Polyethylene composition suitable for cast stretch film

Abstract

Provided are polyethylene compositions and cast stretch films comprising the polyethylene compositions. The cast stretch films can exhibit improved tear strength and pallet benefits while maintaining other properties. The cast stretch films can also be fully compatible with polyethylene recycling streams and can be free of polypropylene.

Description

Technical Field

[0001] The embodiments of this disclosure generally relate to polyethylene compositions, and more specifically to polyethylene compositions suitable for cast stretch films. Background Technology

[0002] Cast stretch film is a highly transparent film used to protect and utilize manufactured goods or articles during transport and storage. High transverse tear strength is highly desirable in cast stretch films to minimize catastrophic damage during pallet packaging. To increase transverse tear strength, cast stretch films are typically formed from polyolefins comprising a mixture of polypropylene and polyethylene, with polypropylene added in part to improve tear properties. Such films can be difficult to manufacture and difficult (if not impossible) to recycle together due to the different mixtures of incompatible recyclable materials (i.e., polypropylene and polyethylene). With the continued growth in demand for sustainable and recyclable materials, there remains a strong need for polyethylene compositions that can form cast stretch films with improved tear strength while maintaining other properties such as stretchability and puncture resistance. Summary of the Invention

[0003] Embodiments of this disclosure satisfy the aforementioned needs by providing a polyethylene composition that is fully recyclable in a polyethylene recycling stream and can be used to form cast stretch films exhibiting improved tear strength properties. The films of this invention can have better performance than other cast stretch films (e.g., cast stretch films containing polyethylene) and, for example, can provide better pallet benefits.

[0004] This document discloses a polyethylene composition. In an embodiment, the polyethylene composition is characterized by having the following: (a) 0.910 g / cm³ 3 Up to 0.945 g / cm 3 (a) density; (b) melt index (I2) from 0.5 g / 10 min to 7.0 g / 10 min; (c) a first polyethylene fraction having a single peak in the temperature range of 40 °C to 85 °C in the elution curve obtained by the modified comonomer composition distribution (iCCD) analysis method; (d) a second polyethylene fraction having a single peak in the temperature range of 90 °C to 115 °C in the elution curve obtained by the iCCD analysis method, wherein the area fraction of the second polyethylene fraction is the area in the elution curve below the peak of the second polyethylene fraction between 90 °C and 115 °C, wherein the area fraction of the second polyethylene fraction accounts for at least 30% of the total area of ​​the elution curve, and wherein the peak width of the second polyethylene fraction at the 50% peak height is less than 4.0 °C; and (e) a molecular weight comonomer distribution coefficient (MWCDI) value less than 0.

[0005] This document also discloses a cast stretch film. In an embodiment, the cast stretch film comprises a polyethylene composition characterized by having the following: (a) 0.910 g / cm³ 3 Up to 0.945 g / cm 3 (a) density; (b) melt index (I2) of 0.5 g / 10 min to 7 g / 10 min; (c) a first polyethylene fraction having a single peak in the temperature range of 40 °C to 85 °C in the elution curve obtained by the modified comonomer composition distribution (iCCD) analysis method; (d) a second polyethylene fraction having at least one peak in the temperature range of 90 °C to 115 °C in the elution curve obtained by the iCCD analysis method, wherein the area fraction of the second polyethylene fraction is the area below the peak of the second polyethylene fraction in the elution curve between 90 °C and 115 °C, and wherein the area fraction of the second polyethylene fraction accounts for at least 30% of the total area of ​​the elution curve; and (e) a MWCDI value less than 0.

[0006] These and other implementation schemes are described in more detail in the specific embodiments. Attached Figure Description

[0007] Figure 1 The iCCD elution curve is schematically depicted.

[0008] Figure 2 This is a diagram of the data flow graph for a dual parallel reactor.

[0009] Figure 3 This is a diagram of the data flow graph for a dual-series reactor.

[0010] Figure 4 This is the iCCD elution curve of polymer 1 in Example 1.

[0011] Figure 5 This is a GPC overlay image of polymer 1 in Example 1. Detailed Implementation

[0012] Specific embodiments of this application will now be described. However, this disclosure may be implemented in various forms and should not be construed as limiting it to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0013] Stretch film is a name given to polyolefin films that can be cold-stretched in the longitudinal and / or transverse directions without heat application and can maintain tension for a long time when stretched around a load. The difference between cast stretch film and blown stretch film lies in the manufacturing method. The main differences between cast and blown films involve cooling methods, film orientation, linear velocity, and thickness control. Compared to blown films, cast films generally exhibit better optical properties and a much higher degree of longitudinal orientation. Cast stretch films and film structures with the novel properties described herein can be prepared using conventional cast film manufacturing techniques.

[0014] As used herein, the term "polymer" refers to a polymeric compound prepared by polymerizing monomers of the same or different types. Therefore, the general term polymer encompasses the term homopolymer (used to refer to a polymer prepared from only one type of monomer) and the term copolymer or interpolymer. Trace impurities (e.g., catalyst residues) may be incorporated into and / or within a polymer. A polymer can be a single polymer, a polymer blend, or a mixture of polymers comprising a mixture of polymers formed in situ during polymerization.

[0015] As used herein, the terms “polyethylene” or “ethylene-based polymer” should mean a polymer comprising a majority amount (>50 mol%) of units derived from ethylene monomers. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers).

[0016] The terms “comprising,” “including,” “having,” and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures, whether or not such components, steps, or procedures are specifically disclosed. For the avoidance of any doubt, unless stated otherwise, all compositions claimed using the term “comprising” may include any additional additives, adjuvants, or compounds, whether polymerized or otherwise. In contrast, the term “substantially constitutes” excludes any other components, steps, or procedures from any subsequently listed scope, except those that are not essential for operability. The term “consisting of” excludes any ingredients, steps, or procedures not specifically described or listed.

[0017] Polyethylene composition

[0018] This document discloses a polyethylene composition. In an embodiment, the polyethylene composition is characterized by having a content of 0.910 g / cm³. 3 Up to 0.945 g / cm 3 The density. This document discloses and includes 0.910 g / cm³. 3 Up to 0.945 g / cm 3All individual values ​​and sub-ranges. For example, a polyethylene composition can have 0.910 g / cm³. 3 Up to 0.940 g / cm 3 0.910 g / cm 3 Up to 0.935 g / cm 3 0.910 g / cm 3 Up to 0.930 g / cm 3 0.910 g / cm 3 Up to 0.925 g / cm 3 0.915g / cm 3 Up to 0.945 g / cm 3 0.915g / cm 3 Up to 0.940 g / cm 3 0.915g / cm 3 Up to 0.935 g / cm 3 0.915g / cm 3 Up to 0.930 g / cm 3 0.915g / cm 3 Up to 0.925 g / cm 3 Or 0.915g / cm 3 Up to 0.920 g / cm 3 The density.

[0019] In the embodiments, the polyethylene composition is also characterized by having a melt index (I2) of 0.5 g / 10 min to 7.0 g / 10 min. All individual values ​​and sub-ranges of 0.5 g / 10 min to 7.0 g / 10 min are disclosed and included herein. For example, the polyethylene composition may have a melt index (I2) of 0.5 g / 10 min to 6.0 g / 10 min, 0.5 g / 10 min to 4.0 g / 10 min, 0.5 g / 10 min to 2.0 g / 10 min, 0.8 g / 10 min to 6.0 g / 10 min, 0.8 g / 10 min to 4.0 g / 10 min, 0.8 g / 10 min to 2.0 g / 10 min, 0.8 g / 10 min to 1.8 g / 10 min, 1.0 g / 10 min to 7.0 g / 10 min, 1.0 g / 10 min to 6.0 g / 10 min, 1.0 g / 10 min to 4.0 g / 10 min, or 1.0 g / 10 min to 2.0 g / 10 min.

[0020] In embodiments, the polyethylene composition is further characterized by having a first polyethylene fraction and a second polyethylene fraction. As described herein, a polyethylene “fraction” refers to a portion of the total composition of the polyethylene component. Embodiments disclosed herein comprise at least a “first polyethylene fraction” and a “second polyethylene fraction.” Fractions contained in the polyethylene composition can be quantified by the temperature range of their elution profiles obtained via an improved comonomer composition distribution (iCCD) analytical method. Unless otherwise stated, any elution profiles mentioned herein are elution profiles observed via iCCD. Examples of such fractions will be better understood given the embodiments provided herein. Typically, the first fraction may comprise a single peak within the temperature range of the first fraction, and the second fraction may comprise a single peak within the temperature range of the second fraction. The polyethylene compositions described herein may be referred to as “multimodal,” meaning they comprise at least two peaks in their elution profiles. Some embodiments may be “bimodal,” meaning there are two main peaks.

[0021] Referring to the described iCCD distribution, Figure 1 The sample iCCD distribution 100 and the cumulative weight fraction curve 200 are schematically depicted. Figure 1 This section generally depicts several characteristics of the iCCD curves of the polyethylene compositions currently described in detail herein, such as the first fraction, second fraction, and full width at half maximum (FWHM). Therefore, Figure 1 This can be used as a reference regarding public information related to the iCCD curves provided herein. Specifically, the first segment 102 and the second segment 106 are depicted. The first segment 102 has a peak 104 and the second segment 106 has a peak 108. Each segment has a half-width at half-maximum (i.e., the peak width at 50% of the peak height) 110 and 112. It should be understood that... Figure 1 The curves are not derived from experiments or observations, but rather provide information for the purpose of describing specific characteristics of iCCD elution curves.

[0022] In an embodiment, the polyethylene composition is characterized by having a first polyethylene fraction. The first polyethylene fraction may have a single peak in the elution profile obtained by iCCD analysis within a temperature range of 40°C to 85°C. As used herein, "single peak" refers to an iCCD in which a particular fraction comprises only a single peak. That is, in some embodiments, the iCCDs of the first and second polyethylene fractions comprise only an upward-sloping region followed by a downward-sloping region to form a single peak. It should be understood that the peak in the first or second polyethylene fraction may not be formed by a local minimum in the respective polyethylene fraction at a defined temperature boundary. That is, the peak must be a peak spanning the entire spectral range, not a peak formed by a threshold temperature of the polyethylene fraction. For example, if a polyethylene fraction contains a single peak followed by a single valley (upward-sloping, then downward-sloping, then upward-sloping again), then only a single peak will exist in such a polyethylene fraction.

[0023] In an embodiment, the polyethylene composition is characterized by having a second polyethylene fraction. The second polyethylene fraction may have a single peak in the elution profile obtained by iCCD analysis within a temperature range of 90°C to 115°C. In an embodiment, the width of the single peak of the second polyethylene fraction at 50% peak height may be less than 4.0°C, less than 3.5°C, less than 3.0°C, or even less than 2.5°C. Typically, a smaller temperature range at 50% peak height corresponds to a “sharper” peak. Without being bound by any particular theory, it is believed that a “sharper” or “narrower” peak is a characteristic induced by molecular catalysts and indicates minimal comonomer incorporation in the higher density fraction, thereby enabling higher density separation between the two fractions.

[0024] In an embodiment, the first polyethylene area fraction is defined as the area below the single peak of the first polyethylene fraction in the elution curve between 40°C and 85°C. Similarly, the second polyethylene area fraction is defined as the area below the single peak of the second polyethylene fraction in the elution curve between 90°C and 115°C. The first polyethylene area fraction and the second polyethylene fraction may respectively correspond to the total relative mass of each polymer fraction in the polyethylene composition. In an embodiment, the second polyethylene area fraction accounts for at least 30% of the total area of ​​the elution curve. For example, the second polyethylene area fraction may account for at least 30%, at least 32%, at least 33%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, or even at least 60% of the total area of ​​the iCCD elution curve, or it may account for 30% to 65%, 30% to 60%, 30% to 55%, 30% to 50%, 35% to 65%, 35% to 50%, 40% to 65%, or 40% to 60% of the total area of ​​the elution curve.

[0025] In embodiments, the second polyethylene fraction of the polyethylene composition may have a weight-average molecular weight (Mw) of at least 95,000 g / mol. All individual values ​​and sub-ranges of at least 95,000 g / mol are disclosed and included herein. For example, the second polyethylene fraction may have a weight-average molecular weight (Mw) of at least 95,000 g / mol, at least 100,000 g / mol, at least 120,000 g / mol, at least 160,000 g / mol, or at least 200,000 g / mol, or may have a weight-average molecular weight (Mw) in the range of 95,000 g / mol to 260,000 g / mol, 100,000 g / mol to 250,000 g / mol, or 100,000 g / mol to 220,000 g / mol. The molecular weight of the polyethylene fraction may be calculated based on GPC results, as described below.

