MXPA05000589A - Cut and abrasion resistant fibrous structure. - Google Patents

Abstract

The invention relates to a fibrous structure comprising at least one non composite para-aramid strand and at least one nylon strand maintained in a parallel relationship to each other, the non composite para-aramid strand being present in the material in an amount ranging from about 20 % to 99.9 % by weight, relative to the weight of the structure. The invention also relates to a process to manufacture such structure and to high cut and abrasion resistant protective clothing made of this structure like gloves, aprons and sleeves.

Description

FIBROUS STRUCTURE RESISTANT TO CUTTING AND ABRASION FIELD OF THE INVENTION The present invention relates to a fibrous structure 5 resistant to high abrasion, comprising a specific construction of a non-composite para-aramid strand and a nylon strand. This structure can be used for the manufacture of protective clothing that has a high resistance to cutting and a high resistance to abrasion. BACKGROUND OF THE INVENTION Aramides and more specifically para-aramides, are a class of relatively new materials, which find application in the domain of mechanical and thermal protection. The high cut protection performance can be obtained from textile assemblies made from the para-aramid fibers. Therefore, para-aramid fibers are often used in the manufacture of protective clothing for workers or industrialists, firefighters, athletes, military and military officers. A drawback of para-aramid fibers is that they tend to experience a relatively low abrasion resistance due to their tendency to fibrillation. The 5 risk associated with this modest resistance to abrasion is REF. : 160183 the reduction of the operation to the cut of the protective clothes with the time under service. In this area of protection against wear and friction and therefore, low abrasion, the nylons are superior, but do not offer sufficient cutting performance. There is still a need to provide a material that has both high and durable cutting performance and a very high abrasion resistance. There are many factors that influence the abrasion resistance of a fabric. Abrasion performance can be adapted by selecting the type of fiber components, fiber properties, textile structures, fabric mass per unit area, number of fibers per unit volume or tolerance of relaxation of the fiber components within the fiber bundle. Often, the addition of abrasion-resistant materials in a given structure containing cut-resistant components generally provides superior performance to abrasion at the expense of cut resistance. U.S. Patent 5,319,950 discloses a reinforcement component which is a composite yarn made of a nylon twisted yarn helically wrapped by another nylon twisted yarn, this reinforcing component is knitted in a braided relationship with a yarn of the body. The manufacture of such yarn is complex and requires several steps, however, the reinforced fabric thus obtained is still not satisfactory with respect to the shear strength.

