CN111485294B

CN111485294B - High-tenacity or high-load-bearing nylon fiber and yarn and fabric thereof

Info

Publication number: CN111485294B
Application number: CN202010292743.6A
Authority: CN
Inventors: D.A.布卢姆; C.D.麦克瑙尔
Original assignee: Invista North America LLC
Current assignee: Invista North America LLC
Priority date: 2014-10-15
Filing date: 2015-10-13
Publication date: 2023-03-31
Anticipated expiration: 2035-10-13
Also published as: CN111485294A; WO2016061103A1; MX2017004867A; BR112017007736A2; KR20170067845A; EP3207173A4; EP3207173A1; CN107002330A; US20170253997A1; RU2017116442A; RU2017116442A3; IL251686B; CN107002330B; IL251686A0

Abstract

The present disclosure provides high strength or load bearing nylon fibers having a break tenacity greater than 7.5g/den and/or a tenacity at 10% elongation greater than 4.0g/den, as well as yarns, fabrics, and articles thereof and methods of producing the same.

Description

High-tenacity or high-load-bearing nylon fiber and yarn and fabric thereof

The present application is a divisional application of the following applications: application date: 10 months and 13 days in 2015; application No.: 2015800685073; the invention name is as follows: "high tenacity or high load-bearing nylon fibers and yarns and fabrics thereof".

Technical Field

The present disclosure relates to the preparation of improved nylon staple fibers having desirably high strength quantified by fracture toughness and toughness at 7% and 10% elongation. These nylon staple fibers are produced by: the process includes the steps of preparing tows of relatively uniformly spun and quenched nylon filaments, drawing and annealing these tows in the presence of steam, and then cutting or otherwise converting the drawn and annealed tows into the desired high strength nylon staple fibers.

The nylon staple fibers so produced can be blended with other fibers such as cotton staple fibers to produce a yarn that also has desirably high strength. These yarns can then be made into fabrics and other articles that advantageously can be lightweight, comfortable, lower cost, and durable, and thus are particularly suitable for use in or as, for example, military apparel, such as combat uniforms or other rugged use apparel.

The present disclosure also relates to nonwoven composites of high tenacity nylon fibers and cellulosic materials or recycled synthetic or natural fiber technologies. End uses for these composites include, but are not limited to, industrial (felt/backing/filtration/insulation), apparel (including lining fabrics), footwear, bag/backpack hard shells, durable and semi-durable (disposable or semi-disposable) garments or PPEs, including FR (chemically treated or combined with inherent FR fiber technology), biochemical or other specialty protective apparel.

Background

Nylon has been manufactured and used commercially for many years. The first nylon fibers were nylon 6, poly (hexamethylene adipamide), and nylon 6,6 fibers were still being made and used commercially as the primary nylon fiber. A large number of other nylon fibers, particularly nylon 6 fibers prepared from caprolactam, are also being made and are in commercial use. Nylon fibers are used in yarns for textile fabrics, as well as for other purposes. For textile fabrics, there are basically two main yarn classes, namely continuous filament yarns and yarns made from staple fibers (i.e. cut fibers).

Nylon staple fibers are conventionally made by: melt spinning a nylon polymer into filaments, collecting a substantial amount of these filaments as a tow, subjecting the tow to a drawing operation, and then converting the tow into staple fibers (e.g., in a staple cutter). The tow typically contains thousands of filaments, and generally has a total denier of about several hundred thousand (or more). The pulling operation involves delivering the tow between a set of feed rollers and a set of pulling rollers (operating at a higher speed than the feed rollers) to increase the orientation of the nylon polymer in the filaments. Drawing is often combined with an annealing operation to increase nylon crystallinity in the filament of the tow prior to converting the tow to staple fibers.

One of the advantages of nylon staple fibers is that they are easily blended with, among other things, natural fibers such as cotton (often referred to as staple fibers) and/or with other synthetic fibers to achieve the advantages that can be derived from such blending. One particularly desirable form of nylon staple fiber has been used for many years to blend with cotton, particularly to improve fabrication from yarns including blends of cotton and nylonDurability and economy of the fabric. This is because such nylon staple fibers have relatively high load-bearing toughness, as described in Hebeler, U.S. Pat. nos. 3,044,250;3,188,790;3,321,448; and U.S. patent No. 3,459,845, the disclosures of which are hereby incorporated by reference in their entirety. As explained by Hebeler, the load bearing capacity of nylon staple fibers is conventionally measured as tenacity (T) at 7% elongation ₇ ) And T is ₇ Parameters have long been accepted as standard measurements and are easily read on an Instron tester.

