Yarns and fabrics having fire resistance, cut resistance, and elastic recovery properties, and processes for producing them.

Abstract

A ply yarn, and fabrics and articles comprising the ply yarn, the ply yarn comprising: (a) at least one first yarn comprising at least 50 weight percent heat resistant polymeric fibers, wherein at least 30 weight percent of the polymeric fibers present in said yarn are cut resistant heat resistant polymeric fibers having a cut resistance of 500 grams force or greater according to ASTM F2992-15; (b) at least one second yarn having a sheath / core structure with a sheath of halogenated self-extinguishing staple fibers and a core comprising at least one continuous elastomeric filament; (b) 60 to 95 weight percent of the halogenated self-extinguishing fibers are in contact with elastomeric filaments, and the halogenated self-extinguishing fibers are free or substantially free of inorganic fibers, and fabrics and articles comprising the ply yarn.

Description

Technical Field

[0001] 1. Field of the Invention. The present invention relates to threads and fabrics suitable for use in articles of protective clothing having fire resistance, shape conformity, and cut resistance.

Background Art

[0002] Description of Related Art. Twisted threads and fabrics having cut resistance and elastic recovery, processes for making them, and their use in articles of protective clothing are disclosed in U.S. Patent No. 6,952,915.

[0003] Threads containing modacrylic fibers, p-aramid fibers, and m-aramid fibers, which are useful in making fabrics having arc protection and flame protection properties, are disclosed, for example, in U.S. Patent No. 7,065,950 and U.S. Patent No. 7,348,059. These threads may further include, as optional components, 2 to 15 weight percent of a wear-resistant fiber such as nylon and / or 1 to 5 weight percent of an antistatic component.

[0004] Threads and fabrics having a combination of fire resistance and elastic recovery are described, for example, in U.S. Patent No. 5,069,957, U.S. Patent No. 5,527,597, and U.S. Patent No. 5,694,981. These existing solutions utilize threads made by covering an elastic core thread with an outer coating of substantially protective fibers made from fire-resistant fibers. In other words, these references describe protecting the elastic core by using another fiber in the same thread to structurally shield the elastic core from the flame.

[0005] As used herein, the terms “structural shielding” and “structural shielding” mean that the covering fibers readily carbonize when exposed to flame and remain in place in the yarn covering any elastic filaments within the core, thus providing a structural barrier between the flame and the elastic core. As taught in these patents, these yarns are provided with an outer covering of substantial protective fibers made of fire-resistant fibers that physically protect the elastic core yarn from degradation or melting when exposed to extreme temperatures and fire.

[0006] Unfortunately, in many cases, the fibers that provide a suitable structurally shielding outer fibrous covering tend to be stiffer fibers, and therefore, fabrics made from such yarns may not be as comfortable as desired. This ultimately results in protective clothing that may not be as comfortable as desired, and it is well known that when protective clothing is not comfortable enough, workers tend not to wear it, putting themselves at risk.

[0007] In addition, any solution to protect the elastic core must meet current protective clothing standards. Specifically, the new NFPA 2112-2018, "Standard on Flame-Resistant Clothing for Protection of Industrial Personnel Against Short-Duration Thermal Exposures from Fire," provides specifications for minimum design, performance, testing, and certification requirements, as well as test methods for flame-resistant clothing, shrouds, hoods, balaclavas, and gloves for use in areas where there is a risk of short-term thermal exposure from fire. This standard requires that the afterflame time of the fabric used in the clothing be 2 seconds or less. Afterflame time is the time the test specimen continues to burn after the burner has been removed from the flame, up to 0.2 seconds in seconds.

[0008] This standard imposes even stricter requirements for flame-resistant gloves, stating that the amount of material consumed in a flame resistance test must not exceed 5.0 percent of the original weight of the test specimen. In other words, after applying a flame to the test specimen for a specified 12 seconds, following the standard's procedure, the weight loss of the fabric must be 5.0 percent or less. [Overview of the project] [Problems that the invention aims to solve]

[0009] Therefore, what is needed is a yarn and / or fabric that possesses a combination of cut resistance, fire resistance, and elastic recovery, specifically incorporating an elastic core yarn, meeting the NFPA 2112-2018 standard, and further utilizing fibers with a textile feel to provide more comfortable protective clothing. [Means for solving the problem]

[0010] The present invention relates to a flame-resistant, cut-resistant fabric, and a multi-ply yarn suitable for use in fabrics and articles containing the same, wherein the multi-ply yarn is (a) at least one first yarn comprising at least 50 weight percent of heat-resistant polymer fibers, wherein at least 30 weight percent of the polymer fibers present in at least one first yarn are cut-resistant heat-resistant polymer fibers having a cut resistance of 500 gram force or more according to ASTM F2992-15, (b) comprising at least one second yarn having a sheath / core structure comprising a sheath of halogenated self-extinguishing short fibers and a core containing at least one continuous elastomer filament, In this case, 60–95 weight percent of at least one second yarn is halogenated self-extinguishing fiber, the halogenated self-extinguishing fiber is in contact with at least one continuous elastomer filament, and the second yarn is free of or substantially free of inorganic fibers. [Modes for carrying out the invention]

[0011] The present invention relates to yarns and fabrics suitable for use in protective clothing articles, which possess both fire resistance and shape conformability, and further provide cut protection. This unique combination is achieved by combining elastic materials, self-extinguishing fibers, and strong heat-resistant polymer fibers to limit the consumption of the fabric during combustion and to provide high fire resistance in the yarn or fabric.

[0012] Specifically, the present invention relates to a multi-ply yarn suitable for use in flame-retardant and cut-resistant fabrics, and this multi-ply yarn is (a) at least one first yarn comprising at least 50 weight percent of heat-resistant polymer fibers, wherein at least 30 weight percent of the polymer fibers present in at least one first yarn are cut-resistant heat-resistant polymer fibers having a cut resistance of 500 gram force or more according to ASTM F2992-15, (b) comprising at least one second yarn having a sheath / core structure comprising a sheath of halogenated self-extinguishing short fibers and a core containing at least one continuous elastomer filament, In this case, 60–95 weight percent of at least one second yarn is halogenated self-extinguishing fiber, the halogenated self-extinguishing fiber is in contact with at least one continuous elastomer filament, and the second yarn is free of or substantially free of inorganic fibers.