Now, it has been found that by combining the specific fiber ingredients in a specific construction style, it is possible to realize fibrous material resistant to high abrasion and very resistant to high cutting, quickly, directly and easily. In particular, it is possible to achieve the same level of cut resistance with a higher level of abrasion resistance than if the same fiber ingredients are either taken separately or combined in a different construction style. SUMMARY OF THE INVENTION One aspect of the invention is a fibrous structure comprising at least one strand of non-composite para-aramid and at least one nylon-based strand maintained in a parallel relation to each other, the strand of para Non-composite aramid is present in the structure in an amount ranging from about 20% to about 99.9% by weight, based on the weight of the structure. Another aspect of the invention is a process for manufacturing the above structure, comprising the step of processing a non-composite para-aramid strand and a nylon strand in a parallel relationship with each other. Another aspect, of the invention, is a process for providing a fibrous structure having abrasion and high cut resistance, comprising: - a) providing strands of at least one strand of non-composite para-aramid and at least one strand of nylon, - b) feeding the strands in a knitting machine or knitting machine without prior assembly, and - c) knitting or weaving a fibrous structure without changing the order in which the fibers are fed to the machine, the strands are maintained in a parallel relationship with each other during the knitting or full fabric process. A further aspect of the invention is a protective clothing resistant to abrasion and high cut, in particular, gloves, aprons or sleeves, made of the above fibrous structure. The fibrous structure of the invention has a high resistance to abrasion. It also has a very high cut resistance. With the structure of the invention, it is possible to manufacture protective clothing resistant to abrasion and high cut, such as work gloves. The gloves made of the fibrous structure of the invention are comfortable and, using them, the user does not lose the natural dexterity of their hands. The fibrous structure of the invention also finds use in the ballistics area: it has a very good puncture resistance. However, since the strand of. Para-aramid of the invention is a non-composite, the manufacturing process of the fibrous structure is very simple and direct, and does not require any prior treatment or arrangement of the strand. The manufacturing process can therefore be completed in a minimum number of stages, allowing a fast, easy and effective realization in cost of any fibrous structure. DETAILED DESCRIPTION OF THE INVENTION "Fibrous structure" as used herein, includes two or three dimensional structures comprising fibrous material. Preferably, this structure includes knitted fabrics, woven, unidirectional, non-woven fabrics, and / or combinations thereof. By "combinations", it means that structures of different nature and / or construction can be assembled together, either in the same plane or not, for example as a multi-layered structure, or by any means of assembly such as sewing, gluing , stitches and the like. By "nonwoven", it means fibrous materials combined to a bonding matrix of polyethylene, polypropylene, polyamides, phenols, epoxy resins, polyester or mixtures thereof. "Fibrous material", as used herein, includes continuous fibers, such as filaments, short fibrous structures, short-cut fibers, microfibers, multiple filaments, cords, yarns, fibers, pulps. The fibers can be processed into threads of short fibrous structures, which are spun into staple fibers, into continuous fiber threads or into cracked threads which can be described as intermediate threads between continuous and discontinuous threads. "Strand", as used herein, means an ordered assembly of fibrous material having a high length to diameter ratio, preferably having a length of at least 1000 times its diameter. The strand may be round, flat or may have another transverse shape, or it may be a hollow fiber. "Uncomposed strand" means a single single strand as opposed to strands assembled as co-twisted strands, co-textured strands, intermixed strands, spun strands with core and combinations thereof. The structure of the invention comprises at least one strand of non-composite para-aramid. Aramides are polymers that are partially, predominantly or exclusively, composed of aromatic rings, which are connected through carbamide bridges or optionally, also, through other bridging structures. The structure of such aramides can be elucidated by the following general formula of repeating units: (-NH-Al-H-CO-A2-CO) n wherein Al and A2 are the same or different and mean aromatic rings and / or polyaromatics and / or heteroaromatics, which can also be substituted. Typically, Al and A2 can independently be selected from 1,4-phenylene, 1,3-phenylene, 1,2-phenylene, 4,4'-biphenylene, 2,6-naphthylene, 1,5-naphthylene, 1 , 4-naphthylene, phenoxyphenyl-4,4'-5-diylene, phenoxyphenyl-3,4 '-diylene, 2,5-pyridylene and 2,6-quinolylene, which may or may not be substituted by one or more substituents. which may comprise halogen, C 1 -C 4 alkyl, phenyl, carboalkoxy, C 1 -C 4 alkoxy, acyloxy, nitro, dialkylamino, thioalkyl, carboxyl and 0-sulfonyl. The group -CO H- can also be replaced by a carbonyl hydrazide group (-CONH H-), azo group or azoxy group. These aramides are prepared in a general manner, by polymerization of diacid chloride, or the corresponding diacid, and diamine. Examples of aramides are poly-m-phenylene isophthalamide and poly-p-phenylene terephthalamide. Additional suitable aromatic polyamides are of the following structure: (-NH-Arl-X-Ar 2 -NH-CO-A 1-X-Ar 2 -CO-) n 0 in which X represents O, S, S02, NR, N2 , CR2, CO. · · '|-; . · R represents H, C1-C4 alkyl and AR1 and Ar2, which may be the same or different, are selected from 1,2-phenylene, 1,3-phenylene and 1,4-phenylene and in which at least , a hydrogen atom can be substituted with halogen and / or C 1 -C 4 alkyl.

