Polyethylene film

Abstract

A biaxially oriented shrink film is provided comprising a metallocene linear low density polyethylene having a density in the range of from 0.900 g / cm3 to 0.940 g / cm3, a melt index (I2) in the range of from 0.1 g / 10 min to 5.0 g / 10 min, a melt index ratio (MIR) in the range of from 20 to 38, a molecular weight distribution (MWD) in the range of from 2.0 to 4.5, and a wide orthogonal comonomer distribution. In some embodiments, the shrink film provides sufficient shrink force at a temperature of less than 160 DEG C.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Application 63 / 502,865 entitled “Polyethylene Film”, filed May 17, 2023, the entire contents of which are incorporated herein by reference.

[0003] Invention Field

[0004] This disclosure relates to co-extrusion structures for finishing shrink films and polyethylene blends therefor. Background Technology

[0005] Finishing shrink (CS) involves using heat-shrink film to bundle items together. Finishing shrink is used in a very wide variety of applications and is especially used for secondary packaging of food or beverages. Examples include metal cans and plastic bottles.

[0006] Typically, the film is applied at room temperature and placed under a heat source to shrink. Suitable performance characteristics for shrink packaging lines include sufficient stiffness to allow the film to properly wrap around the packaged item, and sufficient dimensional shrinkage to ensure a tight fit. Films suitable for finishing shrinks must have high heat shrinkage force to ensure a tight fit and high tensile strength to withstand handling and abuse during transportation.

[0007] CS film is widely used in the beverage industry. For conventional CS film, the shrink tunnel operating temperature is typically between 180°C and 220°C, and even for thin CS film (e.g., 30 µm), the shrink tunnel temperature is above 150°C. There is a need for a low-temperature shrink CS film solution that can significantly save energy, improve packaging efficiency, and minimize the temperature impact on the contents of the packaged container.

[0008] References of interest in this regard include U.S. Patent Nos. 7,422,786; 9,126,269; 9,902,822; 10,273,029; and 11,441,023; and U.S. Patent Publication No. US 2022 / 0259417. Summary of the Invention

[0009] This disclosure provides a biaxially oriented film having at least a first outer layer, a second outer layer, and a core layer disposed between the first and second outer layers, the core layer comprising a first polymer composition. The first polymer composition comprises at least 50 wt% of a first metallocene linear low-density polyethylene (mLLDPE). The first mLLDPE comprises 80 wt% to 99 wt% of ethylene-derived units based on the weight of the first mLLDPE and 1 wt% to 20 wt% of units derived from one or more C3 to C4 derivatives. 20 The unit of α-olefin, and having:

[0010] i) From 0.900 g / cm 3 Up to 0.940 g / cm 3 Density within the range;

[0011] ii) Composition distribution width index (CDBI) less than or equal to 40%;

[0012] iii) Melt index (I2) in the range of 0.1 g / 10 min to 5.0 g / 10 min; and

[0013] iv) Broad orthogonal copolymer distribution.

[0014] The first outer layer comprises a second polymer composition, and the second outer layer comprises a third polymer composition. The second and third polymer compositions may be the same or different. The second and third polymer compositions each independently comprise:

[0015] a) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min.

[0016] b) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min.

[0017] c) High-density polyethylene (HDPE); or

[0018] d) Its combination.

[0019] In some embodiments, the first polymer composition further comprises:

[0020] a) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min.

[0021] b) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min.

[0022] c) High-density polyethylene (HDPE); or

[0023] d) Its combination.

[0024] In some embodiments, biaxial orientation includes a machine direction (MD) orientation stretch ratio ranging from 2.0:1 to 7.5:1 and a transverse direction (TD) orientation stretch ratio ranging from 6.5:1 to 11.5:1.

[0025] In some embodiments, the membrane has a shrinkage temperature in the range of 120°C to 170°C.

[0026] This disclosure further discloses a method for preparing shrink wrap, the method comprising arranging two or more adjacent items in one or more rows of two or more items to form a prepared bundle, wherein a Cartesian coordinate system is defined by a first horizontal axis parallel to one or more rows, a second horizontal axis perpendicular to one or more rows, and a vertical axis. The method further comprises wrapping the prepared bundle as disclosed herein in a multilayer film at a temperature ranging from 10°C to 40°C to form a wrapped bundle, wherein: i) the multilayer film forms a tube that encloses the prepared bundle of items; ii) the tube has a first opening at one end of the bundle and a second opening at the other end of the bundle; and iii) the tube is oriented such that the central axis of the tube is parallel to the first horizontal axis, the second horizontal axis, or the vertical axis. The method further comprises heating the wrapped bundle to a temperature sufficient to cause the tube to shrink to conform to the outermost surface of the prepared bundle to form a shrink-wrapped bundle.