[0013] When tested according to NFPA-2112-2018, this yarn can produce fabrics with a maximum afterburn time of 2 seconds or less and a weight loss of 5 weight percent or less.

[0014] "Flame-resistant and cut-resistant fabric" means a knitted or woven fabric that is both "flame-resistant" and "cut-resistant." The description of "flame-resistant" in relation to a fabric means that, when tested according to ASTM 6143-15, the carbonization length of the fabric is 4 inches (100 mm) or less. "Cut-resistant fabric" means that the fabric has at least a minimum level of cut resistance, and generally has a cut resistance of at least 200 gram-force according to ASTM F2992-15. In some preferred embodiments, the fibers and yarns described herein can provide a flame-resistant and cut-resistant fabric having a cut resistance of at least 500 gram-force according to ASTM F2992-15. However, in some other embodiments, it is understood that other fibers or yarns can be incorporated into the fabric that can provide other desirable qualities to the fabric, as long as the flame performance requirements described herein are met and the fabric maintains a minimum cut resistance of at least 200 gram force in accordance with ASTM F2992-15, although it is not necessarily required to provide cut resistance.

[0015] Flame-retardant fabrics provide thermal protection from thermal events, while cut-resistant fabrics provide mechanical protection from objects such as knives and sharp blades. In addition, it is often important or desirable that any articles made from such fabrics, such as protective gloves, be comfortable, have a good fit, and possess dexterity. "Good fit and dexterity" means, for example, that the gloves conform well to the shape of the wearer's hand, allowing them to grasp and manipulate small objects while wearing them. The flame-retardant and cut-resistant fabrics that can be provided by the yarns described herein are highly flame-retardant and cut-resistant, and also provide articles that are soft, flexible, and conform to shape. Protective clothing made from such fabrics is very comfortable and effective against multiple threats.

[0016] A flame-retardant, cut-resistant fabric is made from at least a first yarn providing heat-resistant polymer fibers and at least a second yarn providing at least one continuous elastomer filament covered with halogenated self-extinguishing fibers in contact with at least one continuous elastomer filament. The fabric is then made using at least the first yarn and at least the second yarn.

[0017] At least a first yarn and at least a second yarn are twisted together to form a multi-ply yarn. In some embodiments, the multi-ply yarn consists of only one first yarn and only one second yarn. In other embodiments, the multi-ply yarn consists of only one first yarn and multiple second yarns, and in other embodiments, the multi-ply yarn consists of multiple first yarns and only one second yarn. Similarly, in some embodiments, the multi-ply yarn consists of multiple first yarns and multiple second yarns. Finally, in some embodiments, the multi-ply yarn includes at least one first yarn and at least one second yarn, and other yarns made from any number of fibers may be included in the multi-ply yarn, as long as the final fabric meets the performance criteria discussed herein.

[0018] At least one first yarn contains at least 50 weight percent of heat-resistant polymer fibers based on the total weight of the first yarn, and at least 30 weight percent of the polymer fibers present in at least one first yarn are cut-resistant heat-resistant polymer fibers having a cut resistance of 500 gram force or more according to F2992-15, and at least one first yarn further has a sheath / core structure comprising a sheath containing cut-resistant heat-resistant polymer fibers and a core containing inorganic fibers. The reason for using the sheath / core structure is that the sheath short fibers provide covering and shield the inorganic filaments in the core from direct abrasion contact with the skin, thereby improving the comfort of the fabric containing the sheath / core yarn.

[0019] "Heat-resistant polymer fiber" refers to a fiber made from a synthetic organic polymer that retains 90 percent of its original fiber weight when heated to 500°C at a rate of 20°C per minute in air. Preferred heat-resistant polymer fibers have a yarn toughness of at least 3 grams per denier (2.7 grams per decitex). Heat-resistant polymer fibers include para-aramid fibers, aramid copolymer fibers, polybenzazole fibers, polybenzimidazole fibers, polyimide fibers, and mixtures thereof. Preferred heat-resistant polymer fibers are para-aramid fibers, and preferred para-aramid fibers are poly(paraphenylene terephthalamide) fibers.

[0020] At least one first yarn contains at least 50 weight percent of heat-resistant polymer fibers based on the total weight of the first yarn. In some embodiments, at least one first yarn contains at least 60 weight percent of heat-resistant polymer fibers based on the total weight of the first yarn. In some embodiments, at least one first yarn contains 60 to 85 weight percent of heat-resistant polymer fibers based on the total weight of the first yarn, and in some other embodiments, at least one first yarn contains 60 to 80 weight percent of heat-resistant polymer fibers based on the total weight of the first yarn.

[0021] At least 30 weight percent of the polymer fibers present in at least one first yarn are heat-resistant polymer fibers with a cut resistance of 500 gram force or more according to F2992-15. The cutting performance of the fibers is determined by measuring the cutting performance of a 345 g / m² (10 ounces / m² yard) fabric woven or knitted from 100% of the fibers under test, and the cut resistance (in gram force units) is then measured according to ASTM F2992-15.

[0022] According to F2992-15, cut-resistant heat-resistant polymer fibers having a cut resistance of 500 grams or more include para-aramid fibers, aramid copolymer fibers, polybenzazole fibers, polybenzimidazole fibers, and mixtures thereof. Preferred cut-resistant heat-resistant polymer fibers are para-aramid fibers, and preferred para-aramid fibers are poly(paraphenylene terephthalamide) fibers. When the heat-resistant polymer fibers have sufficient cut resistance, the cut-resistant heat-resistant polymer fibers in at least one first yarn can be the same as or different from the heat-resistant polymer fibers in at least one first yarn.

[0023] Therefore, it is understood that the cut-resistant heat-resistant polymer fibers are both the heat-resistant polymer fibers defined above and the cut-resistant fibers defined above. It is also understood that at least one first yarn can include fibers that are heat-resistant polymer fibers as defined herein but not cut-resistant fibers as defined herein. Table 1 provides an indicative standard showing selected exemplary compositions with respect to the possible percentages of total heat-resistant (CH-HR) polymer fibers and total inorganic filaments in at least one first yarn, and further provides the possible percentages showing the possible amounts of non-cut-resistant heat-resistant (non-CR-HR) polymer fibers and cut-resistant heat-resistant (CH-HR) polymer fibers.

