Patent Description:
Air-through bonded nonwovens are fabrics that are bonded through heat, typically hot air, using processes that are also referred to as air-through bonding. Air-through bonded nonwovens, which may also be referred to as air-through nonwovens, offer several advantages including bulkiness, softness, and good hand feel. These nonwoven fabrics are also advantageous because they lack chemical bonding agents. As a result, air-through nonwovens are useful in the manufacture of a wide range of articles, especially disposable hygiene goods such as diapers, sanitary napkins, training pants, and adult incontinence products.

Air-through nonwovens are conventionally produced from multilayered fibers. Generally speaking, these multilayered fibers include a core of a relatively high melt polymer encased within a polymer having a lower melt temperature (i.e. a sheath). Hot air is applied to at least partially melt the sheath and thereby bond or heat set the fibers. The nonwoven fabric to which the air-through bonding is applied can be formed by a variety of technologies including carding, spunbonding, airlaying, thermal bonding, wetlaying and spunlacing. Conventionally, many air-through bonded nonwoven fabrics are prepared from carded multilayer staple fiber webs or spunmelt nonwoven webs of multilayered fibers.

Multilayered fibers, which are also referred to as multicomponent fibers, are often prepared by using a spinning process in which separate polymer streams are fed to a single die or spinneret in order to form fibers having two (or more) polymer phases. While many structural variations of multicomponent fibers exist, sheath-core, or core-sheath, multicomponent fibers are often used in the manufacture of air-through nonwoven fabrics, especially those used in the manufacture of disposable hygiene products. In this regard, it is common to employ polypropylene or polyethylene terephthalate within the core, and polyethylene, which has a lower melt temperature, within the sheath. Polypropylene and polyethylene terephthalate have higher stiffness and melt temperatures, which ensure that the fiber bulkiness can be maintained during the air-through bonding process. Japanese patent publication <CIT> describes a nonwoven comprising fibers having an ethylene-propylene copolymer at the surface, and further comprising an olefin-based polymer having a higher melt temperature than the ethylene-propylene copolymer. Patent application publication <CIT> describes a spunbonded nonwoven having core/sheath filaments comprising thermoplastic polyurethane and an elastic propylene-based olefin copolymer. US patent application publication <CIT> describes fibers comprising a blend of an impact copolymer and a propylene-based elastomer. Patent application publication <CIT> describes bicomponent fibers having a sheath comprising a sheath polymer which is a polyolefin, and a core having a weight average molecular weight less than that of the sheath polymer.

The present invention provides a bicomponent fiber according to claim <NUM>.

The present invention further provides a nonwoven fabric according to claim <NUM>.

The present invention further provides a process for forming bicomponent polymer fibers, according to claim <NUM>.

The present invention further provides a process for forming an air-through nonwoven fabric, according to claim <NUM>.

Embodiments of the invention are based, at least in part, on the discovery of bicomponent polymeric fibers having a core and sheath, where the sheath includes a propylene-based elastomer. In one or more embodiments, the core includes a polymer having a higher flexural modulus and higher melt temperature than the propylene-based elastomer. While bicomponent fibers have been produced using polyethylene in the sheath, it has now been discovered that polyethylene gives rise to several disadvantages including gelling during the spinning process, limited temperature windows in which the fabrics can be bonded, limited tensile strength of the bonded fabric, and the inability to recycle the fibers. In contrast, the present invention employs propylene-based elastomer in the sheath, which advantageously provides for less gelling during the spinning process, lower-bonding temperature, higher tensile strength when bonded, and the ability to recycle the fabric. One or more of these advantages can be attributed to the lower melt temperature of the propylene-based elastomer, the higher tensile strength of the propylene-based elastomer, and the compatibility that exists between the propylene-based elastomer and useful core polymers, especially polypropylene. Additionally, the propylene-based elastomer has been found to offer good hand feel to the finished product. Accordingly, embodiments of the invention are directed toward multicomponent fibers, such as bicomponent fibers, and methods for producing these fibers, where the sheath includes propylene-based elastomer.

For purposes of this specification, the term "fiber," which may be used interchangeably with the terms "filament" or "monofilament," refers to a structure whose length is substantially greater than its diameter or breadth. In or more embodiments, the fibers of the present invention have an average diameter of from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>. In these or other embodiments, the fibers of the present invention have an aspect ratio of from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>.

For purposes of this specification, a "bicomponent fiber" is a multicomponent fiber including two or more polymer domains. In one or more embodiments, the bicomponent fibers of the present invention include a first polymer domain forming a sheath and a second polymer domain forming a core of the fiber (i.e. a sheath-core arrangement). In one or more embodiments, the core-sheath arrangement of the fibers of the present invention is concentric, which refers to a sheath and core that share the same center, or it may be eccentric, which refers to a sheath and the core that have different centers, or it may be multi-lobal, which refers to a cross-sectional structure that includes three or more lobes with the core being encased by the sheath in each lobe. In one or more embodiments, the sheath completely encases the core at cross-sections along the length of the fiber (e.g. the sheath forms a annulus around a circular core).

In one or more embodiments, the fibers of the present invention may be characterized by the ratio of the average cross-sectional area of the core to the average cross-sectional area of the sheath. In one or more embodiments, the ratio of the average cross-sectional area of the core to the average cross-sectional area of the sheath is from about <NUM>:<NUM> to about <NUM>:<NUM>, in other embodiments from about <NUM>:<NUM> to about <NUM>:<NUM>, and in other embodiments from about <NUM>:<NUM> to about <NUM>:<NUM>.

In one or more embodiments, the bicomponent fibers of the present invention may be characterized by the weight ratio of the sheath polymer to the core polymer. In one or more embodiments, the ratio of the weight of the core to the weight of the sheath may be from about <NUM>:<NUM> to about <NUM>:<NUM>, in other embodiments from about <NUM>:<NUM> to about <NUM>:<NUM>, in other embodiments from about <NUM>:<NUM> to about <NUM>:<NUM>, in other embodiments from about <NUM>:<NUM> to about <NUM>:<NUM>, and in other embodiments from about <NUM>:<NUM> to about <NUM>:<NUM>.

In one or more embodiments, the sheath and the core, individually and irrespective of each other, may be "mono-constituent," which refers to the presence of a single polymeric species, or they may be "bi-constituent," which refers to a blend of two or more distinct polymeric species. For purposes of this specification, distinct polymeric species refers to polymers that are compositionally distinct (e.g. different type or amount of polymeric units) or that are structurally distinct (e.g. differ in molecular weight or molecular architecture).

In one or more embodiments, the fibers of the present invention may be characterized by fiber tenacity, which is the force/denier of a fiber bundle (<NUM>-fibers per bundle) and is reported in grams/denier. Fiber tenacity, as described herein, is measured using a Textechno Statimat M S/N <NUM>, CRE loaded with a Textechno program FPAM0210E. These Textechno products are commercially available from Textechno Herbert Stein GmbH & Co. located in M5nchengladbach, Germany. To test the fibers, a fiber bundle is threaded through ceramic guides on the Statimat M into a pneumatic clamp. The gage length for the fiber bundles being tested is <NUM>. Each fiber bundle is pulled at <NUM>/min until it fails. The force to pull the fiber bundle and the strain of the fiber bundle are recorded until failure occurs.

In one or more embodiments, the fibers of the present invention have a fiber tenacity of greater than <NUM>/den, in other embodiments greater than <NUM>/den, in other embodiments greater than <NUM>/den, in other embodiments greater than <NUM>/den, in other embodiments greater than <NUM>/den, in other embodiments greater than <NUM>/den, in other embodiments greater than <NUM>/den, and in other embodiments greater than <NUM>/den. In one or more embodiments, the fibers of the present invention have a fiber tenacity from about <NUM>/den to about <NUM>/den, in other embodiments about <NUM>/den to about <NUM>/den, and in other embodiments about <NUM>/den to about <NUM>/den.

