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Fibers and fabrics prepared from blends of homopolymers and copolymersRelated 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 Stated To Have Specific Attributes (e.g., Heat Or Fire Resistance, Chemical Or Solvent Resistance, High Absorption For Aqueous Compositions, Water Solubility, Heat Shrinkability, Etc.)Fibers and fabrics prepared from blends of homopolymers and copolymers description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060240733, Fibers and fabrics prepared from blends of homopolymers and copolymers. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Technical Field [0002] This invention relates to the field of fibers and more specifically to the field of fibers and fabrics prepared from blends of polypropylene homopolymers and copolymers. [0003] 2. Background of the Art [0004] Homopolymers and copolymers of polypropylene are typically polymerized in continuous polymerization reactors, such as, for example, loop reactors. To produce these polymers one or more monomer streams are generally introduced into the selected reactor and then circulated with an appropriate catalyst. Ziegler-Natta or metallocene catalysts may be employed. The resulting polymers may be subjected to appropriate purification and post-processing steps and then made into end products using conventional techniques such as injection molding and extrusion. These end products may include fibers, which may then be used to prepare woven and non-woven products. [0005] Propylene polymer fibers and fabrics are widely used in many applications including twine, carpet, medical gowns and drapes, and diapers. The optimization of processing characteristics and properties of propylene based fibers and fabrics has been the subject of intense effort. When the fibers are used to form fabrics, specifically nonwoven fabrics, various methods of thermal bonding are employed. To accomplish this it is desirable to have high strength when bonding at the lowest possible temperatures. Unfortunately, many polypropylene fabrics exhibit relatively poor strength properties, and the resins used to prepare them may also present challenges relating to melt spinning and overall melt processing. It would therefore be desirable to have a means or method of providing propylene-based fabric and fibers with improved thermal bonding characteristics, softness and fabric strength properties which may be prepared from resins having desirable melt spinning and melt processing characteristics. SUMMARY OF THE INVENTION [0006] In one aspect, the invention is a fiber, spunbond fabric, or melt blown fabric including a polymer composition that includes a resin blend of from about 60 to about 99 weight percent of a Ziegler-Natta or metallocene catalyzed isotactic polypropylene homopolymer, and from about 1 to about 40 weight percent of a metallocene catalyzed propylene copolymer. The copolymer includes a comonomer in an amount from about 0.05 to about 25 weight (or higher) percent, based on the copolymer. [0007] In another aspect, the invention is an article including a fiber prepared using a polymer composition that includes a resin blend of from about 60 to about 99 weight percent of a Ziegler-Natta or metallocene catalyzed isotactic polypropylene homopolymer, and from about 1 to about 40 weight percent of a metallocene catalyzed propylene copolymer. The copolymer includes a comonomer in an amount from about 0.05 to about 25 weight percent, based on the copolymer. [0008] Another aspect of the invention is a thermally bonded non-woven fabric made using a fiber including a polymer composition including a resin blend of from about 75 to about 95 weight percent of a Ziegler-Natta or metallocene catalyzed isotactic polypropylene homopolymer, and from about 95 to about 75 weight percent of a metallocene catalyzed polypropylene copolymer. The copolymer includes a comonomer in an amount from about 0.05 to about 25 weight percent, based on the copolymer. [0009] An aspect of the invention is an article including a thermally bonded non-woven fabric made using a fiber including a polymer composition including a resin blend of from about 75 to about 95 weight percent of a Ziegler-Natta or metallocene catalyzed isotactic polypropylene homopolymer, and from about 95 to about 75 weight percent of a metallocene catalyzed polypropylene copolymer. The copolymer includes a comonomer in an amount from about 0.05 to about 25 weight percent, based on the copolymer. [0010] In still another aspect, the invention is a method for preparing a non-woven fabric, the method including melt spinning a polymer composition including a resin blend of from about 75 to about 95 weight percent of a Ziegler-Natta or metallocene catalyzed isotactic polypropylene homopolymer, and from about 95 to about 75 weight percent of a metallocene catalyzed propylene copolymer. The copolymer includes a comonomer in an amount from about 0.05 to about 25 weight percent, based on the copolymer. The method also includes forming a fiber and thermally bonding the fiber at a temperature of at least about 240.degree. C. DETAILED DESCRIPTION OF THE INVENTION [0011] Disclosed herein are fibers and non-woven fabrics that may be prepared from a specific blend of metallocene catalyzed polypropylene copolymers and either metallocene catalyzed, or