[0024]

Table 1

[0026] In some preferred embodiments, in addition to heat-resistant and cut-resistant heat-resistant fibers, at least one first yarn may further include flame-resistant fibers. “Flame-resistant fiber” means that a fabric made solely from that fiber, according to the ASTM D6143-99 vertical burning test, has a carbonization length of 4 inches or less and an afterflame time of 2 seconds or less, but the fiber does not meet the cut resistance criteria set forth herein for cut-resistant heat-resistant polymer fibers. Suitable flame-resistant fibers include meta-aramid fibers, with a preferred meta-aramid being poly(metaphenylene isophthalamide). Potentially useful flame-resistant fibers include meta-aramid, polyamide-imide, flame-retardant treated (FR) cellulose, FR cotton, FR lyocell, or mixtures thereof. In some embodiments, at least one first yarn preferably has as much as 10 to 35 weight percent flame-resistant fibers, based on the total weight of polymer fibers in the first yarn.

[0027] Both the heat-resistant polymer fiber and the cut-resistant heat-resistant polymer fiber in at least one first yarn are short fibers having a length of preferably about 2 to 20 centimeters, preferably about 3.5 to 6 centimeters. Both the heat-resistant polymer fiber and the cut-resistant heat-resistant polymer fiber in at least one first yarn are short fibers having a diameter of preferably 5 to 25 micrometers and a linear density of 0.5 to 7 decitex. In some embodiments, if present, fibers or filaments that are flame-resistant or not heat-resistant polymer fibers are short fibers having dimensions similar to the above ranges of the heat-resistant polymer fiber and the cut-resistant heat-resistant polymer fiber.

[0028] In some embodiments, inorganic fibers are present in an amount of 15–40 weight percent of the total weight of the first yarn. Similarly, the maximum amount of heat-resistant polymer fibers in the first yarn of these sheath-core yarns is 85 weight percent based on the total weight of the first yarn. In some preferred embodiments, the sheath / core yarn has 60–80 weight percent of heat-resistant polymer fibers in the sheath and 20–40 weight percent of inorganic fibers in the core. Preferably, the inorganic fibers in the core are steel or tungsten. Preferably, the inorganic fibers in the core exist as one or more continuous filaments.

[0029] Sheath fibers can be wound around or spun around an inorganic filament core. Specifically, this can be achieved by known means, including conventional ring spinning, which includes improvements to conventional processes such as those utilizing COTSON technology, core-spun spinning such as DREF spinning, air-jet spinning using so-called core insertion by Murata (now Muratec) jet spinning, and open-end spinning. Preferably, short fibers are packed around the inorganic filament core at a density sufficient to cover the core. The coverage rate varies depending on the process used to spin the yarn, and core-spun spinning such as DREF spinning (disclosed in U.S. Patent Nos. 4,107,909, 4,249,368, and 4,327,545, for example) provides better coverage than ring spinning. Conventional ring spinning provides only partial coverage of the central core, but even partial coverage can provide adequate sheath / core coverage. Furthermore, the sheath may contain some fibers of other materials, to the extent that the reduction in cut resistance due to the other materials is acceptable.

[0030] Incorporating at least one inorganic filament as the core of a first yarn can be achieved, for example, in its simplest practical application, by passing rovings, slivers, or aggregates of heat-resistant and cut-resistant fibers, and optionally non-heat-resistant fibers, through a set of draft rolls to draft the fiber mass, which is then ring-twisted into a single yarn. At least one inorganic filament is typically fed from a bobbin through a set of feed rolls, and then fed into the short fibers before the final set of draft rollers. Since the inorganic core filament is not an elastomer, it does not need to be subjected to excessive tension during insertion into the yarn, and only sufficient tension is applied to either the sheath fiber or the core, as is conventionally done.

[0031] At least one first thread in the form of a sheath / core thread generally contains 15 to 50 weight percent inorganic filaments having a total linear sheath / core thread density of 100 to 5000 decitex. The core containing inorganic fibers may be a single filament or a multifilament, and may preferably be a single metal filament or several metal filaments, as required or desired in a particular application or degree of cut protection. Metal filament means a filament or wire made from a ductile metal such as stainless steel, copper, aluminum, bronze, tungsten, or a metal fiber structure commonly known as "micro-steel". Stainless steel is a preferred metal. Metal filaments are generally continuous wires. Useful metal filaments have a diameter of 1 to 150 micrometers, preferably 25 to 75 micrometers.

[0032] In some embodiments, the inorganic fiber is a glass filament. The inorganic fiber may be one or more glass filaments, such as a 110 decitex (100 denier) glass filament. However, glass is less preferable than metal because it has lower cut resistance per unit linear density, and when the yarn is used in gloves, sleeves, etc., where the fabric comes into contact with the skin, it is far more important that the glass is substantially covered with a sheath of short fibers to minimize skin irritation. Therefore, in many embodiments, the inorganic fiber is a metal filament rather than a glass filament.

[0033] At least one second yarn has a sheath / core structure comprising a sheath of halogenated self-extinguishing short fibers and a core containing at least one continuous elastomer filament, wherein 60–95 percent by weight of at least one second yarn is halogenated self-extinguishing short fibers, based on the total weight of the second yarn, the halogenated self-extinguishing fibers are in contact with at least one continuous elastomer filament, and the second yarn is free of or substantially free of inorganic fibers.

[0034] At least one second filament has a sheath / core structure, where the sheath of the halogenated self-extinguishing short fiber is in contact with and covering the core of at least one continuous elastomer filament. The halogenated self-extinguishing short fiber is thought to provide an active flame-extinguishing coating to the core of at least one continuous elastomer filament. This is different from a coating fiber that provides a "structural shielding" of the core, i.e., a coating fiber that readily carbonizes and remains in place when exposed to flame, and thus provides a structural barrier between the flame and the elastic core. Instead, the sheath of the halogenated self-extinguishing short fiber decomposes in the presence of a high heat flux such as a flame, releasing halogen gas that displaces local oxygen from the filament and prevents combustion of the core of at least one continuous elastomer filament. Therefore, it is thought that the halogenated self-extinguishing short fiber not only covers the core but is also in direct contact with the core and needs to locally displace oxygen from the surface of the core of at least one continuous elastomer filament.