Further, useful polyamides are disclosed in U.S. Patent No. 4,670,343, wherein the aramid is a copolyamide in which, preferably at least 80% by mass of the Al and total A2 are 1,4-phenylene and phenoxyphenyl-3, 4. '-diylene, which may or may not be substituted and the content of phenoxyphenyl-3,4'-diylene is 10% up to 40% per mole. Additives with aramid can be used and, indeed, it has been found that as much as 10% by weight of other polymeric materials can be mixed with the aramid, or such copolymers can be used having as much as 10% of another diamine substituted by the diamine of aramid or as much as 10% of another chloride diacid substituted by the chloride diacid of aramid. The non-composite para-aramid strands of the invention preferably have an elongation equal to or less than 5%, measured in accordance with ASTM D885-98. Preferably, the para-aramid strands have a modulus of from about 10 to about 2500 g / den, preferably from about 1000 to about 2500 g / den, and a toughness of from about 3 to about 50 g / den. , preferably from about 3 to about 38 g / den. Modules and tenacity are measured in accordance with ASTM method D 885-98. The structure of the invention may comprise several strands of para-aramides. In such a case, the strands are independent of each other. Para-aramid strands are present in the structure of the invention in an amount ranging from about 20 to about 99.9%, preferably, from about 30% to about 70% by weight, relative to the total weight of the structure. The strands are generally spun from an anisotropic spinning solution using an air vacuum spinning process as is well known and described in US Patent Nos. 3,767,756 or 4,340,559. The structure of the invention also comprises at least one nylon strand. For "nylon", an elaborate polymer polyamide aliphatic thread is suggested. Nylons suitable in the present invention include, polyhexamethylene adipamide (nylon 66.), polycaprolactam (nylon 6), polybutyrolactam (nylon 4), poly (9-aminononanoic acid) (nylon 9), polyenantolactam (nylon 7), polycaprylactam ( nylon 8) and polyhexamethylene sebacamide (nylon 6.10) The preferred nylon is polyhexamethylene adipamide (nylon 66) In a preferred embodiment of the invention, the | Nylon thread is. a textured thread. By "textured strand," it means a strand which has been subjected to a treatment, such as air injection, for example, to intermix the originally parallel strands that make up the strand.

Preferred nylon strands of the invention have an elongation equal to or less than 18%, and a tenacity equal to or less than 10 gpd. Elongation and tenacity are measured in accordance with ASTM D885-98. The nylon yarns are generally spun by extrusion of a polymer melt through a capillary in a gaseous frozen medium. Such processes are well known. Suitable nylon strands of the invention include, the product sold under the trademark "Cordura®" by E.I. du Pont de Nemours and Company, Delaware. The structure of the invention may comprise several nylon strands. The non-composite para-aramid strands and the nylon strands are maintained in a parallel relationship to one another in the structure of the invention. "Parallel", as used here, means that the angle between a strand along its entire path and any other strand along its entire path is around zero. All the strands remain independent and separated from each other. They do not mix intimately, they are not cotorcidas, they are not intermixed, neither commingled, nor interlaced, nor intermingled nor textured. They are not wrapped with any other, they do not form a fiber spun with a soul, nor a cover soul.

In a preferred embodiment of the fibrous structure of the invention, the non-composite para-aramid strand is present in an amount ranging from about 30% to about 70% by weight and the nylon-based strand is present in an amount ranging from about 30% to about 70% by weight, based on the weight of the structure. In addition to the non-composite para-aramid strands and the nylon-based strands described above, the structure of the invention may comprise additional natural or man-made strands. These additional strands include polyethylene strands, polyester strands, acrylic strands, acetate strands, meta-aramid strands, glass strands, steel strands, ceramic strands, polytetrafluoroethylene strands, cellulosic strands, cotton strands, strands of silk, wool strands and mixtures thereof. These additional strands may be present in an amount of about 0.25 wt.% To about 25 wt.%, Based on the total weight of the structure, as long as their presence in the structure of the invention does not negatively impact the strength of the structure. cutting and high abrasion specific to the structure of the invention. These additional strands are also maintained in a parallel relationship to any other strand present in the structure.