The Hebeler process for making nylon staple fibers involves the nylon spinning, tow formation, drawing and converting operations described previously. Improvements in the Hebeler process for making nylon staple fibers were subsequently made by modifying the nature of the tow pulling operation and by adding a specific type of annealing (or high temperature treatment) and subsequent cooling step to the overall process. For example, thompson discloses nylon staple fiber preparation in U.S. Pat. nos. 5,093,195 and 5,011,645, wherein a nylon 6,6 polymer, for example having a formic acid Relative Viscosity (RV) of 55, is spun into filaments which are then drawn, annealed, cooled and cut into staple fibers having a tenacity T at break of about 6.8 to 6.9, a denier per filament of about 2.44, and a load-bearing capacity T of from about 2.4 to 3.2 ₇ . These nylon staple fibers are further disclosed in the Thompson patent as being blended with cotton and formed into yarns having improved yarn strength. (both Thompson patents are incorporated by reference in their entirety.)

Nylon staple fibers prepared according to Thompson technology have been incorporated into NYCO yarns (generally at a 50: 50 nylon/cotton ratio) where these yarns are used to prepare NYCO fabrics. These NYCO fabrics (e.g., woven fabrics) have application in military combat uniforms and apparel. While these fabrics have generally proven satisfactory for military or other rugged apparel uses, military authorities, for example, are constantly searching for improved fabrics that may be lighter in weight, less costly, and/or more comfortable, and yet still be highly durable or even have improved durability.

Disclosure of Invention

The present invention relates to the production of nylon staple fibers having very high tenacity (both fracture tenacity and tenacity at low elongation). The present invention relates to the use of steam to allow for higher draw ratios versus the normal draw ratios currently in use. The product is then annealed and dried under tension. Annealing/furnace drying under tension helps remove excess moisture gained during steam pulling. The resulting fiber fracture toughness has increased from an average of 7.1 grams/den to the 7.5 to 7.75 grams/denier range. Toughness at 10% elongation has also increased by 10-20% higher for standard products or previously described improvements. Fabrics made from this fiber are expected to exhibit higher or comparable strength in terms of grab and tear strength but a weight loss of as much as 1.0oz.

Accordingly, one aspect of the present invention is directed to high strength or load bearing nylon staple fibers having a fracture toughness greater than 7.5g/den and/or a toughness at 10% elongation greater than 4.0 g/den.

Another aspect of the invention relates to a yarn at least a portion of which is spun from high strength or load bearing nylon staple fibers having a tenacity at break of greater than 7.5g/den and/or a tenacity at 10% elongation of greater than 4.0 g/den.

In one embodiment, the yarn is made by blending the nylon staple fibers with at least one companion staple fiber.

In one embodiment, the yarns may be nylon/cotton (NYCO) yarns, which may be subsequently woven into durable and optionally lightweight woven NYCO fabrics, which may be particularly suitable for military or other rugged apparel uses.

Another aspect of the invention relates to less than 6.0oz./yd ² Of a light weight fabric which meets or exceeds a weight for more than 6.0oZ./yd ² The current military fabric strength and tear specifications established for the fabric. The fabric is comprised of a blend of fibers at least a portion of which comprises high strength or load bearing nylon fibers having a tenacity at break of greater than 7.5g/den and a tenacity at 10% elongation of greater than 4.0 g/den.

Another aspect of the invention relates to an article at least a portion of which comprises a high strength or load bearing nylon fiber having a tenacity at break of greater than 7.5g/den and/or a tenacity at 10% elongation of greater than 4.0 g/den.

Another aspect of the invention relates to a nonwoven fabric composite comprising high tenacity fibers and cellulosic material or recycled synthetic or natural fibers.

In one embodiment, the high tenacity fibers used in the nonwoven fabric composite comprise load bearing nylon fibers having a fracture tenacity greater than 7.5g/den and/or a tenacity at 10% elongation greater than 4.0 g/den.

Yet another aspect of the invention relates to a process for producing a high strength or load bearing nylon fiber having a fracture toughness of greater than 7.5g/den and/or a toughness at 10% elongation of greater than 4.0 g/den. The method comprises the following steps: melt spinning a nylon polymer into filaments; uniformly quenching the filaments and forming a tow from a plurality of these quenched filaments; subjecting the tow to drawing in the presence of steam; annealing under tension; and subsequently converting the resulting drawn and annealed tow into staple fibers suitable for formation into, for example, textile yarns.

Detailed Description

The present disclosure provides high strength or load bearing nylon fibers having a fracture toughness of greater than 7.5g/den and/or a toughness at 10% elongation of greater than 4.0g/den, yarns, fabrics, and other articles at least a portion of which are prepared from these fibers, and methods for their production.

The present disclosure also provides nonwoven fabric composites comprising high tenacity fibers and cellulosic or recycled synthetic or natural fibers.

As used herein, the terms "durable" and "durability" refer to the tendency of a fabric so characterized to have suitably high tear strength and abrasion resistance for the intended end use of such fabric, as well as to retain these desirable properties for a suitable length of time after the start of use of the fabric.

As used herein, the terms "blended" or "blended" when referring to a textile yarn means a mixture of at least two types of fibers, wherein the mixture is formed in such a way that the individual fibers of each type of fiber are substantially completely intermixed with the other types of individual fibers to provide a substantially homogeneous mixture of fibers having sufficient entanglement to maintain their integrity in further processing and use.