[0026] In the embodiments, the polyethylene composition is further characterized by having a molecular weight comonomer distribution index (MWCDI) less than 0. All individual values ​​and sub-ranges less than 0 are disclosed and incorporated herein. For example, the polyethylene composition may have an MWCDI less than 0, less than -1, less than -2, less than -3, less than -4, less than -5, or less than -6, or may have an MWCDI in the range of 0 to -15, -1 to -12, -2 to -10, or -3 to -8, wherein the MWCDI can be measured according to the test methods described below.

[0027] In one embodiment, the polyethylene composition is further characterized in that the molecular weight distribution, expressed as a weight-average molecular weight to number-average molecular weight ratio (Mw / Mn), is in the range of 2.0 to 8.0. In another embodiment, the molecular weight distribution (Mw / Mn) can be 2.0 to 7.0, 2.0 to 6.0, 2.0 to 5.0, 2.5 to 7.0, 2.5 to 6.0, or 2.5 to 5.0. The molecular weight distribution (Mw / Mn) of the polyethylene composition can be calculated based on GPC, as described below.

[0028] In one embodiment, the polyethylene composition may be further characterized by having a zero-shear viscosity ratio (ZSVR) of less than 3.0. For example, the polyethylene composition may have a ZSVR of less than 2.9, less than 2.8, less than 2.7, less than 2.6, less than 2.5, less than 2.4, less than 2.3, less than 2.2, less than 2.1, less than 2.0, less than 1.9, less than 1.8, less than 1.7, less than 1.6, less than 1.5, less than 1.4, less than 1.3, less than 1.2, or even less than 1.1. In one or more embodiments, the polyethylene component may have a ZSVR of at least 1.0. The ZSVR of the polyethylene composition can be measured according to the test methods described below.

[0029] Blends or mixtures of polyethylene compositions with other polyolefins can be formed. Suitable polymers for blending with the polyethylene compositions of the present invention include thermoplastic and non-thermoplastic polymers, including natural and synthetic polymers. Exemplary polymers for blending include: polypropylene (both impact-modified polypropylene, isotactic polypropylene, atactic polypropylene, and atactic ethylene / propylene copolymers); various types of polyethylene, including high-pressure free radical low-density polyethylene (LDPE), Ziegler-Natta linear low-density polyethylene (LLDPE), metallocene PE (including multi-reactor PE (“in-reactor” blends of Ziegler-Natta PE and metallocene PE, such as U.S. Patent No. 6,545,088 (Kolthammer et al.), U.S. Patent No. 6,538,070 (Cardwell et al.); U.S. Patent No. 6,566,446 (Parikh et al.); U.S. Patent No. 5,844,04 5 (Kolthammer et al.); US Patent No. 5,869,575 (Kolthammer et al.); US Patent No. 6,448,341 (Kolthammer et al.)), ethylene-vinyl acetate (EVA), ethylene / vinyl alcohol copolymers, polystyrene, impact-modified polystyrene, acrylonitrile-butadiene-styrene (ABS), styrene / butadiene block copolymers and their hydrogenated derivatives (styrene-butadiene-styrene (SBS) and styrene-ethylene-butadiene-styrene (SEBS)), and thermoplastic polyurethanes. Homogeneous polymers, such as olefin plasmids and elastomers, ethylene-based and propylene-based copolymers (e.g., under the trade name VERSIFY) TM Plastics and elastomers (The Dow Chemical Company), SURPASS TM (Nova Chemicals) and VISTAMAXX TM (Polymers obtained from ExxonMobil Chemical Co.) can also be used as components in blends comprising the polyethylene compositions of the present invention. In embodiments, suitable polymers for blending with the polyethylene compositions disclosed herein include LDPE and LLDPE, such as AGILITY 1200 (manufactured by Dow Chemical Company).

[0030] In embodiments, the polyethylene compositions disclosed in this invention may further comprise additional components, such as one or more additives. Such additives include, but are not limited to, antistatic agents, colorants, dyes, lubricants, fillers (such as TiO2 or CaCO3), opacifiers, nucleating agents, processing aids, pigments, primary antioxidants, secondary antioxidants, UV stabilizers, anti-caking agents, slip agents, lubricants, flame retardants, antimicrobial agents, deodorizers, antifungal agents, and combinations thereof. Based on the weight of the polyethylene composition containing such additives, the polyethylene composition may comprise from about 0.1% to about 10% of the total weight of such additives.

[0031] In embodiments, a first polyethylene fraction of the polyethylene composition may be formed in the presence of a first molecular catalyst, and a second polyethylene fraction of the polyethylene composition may be formed in the presence of a second molecular catalyst. The first and second molecular catalysts may be the same or different catalysts. In other embodiments, the first polyethylene fraction of the polyethylene composition may be formed in the presence of a molecular catalyst, and the second polyethylene fraction of the polyethylene composition may be formed in the presence of a Ziegler-Natta catalyst. The polymerization and catalyst systems used to form the polyethylene compositions according to the embodiments disclosed herein are described in more detail below. Typically, the molecular catalyst is a homogeneous polymerization catalyst comprising (a) a transition metal, (b) one or more unsubstituted or substituted cyclopentadienyl ligands, and / or (c) one or more ligands containing at least one heteroatom such as oxygen, nitrogen, phosphorus, and / or sulfur. The molecular catalyst may be immobilized on an inorganic support, such as silica, alumina, or MgCl2.

[0032] polymerization

[0033] The polyethylene components described herein can be produced using any conventional polymerization method. Such conventional polymerization methods include, but are not limited to, slurry polymerization methods and solution polymerization methods using one or more conventional reactors, such as loop reactors in parallel or in series, isothermal reactors, stirred tank reactors, batch reactors, and / or any combination thereof. The polyethylene compositions can be produced, for example, via solution-phase polymerization methods using one or more loop reactors, isothermal reactors, and combinations thereof.

[0034] Typically, solution-phase polymerization can be carried out at temperatures ranging from 115°C to 250°C (e.g., 115°C to 210°C) and pressures ranging from 300 psi to 1,000 psi (e.g., 400 psi to 800 psi) in one or more well-mixed reactors, such as one or more isothermal loop reactors or one or more adiabatic reactors. In one embodiment, in a dual-reactor configuration, the temperature in the first reactor is in the range of 115°C to 190°C (e.g., 160°C to 180°C), while the temperature in the second reactor is in the range of 150°C to 250°C (e.g., 180°C to 220°C). In other embodiments, in a single reactor, the temperature in the reactor is in the range of 115°C to 250°C (e.g., 115°C to 225°C).

[0035] Residence time in solution-phase polymerization can range from 2 to 30 minutes (e.g., 5 to 25 minutes). Ethylene, solvent, hydrogen, one or more catalyst systems, optionally one or more cocatalysts, and optionally one or more comonomers are continuously fed into one or more reactors. Exemplary solvents include, but are not limited to, isoparaffins. For example, such solvents may be available under the name ISOPAR E from ExxonMobil Chemical Co., Houston, Texas. The resulting mixture of the polyethylene composition and solvent is then removed from the reactor, and the polyethylene composition is separated. The solvent is typically recovered via a solvent recovery unit (i.e., a heat exchanger and a vapor-liquid separator drum) and subsequently recycled back into the polymerization system.

[0036] In some embodiments, the polyethylene composition can be produced by solution polymerization in a dual-reactor system, such as a dual-loop reactor system, wherein ethylene is polymerized in the presence of one or more catalyst systems. In some embodiments, only ethylene is polymerized. Additionally, one or more co-catalysts may be present. In another embodiment, the polyethylene composition can be produced by solution polymerization in a single-reactor system, such as a single-loop reactor system, wherein ethylene is polymerized in the presence of two catalyst systems. In some embodiments, only ethylene is polymerized.

[0037] catalyst system

[0038] Specific embodiments of a catalyst system that can be used in one or more embodiments to produce the polyethylene compositions described herein will now be described. It should be understood that the catalyst systems of this disclosure may be embodied in different forms and should not be construed as limited to the specific embodiments set forth in this disclosure. Rather, the provision of embodiments makes this disclosure thorough and complete, and the embodiments will fully convey the scope of the subject matter to those skilled in the art.

[0039] The term "independently chosen" is used in this document to indicate R groups (such as R...). 1 R 2 R 3 R 4 and R 5 ) can be the same or different (e.g., R) 1 R 2 R 3 R 4 and R 5 Both can be substituted alkyl groups, or R 1 and R 2 It can be a substituted alkyl group and R 3 (This can be aryl, etc.). The use of the singular form includes the use of the plural form, and vice versa (e.g., hexane solvent includes various hexanes). The named R group will generally have a structure recognized in the art as corresponding to the R group having that name. These definitions are intended to supplement and illustrate, rather than exclude, definitions known to those skilled in the art.

[0040] The term "procatalyst" refers to a compound that exhibits catalytic activity when combined with an activator. The term "activator" refers to a compound that chemically reacts with the procatalyst in a manner that converts the procatalyst into a catalytically active catalyst. As used herein, the terms "co-catalyst" and "activator" are interchangeable.

[0041] When used to describe certain carbon-containing chemical groups, the form is "(C x -C y The parenthetical expression “)” indicates that the unsubstituted form of the chemical group has x to y carbon atoms (inclusive). For example, (C1-C 40 Alkyl is an alkyl group having 1 to 40 carbon atoms in its unsubstituted form. In some embodiments and general structures, certain chemical groups may be substituted with one or more substituents such as RS. (C) x -C y The chemical groups defined in parentheses () are R S The substitution form can be based on any group R S The property contains more than y carbon atoms. For example, "exactly bound by a group R". S Replacement (C1-C) 40 ) alkyl, wherein R S The phenyl group (-C6H5) can contain 7 to 46 carbon atoms. Therefore, it is common practice to use the parenthetical phrase "(C6H5)" when referring to phenyl groups. x -C y The chemical group defined as ")" is substituent for one or more carbon atoms by one or more carbon-containing substituents R. SDuring substitution, both x and y are added with substituents R from all carbon atoms. S The minimum and maximum total number of carbon atoms in a chemical group are determined by the sum of the combinations of carbon atoms.

[0042] The term "substitution" means that at least one hydrogen atom (-H) bonded to the carbon atom or heteroatom corresponding to the unsubstituted compound or functional group is replaced by a substituent (e.g., R). S Substitution. The term "total substitution" means that each hydrogen atom (H) bonded to the carbon atom or heteroatom of the corresponding unsubstituted compound or functional group is replaced by a substituent (e.g., R). S Substitution. The term "multi-substitution" means that at least two, but fewer than all, hydrogen atoms bonded to the corresponding unsubstituted carbon or heteroatom of a compound or functional group are replaced by substituents.

[0043] The term "-H" refers to a hydrogen or hydrogen group covalently bonded to another atom. "Hydrogen" and "-H" are interchangeable and, unless explicitly stated otherwise, refer to the same thing.

[0044] The term "(C1-C40) hydrocarbon group" refers to a hydrocarbon group having 1 to 40 carbon atoms, and the term "(C1-C40) hydrocarbon subgroup" refers to a hydrocarbon diester having 1 to 40 carbon atoms, wherein each hydrocarbon group and each hydrocarbon diester is aromatic or non-aromatic, saturated or unsaturated, straight-chain or branched, cyclic (including monocyclic and polycyclic, fused and non-fused polycyclic, including bicyclic; 3 or more carbon atoms) or acyclic, and is not substituted or modified by one or more R groups. S replace.

[0045] In this disclosure, (C) 1- C 40 The hydrocarbon group is independently unsubstituted or substituted (C1-C2). 40 )alkyl, (C3-C 40 )cycloalkyl, (C3-C 20 )cycloalkyl-(C1-C 20 )alkylene, (C6-C 40 ) aryl or (C6-C 20 )aryl-(C1-C 20 ) alkylene. In some embodiments, the aforementioned (C1-C 40 Each hydrocarbon group in the hydrocarbon group has a maximum of 20 carbon atoms (i.e., (C 1- C 20 (hydrocarbon group), and in other embodiments, has up to 12 carbon atoms.