The sheath of the bicomponent fibers of the present invention is formed from a composition that includes a propylene-based elastomer. In one or more embodiments, the sheath is bi-constituent. In one or more embodiments, the sheath may include a blend of a propylene-based elastomer and a second polymer that is not a propylene-based elastomer. In these embodiments, the sheath includes greater than <NUM> wt%, in other embodiments greater than <NUM> wt%, and in other embodiments greater than <NUM> wt% propylene-based elastomer, based upon the entire weight of the sheath. In particular embodiments, the sheath consists essentially of propylene-based elastomer whereby the sheath is devoid of other polymer that would have an appreciable impact on the sheath. In particular embodiments, the sheath consists of propylene-based elastomer.

In one or more embodiments, the sheath may include first and second propylene-based elastomers. These embodiments may be described with reference to the relative weight of each of the respective propylene-based elastomers. In one or more embodiments, the sheath includes greater than <NUM> wt%, in other embodiments greater than <NUM> wt%, and in other embodiments greater than <NUM> wt% of the first propylene-based copolymer, based upon the total weight of the propylene based elastomer (e.g. the first and second propylene-based elastomers) with the balance including distinct propylene-based elastomer (e.g. the second propylene-based elastomer). In these or other embodiments, the sheath includes less than <NUM> wt%, in other embodiments less than <NUM> wt%, and in other embodiments less than <NUM> wt% of the first propylene-based copolymer, based upon the total weight of the propylene based elastomer (e.g. the first and second propylene-based elastomers) with the balance including distinct propylene-based elastomer (e.g. the second propylene-based elastomer). In one or more embodiments, the sheath includes from about <NUM> to about <NUM> wt%, in other embodiments from about <NUM> to about <NUM> wt%, and in other embodiments from about <NUM> to about <NUM> wt% of the first propylene-based copolymer, based upon the total weight of the propylene based elastomer (e.g. the first and second propylene-based elastomers) with the balance including distinct propylene-based elastomer (e.g. the second propylene-based elastomer).

The propylene-based elastomers are copolymers including propylene-derived units and alpha-olefin-derived units. In other words, the propylene-based elastomers are prepared from the polymerization of propylene and at least one alpha-olefin monomer other than propylene, which alpha-olefins include ethylene. For purposes of this specification, alpha-olefin monomer other than propylene includes ethylene and C4 (i.e. butene) or higher alpha-olefin. In particular embodiments, the propylene-based elastomers are prepared from the polymerization of propylene and ethylene. In this regard, the embodiments described below may be discussed with reference to ethylene as the alpha-olefin comonomer, but the embodiments are equally applicable to other propylene-based elastomers with other alpha-olefin-derived units. Also, while only certain embodiments include a first and second propylene-based elastomer within the sheath, unless otherwise stated, reference will be made to "first propylene-based elastomer" even for those embodiments that include only one propylene-based elastomer.

Propylene-based elastomers can be characterized by comonomer content, which as described below, can be determined by 4D GPC analysis.

The first propylene-based elastomer includes propylene-derived units and greater than <NUM> wt%, in other embodiments greater than <NUM> wt%, in other embodiments greater than <NUM> wt%, and in other embodiments greater than <NUM> wt% ethylene-derived units, based upon the entire weight of the copolymer (i.e. the total weight of the propylene-derived and ethylene-derived units). The first propylene-based elastomer includes propylene-derived units and less than <NUM> wt%, in other embodiments less than <NUM> wt%, in other embodiments less than <NUM> wt%, and in other embodiments less than <NUM> wt% ethylene-derived units, based upon the entire weight of the copolymer. The first propylene-based elastomer includes propylene-derived units and from about <NUM> to about <NUM> wt%, in other embodiments from about <NUM> to about <NUM> wt%, in other embodiments from about <NUM> to about <NUM> wt%, and in other embodiments from about <NUM> to about <NUM> wt% ethylene-derived units, based upon the entire weight of the copolymer. As the skilled person will appreciate, the amount of the alpha-olefin-derived units can be determined by GPC analysis as described herein.

Propylene-based elastomers can be characterized by a melting point (Tm), which can be determined by differential scanning calorimetry (DSC), where the maximum of the highest temperature peak is considered to be the melting point of the polymer. A "peak" in this context is defined as a change in the general slope of the DSC curve (heat flow versus temperature) from positive to negative, forming a maximum without a shift in the baseline where the DSC curve is plotted so that an endothermic reaction would be shown with a positive peak.

As used within this specification, conventional DSC procedures are used for determining Tm and Hf.

The following procedure is employed. About <NUM> grams of polymer is weighed out and pressed to a thickness of about <NUM>-<NUM> mils (about <NUM>-<NUM> microns) at about <NUM> -<NUM>, using a "DSC mold" and Mylar™ as a backing sheet. The pressed pad is allowed to cool to ambient temperature by hanging in air (the Mylar was not removed). The pressed pad is annealed at room temperature (about <NUM> - <NUM>) for about <NUM> days. At the end of this period, an about <NUM>-<NUM> disc is removed from the pressed pad using a punch die and placed in a <NUM> microliter aluminum sample pan. The sample is placed in a differential scanning calorimeter (Perkin Elmer Pyris <NUM> Thermal Analysis System) and cooled to about -<NUM>. The sample is heated at about <NUM>/min to attain a final temperature of about <NUM>. The thermal output, recorded as the area under the melting peak of the sample, is a measure of the heat of fusion and can be expressed in Joules per gram (J/g) of polymer and automatically calculated by the Perkin Elmer System. Under these conditions, the melting profile shows two (<NUM>) maxima, the maxima at the highest temperature was taken as the melting point within the range of melting of the sample relative to a baseline measurement for the increasing heat capacity of the polymer as a function of temperature.

In one or more embodiments, the melt temperature (Tm) of the first propylene-based elastomer (as determined by DSC) is less than <NUM>, in other embodiments less than <NUM>, in other embodiments less than <NUM>, and in other embodiments less than <NUM>. In one or more embodiments, the Tm of the first propylene-based elastomer is from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>.

Propylene-based elastomers can be characterized by a heat of fusion (Hf), which can be determined by DSC.

In one or more embodiments, the first propylene-based elastomer may be characterized by its heat of fusion (Hf), as determined by DSC of greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, and in other embodiments greater than <NUM> J/g. The first propylene-based elastomer is characterized by an Hf of less than <NUM> J/g, in other embodiments less than <NUM> J/g, in other embodiments less than <NUM> J/g, and in other embodiments less than <NUM> J/g. In one or more embodiments, the first propylene-based elastomer has an Hf of from about <NUM> to about <NUM> J/g, in other embodiments from about <NUM> to about <NUM> J/g, and in other embodiments from about <NUM> to about <NUM> J/g.

Propylene-based elastomers can be characterized by a triad tacticity of three propylene-derived units, as measured by <NUM>C NMR according to the methods described in <CIT>.

The first propylene-based elastomer has a triad tacticity of greater than <NUM>%, in other embodiments greater than <NUM>%, in other embodiments greater than <NUM>%, in other embodiments greater than <NUM>%, in other embodiments greater than <NUM>%, in other embodiments greater than <NUM>%, and in other embodiments greater than <NUM>%. In one or more embodiments, the triad tacticity of the first propylene-based elastomer may range from about <NUM> to about <NUM>%, in other embodiments from about <NUM> to about <NUM>%, in other embodiments from about <NUM> to about <NUM>%, in other embodiments from about <NUM> to about <NUM>%, in other embodiments from about <NUM> to about <NUM>%, and in other embodiments from about <NUM> to about <NUM>%.

Propylene-based elastomers can be characterized by a tacticity index (m/r), which is determined by <NUM>C nuclear magnetic resonance ("NMR"), where the tacticity index (m/r) is calculated as defined by <NPL>). The designation "m" or "r" describes the stereochemistry of pairs of contiguous propylene groups, where "m" refers to meso and "r" refers to racemic. As the skilled person appreciates, an m/r ratio of <NUM> generally describes a syndiotactic polymer, and an m/r ratio of <NUM> generally describes an atactic material. An isotactic material theoretically may have a ratio approaching infinity, and many by-product atactic polymers have sufficient isotactic content to result in ratios of greater than <NUM>.

In one or more embodiments, the first propylene-based elastomer may have a tacticity index (m/r) of greater than <NUM> or in other embodiments greater than <NUM>. In these or other embodiments, the first propylene-based elastomer may have a tacticity index (m/r) of less than <NUM>, in other embodiments less than <NUM>, or in other embodiments less than <NUM>.