As used herein, cotton count refers to a yarn counting system based on the length of 840 yarn, and wherein the count of yarn is equal to the number of 840 strands required to weigh 1 pound.

All numerical values recited herein are to be understood as modified by the term "about".

Some embodiments are based on the preparation of improved nylon staple fibers having certain specified properties, wherein the improved nylon staple fibers are blended with at least one other fiber, and on the subsequent preparation of yarns and fabrics woven from these yarns. Other fibers can include cellulosic materials such as cotton, modified cellulosic materials such as FR-treated cellulose, polyester, rayon, animal fibers such as wool, fire-resistant (FR) polyester, FR nylon, FR rayon, FR-treated cellulose, meta-aramid, para-aramid, modacrylic, phenolic fibers, melamine, polyvinyl chloride, antistatic fibers, PBO (1, 4-phthalic acid, polymer with 4, 6-diamino-1, 3-benzenediol hydrochloride), PBI (polybenzimidazole), and combinations thereof. Some embodiments of nylon staple fibers may provide an increase in strength and/or abrasion resistance to the yarn and fabric. This is particularly true for combinations with relatively weak fibers such as cotton and wool.

Specific characteristics of the nylon staple fibers made and used herein include fiber denier, fiber tenacity, and fiber load-bearing capacity as defined in terms of fiber tenacity at 7% and 10% elongation.

The desired nylon staple fiber materials herein are realized based on the use in the manufacture of staple fibers of nylon polymeric filaments and tows having certain selected properties and treated using certain selected treatment operations and conditions. In particular, the inventors have found that the introduction of steam between the feed and draw modules and/or tension during annealing significantly reduces the pulling force, thus allowing the nylon supply to be drawn much further than any dry drawing process. In one embodiment of the invention, steam is introduced into the normal nylon staple fiber process by adding a steam chamber between the feeding and pulling modules, as this allows for removal of excess water prior to annealing. Without being limited to any particular theory, it is believed that the steam chamber adds enough heat/steam to reduce the pulling force of the nylon and helps localize the pulling to the steam chamber rather than above or at the exit of the feed roll. The steam may be controlled by pressure.

The nylon polymer for nylon filament spinning of the present invention itself can be produced in a conventional manner. Nylon polymers suitable for use in the processes and filaments of some embodiments are comprised of synthetic melt spinnable or melt spun polymers. These nylon polymers may comprise polyamide homopolymers, copolymers, and mixtures thereof, which are predominantly aliphatic, i.e., less than 85% of the amide linkages of the polymer are attached to two aromatic rings. Widely used polyamide polymers such as poly (hexamethylene adipamide) as nylon 6,6 and poly (epsilon-caproamide) as nylon 6, and copolymers and blends thereof may be used according to some embodiments. Other polyamide polymers that may be advantageously used are nylon 12, nylon 4,6, nylon 6, 10, nylon 6, 12, nylon 12, 12, and copolymers and mixtures thereof. Illustrative of polyamides and copolyamides that may be employed in the processes, fibers, yarns and fabrics of some embodiments are those described in U.S. Pat. Nos. 5,077,124, 5,106,946 and 5,139,729, all to Cofer et al, and polyamide polymer blends disclosed by Gutmann in International Chemical Fibers International (1996, 12 months, vol. 46, 418 to 420). These publications are incorporated herein by reference in their entirety.

Nylon polymers used in the preparation of nylon staple fibers are conventionally prepared by reacting appropriate monomers, catalysts, antioxidants, and other additives such as plasticizers, delusterants, pigments, dyes, light stabilizers, heat stabilizers, antistatic agents for reducing static electricity, additives for modifying dye ability, agents for modifying surface tension, and the like. The polymerization is usually carried out in a continuous polymerizer or a batch reactor. The molten polymer thus produced is then typically introduced into a textile assembly where the polymer is forced through a suitable spinneret and formed into filaments that are quenched and then formed into tows for final processing into nylon staple fibers. As used herein, a textile assembly includes an assembly cover at the top of the assembly, a spinneret plate at the bottom of the assembly, and a polymeric filter holder sandwiched between the two aforementioned components. The filter retainer has a central recess therein. The cover and recess in the filter holder cooperate to define a closed pocket in which a polymeric filter media, such as sand, is received. The interior of the assembly provides passages to allow a stream of molten polymer supplied by a pump or extruder to travel through the assembly and ultimately through the spinneret. The spinneret has an array of small precision holes extending therethrough that deliver polymer to the lower surface of the assembly. The mouths of the holes form an array of orifices on a lower surface of the spinneret plate, the surface defining the top of the quench zone. The polymer exiting these orifices is in the form of filaments which are then directed downwardly through a quench zone.