[0027] In some embodiments of the method, the bundles are wrapped such that the machine orientation of the membrane is perpendicular to the central axis of the tube.

[0028] The features and technical advantages of the invention have been summarized quite extensively above in order to better understand the following detailed description of the invention. Additional features and advantages of the invention will be described below, which form the subject matter of the claims. Those skilled in the art will understand that the disclosed concepts and specific embodiments can be readily used as the basis for modifying methods for achieving the same objectives of the invention. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features considered characteristic of the invention (regarding its structure and method of manufacture), as well as further objects and advantages, will be better understood from the following description. Attached Figure Description

[0029] Figure 1 It is a superimposed graph used to compare the shrinkage force versus time of the present invention and comparative membranes according to the embodiments and / or techniques disclosed herein.

[0030] While the disclosed methods and systems are susceptible to various modifications and alternatives, the accompanying drawings illustrate specific embodiments described herein by way of example. However, it should be understood that the description of specific embodiments herein is not intended to limit the invention to the specific forms disclosed, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. Detailed Implementation

[0031] Illustrative embodiments of the claimed subject matter will now be disclosed. For clarity, some features of some actual implementations may not be described in this specification. It will be understood that in the development of any such actual implementation, many implementation-specific decisions must be made to achieve the developer's specific goals, such as complying with system-related and business-related constraints, which will vary from one implementation to another. Furthermore, it will be understood that such development efforts, even if complex and time-consuming, will be routine work for those of ordinary skill in the art who will benefit from this disclosure.

[0032] The words and phrases used herein should be understood and interpreted as having the same meaning as that understood by one of skill in the art. No particular definition of a term or phrase is intended to be implied by the consistent use of the term or phrase herein, i.e., a definition different from the common and conventional meaning understood by one of skill in the art. If a term or phrase is intended to have a particular meaning, i.e., a meaning different from the broadest meaning understood by one of skill in the art, such particular or clarifying definition will be clearly stated in the specification in a manner that provides for the particular or clarifying definition of the term or phrase.

[0033] For example, the following discussion contains a non-exhaustive list of definitions for several specific terms used in this disclosure (other terms may be defined or clarified elsewhere in this document). These definitions are intended to clarify the meaning of the terms as used herein. Terms are believed to be used in accordance with their ordinary meaning, but definitions are provided here for clarity.

[0034] definition

[0035] As used in this article, the “central axis” of a tube refers to the axis in a Cartesian coordinate system that is parallel to the wall of the tube and passes through the centroid or geometric center of the shape defined by the intersection of the tube and a plane perpendicular to the central axis of the tube.

[0036] As used herein, “free of” a component means that the composition is substantially free of the component or contains the component in an amount of less than about 0.01 wt% of the component by weight of the total composition.

[0037] As used herein, "HDPE" refers to polymers produced in the gas phase and / or slurry phase and having a strength of 0.940 g / cm³. 3 Up to 0.970 g / cm 3 ethylene homopolymers and ethylene copolymers within a certain density range.

[0038] As used in this article, “LCB-mLLDPE” refers to metallocene-catalyzed LLDPE with a melt index ratio (MIR) greater than or equal to 20.

[0039] As used herein, "LDPE" or "low-density polyethylene" refers to polyethylene produced in high-pressure free radical polymerization and having a density of 0.910 g / cm³. 3 Up to 0.940 g / cm 3 Ethylene homopolymers and / or ethylene copolymers within a certain density range.

[0040] As used herein, "LLDPE" or "linear low-density polyethylene" refers to polyethylene produced in suspension, solution, slurry, or gas-phase polymerization processes and having a density of 0.910 g / cm³. 3 Up to 0.940 g / cm 3 Ethylene copolymers within a certain density range. LLDPE can be produced in gas-phase reactors, high-pressure tubular reactors and / or slurry reactors and / or in solution reactors using conventional Ziegler-Natta catalysts, vanadium catalysts, metallocene catalysts, and / or other suitable catalysts for polymerizing ethylene and comonomers, and / or with any disclosed catalyst.

[0041] As used in this article, “narrow-CD mLLDPE” refers to metallocene-catalyzed LLDPE with a compositional distribution width index (CDBI) greater than or equal to 50%.

[0042] As used herein, “polyethylene” means ethylene homopolymer or copolymer containing at least 79 wt.% ethylene. The terms “polyethylene polymer,” “polyethylene,” “ethylene polymer,” “ethylene copolymer,” and “ethylene-based polymer” have the same meaning as polyethylene copolymer, unless otherwise specified (e.g., when referring to polyethylene homopolymer, this means a polymer formed from ethylene monomers that does not contain comonomer units, e.g., 100 wt% ethylene-derived units).