[0035] A sheath of halogenated self-extinguishing staple fibers can be wound or spun around at least one continuous elastomer filament. This can be achieved by known means, including conventional ring spinning, including improvements to conventional processes such as core-spun spinning such as COTSON technology and DREF spinning, air-jet spinning using so-called core insertion by Murata (now Muratec) jet spinning, and open-end spinning. Preferably, the staple fibers are compacted around a core of at least one continuous elastomer filament with sufficient density to cover the core. The coverage rate varies depending on the process used to spin the yarn, and core-spun spinning such as DREF spinning (disclosed in U.S. Patents No. 4,107,909, 4,249,368, and 4,327,545, for example) provides better coverage than ring spinning. Conventional ring spinning provides only partial coverage of the central core, but even partial coverage is assumed herein to be a possible sheath / core structure.

[0036] The flame-extinguishing effect of halogenated self-extinguishing short fibers is considered appropriate when, based on the total weight of the second yarn, at least 60–95 weight percent of one second yarn is halogenated self-extinguishing fiber. In some embodiments, it is desirable that, based on the total weight of the second yarn, at least 80–95 weight percent of one second yarn is halogenated self-extinguishing fiber. The sheath may also include some fibers of other materials, to the extent that the reduction in flame-extinguishing effect due to the other materials is acceptable.

[0037] Halogenated self-extinguishing fibers include those made from halogenated polymers. One particularly preferred halogenated self-extinguishing fiber is a fiber made from modacryl polymer. "Modacryl polymer" preferably means a copolymer in which the polymer comprises 30 to 70 weight percent acrylonitrile and 70 to 30 weight percent halogen-containing vinyl monomer. The halogen-containing vinyl monomer is at least one monomer selected from, for example, vinyl chloride, vinylidene chloride, vinyl bromide, vinylidene bromide, etc.

[0038] In some embodiments, the modacryl copolymer is acrylonitrile combined with vinylidene chloride. In some embodiments, the modacryl copolymer further contains antimony oxide or antimony oxides. In some preferred embodiments, the modacryl copolymer contains less than 1.5 weight percent of antimony oxide or antimony oxides, or the copolymer is completely antimony-free. By limiting or completely eliminating the amount of any antimony compound added to the copolymer during manufacturing, polymers with very low antimony content and antimony-free polymers can be produced. Representative processes for modacryl polymers, including those that can be modified in this way, are disclosed in U.S. Patent No. 3,193,602, which uses various antimony oxides present in amounts of at least 2 weight percent, preferably 8 weight percent or less, and in U.S. Patent Nos. 5,208,105 and 5,506,042, which use 8 to 40 weight percent of antimony compounds. In some embodiments, the modacryl polymer has at least 26 lines of interest (LOIs). In one preferred embodiment, the modacryl polymer has at least 26 LOIs but does not contain antimony.

[0039] The halogenated self-extinguishing short fibers in at least one second yarn are preferably short fibers having a length of about 2 to 9 centimeters, preferably about 3.5 to 6 centimeters. The halogenated self-extinguishing short fibers in at least one second yarn are preferably short fibers having a diameter of 5 to 25 micrometers and a linear density of 0.5 to 7 decitex.

[0040] The multi-ply yarn includes at least one second yarn having a sheath / core structure comprising a sheath of halogenated self-extinguishing short fibers and a core containing at least one continuous elastomer filament. The halogenated self-extinguishing fibers are in contact with at least one continuous elastomer filament, so that the entire surface of this elastomer filament does not actually need to be completely covered by the short fiber sheath.

[0041] In some embodiments, it is preferable that at least 90% of the core is covered by the sheath so that the thread can be observed under a microscope in a relaxed state; that is, the sheath-core thread is observed in a tension-free state. The actual coverage of the core may vary depending on the degree of tension of the thread, but modacrylic is thought to exert its shielding effect as long as it is in contact with the elastomer core.

[0042] In some embodiments, 5 to 40 weight percent of the total weight of at least one second yarn is at least one continuous elastomer filament. In some embodiments, the ring-spun second yarn has a core containing at least one elastomer filament and a partial coating of halogenated self-extinguishing short fibers. In some preferred embodiments, the core of elastomer filaments contains 5 to 25 weight percent of the total sheath / core single filament linear density of 100 to 1500 decitex.

[0043] As used herein, “core comprising at least one continuous elastomer filament” means a core formed from or containing elastomer filaments, which preferably has the ability to quickly return to its original length after repeated stretching and at least two more times. Preferred elastomer cores include polyurethane yarns such as spandex or elastane, but any fiber that is generally stretchable and resilient can be used. Suitable well-known elastomer yarns include products sold under the trademark names Dorlastan® and Lycra®.

[0044] A preferred at least one continuous elastomer filament is a spandex fiber. As used herein, “spandex” has its usual definition, i.e., a manufactured fiber having a long-chain synthetic polymer in which the fiber-forming material consists of at least 85 weight percent of segmented polyurethane. Among spandex-type segmented polyurethanes are, for example, those described in U.S. Patent Nos. 2,929,801, 2,929,802, 2,929,803, 2,929,804, 2,953,839, 2,957,852, 2,962,470, 2,999,839, and 3,009,901.

[0045] In some processes for producing spandex elastomer filaments, a coalescing jet is used to solidify the spandex filament immediately after extrusion. It is also well known that dry-spun spandex filaments are sticky immediately after extrusion. The combination of joining such sticky filaments together and using a coalescing jet produces a fused multifilament yarn, which is then typically coated with silicone or other finishing agents before winding to prevent sticking in the package. In reality, such fused filaments, which are numerous very small individual filaments that adhere to each other along their length, are superior in many ways to a single filament of spandex of the same linear density.

[0046] In elastomer monofilaments, the elastomer filaments are preferably continuous filaments and can exist in the second yarn in the form of one or more individual filaments or in the form of one or more fused filament groups. However, in preferred elastomer monofilaments, it is preferable to use only one fused filament group. Regardless of whether they exist as one or more individual filaments or one or more fused filament groups, the overall linear density of the elastomer filaments in a relaxed state is generally 17 to 560 decitex (15 to 500 denier), with a preferred linear density range of 44 to 220 decitex (40 to 200 denier).