Propylene-based elastomers can be characterized by crystallinity, which may be determined by DSC procedures, where the Hf of a sample of the propylene-based elastomer isdivided by the Hf of a <NUM>% crystalline polymer, which is assumed to be <NUM> joules/gram for isotactic polypropylene or <NUM> joules/gram for polyethylene.

In one or more embodiments, the first propylene-based elastomer may have a crystallinity of from about <NUM>% to about <NUM>%, in other embodiments from about <NUM>% to about <NUM>%, and in other embodiments from about <NUM>% to about <NUM>%.

Propylene-based elastomers can be characterized by density, which is measured at room temperature according to ASTM D-<NUM>.

In one or more embodiments, the first propylene-based elastomer may have a density of from about <NUM>/cm<NUM> to about <NUM>/cm<NUM>, in other embodiments from about <NUM>/cm<NUM> to about <NUM>/cm<NUM>, and in other embodiments from about <NUM>/cm<NUM> to about <NUM>/cm<NUM>.

Propylene-based elastomers can be characterized by melt flow rate (MFR), which is measured according to ASTM D-<NUM>, <NUM> weight @ <NUM>.

In one or more embodiments, the first propylene-based elastomer may have an MFR of greater than <NUM>/<NUM>, in other embodiments greater than <NUM>/<NUM>, in other embodiments greater than <NUM>/<NUM>, in other embodiments greater than about <NUM>/<NUM>, and in other embodiments greater than <NUM>/<NUM>. In the same or other embodiments, the first propylene-based polymer may have an MFR of less than <NUM>/<NUM>, in other embodiments less than about <NUM>/<NUM>, in other embodiments less than about <NUM>/<NUM>, in other embodiments less than about <NUM>/<NUM>, and in other embodiments less than about <NUM>/<NUM>. In these or other embodiments, the first propylene-based polymer may have an MFR from about <NUM> to about <NUM>/<NUM>, in other embodiments from about <NUM> to about <NUM>/<NUM>, and other embodiments from about <NUM> to about <NUM>/<NUM>.

Propylene-based elastomers may be characterized by molecular weight moments and branching index (g').

Unless otherwise indicated, the distribution and the moments of molecular weight (Mp, Mw, Mn, Mz, Mw/Mn, etc.), the comonomer content (C2, C3, C6, etc.), and the branching index (g') are determined by using a high temperature Gel Permeation Chromatography (Polymer Char GPC-IR) equipped with a multiple-channel band-filter based Infrared detector IR5, an <NUM>-angle light scattering detector and a viscometer (which may be referred to as 4D GPC analysis). Three Agilent PLgel <NUM>-µm Mixed-B LS columns are used to provide polymer separation. Aldrich reagent grade <NUM>,<NUM>,<NUM>-trichlorobenzene (TCB) with <NUM> ppm antioxidant butylated hydroxytoluene (BHT) is used as the mobile phase. The TCB mixture is filtered through a <NUM>-µm Teflon filter and degassed with an online degasser before entering the GPC instrument. The nominal flow rate is <NUM>/min and the nominal injection volume is <NUM>µL. The whole system including transfer lines, columns, and detectors are contained in an oven maintained at <NUM>. Given amount of polymer sample is weighed and sealed in a standard vial with <NUM>-µL flow marker (Heptane) added to it. After loading the vial in the autosampler, polymer is automatically dissolved in the instrument with <NUM> added TCB solvent. The polymer is dissolved at <NUM> with continuous shaking for about <NUM> hour for most polyethylene samples or <NUM> hours for polypropylene samples. The TCB densities used in concentration calculation are <NUM>/ml at room temperature and <NUM>/ml at <NUM>. The sample solution concentration is from <NUM> to <NUM>/ml, with lower concentrations being used for higher molecular weight samples. The concentration (c), at each point in the chromatogram is calculated from the baseline-subtracted IR5 broadband signal intensity (I), using the following equation: c = βI, where β is the mass constant. The mass recovery is calculated from the ratio of the integrated area of the concentration chromatography over elution volume and the injection mass which is equal to the pre-determined concentration multiplied by injection loop volume. The conventional molecular weight (IR MW) is determined by combining universal calibration relationship with the column calibration which is performed with a series of monodispersed polystyrene (PS) standards ranging from <NUM> to <NUM> gm/mole. The MW at each elution volume is calculated with following equation: <MAT> where the variables with subscript "PS" stand for polystyrene while those without a subscript are for the test samples. In this method, αPS=<NUM> and KPS=<NUM>, while α and K for other materials are as calculated and published in literature (<NPL>), except that for purposes of this invention and claims thereto, α=<NUM> and K=<NUM> for linear ethylene polymers, α=<NUM> and K=<NUM> for linear propylene polymers, α=<NUM> and K=<NUM> for linear butene polymers, α is <NUM> and K is <NUM>*(<NUM>-<NUM>*w2b+<NUM>*(w2b)^<NUM>) for ethylene-butene copolymer where w2b is a bulk weight percent of butene comonomer, α is <NUM> and K is <NUM>*(<NUM>-<NUM>*w2b) for ethylene-hexene copolymer where w2b is a bulk weight percent of hexene comonomer, and α is <NUM> and K is <NUM>*(<NUM>-<NUM>*w2b) for ethylene-octene copolymer where w2b is a bulk weight percent of octene comonomer. Concentrations are expressed in g/cm<NUM>, molecular weight is expressed in g/mole, and intrinsic viscosity (hence K in the Mark-Houwink equation) is expressed in dL/g unless otherwise noted.

The comonomer composition is determined by the ratio of the IR5 detector intensity corresponding to CH<NUM> and CH<NUM> channel calibrated with a series of PE and PP homo/copolymer standards whose nominal value are predetermined by NMR or FTIR. In particular, this provides the methyls per <NUM> total carbons (CH<NUM>/1000TC) as a function of molecular weight. The short-chain branch (SCB) content per 1000TC (SCB/1000TC) is then computed as a function of molecular weight by applying a chain-end correction to the CH<NUM>/1000TC function, assuming each chain to be linear and terminated by a methyl group at each end. The weight % comonomer is then obtained from the following expression in which f is <NUM>, <NUM>, <NUM>, <NUM>, and so on for C3, C4, C6, C8, and so on co-monomers, respectively: <MAT>.

The bulk composition of the polymer from the GPC-IR and GPC-4D analyses is obtained by considering the entire signals of the CH<NUM> and CH<NUM> channels between the integration limits of the concentration chromatogram. First, the following ratio is obtained <MAT>.

Then the same calibration of the CH<NUM> and CH<NUM> signal ratio, as mentioned previously in obtaining the CH3/1000TC as a function of molecular weight, is applied to obtain the bulk CH3/1000TC. A bulk methyl chain ends per 1000TC (bulk CH3end/1000TC) is obtained by weight-averaging the chain-end correction over the molecular-weight range. Then <MAT> <MAT> and bulk SCB/1000TC is converted to bulk w<NUM> in the same manner as described above.

The LS detector is the <NUM>-angle Wyatt Technology High Temperature DAWN HELEOSII. The LS molecular weight (M) at each point in the chromatogram is determined by analyzing the LS output using the Zimm model for static light scattering (<NPL>. ): <MAT> Here, ΔR(θ) is the measured excess Rayleigh scattering intensity at scattering angle θ, c is the polymer concentration determined from the IR5 analysis, A<NUM> is the second virial coefficient, P(θ) is the form factor for a monodisperse random coil, and KO is the optical constant for the system: <MAT> where NA is Avogadro's number, and (dn/dc) is the refractive index increment for the system. The refractive index, n=<NUM> for TCB at <NUM> and λ=<NUM>. For analyzing polyethylene homopolymers, ethylene-hexene copolymers, and ethylene-octene copolymers, dn/dc=<NUM>/mg and A<NUM>=<NUM>; for analyzing ethylene-butene copolymers, dn/dc=<NUM>*(<NUM>-<NUM>*w2) ml/mg and A<NUM>=<NUM> where w2 is weight percent butane.

For use herein, the g' index is defined as: <MAT> where ηb is the intrinsic viscosity of the polymer and η<NUM> is the intrinsic viscosity of a linear polymer of the same viscosity-averaged molecular weight (Mv) as the polymer. η<NUM>=KWv α, K and α are measured values for linear polymers and should be obtained on the same instrument as the one used for the g' index measurement.

