Polyethylene compositions and related bicomponent fibers, nonwoven fabrics and methods

Abstract

The polyethylene copolymer may include a polyethylene of from about 90% to about 99.99% by weight of ethylene and from about 0.01% to about 10% by weight of a non-ethylene alpha-olefin, where the polyethylene has a density of from about 0.930 g / cm3 to about 0.955 g / cm3, a melt flow index (2.16 kg at 190 DEG C) of from about 10 g / 10 min to about 50 g / 10 min, a melt flow index ratio (MIR) of from 15 to 25, a weight average molecular weight to number average molecular weight ratio (Mw / Mn) of from about 2 to about 4, and a number average molecular weight (Mw / Mn) of from about 2 to about 4. The weight% of the TREF elution at a temperature of 90 DEG C and less is from about 10% to about 80% by weight, and the weight% of the TREF elution at a temperature of 95 DEG C and more is about 3% by weight or greater. The polyethylene is particularly suitable for the production of bicomponent fibers which can be used for the production of non-woven fabrics.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 366,315, filed on June 13, 2022, entitled “POLYETHYLENE COMPOSITIONS AND RELATED BICOMPONENT FIBERS, NONWOVEN FABRICS, AND METHODS,” the entire contents of which are incorporated herein by reference. Field of the Invention

[0003] The present disclosure relates to polyethylene, bicomponent fibers comprising polyethylene, nonwoven fabrics comprising bicomponent fibers, and methods relating to any of the foregoing.

[0004] background

[0005] Air-through bonded nonwovens are fabrics bonded by heat (usually hot air) using a process also known as air-through bonding. Air-through bonded nonwovens (which may also be referred to as air-through nonwovens) offer several benefits, including bulk, softness, and a good hand. These nonwovens are also beneficial because there are no chemical binders. Therefore, air-through nonwovens can be used to make a wide range of articles, especially disposable hygiene products such as diapers, sanitary napkins, training pants, and adult incontinence products.

[0006] Hot air nonwovens are routinely prepared by multi-layer fibers. Generally speaking, these multi-layer fibers include a core of a relatively high melting temperature polymer enclosed in a skin comprising a polymer with a relatively low melting temperature. Hot air is applied so that at least part of the skin is melted and the fibers are bonded to each other or heat-set thereby. Nonwoven fabrics to be applied with hot air bonding can be formed by various techniques (including carding, spunbonding, air-laid, thermal bonding, wet-laid and spunlace, etc.). Routinely, many hot air bonded nonwoven fabrics are prepared by the melt-spun nonwoven web of a multi-layer staple fiber web or a multi-layer fiber of a carding.

[0007] Multilayer fibers (also referred to as multicomponent fibers) are often prepared using a spinning process in which separate polymer streams are fed to a single die or spinneret to form fibers having two (or more) polymer phases. Although there are many structural variations of multicomponent fibers, sheath-core (or core-sheath) multicomponent fibers are often used to make air-through nonwoven fabrics, especially those used to make disposable hygiene products.

[0008] Polyethylene is a polymer that can be used in any part of the multicomponent fiber. For example, in a core-sheath bicomponent fiber, polyethylene can be used in the sheath and structurally contribute to bonding and physically contribute to the hand of the resulting nonwoven fabric.

[0009] For example, U.S. Pat. No. 7,300,988 discloses how to increase the catalyst productivity from 1000 grams of polymer / gram of catalyst (g / g) to about 5000 g / g by increasing the reactor pressure from about 300 psi to about 350 psi when using bis(n-propylcyclopentadienyl)hafnium dichloride and hafnium difluoride as catalysts. However, there is no discussion of molecular structure such as molecular distribution and short chain branching distribution, and furthermore, achieving this productivity requires low density polyethylene (0.918 g / cm 3 density), and furthermore results in very low melt index (MI) polyethylene (e.g., 0.69 g / 10 min), and a fairly high melt index ratio (MIR, ratio of high load melt index to melt index) of 31. The reference provides no guidance or suggestion for similarly achieving high catalyst productivity for higher density polymers of higher melt index as required for fiber applications.

[0010] In another example, U.S. Pat. No. 9,181,362 also discloses polyethylene produced by using a silica-supported bis(n-propylcyclopentadienyl) hafnium dichloride catalyst. By using a reactor temperature greater than 85°C and an operating pressure of about 300 psi to about 375 psi, the inventive polyethylene has a Mw / Mn greater than 3 and a unimodal short chain branching distribution according to a Temperature Ris ing Elution Fraction (TREF) curve. SUMMARY OF THE INVENTION

[0012] The present disclosure relates to polyethylene, bicomponent fibers comprising polyethylene, nonwoven fabrics comprising bicomponent fibers, and methods relating to any of the foregoing.

[0013] Non-limiting example compositions of the present disclosure include: a polyethylene comprising from about 90 wt% to about 99.99 wt% ethylene and from about 0.01 wt% to about 10 wt% of an alpha-olefin other than ethylene, wherein the polyethylene has: a density of about 0.930 g / cm 3 to about 0.955g / cm 3 , a melt flow index (2.16 kg at 190°C) of about 10 g / 10 min to about 50 g / 10 min, a melt flow index ratio (MIR) of about 15 to about 30, a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of about 2 to about 4, a weight % TREF eluted at 90°C and lower temperatures of about 10 weight % to about 80 weight %, and a weight % TREF eluted at 95°C and higher temperatures of about 3 weight % or greater.

[0014] A non-limiting process of the present disclosure comprises: polymerizing ethylene and non-ethylene alpha-olefins in the presence of a hafnocene catalyst in a fluidized bed gas reactor to produce polyethylene, wherein the reactor pressure is less than 300 psig, wherein the polyethylene comprises from 90 wt% to 99.99 wt% ethylene and from 0.01 wt% to about 10 wt% alpha-olefins, and wherein the polyethylene has: a density of about 0.930 g / cm 3 to about 0.955g / cm 3 , a melt index (2.16 kg at 190°C) of about 10 g / 10 min to about 50 g / 10 min, a melt index ratio (MIR) of about 15 to about 30, a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of about 2 to about 4, a TREF elution of about 10 wt% to about 80 wt% at 90°C and lower, and a TREF elution of about 3 wt% or greater at 95°C and higher.

[0015] A non-limiting example bicomponent fiber of the present disclosure comprises: a first polymer component comprising one or more of: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene, or polyetheretherketone; and a second polymer component comprising: a polyethylene comprising from about 90 wt % to about 99.99 wt % ethylene and from about 0.01 wt % to about 10 wt % of an alpha-olefin other than ethylene, wherein the polyethylene has: a density of about 0.930 g / cm 3 to about 0.955g / cm 3 , a melt flow index (2.16 kg at 190°C) of about 10 g / 10 min to about 50 g / 10 min, a melt index ratio (MIR) of about 15 to about 30, a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of about 2 to about 4, a weight % TREF eluted at 90°C and lower temperatures of about 10 weight % to about 80 weight %, and a weight % TREF eluted at 95°C and higher temperatures of about 3 weight % or greater.

[0016] Non-limiting example methods of the present disclosure include: melt spinning bicomponent fibers, wherein the bicomponent fibers comprise: a first polymer component comprising one or more of: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene, or polyetheretherketone; and a second polymer component comprising: polyethylene comprising from about 90 wt % to about 99.99 wt % ethylene and from about 0.01 wt % to about 10 wt % of an alpha-olefin other than ethylene, wherein the polyethylene has: a density of about 0.930 g / cm 3 to about 0.955g / cm 3, a melt flow index (2.16 kg at 190°C) of about 10 g / 10 min to about 50 g / 10 min, a melt index ratio (MIR) of about 15 to about 30, a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of about 2 to about 4, a weight percent TREF eluted at 90°C and below of about 10 weight percent to about 80 weight percent, and a weight percent TREF eluted at 95°C and above of about 3 weight percent or greater; cutting the bicomponent fibers into bicomponent staple fibers; producing a nonwoven fabric from the bicomponent staple fibers using a hot air bonding temperature of about 180°C or less.

