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  Elastomeric multicomponent fibers, nonwoven webs and nonwoven fabricsUSPTO Application #: 20060084339Title: Elastomeric multicomponent fibers, nonwoven webs and nonwoven fabrics Abstract: A bonded web of multi-component strands that include a first polymeric component and a second polymeric component is capable of overcoming a number of problems associated with nonwoven webs including both stickiness and blocking. The first polymeric component and second polymeric component are arranged in substantially distinct zones extending longitudinally along at least a portion of a length of the strands which make up the web with the second component containing a zone constituting at least a portion of the peripheral surface of the strand. The first polymeric component also has an elasticity which is greater than that of the second polymer component. A process producing elastomeric spunbonded nonwoven fabrics which utilizes the activation by incremental stretching of the strands is also provided. (end of abstract) Agent: Robert M. O'keefe O'keefe, Egan & Peterman, LLP - Austin, TX, US Inventors: Steven P. Webb, Jared A. Austin, Stephen R. Sharp USPTO Applicaton #: 20060084339 - Class: 442329000 (USPTO) Related Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Nonwoven Fabric (i.e., Nonwoven Strand Or Fiber Material), Nonwoven Fabric Has An Elastic Quality, Nonwoven Fabric Comprises An Elastic Strand Or Fiber Material The Patent Description & Claims data below is from USPTO Patent Application 20060084339. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims priority to provisional application Ser. No. 60/420,949, filed Oct. 24, 2002, incorporated herein by reference. FIELD OF THE INVENTION [0002] The invention relates to nonwoven fabrics produced from multi-component strands, processes for producing nonwoven webs and products using the nonwoven webs. The nonwoven webs of the invention can be-produced from multi-component strands including at least two components, a first, elastic polymeric component and a second, extensible but less elastic polymeric component. BACKGROUND OF THE INVENTION [0003] In recent years there has been a dramatic growth in the use of nonwovens, particularly elastomeric nonwovens, in disposable hygiene products. For example, elastic nonwoven fabrics have been incorporated into bandaging materials, garments, diapers, support clothing, and feminine hygiene products. The incorporation of elastomeric components into these products provides improved fit, comfort and leakage control. [0004] However, many laminates composed of an elastic film bonded to one or two non-elastic nonwoven layer or layers must be "activated" to provide suitable tensile and recovery properties. In particular, many of these elastic film/non-elastic nonwoven laminates must be subjected to an initial drawing or stretching process to develop their ultimate properties. Traditional stretching equipment associated with wide web products include conventional draw rolls and tenter frames. Unfortunately, draw rolls can impart non-uniform stretching when used in conjunction with elastomeric fabrics. Tenter frames are expensive and require a significant amount of space within manufacturing facilities. [0005] The present inventors have recognized that there remains a need in the art for elastomeric nonwoven fabrics exhibiting improved drape and which further may be produced economically. SUMMARY OF THE INVENTION [0006] The present invention is based, at least in part, on the surprising discovery that bonded webs made from a plurality of strands comprising at least two polymeric components where one component is elastic and another component is less elastic but extensible wherein the bonded nonwoven web has been subjected to incremental stretching, can overcome a variety of problems in the field. [0007] The present invention is generally directed to methods for producing elastic nonwoven webs and fabrics that may include melt spinning a plurality of multicomponent strands having first and second polymer components longitudinally coextensive along the length of the filament. The first component is formed from an elastomeric polymer and the second component is formed from a non-elastomeric polymer. The melt spun strands are formed into a nonwoven web which is subsequently bonded and incrementally stretched in at least one direction to activate the elastic properties of the nonwoven web. Incremental stretching is accomplished by supporting a web at closely spaced apart locations and then stretching the unsupported segments of the web between these closely spaced apart locations. This is most easily accomplished by passing the web through a nip formed between a pair of meshing corrugated rolls, which have an axis of rotation perpendicular to the direction of web travel. Incremental stretching apparatuses designed for machine direction, cross direction, and diagonal stretching are described in U.S. Pat. No. 5,861,074, incorporated herein by reference. The incremental stretching step may include stretching the web so that portions of the multicomponent strands are stretch-activated and become elastic, while other portions of the strands are not stretch activated and are substantially less elastic. In advantageous embodiments, the web is incrementally stretched so that substantially all of the multicomponent strands are uniformly stretch-activated and become elastic. [0008] In further beneficial aspects, the incremental stretching step includes incrementally stretching the web in both the machine direction and the cross-machine direction. In one embodiment, the incremental stretching may be accomplished by directing the web through at least one pair of interdigitating stretching rollers at a temperature less than about 35.degree. C. In one aspect of such embodiments, the interdigitating stretching rollers give rise to narrow, spaced apart longitudinally extending stretch-activated elastic zones within the fabric, separated by intervening longitudinally