[0043] As used herein, “stretch ratio” refers to the ratio of the length of a stretch of membrane to the length of the membrane before stretching. For example, a membrane with a length of 10 cm stretched to a length of 40 cm in the machine direction (MD) will have an MD stretch ratio or MD orientation ratio of 4:1.

[0044] It should be noted that in this disclosure and particularly in the claims and / or paragraphs, terms such as “comprises,” “comprised,” “comprising,” etc., may have the meanings conferred upon them under U.S. patent law; for example, they may mean “includes,” “included,” “including,” etc.; and terms such as “consisting essentially of” and “consists essentially of” have the meanings conferred upon them under U.S. patent law, for example, they allow for elements not expressly listed, but do not include elements found in the prior art or that affect the essential or novel features of this disclosure.

[0045] Multilayer film

[0046] As disclosed herein, a multilayer film for finishing shrinkage applications comprises at least a first outer layer, a second outer layer, and a core layer disposed between the first and second outer layers. The multilayer film is biaxially oriented. The core layer comprises a first polymer composition containing at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, or at least 90 wt% of a first metallocene linear low-density polyethylene (mLLDPE) based on the weight of the first polymer composition.

[0047] In some embodiments, the first polymer composition further comprises: a) a narrow-CD mLLDPE having a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min.; b) a long-chain branched (LCB) mLLDPE having a CDBI greater than or equal to 60% and a melt index (I2) less than 1.2 dg / min.; c) high-density polyethylene (HDPE); or d) a combination thereof.

[0048] In some embodiments, narrow-CD mLLDPE is present in the first polymer composition in an amount of less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, or less than or equal to 10 wt% of the total weight of the first polymer composition.

[0049] In some embodiments, LCB mLLDPE is present in the first polymer composition in an amount of less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, or less than or equal to 10 wt% of the total weight of the first polymer composition.

[0050] In some embodiments, HDPE is present in the first polymer composition in an amount of less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, or less than or equal to 10 wt% of the total weight of the first polymer composition.

[0051] In some embodiments, based on the total weight of the first polymer composition, the first polymer composition comprises a first mLLDPE in an amount ranging from 50 wt% to 95 wt%, from 60 wt% to 90 wt%, from 70 wt% to 85 wt%, or from 75 wt% to 80 wt%, and an HDPE in an amount ranging from 5 wt% to 50 wt%, from 10 wt% to 40 wt%, from 15 wt% to 30 wt%, or from 20 wt% to 25 wt%.

[0052] The first mLLDPE is a narrow MWD BOCD-mLLDPE as defined herein, comprising 80 wt% to 99 wt% by weight of ethylene-derived units based on the first mLLDPE and 1 wt% to 20 wt% of derivatives derived from one or more C3 to C4 groups. 20 The unit of α-olefin, and having:

[0053] a) The first mLLDPE comprises 80 wt% to 99 wt% ethylene-derived units based on the first mLLDPE and 1 wt% to 20 wt% derivatives derived from one or more C3 to C4 groups. 20 The unit of α-olefin, and having:

[0054] i) From 0.900 g / cm 3 Up to 0.940 g / cm 3 Density within the range;

[0055] ii) Composition distribution width index (CDBI) less than or equal to 40%;

[0056] iii) Melt index (I2) in the range of 0.1 g / 10 min to 5.0 g / 10 min; and

[0057] iv) Broad orthogonal copolymer distribution.

[0058] The first outer layer comprises a second polymer composition, and the second outer layer comprises a third polymer composition, wherein the second and third polymer compositions are the same or different. The second and third polymer compositions each independently comprise:

[0059] i) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min.

[0060] ii) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min.

[0061] iii) High-density polyethylene (HDPE); or

[0062] iv) Its combination.

[0063] In some embodiments, narrow-CD mLLDPE is present in the first outer layer and / or the second outer layer in an amount greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt% of the total weight of the relevant layers.

[0064] In some embodiments, LCB mLLDPE is present in the first outer layer and / or the second outer layer in an amount greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt% of the total weight of the relevant layers.

[0065] In some embodiments, HDPE is present in the first outer layer and / or the second outer layer in an amount greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt% of the total weight of the relevant layers.

[0066] In some embodiments, based on the total weight of the first polymer composition, the first polymer composition comprises a first mLLDPE in an amount ranging from 50 wt% to 95 wt%, from 60 wt% to 90 wt%, from 70 wt% to 85 wt%, or from 75 wt% to 80 wt%, and an HDPE in an amount ranging from 5 wt% to 50 wt%, from 10 wt% to 40 wt%, from 15 wt% to 30 wt%, or from 20 wt% to 25 wt%.

