WO2010014555A1

WO2010014555A1 - Dyeable and hydrophobic bi-component fibers comprising a polyolefin exterior surface and articles made therefrom

Info

Publication number: WO2010014555A1
Application number: PCT/US2009/051867
Authority: WO
Inventors: Jesus Nieto; Supriyo Das; Manu Rego; Paul Casey; Jerry Wang
Original assignee: The Dow Chemical Company
Priority date: 2008-07-28
Filing date: 2009-07-27
Publication date: 2010-02-04
Also published as: TW201012992A

Abstract

Of the many compositions and methods provided herein, one composition involves a bi-component fiber comprising: a first polymer component comprising an ester linkage, wherein the polymer has a melting point of less than about 265°C; and a second polymer component comprising a polyolefin wherein the second polymer component comprises at least a portion of an exterior surface of the bi-component fiber. One method provided herein involves a method of making a bi-component fiber.

Description

DYEABLE AND HYDROPHOBIC BI-COMPONENT FIBERS COMPRISING A POLYOLEFIN EXTERIOR SURFACE AND ARTICLES MADE THEREFROM

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Serial No. 61/084,141, filed July 28, 2008, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND

The present invention relates to dyeable and hydrophobic bi-component fibers comprising a polyolefin exterior surface and articles made therefrom. More particularly, in some embodiments, the present invention relates to dyeable and hydrophobic bi-component fibers comprising a polyolefin exterior surface and a polymer that comprises an ester linkage and has a melting point of less than about 265⁰C and articles made therefrom.

Fibers that are hydrophobic in nature may possess desirable properties for use in a variety of textile articles, such as in the field of active wear apparel. Polyolefin fibers (such as polypropylene fibers) are one example of a hydrophobic fiber that may be used in the manufacture of textile articles to posses desirable moisture transport and associated properties. Polyolefin fibers are manufactured fibers in which the fiber-forming substance is any long-chain synthetic polymer composed of at least 85% by weight of ethylene, propylene, or other olefin units. Polyolefin fibers can be multi- or monofilament and staple, tow, or film yarns. In some embodiments, the fibers are colorless and round in cross-section. The cross-section can be modified for different end uses. In some instances, their physical characteristics are a waxy feel and colorless. These fibers traditionally have been used mainly for ropes, twines, and utility fabrics. Polypropylene generally is the more favored polyolefin for general textile applications because of its higher melting point. While polyolefin fibers, such as polypropylene fibers, possess certain desirable properties due to their hydrophobic nature, the use of polyolefin fibers in textile articles may present a number of challenges. For instance, polypropylene fibers generally do not contain dye sites and, thus, the dyeability of polypropylene fibers is very poor. Likewise, the dyeability of yarns and textile articles made with polypropylene fibers is also very poor. Understandably, this lack of dyeability has limited the use of polyolefins in the apparel segment.

Colored polypropylene fiber is generally produced by dispersing pigments, inorganic or organic, into the polypropylene melt prior to extruding the fiber. The extrusion of inorganic pigments in a fiber is generally referred to as "solution dying" in the textile trade. In general, solution dying involves melting of the thermoplastic polyolefin to form a liquid into which inorganic pigments are added and dispersed to form a heterogeneous solution of inorganic pigments in a polymer melt. Solution-dyed polypropylene fiber generally involves addition of inorganic pigments in the range of 1-2 weight %, with deep shades needing as much as 5-10 weight % of pigment. This makes uniform distribution of pigment essential for reasonable mechanical performance, particularly for fine-denier filaments. As the desired size of the fiber decreases, this procedure for coloring polypropylene fibers presents challenges, particularly as the size of the pigment particles approaches 5% of the filament diameter. For instance, thermoplastic materials with large pigment particles are more susceptible to mechanical fracture, in that the particles may behave as notch defects enabling crack propagation under strain. This may be problematic during draw texturing of the solution-dyed fibers. Accordingly, solution- dyed fibers that require low filament diameters are rare, given the technical art needed to obtain pigment dispersions that are sufficiently small enough to not behave as notch defects in the fiber. For this reason, solution-dyed polypropylene fibers have typically found application in medium and heavy denier markets, such as carpet and upholstery. Additionally, use of inorganic pigments limits the color palette for textiles to that of available pigments, limiting the variety of colors as well as making color matching between production lots burdensome to manufacturers. As such, textile mills using solution-dyed yarns tend to have higher yarn inventory when compared to chemically dyed yarns, which can generally more easily dye or print uncolored inventory to many colors or patterns. In contrast to the above problems with solution dyeing, chemical-dye methods generally provide textile makers with more flexibility in color shade and depth, for example, by simple changes in dye recipe, formulation, and process conditions. However, as noted above, the dyeability of polypropylene is poor. For instance, polypropylene bath dyed with disperse dyes having long chains, such as anthraquinon dyes, generally lacks the light fastness and color fastness found in other chemical classes of disperse dyes having long alkyl chains. To improve the dyeability of polypropylene fibers, two different methodologies have been followed: (1) chemical modification of the polypropylene polymer or (2) blending polypropylene with a material (e.g., a polymer, additive, or natural filler fiber) that can be chemically dyed. Chemical- modification methods have included, for example, copolymerization and grafting of more polar compounds to the polypropylene polymer. However, this approach generally requires significant levels of modification to enable conventional dyeing of the modified polypropylene, which in turn changes the chemical and physical properties of the polymer to be different than unmodified polypropylene. Further, chemically modified polypropylene and polypropylene blends with other resins may not melt spin into the fine denier fibers or may undesirably lose their hydrophobic character. This is problematic given the desirable properties described above that are associated with the hydrophobic nature of polyolefins. Blending of the polypropylene with a material that can be dyed also may be problematic. For instance, color shades that may be achieved with a blending approach may be limited because blends are difficult to process. SUMMARY

