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  Improved abrasion resistance of nonwovensUSPTO Application #: 20060234588Title: Improved abrasion resistance of nonwovens Abstract: An extruded web material comprises a conjugate fiber including first and second fiber portions. The first fiber portion extends substantially continuously along the length of the conjugate fiber and comprises a first thermoplastic polymeric material. The second fiber portion extends substantially continuously along the length of the conjugate fiber and defines at least a portion of a conjugate fiber exterior surface. The second fiber portion comprises a second thermoplastic polymeric material. At least one of the first fiber portion or the second fiber portion further comprises a thermoplastic adhesive component. The extruded web material is produced by spunbonding or meltblowing. The extruded web material can also be included in a composite article. (end of abstract) Agent: Alix Yale & Ristas LLP - Hartford, CT, US Inventor: Smita Bais USPTO Applicaton #: 20060234588 - Class: 442361000 (USPTO) Related Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Nonwoven Fabric (i.e., Nonwoven Strand Or Fiber Material), Including Strand Or Fiber Material Which Is A Monofilament Composed Of Two Or More Polymeric Materials In Physically Distinct Relationship (e.g., Sheath-core, Side-by-side, Islands-in-sea, Fibrils-in-matrix, Etc.) Or Composed Of Physical Blend Of Chemically Different Polymeric Materials Or A Physical Blend Of A Polymeric Material And A Filler Material The Patent Description & Claims data below is from USPTO Patent Application 20060234588. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] This invention relates generally to extruded web materials. More particularly, the present invention relates to a method of producing an extruded web material comprising a fiber or filament wherein the fiber or filament includes a thermoplastic adhesive component and to the extruded web material made thereby. BACKGROUND OF THE INVENTION [0002] Staple fibers are fibers used for nonwoven web formation that have a typical length of 0.6 cm to 20 cm. Nonwoven fabrics made from staple fibers have been in use for several decades. These nonwovens are formed by processing staple fibers using carding, or air forming techniques, depositing them on a forming wire and using a bonding technique such as thermal bonding, hydro-entangling or needle-punching to form a bonded web. Short staple fibers may also be used in a wet forming process, where water is used as a medium to disperse pulp and short cut staple fibers into a slurry, which is then deposited on a forming wire to form a nonwoven web. A variety of short binder fibers can be used to impart heat bondable properties to nonwoven webs made from staple fibers. [0003] In the spunbonding and meltblowing processes, nonwoven web materials are formed directly from extruded polymers doing away with the need cut fibers to staple lengths and subsequently card, air form or water form the staple fibers into a nonwoven web. The spunbonding process generally uses a heated extruder that supplies melted polymer to a spinneret where the polymer is converted to filaments, forming a vertically oriented curtain of downward advancing filaments. The filaments are partially cooled in a quench chamber, usually with chilled air, reaching a temperature suitable for the next stage of the process. A drawing unit (or attenuator) located below the quench chamber creates a drawing force on the partly cooled filaments, causing them to be attenuated or stretched to a large degree. The filaments exit the bottom of the attenuator unit where they are deposited on a forming element, usually a moving, porous, conveyor belt, to form a batt of substantially continuous filaments. The batt is accumulated, generally in roll form. Typically, the filaments extend the length of the batt, which may be hundreds or thousands of meters in length. After deposition on the forming element, some or all of the filaments in the batt may be joined to each other through conventional techniques such as thermal bonding to form a nonwoven web material. [0004] The melt blown process forms fibers by extruding molten thermoplastic polymer through a plurality of fine, usually circular, die capillaries as molten threads or filaments into converging heated, high velocity gas (e.g. air) streams which attenuate the filaments of molten thermoplastic material to reduce their diameter, generally to micron or sub-micron dimensions. Thereafter, the meltblown filaments are carried by the high velocity gas stream and are deposited on a forming surface to form a batt of randomly dispersed meltblown fibers. The batt is accumulated, generally in roll form. Meltblown fibers are substantially continuous when deposited onto the forming surface and typically extend the length of the batt, which may be hundreds or thousands of meters in length. After cooling, some or all of the fibers in the batt may be joined to each other through web consolidation techniques with or without the use of heat. [0005] Thermal bonding holds the nonwoven web material together by bonding fibers or filaments within the fabric. Thermal bonding techniques include passing a collection of fibers to be bonded between heated calender rolls. One of the calender rolls is usually, though not always, patterned in some way so that the entire fabric is not bonded across its entire surface. This technique is known as thermal point bonding or thermal pattern bonding. As a result, various patterns for calender rolls have been developed for functional as well as aesthetic reasons. Typically, the percent bonded area for pattern bonding varies from around 5% to around 50% of the area of the nonwoven web material. One example of a thermal point bond pattern has points with about a 30% bond area and about 200 bonds/square inch. [0006] Spunbonded fabrics made from single polymer fibers may not provide the desired combination of properties. For example, spunbonded fabrics consisting of polyester fibers are strong, high temperature stable and radiation sterilizable for medical applications but they do not offer a high degree of softness. Spunbonded fabrics consisting of polyethylene fibers tend to be soft