[0067] In some embodiments, based on the polymer portion of the associated layer (excluding additives), the first outer layer and / or the second outer layer comprises 100 wt% narrow-CD mLLDPE.

[0068] In some embodiments, the multilayer film does not contain low-density polyethylene (LDPE). Adding LDPE to conventional CS films helps improve TD shrinkage, believed to be due to the long-chain branching present in LDPE. However, the TD shrinkage of conventional CS films containing LDPE and produced in a blown film process is typically limited to about 20%-25%. In contrast, some embodiments of the BOPE CS films disclosed herein have TD shrinkage greater than or equal to 50%. Furthermore, the addition of LDPE negatively impacts certain mechanical properties, such as, but not limited to, dart impact strength. The BOPE CS films disclosed herein, containing less or no LDPE, offer better dart impact strength compared to conventional CS films. As used herein, LDPE, unlike LLDPE (linear low-density polyethylene), refers to low-density polyethylene with a considerable degree of long-chain branching (LCB) and is known in the art to be produced by free radical polymerization of, for example, ethylene monomers, typically in autoclaves or tubular reactors. Unlike catalytically polymerized LLDPE, which is polymerized from ethylene monomers and α-olefin comonomers, LLDPE has a considerable degree of short-chain branching (SCB) (typically attributed to the incorporation of said comonomers into the polymer chain) and has little or no LCB.

[0069] First mLLDPE

[0070] The first mLLDPE is narrow MWD BOCD-mLLDPE. In some embodiments, narrow MWD BOCD-mLLDPE is produced using substituted bulky ligand hafnium transition metal-metallocene catalyst compounds and their substituted forms, as disclosed in U.S. Patent Nos. 9,181,362, 6,242,545, 7,078,467, RE 40751 11,214,659, and 9,695,290; and one or more of U.S. Publications 2015 / 240000, 2015 / 259445, and 2015 / 284523, the contents of which are incorporated herein by reference in their entirety. This type 3 catalyst produces polyethylene grades having a narrow MWD and a wide orthogonal comonomer distribution (BOCD), which may be referred to herein as narrow MWD BOCD-mLLDPE.

[0071] As mentioned above, suitable mLLDPEs can have a narrow molecular weight distribution (MWD) and a wide orthogonal compositional distribution (BOCD). Molecular weight distribution (MWD) or (M w / M n The range can be from about 2.0 to about 4.5, from about 2.2 to about 4.5, from about 3.0 to about 4.0, or from about 2.5 to about 4.0. Weight-average molecular weight (M wThe range can be from about 15,000 to about 400,000 g / mol, from about 20,000 to about 250,000 g / mol, from about 20,000 to about 200,000 g / mol, from about 25,000 to about 150,000 g / mol, from about 150,000 to about 400,000 g / mol, from about 200,000 to about 400,000 g / mol, or from about 250,000 to about 350,000 g / mol. z-average molecular weight (M z ) and weight-average molecular weight (M w The ratio can be greater than about 1.5, or greater than about 1.7, or greater than about 2.0. In some embodiments, this ratio is from about 1.7 to about 3.5, from about 2.0 to about 3.0, or from about 2.2 to about 3.0.

[0072] The term "orthogonal comonomer distribution" is used herein to mean that, within the molecular weight range of the polymer, the comonomer content of various polymer fractions is not substantially uniform, and that higher molecular weight fractions typically have higher comonomer content than lower molecular weight fractions. The term "substantially homogeneous comonomer distribution" is used herein to mean that, within the molecular weight range of ethylene-based polymers, the variation in comonomer content of polymer fractions is < 10.0 wt%. In some embodiments, a substantially homogeneous comonomer distribution may mean < 8.0 wt%, < 5.0 wt%, or < 2.0 wt%. Both substantially homogeneous and orthogonal comonomer distributions can be determined using fractionation techniques such as gel permeation chromatography-differential viscometry (GPC-DV), temperature elution fractionation-differential viscometry (TREF-DV), or cross-fractionation techniques.