The extent of polymerization effected in the continuous polymerizer or batch reactor can be generally quantified by means of a parameter known as relative viscosity or RV. RV is the ratio of the viscosity of the nylon polymer solution in formic acid solvent to the viscosity of the formic acid solvent itself. RV is considered an indirect indication of nylon polymer molecular weight. For purposes herein, increasing RV for nylon polymer is considered synonymous with increasing molecular weight for nylon polymer.

As the molecular weight of nylon increases, its handling becomes more difficult due to the increased viscosity of the nylon polymer. Thus, a continuous polymerizer or batch reactor is typically operated to provide a nylon polymer for final processing into staple fibers, wherein the nylon polymer has an RV value of about 60 or less.

It is known that for some purposes, the provision of nylon polymers having a larger molecular weight, i.e., nylon polymers having RV values greater than 70 to 75 and up to 140 or even 190 and higher, can be advantageous. High RV nylon polymers of this type are known to have improved resistance to flex abrasion and chemical degradation. Thus, this high RV nylon polymer is particularly suitable for spinning into nylon staple fibers, which can be advantageously used in the preparation of papermaking felts. Procedures and equipment for making high RV nylon polymers and making staple fibers therefrom are described in U.S. patent No. 5,236,652 to Kidder and 6,235,390 to Schwinn and West; 6,605,694; U.S. Pat. nos. 6,627,129 and 6,814,939. All of these patents are incorporated herein by reference in their entirety.

According to some embodiments, it has been found that staple fibers made from nylon polymers having RV values substantially consistent with or in some cases higher than values substantially obtained via polymerization in a continuous polymerizer or batch autoclave unexpectedly exhibit such increased fiber fracture toughness and increased toughness and 10% elongation as standard products or the previously described improvements when processed according to spinning, quenching, feeding, and drawing in the presence of steam and annealing procedures described herein. When these nylon staple fibers having improved tenacity are blended with one or more other fibers, such as cotton staple fibers, a textile yarn having improved strength and lower weight can be achieved. Fabrics, such as NYCO fabrics, woven from these yarns exhibit the advantages described thus far with respect to durability, optionally lighter weight, improved comfort, and/or potentially lower cost.

According to the staple fiber preparation process herein, the nylon polymer melt spun into tow-forming filaments by one or more spinning assembly spinnerets and quenched will have RV values ranging from 45 to 100, including from 55 to 100, from 46 to 65; from 50 to 60; and from 65 to 100. Nylon polymers having these RV properties can be prepared, for example, using melt blending of a polyamide concentrate procedure, such as the process disclosed in the Kidder'652 patent mentioned above. Kidder discloses certain examples in which the additive incorporated into the polyamide concentrate is a catalyst for increasing the Relative Viscosity (RV) of formic acid. Higher RV nylon polymers, such as nylons having RV from 65 to 100, which are useful for melting and spinning, can also be provided by means of a Solid Phase Polymerization (SPP) step in which nylon polymer flakes or particles are adjusted to increase RV to the desired degree. These Solid Phase Polymerization (SPP) procedures are well known and are disclosed in more detail in the Schwinn/West '390,' 694, '129 and' 939 patents mentioned above.

Nylon polymeric material having the requisite RV properties as specified herein is fed to the textile assembly, for example, via a twin screw melter device. In the spinning assembly, the nylon polymer is spun into a plurality of filaments by extrusion through one or more spinnerets. For the purposes herein, the term "filament" is defined as a relatively flexible, macroscopically homogeneous body having a high ratio of length to width across its cross-sectional area perpendicular to its length. The filament cross-section may be of any shape, but is typically circular. Herein, the term "fiber" may also be used interchangeably with the term "filament".

Each individual spinneret position can contain from 100 to 1950 filaments in an area as small as 9 inches by 7 inches (22.9 cm by 17.8 cm). The textile assembly machine can contain from one to 96 positions, each of which provides multiple bundles of filaments, which are ultimately combined into a single tow band for pulling/downstream processing with respect to other tow bands.

After exiting the spinnerets of the textile assembly, the molten filaments that have been extruded through each spinneret typically pass through a quench zone, wherein a variety of quench conditions and configurations can be used to solidify the molten polymer filaments and render them suitable for collecting together into a tow. Quenching is most commonly carried out by: a cooling gas (e.g., air) is passed toward, onto, with, around, and through the filament bundle being extruded into the quench zone from each spinneret position within the textile assembly.

One suitable quenching configuration is cross-flow quenching, in which a cooling gas, such as air, is forced into the quenching zone in a direction substantially perpendicular to the direction in which the extruded filaments are traveling through the quenching zone. Cross-flow quenching arrangements are described in U.S. Pat. No. 3,022,539;3,070,839;3,336,634;5,824,248; U.S. Pat. nos. 6,090,485, 6,881,047, and 6,926,854, all of which are incorporated herein by reference.

In one embodiment of the staple fiber preparation process herein, extruded nylon filaments used to ultimately form the desired nylon staple fibers are spun, quenched and formed into tows having both positional uniformity and uniformity of quenching conditions, such as described in U.S. patent applications published as 2011/0177737 and 2011/0177738, the teachings of which are incorporated herein by reference in their entirety.