The structure of the invention shows a very good cut resistance. In a preferred embodiment of the invention, the structure of the invention shows a combined normal IFCP C.N.C. index, measured as described below, equal to or greater than 80 g / mm, more preferably, equal to or greater than 90 g / mm. The structure of the invention also shows a very good resistance to abrasion. In a preferred embodiment of the invention, the structure exhibits an abrasion resistance, measured in accordance with the method EN 388, equal to or greater than 1000 cycles, more preferably equal to or greater than 3000 cycles. In a more preferred embodiment of the invention, the structure exhibits both a combined standard IFCPRC.N Index, measured as described below, equal to or greater than 90 as an abrasion resistance, measured in accordance with EN 388, equal or greater than 1000 cycles. The structure of the invention preferably shows an average weight ranging from 200 g / m2 to around 1500 g / m2, preferably ranging from around 300 g / m2 to around 800 g / m2, measured in accordance with the method EN 388. The structure of the invention is prepared in accordance with any classical textile process, allowing the parallel alignment of the strands by making the structure: knitted, woven, placed unidirectionally, combining the strands with a bonding matrix to form a nonwoven. For example, in the process of knitting or weaving, the strands are fed directly into the knitting machine or the knitting machine without any prior assembly of any kind. For example, in the knitting process, the order in which the strands are fed into the needles of the knitting machine remains the same during the complete knitting process. The preferred process for making the structure of the invention is the knitting process. The structure of the invention can be used in the manufacture of gloves, aprons, sleeves and any protective clothing that requires a high cut resistance and a high resistance to abrasion. The invention will be explained in more detail with reference to the following examples. Test Methods and Description of Examples Abrasion Resistance In the following examples, the abrasion resistance of the samples was measured in accordance with the European Standard Method EM388, July 1994, section entitled "Protective Gloves Against Mechanical Hazards", subsection 6"Resistance to Abrasion". The device was the Martindale abrasion and use tester, designed to give a controlled amount of abrasion between the surface of the fabric and abrasive selected at relatively low contact pressure of (9 +/- 0.2) kPa in continuously changing directions. The circular samples were weathered against a standard abrasive glass fiber paper (grade 117 grade 117 sand grit). The abrasion was continued and the samples were examined at suitable intervals without removing them from their support. The rubbing situation was characterized by breaking yarns and the average values of the cycle to reach this break were recorded and averaged for the 6 samples. The test was conducted at (23 +/- 2) ° C and (50 +/- 5)% relative humidity. The greater the number of cycles necessary to reach the break, the higher the abrasion resistance of the sample. Cutting resistance In the following examples, the cut resistance was measured in accordance with the "Standard Test Method for Measuring the Cut Resistance of Materials Used in Protective Clothing", ASTM Standard F 1790-97. In the execution of the test, a cutting edge, under a specified force, was approached once through a sample mounted on a cylindrical mandrel. ? several different forces, the distance approached from the initial contact through the cut was recorded and a force graph was constructed as a function of the distance through the cut. From the graph, the forces (in grams) were determined through cutting at a distance of 25.4 millimeters and 10 millimeters, and were normalized to validate the consistency of the blades. These normalized forces are respectively referred to later as NL1 (for the distance of 25.4 mm) and NL2 (for the distance 10 mm). The blades were stainless steel cutting blades with a sharp edge of 70 mm, which were calibrated using a 4 N load on a neoprene sheet of about (1.57 +/- 10%) mm and a Shore A hardness of ( 50 +/- 5). This was done at the beginning and end of the test. A new blade was used for each measurement, that is, on each load. The sample was a rectangular piece of 50x100 mm textile placed at an inclination of 45 degrees. The mandrel was a rounded electroconductive rod with a radius of 38 millimeters and the sample was mounted on top using double-sided tapes. The cutting edge was approached through the textile in the mandrel at right angles to the longitudinal axis of the mandrel. The • was registered; cut when the cutting edge made electrical contact with the mandrel. The normalized forces were reported as the shear strengths, respectively NL1 and NL2 expressed in grams for a cut length of 25.4 mm and 10 mm.