The present invention relates to dyeable and hydrophobic bi-component fibers comprising a polyolefin exterior surface and articles made therefrom. More particularly, in some embodiments, the present invention relates to dyeable and hydrophobic bi-component fibers comprising a polyolefin exterior surface and a polymer that comprises an ester linkage and has a melting point of less than about 265°C and articles made therefrom.

In one embodiment, the present invention provides a bi-component fiber comprising: a first polymer component comprising an ester linkage, wherein the polymer has a melting point of less than about 265°C; and a second polymer component comprising a polyolefin wherein the second polymer component comprises at least a portion of an exterior surface of the bi- component fiber.

In another embodiment, the present invention provides a method of making a bi- component fiber comprising: co-extruding at least a first polymer component and a second polymer component to form the bi-component fiber, wherein the first polymer component comprises a polymer comprising an ester linkage, wherein the polymer has a melting point of less than about 265⁰C, wherein the first polymer component comprises polypropylene, and wherein the first polymer component comprises at least a portion of an exterior surface of the bi- component fiber.

The features and advantages of the present invention will be readily apparent to those skilled in the art. While numerous changes may be made by those skilled in the art, such changes are within the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some of the embodiments of the present invention, and should not be used to limit or define the invention.

Figure 1 illustrates cross-section examples of various sheath-core arrangements for a bi-component fiber, in accordance with embodiments of the present invention.

Figure 2 illustrates cross-section examples of various side-by-side arrangements for a bi-component fiber, in accordance with embodiments of the present invention. Figure 3 illustrates cross-section examples of various island-in-the-sea arrangements for a bi-component fiber, in accordance with embodiments of the present invention.

Figure 4 illustrates cross-section examples of various segmented-pie arrangements for a bi-component fiber, in accordance with embodiments of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

There may be many potential advantages to the bi-component fibers of the present invention, only some of which are alluded to herein. One of the many potential advantages may be that the fibers are dyeable while retaining the hydrophobic nature of the polyolefin. Accordingly, fabrics that comprise the bi-component fibers should possess the desirable properties of moisture transport and fast drying that are associated with polyolefin fibers. Another potential advantage may be that the bi-component fibers maintain dimensional stability during the high-temperature processes involved in the fabrication of fabrics, such as dyeing, heat setting, cutting, etc. Another potential advantage may be that the bi-component fibers exhibit good resistance to creep under load at room temperature. Another potential advantage may be that the bi-component fibers exhibit chlorine-water color fastness resistance. Yet another potential advantage may be that the bi-component fibers, in accordance with embodiment of the present invention, may be used successfully in apparel applications, such as active wear, intimates, swimwear, career wear, work wear (e.g., uniforms and protective clothing), medical clothing, and other technical clothing. Glossary of Certain Terms The term "bi-component fiber," as used herein, refers to a fiber comprising two or more polymeric components comprising two or more distinct regions of the fiber. Bi-component fibers are also known as conjugated or multicomponent fibers. The term "bi" in "bi-component" does not imply that only two elements are used. The structure of the bi-component fiber may be, for example, a core-sheath arrangement (in which one polymer is surrounded by another polymer), a side-by-side arrangement, a pie arrangement, an islands-in-the-sea arrangement, a crescent-moon arrangement, and the like. These different arrangements may have a variety of different cross sections. Figure 1 illustrates cross-section examples of various sheath-core arrangements for a bi-component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 1, bi-component fiber 10 has a sheath-core arrangement and comprises sheath 12 and core 14. Figure 2 illustrates cross-section examples of various side-by- side arrangements for a bi-component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 2, bi-component fiber 16 has a side-by-side arrangement and comprises first polymer side component 18 and second polymeric side component 20. Figure 3 illustrates cross-section examples of various islands-in-the-sea arrangements for a bi-component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 3, bi- component fiber 22 has an islands-in-the-sea arrangement comprises a polymer island component 24 and a polymer sea component 26. Figure 4 illustrates cross-section examples of various segmented-pie arrangements for a bi-component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 4, bi-component fiber 28 has a segment-pie arrangement and comprises first component 30 and second component 32.

The term "compatibilizer," as used herein, refers to a component that promotes the blending and/or adhesion of polymers in a fiber.

The term "dimensional stability" means that the fiber will not substantially shrink upon exposure to an elevated temperature, e.g., that a fiber will shrink less than 30% of its length when exposed to a temperature of 110⁰C for 1 minute.

The term "elastic fiber," as used herein, refers to a fiber that will recover at least about 50%, more preferably at least about 60%, and even more preferably 70%, of its stretched length after the first pull, and after the fourth to 100% strain (double the length). One suitable way to do this test is based on the International Bureau for Standardization of Manmade Fibers, BISFA 1998, chapter 7, option A. Under such a test, the fiber is placed between grips set 4 inches apart; the grips are then pulled apart at a rate of about 20 inches per minute to a distance of 8 inches and then allowed to immediately recover.