extending non-activated zones that are substantially less elastic. In beneficial aspects of the invention, the incremental stretching may be accomplished by directing an incrementally stretched web through a second pair of interdigitating stretching rollers at a temperature less than about 35.degree. C. to stretch activate a second portion of the non-activated strands within the web. In further advantageous aspects, mechanical incremental stretching may be performed in conjunction with an impinging fluid directed onto the surface of the web. Advantageously, the impinging fluid is air or water. [0009] With respect to the multicomponent strands, the first and second components can be derived from any of a wide variety of polymers. In one embodiment of the invention, the first polymer component is formed from an elastomeric polyurethane, elastomeric styrene block copolymer, or an elastomeric polyolefin and the second polymer component is formed from a polyolefin that is less elastic than the first component. [0010] Aspects of the invention are directed to the production of strands having a sheath/core configuration in which the step of incremental stretching forms corrugations within both the sheath and the core of the strands. Individual strands are lengthy, generally extruded continuously and are infinite in length. The strands are not broken into smaller lengths after the activation by incremental stretching; rather, the strands have generally been formed in structures that have a corrugated, bellows-like configuration throughout substantially the entire length of the nonwoven web that has been subjected to the incremental stretching. This corrugated appearance and structure can be observed using standard microscopy techniques, and are difficult if not impossible to detect using the unaided eye. The thickness of the individual folds in the incrementally stretched and corrugated portions of the nonwoven web are essentially the width of the sheath component of the strand, and as such are typically on the order of 0.1 to 2 microns in thickness. Alternative aspects of the invention involve melt spinning strands having either segmented pie-wedge or tipped multilobal configurations and using incremental stretching to split the components apart from one another or form corrugations, serpentines, or other forms of texture down the length of the strands. [0011] The present invention further includes elastic nonwoven fabrics produced by the methods of the invention, as well as multicomponent elastic fibers. In one advantageous embodiment, multicomponent elastomeric fibers exhibiting an overall helical configuration (similar to the appearance of a candy cane or barber pole) are provided. In beneficial aspects of these embodiments, the helical fibers may further be split to produce helically wrapped fibers of the non-elastomeric components around one or more elastomeric components. [0012] In one broad respect, this invention is a method for producing an elastic nonwoven fabric, comprising: incrementally stretching a nonwoven web in at least one direction to activate the elastic properties of the nonwoven web and to form the elastic nonwoven fabric, wherein the nonwoven web comprises a plurality of multicomponent strands having first and second polymer components longitudinally coextensive along the length of the strands, said first component comprising an elastomeric polymer, and said second polymer component comprising a polymer less elastic than the first polymer component. In one embodiment, the nonwoven web can be formed by: melt spinning a plurality of multicomponent strands having first and second polymer components longitudinally coextensive along the length of the strands, said first component comprising an elastomeric polymer, and said second polymer component comprising a non-elastomeric polymer; forming the multicomponent strands into a nonwoven web; and bonding or intertwining the strands to form a coherent bonded nonwoven web. In one embodiment, the incremental stretching of the web may comprise stretching the fabric so that portions of the multicomponent strands are stretch-activated and become elastic, while other portions of the strands are not stretch-activated and are substantially less elastic. In one embodiment, the incrementally stretching the web may comprises stretching the fabric so that substantially all of the multicomponent strands are stretch-activated and become elastic. In one embodiment, the incrementally stretching the web comprises incrementally stretching the web in both the machine direction and in the cross-machine direction. In one embodiment, the incrementally stretching the web comprises directing the web through at least one pair of interdigitating stretching rollers at a temperature less than 35 degrees Centigrade. In one embodiment, directing the web through interdigitating stretching rollers includes forming narrow, spaced apart longitudinally extending stretch-activated elastic zones in the fabric, separated by intervening longitudinally extending non-activated zones that are substantially less elastic. In one embodiment, the incrementally stretching the web comprises directing the web through a first pair of interdigitating stretching rollers to stretch activate at a first portion of the web and subsequently directing the web through a second pair of interdigitating stretching rollers to stretch activate a second portion of the non-activated strands within the web. In one embodiment, the incrementally stretching the web further comprises impinging fluid onto the surface of the web. In one embodiment, the fluid is either water or air. In one embodiment, the first polymer component comprises an elastomeric polyurethane, and the second polymer component comprises a polyolefin that is less elastic than the elastomeric polyurethane, and in another embodiment the second polymer component is polypropylene, polyethylene, or a blend thereof. In one embodiment, the melt spinning comprises arranging the first and second polymer components in the strand