[0047] It is preferable to incorporate at least one continuous elastomer filament into the second yarn under tension by stretching or stretching at least one continuous elastomer filament before combining it with the short fibers, using a slower feed rate of at least one continuous elastomer filament compared to the final second yarn rate. This stretching can be described as the stretch ratio of the continuous elastomer filament, which is the final second yarn rate divided by the feed rate of the continuous elastomer filament.

[0048] A typical stretch ratio is 1.5 to 5.0, with 1.5 to 3.50 being preferable. A low stretch ratio results in poor elastic recovery, while a very high stretch ratio makes processing the single yarn difficult and the fabric becomes too tight and uncomfortable. The optimal stretch ratio also depends on the weight % content of the elastomer core. While it is possible to stretch and pull the elastomer fibers using a tensioning device, this is not preferred due to the difficulty in reproducing and controlling the tension and stretch. The optimal stretch ratio is ultimately determined on a fabric-by-fabric basis, based on the desired fit and feel of the fabric.

[0049] Incorporating at least one continuous elastomer filament into a second yarn of halogenated self-extinguishing staple fibers can be achieved, for example, in its simplest practical application, by passing a roving, sliver, or aggregate of halogenated self-extinguishing staple fibers through a set of draft rolls to draft the fiber mass, which is then ring-twisted into a single yarn. At least one continuous elastomer filament is typically fed from a bobbin through a set of feed rolls, and subsequently fed into the staple fibers before the final set of draft rollers. Using conventional techniques, the amount of elastic stretch and tension of the final ring-twisted single yarn is determined by increasing or decreasing the slow relative surface velocity of the feed rollers to the surface velocity of the draft rollers.

[0050] In some embodiments, the sheath of at least one second thread may further include heat-resistant polymer fibers as described herein. In some other embodiments, the sheath of at least one second thread may further include cut-resistant heat-resistant polymer fibers as described herein.

[0051] In some embodiments, at least one second yarn sheath may further contain flame-retardant fibers. "Flame-retardant" means that a fabric made solely from that fiber has a carbonization length of 4 inches or less and an afterflame time of 2 seconds or less, according to the ASTM D6143-99 vertical burning test. Suitable flame-retardant fibers include aramid fibers, with meta-aramid fibers being particularly preferred, and a preferred meta-aramid being poly(metaphenylene isophthalamide). Potentially useful flame-retardant fibers include meta-aramid, polyamide-imide, flame-retardant treated (FR) cellulose, FR cotton, FR lyocell, or mixtures thereof. Any number of fibers may be included in the second yarn, as long as the second yarn and the final fabric meet the performance criteria discussed herein.

[0052] When used in a second yarn, the heat-resistant polymer fiber, cut-resistant heat-resistant polymer fiber, or flame-resistant fiber is preferably a short fiber having a length of about 2 to 20 centimeters, preferably about 3.5 to 6 centimeters. Furthermore, when used in a second yarn, the heat-resistant polymer fiber, cut-resistant heat-resistant polymer fiber, and flame-resistant fiber are preferably a short fiber with a diameter of 5 to 25 micrometers and a linear density of 0.5 to 7 decitex.

[0053] In some embodiments, the sheath of at least one second yarn may further include fibers known in the art as antistatic fibers, or fibers having the ability to reduce the accumulation of charge in the yarn or in the resulting fabric. In some preferred embodiments, the sheath of at least one second yarn contains at least 1 to 5 weight percent of antistatic fibers, based on the total weight of at least one second yarn. Preferred antistatic fibers are those that function by the presence of carbon in the fiber as a carbon coating or carbon particles, and are particularly useful in removing the accumulation of charge, but are not considered to be conductive in a practical sense. In some embodiments, aramid fibers containing carbon particles are preferred.

[0054] The second yarn contains little to no inorganic fibers. Since the break resistance advantage of the multi-ply yarn is provided by the first yarn, there is no need to add inorganic fibers to the second yarn for most intended applications.

[0055] A multi-ply yarn is formed from at least a first yarn and at least a second yarn. A multi-ply yarn is made by twisting together at least two individual single yarns. The phrase "twisting together at least two individual single yarns" means that the two single yarns are twisted together without one yarn completely covering the other. This distinguishes a multi-ply yarn from a covered or wrapped yarn in which the first single yarn is substantially or completely wrapped around the second single yarn, so that ideally only the first single yarn is exposed on the surface of the resulting covered yarn.

[0056] In one preferred embodiment, the multi-ply yarn is made from at least two single yarns, the first single yarn being (a) at least one first yarn containing at least 50 weight percent of heat-resistant polymer fibers based on the total weight of the first yarn, in which case at least 30 weight percent of the polymer fibers present in the at least one first yarn are cut-resistant heat-resistant polymer fibers having a cut resistance of 500 gram force or more according to F2992-15, and the at least one first yarn is a sheath containing cut-resistant heat-resistant polymer fibers and a core containing inorganic fibers The second monofilament further comprises a sheath / core structure, wherein the second monofilament is at least one second yarn having a sheath / core structure comprising (b) a sheath of halogenated self-extinguishing short fibers and a core comprising at least one continuous elastomer filament, in which case, based on the total weight of the second yarn, 60 to 95 percent by weight of at least one second yarn is halogenated self-extinguishing fiber, the halogenated self-extinguishing fiber is in contact with at least one continuous elastomer filament, and the second yarn is free of or substantially free of inorganic fibers. Each monofilament may have some degree of twist.

[0057] In some embodiments, a twisted yarn made from two single yarns has a total linear density of 200 to 3000 decitex. Each individual short fiber of either single yarn may have a linear density of 0.5 to 7 decitex, with a preferred linear density range of 1.5 to 3 decitex. The twisted yarns, and the single yarns constituting them, may contain other materials, provided that the function or performance of the yarn or the fabric made from it is not impaired for the desired use.

[0058] Multiple-ply yarns can be produced from single yarns by the process disclosed in Prickett's U.S. Patent No. 6,952,915, and multiple-ply yarns can have a wide range of twists as disclosed therein. For example, either a two-step process or a combined process can be used. In the first step of a two-step process, two or more single yarns are combined parallel to each other without multiple twists and wound into a package. In the next step, the two or more combined single yarns are then ring-twisted together using the reverse twist of the single yarns (if any) to form multiple-ply yarn. Multiple-ply yarns typically have a "Z" twist, and single yarns typically have an "S" twist. Alternatively, multiple-ply yarns can be produced using a combined process that combines both of these steps in a single operation. Equipment commonly used for multiple-plying single yarns is available from equipment manufacturers such as Volkmann and Muratec (formerly Murata).