[0017] These and other features and properties of the disclosed methods and compositions of the present disclosure and their advantageous applications and / or uses will be apparent from the following detailed description.

[0018] BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To aid those of ordinary skill in the relevant art in making and using the subject matter herein, reference is made to the accompanying drawings. The following drawings are included to illustrate certain aspects of the present disclosure and should not be construed as exclusive constructions. The disclosed subject matter is capable of significant modifications, alterations, combinations, and equivalences in form and function as will occur to those skilled in the art having the benefit of the present disclosure.

[0020] Figure 1 Here is a TREF comparison of some polyethylenes.

[0021] Figure 2 is a graph of the weight percent of polymer eluting below 90°C in a TREF experiment versus polymer density for various polyethylene polymers associated with the Examples.

[0022] Details

[0023] The present disclosure relates to polyethylene, comprises polyethylene bicomponent fiber, comprises the product of bicomponent fiber and with aforementioned any relevant method.More specifically, the present disclosure comprises the method and composition of producing polyethylene, and described polyethylene has the property that is converted into softer, more plush feeling nonwoven material when being used for producing bicomponent fiber and nonwoven fabric afterwards.In addition, polyethylene described herein can have the wide bonding temperature window that extends to lower temperature, when bonding, keeps the bond strength of fiber and fiber, and therefore keeps the mechanical property of nonwoven fabric.The wide bonding temperature window and the possibility of lower temperature advantageously improve manufacturing flexibility and can reduce the power consumption used for bonding in heated air.

[0024] Definition and test methods

[0025] Unless otherwise indicated, room temperature is 25°C.

[0026] "Olfin" or "alkene" is a linear, branched or cyclic carbon and hydrogen compound having at least one double bond.

[0027] "Polymer" has two or more identical or different monomer (mer) units. "Homopolymer" is a polymer having identical monomer units. The term "polymer" as used herein includes, but is not limited to, homopolymers, copolymers, terpolymers, etc. The term "polymer" as used herein also includes impact, block, graft, random and alternating copolymers. Unless otherwise specifically stated, the term "polymer" shall also include all possible geometric configurations. Such configurations may include isotactic, syndiotactic and random symmetries.

[0028] As used herein, unless otherwise specified, the term "copolymer(s)" refers to a polymer formed by the polymerization of at least two different monomers (i.e., monomer units). For example, the term "copolymer" includes copolymerization products of propylene and α-olefins such as ethylene, 1-hexene. A "terpolymer" is a polymer having three monomer units that are different from each other. Thus, the term "copolymer" also includes terpolymers and tetrapolymers such as copolymer products of a mixture of ethylene, propylene, 1-hexene, and 1-octene.

[0029] "Different" as used to refer to monomeric monomeric units means that the monomeric units differ from each other by at least one atom or are isomerically different. An "ethylene polymer" or "ethylene copolymer" is a polymer or copolymer comprising at least 50 mole % ethylene derived units, a "propylene polymer" or "propylene copolymer" is a polymer or copolymer comprising at least 50 mole % propylene derived units, and so forth. For purposes of the present invention, polyethylene is an ethylene polymer.

[0030] As used herein, when a polymer is referred to as "comprising, consisting of, or consisting essentially of a monomer," the monomer is present in the polymer in the polymerized / derivative form of the monomer. For example, when a copolymer is said to have an "ethylene" content of 35% to 55% by weight, it is understood that the monomer units in the copolymer are derived from ethylene in the polymerization reaction, and the derived units are present at 35% to 55% by weight based on the weight of the copolymer. Thus, a polymer or copolymer said to have a 90% by weight "ethylene" content is equivalent to a polymer or copolymer said to have a 90% by weight "ethylene-derived" content or 90% by weight "units derived from ethylene," etc.

[0031] Moment and distribution of molecular weight (Mw, Mn, Mz, Mw / Mn, Mz / Mn, etc.) and monomer / comonomer content (C2, C4, C6 and / or C8 and / or other, etc.) and g'(vis) are determined by using high temperature gel permeation chromatography (Polymer Char GPC-IR) equipped with an infrared detector IR5 based on a multi-channel bandpass filter, an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10 μm mixed-B LS columns are used to provide polymer separation. The detailed analysis principle and molecular weight determination method and g'(vis) are described in paragraphs

[0044] -

[0051] of PCT Publication WO2019 / 246069A1, which is incorporated herein by reference (note that the equation c= / / / mentioned in paragraph

[0044] about the concentration (c) at each point in the chromatogram is c=βI, where β is a mass constant and I is the IR5 broadband signal intensity (I) minus the baseline). Unless specifically mentioned, all molecular weight moments used or mentioned in this disclosure are determined according to the absolute determination method (such as mentioned in paragraphs

[0044] -

[0051] of the just-mentioned publication), noting that for the equation in such paragraph

[0044] , a=0.695 and K=0.000579 (1-0.75Wt) are used, where Wt is the weight fraction of the comonomer, and further noting that the comonomer composition is determined by the ratio of the IR5 detector intensities corresponding to the CH2 and CH3 channels calibrated with a series of PE and PP homo / copolymer standards, the nominal values ​​of which are predetermined by NMR or FTIR as indicated in paragraph

[0045] of the just-mentioned PCT publication (providing methyl groups / 1000 total carbons (CH3 / 1000TC)). Other parameters required can be found in the paragraphs mentioned in the WO2019 / 246069A1 publication, but for convenience some are included here: TCB at 145°C n = 1.500; I = 665nm; dn / dc = 0.1048mL / mg.

[0032] The density values ​​of the polymers were measured by the displacement method according to ASTM D1505-10.

[0033] Each melt flow index or melt index (MI) and high load melt index (HLMI) are measured on a Goettfert MI-4 melt indexer according to ASTM D1238-13, wherein the MI is measured at 190°C, 2.16 kg load (sometimes referred to as I2); and the HLMI is measured at 190°C, 21.6 kg load (sometimes referred to as I 21). Samples in an amount of 5 to 6 g were loaded into the barrel of the instrument at 190°C and compressed manually. Thereafter, the material was automatically compacted in the barrel by lowering all available weight onto the piston to remove all air bubbles. Data acquisition started after a 6 min pre-melting time.

[0034] The melt flow index ratio or melt index ratio (equivalently MFR or MIR) is the ratio HLMI / MI (or I 21 / I2).

[0035] The Broad Orthogonal Composition Distribution (BOCD) Index relates to short chain branching and is calculated according to PCT / US2021 / 072552, paragraph 0052, where it is referred to as the "Mn-Mz Comonomer Slope Index", which uses logMW = logMn as the low point and logMW = logMz as the high point for the slope determination. The Mn and Mz used in determining the BOCD Index are based on GPC absolute values.

[0036] Short chain branching per 1000 total carbons along the molecular weight (SCB / 1000C) is determined according to paragraph 0048 of PCT / US2021 / 072552, where SCB / 1000C = (comonomer weight %) * 140 / (comonomer molecular weight). So, for 1-hexene comonomer, SCB / 1000C = (comonomer weight %) * 140 / 84, and for 1-octene, SCB / 1000C = (comonomer weight %) * 140 / 112.