[0046] The term "(C1-C)" 40 alkyl and (C1-C) 18"alkyl" refers to a saturated straight-chain or branched hydrocarbon group with 1 to 40 carbon atoms or 1 to 18 carbon atoms, which is unsubstituted or surrounded by one or more R groups. S Replacement. Unreplaced (C1-C) 40 Examples of alkyl groups are unsubstituted (C1-C1) alkyl groups. 20 )alkyl; unsubstituted (C 1- C 10 )alkyl; unsubstituted (C 1- (C5) Alkyl; Methyl; Ethyl; 1-Propyl; 2-Propyl; 1-Butyl; 2-Butyl; 2-Methylpropyl; 1,1-Dimethylethyl; 1-Pentyl; 1-Hexyl; 1-Heptyl; 1-Nonyl; and 1-Decyl. Substituted (C1-C5) 40 Examples of alkyl groups are substituted (C1-C2) 20 )alkyl, substituted (C1-C 10 )alkyl, trifluoromethyl and [C 45 Alkyl group. The term "[C]" 45 Alkyl (with square brackets) means that there are a maximum of 45 carbon atoms in the group (including substituents), and is, for example, substituted by one RS (C 27 -C 40 ) alkyl, which are (C1-C5) alkyl. Each (C1-C5) alkyl can be methyl, trifluoromethyl, ethyl, 1-propyl, 1-methylethyl or 1,1-dimethylethyl.

[0047] The term "(C6-C)" 40 "Aryl" refers to an unsubstituted or substituted compound with 6 to 40 carbon atoms (one or more R groups). S A substituted monocyclic, bicyclic, or tricyclic aromatic hydrocarbon group, wherein at least 6 to 14 carbon atoms are aromatic ring carbon atoms, and the monocyclic, bicyclic, or tricyclic group comprises 1, 2, or 3 rings, respectively. One ring is an aromatic ring, and the other 2 or 3 rings are independently fused or non-fused rings, and at least one of the 2 or 3 rings is an aromatic ring. Unsubstituted (C6-C) 40 An example of an aryl group is the unsubstituted (C6-C) 20 ) aryl; unsubstituted (C6-C 18 ) aryl; 2-(C1-C5)alkyl-phenyl; 2,4-bis(C1-C5)alkyl-phenyl; phenyl; fluorenyl; tetrahydrofluorenyl; dicyclopentadienylphenyl; hexahydrodicyclopentadienylphenyl; indene; dihydroindene; naphthyl; tetrahydronaphthyl; and phenanthrene. Substituted (C6-C 40 Examples of aryl groups are substituted (C1-C) 20 ) aryl; substituted (C6-C 18 )aryl; 2,4-bis[(C 20[alkyl]-phenyl; polyfluorophenyl; pentafluorophenyl; and fluorene-9-one-1-yl.

[0048] The term "(C3-C)" 40 "Cycloalkyl" refers to a saturated cyclic hydrocarbon group having 3 to 40 carbon atoms, which is either unsubstituted or substituted with one or more R groups. S Substitution. Other cycloalkyl groups (e.g., (C10) x -C y Cycloalkyl groups are defined in a similar manner as having x to y carbon atoms and being unsubstituted or substituted by one or more R groups. S Replaced. Unreplaced (C3-C) 40 Examples of cycloalkyl groups are unsubstituted (C3-C4) 20 )cycloalkyl, unsubstituted (C3-C 10 Cycloalkyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, and cyclodecyl. Substituted (C3-C) 40 Examples of cycloalkyl groups are substituted (C3-C4) 20 )cycloalkyl, substituted (C3-C 10 )cycloalkyl, cyclopentanone-2-yl and 1-fluorocyclohexyl.

[0049] (C 1- C 40 Examples of alkylene groups include unsubstituted or substituted (C6-C) groups. 40 ()Asyl, (C3-C 40 )cycloalkylene and (C1-C 40 )alkylene (e.g., (C 1- C 20 (alkylene). In some embodiments, the bimolecular group is located on the same carbon atom (e.g., -CH2-) or on adjacent carbon atoms (i.e., 1,2-bimolecular group), or separated by one, two, or more than two intercalary carbon atoms (e.g., 1,3-bimolecular group, 1,4-bimolecular group, etc.). Some bimolecular groups include α,ω-bimolecular groups. α,ω-bimolecular groups are bimolecular groups with the largest carbon backbone spacing between the group carbons. (C2-C) 20 Some examples of alkylene α,ω-bigroups include ethyl-1,2-diyl (i.e., -CH2CH2-), propan-1,3-diyl (i.e., -CH2CH2CH2-), and 2-methylpropan-1,3-diyl (i.e., -CH2CH(CH3)CH2-). (C6-C) 50 Some examples of arylene α,ω-dimethyl groups include phenyl-1,4-diyl, naphth-2,6-diyl, or naphth-3,7-diyl.

[0050] The term "(C1-C)" 40"Alkylene" refers to an unsubstituted or compounded alkylene oxide having 1 to 40 carbon atoms. S Substituted saturated straight-chain or branched bigroups (i.e., the group is not on a ring atom). Unsubstituted (C1-C) 50 Examples of alkylene groups are unsubstituted (C 1- C 20 Alkylene groups, including unsubstituted -CH2CH2-, -(CH2)3-, -(CH2)4-, -(CH2)5-, -(CH2)6-, -(CH2)7-, -(CH2)8-, -CH2C*HCH3 and -(CH2)4C*(H)(CH3), where "C*" indicates the carbon atom from which a hydrogen atom is removed to form a secondary or tertiary alkyl group. Substituted (C1-C 50 Examples of alkylene groups are substituted (C1-C2) 20 Alkylene, -CF2-, -C(O)-, and -(CH2) 14 C(CH3)2(CH2)5- (i.e., 6,6-dimethyl-substituted n-1,20-eicosene). As previously stated, the two R... S They can form together (C1-C) 18 )alkylene, substituted (C1-C 50 Examples of alkylene groups also include 1,2-bis(methylene)cyclopentane, 1,2-bis(methylene)cyclohexane, 2,3-bis(methylene)-7,7-dimethyl-bicyclo[2.2.1]heptane and 2,3-bis(methylene)bicyclo[2.2.2]octene.

[0051] The term "(C3-C)" 40 "Cycloalkylene" refers to an unsubstituted or compounded alkylene oxide having 3 to 40 carbon atoms. S Substituted cyclic diradicals (i.e., radicals on ring atoms).

[0052] The term "heteroatom" refers to an atom other than hydrogen or carbon. Examples of heteroatoms include O, S, S(O), S(O)₂, and Si(R). C 2. P(R) P ), N(R N -N=C(R) C )2、-Ge(R C )2- or -Si(R C )-, where each R C Each R N and each R P For the unreplaced (C1-C) 18 The term "heterohydrocarbon" refers to a molecule or molecular framework in which one or more carbon atoms are replaced by heteroatoms. The term "(C1-C)" is used in conjunction with the hydrocarbon group or -H.40 "(C1-C4)" refers to a heterohydrocarbon group having 1 to 40 carbon atoms, and the term "(C1-C4)" is used in conjunction with the meaning of "(C1-C4)". 40 "Heteroalkyl group" refers to a heteroalkyl bibase having 1 to 40 carbon atoms, and each heteroalkyl group has one or more heteroatoms. The bibase of the heteroalkyl group is located on a carbon atom or a heteroatom, and the bibase of the heteroalkyl group can be located on: (1) one or two carbon atoms, (2) one or two heteroatoms, or (3) a carbon atom and a heteroatom. Each (C1-C 50 ) heterohydrocarbon groups and (C1-C 50 The heteroalkyl group can be unsubstituted or substituted with (one or more R groups). S Substituted, aromatic or non-aromatic, saturated or unsaturated, straight or branched, cyclic (including monocyclic and polycyclic, fused and non-fused polycyclic) or acyclic.

[0053] (C1-C 40 Heteroalkyl groups can be unsubstituted or substituted (C1-C2). 40 (heteroalkyl, (C1-C) 40 )hydrocarbon group -O-, (C 1- C 40 )hydrocarbon group -S-, (C1-C 40 )hydrocarbon group -S(O)-, (C1-C 40 )Hydrocarbon group -S(O) 2- (C1-C) 40 )hydrocarbon-Si(R C )2-、(C l -C 40 )hydrocarbon-N(R N )-、(C l -C 40 )hydrocarbon-P(R P )-、((C2-C 40 Heterocyclic alkyl groups, (C2-C 19 Heterocyclic alkyl-(C1-C) 20 )alkylene, (C3-C 20 )cycloalkyl-(C1-C 19 (Hypoalkylene, (C2-C) 19 Heterocyclic alkyl-(C1-C) 20 (Hypoalkylene, (C1-C) 40 () heteroaryl, (C1-C 19 ) heteroaryl-(C1-C 20 )alkylene, (C6-C 20 )aryl-(C1-C 19 (Hypoalkylene, or (C1-C) 19 ) heteroaryl-(C1-C 20 Heteroalkyl groups.

[0054] The term "(C4-C)" 40 "Heteroaryl" refers to an unsubstituted or substituted (by one or more R groups) aryl group with 4 to 40 total carbon atoms and 1 to 10 heteroatoms. S Substituted) monocyclic, bicyclic, or tricyclic heteroaromatic groups, wherein the monocyclic, bicyclic, or tricyclic group comprises one, two, or three rings, wherein the two or three rings are independently fused or unfused, and at least one of the two or three rings is heteroaromatic. Other heteroaromatic groups (e.g., typically (C x -C y ) heteroaryl groups, such as (C4-C 12 (Heteroaryl) is defined in a similar manner as having x to y carbon atoms (such as 4 to 12 carbon atoms) and being unsubstituted or substituted by one or more R atoms. S Substituted. Monocyclic heteroaromatic hydrocarbon groups are 5- or 6-membered rings. A 5-membered ring has 5 minus h carbon atoms, where h is the number of heteroatoms and can be 1, 2, or 3; and each heteroatom can be O, S, N, or P. Examples of 5-membered heteroaromatic hydrocarbon groups are pyrrolo-1-yl; piperidin-2-yl; furan-3-yl; thiophene-2-yl; pyrazol-1-yl; isoxazol-2-yl; isothiazol-5-yl; imidazole-2-yl; oxazol-4-yl; thiazol-2-yl; 1,2,4-triazol-1-yl; 1,3,4-oxadiazol-2-yl; 1,3,4-thiadiazol-2-yl; tetrazol-1-yl; tetrazol-2-yl; and tetrazol-5-yl. A 6-membered ring has 6 minus h carbon atoms, where h is the number of heteroatoms and can be 1 or 2, and the heteroatom can be N or P. Examples of 6-membered ring heteroaromatic hydrocarbon groups are pyridin-2-yl; pyrimidin-2-yl; and pyrazin-2-yl. Bicyclic heteroaromatic hydrocarbon groups can be fused 5,6- or 6,6-cyclic systems. Examples of fused 5,6-cyclic bicyclic heteroaromatic hydrocarbon groups are indol-1-yl; and benzimidazol-1-yl. Examples of fused 6,6-cyclic bicyclic heteroaromatic hydrocarbon groups are quinoline-2-yl; and isoquinoline-1-yl. Bicyclic heteroaromatic hydrocarbon groups can be fused 5,6,5-cyclic systems; 5,6,6-cyclic systems; 6,5,6-cyclic systems; or 6,6,6-cyclic systems. An example of a fused 5,6,5-cyclic system is 1,7-dihydropyrrolo[3,2-f]indol-1-yl. An example of a fused 5,6,6-cyclic system is 1H-benzo[f]indol-1-yl. An example of a fused 6,5,6-cyclic system is 9H-carbazole-9-yl. An example of a fused 6,5,6-cyclic system is 9H-carbazole-9-yl. An example of a fused 6,6,6-cyclic system is acridine-9-yl.

[0055] The aforementioned heteroalkyl group may contain (C1-C1) 50A saturated straight-chain or branched group containing one to 50 carbon atoms and one or more heteroatoms. Similarly, a heteroalkylene group can be a saturated straight-chain or branched bimolecular group containing 1 to 50 carbon atoms and one or more heteroatoms. Heteratoms as defined above can include Si(R) C 3. Ge(R) C 3. Si(R) C )2、Ge(R C 2. P(R) P 2. P(R) P ), N(R N )2、N(R N ), N, O, OR C , S, SR C S(O) and S(O)2, wherein each of the heteroalkyl and heteroalkylene groups is unsubstituted or is substituted by one or more R S replace.

[0056] Unreplaced (C2-C) 40 Examples of heterocyclic alkyl groups are unsubstituted (C2-C) 20 Heterocyclic alkyl groups, unsubstituted (C2-C) 10 Heterocyclic alkyl groups, aziridin-1-yl, oxacyclobut-2-yl, tetrahydrofuran-3-yl, pyrrolidine-1-yl, tetrahydrothiophene-S,S-dioxo-2-yl, morpholin-4-yl, 1,4-dioxane-2-yl, hexahydroacetane-4-yl, 3-oxacyclooctyl, 5-thiocyclononyl, and 2-azacyclodecyl.