[0059] Next, the multi-ply yarns can be combined with other identical or different multi-ply yarns to form yarn bundles and create a fabric, or, depending on the requirements of the desired fabric, the individual multi-ply yarns can be used to create a fabric. For example, two or more of the multi-ply yarns described can be combined to form yarn bundles that can be supplied to a knitting machine with or without twist. Alternatively, the yarn bundles can be made using one or more of the multi-ply yarns described above, each having one or more different single yarns, to impart desired properties to the final fabric. Modern knitting machines can knit fabric by supplying multiple multi-ply yarns, so it is not necessary to add twist to the bundles of multi-ply yarns supplied to the knitting machine, but twist can be added to the bundles if necessary.

[0060] The first yarn used in the preferred multi-ply yarn preferably has a poly(paraphenylene terephthalamide) (PPD-T) short fiber sheath, where the PPD-T has a cut length of 3.8 cm (1.5 inches) and a filament density of 1.7 decitex (1.5 denier per filament). The short fiber sheath can be in the form of a 14-29 cotton count yarn.

[0061] The preferred two-ply yarn used is a ring-spun monofilament of 330 decitex (295 denier, equivalent to 18 cotton count). This monofilament has a modacrylic staple fiber sheath that at least partially covers the elastomer core filaments, the modacrylic staple fibers having a cut length of 4.8 cm (1.89 inches) and a filament density of 1.7 decitex (1.5 denier per filament). The elastomer core is a 78 decitex (70 denier) spandex fused filament yarn with a stretch ratio of 3.0 (approximately 200 percent elongation). In some preferred embodiments, approximately 92 weight percent of the second yarn consists of modacrylic staple fibers, and 8 weight percent of the second yarn is the elastomer core.

[0062] The present invention also relates to a cut-resistant woven or knitted fabric made from a multi-ply yarn or a bundle of yarns containing multi-ply yarns, wherein the multi-ply yarn comprises at least one first yarn and at least one second yarn as described herein.

[0063] Specifically, the present invention relates to a cut-resistant woven or knitted fabric made from a multi-ply yarn made from at least two single yarns, wherein the first single yarn is (a) at least one first yarn containing at least 50 weight percent of heat-resistant polymer fibers based on the total weight of the first yarn, in which case at least 30 weight percent of the polymer fibers present in the at least one first yarn are cut-resistant heat-resistant polymer fibers having a cut resistance of 500 gram force or more according to F2992-15, and the at least one first yarn is a sheath and The second monofilament further comprises a sheath / core structure having a core containing inorganic fibers, wherein the second monofilament is at least one second yarn having a sheath / core structure comprising a sheath of halogenated self-extinguishing short fibers and a core containing at least one continuous elastomer filament, in which case, based on the total weight of the second yarn, 60 to 95 percent by weight of at least one second yarn is halogenated self-extinguishing fiber, the halogenated self-extinguishing fiber is in contact with at least one continuous elastomer filament, and the second yarn does not contain or substantially contains inorganic fibers. Preferably, the cut-resistant woven or knitted fabric has a maximum afterflame time of 2 seconds or less and a weight loss of 5 percent by weight or less when tested according to NFPA-2112-2018.

[0064] At least one first yarn and at least one second yarn act synergistically together in the multi-twist yarn, and at least one continuous elastomer filament incorporated into the yarn provides improved elasticity and resilience, while heat-resistant staple fibers provide structure in flames, and heat-resistant, cut-resistant organic staple fibers and inorganic filaments provide excellent cut resistance to the fabric. Fabrics made from such yarns are soft, comfortable, non-abrasion, and also cut-resistant.

[0065] Twisting the first and second threads together helps to keep the elastomer monofilament stretched without looping itself when relaxed. Furthermore, when the bundle is composed of twisted threads, controlling the tension of the threads during knitting and weaving is less critical.

[0066] Woven and / or knitted fabrics may contain the various twisted yarns described herein. Preferred woven and knitted fabrics, when tested according to NFPA-2112-2018, have a maximum afterflame time of 2 seconds or less and a weight loss of 5 weight percent or less.

[0067] The preferred fabric is a knitted fabric, and any suitable knitting pattern is acceptable. Cut resistance and comfort are influenced by the tightness of the knitted fabric, which can be adjusted to meet any specific requirements. A very effective combination of cut resistance and comfort in many cut-resistant articles has been found, for example, in single jersey and terry knit patterns. Preferably, the fabric is about 4 to 30 ounces / yard. 2 Preferably 6-25 ounces / yard 2 Having a basis weight, the fabric is at the upper limit of the basis weight range, providing higher thermal and cut protection.

[0068] Articles may include the various twisted yarns described herein, or articles may be made from the aforementioned fabrics containing the various twisted yarns described herein. Particularly useful articles include gloves, sleeves, and aprons.

[0069] Test method Afterflame and weight loss were determined according to NFPA 2112-2018 "Standard on Flame-Resistant Clothing for Protection of Industrial Personnel Against Short-Duration Thermal Exposures from Fire," specifically the procedure outline in Section 8.8 of the standard.

[0070] The determination of “heat-resistant polymer fibers” as discussed herein can be achieved by using ASTM E2105-2016 – Standard Practice for General Techniques of Thermogravimetric Analysis (TGA) Coupled With Infrared Analysis (TGA / IR). Analysis of whether the synthetic organic polymer retains 90 percent of the original fiber weight is performed by heating the sample in air at a rate of 20°C per minute up to 500°C. [Examples]

[0071] Examples of multi-twist yarns and knitted fabrics made from them are shown in Examples 1, 2, and 3 and Comparative Example A, and are summarized in Table 5.

[0072] Example 1 The double-twist elastic yarn was made by double-twisting a first yarn and a second yarn.

[0073] The first yarn was a 14-count cotton sheath-core yarn with a para-aramid fiber sheath and a 50-micron stainless steel wire core, spun on a ring spinning frame. The para-aramid fiber was a 2-inch poly(paraphenylene terephthalamide) staple fiber.