The term "fabric," as used herein, refers to a manufactured assembly of fibers and/or yarns which has substantial area in relation to its thickness and sufficient mechanical strength to give the assembly inherent cohesion. Fabrics can be knits, woven, or nonwoven. Fabrics may be used to make apparel garments, for instance.

The term "fiber," as used herein, refers to a material in which the length to diameter ratio is greater than about 10. Fiber is typically classified according to its denier, which is a unit of measurement of linear density defined as mass in grams per 9,000 meters. Filament fiber is generally defined as having a denier per fiber of greater than about 10 (11 dtex), usually greater than about 30 (33 dtex). Fine denier fiber generally refers to fiber having a denier per fiber of less than about 15. Microdenier fibers are generally thought of as multifilament fibers having a denier per filament ("dpf ') of less than about 1. "Filament fiber," or "monofilament fiber," means a single, continuous strand of material of indefinite (i.e., not predetermined) length, as opposed to a "staple fiber," which is a discontinuous strand of material of definite length (i.e., a strand which has been cut or otherwise divided into segments of a predetermined length .

The term "partially oriented yarn" or "POY," as used herein, refers to a continuous filament yarn made by extruding a synthetic polymer so that a substantial degree of molecular orientation is present in the resulting filaments, but further molecular orientation is possible, i.e., a filament yarn which is incompletely drawn.

The term "polymer," as used herein, refers to a polymeric compound prepared by polymerizing monomers of the same or a different type. The generic term "polymer" encompasses homopolymers, copolymers, terpolymers, dendrimers, interpolymers, and oligomers.

The term "polyolefin," as used herein, refers to a family of polymers (such as polyethylene and polypropylene) made from olefin monomers. Olefin monomers are made from alkenes. Olefins are also referred to as polypropylene, polyethylene, or polyolefin. The terms

"polyolefin" and "polyolefins" may be used generally herein to refer to all types of polyolefin substrates, including fibers, fabrics, and garments.

The term "textile article," as used herein, refers to fabric as well as articles, made from the fabric, including, for example, apparel and other items.

The term "textured yarn" refers to a filament or spun yarn that has been given notably more apparent volume than conventional yarns of similar fiber or filament count and linear density, often times through a texturing process. A textured yarn may be a continuous filament yarn that has been processed to introduce durable crimps, coils, loops or other fine distortions along the lengths of the filaments.

The term "yarn," as used herein, includes both a monofilament fiber as well as a number of fibers (e.g., filament fibers, monofilament fibers, staple fibers, etc.) twisted or otherwise joined together to form a continuous strand. A core-spun yarn is a yarn which has been made by twisting fibers around a core, which is another filament or a previously spun yarn, at least partially concealing the core.

All numbers disclosed herein are approximate values, regardless of whether the word "about" or "approximate" is used in connection therewith. They may vary by 1 %, 2%, 5%, or, sometimes, 10 to 20%. Whenever a numerical range with a lower limit, RL, and an upper limit, RU, is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=RL+k*(RU-RL), wherein k is a variable ranging from 1% to 100% with a 1% increment, i.e., k is 1%, 2%, 3%, 4%, 5%, 50%, 51%, 52%, . . . , 95%, 96%, 97%, 98%, 99%, or 100%. Moreover, any numerical range defined by two R numbers, as defined in the above, is also specifically disclosed.

Moreover, the indefinite article "a" or "an," as used in the claims, is defined herein to mean one or more than one of the element that it introduces.

Examples of Bi-Component Fibers Suitable for Use in Embodiments of the Present Invention

In certain embodiments, the present invention provides dyeable and hydrophobic bi- component fibers comprising a first polymer that comprises an ester linkage and has a melting point of less than about 265⁰C and a second polymer that comprises a polyolefin, wherein the second polymer comprises at least a portion of an exterior surface of the bi-component fiber. Bi-component fibers in accordance with embodiments of the present invention may have any suitable arrangement. The structure of the bi-component fibers may be, for example, a core- sheath arrangement (in which one polymer is surrounded by another polymer), a side-by-side arrangement, a pie arrangement, an islands-in-the-sea arrangement, a crescent-moon arrangement, and the like. Figure 1 illustrates cross-section examples of various sheath-core arrangements for a bi-component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 1, bi-component fiber 10 has a sheath-core arrangement and comprises sheath 12 and core 14. In certain embodiments, core 14 may comprise the first polymer and sheath 12 may comprise the second polymer. Figure 2 illustrates cross-section examples of various side-by-side arrangements for a bi-component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 2, bi-component fiber 16 has a side-by-side arrangement and comprises first polymer side component 18 and second polymeric side component 20. In certain embodiments, first polymer side component 18 may comprise the first polymer, and second polymer side component 20 may comprise the second polymer. Figure 3 illustrates cross-section examples of various islands-in-the-sea arrangements for a bi- component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 3, bi-component fiber 22 has an islands-in-the-sea arrangement and comprises a polymer island component 24 and a polymer sea component 26. In certain embodiments, polymer island component 24 may comprise the first polymer, and polymer sea component 26 may comprise the second polymer. Figure 4 illustrates cross-section examples of various segmented-pie arrangements for a bi-component fiber, in accordance with embodiments of the present invention. As illustrated in Figure 4, bi-component fiber 28 has a segment-pie arrangement and comprises first component 30 and second component 32. In certain embodiments, first component 30 may comprise the first polymer, and second component 32 may comprise the second polymer.