[0037] Temperature rising elution fractionation (TREF) is described in Monrabal, B. and del Hierro, P., Characterization of polypropylene-polyethylene blends by temperature rising elution and crystallization analysis fractionation, Analytic & Bioanalytic Chem. 399, 1557-1561 (Spr inger 2011), which is fully incorporated herein by reference. TREF analysis herein was performed on a CRYSTAF-TREF 200+ instrument from Polymer Char, SA, Valencia, Spain. Briefly, about 10 mg to 25 mg of sample was dissolved in 25 mL of o-dichlorobenzene (ODCB) while stirring at 150°C. A small volume (0.5 ml) of the solution was introduced into a column of an inert support equipped with a stainless steel ball at 150°C, and the column temperature was stabilized at 140°C for about 45 min. The sample volume is then crystallized in the column by lowering the temperature to 0°C at a cooling rate of 1°C / min. The column is maintained at a relatively low temperature and then an ODCB stream (1 mL / min) is injected into the column for 10 min to elute and measure the polymer (soluble fraction) that is not crystallized. The infrared detector (Polymer Char IR4) used produces an absorbance signal proportional to the concentration of the polymer in the elution stream. A complete TREF curve is then produced by increasing the column temperature from a relatively low temperature to 140°C at a rate of 2°C / min while maintaining an ODCB stream of 1 mL / min to elute and measure the dissolved polymer. The TREF peak elution temperature is defined as the temperature at the maximum dW / dT ([wt %] / °C). The TREF 50 wt % elution temperature is defined as the temperature at which a cumulative 50 wt % composition has been eluted.

[0038] Polyethylene and Polyethylene Synthesis

[0039] The present disclosure includes a method of producing polyethylene, which may include polymerizing ethylene and a non-ethylene alpha-olefin in the presence of a hafnocene catalyst. During the polymerization, an activator and / or hydrogen may also be present.

[0040] The hafnium cyclopentadienyl catalyst is a hafnium transition metal metallocene type catalyst system as described in U.S. Pat. No. 6,242,545 and / or U.S. Pat. No. 6,248,845, which are incorporated by reference. Non-limiting examples of hafnium cyclopentadienyl catalysts include, but are not limited to, bis(n-propylcyclopentadienyl) hafnium dichloride; bis(n-propylcyclopentadienyl) dimethyl hafnium; bis(n-propylcyclopentadienyl) hafnium dihydride; bis(n-butylcyclopentadienyl) hafnium dichloride; bis(n-butylcyclopentadienyl) dimethyl hafnium; bis(n-pentylcyclopentadienyl) hafnium dichloride; bis(n-pentylcyclopentadienyl) dimethyl hafnium; (n-propylcyclopentadienyl)(n-butylcyclopentadienyl) hafnium dichloride; (n-propylcyclopentadienyl)(n-butylcyclopentadienyl) bis(trimethylsilylcyclopentadienyl) hafnium dichloride; bis(trimethylsilylcyclopentadienyl) hafnium dimethyl chloride; bis(trimethylsilylcyclopentadienyl) hafnium dichloride; bis(trimethylsilylcyclopentadienyl) hafnium dimethyl chloride; bis(trimethylsilylcyclopentadienyl) hafnium dihydride; bis(2-n-propylindenyl) hafnium dichloride; bis(2-n-propylindenyl) hafnium dimethyl chloride; bis(2-n-butylindenyl) hafnium dichloride Hafnium; bis(2-n-butylindenyl) dimethyl hafnium, dimethylsilylbis(n-propylcyclopentadienyl) hafnium dichloride; dimethylsilylbis(n-propylcyclopentadienyl) hafnium dimethyl; dimethylsilylbis(n-butylcyclopentadienyl) hafnium dichloride; dimethylsilylbis(n-butylcyclopentadienyl) hafnium dimethyl; bis(9-n-propylfluorenyl) hafnium dichloride; bis(9-n-propylfluorenyl) dimethyl hafnium; bis(9-n-butylfluorenyl) hafnium dichloride; bis(9-n-butylfluorenyl) dimethyl hafnium ; (9-n-propylfluorenyl)(2-n-propylindenyl) hafnium dichloride; (9-n-propylfluorenyl)(2-n-propylindenyl) hafnium dimethyl; bis(1,2-n-propyl, methylcyclopentadienyl) hafnium dichloride; bis(1,2-n-propyl, methylcyclopentadienyl) hafnium dimethyl; (n-propylcyclopentadienyl)(1,3-n-propyl, n-butylcyclopentadienyl) hafnium dichloride; (n-propylcyclopentadienyl)(1,3-n-propyl, n-butylcyclopentadienyl) hafnium dimethyl, etc.; and any combination thereof.

[0041] The activator that can be used in conjunction with the hafnocene catalyst can include Lewis acid or non-coordinating ion activator or ionizing activator or any other compound that can convert the neutral metallocene catalyst component into a metallocene cation. Examples of activators that can be used in conjunction with the hafnocene catalyst can include, but are not limited to, aluminoxanes, modified aluminoxanes, tri(n-butyl)aluminum tetra(pentafluorophenyl)boron metalloid precursors, triperfluorophenylboron metalloid precursors, etc., and any combination thereof. Additional disclosures about activators can be found in U.S. Pat. No. 6,242,545 and / or U.S. Pat. No. 6,248,845, which are incorporated by reference.

[0042] The hafnocene catalyst and / or activator may be supported on a support material such as a porous support material (e.g., talc, an inorganic oxide, an inorganic chloride and / or magnesium chloride), a resinous support material (e.g., polystyrene or polystyrene divinyl benzene polyolefin or polymer compound) or any other organic or inorganic support material, and any combination thereof. Additional disclosure regarding support materials may be found in U.S. Pat. No. 6,242,545 and / or U.S. Pat. No. 6,248,845, which are incorporated by reference.

[0043] The molar ratio of the metal of the activator component to the transition metal of the metallocene component is in a ratio range of between 0.3: 1 to 1000: 1, preferably 20: 1 to 800: 1, and most preferably 50: 1 to 500: 1. When the activator is an aluminum-free ionizing activator such as those based on the anion tetrakis(pentafluorophenyl)boron, the molar ratio of the activator component to the metal of the transition metal component is preferably in a ratio range of between 0.3: 1 to 3: 1.

[0044] The hafnocene catalyst can have a catalyst productivity of about 7,000 grams of polymer / gram of hafnocene catalyst (g / g) or greater (or about 7,000 g / g to about 12,000 g / g, or about 7,000 g / g to about 10,000 g / g, or about 7,000 g / g to about 9,000 g / g).

[0045] Hafnium bis(oxadiazole) catalyst can be used for polymerizing ethylene and non-ethylene alpha-olefins. Such alpha-olefins can be olefins with 3 to 30 carbon atoms (or 3 to 12 carbon atoms or 3 to 8 carbon atoms). Examples of such alpha-olefins can include but are not limited to propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, etc. or any combination thereof. Preferred alpha-olefins include 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

[0046] The polymerization process of the present disclosure is preferably a fluidized bed gas process. Typically, the monomer stream is passed through a polymerization section. As an illustration of the polymerization section, a fluidized bed gas phase reactor (also referred to herein as a "reactor") in fluid communication with one or more discharge tanks, a buffer tank, a purge tank, and a recycle compressor may be included. The reactor may include a reaction zone in fluid communication with a velocity reduction zone. The reaction zone includes a bed of growing polymer particles, formed polymer particles, and catalyst composition particles, and the bed is fluidized by continuously flowing through the reaction zone with polymerizable and modified gaseous components in the form of supplementary feed and recycle fluid. Preferably, the supplementary feed includes polymerizable monomers, most preferably ethylene and at least one other alpha-olefin, and may also include a "condensing agent", as known in the art and disclosed in, for example, U.S. Patent Nos. 4,543,399, 5,405,922, and 5,462,999.