[0073] The width of the compositional distribution of a polymer can be expressed by T. 75 -T 25Characterization was performed using an analytical-sized TREF instrument (Polymerchar, Spain), with a column having the following dimensions: inner diameter (ID) 7.8 mm, outer diameter (OD) 9.53 mm, and column length 150 mm. The column could be packed with steel balls. 0.5 mL of a polymer solution containing 2 g BHT / 4 L o-dichlorobenzene (ODCB) at a concentration of 4 mg / mL was loaded into the column and cooled from 140°C to -15°C at a constant cooling rate of 1.0°C / min. Subsequently, ODCB was pumped through the column at a flow rate of 1.0 mL / min, and the column temperature was increased at a constant heating rate of 2°C / min to elute the polymer. The polymer concentration in the eluent was then detected by measuring the absorbance at a wavenumber of 2941 cm⁻¹ using an infrared detector. The concentration of the ethylene-α-olefin copolymer in the eluent was calculated from the absorbance and plotted as a function of temperature. As used herein, T 75 -T 25 The value refers to T. 25 The temperature at which 25% of the eluted polymer is obtained, expressed in degrees Celsius, and T 75 The temperature at which 75% of the eluted polymer was obtained, expressed in degrees Celsius (by TREF analysis).

[0074] "Broad orthogonal comonomer distribution" or BOCD refers to a significantly higher degree of short-chain branching in the copolymer compared to the shorter molecular weight polymer chains. Suitable narrow-MWD mLLDPEs with BOCD can have T values ​​ranging from 5 to 10. 75 -T 25 Values, alternatively, from 5.5 to 10 for T 75 -T 25 Values, and alternatively, T values ​​from 5.5 to 8. 75 -T 25 Values, alternatively, T from 6 to 10 75 -T 25 Values, and alternatively, T from 6 to 8. 75 -T 25 Value, where T 25 The temperature at which 25% of the eluted polymer is obtained, expressed in degrees Celsius, and T 75 It is the temperature at which 75% of the eluted polymer is obtained, measured in degrees Celsius (by temperature elution fractionation (TREF)).

[0075] These mLLDPEs may have a CDBI of less than about 40%, or less than about 35%, or less than about 30%, or less than about 25%. The CDBI range may also be from as low as about 15%, 20%, or 25% to as high as about 30%, 35%, or 40%, and it should be further noted that the compositional distribution results in the higher molecular weight chains of these mLLDPEs having a larger wt% comonomer content than the lower molecular weight chains of the mLLDPEs. CDBI is defined as the weight percentage of copolymer molecules having a comonomer content within + / - 50% of the intermediate comonomer mol% value, as described on pages 18-19 of WO 1993 / 003093 in conjunction with Figure 17 therein. This means that for a copolymer with an intermediate comonomer mol% value (Cmed) of 8 mol% comonomer on the polymer chain, the CDBI is the wt% of the copolymer chain having a comonomer mol% content between (0.5 × Cmed) and (1.5 × Cmed). In this example, CDBI is the wt% of a copolymer chain having a comonomer content between (0.5 × 8) and (1.5 × 8) mol%, or between 4 mol% and 12 mol%. WO 1993 / 003093 also describes a method for determining the weight fraction versus composition curve (i.e., composition distribution curve) of a polymer using chromatography and C13 NMR, and for determining the intermediate comonomer composition Cmed by referring to Figures 16 and 17 of that publication. See also Wild, et al., J. Poly. Sci., Poly. Phys. Ed., Vol. 20, p. 441 (1982) and U.S. Patent No. 5,008,204, which is also incorporated herein by reference. Thus, a higher CDBI value indicates a narrow composition distribution (meaning that the comonomers are distributed relatively uniformly across polymer chains of different molecular weights).

[0076] These mLLDPEs can have 70.0 wt% to 100.0 wt% of ethylene-derived units. Based on the wt% of ethylene-derived polymer units, the lower limit of the ethylene content range can be 70.0 wt%, 75.0 wt%, 80.0 wt%, 85.0 wt%, 90.0 wt%, 92.0 wt%, 94.0 wt%, 95.0 wt%, 96.0 wt%, 97.0 wt%, 98.0 wt%, or 99.0 wt%. Based on the ethylene-derived polymer units, these mLLDPEs can also have an upper limit of ethylene of 80.0 wt%, 85.0 wt%, 90.0 wt%, 92.0 wt%, 94.0 wt%, 95.0 wt%, 96.0 wt%, 97.0 wt%, 98.0 wt%, 99.0 wt%, 99.5 wt%, or 100.0 wt%. Less than 30.0 wt% of polymer units can be derived from C3-C. 20 Olefins, preferably α-olefins, such as hexene or octene. Based on C3-C derivatives. 20 Polymer units of olefins, C3-C 20 The lower limit of the olefin content range can be 25.0 wt%, 20.0 wt%, 15.0 wt%, 10.0 wt%, 8.0 wt%, 6.0 wt%, 5.0 wt%, 4.0 wt%, 3.0 wt%, 2.0 wt%, 1.0 wt%, or 0.5 wt%. This is based on olefins derived from C3 to C4. 20 Polymer units of olefins, C3-C 20 The upper limit of the olefin content range can be 20.0 wt%, 15.0 wt%, 10.0 wt%, 8.0 wt%, 6.0 wt%, 5.0 wt%, 4.0 wt%, 3.0 wt%, 2.0 wt%, or 1.0 wt%.