The bi-component fibers in accordance with embodiments of the present invention comprise a first polymer that comprises an ester linkage and has a melting point of less than about 265°C. Examples of suitable first polymers include, but are not limited to, polyethylene- terephtalate, poly-butylene-terephtalate ("PBT"), poly-tri-methyl-terephtalate, poly-tetra-methyl- terephtalate, poly-lactic acid, amorphous polyesters, polyester copolymers, and combinations thereof. For the purposes of this invention, amorphous polyesters having a melting point that cannot be determined and a glass transition temperature greater than 100⁰C, as determined by Differential Scanning Calorimetry, are considered to have a melting point of less than 265°C. In some embodiments, the first polymer may have a melting point of less than about 240°C. The internal component of the bi-component fiber may also comprise a blend of the first polymer with the polyolefins described below. In certain embodiments, the first polymer may be an internal component of the bi-component fiber. For example, as illustrated in Figure 1 , the first polymer may be included in core 14 of bi-component fiber 10 having a core-sheath arrangement. By way of further example, illustrated in Figure 3, the first polymer may be included in polymer island component 24 of bi-compohent fiber 22 in the islands-in-the-sea embodiments.

The amount of the first polymer included in the bi-component fiber varies depending upon a number of factors, including the desired application and properties. In certain embodiments, the first polymer may be present in the bi-component fiber in an amount of about 10% to about 60% by volume of the bi-component fiber (e.g., 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, etc.) and, alternatively, of about 20% to about 50% by volume of the bi- component fiber.

The bi-component fibers in accordance with embodiments of the present invention also comprise a second polymer comprising a polyolefin, wherein the second polymer comprises at a least a portion of an exterior surface of the bi-component fiber. In certain embodiments, the second polymer may at least partially surround the first polymer. For example, as illustrated in Figure 1, the second polymer may be included in sheath 14 of bi-component fiber 10 having a core-sheath arrangement. By way of further example, as illustrated in Figure 3, the second polymer may be included in the polymer sea component 26 of bi-component fiber 22 having an islands-in-the-sea arrangement. Examples of suitable polyolefϊns include polymers with ethylene, propylene, or other olefin units. Additional examples of suitable polyolefins include polyolefϊns having high- melting points (>about 135°C) including, but not limited to, polypropylene homopolymers, polypropylene copolymers, Ziegler-Natta catalyzed polypropylene, and metallocene catalyzed polypropylene homopolymers, or other high-melting point (>about 135°C) polyolefins, such as poly-4-m ethyl- 1-pentene, cyclic-olefin-copolymers, and syndiotactic polystyrene. Blends of these polyolefins are also suitable. Blends of these high-melting point polyolefins with other polyolefins having a melting point less than about 135°C are also suitable. Examples of low- melting point polyolefins include, but are not limited to, polyethylene, ethylene copolymers (polar or not), or propylene-based copolymers. Blends of these high-melting point polyolefins with amorphous polymers, such as atactic polystyrene and hydrogenated polystyrene, may also be suitable.

The amount of the second polymer included in the bi-component fiber varies depending upon a number of factors, including the desired application and properties. In certain embodiments, the second polymer may be present in the bi-component fiber in an amount of about 40% to about 90% by volume of the bi-component fiber (e.g., 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc.) and, alternatively, of about 50% to about 80% by volume of the bi- component fiber. In certain embodiments, the second polymer may comprise a substantial portion of a sheath of a bi-component fiber having a core-sheath arrangement. The ratio of the second polymer to the first polymer in the bi-component fiber varies depending upon a number of factors, including the desired application and properties. In certain embodiments, the second-polymer-to-first-polymer volume ratio is in a range of about 1 :10 to about 95:5, alternatively, a range of about 60:40 to about 90:10, and alternatively, a range of about 40:60 to about 80:20. In certain embodiments, a volume ratio in a range of about 65:35 to about 80:20 may be used in a core-sheath arrangement with a sheath comprising the polyolefin as the second polymer and a core comprising PBT as the first polymer. In certain embodiments, a volume ratio in a range of about 40:60 to about 80:20 may be used in a core-sheath arrangement wherein a third polymeric component is blended in either the core and/or the sheath.

In addition to the polyolefin and the polymer comprising the ester linkage, the bi- component fiber may comprise an additional polymeric component, in certain embodiments. For example, the additional component may be blended with either the first or second polymer. Alternatively, for example, the additional component may comprise a distinct region of the fiber from the first and second polymers. For example, the bi-component fiber may comprise: a polyolefin comprising at least a portion of an exterior surface of the fiber; a middle layer comprising a polymer that comprises an ester linkage and having a melting point of less than about 265°C; and an inner core comprising a polyolefϊn. The polyolefin in the inner core may be, for example, the polyolefϊns described above suitable for use as the polyolefin exterior surface. Examples of suitable polymeric components that may be blended with, or be a distinct component from the first and second polymers include, but are not limited to copolymers of propylene and ethylene with a weight fraction of ethylene between 3 and 20%, or copolymers of ethylene and one or more alpha-olefms with a total alpha-olefin content of more than 5% by weight, or copolymers of propylene or ethylene with polar comonomers like acrylic acid and its metal salts, or vinyl acetate, methyl-metacrylate and the like. Additives may be included in the bi-components fibers if desired for a particular application, provided that any such additive does not undesirably impact the purposes of the present invention. For example, additives for resistance to oxidation and UV exposure, for static dissipation, for odor control, for fiber coloring, spin finish and other aids may be used. In certain embodiments, the fibers could also contain dispersed particles for purposes, including, but not limited to, dyeability improvement. These particles could be, for example, polymeric, clays, metal hydroxides, or the like.