[0047] The fluidized bed has the general appearance of densely packed individually moving particles, preferably polyethylene particles, produced by gas permeation through the bed. The pressure drop through the bed is equal to or slightly greater than the weight of the bed divided by the cross-sectional area. It therefore depends on the geometry of the reactor. In order to maintain a viable fluidized bed in the reaction zone, the superficial gas velocity through the bed must exceed the minimum flow required for fluidization. Preferably, the superficial gas velocity is at least twice the minimum flow velocity. Typically, it is sufficient for the superficial gas velocity to be no more than 1.5 m / sec and often no more than 0.76 ft / sec.

[0048] Monomers (e.g., ethylene and alpha-olefins) can be introduced in a variety of ways including direct injection into the bed or into the recycle gas line through nozzles. Monomers can also be sprayed into the top of the bed through nozzles located above the bed, which can help eliminate some carryover of fines with the recycle gas stream.

[0049] The reactor temperature (also referred to as bed temperature) of the fluidized bed processes described herein can be about 70°C to about 110°C (or about 70°C to about 80°C, or about 70°C to about 85°C, or about 75°C to about 90°C, or about 80°C to about 100°C).

[0050] The reactor pressure of the fluidized bed process described herein can be about 300 psig or less (or about 100 psig to about 300 psig, or about 100 psig to about 290 psig, or about 100 psig to about 275 psig, or about 100 psig to about 200 psig, or about 200 psig to about 300 psig).

[0051] The α-olefin should be present at a level that will achieve the desired weight percent incorporation of the α-olefin into the final polyolefin.

[0052] Hydrogen may also be added to the polymerization reactor(s) to control the final properties of the polyethylene composition (e.g., melt flow index, melt flow ratio, bulk density, etc.). By way of non-limiting example, the ratio of hydrogen to total ethylene monomer in the recycled gas stream (ppm H2:mol% C2) may be in the range of 0 to about 60:1 (or about 0.10:1 (0.10) to about 50:1 (50), or about 0.12 to about 40, or about 0.15 to about 35).

[0053] The polyethylene of the present disclosure may comprise about 90 wt % to about 99.99 wt % (or about 90 wt % to about 95 wt %, or about 95 wt % to about 99.99 wt %, or about 93 wt % to about 98 wt %, or about 97 wt % to about 99 wt %, or about 99 wt % to about 99.99 wt %) of ethylene and about 0.01 wt % to about 10 wt % (or about 5 wt % to about 10 wt %, or about 0.01 wt % to about 5 wt %, or about 2 wt % to about 7 wt %, or about 1 wt % to about 3 wt %, about 0.01 wt % to about 1 wt %) of non-ethylene α-olefins.

[0054] The polyethylene of the present disclosure may have a density of about 0.930 or 0.931 g / cm 3 to about 0.950, 0.953 or 0.955 g / cm 3 (or about 0.930g / cm 3 To about 0.950g / cm 3 , or about 0.930g / cm 3 To about 0.945g / cm 3 , or about 0.930g / cm 3 To about 0.940g / cm 3 ).

[0055] The polyethylene of the present disclosure may have a melt flow index (measured at 190°C and 2.16 kg load) of about 10 g / 10 min to about 50 g / 10 min (or about 10 g / 10 min to about 40 g / 10 min, or about 10 g / 10 min to about 30 g / 10 min, or about 10 g / 10 min to about 25 g / 10 min).

[0056] The polyethylene of the present disclosure can have a melt index ratio (MIR) of about 12, 13, 14 or 15 to about 20, 22, 25, 27 or 30 (wherein ranges from any of the foregoing lower ends to any of the foregoing upper ends are contemplated, e.g., 15 to 25, or 15 to 20, or 15 to 30).

[0057] The polyethylene of the present disclosure may have a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of about 2 to about 4 (or about 2 to about 3, or about 2.0 to about 2.9, or about 2 to about 3.5, or about 2.5 to about 3.5).

[0058] The polyethylenes of the present disclosure may have a g'(vis) of about 0.95 or greater (or about 0.95 to about 1.0).

[0059] The polyethylene of the present disclosure can have a weight % TREF elution at 90°C and lower of about 10 wt% to about 80 wt% (or about 10 wt% to about 30 wt%, or about 25 wt% to about 50 wt%, or about 30 wt% to about 60 wt%, or about 50 wt% to about 80 wt%), wherein ranges from any of the foregoing lower ends to any of the foregoing upper ends (e.g., 25 to 60 wt%) are also contemplated herein.

[0060] The polyethylene of the present disclosure can have a wt % TREF elution at 95°C and above of about 3 wt % or greater (or about 5 wt % or greater, or about 3 wt % to about 85 wt %, or about 5 wt % to about 85 wt %, or about 3 wt % to about 35 wt %, or about 5 wt % to about 25 wt %, or about 10, 15 or 20 wt % to about 50, 55, 60, 70, 80 or 85 wt %), wherein ranges from any of the foregoing lower ends to any of the foregoing upper ends (e.g., 5 to 35 wt % or 5 to 60 wt %) are also contemplated herein.

[0061] Typically, the lower density fraction of polyethylene has a higher comonomer content and is eluted at a lower temperature by TREF, while the higher density fraction of polyethylene has a lower comonomer content and is eluted at a higher temperature by TREF. Without being bound by theory, it is believed that the lower density fraction broadens the bonding temperature window and the higher density fraction improves the bonding strength. Advantageously, the polyethylene of the present disclosure can have a low density fraction (e.g., illustrated by having a weight % of TREF eluted at 90° C. and lower temperatures of about 10 weight % to about 80 weight %) and a high density fraction (e.g., illustrated by having a weight % of TREF eluted at 95° C. and higher temperatures of about 3 weight % or greater).

[0062] The polyethylene of the present disclosure may have a TREF peak elution temperature greater than the TREF 50 wt% elution temperature.

[0063] The polyethylene of the present disclosure may have a BOCD index (or Mn-Mz comonomer slope index) greater than about 2, 3, or 4 (or about 2 to about 7, or about 2 to about 5, or about 3 to about 5) in various embodiments. In some embodiments, a BOCD index greater than 2, 3, or 4 (i.e., a higher BOCD index) may be associated with a lower density species of polyethylene (e.g., having a density of 0.945 g / cm 3 or smaller, such as 0.940 g / cm 3 or less), while for higher densities (e.g., greater than 0.945 g / cm 3 , for example 0.950g / cm 3 or greater), the BOCD index may be less than 2, for example less than 1.

[0064] As discussed in more detail in conjunction with the examples below, the polyethylenes of the present disclosure exhibit the unique feature of the adjustability of their low density fraction relative to the high density fraction as a function of density (comonomer incorporation). In particular, the polyethylenes of the present disclosure (having a density of 0.930 to 0.955 g / cm 3 , or within other narrower ranges as discussed above) can follow the relationship Y>-3000X+2865, where Y is the weight % TREF eluted at 90°C and below; and X is the density of the polyethylene (g / cm 3 ). This quantifies the phenomenon that allows for the tailorability of the polyethylene - whereby increased comonomer incorporation (lower density) is selectively performed in the lower density fraction of the polyethylene (rather than equally throughout both the lower and higher density fractions), such that as density decreases (increases comonomer incorporation), comonomer is significantly preferentially incorporated into the low density fraction. Importantly, the polyethylenes according to such embodiments still possess a suitable high density fraction, as demonstrated by their having a wt% TREF eluting at 95°C and above of at least 3 wt%, preferably at least 5 wt% (or any other range of wt% TREF eluting at 95°C described herein).