[0074] The second yarn is an 18 cotton count sheath-core yarn made by core spinning a 2-inch modacrylic staple fiber ring spinning frame around a 70 denier spandex core, with the spandex core being stretched three times when incorporated (spun) into the sheath-core yarn.

[0075] The double-twist elastic yarn obtained by double-twisting the first and second threads had a total cotton count of 16 / 2, or 675 denier. The relative amounts of the yarn components are shown in Table 2.

[0076] The obtained multi-ply elastic yarn was knitted into a 13-gauge sleeve using a Shima-Seiki glove knitting machine. The resulting sleeve exhibited excellent fit to the hand and shape conformability. Fabric samples from the obtained sleeve were subjected to a fire-resistant glove test method according to the NFPA-2112-2018 standard. The resulting stretch fabric was found to have a 0-second afterflame at 4.8% of its weight consumed during the test, which was below the 2-second maximum afterflame requirement and 5% weight loss limit permitted by the specification.

[0077] [Table 2] Example 2 The multi-ply elastic yarn of Example 1 was repeated, with the following exceptions. The first yarn was a 26 cotton count yarn having a para-aramid fiber sheath and a stainless steel wire core made of a 35-micron stainless steel wire core. The second yarn was a 32 cotton count yarn having a modacrylic sheath and a 40-denier spandex core that was stretched three times during spinning.

[0078] Similar to Example 1, the resulting double-twisted elastic yarn, produced by double-twisting the first and second yarns, had a total cotton count of 29 / 2 or 371 denier. The relative amounts of the yarn components are shown in Table 3.

[0079] The obtained multi-ply elastic yarn was knitted into an 18-gauge sleeve on a Shima-Seiki glove knitting machine. The resulting sleeve exhibited excellent shape conformability. Fabric samples from the obtained sleeves were washed to remove knitting oil and finishing agents, and then subjected to a combustion test according to the fire-resistant glove test method detailed in the NFPA-2112-2018 standard. The resulting elastic fabric was found to have a 0-second afterflame with 3.3% of its weight consumed during the test, which was below the 2-second maximum afterflame requirement and 5% weight loss limit permitted by the specification.

[0080] [Table 3] Example 3 The multi-twist elastic yarn of Example 1 was repeated, with the following points to note.

[0081] The first yarn was a 19.5 cotton count yarn with a stainless steel wire core made of a para-aramid fiber sheath and a 45-micron stainless steel wire core. The second yarn was a 32 cotton count sheath-core yarn with a 40-denier spandex core that was stretched three times during spinning, the sheath being a blend of 82 wt% modacrylic staples and a 10 wt% blend of 2-inch cut meta-aramid staples, specifically the meta-aramid blend containing 93 wt% poly(methaphenylene isophthalamide) staples, 5 wt% poly(paraphenylene terephthalamide) staples, and 2 wt% carbon-core nylon antistatic fibers.

[0082] Similar to Example 1, the resulting double-twisted elastic yarn, produced by double-twisting the first and second yarns, had a total cotton count of 24 / 2 or 439 denier. The relative amounts of the yarn components are shown in Table 4.

[0083] The resulting multi-twist elastic yarn was knitted into an 18-gauge sleeve using a Shima-Seiki glove knitting machine. The resulting sleeve exhibited excellent shape conformability.

[0084] The fabric samples of the prepared sleeves were washed to remove knitting oil and finishing agents, and then subjected to a combustion test according to the fire-resistant glove test method detailed in the NFPA-2112-2018 standard. The resulting stretch fabric was found to have 0 seconds of afterflame with 3.9% of its weight consumed during the test, which was below the maximum afterflame requirement of 2 seconds and the 5% weight loss limit permitted by the specification.

[0085] Another fabric sample of the fabricated sleeve was subjected to a combustion test according to the fire-resistant glove test method detailed in the EN407:2020 standard. The resulting stretchable fabric was found to have zero afterflame and zero afterglow after 3 and 15 seconds of exposure to flame, which falls below the maximum afterflame requirement of 2 seconds and maximum afterglow requirement of 5 seconds permitted by the specification.

[0086] [Table 4] Comparative example A A comparative multi-ply elastic yarn similar to that of Example 3 was prepared, but the first yarn, which had a para-aramid fiber sheath and a stainless steel wire core, was made of 1.5-inch poly(paraphenylene terephthalamide) staple fibers and a 45-micron stainless steel wire core. The second yarn was again a 32-count cotton sheath-core yarn, but had a sheath of only nylon staple fiber core-spun fibers with a cut length of 1.5 inches around a 40-denier spandex core.

[0087] The resulting 24's-2 count double-twist elastic yarn was knitted into an 18-gauge sleeve using a Shima-Seiki glove knitting machine. The resulting sleeve exhibited excellent shape conformity.

[0088] However, the prepared samples were subjected to a combustion test according to the fire-resistant glove test method detailed in the EN407:2020 standard. The resulting stretch fabric was found to have an afterburn of at least 25 seconds after being exposed to flame for 3 seconds, which was higher than the maximum afterburn requirement of 20 seconds required to achieve even the lowest rank specified in the specification.

[0089] Because excessive afterflame occurred after only 3 seconds of flame exposure, no further testing was conducted for either the 15-second exposure in the EN407 test or the 12-second exposure in the NFPA-2112 test.