The test was conducted at (23 +/- 2) ° C and (50 +/- 5)% relative humidity. The cut of 25.4 millimeters can be classified as a cut similar to the tear and the cut of 10 millimeters can be classified as a cut similar to perforation. These two belong to different regions of the cut length - shear force ratio, which is a non-linear curve. It was therefore convenient to define a combined index, which has merit to the composite of the two behaviors. This index is hereinafter referred to as the Combined Drilling and Tearing Court Operation Index, IFCPRC. It was computed by the following equation: IFCPRC = This index was further normalized by a constant weight of the fabric composition, subsequently selected at 800 grams per square meter. This mass per square area is a realistic value with respect to protective clothing applications, such as gloves for use. industrial.

IFCPRC, This combined normalized index is given in grams per millimeters of cutting length. The higher this index is, the higher the cut resistance of the sample. For each sample, 12 samples were tested. The result is the average of the results of the 12 tests. Ingredients Strand A of non-composite para-aramid: the discontinuous linear para-aramid yarn of 714 dtex, equivalent Nm = 28/2 (with dtex = 10000 / Nm) is commercially available from E.I. du Pont de Nemours and Company under the trademark Kevlar® discontinuous aramid fiber, Type 970. Discontinuous synthetic fibers were produced from short para-aramid fibers 38 mm in length as per the state of the art spinning process used for the production of discontinuous para-aramid yarns. The short fibers of para-aramids were obtained by cutting para-aramid strands of continuous filaments made of 1000 filaments of 1.5 dpf (1.6 dtex) each. Strand B of nylon: Discontinuous nylon yarns 66 of linear density of 370 dtex, equivalent Nm = 55/2 (with dtex = 10000 / Nm), are commercially available from E.I. du Pont de Nemours and Company under the trade designation Cordura® Type 200. Discontinuous synthetic fibers were produced from short polyamide 66 nylon fibers of 38 mm length as per the state of the art spinning processes used for the production of discontinuous threads of aliphatic polyamide. The short fibers of aliphatic polyamide were obtained by cutting elaborate filaments of continuous filament yarns of 1.9 dtex each. EXAMPLES Examples 1 and 2 are comparative examples. Example 3 is an example according to the invention. For the results to be comparative, all three experiments were performed by a relatively constant value of the total dtex (which is representative of the linear density of a fiber), and a relatively constant value of the mass per surface area. Example 1 (Comparative) Five strands A, of independent non-composite para-aramid, were fed to a circular knitting machine (Lawson-Hamphill Fiber Analysis Weaver) without prior assembly of any kind. A sleeve of sufficient length was knitted to obtain a uniform and reproducible pattern of a mass per surface area close to 800 g / m2. The samples were cut to the dimensions and shapes - adequate, circular for the abrasion and rectangular tests for the measurement of the cutting operation, to carry out 6 abrasion tests and 12 cutting tests. Each of the samples has therefore a total dtex of 3570 (five times of 714 dtex).

The abrasion resistance measured was 900 cycles. The forces measured in the cut resistance test were 821 g for a cutting length of 25.4 mm and 1666 g for a cutting distance of 10 mm. The combined IFCPRC.N index 5 was given by the following calculation [(821 / 25.4 + 1666/10) / 2x800 / 800 and equaled to 99 g / mm. Step 2 (Comparative) Ten strands B were fed, of independent nylon to the same circular knitting machine as used in Example 1 without prior assembly of any kind. A sleeve of sufficient length was knitted to obtain a uniform and reproducible pattern of a mass per surface area close to 843 g / m2. The samples were cut to the dimensions and 5 suitable forms, circular for the abrasion test and rectangular for the measurement of the operation to the cut, to carry out 6 abrasion tests and 12 cutting tests. Each of the samples has, therefore, a total dtex of 3700 (ten times of 370 dtex). 0 The abrasion resistance measured was 3000 cycles.

| · '- "The forces measured in the cut resistance test were 759 g for a cut length of 25.4 mm and 923 g for a cut distance of 10 mm The combined normalized index IFCPRC.N was given by the next 5 calculation [(759 / 25.4 + 923/10) / 2] x800 / 826 and equal to 59 g / mm.