[0065] Bicomponent Fibers

[0066] The bicomponent fibers of the present disclosure may include a first polymer component and a second polymer component, wherein one of the polymer components includes the polyethylene of the present disclosure. Examples of polymers that may be used in or as the other polymer component may include, but are 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 TM , maleic anhydride functionalized elastomers, ethylene copolymers), plastomers (e.g., ethylene-α-olefin copolymers), polyurethanes, polyesters such as polyethylene terephthalate, polylactic acid, polyvinyl chloride, polytetrafluoroethylene, styrenic block copolymers, ethylene vinyl acetate copolymers, polyamides, polycarbonates, cellulosics (e.g., RAYON TM LYOCELL TM TENCIL TM), elastomers, poly(acetylene), poly(thiophene), poly(aniline), poly(fluorene), poly(pyrrole), poly(3-alkylthiophene), poly(phenylene sulfide), polynaphthalene, poly(phenylene vinylene), poly(vinylidene fluoride), poly(oxyethylene glycol) polymers (POP), polyoxymethylene (POM), polyetheretherketone (PEEK), and blends of any two or more of these materials. Useful polymers also include plastomers (e.g., ethylene-α-olefin copolymers and block copolymers), polyurethanes, polyesters such as polyethylene terephthalate (PET), polylactic acid, polyvinyl chloride, polytetrafluoroethylene, styrenic block copolymers, ethylene vinyl acetate copolymers, polyamides, polycarbonates, cellulosics (e.g., RAYON TM LYOCELL TM TENCIL TM ), elastomers, poly(acetylene), poly(thiophene), poly(aniline), poly(fluorene), poly(pyrrole), poly(3-alkylthiophene), poly(phenylene sulfide), polynaphthalene, poly(phenylene vinylene), poly(vinylidene fluoride), etc., and blends of any two or more of these materials. Preferred polymers include, but are not limited to, polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymers, polyoxymethylene, polyetheretherketone, etc., and any blends thereof.

[0067] One or more additives may be incorporated into the first polymer component and / or the second polymer component. Examples of additives may include, but are not limited to, stabilizers, antioxidants, fillers, colorants, nucleators, dispersants, mold release agents, slip agents, flame retardants, plasticizers, pigments, vulcanization or curing agents, vulcanization or curing accelerators, curing retardants, processing aids, tackifying resins, etc., and any combination thereof. Other additives may include fillers and / or reinforcing materials, such as carbon black, clay, talc, calcium carbonate, mica, silicon dioxide, silicates, etc., and any combination thereof.

[0068] The antioxidants may be primary and secondary antioxidants. Examples of antioxidants may include, but are not limited to, hindered phenols, hindered amines, phosphate esters, and the like, and any combination thereof.

[0069] The bicomponent fibers of the present disclosure can be prepared in a melt spinning process (also referred to as melt spinning), which is a process in which a polymer melt or solution is extruded through a spinneret to form filaments (also referred to as monofilaments).

[0070] The bicomponent fiber can have a side-by-side configuration or a core-sheath configuration. In a core-sheath configuration, the polyethylene of the present disclosure can be either in the core or in the sheath. Preferably, the polyethylene of the present disclosure is in the sheath of a core-sheath bicomponent fiber configuration.

[0071] In one or more embodiments, the sheath-core fibers of the present invention are prepared by a melt spinning process, wherein two polymer liquids are supplied separately to the spinneret holes and then extruded to form a sheath-core structure. In the case of concentric monofilaments, the hole for supplying the core polymer is at the center of the spinning hole outlet and the flow conditions of the core polymer fluid are strictly restricted to maintain the concentricity of the two components during spinning. Eccentric fiber production may include eccentric placement of the inner polymer channel and control of the supply rate of the two component polymers. Alternatively, different elements may be introduced near the supply of the sheath component melt. Alternatively, the single component stream may merge with the concentric sheath-core component just before exiting the hole. Alternatively, the spinning concentric fiber may be deformed by passing through a hot edge.

[0072] The bicomponent fibers may optionally be stretched (eg, using high speed air and / or rollers) to reduce the diameter of the bicomponent fibers.

[0073] The bicomponent fibers may be optionally treated with a hydrophobic agent or a hydrophilic agent to coat at least a portion of the surface of the bicomponent fibers. The agent may be applied by spraying or other suitable techniques.

[0074] The bicomponent fibers described herein can have a diameter of from about 1 micron to about 15 microns (or from about 1 micron to about 10 microns, or from about 2 microns to about 7 microns).

[0075] The bicomponent fibers may have an elongation at break of about 50% or greater (or about 50% to about 90%, or about 55% to about 75%, or about 60% to about 80%).

[0076] The bicomponent fibers may have a breaking force of about 2 cN / dtex to about 4 cN / dtex (or about 2 cN / dtex to about 3 cN / dtex).

[0077] The bicomponent fibers can be directly formed into the nonwoven fabrics of the bicomponent fibers described herein by spunbond technology. Alternatively, the bicomponent fibers can be cut into staple fibers and formed into the nonwoven fabrics of the bicomponent fibers described herein by hot air technology.

[0078] In melt spinning technology, nonwoven fabrics can be produced by spunbond technology. Conventionally, for example, spunbond fibers are produced by either extruding molten polymers (for example, using melt spinning conditions described above) from a large spinneret with thousands of holes or using a smaller spinneret in rows that for example contains as few as 40 holes. After leaving the spinneret, the molten fiber is quenched by a cross-flow air quenching system, then pulled out from the spinneret and attenuated (pulled) by high-speed air. The filaments formed in this way are collected on a wire mesh (" line ") or a porous forming belt to form a net. The net is then passed through a press roll, and then between the calender rolls of heating, the raised area on one of the rollers is bonded to form a nonwoven fabric at 10% to 40% of the point covering its area.

[0079] In the through-air technique, the bicomponent fibers can be processed to produce staple fibers. The processing steps can include (a) crimping and cutting the bicomponent fibers into bicomponent staple fibers or (b) cutting the bicomponent fibers into bicomponent staple fibers. The bicomponent staple fibers can have a length of about 10 mm to about 100 mm (or about 20 mm to about 80 mm, or about 30 mm to about 60 mm).

[0080] The nonwoven fabric of bicomponent staple fibers described herein can be formed by placing the bicomponent staple fibers on a forming belt, bulking the bicomponent staple fibers to form a web, and then subjecting the web to a through-air bonding process to thereby thermally bond or consolidate the fibers in the nonwoven fabric.

[0081] Hot air bonding techniques may use air having a temperature of about 180°C or less (or about 150°C to about 180°C, or about 155°C to about 175°C, or about 150°C to about 170°C, or about 155°C to about 160°C).

[0082] Nonwoven fabrics made using the bicomponent fibers described herein (e.g., made by melt spinning or through-air technology) can be characterized by basis weight, which can be measured according to WSP (Worldwide Strategic Partnership) 130.1 (05). The nonwoven fabric can have a basis weight of about 120 g / m 3 or less (or about 5g / m 3 About 120g / m 3 , or about 5g / m 3 About 50g / m 3 , or about 25g / m 3 About 100g / m 3 , or about 80g / m 3 About 120g / m 3 ).