Reference can be made to <CIT>, whose test methods are also fully applicable for the various measurements referred to in this specification and claims and which contain more details on GPC measurements, the determination of ethylene content by NMR and the DSC measurements.

In one or more embodiments, the first propylene-based elastomer can have a weight average molecular weight (Mw) of from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, and in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol. In one or more embodiments, the first propylene-based elastomer can have a number average molecular weight (Mn) of from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, and in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol. In one or more embodiments, the first propylene-based elastomer hay have a molecular weight distribution (Mw/Mn) of from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>.

In one or more embodiments, the first propylene-based elastomer may have a g' index value of <NUM> or greater, or at least <NUM>, or at least <NUM>, wherein g' is measured at the Mw of the polymer using the intrinsic viscosity of isotactic polypropylene as the baseline.

Propylene-based elastomers may be characterized by a flexural modulus, which may also be referred to as <NUM>% secant modulus, which is determined according to ASTM D-<NUM>.

In one or more embodiments, the flexural modulus of the first propylene-based elastomer is less than <NUM>,<NUM> MPa, in other embodiments less than <NUM> MPa, in other embodiments less than <NUM> MPa, and in other embodiments less than <NUM> MPa. In these or other embodiments, the flexural modulus of the first propylene-based elastomer is greater than <NUM> MPa, in other embodiments greater than <NUM> MPa, and in other embodiments greater than <NUM> MPa. In one or more embodiments, the flexural modulus of the first propylene-based elastomer is from about <NUM> to <NUM>,<NUM> MPa, in other embodiments from about <NUM> to <NUM> MPa, and in other embodiments from about <NUM> to <NUM> MPa.

As indicated above, in certain embodiments, the sheath includes a second propylene-based elastomer, which elastomer may also be referred to as flowability modifier. Generally, this second propylene-based elastomer is characterized by having a lower molecular weight, lower viscosity, and/or a higher melt flow rate than that first propylene-based elastomer, and as a result, the composition for forming the sheath has an overall lower melt temperature and thereby the extruding conditions relative to the sheath are less energy intensive. In one or more embodiments, besides the following characteristics, the second propylene-based elastomer can be characterized as set forth above with respect to the first propylene-based elastomer.

In one or more embodiments, the second propylene-based elastomer may have a melt flow rate (MFR), as measured according to ASTM D-<NUM>, <NUM> weight @ <NUM>, of greater than <NUM>/<NUM>, in other embodiments greater than <NUM>/<NUM>, in other embodiments greater than <NUM>/<NUM>, in other embodiments greater than <NUM>/<NUM>, and in other embodiments greater than <NUM>/<NUM>. In the same or other embodiments, the second propylene-based polymer may have an MFR of less than <NUM>/<NUM>, in other embodiments less than <NUM>/<NUM>, in other embodiments less than <NUM>/<NUM>, in other embodiments less than <NUM>/<NUM>, and in other embodiments less than <NUM>/<NUM>. In one or more embodiments, the second propylene-based polymer may have an MFR from about <NUM> to about <NUM>/<NUM>, in other embodiments from about <NUM> to about <NUM>/<NUM>, and other embodiments from about <NUM> to about <NUM>/<NUM>.

In one or more embodiments, the second propylene-based copolymer can have a weight average molecular weight (Mw) of from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, and in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol. In one or more embodiments, the second propylene-based copolymer can have a number average molecular weight (Mn) of from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol, and in other embodiments from about <NUM>,<NUM> to about <NUM>,<NUM>/mol. In one or more embodiments, the second propylene-based elastomer hay have a molecular weight distribution (Mw/Mn) of from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>.

In one or more embodiments, the second propylene-based elastomer may be characterized by its heat of fusion (Hf), as determined by DSC of greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, in other embodiments greater than <NUM> J/g, and in other embodiments greater than <NUM> J/g. In these or other embodiments, the second propylene-based elastomer may be characterized by an Hf of less than <NUM> J/g, in other embodiments less than <NUM> J/g, in other embodiments less than <NUM> J/g, in other embodiments less than <NUM> J/g, in other embodiments less than <NUM> J/g, and in other embodiments less than <NUM> J/g. In one or more embodiments, the second propylene-based elastomer has an Hf of from about <NUM> to about <NUM> J/g, in other embodiments from about <NUM> to about <NUM> J/g, and in other embodiments from about <NUM> to about <NUM> J/g.

In one or more embodiments, the Tm of the second propylene-based elastomer (as determined by DSC) is less than <NUM>, in other embodiments less than <NUM>, in other embodiments less than <NUM>, and in other embodiments less than <NUM>. In one or more embodiments, the Tm of the second propylene-based elastomer is from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>.

In one or more embodiments, the second propylene-based elastomer may be characterized by a flexural modulus, which may also be referred to as <NUM>% secant modulus, which is determined according to ASTM D-<NUM>. In one or more embodiments, the flexural modulus of the second propylene-based elastomer is less than <NUM> MPa, in other embodiments less than <NUM> MPa, in other embodiments less than <NUM> MPa, and in other embodiments less than <NUM> MPa. In these or other embodiments, the flexural modulus of the second propylene-based elastomer is greater than <NUM> MPa, in other embodiments greater than <NUM> MPa, in other embodiments greater than <NUM> MPa, and in other embodiments greater than <NUM> MPa. In one or more embodiments, the flexural modulus of the second propylene-based elastomer is from about <NUM> to <NUM> MPa, in other embodiments from about <NUM> to <NUM> MPa, and in other embodiments from about <NUM> to <NUM> MPa.

Embodiments of the invention can be described with reference to the overall characteristics of the sheath composition, which as explained above may include a single polymeric species or multiple polymeric species.

In one or more embodiments, the sheath composition may be characterized by a flexural modulus, which may also be referred to as <NUM>% secant modulus, which is determined according to ASTM D-<NUM>. In one or more embodiments, the flexural modulus of the sheath composition is less than <NUM>,<NUM> MPa, in other embodiments less than <NUM> MPa, in other embodiments less than <NUM> MPa, and in other embodiments less than <NUM> MPa. In these or other embodiments, the flexural modulus of the sheath composition is greater than <NUM> MPa, in other embodiments greater than <NUM> MPa, and in other embodiments greater than <NUM> MPa. In one or more embodiments, the flexural modulus of the sheath composition is from about <NUM> to <NUM>,<NUM> MPa, in other embodiments from about <NUM> to <NUM> MPa, and in other embodiments from about <NUM> to <NUM> MPa.

The sheath composition may be characterized by a melt temperature (Tm) as determined by DSC. In one or more embodiments, the sheath composition may have a Tm of less than <NUM>, in other embodiments less than <NUM>, in other embodiments less than <NUM>, and in other embodiments less than <NUM>. In one or more embodiments, the Tm of the sheath composition is from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>.

The sheath composition may be characterized by melt flow rate (MFR). In one more embodiments, the sheath composition may have a melt flow rate (MFR), as measured according to ASTM D-<NUM>, <NUM> weight @ <NUM>, of greater than <NUM>/<NUM>, in other embodiments greater than <NUM>/<NUM>, in other embodiments greater than <NUM>/<NUM>, and in other embodiments greater than <NUM>/<NUM>. In the same or other embodiments, the sheath composition may have an MFR of less than <NUM>/<NUM>, in other embodiments less than <NUM>/<NUM>, in other embodiments less than <NUM>/<NUM>, and in other embodiments less than <NUM>/<NUM>. In one or more embodiments, the sheath composition may have an MFR from about <NUM> to about <NUM>/<NUM>, in other embodiments from about <NUM> to about <NUM>/<NUM>, and other embodiments from about <NUM> to about <NUM>/<NUM>.