[0057] The term "halogen atom" or "halogen" refers to a free radical of a fluorine (F), chlorine (Cl), bromine (Br), or iodine (I) atom. The term "halogen ion" refers to the anionic form of the following halogen atom: fluoride ion (F... - ), chloride ions (Cl) - ), bromide ions (Br) - ) or iodide ions (I - ).

[0058] The term "saturated" refers to the absence of carbon-carbon double bonds, carbon-carbon triple bonds, and (in heteroatom-containing groups) carbon-nitrogen, carbon-phosphorus, and carbon-silicon double bonds. In saturated chemical groups, the presence of one or more substituents R... S In the case of substitution, one or more double and / or triple bonds may or may not be present in the substituent R. S In Chinese, the term "unsaturated" means containing one or more carbon-carbon double bonds, carbon-carbon triple bonds, and (in heteroatom-containing groups) carbon-nitrogen, carbon-phosphorus, and carbon-silicon double bonds, excluding those that may exist in substituents R. S(If present) any such double bond in or that may exist in (hetero)aromatic rings (if present).

[0059] According to some embodiments, the catalyst system for producing the polyethylene composition comprises a metal-ligand complex according to formula (I):

[0060]

[0061] In formula (I), M is a metal selected from titanium, zirconium, or hafnium, in the form of an oxidation state of +2, +3, or +4; n is 0, 1, or 2; when n is 1, X is a monodentate or bidentate ligand; when n is 2, each X is a monodentate ligand and may be the same or different; the metal-ligand complex is electrically neutral overall; each Z is independently selected from -O-, -S-, -N(R-) N - or - P(R) P )-; L is (C1-C 40 ) alkylene group or (C1-C 40 ) heterohydrocarbon group, of which (C1-C 40 The alkylene group has a portion of the main chain consisting of two Z groups in formula (I) with 1-carbon to 10-carbon atoms connected (to which L is bonded), or (C1-C 40 The heteroalkyl group has a portion of the main chain consisting of 1- to 10-atoms of two Z groups in formula (I), wherein (C1-C 40 The 1- to 10-atom connections of the heteroalkyl group to the 1- to 10 atoms of the main chain are each independently a carbon atom or a heteroatom, wherein each heteroatom is independently O, S, S(O), S(O)2, Si(R)2, or S(O)2. C )2、Ge(R C 2. P(R) C ) or N(R C ), where each R C Independently is (C1-C 30 ) hydrocarbon group or (C1-C 30 ( ) heteroalkyl group; R1 and R8 are independently selected from the following groups: -H, (C1-C40)alkyl group, (C1-C 40 heterohydrocarbon group, -Si(R) C )3、-Ge(R C 3. -P(R) P )2、-N(R N )2、-OR C -SR C、 -NO2, -CN, -CF3, R C S(O)-、R C S(O)2-、(R C )2C=N-、RC C(O)O-、R C OC(O)-, R C C(O)N(R N )-、(R N )2NC(O)-, halogens and groups having formula (II), (III) or (IV):

[0062]

[0063]

[0064] In equations (II), (III), and (IV), R 31-35 R 41-48 or R 51-59 Each of them is independently selected from (C1-C) 40 Hydrocarbon group, (C1-C) 40 heterohydrocarbon group, -Si(R) C )3、-Ge(R C 3. -P(R) P )2、-N(R N 2. -N=CHR C -OR C -SR C -NO2, -CN, -CF3, R C S(O)-、R C S(O)2-、(R C )2C=N-、R C C(O)O-、R C OC(O)-, R C C(O)N(R N )-、(R N )2NC(O)-, halogen or -H, with the constraint R 1 or R 8 At least one of them is a group having formula (II), formula (III) or formula (IV).

[0065] In equation (I), R 2-4 R 5-7 and R 9-16 Each of them is independently selected from (C1-C) 40 ) hydrocarbon group, (C1-C 40 heterohydrocarbon group, -Si(R) C )3、-Ge(R C 3. -P(R) P )2、-N(R N 2. δ-N=CHR C -OR C -SR C-NO2, -CN, -CF3, R C S(O)-、R C S(O)2-、(R C )2C=N-、R C C(O)O-、R C OC(O)-, R C C(O)N(R N )-、(R C )2NC(O)-, halogens and -H.

[0066] In some embodiments, the polyethylene component is formed using a first catalyst according to formula (I) in a first reactor and a different catalyst according to formula (I) in a second reactor.

[0067] In one exemplary embodiment using a dual-loop reactor, the primary catalyst used in the first loop is zirconium, [[2,2”'-[[bis[1-methylethyl)germanene]bis(methyleneoxy-κO)]bis[3”,5,5”-tris(1,1-dimethylethyl)-5'-octyl[1,1':3',1”-terphenyl]-2'-olato-κO]](2-)]dimethyl-, having the chemical formula C 86 H 128 F2GeO4Zr and the following structure (V):

[0068]

[0069] In such an implementation, the main catalyst used in the second ring tube is zirconium, [[2,2”'-[1,3-propanediylbis(oxy-κO)]bis[3-[2,7-bis(1,1-dimethylethyl)-9H-carbazole-9-yl]]-5'-(dimethyloctylsilyl)-3'-methyl-5-(1,1,3,3-tetramethylbutyl)[1,1]-biphenyl]-2-olato-κO]](2-)]dimethyl, having the chemical formula C 107 H 154 N2O4Si2Zr and the following structures (VI):

[0070]

[0071] In another embodiment, the main catalyst used in the second ring tube is hafnium, [[2,2”'-[1,3-propanediylbis(oxy-κO)]bis[3-[2,7-bis(1,1-dimethylethyl)-9H-carbazole-9-yl]]-5'-(dimethyloctylsilyl)-3'-methyl-5-(1,1,3,3-tetramethylbutyl)[1,1]-biphenyl]-2-olato-κO]](2-)]dimethyl, having the chemical formula C 107 H154 N2O4Si2Zr and the following structures (VII):

[0072]

[0073] co-catalyst components

[0074] Catalytic activity can be achieved by any technique known in the art for activating metal-based catalysts for olefin polymerization reactions, including metal-ligand complexes of formula (I). For example, a system comprising a metal-ligand complex of formula (I) can be made catalytically active by contacting the complex with an activating cocatalyst or by combining the complex with an activating cocatalyst. Activating cocatalysts suitable for this document include alkylaluminum; polymeric or oligomeric aluminum oxanes (also known as aluminum oxanes); neutral Lewis acids; and non-polymeric, non-coordinated, ion-forming compounds (including those used under oxidizing conditions). A suitable activation technique is bulk electrolysis. Combinations of one or more of the aforementioned activating cocatalysts and techniques are also contemplated. The term "alkylaluminum" means dihydrogenated monoalkylaluminum or dihalogenated monoalkylaluminum, hydrogenated dialkylaluminum or halodialkylaluminum, or trialkylaluminum. Examples of polymeric or oligomeric aluminum oxanes include methylaluminoxane, methylaluminoxane modified with triisobutylaluminum, and isobutylaluminoxane.

[0075] Lewis acid activators (co-catalysts) contain 1 to 3 (C1-C2) groups as described herein. 20 A Group 13 metal compound with a hydrocarbon substituent. In one embodiment, the Group 13 metal compound is a tri((C1-C) group 13 metal compound. 20 ()hydrocarbon-substituted aluminum or tri((C1-C) 20 Hydroxyl)-boron compounds. In other embodiments, the Group 13 metal compound is a tri(hydroxyl)-substituted aluminum, tri((C1-C)-boron compound. 20 )hydro-boron compounds, tri((C1-C 10 Alkyl aluminum, tri((C6-C) 18 (Aryl)boron compounds and their halogenated (including perhalogenated) derivatives. In other embodiments, the Group 13 metal compound is tris(fluorosubstituted phenyl)borane or tris(pentafluorophenyl)borane. In some embodiments, the activation cocatalyst is tris((C1-C)borane. 20 ) hydrocarbon borates (e.g., triphenylmethyltetrafluoroborate) or tri((C1-C 20 )hydro-based)ammonium tetra((C1-C 20 (e.g., bis(octadecyl)methylammonium tetra(pentafluorophenyl)borane). As used herein, the term "ammonium" refers to a nitrogen cation that is ((C1-C2) 20 )hydrocarbon group)4N + 、((C1-C20 )hydrocarbon group)3N(H) + 、((C1-C 20 )hydrocarbon group)2N(H)2 + (C1-C) 20 )hydrocarbon N(H)3 + or N(H)4 + Where there are two or more (C1-C) 20 When there are hydrocarbon groups, they can be the same or different.

[0076] The combination of neutral Lewis acid activators (co-catalysts) includes tris((C1-C4)alkyl)aluminum and tri((C6-C4)halogenated tris((C6-C4)alkyl)aluminum. 18 Mixtures of arylborane compounds, particularly tris(pentafluorophenyl)borane. Other embodiments are combinations of such neutral Lewis acid mixtures with polymeric or oligomeric aluminum oxanes, and combinations of single neutral Lewis acids (especially tris(pentafluorophenyl)borane) with polymeric or oligomeric aluminum oxanes.

[0077] The metal-ligand complex catalyst system of formula (I) can be activated by combination with one or more cocatalysts (e.g., cation-forming cocatalysts, strong Lewis acids, or combinations thereof) to form an active catalyst composition. Suitable activation cocatalysts comprise polymeric or oligomeric aluminum oxanes (especially methylaluminoxanes) and inert, compatible, noncoordinate, ion-forming compounds. Exemplary suitable cocatalysts include, but are not limited to: modified methylaluminoxane (MMAO), bis(hydrogenated tallow alkyl)methyltetra(pentafluorophenyl)boronic acid (1... - )amines, and combinations thereof.

[0078] In some embodiments, one or more of the aforementioned activation cocatalysts are used in combination with each other. Particularly preferred combinations are mixtures of tris((C1-C4)alkyl)aluminum, tris((C1-C4)alkyl)borane, or ammonium borate with oligomeric or polymeric aluminum oxane compounds. The ratio of the total molar number of one or more metal-ligand complexes of formula (I) to the total molar number of one or more activation cocatalysts in the activation cocatalyst is from 1:10,000 to 100:1. In some embodiments, the ratio is at least 1:5000, in some other embodiments at least 1:1000; and 10:1 or less, and in some other embodiments 1:1 or less. When an aluminum oxane is used alone as an activation cocatalyst, preferably, the molar number of the aluminum oxane used is at least 100 times the molar number of the metal-ligand complex of formula (I). In some other embodiments, when tris(pentafluorophenyl)borane is used alone as an activation cocatalyst, the molar ratio of tris(pentafluorophenyl)borane to the total molar ratio of one or more metal-ligand complexes of formula (I) is from 0.5:1 to 10:1, 1:1 to 6:1, or 1:1 to 5:1. The remaining activation cocatalyst is typically used in a molar amount approximately equal to the total molar amount of one or more metal-ligand complexes of formula (I).

[0079] Cast stretch film

[0080] A cast stretch film comprising a polyethylene composition is also disclosed, the polyethylene composition being characterized by having the following: (a) 0.910 g / cm³ 3 Up to 0.945 g / cm 3 (a) density; (b) melt index (I2) of 0.5 g / 10 min to 7 g / 10 min; (c) a first polyethylene fraction having a single peak in the temperature range of 40 °C to 85 °C in the elution curve obtained by the modified comonomer composition distribution (iCCD) analysis method; (d) a second polyethylene fraction having at least one peak in the temperature range of 90 °C to 115 °C in the elution curve obtained by the iCCD analysis method, wherein the area fraction of the second polyethylene fraction is the area below the peak of the second polyethylene fraction in the elution curve between 90 °C and 115 °C, and wherein the area fraction of the second polyethylene fraction accounts for at least 30% of the total area of ​​the elution curve; and (e) a MWCDI value less than 0. In the implementation scheme, the cast stretch film may be formed from the same or similar polyethylene composition described above and herein (e.g., the polyethylene composition of the cast stretch film may have the same properties as the polyethylene composition described above, or may not be limited thereto, for example, it may not necessarily have only a “single peak” in the second polyethylene fraction or may not necessarily have a peak width of less than 4.0°C in the second polyethylene fraction at 50% peak height).