to the touch, drapeable and have a pleasant hand, but generally suffer from low strength properties and poor abrasion resistance. Therefore, spunbonded fabrics have been produced using conjugate fibers or filaments, to provide a fabric having a more desirable combination of properties. Conjugate fibers or filaments are formed from at least two separate polymer sources extruded from separate extruders but spun together to form a single fiber or filament. The extruded polymers are located, by means of the internal design of the spinning equipment, in substantially constantly positioned distinct zones across the cross-section of the conjugate fiber or filament and extend substantially continuously along the length of the conjugate fiber or filament. [0007] Bicomponent fibers of the sheath:core type containing polyethylene at the surface generally retain the poor abrasion resistance of monocomponent polyethylene fibers. Thermally bonded, nonwoven web materials comprising such mono- or bicomponent fibers or filaments incorporating polyethylene similarly tend to similarly suffer from poor abrasion resistance. Thus, there remains a need for a more abrasion resistant nonwoven material comprising polyethylene fibers. Definitions [0008] Bicomponent fiber or filament--Conjugate fiber or filament that has been formed by extruding polymer sources from separate extruders and spun together to form a single fiber or filament. Typically, two separate polymers are extruded, although a bicomponent fiber or filament may encompass extrusion of the same polymeric material from separate extruders. The extruded polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the bicomponent fibers or filaments and extend substantially continuously along the length of the bicomponent fibers or filaments. The configuration of bicomponent fibers or filaments can be symmetric (e.g., sheath:core or side:side) or they can be asymmetric (e.g., offset core within sheath; crescent moon configuration within a fiber having an overall round shape). The two polymer sources may be present in ratios of, for example (but not exclusively), 75/25, 50/50 or 25/75. [0009] Conjugate fiber or filament--Fiber or filament that has been formed by extruding polymer sources from separate extruders and spun together to form a single fiber or filament. A conjugate fiber encompasses the use of two or more separate polymers each supplied by a separate extruder. The extruded polymers are arranged in substantially constantly positioned distinct zones across the cross-section of the conjugate fiber or filament and extend substantially continuously along the length of the conjugate fiber or filament. The shape of the conjugate fiber or filament can be any shape that is convenient to the producer for the intended end use, e.g., round, trilobal, triangular, dog-boned, flat or hollow. [0010] Cross machine direction (CD)--The direction perpendicular to the machine direction. [0011] Denier--A unit used to indicate the fineness of a filament given by the weight in grams for 9,000 meters of filament. A filament of 1 denier has a mass of 1 gram for 9,000 meters of length. [0012] Extruded web material--A nonwoven sheet material formed by the spunbond or meltblown process. As used herein an extruded web material excludes nonwoven web materials made from staple fibers using wet laid, air laid or carding processes. The extruded web material can comprise one or more layers and can comprise post-formation treatments. [0013] Fiber--A material form characterized by an extremely high ratio of length to diameter. As used herein, the terms fiber and filament are used interchangeably unless otherwise specifically indicated. [0014] Filament--A substantially continuous fiber. As used herein, the terms fiber and filament are used interchangeably unless otherwise specifically indicated. [0015] Machine direction (MD)--The direction of travel of the forming surface onto which fibers or filaments are deposited during formation of a nonwoven web material. [0016] Meltblown fiber--A fiber formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, die capillaries into a high velocity gas (e.g., air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Meltblown fibers are generally continuous. The meltblown process includes the meltspray process. [0017] Non-thermoplastic polymer--Any polymer material that does not fall within the definition of thermoplastic polymer. [0018] Nonwoven fabric, sheet or web--A material having a structure of individual fibers which are interlaid, but not in an identifiable manner as in a woven or knitted fabric. Nonwoven materials have been formed from many processes such as, for example, meltblowing, spunbonding, carding and water laying processes. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm) and the fiber fineness is measured in denier. [0019] Polymer--A long chain of repeating, organic structural units. Generally includes, for example, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc, and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term "polymer" includes all possible geometrical configurations. These configurations include, for example, isotactic, syndiotactic and random symmetries. [0020] Spunbond filament--A filament formed by extruding molten thermoplastic materials from a plurality of fine, usually circular, capillaries of a spinneret. The diameter of the extruded filaments is then rapidly reduced as by, for example, eductive drawing and/or other well-known spunbonding mechanisms. Spunbond fibers are generally continuous with deniers within the range of about 0.1 to 5 or more. [0021] Spunbond nonwoven web--Webs formed (usually) in a single process by extruding at least one molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinneret. The filaments are partly quenched and then drawn out to reduce fiber denier and increase molecular orientation within the fiber. The filaments are generally continuous and not tacky when they are deposited onto a collecting surface as a fibrous balt. The fibrous balt is then bonded by, for example, thermal bonding, chemical binders, mechanical needling, hydraulic entanglement or combinations thereof, to produce a nonwoven fabric. Continue reading... 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