The sheath composition may be characterized by total ethylene-derived units (which may be included in one or more polymeric species), where the amount of ethylene-derived units is be determined by GPC analysis as described herein. In one or more embodiments, the sheath composition includes greater than <NUM> wt%, in other embodiments greater than <NUM> wt%, in other embodiments greater than <NUM> wt%, and in other embodiments greater than <NUM> wt% ethylene-derived units, based upon the entire weight of the polymeric content of the sheath composition. In these or other embodiments, the sheath composition includes less than <NUM> wt%, in other embodiments less than <NUM> wt%, in other embodiments less than <NUM> wt%, in other embodiments less than <NUM> wt%, in other embodiments less than <NUM> wt%, in other embodiments less than <NUM> wt%, and in other embodiments less than <NUM> wt% ethylene-derived units, based upon the entire weight of the polymeric content of the sheath composition. In one or more embodiments, the sheath composition includes from about <NUM> to about <NUM> wt%, in other embodiments from about <NUM> to about <NUM> wt%, in other embodiments from about <NUM> to about <NUM> wt%, and in other embodiments from about <NUM> to about <NUM> wt% ethylene-derived units, based upon the entire weight of the polymeric content of the sheath composition.

In one or more embodiments, the propylene-based elastomer employed in this invention can be prepared by reacting monomers in the presence of a catalyst system described herein at a temperature of from <NUM> to <NUM> for a time of from <NUM> second to <NUM> hours. In particular embodiments, homogeneous conditions are used, such as a continuous solution process or a bulk polymerization process with excess monomer used as diluent. The continuous process may use some form of agitation to reduce concentration differences in the reactor and maintain steady state polymerization conditions. The heat of the polymerization reaction can be removed by cooling of the polymerization feed and allowing the polymerization to heat up to the polymerization, although internal cooling systems may be used. Further description of exemplary methods suitable for preparation of the propylene-based elastomer described herein may be found in <CIT>.

The triad tacticity and tacticity index of the propylene-based copolymer may be controlled by the catalyst, which influences the stereoregularity of propylene placement, the polymerization temperature, according to which stereoregularity can be reduced by increasing the temperature, and by the type and amount of a comonomer, which tends to reduce the level of longer propylene derived sequences.

The catalyst may also control the stereoregularity in combination with the comonomer and the polymerization temperature. The propylene-based elastomers described herein are prepared using one or more catalyst systems. As used herein, a "catalyst system" includes at least a transition metal compound, also referred to as catalyst precursor, and an activator. Contacting the transition metal compound (catalyst precursor) and the activator in solution upstream of the polymerization reactor or in the polymerization reactor of the disclosed processes yields the catalytically active component (catalyst) of the catalyst system. Any given transition metal compound or catalyst precursor can yield a catalytically active component (catalyst) with various activators, affording a wide array of catalysts deployable in the processes. Catalyst systems may include at least one transition metal compound and at least one activator. However, catalyst systems may also comprise more than one transition metal compound in combination with one or more activators. These catalyst systems may optionally include impurity scavengers. Each of these components is described in further detail below.

In one or more embodiments, the catalyst systems used for producing propylene-based elastomers includes a metallocene compound. In some embodiments, the metallocene compound is a bridged bisindenyl metallocene having the general formula (In<NUM>)Y(In<NUM>)MX<NUM>, where In<NUM> and In<NUM> are identical substituted or unsubstituted indenyl groups bound to M and bridged by Y, Y is a bridging group in which the number of atoms in the direct chain connecting In<NUM> with In<NUM> is from <NUM> to <NUM> and the direct chain comprises C or Si, and M is a Group <NUM>, <NUM>, <NUM>, or <NUM> transition metal. In<NUM> and In<NUM> may be substituted or unsubstituted. If In<NUM> and In<NUM> are substituted by one or more substituents, the substituents are selected from the group consisting of a halogen atom, C<NUM> to C<NUM> alkyl, C<NUM> to C<NUM> aryl, C<NUM> to C<NUM>alkylaryl, and N- or P-containing alkyl or aryl. Exemplary metallocene compounds of this type include, but are not limited to, µ-dimethylsilylbis(indenyl)hafniumdimethyl and µ-dimethylsilylbis(indenyl)zirconiumdimethyl.

In other embodiments, the metallocene compound may be a bridged bisindenyl metallocene having the general formula (In<NUM>)Y(In<NUM>)MX<NUM>, where In<NUM> and In<NUM> are identical <NUM>,<NUM>-substituted indenyl groups bound to M and bridged by Y, Y is a bridging group in which the number of atoms in the direct chain connecting In<NUM> with In<NUM> is from <NUM> to <NUM> and the direct chain comprises C or Si, and M is a Group <NUM>, <NUM>, <NUM>, or <NUM> transition metal. In<NUM> and In<NUM> are substituted in the <NUM> position by a methyl group and in the <NUM> position by a substituent selected from the group consisting of C<NUM> to C<NUM> aryl, C<NUM> to C<NUM> alkylaryl, and N- or P-containing alkyl or aryl. Exemplary metallocene compounds of this type include, but are not limited to, (µ-dimethylsilyl)bis(<NUM>-methyl-<NUM>-(<NUM>,'<NUM>'-di-tert-butylphenyl)indenyl)zirconiumdimethyl, (µ-dimethylsilyl)bis (<NUM>-methyl-<NUM>-(<NUM>,'<NUM>'-di-tert-butylphenyl)indenyl)hafniumdimethyl, (µ-dimethylsilyl)bis(<NUM>-methyl-<NUM>-naphthylindenyl)zirconiumdimethyl, (µ-dimethylsilyl)bis(<NUM>-methyl-<NUM>-naphthylindenyl)hafniumdimethyl, (µ-dimethylsilyl)bis(<NUM>-methyl-<NUM>-(N-carbazyl)indenyl)zirconiumdimethyl, and (µ-dimethylsilyl)bis(<NUM>-methyl-<NUM>-(N-carbazyl)indenyl)hafniumdimethyl.

Alternatively, in one or more embodiments, the metallocene compound may correspond to one or more of the formulas disclosed in <CIT>. These metallocene compounds include, but are not limited to, dimethylsilyl bis(<NUM>-(methyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydrobenz(f)indenyl)hafnium dimethyl, diphenylsilyl bis(<NUM>-(methyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydrobenz(f)indenyl)hafnium dimethyl, diphenylsilyl bis(<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydrobenz(t)indenyl)hafnium dimethyl, diphenylsilyl bis(<NUM>-(methyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydrobenz(f)indenyl)zirconium dichloride, and cyclo-propylsilyl bis(<NUM>-(methyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetramethyl-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydrobenz(f)indenyl)hafnium dimethyl.

In one or more embodiments of the present invention, the activators of the catalyst systems used to produce propylene-based elastomers comprise a cationic component. In some embodiments, the cationic component has the formula [R<NUM>R<NUM>R<NUM>AH]+, where A is nitrogen, R<NUM> and R<NUM>are together a -(CH<NUM>)a- group, where a is <NUM>, <NUM>, <NUM> or <NUM> and form, together with the nitrogen atom, a <NUM>-, <NUM>-, <NUM>- or <NUM>-membered non-aromatic ring to which, via adjacent ring carbon atoms, optionally one or more aromatic or heteroaromatic rings may be fused, and R<NUM> is C<NUM>, C<NUM>, C<NUM>, C<NUM> or C<NUM> alkyl, or N-methylpyrrolidinium or N-methylpiperidinium. In other embodiments, the cationic component has the formula [RnAH]+, where A is nitrogen, n is <NUM> or <NUM>, and all R are identical and are C<NUM> to C<NUM> alkyl groups, such as for example trimethylammonium, trimethylanilinium, triethylammonium, dimethylanilinium, or dimethylammonium.

In one or more embodiments, the activators of the catalyst systems used to produce the propylene-based elastomers comprise an anionic component, [Y]-. In some embodiments, the anionic component is a non-coordinating anion (NCA), having the formula [B(R<NUM>)<NUM>]-, where R<NUM> is an aryl group or a substituted aryl group, of which the one or more substituents are identical or different and are selected from the group consisting of alkyl, aryl, a halogen atom, halogenated aryl, and haloalkylaryl groups. In one or more embodiments, the substituents are perhalogenated aryl groups, or perfluorinated aryl groups, including but not limited to perfluorophenyl, perfluoronaphthyl and perfluorobiphenyl.