The index IFCPRC.N of Example 2, revealed a lower cut resistance 40%, compared to Example 1. On the other hand, the abrasion resistance of Example 2 is three times higher than that of Example 1. Example 3 (Invention ) Three strands A, of independent non-composite para-aramid and four independent nylon strands B, were fed to the same circular knitting machine as used in Example 1 without prior assembly of any kind. A sleeve of sufficient length was knitted to obtain a uniform and reproducible pattern of a mass per surface area close to 843 g / m2. The samples were cut to the appropriate dimensions and shapes, circular for the abrasion test and rectangular for the measurement of the cutting operation, to perform 6 abrasion tests and 12 cutting tests. Each sample therefore has a total dtex of 3622 (three times of 714 dtex plus four times of 370 dtex). Each sample comprises 50.1% by weight of non-composite para-aramid strand, relative to the weight of the sample, and 40.1% by weight of nylon strand, relative to the weight of the sample. The resistance to abrasion was 6000 cycles. The forces measured in the cut resistance test were 1170 g for a cutting length of 25.4 m and 1400 g for a cutting distance of 10 rtim. The combined IFCPRC.N normalized index is given by the following calculation [(1170 / 25.4 + 1400/10) / 2] X800 / 843 and equals 88 g / mm. The IFCPRC.N index of Example 3 revealed approximately equal shear strength, compared to Example 1. On the other hand, the abrasion resistance of Example 3 is six times higher than that of Example 1, and surprisingly two times greater than that of Example 2. The following table summarizes the results obtained in Examples 1 to 6. TABLE I It is noted that in relation to this date, the best method known to the applicant to practice said invention is that which is clear from the present description of the invention.

Claims (12)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. Fibrous structure, characterized in that it comprises at least one strand of non-composite para-aramid and at least one nylon-based strand maintained in a parallel relationship to each other, the non-composite para-aramid strand is present in the structure in an amount ranging from about 20% to 99.9% by weight, based on the weight of the structure.
2. 2. Structure according to claim 1, characterized in that the non-composite para-aramid strand is present in an amount ranging from about 30% to about 70% by weight, and the nylon strand is present in an amount which varies from about 30% to about 70% by weight, based on the weight of the structure.
3. 3. Structure according to claim 1, characterized in that the nylon strand is a textured strand.
4. Process for manufacturing the fibrous structure according to claim 1, characterized in that it comprises the step of processing the non-composite para-aramid strand and a nylon strand in a parallel relationship with each other.
5. 5. Process according to claim 4, characterized in that the processing includes knitting, weaving, placing unidirectionally or combining the strands with a linking matrix to form a non-woven.
6. 6. Process according to claim 5, characterized in that the processing is knitted.
7. 7. Protective clothing resistant to abrasion and high cut, characterized in that it is made of the fibrous structure according to claim 1.
8. 8. Gloves resistant to abrasion and high cut, characterized in that they are made of the fibrous structure in accordance with claim 1.
9. 9. High-abrasion and abrasion-resistant sleeves, characterized in that they are made of the fibrous structure according to claim 1.
10. 10. Abrasion-resistant and high-cut apron, characterized in that it is made of the fibrous structure of according to claim 1.
11. 11. Process for providing a fibrous structure having abrasion resistance and high shear, characterized in that it comprises: a) providing strands of at least one strand of non-composite para-aramid and at least one strand nylon, b) feed the threads on a knitting machine or knitting machine without prior assembly, c) knit or weave a fibrous structure if n change the order in which the strands are fed into the machine, the strands are maintained in a parallel relationship with each other during the knitting or full fabric process. Structure according to claim 1, characterized in that it shows a combined standard IFCPRC index equal to or greater than 80 g / mm and an abrasion resistance, measured in accordance with EN 388, equal to or greater than 1000 cycles.