Ziegler-Natta catalyzed, isotactic polypropylene homopolymers. The blend may be in the form of discreet resin blends or in the form of in-situ reactor blends. The resin blend may exhibit good melt spinning processability for preparing fibers. These fibers may be used to form non-woven fabrics in particular, using conventional processes including the spunbond or carded staple process. In either of these processes, the result may be a fabric that exhibits improved tensile strength and other properties, particularly when compared to fabrics prepared using the same homopolymer alone. In other words, incorporation of a given proportion of a metallocene catalyzed copolymer in the starting resin improves the strength properties of the fiber and/or fabric when compared with the strength properties attained by the homopolymer alone. [0012] The resin blend includes a major proportion of an isotactic polypropylene homopolymer and a minor proportion of a random copolymer. These polymers may each be prepared using any conventional polymerization method known or used in the art. Reactor types may include, for example, loop, slurry, continuous stirred tank, or other, and polymerization protocol and conditions may be determined accordingly, as are well known to those of ordinary skill in the art. Gas, slurry, solution phase, and high pressure autoclave processes are all contemplated hereby. For example, a slurry polymerization process may be selected and will generally use pressures of from about 1 to about 100 atmospheres (about 0.1 to about 10 MPa) or greater, and temperatures from about 60.degree. C. to about 150.degree. C. In some embodiments the temperature is from about 50.degree. C. to about 120.degree. C. In such a polymerization a suspension of solid, particulate polymer is formed in a liquid or supercritical polymerization medium to which propylene (and, for the copolymer, a comonomer) and often hydrogen, along with a selected catalyst, are added. The liquid employed in the polymerization medium may be, for example, an alkane or cycloalkane. This medium desirably remains liquid under the conditions of polymerization and is also desirably relatively inert. For example, hexane or isobutene are often employed. Such polymerizations may be conducted in batch or continuous mode and may take place in one reactor or may be carried out in a series of reactors. The amount of time will depend upon the catalyst and reaction conditions. In general, propylene may desirably be homopolymerized or copolymerized for a time period sufficient to yield the intended final homopolymer or copolymer, typically from about 15 to about 120 minutes. In one embodiment the polymerization is continued for a time of from about 30 to about 60 minutes. [0013] In the case of the copolymer, one or more comonomers is also added along with the propylene. In one embodiment the comonomer is a C.sub.2 or C.sub.4-C.sub.16 compound, desirably C.sub.2 or C.sub.4-C.sub.8. In another embodiment the comonomer is desirably ethylene (C.sub.2). The comonomer level in the copolymer is desirably limited. In one embodiment the comonomer is desirably present in the final copolymer in an amount from about 0.05 to about 25 percent by weight of the copolymer. In another embodiment the comonomer is desirably present in an amount from about 1 to about 10 percent by weight of the final copolymer. Feed rate of the ethylene may be adjusted according to the rate of its incorporation into the copolymer under the selected polymerization conditions. Such adjustment will be easily within the skill of those in the art. [0014] Hydrogen may be added to the polymerization system as a molecular weight regulator, depending upon the particular properties of the product desired and the specific catalyst used. When two catalysts having different hydrogen responses are used, the addition of hydrogen may affect the molecular weight distribution of the polymer product and may therefore be employed with the intent to tailor the molecular weight distribution for a specific purpose. This whole section is confusing, and maybe irrelevant. Narrow MWD is desired for spunbond fiber, either by metallocene catalsyst or vis-breaking via peroxide. I have not established the correlation between the MW of the blend resin with the host. [0015] The catalyst that is desirably selected for preparing either just the copolymer, or for both the homopolymer and the copolymer, is a metallocene catalyst. Metallocene catalysts may be characterized generally as coordination compounds incorporating one or more cyclopentadienyl (Cp) groups (which may be substituted or unsubstituted, each substitution being the same or different) coordinated with a transition metal through pi bonding. [0016] The Cp substituent groups may be linear, branched or cyclic hydrocarbyl radicals. The cyclic hydrocarbyl radicals may further form other contiguous ring structures, including, for example indenyl, azulenyl and fluorenyl groups. These additional ring structures may also be substituted or unsubstituted by hydrocarbyl radicals, such as C.sub.1 to C.sub.20 hydrocarbyl radicals. [0017] A specific example of a metallocene catalyst is a bulky ligand metallocene compound generally represented by the formula: [L].sub.mM[A].sub.n; where L is a bulky ligand, A is a leaving group, M is a transition metal