Together, the cationic and anionic components of the catalysts systems described herein form an activator compound. In one or more embodiments, the activator may be N,N-dimethylanilinium-tetra(perfluorophenyl)borate, N,N-dimethylanilinium-tetra(perfluoronaphthyl)borate, N,N-dimethylanilinium-tetrakis(perfluorobiphenyl)borate, N,N-dimethylanilinium-tetrakis(<NUM>,<NUM>-bis(trifluoromethyl)phenyl)borate, triphenylcarbenium-tetra(perfluorophenyl)borate, triphenylcarbenium-tetra(perfluoronaphthyl)borate, triphenylcarbenium-tetrakis(perfluorobiphenyl)borate, or triphenylcarbenium-tetrakis(<NUM>,<NUM>-bis(trifluoromethyl)phenyl)borate.

Any catalyst system resulting from any combination of a metallocene compound, a cationic activator component, and an anionic activator component mentioned in the preceding paragraphs shall be considered to be explicitly disclosed herein and may be used in accordance with the present invention in the polymerization of one or more olefin monomers. Also, combinations of two different activators can be used with the same or different metallocene(s).

Suitable activators also include alominoxanes (or alumoxanes) and aluminum alkyls. Without being bound by theory, an alumoxane is typically believed to be an oligomeric aluminum compound represented by the general formula (Rx-Al-O)n, which is a cyclic compound, or Rx (Rx-Al-O)nAlRx <NUM>, which is a linear compound. Most commonly, alumoxane is believed to be a mixture of the cyclic and linear compounds. In the general alumoxane formula, Rx is independently a C<NUM>-C<NUM> alkyl radical, for example, methyl, ethyl, propyl, butyl, pentyl, isomers thereof, and the like, and n is an integer from <NUM>-<NUM>. In one or more embodiments, Rx is methyl and n is at least <NUM>. Methyl alumoxane (MAO), as well as modified MAO containing some higher alkyl groups to improve solubility, ethyl alumoxane, iso-butyl alumoxane, and the like are useful for the processes disclosed herein.

Further, catalyst systems may contain, in addition to the transition metal compound and the activator described above, additional activators (co-activators) and/or scavengers. A co-activator is a compound capable of reacting with the transition metal complex, such that when used in combination with an activator, an active catalyst is formed. Co-activators include alumoxanes and aluminum alkyls.

In some embodiments, scavengers may be used to "clean" the reaction of any poisons that would otherwise react with the catalyst and deactivate it. Typical aluminum or boron alkyl components useful as scavengers are represented by the general formula RxJZ<NUM>where J is aluminum or boron, Rx is a C<NUM>-C<NUM> alkyl radical, for example, methyl, ethyl, propyl, butyl, pentyl, and isomers thereof, and each Z is independently Rx or a different univalent anionic ligand such as halogen (Cl, Br, I), alkoxide (ORx) and the like. Exemplary aluminum alkyls include triethylaluminum, diethylaluminum chloride, ethylaluminium dichloride, tri-iso-butylaluminum, tri-n-octylaluminum, tri-n-hexylaluminum, trimethylaluminum and combinations thereof. Exemplary boron alkyls include triethylboron. Scavenging compounds may also be alumoxanes and modified alumoxanes including methylalumoxane and modified methylalumoxane.

In some embodiments, the catalyst system used to produce the propylene-based elastomers include a transition metal component which is a bridged bisindenyl metallocene having the general formula (In<NUM>)Y(In<NUM>)MX<NUM>, where In<NUM> and In<NUM> are identical substituted or unsubstituted indenyl groups bound to M and bridged by Y, Y is a bridging group in which the number of atoms in the direct chain connecting In<NUM> with In<NUM> is from <NUM> to <NUM> and the direct chain comprises C or Si, and M is a Group <NUM>, <NUM>, <NUM>, or <NUM> transition metal. In<NUM> and In<NUM> may be substituted or unsubstituted. If In<NUM> and In<NUM> are substituted by one or more substituents, the substituents are selected from the group consisting of a halogen atom, C<NUM> to C<NUM> alkyl, C<NUM> to C<NUM> aryl, C<NUM> to C<NUM>alkylaryl, and N- or P-containing alkyl or aryl. In one or more embodiments, the transition metal component used to produce the propylene-based polymers is µ-dimethylsilylbis(indenyl)hafniumdimethyl.

As indicated above, the core includes one or more polymers (i.e. core polymer) that provide the core composition with a higher melt temperature and higher flexural modulus as compared to the sheath composition.

In one or more embodiments, the core composition is characterized by having a flexural modulus, as defined by ASTM D-<NUM>, that is at least <NUM>%, in other embodiments at least <NUM>%, in other embodiments at least <NUM>%, in other embodiments at least <NUM>%, in other embodiments at least <NUM>%, and in other embodiments at least <NUM>% greater than the flexural modulus of the sheath composition. Stated differently, the core composition is characterized by having a flexural modulus, as defined by ASTM D-<NUM>, that is at least <NUM> MPa, in other embodiments at least <NUM> MPa, in other embodiments at least <NUM> MPa, in other embodiments at least <NUM> MPa, in other embodiments at least <NUM> MPa, and in other embodiments at least <NUM> MPa greater than the flexural modulus of the sheath composition.

In one or more embodiments, the core composition is characterized by having a melt temperature (Tm as determined by DSC) that is at least <NUM>%, in other embodiments at least <NUM>%, in other embodiments at least <NUM>%, in other embodiments at least <NUM>%, in other embodiments at least <NUM>%, and in other embodiments at least <NUM>%, greater than the melt temperature of the sheath composition. Stated differently, the core composition is characterized by having a melt temperature (Tm as determined by DSC) that is at least <NUM>, in other embodiments at least <NUM>, in other embodiments at least <NUM>, in other embodiments at least <NUM>, in other embodiments at least <NUM>, in other embodiments at least <NUM>, in other embodiments at least <NUM> greater than the melt temperature of the sheath composition.

In one or more embodiments, the core composition may be characterized by a flexural modulus, which may also be referred to as <NUM>% secant modulus, which is determined according to ASTM D-<NUM>. In one or more embodiments, the flexural modulus of the core composition is greater than <NUM>,<NUM> MPa, in other embodiments greater than <NUM>,<NUM> MPa, and in other embodiments greater than <NUM>,<NUM> MPa. In one or more embodiments, the flexural modulus of the core composition is from about <NUM>,<NUM> to <NUM>,<NUM> MPa, in other embodiments from about <NUM>,<NUM> to <NUM>,<NUM> MPa, and in other embodiments from about <NUM>,<NUM> to <NUM>,<NUM> MPa.

In one or more embodiments, the melt temperature (Tm) of the core composition (as determined by DSC) is greater than <NUM>, in other embodiments greater than <NUM>, and in other embodiments greater than <NUM>. In one or more embodiments, the Tm of the core composition is from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>.

In one or more embodiments, the core composition can include or consist of polymers, such as, but not limited to, propylene-based polymers (e.g., homopolymers, impact copolymers, copolymers), ethylene-based polymers (e.g., LDPE, LLDPE, HDPE (copolymers and block copolymers)), functionalized polyolefins (e.g., Exxelor™. maleic anhydride functionalized elastomeric ethylene copolymers), plastomers (e.g., ethylene-. -olefin copolymers), polyurethane, polyesters such as polyethylene terephthalate, polylactic acid, polyvinyl chloride, polytetrafluoroethylene, styrenic block copolymers, ethylene vinyl acetate copolymers, polyamide, polycarbonate, cellulosics (e.g., Rayon™, Lyocell™. , Tencil™), an elastomer, poly(acetylene), poly(thiophene), poly(aniline), poly(fluorene), poly(pyrrole), poly(<NUM>-alkylhiophene), poly(phenylene sulphide), polynaphthalenes, poly(phenylene vinylene), poly(vinylidene fluoride), and blends of any two or more of these materials. Useful polymers also include plastomers (e.g., ethylene-. -olefin copolymers and block copolymers), polyurethane, polyesters such as polyethylene terephthalate, polylactic acid, polyvinyl chloride, polytetrafluoroethylene, styrenic block copolymers, ethylene vinyl acetate copolymers, polyamide, polycarbonate, cellulosics (e.g., Rayon™, Lyocell™, Tencil™), an elastomer, poly(acetylene), poly(thiophene), poly(aniline), poly(fluorene), poly(pyrrole), poly(<NUM>-alkylhiophene), poly(phenylene sulphide), polynaphthalenes, poly(phenylene vinylene), poly(vinylidene fluoride), and blends of any two or more of these materials.