In certain embodiments, compatibilizers may be also be used, for example, to enhance the intimate blending and/or adhesion of the polymers in the bi-component fiber. Examples of suitable compatibilizers include, but are not limited to, a homogeneously branched ethylene polymer, such as a homogeneously branched, substantially ethyl ene-polymer grafted with a carbonyl-containing compound, e.g., maleic anhydride, that is reacted with a diamine. Compatibilizers generally should facilitate the extrusion of the core component into the sheath component, for example. Those of ordinary skill in the art, with the benefit of this disclosure, should be able to select appropriate type and amounts of a compatibilizer to use for a particular application.

The fibers may be of any suitable size and cross-sectional shape depending upon, for example, the desired application. For many applications, approximately round cross-section is desirable due to its reduced friction. However, other shapes, such as trilobal shape, or a flat (i.e., "ribbon"-like) shape can also be employed. In certain embodiments, suitable fibers may have a dpf of at least about 0.5 to about 50 dpf. In certain embodiments, the bi-component fiber may be a fine denier fiber having a dpf of less than about 15. By way of example, the bi-component fiber may have a dpf of about 0.5 to about 15 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, etc.) and, alternatively, about 0.7 to about 3 dpf. In certain embodiments, the bi-component fibers maybe spun into yarn having a total denier of about 20 to about 1,500 and alternatively, of about 30 to about 300.

The density of the bi-component fibers may be calculated from the volume ratios and nominal density of the component. In certain embodiments, the bi-component fibers may have a density of less than about 1.15 grams per cubic centimeter, for example, about 1.08 grams per cubic centimeter to about 1.07 grams per cubic centimeter. By way of further example, the bi- component fibers may have a density of less than about 1.1 grams per cubic centimeter, for example, about 0.9 grams per cubic centimeter to about 1.0 grams per cubic centimeter.

Depending on the application, bi-component fibers in accordance with the present invention may take the form of staple fibers, monofilament fibers or multifilament fibers. In certain embodiments, a number of bi-component fibers may be fibers twisted or otherwise jointed together to form a continuous strand. In certain embodiments, bi-component fibers in accordance with embodiments of the present invention may be used in a core-spun yarn. For example, a bi-component fiber in accordance with embodiments of the present invention may be utilized as the core in a core-spun yarn. In certain embodiments, monofilament or multifilament fibers that comprise a bi-component fiber in accordance with embodiments of the present invention may be utilized in a textured yarn, a draw-textured yarn, a ring-spun yarn, a spun- drawn yarn, or a partially oriented yarn. Draw-texturing may be applied, for example, to a partially oriented yarn. In certain embodiments, a monofilament or multifilament fiber that comprises a bi- component fiber in accordance with embodiments of the present invention may be textured. The bi-component fibers may be textured, for example, to provide a desirable hand feel to fabrics fabricated with such fibers. Texturing may involve, for example, air-jet texturing, a false-twist texturing process, a twist/detwist process, a twist-separation process, a stuffer-box crimping process, a BCF-jet process, a knit-de-knit process, an edge-crimping process, or a gear-crimping process. One advantage of monofilament or multifilament fibers that comprise a bi-component fiber in accordance with embodiments of the present invention is that the fibers should exhibit high crimp stability, in that the crimp imparted during texturing is stable, resulting in long-term maintenance of a desirable feel to fabrics fabricated with such fibers Examples of Fabrics Suitable for Use in Embodiments of the Present Invention

In certain embodiments, the bi-component fibers in accordance with embodiments of the present invention may be incorporated into textile articles. As previously mentioned, textile articles include fabrics as well as articles (e.g., apparel) made from the fabric. Examples of suitable textile articles include, but are not limited to, active wear, intimates, swimwear, career wear, work wear {e.g., uniforms and protective clothing), medical clothing, and other technical clothing. Shrinkage of the fabrics knitted from the yarns prepared in accordance with embodiments of the present invention may exhibit a shrinkage level and dimensional stability at high temperatures equivalent to the standards in the industry for fabrics made with pure PET or PP yarns.

Example fabrics may comprise a dyeable and hydrophobic bi-component fiber comprising a first polymer component and a second polymer component. As discussed above, in accordance with embodiments of the present invention, the first polymer component comprises an ester linkage and have a melting point of less than about 265°C, and the second polymer component comprises a polyolefm, wherein the second polymer component comprises at a least a portion of an exterior surface of the bi-component fiber. Examples of suitable fabrics include knit, woven, or nonwoven fabrics.