The quenched textile filaments can then be combined into one or more tows. The tows formed from filaments from one or more spinnerets are then subjected to a two-stage continuous operation in which the tows are drawn and annealed in the presence of steam.

The drawing of the tow is generally carried out primarily in an initial or first drawing stage or zone, with a tow band passing between a set of feed rollers and a set of draw rollers (operating at higher speeds) to increase the crystallographic orientation of the filaments in the tow. The degree to which the tow is pulled can be quantified by specifying the pull rate, which is the ratio of the higher peripheral speed of the pull roll to the lower peripheral speed of the feed roll. The effective draw ratio is calculated by multiplying the first draw ratio by the second draw ratio.

The first pulling stage or zone may include sets of feed and pulling rolls, as well as other tow guide and take-up rolls, such as brake pins. The pulling roll surface may be made of metal (e.g., chrome) or ceramic. It has been found that ceramic pulling roll surfaces are particularly advantageous to permit the use of relatively high draw ratios specified for use in connection with the staple fiber making process herein. Ceramic rollers improve roller life and provide a surface that is less prone to winding. The use of ceramic Rolls in order to improve roll life and reduce Fiber adhesion to roll surfaces is also disclosed in the paper presented in International Fiber Journal (International Fiber Journal, 2002, 2.1, 17: "Textile and Bearing Technology for Separator Rolls (Zeitz et al), and U.S. patent No. 4,794,680, both incorporated herein by reference.

While the maximum degree of drawing of the filament tow herein occurs in the initial or first drawing stage or zone, some additional drawing of the tow will generally also occur in the second or annealing and drawing stage or zone described below. The total amount of draw experienced by the filament bundle herein can be quantified by specifying a total effective draw ratio that takes into account the draw that occurs in the first initial draw stage or zone and in the second zone or stage where annealing and some additional draw are simultaneously performed.

In the process of some embodiments, the tow of nylon filaments is subjected to a total effective draw rate of from 2.3 to 5.0, including from 3.0 to 4.0. In one embodiment, where the denier per filament of the tow is generally smaller, the total effective draw ratio may range from 3.12 to 3.40. In another embodiment, where the denier per filament of the tow is generally greater, the total effective draw ratio may range from 3.5 to 4.0.

In the process herein, most of the drawing of the tow as described hereinbefore occurs in the first or initial drawing stage or zone. In particular, from 85% to 97.5% (including from 92% to 97%) of the total draw imparted to the tow will occur in the first or initial draw stage or zone. The drawing operation in the first or initial stage will generally be carried out at any temperature that the filaments have when passing from the quench zone of the melt spinning operation. This first stage drawing temperature will often range from 80 ℃ to 125 ℃.

In the present invention, steam is introduced between the feed and draw to maximize the drawing of the nylon. In one embodiment, a vapor chamber positioned between the feed and pull modules is used to allow for higher pull rates versus normal pull rates such as described herein.

From the first or initial drawing stage or zone, the partially drawn tow passes to a second annealing and drawing stage or zone where the tow is simultaneously heated and further drawn. Heating of the annealed tow is achieved to increase the crystallinity of the nylon polymer of the filaments. In this second annealing and drawing stage or zone, the filaments of the tow are subjected to an annealing temperature of from 145 ℃ to 205 ℃, for example from 165 ℃ to 205 ℃. In one embodiment, the temperature of the tow in this annealing and drawing stage may be achieved by contacting the tow with steam heated metal plates positioned between the first stage drawing and second stage drawing and annealing operations. In the present invention, annealing/furnace drying under tension helps remove excess moisture gained during steam pulling.

After the annealing and drawing stage of the process herein, the drawn and annealed tow is cooled to a temperature of less than 80 ℃, for example less than 75 ℃. Throughout the drawing, annealing, and cooling operations described herein, the tow is maintained under controlled tension and therefore does not permit relaxation.

After drawing in the presence of steam and annealing/oven drying under tension, the multifilament tow is converted into staple fibers in a conventional manner, for example using a staple cutter. Staple fibers formed from the tow will often range in length from 2 to 13cm (0.79 to 5.12 inches). For example, staple fibers may range from 2 to 12cm (0.79 to 4.72 inches), from 2 to 12.7cm (0.79 to 5.0 inches), or from 5 to 10cm may be formed. The staple fibers herein may optionally be crimped.

The high tenacity nylon staple fibers formed in accordance with the processes herein will generally be provided as a collection of fibers, for example as a fiber bundle, having a denier per fiber of from 1.0 to 3.0. When staple fibers having deniers per fiber from 1.6 to 1.8 are to be produced, a total effective draw ratio of from 3.12 to 3.40 (e.g., from 3.15 to 3.30) can be used in the processes herein to provide staple fibers having the necessary load-bearing capacity. When staple fibers having a denier per fiber of from 2.5 to 3.0 or 2.3 to 2.7 are to be prepared, a total effective draw rate of from 3.5 to 4.0 or from 3.74 to 3.90 should be used in the process herein to provide staple fibers having the necessary load-bearing capacity.