[0077] These mLLDPEs can have a concentration ranging from approximately 0.900 g / cm³. 3 Approximately 0.940 g / cm³ 3 From approximately 0.910 g / cm 3 Approximately 0.935 g / cm³ 3 From approximately 0.900 g / cm 3 Approximately 0.930 g / cm³ 3 From approximately 0.900 g / cm 3 To approximately 0.925 g / cm 3 From approximately 0.900 g / cm 3 Approximately 0.923 g / cm³ 3 From approximately 0.900 g / cm 3To approximately 0.920 g / cm 3 From approximately 0.912 g / cm 3 Approximately 0.919 g / cm³ 3 From approximately 0.912 g / cm 3 Approximately 0.918 g / cm³ 3 From approximately 0.914 g / cm 3 Approximately 0.918 g / cm³ 3 Or from approximately 0.915 g / cm 3 Approximately 0.918 g / cm³ 3 The density is based on ASTM D-4703 and ASTM D-1505 / ISO 1183.

[0078] These mLLDPEs may have concentrations of approximately 0.1 g / 10 min to approximately 5.0 g / 10 min, approximately 0.1 g / 10 min to approximately 3.0 g / 10 min, approximately 0.1 g / 10 min to approximately 2.0 g / 10 min, approximately 0.1 g / 10 min to approximately 1.2 g / 10 min, approximately 0.2 g / 10 min to approximately 1.5 g / 10 min, approximately 0.2 g / 10 min to approximately 1.1 g / 10 min, approximately 0.3 g / 10 min to approximately 1.0 g / 10 min, approximately 0.4 g / 10 min to approximately 1.0 g / 10 min, approximately 0.5 g / 10 min to approximately 1.0 g / 10 min, approximately 0.6 g / 10 min to approximately 1.0 g / 10 min, approximately 0.7 g / 10 min to approximately 1.0 g / 10 min, or approximately 0.75 g / 10 min to approximately 0.95 g / 10 min, as per ASTM standards. The melt index (MI) or (I) measured by D-1238-E (190°C / 2.16 kg) 2.16 ).

[0079] These mLLDPEs can have melt index ratios (MIRs) ranging from about 20 to about 38, from about 22 to about 35, from about 20 to about 32, from about 25 to about 32, or from about 28 to about 31. 21.6 / I 2.16 (as defined below).

[0080] In the comonomer distribution analysis, these mLLDPEs may also have at least a first peak and a second peak, wherein the first peak has a log(M) value between 4.0 and 5.4, or between 4.3 and 5.0, or between 4.5 and 4.7. wThe maximum value at ) values; and TREF elution temperatures from 70.0°C to 100.0°C, or from 80.0°C to 95.0°C, or from 85.0°C to 90.0°C. The second peak in the comonomer distribution analysis has log(M) values ​​in the ranges of 5.0 to 6.0, 5.3 to 5.7, or 5.4 to 5.6. w The maximum value under the specified value; and the TREF elution temperature of 40.0°C to 60.0°C, 45.0°C to 60.0°C, or 48.0°C to 54.0°C.

[0081] In any of the above embodiments, a suitable mLLDPE may have a narrow MWD and a wide orthogonal compositional distribution, and possess one or more of the following properties: a melt index (MI) from about 0.1 g / 10 min to about 5.0 g / 10 min (190°C / 2.16 kg); a melt index ratio (MIR) from about 25 to about 32; and an MnO2 from about 20,000 to about 200,000 g / mol. w M from about 2.0 to about 4.5 w / M n ; and from approximately 0.900 g / cm 3 Approximately 0.940 g / cm³ 3 The density. In the recycled resin compositions disclosed herein, these narrow MWD BOCD-mLLDPEs may be referred to as “second mLLDPEs”.

[0082] Commercially available examples of this type of second mLLDPE with the aforementioned unique combination of properties include Exceed XP™ resin from ExxonMobil Chemical Company.

[0083] Narrow-CD mLLDPE

[0084] Narrow-CD mLLDPE can be produced using unbridged bis-cyclopentadienyl group 4 catalysts and their substituted forms. Such catalysts produce polyethylene grades with a narrow compositional distribution (i.e., uniform distribution of comonomers moving between polymer chains) and are referred to herein as narrow-CD mLLDPE.