[0081] The cast stretch film according to the embodiments disclosed herein can be formed by any conventional method known in the art. Typically, cast stretch films are formed by a cast film extrusion process, in which a polyethylene composition is melted through a slit or flat die to form a thin molten sheet or film. The film is then fixed to the surface of a cooling roller (typically a water-cooled and chrome-plated cooling roller) by a blower from an air knife or vacuum chamber. The film is immediately quenched and then its edges are cut before winding. The film can be cold-stretched in the longitudinal and / or transverse directions without the application of heat, and it can maintain tension for a long time when stretched around a load.

[0082] In some embodiments, the cast stretch film is a single-layer film. In other embodiments, the cast stretch film is a multilayer film. In some embodiments of multilayer films comprising the polyethylene composition disclosed herein, the multilayer film may include the polyethylene composition disclosed herein in the inner layers and / or also in the surface layers. The amount of polyethylene composition used in the cast stretch film of this embodiment may depend on many factors, including, for example, whether the film is a single-layer or multilayer film, the other layers in the film (if it is a multilayer film), the end use of the film, etc.

[0083] The cast stretch film of this disclosure can have a variety of thicknesses. The thickness of the cast stretch film depends on many factors, including, for example, whether the film is a single-layer or multilayer film, the other layers in the film (if it is a multilayer film), the desired properties of the film, the application in which the film is ultimately used, the equipment available for manufacturing the film, etc. In some embodiments, the cast stretch film of this disclosure has a thickness of up to 10 mils. For example, the cast stretch film can have a thickness from a lower limit of 0.2 mils, 0.5 mils, 0.7 mils, 1.0 mils, 1.75 mils, or 2.0 mils to an upper limit of 4.0 mils, 6.0 mils, 8.0 mils, or 10 mils.

[0084] In embodiments where the cast-stretched film is a multilayer film, the number of layers in the film can depend on many factors, including, for example, the desired properties of the film, the desired thickness of the film, the content of other layers in the film, the end use of the film, and the equipment available for manufacturing the film. In various embodiments, the cast-stretched film may include up to 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 layers.

[0085] In embodiments where the cast stretch film is a multilayer film, the cast stretch film may include other layers, such as a surface layer, an adhesive layer, and / or a release layer. For example, the cast stretch film according to the embodiments disclosed herein may also include other layers typically included in the cast stretch film structure, which, depending on the application, include, for example, other skin layers, adhesive layers, release layers, barrier layers, sealant layers, bonding layers, polyethylene layers, and / or polypropylene layers. In further embodiments, a printing layer may be included, which may be an ink layer displaying product details and other packaging information in various colors.

[0086] According to some embodiments, the polyethylene compositions disclosed in this invention can be incorporated into cast stretch films and articles that primarily (if not substantially or entirely) comprise polyethylene to provide films and articles that are easier to recycle. For example, in addition to other advantages that can be provided by using such polymers, cast stretch films in which the membrane primarily comprises polyethylene can have improved recyclability characteristics. In some embodiments, the cast stretch film comprises 95% by weight or more polyethylene based on the total weight of the film. In other embodiments, the cast stretch film comprises 96% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more polyethylene based on the total weight of the film. In yet another embodiment, the cast stretch film does not contain polypropylene.

[0087] Exemplary properties of cast stretch films comprising polyethylene compositions produced according to embodiments disclosed and described herein will now be provided. The molecular composition of the polyethylene composition can affect the properties of the cast stretch film. The properties of the cast films disclosed herein can be combined in any way within the scope of this disclosure. The following film properties were measured on cast stretch films produced as disclosed above (without mixing the polyethylene composition with another polymer) and having a thickness of about 0.6 mils.

[0088] In the embodiments, the cast stretch film has an average ultimate tensile strength in the range of 200% to 500% at a film width of 0.6 mils and 20 inches. This document discloses and includes all individual values ​​and sub-ranges of 200% to 500%. For example, the cast stretch film may have an average ultimate tensile strength of 200% to 500%, 200% to 475%, 200% to 450%, 250% to 500%, 250% to 475%, 250% to 450%, 300% to 500%, 300% to 475%, 300% to 450%, 325% to 500%, 325% to 475%, or 325% to 450%, wherein the average ultimate tensile strength can be measured according to the test methods described below.

[0089] In the implementation, the cast stretched film has an average tear time of at least 5 seconds at a thickness of 0.6 mils and a film width of 20 inches. This document discloses and includes all individual values ​​and sub-ranges of at least 5 seconds. For example, the cast stretched film may have an average tear time (ESTL tear) of at least 5 s, at least 6 s, at least 7 s, at least 8 s, at least 9 s, or at least 10 s measured at a thickness of 0.6 mils and a film width of 20 inches, or may have an average tear time (ESTL tear) within the range of 5 s to 30 s, 7 s to 30 s, 8 s to 30 s, 9 s to 30 s, 5 s to 25 s, 6 s to 25 s, 7 s to 25 s, 8 s to 25 s, 9 s to 25 s, or 10 s to 25 s measured at a thickness of 0.6 mils and a film width of 20 inches. The tear time (ESTL tear) may be measured according to the test methods described below.

[0090] In the implementation, the cast stretch film has an average pallet tear (OPT) of 10.0 lbs to 20.0 lbs, measured at a thickness of 0.6 mils and a film width of 20 inches. This document discloses and includes all individual values ​​and sub-ranges of 10.0 lbs. to 20 lbs. For example, the cast stretch film may have an average pallet tear (OPT) of 10.0 lbs. to 18 lbs., 10.0 lbs. to 16 lbs., 10 lbs. to 14 lbs., 11 lbs. to 20 lbs., 11 lbs. to 18 lbs., 11 lbs. to 16 lbs., 11 lbs. to 14 lbs., 12 lbs. to 20 lbs., 12 lbs. to 18 lbs., or 12 lbs. to 16 lbs., measured at a thickness of 0.6 mils and a film width of 20 inches. The pallet tear (OPT) may be measured according to the test methods described below.

[0091] The cast stretch film of the embodiment has an average pallet puncture (OPP) of 10.0 lbs. to 15.0 lbs., such as 10.5 lbs. to 15.0 lbs., 11.0 lbs. to 14.0 lbs., 10.5 lbs. to 13.0 lbs., 11.0 lbs. to 15.0 lbs., 11.0 lbs. to 14.0 lbs., or 11.0 lbs. to 13.0 lbs., measured using a Type A load test at a thickness of 0.6 mils and a film width. The pallet puncture using the Type A load test can be measured according to the test method described below.

[0092] Test methods

[0093] density

[0094] Density was measured according to ASTM D792 and expressed in grams per cubic centimeter. 3 (g / cm3 )express.

[0095] Melt index (I2)

[0096] Melt index (I2) was measured at 190°C and 2.16 kg according to ASTM D-1238. Values ​​are reported in g / 10 min, corresponding to the number of grams eluted per 10 min.

[0097] Conventional gel permeation chromatography (GPC)

[0098] The chromatographic system consisted of a PolymerChar GPC-IR (Valencia, Spain) high-temperature GPC chromatograph equipped with an internal IR5 infrared detector (IR5). The autosampler oven chamber was set to 160°C, and the column chamber to 150°C. Four Agilent "MixedA" 30 cm 20 μm linear mixed-bed columns were used. The chromatographic solvent was 1,2,4-trichlorobenzene containing 200 ppm of butylated hydroxytoluene (BHT). The solvent source was nitrogen injection. The injection volume was 200 μL, and the flow rate was 1.0 mL / min.

[0099] The calibration of the GPC column was performed using at least 20 narrow molecular weight distribution polystyrene standards in the range of 580 to 8,400,000 g / mol, arranged in a six-component "cocktail" mixture, with individual molecular weights spaced at least ten times apart. The standards were purchased from Agilent Technologies. For molecular weights equal to or greater than 1,000,000 g / mol, the polystyrene standards were prepared at 0.025 g per 50 mL of solvent, and for molecular weights less than 1,000,000 g / mol, at 0.05 g per 50 mL of solvent. The polystyrene standards were dissolved by gentle stirring at 80 °C for 30 minutes. The molecular weight of the polystyrene standard peaks was converted to ethylene-based polymer molecular weights using Equation 5 (as described in Williams and Ward, *Journal of Polymer Science: Polymer Letters*, 6,621 (1968)).

[0100] M 聚乙烯 =A×(M) 聚苯乙烯 ) B (Equation 1)

[0101] Where M is the molecular weight, A has a value of 0.4315, and B equals 1.0.

[0102] A fifth-order polynomial was used to fit the corresponding ethylene-based polymer-equivalent calibration point. Small adjustments (from approximately 0.375 to 0.440) were made to A using homopolymer polyethylene standards with a molecular weight of 120,000 g / mol to correct for column resolution and band broadening effects.

[0103] Total plate counts were performed on the GPC column assembly using decane (“prepared as 0.04 g in 50 mL TCB”, dissolved under slow stirring for 20 min). Plate counts (Equation 2) and symmetry (Equation 3) were measured at 200 μL injections according to the following equations:

[0104]

[0105] Where RV is the retention volume in milliliters, peak width is in milliliters, peak maximum is the maximum height of the peak, and half height is half the height of the peak maximum.

[0106]

[0107] Where RV is the retention volume in milliliters, and peak width is in milliliters, peak maximum is the position of the peak maximum, one-tenth height is one-tenth of the peak maximum height, and a subsequent peak refers to the tail of a peak at a retention volume later than the peak maximum, while a preceding peak refers to the front of a peak at a retention volume earlier than the peak maximum. The plate count of the chromatographic system should be greater than 22,000, and the symmetry should be between 0.98 and 1.22.

[0108] Samples were prepared semi-automatically using PolymerChar Instrument Control software, with a target sample weight of 2 mg / mL. Solvent (containing 200 ppm BHT) was added to a pre-bubbled, diaphragm-capped vial via a PolymerChar high-temperature autosampler. The sample was dissolved at 160°C for 3 hours with "low-speed" shaking.

[0109] Based on the GPC results obtained using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph according to Equations 3 to 6, the PolymerChar GPCOne was used. TM Software, at each equally spaced data collection point i (IR) i The IR chromatogram at point i (M) minus the baseline and the result from point i (M) according to Equation 1 聚乙烯,i The M-value was determined by using a narrow standard calibration curve (in g / mol) to obtain the polymer equivalent molecular weight based on ethylene. n(GPC) M w(GPC) and M z(GPC) The calculation.

[0110] Number average molecular weight M n(GPC) Weight-average molecular weight M w(GPC) and z-average molecular weight M z(GPC) It can be calculated using the following equation.

[0111]

[0112]

[0113]

[0114] To monitor deviations over time, a flow rate marker (decane) was introduced into each sample via a micropump controlled by the PolymerChar GPC-IR system. This flow rate marker (FM) was used to linearly correct the pump flow rate (nominal flow rate) for each sample by comparing the RV (RV(FM sample)) of the corresponding decane peak within the sample with the RV (RV(FM calibrated)) of the decane peak within the narrow standard calibration. It was then assumed that any variation in the decane marker peak time was linearly correlated with the flow rate (effective flow rate) throughout the run. To achieve the highest accuracy in the RV measurement of the flow marker peak, a least-squares fitting procedure was used to fit the peak values ​​of the flow marker concentration chromatogram to a quadratic equation. The first derivative of the quadratic equation was then used to solve for the true peak position. After calibrating the system based on the flow marker peak, the effective flow rate (relative to the narrow standard calibration) was calculated according to Equation 7. (Performed via PolymerChar GPCOne) TM The software processes the flow marker peaks. Acceptable flow rate correction ensures that the effective flow rate is within 0.5% of the nominal flow rate.

[0115]

[0116] Improved iCCD method for analyzing comonomer composition distribution

[0117] An improved method for comonomer content analysis (iCCD) was developed in 2015 (Cong and Parrott et al., WO2017040127A1). iCCD tests were performed using a Crystallization Elution Fractionation (CEF) instrument (Perimocha, Spain) equipped with an IR-5 detector (PolymerChar, Spain) and a two-corner light scattering detector model 2040 (Precision Detectors, now Agilent Technologies). A protective column filled with 20-27 micron glass (MoSCi Corporation, USA) was installed just before the IR-5 detector in the detector oven. o-Dichlorobenzene (ODCB, 99% anhydrous or industrial grade) was used. The results were obtained from EMD. Chemicals obtained silica gel 40 (particle size 0.2–0.5 mm, catalog number 10181-3) (which could previously be used as a solvent for drying ODCB). The dried silica was packed into three empty HT-GPC columns to further purify ODCB as the eluent. The CEF instrument was equipped with an autosampler with N2 sweep capability. ODCB was bubbled with dry nitrogen (N2) for one hour before use. Sample preparation was performed at 160°C with shaking at a concentration of 4 mg / mL (unless otherwise specified) using an autosampler for 1 hour. The injection volume was 300 μL. The iCCD temperature profile was as follows: crystallization from 105°C to 30°C at 3°C / min, thermal equilibration at 30°C for 2 minutes (including elution time for the soluble fraction set to 2 minutes), and elution from 30°C to 140°C at 3°C / min. The flow rate during crystallization was 0.0 mL / min. The flow rate during elution was 0.50 mL / min. Data were collected at a rate of one data point per second.