Annealing the fiber using this process and then using standard annealing rolls at 180 ℃ produced significantly higher tenacity fibers with a tenacity greater than 7.5 g/den.

In one non-limiting embodiment of the present invention, a nylon staple fiber having a fracture toughness greater than 7.5g/den is disclosed. In another non-limiting embodiment of the present invention, a nylon staple fiber having a fracture toughness greater than 7.8g/den is disclosed. In another non-limiting embodiment of the present invention, a nylon staple fiber having a fracture toughness of at least 8.0g/den is disclosed.

In one non-limiting embodiment of the present invention, a nylon staple fiber having a tenacity at 10% elongation of at least 4.0g/den is disclosed.

Fibers having the above properties can be spun into yarns at lower incorporation rates or using alternative textile systems, which significantly reduce the cost of fabric manufacture and still meet existing fabric specifications. Fibers having very high tenacity (fracture tenacity and tenacity at 7% or 10% elongation) and potentially stronger, lower cost or lighter weight fabrics that can be made from such fibers. Such fibers can be used to significantly reduce yarn spinning and finished fabric costs by allowing the use of lower nylon blending levels and/or alternative spinning systems while maintaining fabric properties. This provides value to downstream customers for competition. To achieve these properties in the fiber, the use of a steam chamber helps to maximize the draw of the nylon. The fiber obtained is tougher than any fiber produced on normal staple fiber equipment.

The ability to produce significantly higher strength fibers is extremely advantageous for completion. The higher strength nylon fibers allow the yarn weaver and fabric weaver to reduce costs while still meeting strength requirements in the finished fabric/apparel. This higher strength will place a competitive supply at a greater disadvantage in terms of cost. This cost differential may range from $0.34 to over $1.00/lb. Examples of lower cost yarns/fabrics include the lower use of nylon content in the woven yarns while still meeting yarn and fabric strength requirements, and the use of lower cost yarn weaving systems (Vortex or OES) while still meeting fabric strength requirements. These lower cost alternatives can save over $1.00 per fabric yarn with successful implementation. The ability to produce such higher strength fibers offers significant advantages that are not met by competition. Another possible advantage is to allow for the production of lower weight fabrics/apparel while still meeting existing fabric specifications. The use of new fibers in any new fabric specification, such as lighter weight fabrics, would prevent competitive fiber manufacturers from entering the market.

The nylon staple fibers provided herein are particularly useful for blending with other fibers for various types of textile applications. Some embodiments of nylon staple fibers may be blended, for example, in combination with other synthetic fibers such as rayon or polyester. Examples of blends of nylon staple fibers herein include those made with natural cellulose fibers such as cotton, flax, hemp, jute, and/or ramie. Suitable methods for intimately blending these fibers may include: batch mechanical blending of staple fibers prior to carding; bulk mechanical blending of staple fibers prior to and during carding; or at least two passes of draw frame blending of staple fibers after carding and before yarn weaving.

According to one embodiment, the high load capacity nylon staple fibers herein may be blended with cotton staple fibers and woven into a textile yarn. These yarns may be spun in a conventional manner using commonly known staple and long fiber spinning methods, including endless spinning, air jet or vortex spinning, open-end spinning, or friction spinning. When the yarn incorporates cotton, the resulting textile yarn will generally have a cotton to nylon fiber weight ratio of from 20: 80 to 80: 20, including from 40: 60 to 60: 40, and often 50: 50. As is well known in the art, nominal variations in fiber content (e.g., 52: 48) are also considered as 50: 50 blends. Textile yarns made with the high load capacity nylon staple fibers herein will often exhibit a LEA product value of at least 2800 at a 50: 50NYCO content, for example at least 3000. Alternatively, these yarns may have a fracture toughness of at least 17.5 or 18cN/tex, including at least 19cN/tex, at a 50: 50NYCO content.

In one embodiment, the textile yarns herein will be made from nylon staple fibers having a denier per filament of from 1.6 to 1.8. In another embodiment, the textile yarns herein will be made from nylon staple fibers having a denier per filament of from 2.5 to 3.0 (including from 2.3 to 2.7).

The nylon/cotton (NYCO) yarns of some embodiments may be used in a conventional manner to produce NYCO woven fabrics having desirable properties for use in, inter alia, military or other rugged use apparel. These yarns can be woven into 2x1 or 3x1 twill NYCO fabrics. Woven NYCO yarns and 3x1 twill woven fabrics including these yarns are generally described and exemplified in U.S. patent No. 4,920,000 to Green. This' 000 patent is incorporated herein by reference.

NYCO woven fabrics of course comprise warp and weft (fill) yarns. The woven fabrics of some embodiments are those fabrics in which the NYCO textile yarns herein are woven in at least one, and optionally both, of these directions. In one embodiment, the fabrics herein having particularly desirable durability and comfort will have yarns comprising nylon staple fibers herein having a denier per filament of from 1.6 to 1.8 woven in the weft (fill) yarn direction and yarns comprising nylon staple fibers herein having a denier per filament of from 2.3 to 3.0 woven in the warp direction, comprising from 2.5 to 3.0 and from 2.3 to 2.7 denier per filament.