In particular embodiments, polyesters are used in the core of the bicomponent fibers of the present invention. Exemplary polyesters include polyolefin-terephthalates and polyalkylene terephthalates, such as poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and poly(cyclohexane dimethylene terephthalate) (PCT).

In particular embodiments, polypropylene-based thermoplastic are used in the core of the bicomponent fibers of the present invention. The polypropylene-based thermoplastics may include propylene homopolymer, or a copolymer of propylene, or some mixture of propylene homopolymers and copolymers. In certain embodiments, the polypropylene described herein is predominately crystalline, thus the polypropylene may have a melting point (Tm) greater than <NUM> or <NUM> or <NUM>. The term "crystalline," as used herein, characterizes those polymers which possess high degrees of inter-and intra-molecular order. In certain embodiments the polypropylene has a heat of fusion (Hf) greater than <NUM> J/g or <NUM> J/g or <NUM> J/g, as determined by Differential Scanning Calorimetry (DSC) analysis. The Hf is dependent on the composition of the polypropylene; the thermal energy for the highest order of polypropylene is estimated at <NUM> J/g that is, <NUM>% crystallinity is equal to a Hf of <NUM> J/g. A polypropylene homopolymer will have a higher HHf than a copolymer or blend of homopolymer and copolymer.

In certain embodiments, the polypropylene(s) can be isotactic. Isotacticity of the propylene sequences in the polypropylenes can be achieved by polymerization with the choice of a desirable catalyst composition. The isotacticity of the polypropylenes as measured by <NUM>C NMR, and expressed as a meso diad content is greater than <NUM>% (meso diads [m]><NUM>) or <NUM> % or <NUM> % or <NUM> % in certain embodiments, determined as in <CIT> by <NUM>C NMR. Expressed another way, the isotacticity of the polypropylenes as measured by <NUM>C NMR, and expressed as a pentad content, is greater than <NUM> % or <NUM> % or <NUM> % in certain embodiments.

The polypropylene can vary widely in composition. For example, in certain embodiments, substantially isotactic polypropylene homopolymer or in other embodiments propylene copolymer containing equal to or less than <NUM> wt% of other monomer, that is, at least <NUM> wt% propylene can be used. Further, the polypropylene can be present in the form of a graft or block copolymer, in which the blocks of polypropylene have substantially the same stereoregularity as the propylene-based elastomer described herein so long as the graft or block copolymer has a sharp melting point above <NUM> or <NUM> or <NUM>, characteristic of the stereoregular propylene sequences.

In one or more embodiments, the polypropylene can be a combination of homopolypropylene, and/or random, and/or block copolymers. When the polypropylene is a random copolymer, the percentage of the α-olefin derived units in the copolymer is, in general, up to <NUM> wt% of the polypropylene, <NUM> wt% to <NUM> wt% in another embodiment, and <NUM> wt% to <NUM> wt% in yet another embodiment. In certain embodiments, the comonomer derived from ethylene or α-olefins containing <NUM> to <NUM> carbon atoms. One, two or more comonomers can be copolymerized with propylene. Exemplary α-olefins may be selected from the group consisting of: ethylene; <NUM>-butene; <NUM>-pentene-<NUM>-methyl-<NUM>-pentene-<NUM>-methyl-<NUM>-butene; <NUM>-hexene-<NUM>-methyl-<NUM>-pentene-<NUM>-methyl-<NUM>-pentene-<NUM>,<NUM>-dimethyl-<NUM>-butene; <NUM>-heptene; <NUM>-hexene; <NUM>-methyl-<NUM>-hexene; dimethyl-<NUM>-pentene; trimethyl-<NUM>-butene; ethyl-<NUM>-pentene; <NUM>-octene; methyl-<NUM>-pentene; dimethyl-<NUM>-hexene; trimethyl-<NUM>-pentene; ethyl-<NUM>-hexene; <NUM>-methylethyl-<NUM>-pentene; <NUM>-diethyl-<NUM>-butene; propyl-<NUM>-pentene; <NUM>-decene; methyl-<NUM>-nonene; <NUM>-nonene; dimethyl-<NUM>-octene; trimethyl-<NUM>-heptene; ethyl-<NUM>-octene; methylethyl-<NUM>-butene; diethyl-<NUM>-hexene; <NUM>-dodecene; and <NUM>-hexadodcene.

In one or more embodiments, the weight average molecular weight (Mw) of the polypropylene can be between <NUM>,<NUM>/mol to <NUM>,<NUM>,<NUM>/mol, or from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol in another embodiment, with a molecular weight distribution (MWD, Mw/Mn) within the range from <NUM> to <NUM>; or <NUM> to <NUM>; or <NUM> to <NUM>. The polypropylene can have an MFR (<NUM>/<NUM>) ranging of from <NUM> dg/min to <NUM> dg/min; or <NUM> dg/min to <NUM> dg/min; or <NUM> dg/min to <NUM> dg/min; or <NUM> dg/min to <NUM> dg/min.

The term "random polypropylene" ("RCP") as used herein broadly means a single phase copolymer of propylene having up to <NUM> wt%, or <NUM> wt% to <NUM> wt% of an alpha olefin comonomer. Exemplary alpha olefin comonomers have <NUM> carbon atoms, or from <NUM> to <NUM> carbon atoms. In certain embodiments, the alpha olefin comonomer is ethylene.

The propylene impact copolymers ("ICP") is heterogeneous and can include a first phase of <NUM> to <NUM> wt% homopolypropylene and a second phase of from <NUM> wt% to <NUM> wt% ethylene-propylene rubber, based on the total weight of the impact copolymer. The propylene impact copolymer can include <NUM> wt% to <NUM> wt% homopolypropylene and from <NUM> wt% to <NUM> wt% ethylene-propylene rubber, based on the total weight of the impact copolymer. In certain embodiments, the impact copolymer can include from <NUM> wt% to <NUM> wt% homopolypropylene and from <NUM> wt% to <NUM> wt% ethylene-propylene rubber, based on the total weight of the impact copolymer.

There is no particular limitation on the method for preparing the polypropylenes described herein. However, for example, the polymer is a propylene homopolymer obtained by homopolymerization of propylene in a single stage or multiple stage reactor. Copolymers may be obtained by copolymerizing propylene and ethylene or an α-olefin having from <NUM> to <NUM> carbon atoms in a single stage or multiple stage reactor. Polymerization methods include, but are not limited to, high pressure, slurry, gas, bulk, or solution phase, or a combination thereof, using any suitable catalyst such as traditional Ziegler-Natta catalyst or a single-site, metallocene catalyst system, or combinations thereof including bimetallic (i.e., Ziegler-Natta and metallocene) supported catalyst systems.

Exemplary commercial polypropylenes include the family of Achieve™ polymers (ExxonMobil Chemical Company, Baytown, Tex. The Achieve polymers are produced using metallocene catalyst systems. In certain embodiments, the metallocene catalyst system produces a narrow molecular weight distribution polymer. The MWD is typically in the range of <NUM> to <NUM>. However, a broader MWD polymer may be produced in a process with multiple reactors. Different MW polymers can be produced in each reactor to broaden the MWD. Achieve polymer such as Achieve <NUM>, a homopolymer having an MFR of <NUM> dg/min can be used as a blend component described herein. Alternatively, an Achieve polymer such as Achieve 6936G1, a <NUM> dg/min MFR homopolymer, can be used as a blend component described herein. Other polypropylene random copolymer and impact copolymer may also be used. The choice of polypropylene MFR can be used as means of adjusting the final MFR of the blend, especially the facing layer composition. Any of the polypropylenes described herein can be modified by controlled rheology to improve spinning performance as is known in the art.