[0118] The iCCD column was filled with gold-plated nickel particles (Bright7GNM8-NiS, Nippon Chemical Industrial Co.) in a 15cm (length) × 1 / 4” (ID) stainless steel tube. The column was filled and conditioned using a slurry method, following references (Cong, R.; Parrott, A.; Hollis, C.; Cheatham, M. WO2017040127A1). The final pressure of the TCB slurry filling was 150 bar.

[0119] Column temperature calibration was performed using a mixture of a reference material, linear homopolymer polyethylene (with zero comonomer content, melt index (I2) of 1.0, polydispersity Mw / Mn of approximately 2.6 by conventional gel permeation chromatography, 1.0 mg / ml) and ODCB containing eicosane (2 mg / ml). The iCCD temperature calibration consisted of four steps: (1) calculating the delay volume, which was defined as the measured peak elution temperature of eicosane minus the temperature bias between 30.00 °C and the measured peak elution temperature; and (2) subtracting the temperature bias of the elution temperature from the raw iCCD temperature data. It should be noted that the temperature bias is a function of experimental conditions, such as elution temperature, elution flow rate, etc.; (3) Create a linear calibration line by switching the elution temperature in the range of 30.00℃ to 140.00℃, so that the linear homopolymer polyethylene reference has a peak temperature of 101.0℃ and the eicosane has a peak temperature of 30.0℃; (4) For the soluble fraction measured isothermally at 30℃, the elution temperature below 30.0℃ is linearly extrapolated by using an elution heating rate of 3℃ / min, according to the reference (Cerk and Cong et al., US9,688,795).

[0120] A relationship between comonomer content and elution temperature of iCCD was constructed using 12 reference materials (ethylene homopolymers and ethylene-octene random copolymers prepared with unit-point metallocene catalysts, with ethylene equivalent weight-average molecular weights ranging from 35,000 to 128,000). All these reference materials were analyzed in the same manner as previously specified at 4 mg / mL. The reported elution peak temperatures followed the following comparison of octene mol% for iCCD at R0.9842. 2 The elution temperature curve (curve 1).

[0121]

[0122] By assuming a shape factor of 1 and all virial coefficients equal to zero, the molecular weight of the polymer and polymer fractions were determined directly from the LS detector (90-degree angle) and the concentration detector (IR-5) according to the Rayleigh-Gans-Debys approximation (Striegel and Yau, Modern Size Exclusion Liquid Chromatogram, pp. 242 and 263). An integration window was set to integrate all chromatograms over an elution temperature range of 23.0 °C to 120 °C (temperature calibration specified above).

[0123] Calculating molecular weight (Mw) from an iCCD involves the following steps:

[0124] 1) Measurement of detector bias. Bias is defined as the geometric volume bias between the LS detector and the concentration detector. It is calculated as the difference in elution volume (mL) of the polymer peak between the concentration detector and the LS chromatogram. This is converted to temperature bias using elution heat rate and elution flow rate. Linear high-density polyethylene (zero comonomer content, melt index (I2) 1.0) was used, and polydispersity M2 was measured by conventional gel permeation chromatography. w / M n Approximately 2.6). The same experimental conditions as the normal iCCD method described above were used, except for the following parameters: crystallization from 140°C to 137°C at 10°C / min, followed by 1 minute of thermal equilibration at 137°C as the elution time for the soluble fraction (SF), and elution from 137°C to 142°C at 3°C / min. The flow rate during crystallization was 0.0 mL / min. The flow rate during elution was 0.80 mL / min. The sample concentration was 1.0 mg / mL. 2) Before integration, each LS data point in the LS chromatogram was shifted to correct for detector bias. 3) The baseline from the LS and concentration chromatograms over the entire elution temperature range of step 1) was integrated. The MW detector constant was calculated using known MW HDPE samples in the range of 100,000 to 140,000 Mw and the area ratio of the integrated LS and concentration signals. 4) The Mw of the polymer was calculated by using the ratio of the integrated light scattering detector (90-degree angle) to the concentration detector and by using the MW detector constant.

[0125] For the second elution peak between 35.0℃ and 119.0℃, the peak width (also known as half-maximum width at half-peak) of the second fraction at 50% peak height is calculated using iCCD. The peak width of the second fraction at 50% peak height is determined by taking half of the maximum elution temperature of the second elution peak and calculating the temperature difference between the front and back temperatures of the second elution peak at half the total height.

[0126] Molecularly weighted comonomer distribution index (MWCDI)

[0127] The GPC-IR high-temperature chromatography system from Perimocha (Valencia, Spain) was equipped with a precision detector (Amherst, MA), a Model 2040 2-angle laser scattering detector, an IR5 infrared detector (GPC-IR), and a 4-capillary viscometer, all from Perimocha. A 15-degree angle of the light scattering detector was used for computational purposes. Data collection was performed using Perimocha's Instrument Control software and data acquisition interface. The system was equipped with an online solvent degassing unit and pumping system from Agilent Technologies (Santa Clara, CA).

[0128] The injection temperature was controlled at 150°C. The columns used were four 20-micron PLGel Mixed-A light scattering columns from Agilent Technologies. The solvent was 1,2,4-trichlorobenzene. The sample was prepared as described in the standard GPC section of this report. Both the chromatographic solvent and the sample preparation solvent contained 200 ppm butylated hydroxytoluene (BHT). Both solvent sources were bubbled with nitrogen. The ethylene-based polymer sample was gently stirred at 160°C for three hours. The injection volume was 200 μL, and the flow rate was 1 mL / min.

[0129] GPC column calibration was performed using 21 polystyrene standards with narrow molecular weight distributions ranging from 580 g / mol to 8,400,000 g / mol. These standards were arranged in six "mixture" solutions, with individual molecular weights spaced at least tenfold apart. The standards were purchased from Polymer Laboratories (Shropshire, UK). The polystyrene standards were prepared as follows: for molecular weights equal to or greater than 1,000,000 g / mol, 0.025 g in 50 mL of solvent; and for molecular weights less than 1,000,000 g / mol, 0.050 g in 50 mL of solvent. The polystyrene standards were dissolved by gentle stirring at 80°C for 30 minutes. The narrow standard mixtures were operated first, following a decreasing order of the highest molecular weight components to minimize degradation. The peak molecular weight of the polystyrene standard was converted to the molecular weight of polyethylene using Equation 8 (as described by Williams and Ward, *Journal of Polymer Science and Polymer Letters*, 6, 621 (1968)).

[0130] Mpolyethylene = A × (Mpolystyrene) B (Equation 8),

[0131] Where M is the molecular weight, A is approximately 0.4315, and B equals 1.0. The value of A is adjusted between 0.375 and 0.444 (depending on the specific column setup efficiency) so that the weight-average molecular weight of linear polyethylene corresponds to 120,000 g / mol as calculated by the following Equation 10:

[0132]

[0133]

[0134] In Equations 9 and 10, RV is the column retention volume collected at "1 point / second" (linearly spaced). IR is the IR detector signal from the measurement channel of the GPC instrument minus the baseline, in volts, and LogM PE The polyethylene equivalent in MW is determined from Equation 8. The data was calculated using GPC One software from Perimocha.

[0135] Using known short chain branching (SCB) frequencies (e.g., by...) 13 At least ten vinyl polymer standards (polyethylene homopolymer and ethylene / octene copolymer) measured by the C10 NMR method were calibrated quantitatively using an IR5 detector, wherein the short-chain branching frequency was in the range of approximately 50 SCB / 1,000 total C for homopolymers (0 SCB / 1,000 total C), where total C = carbon in the main chain + carbon in the branches. The weight-average molecular weight of each standard was from 36,000 g / mol to 126,000 g / mol, as determined by the GPC-LALS processing method described above. The molecular weight distribution (Mw / Mn) of each standard was from 2.0 to 2.5, as determined by the GPC-LALS processing method described above.

[0136] For each of the “SCB” standards, calculate the “IR5 area ratio” (or “IR5 area ratio”) of the “area response of the IR5 methyl channel sensor minus the baseline” to the “area response of the IR5 measurement channel sensor minus the baseline”. 甲基通道面积 / IR5 测量通道面积 (e.g., standard filters and filter wheels supplied by PolymerChar: part number IR5_FWM01 included as part of the GPC-IR instrument). The linear fit between the SCB frequency and the "IR5 area ratio" is constructed in the form of Equation 11:

[0137] SCB / 1000 total C = A0 + [A1 × (IR5)] 甲基通道面积 / IR5 测量通道面积 (Equation 11)

[0138] Where A0 is the zero intercept of "SCB / 1,000 total C" under "IR5 area ratio", and A1 is the slope of "SCB / 1,000 total C" relative to "IR5 area ratio" and represents the increase of SCB / 1,000 total C as "IR5 area ratio" changes.

[0139] A series of linear subtractions of baseline chromatographic height from the chromatograms generated by the IR5 methyl channel sensor were established as a function of column elution volume to produce baseline-corrected chromatograms (methyl channel). A series of linear subtractions of baseline chromatographic height from the chromatograms generated by the IR5 measurement channel were also established as a function of column elution volume to produce baseline-corrected chromatograms (measurement channel).

[0140] At each column elution volume index (each equally spaced index representing 1 data point per second at 1 mL / min elution) at both ends of the sample integration limit, calculate the "IR5 height ratio" of the "baseline-corrected chromatogram (methyl channel)" versus the "baseline-corrected chromatogram (measurement channel)". Multiply the "IR5 height ratio" by a coefficient A1 and add a coefficient A0 to this result to produce the predicted SCB frequency of the sample. Convert the result to comonomer molar percentage in Equation 12 as follows:

[0141] Comonomer molar percentage = {SCB f / [SCB f +((1,000-SCB f *Length of comonomer) / 2)]}*100 (Equation 12), where "SCB f "SCB per 1000 total C" and "length of comonomer" = 8 for octene, 6 for hexene, etc.

[0142] Each elution volume index was converted to a molecular weight value (Mw) using the method of Williams and Ward. i (As described above; (Equation 8). Plot the "comonomer molar percentage (y-axis)" as Log(Mw i The function is used to calculate Mw at 50,000 / mol. i With 750,000 g / mol Mw i The slope between (end-group corrections at the chain ends are omitted for this calculation). EXCEL linear regression was used to calculate the slope between 50,000 g / mol and 750,000 g / mol (including the ends). This slope was defined as the molecularly weighted comonomer distribution index (MWCDI = Molecularly Weighted Comonomer Distribution Index).

[0143] A representative determination of the MWCDI of the composition is provided in U.S. Patent No. 10,138,362B2, which is incorporated herein by reference in its entirety.

[0144] Zero shear viscosity ratio (ZSVR)

[0145] ZSVR is defined as the ratio of the zero-shear viscosity (ZSV) of branched polyethylene to that of linear polyethylene at equivalent weight-average molecular weight (Mw-gpc), according to the following equations (EQ) 13 and 14:

[0146]

[0147]

[0148] ZSV values ​​were obtained by creep testing at 190°C using the method described above. Mw-gpc values ​​were determined by the conventional GPC method (Equation 5 in the conventional GPC method description). The correlation between ZSV and Mw-gpc for linear polyethylene was established based on a series of linear polyethylene reference materials. A description of the ZSV-Mw relationship can be found in the following literature: ANTEC Conference: Karjala, Teresa P., Sammler, Robert L., Mangnus, Marc A., Hazlitt, Lonnie G., Johnson, Mark S., Hagen, Charles M. Jr., Huang, Joe WL, Reichek, Kenneth N., “Detection of low levels of long-chain branching in polyolefins”, Annual Technical Conference of the Society of Plastics Engineers (2008), Vol. 66, pp. 887-891.

[0149] Stretch film test

[0150] Stretching technology is characterized by the use of application-specific testing to predict performance in that field. A key part of application testing involves testing the film under stretched conditions, which simulates the performance during stretch packaging. For all film tests, samples with a thickness of 0.6 mils and a width of 20 inches are tested. Two types of stretch tests are performed on the produced films in a stretching laboratory. One approach involves using the ESL Film Performance Tester, which has been developed to provide stretch film testing under representative conditions. The ESL Film Performance Tester is used to measure ultimate tensile strength, which represents the maximum level of stretch that can be applied during pallet packaging. It is also used to perform tear propagation testing to analyze the tear performance of the film during stretch conditions.