Woven fabrics of some embodiments made using yarns comprising the high load-bearing nylon staple fibers herein can use the less nylon staple fibers of such conventional NYCO fabrics while maintaining many of the desirable properties of these conventional NYCO fabrics. As a result, these fabrics can be made relatively lightweight and low cost, while still being desirably durable. Alternatively, equal or even greater amounts of the nylon staple fibers herein can be used to make these fabrics, as compared to the nylon fiber content of conventional NYCO fabrics, where these fabrics herein provide superior durability properties.

Lightweight fabrics such as NYCO fabrics of some embodiments may have a weight of less than 220grams/m ² (6.5oz/yd ² ) Fabric weight of (a), containing less than 200grams/m ² (6.0oz/yd ² ) And less than 175 grams/m ² (5.25oz/yd ² ). Suitable durable NYCO fabrics of some embodiments will have a grab strength of 1901bs or greater in the warp direction and 801bs or greater in the weft (fill) direction. Other durable fabrics have a tear strength of 11.01bf (pounds feet) or greater in the warp direction and 9.0lbf or greater in the weft direction in an "as received" fabric.

The invention also relates to a nonwoven fabric composite comprising high tenacity fibers and cellulosic material or recycled synthetic or natural fibers. The present inventors have discovered that the inclusion of high tenacity fibers imparts additional stretch, tear, abrasion, wash durability and longevity to the nonwoven substrate, including but not limited to hydroentangling, air-weaving, needling, and other carded nonwoven techniques. In one embodiment, the high tenacity fibers used in the nonwoven fabric composite comprise load bearing nylon fibers having a fracture tenacity greater than 7.5g/den and/or a tenacity at 10% elongation greater than 4.0 g/den. However, as will be understood by those skilled in the art upon reading this disclosure, alternative high tenacity fibers may also be used, such as, but not limited to, those described in published U.S. patent applications Nos. 2011/0177737 and 2011/0177738. Additional non-limiting examples of nylon staple fibers having relatively high load-bearing toughness that can be used in these nonwoven composites are described in U.S. Pat. nos. 3,044,250;3,188,790;3,321,448;3,459,845; U.S. Pat. nos. 5,093,195 and 5,011,645. The high tenacity fibers may be combined with various cellulosic materials or recycled synthetic or natural fiber technologies, including but not limited to recycled denim. End uses for nonwoven fabric composites include, but are not limited to, industrial (felt/backing/filtration/insulation), apparel (including lining fabrics), footwear, bag/backpack hard shells, durable and semi-durable (disposable or semi-disposable) garments or PPEs, including FR (chemically treated or combined with inherent FR fiber technology), biochemical or other specialty protective apparel.

Test method

When various parameters, properties, and characteristics of the polymers, fibers, yarns, and fabrics herein are specified, it is understood that these parameters, properties, and characteristics can be determined using the following types of test procedures and equipment:

relative viscosity of Nylon Polymer

Formic acid RV of nylon materials as used herein refers to the ratio of solution to solvent viscosity measured in a capillary viscometer at 25 ℃. The solvent was formic acid containing 10% by weight of water. The solution was 8.4% by weight nylon polymer dissolved in a solvent. This test is based on ASTM standard test method D789. Formic acid RV is determined on the textile filaments before drawing or after drawing, and may be referred to as textile fiber formic acid RV.

Instron measurement on staple fibers

All Instron measurements of the staple fibers herein are made on a single staple fiber, with due care to the staple fiber grip, and the average of the measurements made over at least 10 fibers. In general, at least 3 sets of measurements (each set for 10 fibers) are averaged together to provide a value for the determined parameter.

Filament denier

Denier is the linear density of a filament expressed as the weight in grams of 9000 meters of the filament. Denier can be measured on a vibrometer from Textechno, munich, germany. Denier times (10/9) equals decitex (dtex). Denier per filament can be determined gravimetrically according to ASTM standard test method D1577. Favimat machines with vibration-based linear density measurements, such as used in vibrometers, can also be used to determine DPF or denier per filament of individual fibers and can be compared to ASTM D1577.

Fracture toughness

Fracture toughness (T) is the maximum or breaking force of a filament, expressed as force per unit cross-sectional area. Tenacity can be measured on an Instron model 1130 available from Instron of Canton, mass, and reported as grams per denier (grams per dtex). Filament tenacity at break (as well as elongation at break) can be measured according to ASTM D885.

Filament tenacity at 7% and 10% elongation

Filament tenacity (T) at 7% elongation ₇ ) Is the force applied to the filament to achieve 7% elongation divided by the filament denier. T can be determined according to ASTM D3822 ₇ . Toughness at 10% elongation can be run on a Favimat, which is comparable to ASTM D3822.