cross-section to form a sheath/core configuration, and wherein the step of incrementally stretching includes forming corrugations in both the sheath and the core of the strands. In one embodiment, the melt spinning comprises arranging the first and second polymer components in the strand cross-section to form the polymer components in a segmented pie configuration, and wherein the step of incrementally stretching includes splitting the first and second polymer components apart from one another. In one embodiment, the melt spinning comprises arranging the first and second polymer components in the strand cross-section to form polymer components in a tipped multilobal configuration, and wherein the step of incrementally stretching includes either splitting the first and second polymer components apart from one another or forming crimps or forming serpentines or other non-linear, random textures down the length of the strand. In one embodiment, at least a portion of the multicomponent strands has a sheath/core configuration. In one embodiment, at least a portion of the multicomponent strands have a trilobal or tipped trilobal configuration. Any combination of these embodiments or other embodiments described herein can be employed in the practice of this invention. [0013] In another broad respect, this invention is an elastic nonwoven fabric comprising: a plurality of multicomponent strands randomly arranged to form a nonwoven web; a multiplicity of bond sites or substantially randomly intertwined strands bonding the strands together to form a coherent bonded nonwoven web; the strands of the web including first and second polymer components, the first polymer component comprising an elastomeric polymer, and the second polymer component comprising a non-elastomeric polymer; and wherein first portions of the multicomponent strands of the web are stretch-activated and elastic. In one embodiment, other portions of the multicomponent strands of the web are not stretch-activated and less elastic than the first portions. In one embodiment, the fabric includes narrow, spaced apart-longitudinally extending stretch-activated elastic zones in the fabric, separated by intervening longitudinally extending non-activated, substantially less elastic zones. In one embodiment, the first polymer component comprises an elastomeric polyurethane, and the second polymer component comprises a polyolefin. In one embodiment, the second polymer component is polypropylene, polyethylene, or blend thereof. In one embodiment, the first and second polymer components are arranged in a sheath core configuration, and the stretch-activated portions of the stands have corrugations in the sheath and in the core of the strands. In one embodiment, the first and second polymer components are arranged in a segmented pie configuration, and the stretch-activated portions of the strands have either the first and second polymer components split apart from one another or the components both exhibit crimps down their length. In one embodiment, the first and second polymer components are arranged in a tipped multilobal configuration, and the stretch-activated portions of the strands have either the first and second polymer components split apart from one another or the components both exhibit crimps down their length. [0014] In another broad respect, this invention is a multicomponent fiber comprising an elastomeric component and a component having less elasticity than the elastomeric component, said multicomponent fiber exhibiting an overall helical configuration which includes the components having less elasticity bulked around the elastomeric component. In one embodiment, the fiber has been subjected to incremental stretching. [0015] In another broad respect, this invention is a garment comprising a plurality of layers, wherein at least one of said layers comprises the nonwoven fabric described above. The garment can be, for example, a training pant, a diaper, an absorbent underpant, underwear, an incontinence product, a feminine hygiene item, an industrial apparel, a coverall, a head covering, a pant, a shirt, a glove, a sock, wipes, a surgical gown, wound dressings, bandages, a surgical drape, a face mask, a surgical cap, a surgical hood, a shoe covering, or a boot slipper. [0016] In another broad respect, this invention is an incrementally stretch activated nonwoven web, made from the multicomponent strands. [0017] The fibers and articles of the present invention have utility in a variety of applications. Suitable applications include, for example, but are not limited to, disposable personal hygiene products (e.g. training pants, diapers, absorbent underpants, incontinence products, feminine hygiene items and the like); disposable garments (e.g. industrial apparel, coveralls, head coverings, underpants, pants, shirts, gloves, socks and the like); infection control/clean room products (e.g. surgical gowns and drapes, face masks, head coverings, surgical caps and hood, shoe coverings, boot slippers, wound dressings, bandages, sterilization wraps, wipers, lab coats, coverall, pants, aprons, jackets), and durable and semi-durable applications such as bedding items and sheets, furniture dust covers, apparel interliners, car covers, and sports or general wear apparel. BRIEF DESCRIPTION OF THE DRAWINGS [0018] FIGS. ("FIGS.") 1A-1M illustrate cross sectional views of strands made in accordance with the present invention. [0019] FIG. 2 illustrates a cross direction incremental stretching system in accordance with one aspect of the present invention. [0020] FIG. 3 illustrates a machine direction incremental stretching system in accordance with another aspect of the present invention. Continue reading... Full patent description for Elastomeric multicomponent fibers, nonwoven webs and nonwoven fabrics Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Elastomeric multicomponent fibers, nonwoven webs and nonwoven fabrics patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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