The amount of the bi-component fiber present in the fabric depends on a variety of factors, including the particular fiber, the application, and the desired properties. In certain embodiments, the bi-components fibers may be present in a fabric in an amount up to about 100% by weight. By way of example, the bi-components fibers may be present in a fabric in an amount of about 50% to about 100% by weight. By way of further example, the bi-component fibers may be present in a fabric in an amount of about 70% to about 100% by weight.

In some embodiments, the fabrics also may comprise other fibers, including elastic fibers to provide stretch and elastic recovery properties. Examples of suitable elastic fibers include, but are not limited to, rubber filaments, elastoesters, lastol, spandex, LYCRA fibers (easily available from many global sources), and DOW XLA fibers (available from the Dow Chemical Company). However, it should be noted that combination of the bi-component fiber with spandex may have undesirable properties, such as undesirable hand feel, dimensional stability, uncomfortable due to powerful stretch at lighter weight. Accordingly, combination of the bi- component fiber with the DOW XLA fiber article may be preferred. Additional fibers that may be incorporated into the fabrics include, but are not limited to natural and synthetic fibers, such as nylon, cotton, wool, silk, and the like.

Examples of Dyeing Techniques Suitable for Use in Embodiments of the Present Invention

The fabrics and/or bi-component fibers in accordance with embodiments of the present invention may be dyed using any suitable dyeing process. Examples of suitable dyeing processing include, but are not limited to, disperse dyeing, and acid dyeing. One advantage of fabrics that comprise a bi-component fiber in accordance with embodiments of the present invention is that the fabrics and/or fibers are dyeable even though the fabrics and/or fibers comprise a polyolefϊn. The dyed fabric may be characterized, for example, as having a color strength of greater than about 600, alternatively, greater than about 650, alternatively, greater than about 700, and, alternatively, greater than about 750, as measured with a spectrum photometer.

To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the invention. Ratios, parts, and percentages are by volume unless otherwise stated

EXAMPLES

Fiber/Yarn Preparation: Bi-component fibers having a core-sheath arrangement are made compπsing a polypropylene sheath and a polyester-based core. Bi-component fibers are made with both a PBT-based core and a PET-based core. The bi-component fibers with the PET-based core were made for comparative purposes The resms used to prepare the fibers are described in Table 1 below.

Table 1. Resin Details

Prior to melt spinning, a polyester resm is dπed at a temperature of about 110^cC for 6 hours in a desiccating dryer using -40⁰C dew point air. The fibers are then prepared using a bi- component fiber line from Hills, Inc. in Freeport, Texas, and Taiwan.

Seventy-two filament fibers are produced for these examples. A 144-hole spinneret is used for producing the filament fibers Half of the holes are blocked, and only 72 ends are spun. The round-melt capillary used has a diameter of 0.5 mm and an L/D of 2. The spinneret is mounted in a spin pack equipped with 40-micron filtration application of Goulston Lurol 7521 applied as a 15% water solution at levels of 0.5 weight % to provide lubrication to the partially oriented yarn that is produced. The A-side of this line is equipped with volumetric melt pump delivering 3.0 cubic centimeters of melt per revolution and is charged with polypropylene. The B-side of this line is equipped with a melt pump that supplies 0.65 cubic centimeters of polymer melt per revolution and is charged with PET or PBT. Three different core-sheath composition bi-component yarns are produced, each with a total denier of 147. Given the high temperature of melt extrusion, a nominal polypropylene melt density of 0.75 grams per cubic centimeter ("g/cc") and a nominal polyester melt density of 1.17 g/cc are used for melt pump throughput calculations. The different volume sheath/core ratios are obtained by adjusting the revolutions per minute of the respective melt pumps. An example of spinning temperature settings is as follows: (i) for polypropylene, 180⁰C in zone 1, 200⁰C in zone 2, 210 °C in zone 3 and 220⁰C in zone 4; and (ii) for polyester, 280⁰C for zone 1, 290°C for zone 2, 295⁰C for zone 3 and 300⁰C for zone 4. Both polymer melts enter a spin beam with a common temperature set point of about 290⁰C measured after the respective melt pumps. Spinning temperatures are modified as necessary to ensure a stable process as different bi-component fibers are produced. Fiber leaving the spinneret is cooled using a three-zone quench system with all zones running with 18°C air and quench flow rates of 0.4 meters per second. The fiber is taken up on a pair of denier rolls at a rate of 2,800 meters per minute at ambient temperature. The surface of the take-up roles are painted cast aluminum. The fibers are wound to produce small, 200-gram packages using a Barmag SW4 winder running at 2,772 meters per minute (relax 1%), with a helix angle of 10, and a ribbon break frequency of 9 and a ribbon break amplitude of 8.

The partially oriented yards comprising the bi-component fibers are described in more detail Table 2 below. Comparative Sample 1 listed in Table 2 below is not prepared using the above-described procedure, but rather is a commercially available PET yarn.

Table 2. Partially Oriented Yarn Details

For the table above, density is calculated by first obtaining the weight fractions from the volume fractions and the density of the pure materials, taking nominal density values as follows:

Homopolymer polypropylene: 0.900g/cm³; PET: 1.370 g/cm³; PBT: 1.270 g/cm³; metallocene copolymer of propylene and ethylene: 0.867 g/cm³. Second, the density of the fiber is calculated from the following formula: l /[QbfJ = Xcore/Qcore + Xsheath/Qsheath wherein d_bf is the density of the bicomponent fiber, d_core is the density of the core, d_Sheath is the density of the sheath component, X_Sheath is the weight fraction of the sheath, and X_core is the weight fraction of the core.