[0151] The second set of tests used a Lantech stretch packer, which is equipped with a 44-inch × 35-inch × 60-inch metal frame to simulate pallet packaging. Tests conducted using this apparatus obtained the film's mechanical properties or abuse characteristics, as well as its ability to withstand uniform loads and its adhesion values.

[0152] Ultimate Stretch (US)

[0153] Ultimate tensile strength was measured using an ESL membrane performance tester (ESTL, Deerlijk, Belgium) - FPT-750 membrane performance tester. Select the ultimate tensile strength test from the test menu, and then select the W-winding method. Table A provides the equipment settings for this method. Unwinding force, coiling force, peel force, tensile force, peel angle, and sound level were measured as a function of pre-stretch. Pre-stretch was increased until the breaking point. The coiling speed was kept constant at 360 feet / minute during the test. The test was repeated three times, and the average ultimate tensile strength (US) was reported as a percentage (%) of ultimate tensile strength.

[0154] Table A

[0155] Strain begins ％ 200.0 strain interval ％ 10.0 linear velocity ft / min 360 Unwinding and Adapting ％ 6.7 Curl strain ％ 4

[0156] Pallet puncture – Type A load (OPP-A)

[0157] This test uses the Bruceton step method to determine the maximum load force at which the membrane can pass through three wraps with a test probe without failure. The test probe is inserted into the test stage with the desired protrusion distance. Type A loads are tested with a 3-inch probe; Type B loads with a 6-inch probe; and Type C loads with a 12-inch probe. The membrane is positioned such that the test probe is aligned with the center of the membrane. The membrane is attached to the test stage and the packer is started. Once the packer reaches 250% pre-stretch, the membrane is allowed to pass through the probe up to three times. Starting with a low F2 force of 7 lbs, the membrane is packed three times. If the membrane is not punctured by the probe, the test is repeated in increments of 0.5 lbs at an increased F2 force until failure. At each 0.5 lb increment, the membrane is manually pushed onto the probe and a new set of membranes is tested. Any breakage of the membrane during any packing is considered a failure at that force to load setting. Depending on the membrane's performance at the load setting (i.e., pass or fail), the load force is increased or decreased, and the test is repeated at the new load setting. This test continues until the maximum force at which failure is greater than 50% is found. The failure F2 force represents the pallet puncture value of the membrane and is generally not reported unless the test is repeated more than twice starting from 7 lbs. The highest passing F2 force is reported, where data significance is considered to be + / - 1 lb. It should be understood that the Type A load test is commonly used in pallet packaging, and those skilled in the art will recognize its meaning as used herein. Table B provides the equipment and setup used in this method.

[0158] Table B

[0159] equipment Lantech SHC film test packaging Pre-stretching 250％ Turntable speed 10rpm The force of the load (F2) Variable probe type 4”×4” blunt rod Probe protrusion distance 12 inches

[0160] Pallet puncture – Type B load (OPP-B)

[0161] If the combined pallet is non-uniform in shape and has limited irregularities, it is defined as a “Type B load.” The test uses the Bruceton step method to determine the maximum load force that a membrane can withstand three overlapping wraps with a test probe without failure. The test probe is inserted into the test stage with the desired protrusion distance. All membranes are tested using 2-inch by 2-inch blunt metal probes extending 6 inches. The membrane is positioned such that the test probe is aligned with the center of the membrane. The membrane is attached to the test stage and the packer is started. Once the packer reaches 250% pre-stretch, the membrane is allowed to pass through the probe up to three times. Starting with a stretched membrane tension / load force (F2) of 7 lbs, the membrane is packed three times. If the membrane is not punctured by the probe, the test is repeated in increments of 0.5 lbs at an increased F2 force until failure. Any breakage of the membrane during any packing is considered failure at that force-to-load setting. Once the F2 force reaches the point where failure begins, the test is repeated 6 times at a force setting. If the membrane passes 4 out of 6 tests, the membrane F2 force is increased. If the membrane fails in 4 out of 6 tests, the test is stopped, and this is considered the membrane failure point. Based on the membrane's performance under the load setting (i.e., passing or failing), the load force is increased / decreased, and the test is repeated under the new load setting. The test continues until the maximum force at which failure greater than 50% is found. The highest passing F2 force is reported as the pallet puncture (OPP) value. A standard variation of + / - 1 lb is observed in this test. It should be understood that the Type B load test is commonly used for pallet packaging, and those skilled in the art will recognize its meaning as used herein. Table C below provides the equipment and setup used in this method.

[0162] Table C

[0163] equipment Lantech SHC film test packaging Pre-stretching 250％ Turntable speed 10rpm The force of the load (F2) Variable probe type 2”×2” blunt rod Probe protrusion distance 6 inches

[0164] OPT (Optical Delivery Tear)

[0165] This test uses the Bruceton step method to determine the maximum load force that the membrane can withstand to initiate puncture on a test probe with a fixed blade. The test probe is inserted into the test stage with the desired protrusion distance. The membrane is positioned such that the test probe is aligned with the center of the membrane. The membrane is attached to the test stage and the packer is initiated. Once the packer reaches 250% pre-stretch, the membrane is allowed to pass through the probe; for this test, a single-layer membrane is tested. The membrane tension (F2 force) is increased in increments of 0.5 lbs. from an initial low of approximately 7 lbs. until the membrane is completely torn in either the transverse direction (CD) or transverse direction (TD). The pallet tear value is recorded as the highest F2 force that causes the initial puncture to fail without propagating across the entire width of the membrane, resulting in its failure. Table D provides the equipment and setup used in this method.

[0166] Table D

[0167] equipment Lantech SHC film test packaging Pre-stretching 250％ Turntable speed 17rpm The force of the load (F2) Variable probe type 4” x 4” blunt rod with razor blades fixed on it Probe protrusion distance 5 inches

[0168] Tear propagation / rupture time (ESTL tear)

[0169] Tear propagation / rupture time was measured using an ESL membrane performance tester (ESTL, Deerlijk, Belgium) - FPT-750 membrane performance tester. Select "Tear Propagation" from the test menu, then select the W packaging method. Table E provides the parameters selected on the device to measure rupture time (ESTL tear). The sample cast stretch membrane is placed in a pre-stretched and tensioned state, and then the membrane is clamped. A small vertical cut is made in the membrane using a small "spear-shaped knife." Once this cut is made, the canvas is released from the membrane. After one second, the reel begins to pull the membrane at a constant speed. Other shafts are blocked. This creates tension in the membrane after the initial cut. The FPT-750 membrane property tester monitors how long it takes and how much force is required to break the entire membrane height. The test is repeated 3 times and the average rupture time is reported in seconds (s).

[0170] Table E

[0171] Strain begins ％ 250.0 linear velocity ft / min 195 puncture probe increase Unwinding tension Pound Power 6.70 Curl strain ％ 10.0 Load tension ％ 285.0

[0172] Example

[0173] Preparation of the polyethylene composition (polymer 1 and polymer 2) of the present invention

[0174] The polyethylene compositions of the present invention (“Polymer 1” and “Polymer 2”) are prepared according to the following methods and tables.

[0175] All feedstocks (monomers and comonomers) and process solvents (narrow-boiling-range, high-purity isoparaffin solvent, Isopar-E) were purified using molecular sieves before being introduced into the reaction environment. High-purity hydrogen was supplied via a shared pipeline and dried using molecular sieves. The monomer feed stream to the reactor was pressurized to above the reaction pressure via a mechanical compressor. The solvent feed stream was pressurized to above the reaction pressure via a pump. The comonomer feed stream was pressurized to above the reaction pressure via a pump. Individual catalyst components were manually diluted in batches with the purified solvent and pressurized to above the reaction pressure. All reaction feed streams were measured using mass flow meters and independently controlled by computer-automated metering pumps.

[0176] The reactor configuration is either a double parallel reactor operation or a double series reactor operation as specified in Table G.

[0177] The reactor can be a single reactor system, two reactor systems in parallel configuration, or two reactor systems in series configuration. Each reactor is a continuous solution polymerization reactor consisting of a fully liquid, adiabatic, and continuously stirred tank reactor (CSTR). All fresh solvent, monomer, comonomer (if present), hydrogen, and catalyst components can be independently controlled. The temperature of the total fresh feed stream (solvent, monomer, comonomer [if present], and hydrogen) entering each reactor is controlled by passing the feed stream through a heat exchanger, typically between 15–50°C, to maintain a single solution phase. All fresh feed to each polymerization reactor is injected into the reactor from one location. Fresh feed is controlled by receiving half the total fresh feed mass flow rate at each injector. The catalyst component is injected into the polymerization reactor separately from the other feeds. The main catalyst component feed is computer-controlled to maintain the reactor monomer conversion at a specified value. The cocatalyst component is fed based on a calculated specified molar ratio to the main catalyst component. A stirrer in the reactor is responsible for continuous mixing of the reactants. An oil bath provides some fine-tuning for reactor temperature control.

[0178] In a dual parallel reactor configuration, the effluent streams from the first polymerization reactor and the second polymerization reactor are combined before any further processing.

[0179] In a dual-series reactor configuration, the effluent from the first polymerization reactor (containing solvent, monomer, comonomer [if present], hydrogen, catalyst components, and polymer) leaves the first reactor loop and is added to the second reactor separately from other feeds added to the second reactor.

[0180] In all reactor configurations, the final reactor effluent (either from a second reactor in a dual-tandem configuration, a combined effluent from two parallel configurations, or a single reactor effluent) enters a region where a suitable reagent (typically water) is added and reacts with the reagent to deactivate the final reactor effluent. At the same reactor outlet location, additional additives are added to stabilize the polymer (typical antioxidants suitable for extrusion and manufacturing processes, such as octadecyl 3,5-di-tert-butyl-4-hydroxycinnamate, tetra(methylene(3,5-di-tert-butyl-4-hydroxycinnamate))methane, and tris(2,4-di-tert-butyl-phenyl)phosphite, as well as acid scavengers, such as calcium stearate, if needed).

[0181] After catalyst deactivation and the addition of additives, the reactor effluent enters the devolatilization system, where polymers are removed from the non-polymer stream. The separated polymer melt is granulated and collected. The non-polymer stream is then removed from the system.

[0182] The reactor feed data stream corresponds to the values ​​and information in Tables F and G used for producing polyethylene compositions (polymer 1 and polymer 2). Figure 2 and Figure 3 The illustration is shown in the diagram.

[0183] Table F – Catalysts for Polymer 1 and Polymer 2

[0184]

[0185] Table G

[0186]

[0187]

[0188] Commercially available polyethylene compositions

[0189] Polymer 3 is INNATE TM XUS.59910.08, a linear low-density polyethylene composition commercially available from The Dow Chemical Company, Midland, MI.

[0190] Polymer 4 is DOWLEX TM 2045, a linear low-density polyethylene composition commercially available from Dow Chemical Company, Midland, Michigan.

[0191] Polymer 5 is INNATE TM ST50 is a polyethylene composition commercially available from Dow Chemical Company in Midland, Michigan.

[0192] Preparation of the developed polyethylene compositions (polymers 6, 7, 8, and 9)

[0193] The developed polyethylene compositions (“Polymer 6”, “Polymer 7”, “Polymer 8” and “Polymer 9”) were prepared according to the following methods and tables.

[0194] All feedstocks (monomers and comonomers) and process solvents (narrow-boiling-range, high-purity isoparaffin solvent, Isopar-E) were purified using molecular sieves before being introduced into the reaction environment. High-purity hydrogen was supplied via a shared pipeline and dried using molecular sieves. The monomer feed stream to the reactor was pressurized to above the reaction pressure via a mechanical compressor. The solvent feed stream was pressurized to above the reaction pressure via a pump. The comonomer feed stream was pressurized to above the reaction pressure via a pump. Individual catalyst components were manually diluted in batches with the purified solvent and pressurized to above the reaction pressure. All reaction feed streams were measured using mass flow meters and independently controlled by computer-automated metering pumps.