[0085] For example, narrow-CD mLLDPEs may include metallocene-catalyzed LLDPEs (mLLDPEs) with a flat compositional distribution, which are copolymers of 80% to 99.9 wt% ethylene-derived units, with the remaining units derived from one or more C3 to C4 groups. 12α-olefin comonomers (and particularly one or more of butene, hexene, and octene; preferably one of these; and more preferably hexene). wt% is based on the total mass of ethylene-derived units plus comonomer-derived units in the polyethylene. Such polyethylene is referred to as having a “flat composition distribution”, which is based on the comonomers being incorporated into the shorter and longer molecular weight chains of the polymer in relatively equal amounts (by wt%). These can also be referred to as “narrow-CD” or “narrow-composition-distribution” polyethylene; or, equivalently, high-CDBI mLLDPE. Composition distribution refers to the distribution of comonomers among polymer chains of different lengths (different molecular weights), and CDBI refers to the composition distribution width index, as defined above.

[0086] Narrow-CD polyethylene may have a CDBI of at least 50%, more preferably at least 60%, such as in the range of 50% to 90% or 60% to 80%.

[0087] Narrow-CD polyethylene may more particularly have ethylene-derived content in any range from low to high of 88, 90, 90, 99, 90, 99, 99, 99, 99, 99, 99, 99, 99, 99, 99, 95 wt%, from any of the aforementioned low to any of the aforementioned high, provided that the high end is greater than the low end (e.g., 85 to 95 wt%, such as 86 to 92 wt% of ethylene-derived units; or 94 to 99 wt% of ethane-derived units). The balance is from C3 to C4. 12 It is composed of α-olefin comonomer-derived units (e.g., hexene).

[0088] Narrow-CD mLLDPE can provide a lower softening point with respect to the formation process, and further provides excellent sealing, optical, and mechanical properties for membranes made therefrom. Narrow-CD mLLDPE preferably also has one or more, preferably all of, the following further properties:

[0089] • The peak melting temperature in the range of 105°C to 120°C, preferably 110°C, or 111°C to 115°C or 116°C. The peak melting temperature, also referred to herein simply as the “melting point,” is determined using a differential scanning calorimeter (DSC). DSC measurements can be performed using a TA DSC8000 instrument under a N2 atmosphere at a heating / cooling rate of 10 K / min. The sample is heated from -50°C to 300°C, held for 5 minutes to eliminate the previous thermal history, then cooled to -50°C, and then reheated to 300°C.

[0090] • Vicat softening temperature (ASTM D1525) within the softening point range of 70°C to 130°C, preferably 90°C to 110°C, such as from any of the following low 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 96°C, 97°C, 98°C, 99°C or 100°C to any of the following high 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C (considering the range from any of the above low to any of the above high, provided that the high is greater than the low, for example 90°C to 110°C or 97°C to 103°C).

[0091] • Melt index (MI, also known as I2 or I) in the range of 0.1 to 5.0 g / 10 min (ASTM D1238, 190°C, 2.16 kg load) 2.16 According to the 2.16 kg load used in the test, from any one of the low 0.1, 0.2, 0.3, 0.4, 0.5, 0.7 or 0.8 g / 10 min to any one of the high 1.0, 1.1, 1.2, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 or 5.0 g / 10 min; the range from any of the above low end to any of the above high end was also considered.

[0092] • A long-chain branching index (LCB index, also referred to as g′ in this paper) greater than 0.95, preferably greater than or equal to 0.96 or 0.97. vis Or g′ index).

[0093] Narrow-CD mLLDPE may also have one or more of the following, preferably all of them:

[0094] • Weight-average molecular weight (Mi) in the range of 45,000 to 120,000 g / mol, such as from 50,000 to 115,000 g / mol or 60,000 to 110,000 g / mol. w (Also considered is a range from any of the aforementioned low-end to any of the aforementioned high-end, e.g., 45,000 to 110,000 g / mol).

[0095] • Number-average molecular weight (Mn) in the range of 20,000 to 55,000 g / mol n), such as in the range of 25,000; 30,000; 35,000; or 40,000 to high 30,000; 35,000; 40,000; 45,000; 50,000; or 55,000 g / mol, and also considering the range from any of the lower end to any of the higher end (provided that the higher end is greater than the lower end), for example from 35,000 to 55,000 g / mol;

[0096] • Molecular weight distribution (MWD) in the range of 1.5 or 2.0 to 3.5 or 4; and

[0097] • In the range of 0.905 to 0.940 g / cm 3 Density within the range (ASTM D1505), such as from the lower end of 0.905, 0.910, 0.911, 0.912, or 0.915 g / cm³. 3 Any of the following maximum values: 0.913, 0.914, 0.915, 0.920, 0.925, 0.926, 0.928, 0.930, 0.935, or 0.940 g / cm³ 3 Within any of the ranges mentioned above, considering the range from any of the aforementioned low-end to any of the aforementioned high-end (provided that the high-end is greater than the low-end), for example, 0.910 to 0.915 g / cm³. 3 .