[0090] [Table 5] This disclosure includes the following embodiments. <Embodiment 1> (a) at least one first yarn comprising at least 50 weight percent of heat-resistant polymer fibers, wherein at least 30 weight percent of the polymer fibers present in the at least one first yarn are cut-resistant heat-resistant polymer fibers having a cut resistance of 500 gram force or more according to ASTM F2992-15, (b) A multi-ply yarn suitable for use in flame-retardant, cut-resistant fabrics, comprising: a sheath / core structure having a sheath of halogenated self-extinguishing short fibers and a core comprising at least one continuous elastomer filament; A multi-ply yarn in which 60 to 95 percent by weight of at least one second yarn is a halogenated self-extinguishing fiber, the halogenated self-extinguishing fiber is in contact with the at least one continuous elastomer filament, and the second yarn is free of or substantially free of inorganic fibers. <Embodiment 2> The multi-ply yarn according to Embodiment 1, wherein the at least one first yarn has a sheath / core structure comprising a sheath containing the cut-resistant, heat-resistant polymer fibers and a core containing inorganic fibers. <Embodiment 3> The multi-ply yarn according to Embodiment 1 or 2, wherein the heat-resistant polymer fiber or the cut-resistant heat-resistant polymer fiber is an aramid copolymer, para-aramid, polybenzazole, polybenzimidazole, polyimide, or a mixture thereof. <Embodiment 4> The multi-ply yarn according to Embodiment 3, wherein the heat-resistant polymer fiber or the cut-resistant heat-resistant polymer fiber is para-aramid. <Embodiment 5> The para-aramid fiber is poly(paraphenylene terephthalamide), as described in Embodiment 4. <Embodiment 6> The multi-ply yarn according to any one of embodiments 1 to 5, wherein the at least one first yarn further comprises a flame-retardant fiber that is not cut-resistant. <Embodiment 7> The multi-ply yarn according to Embodiment 6, wherein the flame-retardant fiber is meta-aramid, polyamide-imide, flame-retardant treated (FR) cellulose, FR cotton, FR lyocell, or a mixture thereof. <Embodiment 8> The flame-resistant fiber is meta-aramid, as described in Embodiment 7 of the multi-twist yarn. <Embodiment 9> The multi-twist yarn according to Embodiment 8, wherein the meta-aramid is poly(metaphenylene isophthalamide). <Embodiment 10> The multi-ply yarn according to any one of embodiments 1 to 9, wherein 80 to 95 percent by weight of the total weight of at least one second yarn is the halogenated self-extinguishing fiber. <Embodiment 11> The halogenated self-extinguishing fiber is a modacrylic fiber, as described in any one of Embodiments 1 to 10. <Embodiment 12> The multi-ply yarn according to any one of embodiments 1 to 11, wherein 5 to 40 percent by weight of the total weight of the at least one second yarn is the at least one continuous elastomer filament. <Embodiment 13> The multi-ply yarn according to any one of embodiments 1 to 12, wherein the at least one continuous elastomer filament is a spandex filament. <Embodiment 14> The inorganic fiber is a metal filament, as described in any one of embodiments 1 to 13. <Embodiment 15> The multi-ply yarn according to any one of embodiments 1 to 14, wherein the sheath of at least one second yarn further comprises heat-resistant polymer fibers. <Embodiment 16> The multi-ply yarn according to any one of embodiments 1 to 15, wherein the sheath of at least one second yarn further comprises flame-retardant fibers that are not cut-resistant. <Embodiment 17> The multi-ply yarn according to Embodiment 16, wherein the flame-resistant fiber is meta-aramid, polyamide-imide, or a mixture thereof. <Embodiment 18> The flame-resistant fiber is meta-aramid, as described in Embodiment 17, of the multi-twist yarn. <Embodiment 19> The multi-ply yarn according to Embodiment 18, wherein the meta-aramid is poly(metaphenylene isophthalamide). <Embodiment 20> The sheath of at least one second yarn further comprises an antistatic fiber, as described in any one of embodiments 1 to 19. <Embodiment 21> A woven or knitted fabric containing the various twisted yarns described in any one of Embodiments 1 to 20. <Embodiment 22> A woven or knitted fabric containing multiple twisted yarns as described in Embodiment 21, wherein, when tested according to NFPA-2112-2018, the maximum afterflame time is 2 seconds or less and the weight loss is 5 weight percent or less. <Embodiment 23> An article comprising a woven or knitted fabric as described in Embodiment 21 or 23. <Embodiment 24> The article according to Embodiment 23, which is in the form of a glove, sleeve, or apron.

Claims

1. (a) At least one first yarn comprising at least 50 weight percent of heat-resistant polymer fibers, wherein at least 30 weight percent of the polymer fibers present in the at least one first yarn are cut-resistant heat-resistant polymer fibers having a cut resistance of 500 gram force or more according to ASTM F2992-15, and the at least one first yarn has a sheath / core structure comprising a sheath containing the cut-resistant heat-resistant polymer fibers and a core containing inorganic fibers, (b) A multi-ply yarn suitable for use in flame-retardant, cut-resistant fabrics, comprising: a sheath / core structure having a sheath of halogenated self-extinguishing short fibers and a core comprising at least one continuous elastomer filament; A multi-ply yarn in which 60 to 95 percent by weight of at least one second yarn is a halogenated self-extinguishing fiber, the halogenated self-extinguishing fiber is in contact with the at least one continuous elastomer filament, and the second yarn is free of or substantially free of inorganic fibers.

2. The multi-ply yarn according to claim 1, wherein the heat-resistant polymer fiber or the cut-resistant heat-resistant polymer fiber is an aramid copolymer, para-aramid, polybenzazole, polybenzimidazole, polyimide, or a mixture thereof.

3. The multi-ply yarn according to claim 1 or 2, wherein the at least one first yarn further comprises a flame-retardant fiber that is not cut-resistant.

4. The multi-ply yarn according to claim 3, wherein the flame-retardant fiber is meta-aramid, polyamide-imide, flame-retardant treated (FR) cellulose, FR cotton, FR lyocell, or a mixture thereof.

5. The multi-ply yarn according to claim 4, wherein the flame-resistant fiber is meta-aramid.

6. The multi-ply yarn according to any one of claims 1 to 5, wherein 80 to 95 percent by weight of the total weight of at least one second yarn is the halogenated self-extinguishing fiber.

7. The multi-ply yarn according to any one of claims 1 to 6, wherein the halogenated self-extinguishing fiber is a modacrylic fiber.

8. The multi-twisted yarn according to any one of claims 1 to 7, wherein the inorganic fiber is a metal filament.

9. The multi-ply yarn according to any one of claims 1 to 8, wherein the sheath of at least one second yarn further comprises heat-resistant polymer fibers.

10. The multi-ply yarn according to any one of claims 1 to 9, wherein the sheath of at least one second yarn further comprises flame-retardant fibers that are not cut-resistant.

11. The multi-ply yarn according to claim 10, wherein the flame-resistant fiber is meta-aramid, polyamide-imide, or a mixture thereof.

12. A woven or knitted fabric containing the twisted yarns described in any one of claims 1 to 11.

13. An article comprising a woven or knitted fabric as described in claim 12.

14. The article according to claim 13, which is in the form of a glove, sleeve, or apron.

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