[0195] The two reactor systems are used in series. Each continuous solution polymerization reactor consists of a liquid-filled, non-adiabatic isothermal loop reactor simulating a continuous stirred tank reactor (CSTR) with deheating. The feed of all fresh solvent, monomer, comonomer (if present), hydrogen, and catalyst components can be controlled independently. The temperature of the total fresh feed stream (solvent, monomer, comonomer [if present], and hydrogen) entering each reactor is typically controlled between 15–50°C to maintain a single solution phase by passing the feed stream through a heat exchanger. The total fresh feed to each polymerization reactor is injected into the reactor at two locations, with approximately equal reactor volumes between each injection point. The fresh feed is controlled by receiving half the total fresh feed mass flow rate at each injector. The catalyst component is injected into the polymerization reactor through a specially designed injection plug. The main catalyst component feed is computer-controlled to maintain the reactor monomer conversion at a specified value. The cocatalyst component is fed based on a calculated specified molar ratio to the main catalyst component. Immediately following the feed injection point of each reactor, the feed stream is mixed with the contents of the circulating polymerization reactor using a static mixing element. The contents of each reactor are continuously circulated through a heat exchanger, which removes most of the heat of reaction, and the coolant side temperature is responsible for maintaining the isothermal reaction environment at the specified temperature. Circulation around each reactor loop is provided by a pump.

[0196] The effluent from the first polymerization reactor (containing solvent, monomer, comonomer [if present], hydrogen, catalyst components and polymer) leaves the first reactor loop and is added to the second reactor separately from other feeds added to the second reactor.

[0197] The final reactor effluent (or the effluent from the second reactor in a dual-tandem configuration) enters a zone where a suitable reagent (water) is added and reacts with the suitable reagent to deactivate the final reactor effluent. At the same reactor outlet location, other additives are added to stabilize the polymer (typical antioxidants suitable for extrusion and manufacturing processes, such as octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, tetra(methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate))methane and tris(2,4-di-tert-butyl-phenyl)phosphite, and acid scavengers, such as calcium stearate, if necessary).

[0198] After catalyst deactivation and the addition of additives, the reactor effluent enters the volatilization system, where polymers are removed from the non-polymer stream. The separated polymer melt is granulated and collected. The non-polymer stream is separated by various devices that handle most of the ethylene removed from the system. Most of the solvent and unreacted comonomers are recycled back to the reactor after passing through a purification system. Small amounts of solvent and comonomers are removed from the process.

[0199] The reactor feed data stream corresponding to the values ​​and information in Tables H and I is used for the production of polyethylene compositions (polymers 6, 7, 8, and 9), such as... Figure 3 The diagram illustrates this. Presenting the data makes it easier to treat the complexities of solvent recycling systems and the reaction system as a once-through flow diagram, taking into account those complexities.

[0200] Table H - Catalysts for Polymers 6, 7, 8, and 9

[0201]

[0202] Table I

[0203]

[0204] Analysis of polyethylene samples

[0205] Polymers 1–9 were analyzed by iCCD and GPC. The density, melt number (I²), MWCDI, and zero-shear viscosity ratio (ZSVR) of the compositions were also measured. Data from the analysis and testing are recorded in Tables 1 and 1A. For example, the iCCD elution curves and GPC overlaps for polymer 1 are provided in Tables 1 and 1A. Figure 4 and Figure 5 middle.

[0206] Table 1

[0207]

[0208] *Not measured (NM)

[0209] Table 1A

[0210]

[0211] *Not measured (NM)

[0212] Three-layer and five-layer cast stretch films are manufactured on a five-layer Egan Davis Standard co-extrusion cast film production line. The casting line consists of three 2-1 / 2" and two 2" 30:1 L / D Egan Davis Standard MAC extruders, all air-cooled. All extruders have medium-operation DSB (Davis Standard Barrier) type screws. A microprocessor monitors and controls these operations. The extrusion process is monitored by pressure sensors located before and after the perforated plate, as well as four heater zones on each barrel (one on the adapter and one on the block, and two on the die head). The microprocessor also tracks extruder RPM, % FLA, HP, rate, linear speed, % stretch, primary and secondary cooling roll temperatures, metering deviation, layer ratio, rate / RPM, and melt temperature for each extruder.

[0213] The equipment specifications include a Cloeren 5-layer double-sided feed block and a Cloeren 36” Epoch III autogage 5.1 die. The primary cooling roller, 40” OD x 40” long, has a rough finish and a 30-40 RMS surface finish to improve die release characteristics. The secondary cooling roller, 20” OD x 40” long, has a 2-4 RMS surface finish to improve web tracking. Both primary and secondary cooling rollers have circulating cooling water to provide quenching. X-ray gauge sensors from Scantech are present for thickness measurement and automated measurement control (if required). Rate is measured via five Barron weighing hoppers, each with a load cell for weight analysis control. Samples are finished on a dual-position single-turntable Horizon winder with a center crimp automatic roll changeover and slitting station on a 3” ID core. The production line has a maximum production rate of 600 lbs / hour and a maximum line speed of 1200 ft / min.

[0214] The conditions for sample preparation are shown in Table 2.

[0215] Table 2

[0216]

[0217]

[0218] In addition to polymers 1–9, the following materials were also used to formulate the membranes of the present invention and the comparative membranes:

[0219] DR376_01 (“PP”) is a type of polypropylene that is commercially available from Braskem (Sao Paulo, Brazil).

[0220] ATTANE TM 4404G is an ultra-low density polyethylene copolymer commercially available from Dow Chemical Company in Midland, Michigan.

[0221] ELITE TM 5230G is a reinforced polyethylene resin commercially available from Dow Chemical Company in Midland, Michigan.

[0222] Three-layer and five-layer cast and stretched films were formed and named the film of the present invention and the comparative film. For each layer of the three-layer film, ATTANE was used in the outer layer (layer 1). TM 4404G; Using ELITE in another outer layer (layer 3) TM 5230G; and PP or polymer 1–polymer 5 are used in the inner layer (layer 2). Tables 3, 4, and 5 below provide formulations for three-layer comparative examples and embodiments of the present invention. For comparative membranes 2–4 and membrane 1 of the present invention, PP or polymers 3–5 account for 20% of the total membrane formulation.

[0223] Table 3

[0224] Percentage of total membrane Comparison Membrane 1 Layer 1 10％ <![CDATA[ATTANE TM 4404G]]> Layer 2 10％ PP Floor 3 80％ <![CDATA[ELITE TM 5230G]]>

[0225] Table 4

[0226] Percentage of total membrane Comparison Membrane 2 Comparison Membrane 3 Comparison membrane 4 Layer 1 10％ <![CDATA[ATTANE TM 4404G]]> <![CDATA[ATTANE TM 4404G]]> <![CDATA[ATTANE TM 4404G]]> Layer 2 20％ PP Polymer 4 Polymer 5 Floor 3 70％ <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]>

[0227] Table 5

[0228] Percentage of total membrane Membrane 1 of the present invention Layer 1 10％ <![CDATA[ATTANE TM 4404G]]> Layer 2 20％ Polymer 3 Floor 3 70％ <![CDATA[ELITE TM 5230G]]>

[0229] For each of the five layers of the membrane, ATTANE is used in the outer layer (layer 1). TM 4404G; ELITE is used in another outer layer (layer 5) and the core layer (layer 3). TM 5230G; and polymers 1–9 are used in the inner layers (layers 2 and 4). Tables 6, 7, and 7A below provide formulations of five comparative and inventive embodiments. For comparative membranes 5-6 and inventive membranes 2-4, polymers 1-9 comprise 30% of the total membrane formulation (i.e., 15% in layer 2 and 15% in layer 4).

[0230] Table 6

[0231] Percentage of total membrane Comparison membrane 5 Comparison Membrane 6 Layer 1 10％ <![CDATA[ATTANE TM 4404G]]> <![CDATA[ATTANE TM 4404G]]> Layer 2 15％ Polymer 4 Polymer 5 Floor 3 30％ <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]> Floor 4 15％ Polymer 4 Polymer 5 Floor 5 30％ <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]>

[0232] Table 7

[0233] Percentage of total membrane Membrane 2 of the present invention Membrane 3 of the present invention Membrane 4 of the present invention Layer 1 10％ <![CDATA[ATTANE TM 4404G]]> <![CDATA[ATTANE TM 4404G]]> <![CDATA[ATTANE TM 4404G]]> Layer 2 15％ Polymer 2 Polymer 3 Polymer 1 Floor 3 30％ <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]> Floor 4 15％ Polymer 2 Polymer 3 Polymer 1 Floor 5 30％ <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]> <![CDATA[ELITE TM 5230G]]>

[0234] Table 7A

[0235]

[0236] The properties of the membranes of the present invention and comparative membranes were measured according to the test methods disclosed herein, and are provided in Tables 8, 9, and 9A. The results show that, compared to comparative membranes 3 and 4, membrane 1 of the present invention exhibits a surprisingly high pallet tear and rupture time (ESTL tear). Similarly, compared to comparative membranes 5 and 6, membranes 2-8 of the present invention exhibit surprisingly high pallet tear and rupture time (ESTL tear).

[0237] Table 8

[0238]

[0239] *Not measured

[0240] Table 9

[0241]

[0242] *Not measured

[0243] Table 9A

[0244]

[0245] *Not measured

[0246] Unless expressly excluded or otherwise limited, every document cited herein (if any), including any cross-referenced or related patent or application and any patent application or patent claiming priority or benefit to this application, is hereby incorporated in its entirety by reference. No reference to any document acknowledges it as prior art to any invention disclosed or claimed herein, or as teaching, indicating, or disclosing any such invention, alone or in combination with any other referenced document. Furthermore, in the event of any conflict between the meaning or definition of any term in this document and the meaning or definition of the same term in any document incorporated by reference, the meaning or definition given to the term in this document shall prevail.

[0247] While specific embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that many other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications falling within the scope of the invention be covered in the appended claims.

Claims

1. A polyethylene composition, characterized in that... It has the following features: (a) 0.910 g / cm³ 3 Up to 0.945 g / cm 3 The density; (b) Melt index I2 from 0.5 g / 10 min to 7.0 g / 10 min; (c) The first polyethylene fraction with a single peak in the temperature range of 40°C to 85°C in the elution curve obtained by the improved iCCD analysis method of comonomer composition distribution. (d) A second polyethylene fraction having a single peak in the elution curve obtained by iCCD analysis within a temperature range of 90°C to 115°C, wherein the second polyethylene area fraction is the area below the peak of the second polyethylene fraction in the elution curve between 90°C and 115°C, wherein the second polyethylene area fraction accounts for at least 30% of the total area of ​​the elution curve, and wherein the peak width of the second polyethylene fraction at 50% peak height is less than 4.0°C; and (e) Distribution coefficient (MWCDI) of comonomers with a molecular weight less than 0.

2. The polyethylene composition according to claim 1, wherein the MWCDI value is less than -3.

3. The polyethylene composition according to claim 1 or 2, wherein the second polyethylene fraction has a weight-average molecular weight Mw of at least 95,000 g / mol.

4. The polyethylene composition according to claim 1 or 2, wherein the polyethylene composition is further characterized by having a molecular weight distribution in the range of 2.0 to 8.0, expressed as a ratio of weight-average molecular weight to number-average molecular weight, Mw / Mn.

5. The polyethylene composition according to claim 1 or 2, wherein the polyethylene composition is further characterized by having a zero shear viscosity ratio (ZSVR) of less than 3.

0.

6. The polyethylene composition according to claim 1 or 2, wherein the first polyethylene fraction of the polyethylene composition is formed in the presence of a first molecular catalyst, and the second polyethylene fraction of the polyethylene composition is formed in the presence of a second molecular catalyst.

7. A cast stretch film comprising a polyethylene composition, said polyethylene composition being characterized by having the following: (a) 0.910 g / cm³ 3 Up to 0.945 g / cm 3 The density; (b) Melt index I2 from 0.5 g / 10 min to 7 g / 10 min; (c) The first polyethylene fraction with a single peak in the temperature range of 40°C to 85°C in the elution curve obtained by the improved iCCD analysis method of comonomer composition distribution. (d) A second polyethylene fraction having at least one peak in the elution curve obtained by iCCD analysis, within a temperature range of 90°C to 115°C, wherein the second polyethylene area fraction is the area below the peak of the second polyethylene fraction in the elution curve between 90°C and 115°C, and wherein the second polyethylene area fraction accounts for at least 30% of the total area of ​​the elution curve; and (e) MWCDI values ​​less than 0.

8. The cast stretch film according to claim 7, wherein the peak width of the second polyethylene fraction at 50% peak height is less than 4.0°C.

9. The cast stretch film according to claim 7 or 8, wherein the cast stretch film has a pallet tear of 10.0 lbs. to 20.0 lbs. at a thickness of 0.6 mils and a film width of 20 inches.

10. The cast stretch film according to claim 7 or 8, wherein the cast stretch film has an average breakage time of at least 5 seconds.

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