Texturing of Example Yarns: Certain of the partially oriented yarns from Table 2 are then subjected to texturing, which is done on MPS-V texturing machine from Oerlikon Barmag Zweigniederlassung der Oerlikon Textile GmbH & Co. KG and is based on the false-twist texturing principle. The MPS-V texturing machine, like any traditional texturing machine, has a heating zone, the cooling zone, twist inserter, and a take-up system. The heating is done with newly developed contact electrical heating which is specially suited for low melting point thermoplastic polymer such as polypropylene.

The process conditions during texturing are as follows:

Draw ratio: 1.37;

Primary heater temperature: 120⁰C;

Twist insertion or D/Y ratio: 1.78;

Second heater temperature and over feed: No; and

Type of disc: 4 polyurethane disc, diameter of 52 mm, and 9 mm thick. Crimp Testing of Example Yarns: Certain of the textured yarns from Table 2 are then subjected to crimp testing in accordance with German industrial standard DIN 53 840. This test procedure has been designed for yarns up to 500 dtex. It uses yarn hanks with an overall count of about 2500 dtex, the hanks being subjected to various loads during testing and their length measured at each stage. Crimp contraction, crimp modulus and crimp stability are then

calculated from the measured lengths.

The results of the crimp testing are set forth in Table 3 below. The most relevant parameter is the crimp stability, B%, which gives an indication of how permanent is the crimp and bulk of the textured yarn. As can be seen from Table 3 below, a more permanent crimp is obtained for Samples 6 and 7 as compared to comparative Sample 5.

Table 3. Crimp Testing Results

Fabric Preparation: The textured or non-textured yarns from Table 2 are then knitted in a sock knitting machine into fabric labeled as Comparative Fabric 1 to Fabric 7 in a single- jersey structure, optionally with an elastic fiber like the DOW XLA fiber. The knitting machine has a gauge of 20 G, and the fabric is knitted with a stitch length of 3 millimeters per needle. The resulting fabric is washed and dried, in accordance with AATC Test Method 61- 1996 2A Wash.

Table 4. Fabric Details

Fabric Dyeing: Fabric samples fabricated from the partially oriented yarns are then dyed. Prior to dyeing, scouring is performed on the fabric. The fabric samples are scoured at 90⁰C with 0.3 milliliters per liter of sodium hydroxide for 20 minutes to remove the oil and dirt. Both the fiber and the fabric are separately scoured. Then, the samples are given a hot wash at 100⁰C for 20 minutes followed by a cold wash at room temperature for 10 minutes.

The dyeing is performed on a lab-scale Rotadyer from Atlas. The Rotadyer includes small steel vessels with a maximum capacity of 250 milliliters, each with airtight lids. The vessels are filled with the required dyeing liquor and specified auxiliaries, and the lid is closed and immersed in an oil bath and rotated. The oil bath is heated with heating coil and oil bath heats the vessel containing the dye liquor. The machine is programmed to control the heating rate, the dwell time, and the cooling time. The machine is cooled by a continuous supply of cold water. A disperse dyeing process is utilized. For disperse dyeing, the dyeing phases involves utilizing a dyeing liquor. The dyeing liquor includes 2% by weight of Foron dyestuff (from Clariant), 1 milliliter per liter of Lyocol^™ RDN (dispersing agent from Clariant), 2% by weight of Eganal^™ PS Liquid (leveling agent from Clariant International Ltd.) and 2% by weight of ammonium sulphate in distilled water. The dyeing step involves placing the fabric sample in the dyeing liquor at a sample-to-liquor ratio of 1 :30 and heated to 13O⁰C at a rate of 3⁰C per minute. The dyeing temperature is maintained at 130⁰C for 90 minutes, followed by cooling to 70⁰C at a rate of 4°C per minute. In order to remove the unfixed dye molecules, reduction clearing is done. The reduction clearing composition includes 2 grams per liter of sodium hydrosulphite and 1 gram per liter of sodium hydroxide. The sample is immersed in this solution at a sample-to- liquor ratio of 1:30. The system is heated in this bath to 7O⁰C at rate of 4°C per minute and maintained at this temperature for 20 minutes. The reduction clearing step is done two times. After the reduction clearing, the sample is subjected to a hot wash for 20 minutes at 80⁰C with a sample-to-liquor ratio of 1 :30, followed by a cold wash of 10 minutes at room temperature. Colorfastness/Staining Analysis: To evaluate the colorfastness to laundering of the dyed fabric samples, the dyed fabrics are subjected to accelerated laundering tests in accordance with AATCC Test Method 61-1996. Option 2A of the testing method is used, which is designed for fabrics that are expected to withstand repeated low-temperature machine washings. In this test, dyed fabric samples are washed under specified conditions to replicate five home washings. The samples are then evaluated for color change, staining, and abrasion.