and m and n are such that the total ligand valency corresponds to the transition metal valency. For example m may be from 1 to 3 and n may be from 1 to 3. [0018] The metal atom "M" of the metallocene catalyst compound, as described throughout the specification and claims, may be selected from Groups 3 through 12 atoms and lanthanide Group atoms in one embodiment; and selected from Groups 3 through 10 atoms in a more particular embodiment, and selected from Sc, Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, and Ni in yet a more particular embodiment; and selected from Groups 4, 5 and 6 atoms in yet a more particular embodiment, and Ti, Zr, Hf atoms in yet a more particular embodiment, and Zr in yet a more particular embodiment. The oxidation state of the metal atom "M" may range from 0 to +7 in one embodiment; and in a more particular embodiment, is +1, +2, +3, +4 or +5; and in yet a more particular embodiment is +2, +3 or +4. The groups bound the metal atom "M" are such that the compounds described below in the formulas and structures are electrically neutral, unless otherwise indicated. [0019] The bulky ligand generally includes a cyclopentadienyl group (Cp) or a derivative thereof. The Cp ligand(s) form at least one chemical bond with the metal atom M to form the "metallocene catalyst compound". The Cp ligands are distinct from the leaving groups bound to the catalyst compound in that they are not highly susceptible to substitution/abstraction reactions. [0020] Cp typically includes 7-bonded and/or fused ring(s) or ring systems. The ring(s) or ring system(s) typically include atoms selected from group 13 to 16 atoms, for example, carbon, nitrogen, oxygen, silicon, sulfur, phosphorus, germanium, boron, aluminum and combinations thereof, wherein carbon makes up at least 50% of the ring members. Non-limiting examples include cyclopentadienyl, cyclopentaphenanthrenyl, indenyl, benzindenyl, fluorenyl, tetrahydroindenyl, octahydrofluorenyl, cyclooctatetraenyl, cyclopentacyclododecene, phenanthrindenyl, 3,4-benzofluorenyl, 9-phenylfluorenyl, 8-H-cyclopent[a]acenaphthylenyl, 7-H-dibenzofluorenyl, indeno[1,2-9]anthrene, thiophenoindenyl, thiophenofluorenyl, hydrogenated versions thereof (e.g., 4,5,6,7-tetrahydroindenyl, or "H.sub.4Ind"), substituted versions thereof, and heterocyclic versions thereof. [0021] Cp substituent groups may include hydrogen radicals, alkyls, alkenyls, alkynyls, cycloalkyls, aryls, acyls, aroyls, alkoxys, aryloxys, alkylthiols, dialkylamines, alkylamidos, alkoxycarbonyls, aryloxycarbonyls, carbomoyls, alkyl- and dialkylcarbamoyls, acyloxys, acylaminos, aroylaminos, and combinations thereof. More particular non-limiting examples of alkyl substituents include methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl, phenyl, methylphenyl, and tert-butylphenyl groups and the like, including all their isomers, for example tertiary-butyl, isopropyl, and the like. Other possible radicals include substituted alkyls and aryls such as, for example, fluoromethyl, fluoroethyl, difluroethyl, iodopropyl, bromohexyl, chlorobenzyl and hydrocarbyl substituted organometalloid radicals including trimethylsilyl, trimethylgermyl, methyldiethylsilyl and the like; and halocarbyl-substituted organometalloid radicals including tris(trifluoromethyl)silyl, methylbis(difluoromethyl)silyl, bromomethyldimethylgermyl and the like; and disubstituted boron radicals including dimethylboron for example; and disubstituted Group 15 radicals including dimethylamine, dimethylphosphine, diphenylamine, methylphenylphosphine, Group 16 radicals including methoxy, ethoxy, propoxy, phenoxy, methylsulfide and ethylsulfide. Other substituents R include olefins such as but not limited to olefinically unsaturated substituents including vinyl-terminated ligands, for example 3-butenyl, 2-propenyl, 5-hexenyl and the like. In one embodiment, at least two R groups, two adjacent R groups in one embodiment, are joined to form a ring structure having from 3 to 30 atoms selected from the group consisting of carbon, nitrogen, oxygen, phosphorus, silicon, germanium, aluminum, boron and combinations thereof. Also, a substituent group R group such as 1-butanyl may form a bonding association to the element M. Continue reading about Fibers and fabrics prepared from blends of homopolymers and copolymers... Full patent description for Fibers and fabrics prepared from blends of homopolymers and copolymers Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Fibers and fabrics prepared from blends of homopolymers and copolymers 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. Start now! - Receive info on patent apps like Fibers and fabrics prepared from blends of homopolymers and copolymers or other areas of interest. ### Previous Patent Application: Formed mat Next Patent Application: Method for fabricating field emitters by using laser-induced re-crystallization Industry Class: Fabric (woven, knitted, or nonwoven textile or cloth, etc.) ### FreshPatents.com Support Thank you for viewing the Fibers and fabrics prepared from blends of homopolymers and copolymers patent info. IP-related news and info Results in 0.36757 seconds Other interesting Feshpatents.com categories: Accenture , Agouron Pharmaceuticals , Amgen , AT&T , Bausch & Lomb , Callaway Golf 174 |
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