Yarn strength

The strength of the woven nylon/cotton yarns herein can be quantified via Lea product values or yarn fracture toughness. Lea product and hank break toughness are conventional indicators of the average strength of textile yarns and can be determined according to ASTM D1578. Lea product values are reported in pounds force. Fracture toughness is reported in cN/tex.

Weight of fabric

The fabric weight or basis weight of the woven fabric herein may be determined by: a fabric sample having a known area is weighed and measured at grams/m according to the procedures of the Standard test method of ASTM D3776 ² Or oz/yd ² Aspect calculates weight or basis weight.

Fabric grabbing strength

The fabric grab strength can be measured according to ASTM D5034. Grab strength measurements are reported in pounds force in the warp and fill yarn directions.

Tear Strength of Fabric- -Elmendorf

The fabric tear Strength may be measured according to ASTM D1424 entitled Standard Test Method for testing Strength of Fabrics by drop hammer Type (Elmendorf) Equipment, of the Type of Fabrics, ASTM D1424. Grab strength measurements are reported in pounds force in the warp and fill yarn directions.

Abrasion resistance of fabric-Taber

The fabric Abrasion Resistance can be determined as the Taber Abrasion Resistance as measured by ASTM D3884-01 entitled Abrasion Resistance Using A rotating Platform Double Head grinder. Results are reported as the number of cycles to failure.

Abrasion resistance of Fabric- -Flex

Fabric Abrasion Resistance can be determined as Flex Abrasion Resistance as measured by ASTM D3885 entitled Standard Test Method for Abrasion Resistance of woven Fabrics (Flexing and Abrasion Method). Results are reported as the number of cycles to failure.

The following section provides further illustration of synthetic fibers and their properties compared to fibers prepared by standard processes without steam draw assistance. These working examples are illustrative only, and are not intended to limit the scope of the present invention in any way.

Examples of the invention

Example 1: comparison of Standard T420 to high intensity T420

The properties of the fibers produced by the steam-draw assist process according to the invention were compared to those produced by standard processes on a Favimat instrument after cutting and draining. The results are shown in table 1.

TABLE 1

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Claims

1. A nylon staple fiber comprising a nylon polymer, said fiber having a tenacity at break of greater than 7.5g/den and a tenacity at 10% elongation of greater than 4.0 g/den; the fibers are prepared by a process comprising the steps of:

melt spinning a nylon polymer into filaments; uniformly quenching the filaments and forming a tow from a plurality of these quenched filaments; subjecting the tow to drawing in the presence of steam; annealing; and converting the resulting drawn and annealed tow into staple fibers; wherein subjecting the tow to drawing in the presence of steam is carried out at a temperature range of from 80 ℃ to 125 ℃.

2. The nylon staple fiber of claim 1 wherein the nylon polymer is nylon 6,6.

3. A yarn spun from the nylon staple fiber of any one of claims 1-2.

4. The yarn of claim 3 further comprising at least one companion staple fiber.

5. The yarn according to claim 4, wherein the companion staple fiber is selected from the group consisting of: cellulosic materials, modified cellulosic materials, animal fibers, fire resistant polyesters, fire resistant nylons, fire resistant rayon, fire resistant treated cellulose, meta-aramid, para-aramid, modacrylic, phenolic resins, melamine, polyvinyl chloride, antistatic fibers, PBO (polymer of 1, 4-phthalic acid and 4, 6-diamino-1, 3-benzenediol dihydrochloride), and PBI (polybenzimidazole), and combinations thereof.

6. A fabric comprising the nylon staple fiber of any one of claims 1-2 or the yarn of any one of claims 3-5.

7. The fabric of claim 6 having less than 6.0oz./yd ² The weight of (c).

8. The fabric of claim 7 meeting or exceeding less than 6.0oz./yd for weight ² The fabric of (a) establishes a military fabric strength and tear specification.

9. An article at least a portion of which comprises the nylon staple fiber of claim 1.

10. A nonwoven fabric composite comprising the nylon staple fibers and cellulosic or recycled synthetic or natural fibers of claim 1.

11. The nonwoven fabric composite of claim 10, wherein the cellulosic fibers or recycled synthetic or natural fibers comprise recycled denim.

12. A method for producing high strength or load bearing nylon fibers, the method comprising: melt spinning a nylon polymer into filaments; uniformly quenching the filaments and forming a tow from a plurality of these quenched filaments; subjecting the tow to drawing in the presence of steam; annealing; and converting the resulting drawn and annealed tow into staple fibers; wherein subjecting the tow to drawing in the presence of steam is carried out at a temperature range of from 80 ℃ to 125 ℃.

13. The method of claim 12, wherein annealing is performed under tension.

14. The method of claim 12 or 13 wherein the nylon fiber has a fracture toughness of greater than 7.5 g/den.

15. The method of claim 12 or 13 wherein the nylon fiber has a tenacity at 10% elongation of greater than 4.0 g/den.