[0083] Nonwoven fabrics made using the bicomponent staple fibers described herein can be characterized by gauge (or weight per square meter). The nonwoven fabric can have a gauge of about 50 g / m 2 or less (or about 5g / m 2 About 50g / m 2 , or about 5g / m 2 About 25g / m 2 , or about 10g / m 2 About 30g / m 2 , or about 25g / m 2 About 50g / m 2 ).

[0084] Unless otherwise indicated, all numerical values ​​used in this specification and the related claims expressing the amount of ingredients, properties such as molecular weight, reaction conditions, etc. should be understood as being modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters listed in the following specification and the appended claims are approximate values, which may vary depending on the desired properties sought to be obtained by the embodiment of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0085] One or more illustrative embodiments including one or more inventive elements are proposed herein. For the sake of clarity, all features of physical implementation are not described or shown in this application. It should be understood that in the development of physical implementations including one or more elements of the present invention, in order to achieve the developer's goal, many specific decisions must be made to achieve, for example, system-related, business-related, government-related and other constraints are observed, which change from time to time with the implementation. Although the developer's efforts may be time-consuming, such efforts are routine tasks for those of ordinary skill in the art who benefit from the present disclosure.

[0086] Although compositions and methods are described herein in terms of "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. In the context of compositions, consisting essentially of allows for 25 ppm or less (of each) of impurities.

[0087] Additional embodiments

[0088] Embodiment 1. A composition comprising: a polyethylene comprising from about 90 wt% to about 99.99 wt% ethylene and from about 0.01 wt% to about 10 wt% of an alpha-olefin other than ethylene, wherein the polyethylene has: a density of about 0.930 g / cm 3 to about 0.955g / cm 3 , a melt flow index (2.16 kg at 190°C) of about 10 g / 10 min to about 50 g / 10 min, a melt flow index ratio (MIR) of 15 to 25, a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of about 2 to about 4, a weight % TREF eluted at 90°C and lower temperatures of about 10 wt% to about 80 wt%, and a weight % TREF eluted at 95°C and higher temperatures of about 3 wt% or greater.

[0089] Embodiment 2. The composition of embodiment 1, wherein one or both of the following apply to the polyethylene: (a) the TREF peak elution temperature is greater than the TREF 50 wt% elution temperature; and / or (b) the polyethylene follows the comonomer incorporation relationship Y>-3000X+2865, where Y is the weight % of the polyethylene eluting at TREF at 90°C or less, and X is the density of the polyethylene (g / cm 3 ). Preferably, the polyethylene has both properties (a) and (b).

[0090] Embodiment 3. The composition of any of Embodiments 1-2, wherein Mw / Mn is from about 2 to about 3.

[0091] Embodiment 4. The composition of any one of Embodiments 1-3, wherein the density is about 0.930 g / cm 3 To about 0.945g / cm 3 .

[0092] Embodiment 5. The composition of any of Embodiments 1-4, wherein the polyethylene has a broad orthogonal composition distribution (BOCD) index greater than about 2.

[0093] Embodiment 6. The composition of any one of Embodiments 1-5, wherein the α-olefin is 1-hexene.

[0094] Embodiment 7. A method comprising: polymerizing ethylene and a non-ethylene α-olefin in the presence of a hafnocene catalyst in a fluidized bed gas reactor to produce polyethylene, wherein the reactor pressure is less than 300 psig, wherein the polyethylene comprises 90 wt% to 99.99 wt% ethylene and 0.01 wt% to about 10 wt% α-olefin, and wherein the polyethylene has: a density of about 0.930 g / cm 3 to about 0.955g / cm 3 , a melt index (2.16 kg at 190°C) of about 10 g / 10 min to about 50 g / 10 min, a melt index ratio (2.16 kg at 190°C to 21.6 kg at 190°C) of about 15 to about 30, a ratio of weight average molecular weight to number average molecular weight (Mw / Mn) of about 2 to about 4, a TREF elution of about 10 wt% to about 80 wt% at 90°C and lower, and a TREF elution of about 3 wt% or greater at 95°C and higher.

[0095] Embodiment 8. The process of Embodiment 7, wherein the α-olefin is 1-hexene.

[0096] Embodiment 9. The method of any one of Embodiments 7-8, wherein the reactor bed temperature is from about 70°C to about 80°C.

[0097] Embodiment 10. The method of any of Embodiments 7-9, wherein the catalyst productivity is about 7000 g / g or greater.

[0098] Embodiment 11. The method of any of Embodiments 7-10, wherein one or both of: (a) the polyethylene has a TREF peak elution temperature greater than the polyethylene's TREF 50 wt% elution temperature; and / or (b) the polyethylene follows a comonomer incorporation relationship Y>-3000X+2865, where Y is the polyethylene's weight % TREF elution at 90°C or less, and X is the polyethylene's density (g / cm 3 ). Preferably, the polyethylene has both properties (a) and (b).

[0099] Embodiment 12. The method of any one of Embodiments 7-11, wherein Mw / Mn is from about 2 to about 3.

[0100] Embodiment 13. The method of any one of Embodiments 7-12, wherein the density is about 0.930 g / cm 3 To about 0.945g / cm 3 .

[0101] Embodiment 14. The method of any of Embodiments 7-13, wherein the polyethylene has a broad orthogonal composition distribution (BOCD) index greater than about 2.

[0102] Embodiment 15. A bicomponent fiber comprising: a first polymer component comprising one or more of the following: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene or polyetheretherketone; and a second polymer component comprising the following: polyethylene of any of Embodiments 1-6.

[0103] Embodiment 16. The bicomponent fiber of Embodiment 15, wherein the bicomponent fiber has a core-sheath configuration, wherein the second polymer component serves as the sheath.

[0104] Embodiment 17. The bicomponent fiber of any of Embodiments 15-16, wherein the bicomponent fiber is a bicomponent staple fiber.

[0105] Embodiment 18. A method comprising: melt spinning the bicomponent fiber of any of Embodiments 15-16; cutting the bicomponent fiber into bicomponent staple fibers; and producing a nonwoven fabric from the bicomponent staple fibers using a hot air bonding temperature of about 180°C or less.

[0106] Embodiment 19. The method of Embodiment 18, wherein the through-air bonding temperature is from about 150°C to about 165°C.

[0107] Embodiment 20. The method of any of Embodiments 18-19 further comprises: stretching the bicomponent fibers before cutting the bicomponent fibers.

[0108] In order to facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are given. The following examples should in no way be construed as limiting or defining the scope of the present invention. Example

[0109] XCAT available from Univation Technologies contacted with MAO (methylaluminoxane) and supported on silica was used. TM VP-100 metallocene catalyst produced polyethylene compositions. Ethylene and 1-hexene were polymerized in a fluidized bed reactor in the presence of catalyst and hydrogen according to the conditions in Table 1 to produce polyethylene according to Table 2. Table 2 also includes a comparative polyethylene composition (CE) used in the control bicomponent fibers described below.

[0110] Table 1

[0111]

[0112]

[0113] Table 2

[0114]

[0115]

[0116] NM - Not Measured

[0117] The resulting polyethylene pellets were mixed with IRGONOX TM 3114 (sterically hindered phenolic antioxidant, available from BASF) and IRGOFOS TM 168 (a hydrolytically stable phosphite stabilizer available from BASF) was compounded. The final resin had 600 ppm IRGONOX TM 3114 and 1200ppm IRGOFOS TM 168.