In one or more embodiments, one or more additives may be incorporated into the sheath, the core, or both the core and the sheath. These additives may include, but are not limited to, stabilizers, antioxidants, fillers, colorants, nucleating agents, dispersing agents, mold release agents, slip agents, fire retardants, plasticizers, pigments, vulcanizing or curative agents, vulcanizing or curative accelerators, cure retarders, processing aids, tackifying resins, and the like. Other additives may include fillers and/or reinforcing materials, such as carbon black, clay, talc, calcium carbonate, mica, silica, silicate, combinations thereof, and the like. The antioxidants may include primary and secondary antioxidants such as, for example, hindered phenols, hindered amines, and phosphates. Nucleating agents may include, for example, sodium benzoate and talc. Also, to improve crystallization rates, other nucleating agents may also be employed such as Ziegler-Natta olefin products or other highly crystalline polymers. Other additives such as dispersing agents, for example, Acrowax C, can also be included. Slip agents include, for example, oleamide and erucamide. Catalyst deactivators are also commonly used, for example, calcium stearate, hydrotalcite, and calcium oxide, and/or other acid neutralizers known in the art.

In one or more embodiments, the bicomponent fibers of the present invention may be prepared in a melt-spun process (i.e. meltspinning), which is a process that extrudes polymeric melts or solutions through spinnerets to form filaments, which may also be referred to as monofilaments. The monofilaments may be formed into a fabric through various techniques including, but not limited to, spunbonding, meltblowing, flash spinning, coforming. In one or more embodiments, the fibers may be stable fibers that are carded.

In one or more embodiments, the sheath-core fibers of the present invention are prepared by a melt-spun process where two polymer liquids are separately supplied to spinneret orifices and then extruded to form the sheath-core structure. In the case of concentric monofilaments, the orifice supplying the core polymer is in the center of the spinning orifice outlet and flow conditions of core polymer fluid are strictly controlled to maintain the concentricity of both components when spinning. Eccentric fiber production can include eccentric positioning of the inner polymer channel and controlling of the supply rates of the two component polymers. Alternatively, a varying element can be introduced near the supply of the sheath component melt. Alternatively, a stream of single component can be merged with a concentric sheath-core component just before emerging from the orifice. Or, spun concentric fiber can be deformed by passing over a hot edge.

In one or more embodiments, the melt-spun process for preparing the bicomponent fibers of the present invention includes formation of a fabric by a spunbonding process. Following extrusion through a spinneret (i.e. meltspinning), the filaments can be quenched with air at a low temperature, drawn, usually pneumatically, and deposited on a moving mat, belt or "forming wire" to form the nonwoven fabric. See, for example, in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>. The skilled person understands that process conditions can be altered to tailor fiber and fabric properties. For example, increasing the polymer molecular weight or decreasing the processing temperature results in larger diameter fibers. Changes in the quench air temperature and pneumatic draw pressure also have an affect on fiber diameter.

In one or more embodiments, the melt-spun process for preparing the bicomponent fibers of the present invention includes formation of a fabric by a co-forming process. Following extrusion through a spinneret (i.e. meltspinning), other materials are added to the fabric either within the die or at or near the exit of the die. These other materials may include, but are not limited to, pulp, superabsorbent particles, cellulose or staple fibers. Co-forming processes are described in <CIT> and <CIT>.

In one or more embodiments, the use of the propylene-based elastomer to form the sheath as described herein provides for a process characterized by advantageous meltspinning speed, which is also referred to as spinning speed, which is measured in distance per unit of time (e.g. meters per minute "m/min') at a given throughput, which is conventionally measured in grams per hole per minute ("ghm"). In one or more embodiments, the fibers of the present invention can be meltspun, at a throughput of <NUM> ghm, at a maximum speed that is greater than <NUM>/min, in other embodiments greater than <NUM>/min, and in other embodiments greater than <NUM>/min. In these or other embodiments, the fibers of the present invention can be meltspun, at a throughput of <NUM> ghm, at a maximum speed that is greater than <NUM>/min, in other embodiments greater than <NUM>/min, and in other embodiments greater than <NUM>/min. In one or more embodiments, fiber production can take place by employing a pack pressure that is less than <NUM> psi, in other embodiments less than <NUM> psi, and in other embodiments less than <NUM> psi at <NUM> ghm.

As noted above, the bicomponent fiber may be used to prepare an air-through nonwoven fabric (i.e. a bonded fabric). In one or more embodiments, a nonwoven web of bicomponent fibers prepared according to this invention are subjected to an air-through bonding process to thereby thermally bond or set the fibers.

In one or more embodiments, the nonwoven fabrics prepared according to the present invention may be characterized by their initial sealing temperature, which may be determined according to ASTM F-<NUM>. The skilled person understands that the sealing temperature impacts the temperature that must be employed to bond the fibers in the preparation of bonded fabrics. In one or more embodiments, the nonwoven fabrics (and/or the fibers) of the present invention have an initial sealing temperature that is less than <NUM>, in other embodiments less than <NUM>, and in other embodiments less than <NUM>. In these or other embodiments, the nonwoven fabrics (and/or the fibers) have an initial sealing temperature that is greater than <NUM>, in other embodiments greater than <NUM>, and in other embodiments greater than <NUM>. In one or more embodiments, the nonwoven fabrics (and/or the fibers) have an initial sealing temperature that is from about <NUM> to about <NUM>, in other embodiments from about <NUM> to about <NUM>, and in other embodiments from about <NUM> to about <NUM>. Stated differently, in preparing bonded fabrics according to aspects of the present invention, the unbonded fabrics are subjected to air-bonding techniques where the temperature of the air is equivalent to the foregoing sealing temperatures.

In one or more embodiments, the nonwoven fabrics prepared using the bicomponent fiber may be characterized by their basis weight, which can be measured according to WSP (Worldwide Strategic Partners) <NUM> (<NUM>). In one or more embodiments, the nonwoven fabrics of the present invention may have a basis weight less than <NUM>/m<NUM>, in other embodiments less than <NUM>/m<NUM>, and in other embodiments less than <NUM>/m<NUM>. In these or other embodiments, the nonwoven fabric may have a basis weight greater than <NUM>/m<NUM>, in other embodiments greater than <NUM>/m<NUM>, and in other embodiments greater than <NUM>/m<NUM>. In one or more embodiments, the nonwoven fabric may have a basis weight from about <NUM>/m<NUM> to about <NUM>/m<NUM>, in other embodiments from about <NUM>/m<NUM> to about <NUM>/m<NUM>, and in other embodiments from about <NUM>/m<NUM> to about <NUM>/m<NUM>.

According to one or more embodiment of the invention, the fibers produced according to the process described here are formed into a nonwoven web of the fibers. This nonwoven web is then bonded by employing air-through bonding techniques to thereby form a bonded nonwoven. In one or more embodiments, the air-through bonding techniques include exposing the web to air having a temperature of less than <NUM> C°, in other embodiments less than <NUM> C°, in other embodiments less than <NUM> C°, and in other embodiments less than <NUM> C°. In one or more embodiments, the nonwoven web is exposed to air at temperatures of from about <NUM> to about <NUM> C°, in other embodiments from about <NUM> to about <NUM> C°, and in other embodiments from about <NUM> to about <NUM> C°.

Fabrics formed from the bicomponent fibers described herein may be a single layer, or may be multilayer laminates. In one or more embodiments, the fabric may include a laminate (or "composite") from meltblown fabric ("M") and spunbond fabric ("S"), which combines the advantages of strength from spunbonded fabric and greater barrier properties of the meltblown fabric. A typical laminate or composite has three or more layers, a meltblown layer(s) sandwiched between two or more spunbonded layers, or "SMS" fabric composites. Examples of other combinations are SSMMSS, SMMS, and SMMSS composites. Composites can also be made of the meltblown fabrics of the invention with other materials, either synthetic or natural, to produce useful articles.

Claim 1:
A bicomponent fiber comprising:
a sheath, where the sheath includes a propylene-based elastomer, said propylene-based elastomer including propylene-derived units and from about <NUM> to about <NUM> wt% alpha-olefin-derived units other than propylene-derived units, based upon the entire weight of the copolymer, said propylene-based elastomer having a triad tacticity of greater than <NUM>%, and a heat of fusion, as determined by DSC, of less than <NUM> J/g; and
a core, where the melt temperature of the core, is at least <NUM>% greater than the melt temperature of the sheath, wherein the melt temperature of the core and the melt temperature of the sheath are as determined by the differential scanning calorimetry (DSC) method referred to in the description, and are expressed
in °C.