up to 17.8 cm (ie, 7 inches) and can be 15 made using the processes that use the fibers cut from the bottom to the top, obtained by stretching until the break, traditional. The staple fibers having maximum lengths of up to about 51 cm (i.e., 20 inches) are possible through the processes as described for example in PCT patent application No. WO 0077283. The threads are thus made by means of of consolidated fibers in a woven yarn using the entanglement of the filaments with air jets, having a tenacity in the range of 3 to 7 grams per decitex. These yarns may have a secondary twist, that is, they may be twisted after forming to impart greater tenacity to the yarn, in which case the tenacity may be in the range of 10 to 18 grams per denier (i.e. 17 grams per dtex). The staple fibers obtained by the stretch until the break usually do not require ripple because the process imparts a degree of curling in the fiber. The term "continuous filament" refers to a flexible fiber having a relatively small diameter and whose length is longer than that indicated for the staple fibers. The continuous filament fibers can be converted to multifilament yarns by processes well known to those skilled in the art. The fabrics of this invention can take novel configurations, including, but not limited to, knitted or knitted fabrics, or non-woven structures. Such tissue configurations are well known to those skilled in the art. By "non-woven fabric" is meant a network of fibers, including unidirectional (if contained within a matrix resin), felt, fiber batts, and the like. By "woven fabric" is meant a woven fabric fabric that uses any fabric woven fabric, such as taffeta, Turkish satin, Panama, satin fabric, twill fabric, and the like. Taffeta or twill fabrics are thought to be the most common fabrics used in the market. The invention is exemplified by the following examples which are not proposed to limit the scope of the invention. EXAMPLES COMPARATIVE EXAMPLE 1 In comparative example 1, the multiaxial fabric layers are made from a continuous filament yarn of poly (terephthalamide p-phenylene) of a high tenacity of 930 dtex with a linear density of 1.66 dtex per filament , available from EI DuPont de Nemours and Company under the trademark Kevlar® 129. Each layer of fabric is constructed with four sets of parallel threads in 18 ends per inch arranged at different angles and joined together by a set of polyethylene threads that form a low denier loop with low tenacity. The density of the area of each multiaxial tissue layer is approximately 0.27 kg / m2. The tensile strength of the four sets of yarns used in the multiaxial fabric is 24.3 grams / dtex, and the density of the fiber is 1.44 grams / cm3. The stability of the multiaxial tissue layer is poor. The threads in the multiaxial tissue layer can be distorted and pushed to the side by the penetration of a pointed object. Seventeen layers of the multi-axial fabric of approximately 38.1 x 38.1 cm (15"x 15") in size are knitted together around the edge and with a cross stitch to form a composite structure with a total area density of about 4.6 kg / m2. The assembly is then tested against a 357 mag gun bullet by the NIJ ballistic standard 0101.04 for level II for deformation of the rear face and ballistic V50. The results, especially the deformation of the back face of the composite structure, is poor due to the low structural stability of the layers of the fabric. Example 1 In example 1 of this invention, multiaxial fabric layers are made of a high tenacity poly (terephthalamide p-phenylene terephthalamide) filament yarn with a linear density of 1.66 dtex per filament, available from EI DuPont de Neumors and Company under the brand Registered Kevlar® 129. Each layer of fabric is constructed with four sets of threads parallel to 18 ends per inch arranged at different angles and joined together by a set of polyethylene threads that form a low density loop and low denier. The density of the area of each multiaxial tissue layer is approximately 0.27 kg / m2. The tensile strength of the four sets of yarns used in the multiaxial fabric is 24.3 grams / dtex, and the density of the fiber is 1.44 grams / cm3. The multiaxial tissue layer is additionally coated with about 5% by weight of a high viscosity polymer having a Tg in the range of -40 ° C to about 10 ° C with a zero shear melt viscosity of 2x 106 to about 1013 poises at 20 aC, and a molecular weight of approximately 20,000 to 100,000. The density of the area of each coated multiaxial fabric layer is approximately 0.284 kg / m2. The structural stability of the multiaxial tissue layer of this invention is very good. Sixteen layers of the coated multiaxial fabric of this invention with a size of approximately 38.1 x 38.1 cm (15"x 15") are knitted together around the edge and with a cross stitch to form a composite structure with a density of the total area of approximately 4.5 kg / m2. The assembly is then tested against a 357 mag pistol bullet of NIJ standard 0101.04 for level II for deformation of the rear face and ballistic V50. The results, especially the deformation of the back face of the composite structure of the example is below 44 mm and is much better than that of the art described in comparative example 1. It will be appreciated that certain characteristics are described here, for reasons of clarity, in the context of separate modalities, can also be provided in combination in a single modality. On the contrary, several characteristics that are, for reasons of brevity, described in the context of a single modality, can also be provided separately or in any sub-combination. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (18)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A multi-axial fabric, characterized in that it comprises: a first layer comprising a plurality of first yarns that are substantially parallel in a first direction, a second layer comprising a plurality of second yarns which are substantially parallel in a second direction and which are slid or offset with respect to the first yarns, a transverse yarn interlaced transversely within the layers to hold the layers together; wherein each layer is co with a high viscosity polymer having a Tg in the range of about -40 to about 0 aC, and a zero shear viscosity of about 2xl06 to about 1013 poises at 20 ° C; the high viscosity polymer comprises one or more of a cyanoacryladhesive, a urethane adhesive, an epoxy aliphatic amine resin, an epoxy aromatic amine resin, a poly (vinyl propion, a poly (hexyl methacryl, a poly (isopropyl acryl, and an ethylene / methyl acrylcopolymer. The fabric according to claim 1, characterized in that at least a plurality of yarns comprise an aramid fiber. 3. The fabric according to claim 1, characterized in that at least a plurality of threads comprise a polybispyridazole fiber. The tissue according to claim 3, characterized in that the polybispiridazole is poly [2,6-diimidazo [4,5-b: 4,5-e] -pyridinylene-1,4 [2,5-dihydroxy] phenylene). The fabric according to claim 1, characterized in that the transverse yarn comprises a fiber of polyester, polyethylene, polyamide, aramid, polyarenoazoles, polypyridazoles, or polypyridobisimidazole. The fabric according to claim 1, characterized in that it also comprises a third layer of threads comprising a plurality of third threads that are substantially parallel in a third direction and that are slid or off-center with respect to the first threads and the second threads. threads. The fabric according to claim 6, characterized in that at least a plurality of yarns comprise an aramid fiber. The fabric according to claim 6, characterized in that at least a plurality of yarns comprises the polybispyridazole fiber. The tissue according to claim 8, characterized in that the polybispyridazole is poly [2,6-diimidazo [4,5-b: 4,5-e] -pyridinylene-1,4 [2,5-dihydroxy] phenylene). The fabric according to claim 6, characterized in that the high viscosity polymer is one or more of a cyanoacryladhesive, a urethane adhesive, an epoxy aliphatic amine resin, an epoxy aromatic amine resin, a poly ( vinyl propion, a poly (hexyl methacryl, a poly (isopropyl acryl, and an ethylene / methyl acrylcopolymer. The fabric according to claim 6, characterized in that it also comprises a fourth layer of threads comprising a plurality of fourth threads that are substantially parallel in a fourth direction and that are slid or off-center with respect to the first, second and third threads. threads. 12. The fabric in accordance with the claim 11, characterized in that at least a plurality of yarns comprise an aramid fiber. 13. The fabric in accordance with the claim 11, characterized in that at least a plurality of threads comprise the polybispyridazole fiber. 14. The tissue according to claim 13, characterized in that the polybispiridazole is poly [2,6-diimidazo [4,5-b: 4,5-e] -pyridinylene-1,4 [2,5-dihydroxy] phenylene. 15. The fabric in accordance with the claim 11, characterized in that the high viscosity polymer is one or more of a cyanoacryladhesive, urethane adhesive, aliphatic amine epoxy resin, an epoxy aromatic amine resin, a poly (vinyl propionate), a poly (hexyl methacrylate), a poly (isopropyl acrylate), and an ethylene / acrylate copolymer of methyl. 16. A garment, characterized in that it comprises the fabric according to claim 1. 17. An article, characterized in that it comprises the fabric according to claim 1. 18. A method of producing a fabric, characterized in that it comprises: contacting a first layer comprising a plurality of first yarns that are substantially parallel in a first direction with a second layer, the second layer comprises a plurality of second yarns that are substantially parallel in a second direction and slid or decentered with respect to the first threads; and transversely interlacing the yarn with the layers to form a multi-axial fabric; wherein each layer is coated with a high viscosity polymer having a Tg in the range of about -40 to about 0 2C, - and a zero shear viscosity of about 2xl06 to about 1013 poises at 20 ° C.