[0118] Using conventional parameters known to those skilled in the art, a core-skin structure is used to produce bicomponent fibers, with polyethylene as the skin and polyethylene terephthalate (PET) as the core. Briefly summarized, the molten polymer is ejected from a spinning machine through a melt pump to produce filaments. Each spinning machine contains thousands of pinholes, each with a diameter of about several microns. Then, the filaments are collected together and passed through several heating elements (e.g., a water bath, a steam oven, a dryer). Finally, the filaments are solidified and cut into staple fibers.

[0119] Four types of bicomponent staple fibers were produced: (1) core PET with 2911FS (high density polyethylene, available from Fushun Petro Chemical) sheath, (2) core PET with IE1 sheath, (3) core PET with ASPUN TM 6000 (Linear Low Density Polyethylene, available from Dow) sheath and (4) core PET with IE2 sheath. 2911FS and ASPUN TM 6000 include antioxidants in their formulations. Various properties of the two polyethylenes used in comparative fiber production are provided in Table 3 along with properties of other polyethylene grades. Properties of four staple fiber samples are provided in Table 4.

[0120] Table 3

[0121]

[0122]

[0123] NM - Not Measured

[0124] EXCEED TM 0019XC - Ethylene 1-hexene copolymer, available from ExxonMobil ENABLE TM 4002 - medium density ethylene 1-hexene copolymer, available from ExxonMobil 7200F - high density polyethylene, available from Taisox

[0125] Table 4

[0126]

[0127]

[0128] *For bicomponent fibers, the nomenclature is sheath / / core.

[0129] First, comparing different polyethylenes (not as fibers), the melt flow index and density of the polyethylene of the present invention are similar to those of the comparative examples. However, surprisingly, (1) the polyethylene of the present invention has a lower Mw / Mn value, indicating a narrower molecular weight distribution, making it suitable for fiber spinning processes; and (2) the balance of high and low density fractions in the composition can be adjusted by density. The new and adjustable comonomer distribution is particularly useful for staple fiber applications.

[0130] As a supplement to Tables 2, 3 and 4, refer to Figure 1 , for comparison of TREF of some polyethylenes reported in Tables 2 and 3, and for further explanation of the balance of high and low density fractions in IE1 and IE2. In particular, Figure 1 It is shown that the inventive polyethylenes IE1 and IE2 have clear peaks in their TREF elutions, but the peaks are broadened, with a polymer portion eluting at 90°C and below and a polymer portion eluting at 95°C and above. For example, IE1 shows a very broad peak with a shoulder connected thereto, while IE2 shows a more distinct peak that also includes a shoulder spanning approximately 88°C-92°C. Figure 1 Compared to the other polymers described above, the two IE TREF curves indicate the presence of two different density fractions (i.e., a high density fraction and a low density fraction), with either essentially all of their eluting polymer being below 90°C (Exceed 0019XC) or almost no polymer eluting below 90°C (Enable 4002, 2911, 7200F). Another way to quantify this feature of the polymers of the present invention is by comparing the TREF Peak Elution Temperature relative to the TREF 50 wt% Elution Temperature, reminding that the TREF Peak Elution Temperature is defined as the temperature at the maximum dW / dT ([wt%] / °C), while the TREF 50 wt% elution temperature is defined as the temperature when 50 wt% of the composition has eluted cumulatively. Specifically, in these inventive polyethylenes, the TREF Peak Elution Temperature is greater than the TREF 50 wt% elution temperature, quantifying the peak elution temperature at the TREF 50 wt% elution temperature. Figure 1 The presence of a shoulder on the left side (lower temperature side) of each elution peak shown in IE1 and IE2.

[0131] exist Figure 1Comparison of IE1 and IE2 in Figure 1 highlights another surprising and useful feature: the adjustable balance of high density fractions and low density fractions based on the overall density. That is, as more comonomer is incorporated into the polymer chain of these inventive polyethylenes (i.e., the density decreases), as is the case when moving from IE2 to IE1, the comonomer is incorporated into different fractions of the polymer chain (thus the area under the TREF curve below 90°C in IE1 is increasingly larger than the area under the TREF curve below 90°C for IE2), rather than being evenly distributed along the polymer chain and completely losing the distinction between the fractions. This feature provides significant advantages, particularly in the bicomponent fiber space, where different higher and lower density fractions each provide important advantages.

[0132] For example, EXCEED TM 0019XC has a melt index of 19, which is comparable to IE1. However, reviewing the TREF data (see Figure 1 ), 99.8% by weight of EXCEED TM 0019XC eluted at a temperature below 92°C, indicating the lower melting point and lower temperature required for bonding the fibers. TM The fabric made from the bicomponent fibers of 0019XC is mechanically weak. The mechanical strength of the fibers and fabric is consistent with the low density of the resin. As seen below, the nonwoven fabric produced from the bicomponent fibers comprising IE1 has good mechanical strength, while the majority of the lower (temperature) eluting polymer (low density fraction) corresponds to a portion of the relatively lower melting polymer that is large enough to still enable the lower temperature bonding of IE1, even while maintaining this good mechanical strength.

[0133] ENABLE TM 4002 also has similar density as IE1, but ENABLE TM 4002 has a very narrow comonomer distribution as shown in the TREF graph. About 6.9% of the composition elutes at temperatures below 90°C and 10.3% of the composition elutes at temperatures above 95°C. ENABLE TM 4002 has a very narrow bonding temperature window, which can translate into weaker fiber-to-fiber bonds. TM The broad Mw / Mn and high melt index ratio of 4002 will likely result in strain hardening, making it unsuitable for fine fiber spinning.

[0134] 2911FS and 7200F are typical HDPE resins used in the industry. Both have greater than 80% of the composition eluted above 95°C, indicating good bond strength once formed. However, for these two polyethylenes, the bonding temperature is high and the bonding temperature range is narrow. Without being limited by theory, it is believed that the high bonding temperature and narrow bonding temperature range are because these polyethylenes lack a low density fraction. In addition, 2911FS and 7200F produce nonwoven fabrics with poor soft hand ratings.

[0135] In contrast, both IE1 and IE2 have (a) a composition that elutes more than 10% at a temperature below 90°C (see Figure 1 ) and (b) a composition that elutes greater than 5% at a temperature above 95°C. It is believed that this unique composition with two elution fractions enables lower bonding temperatures, a wider bonding temperature window, and good bond strength for the bicomponent fibers. The overall lower density of IE1 and IE2 (especially compared to HDPE 2911FS and 7200F) can also provide a soft hand.

[0136] As noted above, the density of IE1 and IE2 appears to affect not only the comonomer distribution along the molecular weight, but also the balance of the high density fraction and the low density fraction, which appears to be contrary to conventional wisdom. This unique phenomenon of adjustability can allow fine tuning of the density of the polyethylene composition to accommodate different processes and the material needs of different consumers. That is, an additional advantage of the polymers of the present invention is the ability to use density (comonomer amount) to adjust the size of the low density fraction, thereby changing the balance of ease of processing (low / wide melting window) versus strength, while still maintaining appropriate strength even at lower temperature melting points / fiber bonding points.

[0137] This feature is Figure 2 , which provides an additional means of quantifying this unique effect (preferential incorporation of comonomer into identifiable low density fractions of polyethylene as density decreases, ie, comonomer incorporation increases). Figure 2 is a graph illustrating the weight percent of polymer eluting below 90° C. in a TREF experiment (Y-axis) as a function of density (X-axis) for various example polymers. As can be seen, the inventive polyethylene copolymers follow this relationship: Y>-3000X+2865, where Y is the weight percent TREF eluting at 90° C. or less; and X is the density (g / cm 3 ); and further having a density of 0.930 to 0.955 g / cm 3 In the density value greater than about 0.955g / cm 3(and with particular reference to HDPE homopolymers 2911FS and 7200F), the relationship becomes illogical because such samples are homopolymers without comonomer, and therefore adjustable comonomer incorporation is not appropriate for analysis of such polymers. As noted, the lower density of the inventive polyethylene provides an advantageous softer hand for bicomponent fiber applications compared to HDPE, while also providing lower melting (easier processing) - which as noted is adjustable in the inventive polyethylene, allowing for easy balancing of ease of processing with good mechanical strength.