For this test, dyed fabric samples are tested at 49°C (+/- 2⁰C) inside a canister containing 150 millimeters of a water composition with 0.15% AATCC Standard Reference Detergent of total volume of the water composition. In order to simulate the abrasive action as during hand or mechanical wash, 50 steel balls, each 6 millimeters in diameter, are placed inside the canister. The process is continued for 45 minutes with a multi-fiber witness fabric after which the samples are washed with distilled water and dried. The dyed sample is compared to the original unwashed sample to measure the change of color due to washing and quantitatively measured by the gray scale for color change, and reported as color fastness. The staining of the dye on different components of the multi-fiber witness fabric is determined by gray scale for staining (according to the standard).

Table 5 below provides the results from the colorfastness/staining analysis. Table 5. Colorfastness/Staining Analysis

As shown m the table above, color fastness of Fabπcs 4 and 6 is comparable to the standard fabπcs used in the industry

Color-Intensity Measurement: To evaluate color intensity, the fabπc samples are dyed together with a standard fiber/fabπc whose color intensity is known The standard fabπc is made from multi-filament polyester in the case of disperse dyeing These standaid fabπcs are commercial circular knit samples provided by a mill, made with multifilament fibers with a denier per fiber of about 1 5. After the dyeing is finished, the intensity of the color of the control fiber is compared with the samples to estimate visually the color intensity in companson to the control samples The samples are then qualitatively assessed according to depth of shade It is to be noted that this is a subjective analysis that is meant to provide only a companson of better or worse color intensity.

Table 6 below provides the results from the color-intensity measurements Table 6. Color-Intensity Measurement

Color-Spectrophotometer Analysis: To further evaluate dyeability of the fabric samples, color shade and intensity of the dyed fabric samples, the fabric samples are placed in a color spectrophotometer to obtain a K/S value and L, b, and a parameters.

Table 7 below provides the results of the color-spectrophotometer analysis. Table 7. Color-Spectrophotometer Analysis

Accordingly, based on the above color-spectophotometer analysis, the color strength of the Fabrics Samples 2-4 is comparable to the standards of the industry.

Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein Furthermore, no limitations are intended to the details of construction or design herein shown, other than as descπbed in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified, and all such vaπations are considered within the scope and spiπt of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.

Claims

CLAIMSWhat is claimed is:

1. A bi-component fiber comprising: a first polymer component comprising an ester linkage, wherein the polymer has a melting point of less than about 265°C; and a second polymer component comprising a polyolefin wherein the second polymer component comprises at least a portion of an exterior surface of the bi-component fiber.

2. The bi-component fiber of claim 1 wherein the bi-component fiber is characterized by a core-sheath arrangement, wherein the core comprises the first polymer component, and the sheath comprises the second polymer component.

3. The bi-component fiber of claim 1 , wherein the first polymer component comprises at least one polymer selected from the group consisting of poly-butylene-terephtalate, poly-tri-methyl-terephtalate, poly-tetra-methyl-terephtalate, poly-lactic acid, and an amorphous polyesters.

4. The bi-component fiber of claim 1 wherein the first polymer component comprises poly-butylene-terephtalate.

5. The bi-component fiber of claim 1 wherein the polyolefin has a melting point of greater than about 135°C.

6. The bi-component fiber of claim 1 wherein the second polymer component comprises polypropylene.

7. The bi-component fiber of claim 1 wherein the first polymer component is present in an amount of about 10% to about 50% by volume of the bi-component fiber, and wherein the second polymer is present in an amount of about 50% to about 90% by volume of the bi-component fiber.

8. The bi-component fiber of claim 1 wherein an additional polymeric component is blended with the first polymer component and/or the second polymer component.

9. The bi-component fiber of claim 1 wherein an additional polymeric component is present in a distinct region of the bi-component fiber.

10. The bi-component fiber of claim 1 wherein the bi-component fiber has a denier per filament of less than about 15.

11. The bi-component fiber of claim 1 wherein the bi-component fiber has a denier per filament of about 0.7 to about 3.

12. The bi-component fiber of claim 1 wherein the bi-component fiber has a density of less than about 1.15 grams per cubic centimeter.

13. A yarn comprising the bi-component fiber of claim 1.

14. The yarn of claim 13 wherein the yarn has a total denier of about 30 to about 300.

15. The yarn of claim 13 wherein the yarn is a draw-textured yarn.

16. A woven or knitted fabric comprising the bi-component fiber of claim 1.

17. A textile article comprising the bi-component fiber of claim 1.

18. The textile article of claim 17 comprising an elastic fiber.

19. A method of making a bi-component fiber comprising: co-extruding at least a first polymer component and a second polymer component to form the bi-component fiber, wherein the first polymer component comprises a polymer comprising an ester linkage, wherein the polymer has a melting point of less than about 265°C, wherein the first polymer component comprises polypropylene, and wherein the first polymer component comprises at least a portion of an exterior surface of the bi-component fiber.

20. The method of claim 19 wherein the bi-component fiber is characterized by a core-sheath arrangement, wherein the core comprises the first polymer component, and the sheath comprises the second polymer component.

21. The method of claim 19 wherein the first polymer component comprises poly-butylene-terephtalate, and wherein the second polymer component polypropylene.

22. The method of claim 19 wherein an additional polymeric component is blended with the first polymer component and/or the second polymer component.

23. The method of claim 19 wherein the bi-component fiber has a denier per filament of about 0.7 to about 3.

24. The method of claim 19 wherein the bi-component fiber has a density of less than about 1.15 grams per cubic centimeter.