[0138] Four staple fiber samples from Table 4 were used to produce nonwoven fabrics. Briefly, the staple fibers were opened and fed to a carding machine to deagglomerate the staple fibers. The resulting web was passed through an oven for hot air bonding. The temperature of the hot air and the line speed through the oven are known to those skilled in the art. Although about 165°C or higher temperatures, such as 170°C, are typically used for the reference PET / PE bicomponent fiber process, it was found that the EM 1 / / PET staple fiber sample could be bonded at 160°C. The properties of the resulting nonwoven fabric are provided in Table 5.

[0139] Table 5

[0140]

[0141] In the manufacturing process of nonwoven fabrics, the fibers PET / / EM 1 and PET / / EM 2 both exhibit lower bonding temperatures than those made from other polyethylenes with similar density, which may allow for a wider operating window and lower power consumption.

[0142] When used with PET / / ASPUN TM When compared to 6000, the nonwoven fabric made from PET / / EM 1 showed lower Handtester values, which translated into a softer hand.

[0143] Therefore, the present invention is well suited to obtain the results and advantages mentioned and inherent therein. The specific embodiments and configurations disclosed above are illustrative only, as it is obvious that different but equivalent means can be adopted to modify and implement the present invention for those skilled in the art who benefit from the teachings herein. In addition, except as described in the following claims, it is not intended to limit the details of the construction or design shown herein. It is therefore obvious that the specific illustrative embodiments disclosed above can be changed, combined or modified, and all such changes are considered to be within the scope and spirit of the present invention. In the absence of any element not specifically disclosed herein and / or any optional element disclosed herein, the invention disclosed illustratively herein can be appropriately implemented. Although compositions and methods are described in terms of "comprising", "containing" or "including" various components or steps, the compositions and methods can also be "essentially composed of various components and steps" or "composed of various components and steps". All numerical values ​​and ranges disclosed above can be changed to a certain extent. Whenever a numerical range with a lower limit and an upper limit is disclosed, any numerical value and any included range falling within the range are specifically disclosed. In particular, each range of values ​​disclosed herein (having the following format "from about a to about b", or equivalently "from about a to b", or equivalently "from about ab") should be understood to recite each numerical value and range contained within the wider range of values. Similarly, when multiple ranges are disclosed (e.g., 1-100 or 10-90, e.g., 30 to 75), ranges from any disclosed lower end to any disclosed upper end (e.g., 10-75) are specifically contemplated. In addition, the terms in the claims have their ordinary, general meaning unless otherwise explicitly and clearly defined by the patentee. In addition, the indefinite articles "a" or "an" as used in the claims are defined herein to mean one or more than one of the elements it introduces.

Claims

1. A composition comprising: A polyethylene comprising from about 90 wt % to about 99.99 wt % ethylene derived units and from 0.01 wt % to 10 wt % units derived from an alpha-olefin other than ethylene, wherein the polyethylene has: Density: 0.930 g / cm 3 Up to 0.955g / cm 3 , The melt flow index (MI, measured at 190°C and 2.16 kg load) is 10 g / 10 min to 50 g / 10 min, Melt Index Ratio (MIR) is 15 to 25, The ratio of weight average molecular weight to number average molecular weight (Mw / Mn) is 2 to 4, The weight percent of TREF elution at 90°C and below is from 10 weight percent to 80 weight percent, and The weight percent of TREF elution at 95°C and above was 3 weight percent or greater.

2. The composition according to claim 1, further comprising: (a) the TREF peak elution temperature of the polyethylene is greater than the TREF 50 wt% elution temperature of the polyethylene; and / or (b) Polyethylene follows the comonomer incorporation relationship Y>-3000X+2865, where Y is the weight % of the polyethylene eluted at TREF at 90°C or less, and X is the density of the polyethylene (g / cm 3 ).

3. A composition according to any one of the preceding claims, wherein the polyethylene has an Mw / Mn of 2 to 3.

4. A composition according to any one of the preceding claims, wherein the polyethylene has a density of 0.930 g / cm 3 Up to 0.945g / cm 3 .

5. The composition of any one of the preceding claims, wherein the polyethylene has a broad orthogonal composition distribution (BOCD) index greater than 2.

6. The composition according to any one of the preceding claims, wherein the α-olefin is 1-hexene.

7. Methods, including: Polymerizing ethylene and non-ethylene alpha-olefins in the presence of a hafnocene catalyst in a fluidized bed gas reactor to produce polyethylene wherein the reactor pressure is less than 300 psig, wherein the polyethylene comprises from 90 wt% to 99.99 wt% ethylene derived units and from 0.01 wt% to 10 wt% alpha-olefin derived units, and wherein the polyethylene has: Density: 0.930 g / cm 3 Up to 0.955g / cm 3 , Melt index (MI) is 10g / 10min to 50g / 10min, Melt Index Ratio (MIR) is 15 to 25, The ratio of weight average molecular weight to number average molecular weight (Mw / Mn) is 2 to 4, TREF elution at 90°C and below is 10 wt% to 80 wt%, and TREF eluted at 95°C and above was 3 wt% or greater.

8. The process according to claim 7, wherein the α-olefin is 1-hexene.

9. The process according to any one of claims 7-8, wherein the reactor bed temperature during polymerization is from 70°C to 80°C.

10. The process according to any one of claims 7 to 9, wherein the catalyst productivity during polymerization is 7000 g / g or more.

11. The method according to any one of claims 7 to 10, further wherein: (a) the TREF peak elution temperature of the polyethylene is greater than the TREF 50 wt% elution temperature of the polyethylene; and / or (b) Polyethylene follows the comonomer incorporation relationship Y>-3000X+2865, where Y is the weight % of the polyethylene eluted at TREF at 90°C or less, and X is the density of the polyethylene (g / cm 3 ).

12. The method according to any one of claims 7 to 11, wherein the polyethylene has an Mw / Mn of 2 to 3.

13. The method according to any one of claims 7 to 12, wherein the density of the polyethylene is between 0.930 g / cm 3 -0.945g / cm 3 within the range.

14. The method of any one of claims 7-13, wherein the polyethylene has a broad orthogonal composition distribution (BOCD) index greater than 2.

15. Bicomponent fiber, comprising: a first polymer component comprising one or more of: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene, or polyetheretherketone; and A second polymer component comprising: the polyethylene of any one of claims 1-6.

16. The bicomponent fiber of claim 15, wherein the bicomponent fiber has a core-sheath configuration with the second polymer component serving as the sheath.

17. The bicomponent fiber of any one of claims 15-16, wherein the bicomponent fiber is a bicomponent staple fiber.

18. A method comprising: Melt spinning the bicomponent fiber of any one of claims 15-16; cutting the bicomponent fibers into bicomponent staple fibers; The nonwoven fabric is produced from the bicomponent staple fibers using a hot air bonding temperature of 180°C or less.

19. The method of claim 18, wherein the hot air bonding temperature is 150°C to 165°C.

20. The method according to any one of claims 18-19, further comprising: The bicomponent fibers are stretched prior to cutting the bicomponent fibers.

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