[0098] Examples of suitable polyethylenes for narrow-CD mLLDPE include Exceed™ high-performance polyethylene available from ExxonMobil Chemicals, and other commercially available mLLDPEs such as Evolue™ SP1510 available from Prime Polymer Co., Ltd.

[0099] LCB-mLLDPE

[0100] LCB-mLLDPE can be produced using bridged bis-cyclopentadienyl group 4 and its substituted forms, as disclosed in one or more of U.S. Patent Nos. 6,255,426 and 6,476,171, the contents of which are incorporated herein by reference in their entirety. This type 2 catalyst produces polyethylene grades with some long-chain branching (compared to the highly linear structure of most mLLDPEs) and is referred to herein as “LCB-mLLDPE”.

[0101] Compared to other linear low-density polyethylenes, and especially to other metallocene LLDPEs, long-chain branched mLLDPEs (LCB mLLDPEs) are considered to have long-chain branching; however, their total long-chain branching will still be less than that of LDPEs with a very high degree of long-chain branching. This small amount of LCB can be demonstrated, for example, by a high melt index ratio (MIR) and / or specific rheological properties, as shown by data obtained via small-angle oscillating shear (SAOS) experiments (e.g., η). 0.01 / η 100 The ratio of the complex viscosity recorded at shear rates of 0.01 and 100 rad / s, respectively.

[0102] Another useful parameter that explains the presence of some LCBs can be found in the melt index ratio. The melt index ratio (MIR) is the ratio of the high load melt index (HLMI, ASTM D1238 at 190°C, 21.6 kg) to the melt index (MI2, ASTM D1238 at 190°C, 2.16 kg).

[0103] Therefore, the LCB-mLLDPE that can be used in the compositions of the present invention may have one or more of the following characteristics (this can be a useful indicator of medium LCB):

[0104] • MIR in any range from low 20, 25, 26, 27, 28, 29, 30 or 31 to high 40, 35, 34, 33, 32, 31 or 30, this document considers ranges from any of the above low to any of the above high (e.g. 27 to 33, as 28 to 32, or 29 to 31).

[0105] • Composite shear viscosity (η*) at 0.01 rad / sec and 190°C in the range of 5,000 to 12,000 Pa·s; or from any of the following: low 5,000; 6,000; 7,000; 8,000; 9,000; 10,000; or 11,000 Pa·s to high 12,000; 11,000; 10,000; 9,000; 8,000; 7,000; or 6,000 Pa·s, considering a range from any low end to any high end (e.g., 6,000 to 8,000 Pa·s).

[0106] • Composite shear viscosity (η*) at 100 rad / sec and 190°C in the range of 900 to 2000 Pa·s; such as from any of the lower end of 900; 1,000; 1,100; or 1,200 Pa·s to the upper end of 1,200; 1,300; 1,400; 1,500; or 2,000 Pa·s, and also considering the range from any of the above lower to any of the above higher (e.g., 1,100 to 1,300 Pa·s).

[0107] • Less than 15, or a shear thinning ratio (η* at 0.01 / 100) in the range of 3 to 15, or 4 to 12, or 5 to 10, or 5.5 to 8.

[0108] • The inflection point of the phase angle versus complex modulus (Pa) plot of LCB-mLLDPE.

[0109] Finally, another indicator of LCB can be seen in the LCB index (g' or alternatively g'vis), which can be less than 1 for LCB-mLLDPE, such as in the range of 0.9 to 0.99 or 0.94 to 0.98, although still significantly higher than g' for highly LCB polyethylene (such as LDPE prepared using free radical polymerization).

[0110] Suitable mLLDPEs having the aforementioned moderate LCB are preferably copolymers of 80, 85, 88, 90, 92, 93, 94 or 95 to 6, 97, 98 or 99 wt% ethylene-derived units, the remainder derived from one or more C3 to C4 derivatives. 12 α-olefins (and particularly one or more of butene, hexene, and octene; preferably one of these; and more preferably hexene). wt% is based on the total mass of ethylene-derived units plus comonomer-derived units in polyethylene.

[0111] Suitable LCB mLLDPEs can also have a composition distribution width index (CDBI) of 60% or more, preferably 70% or more, as considered in the range from any of the lower 60%, 70%, or 75% to the higher 80%, 85%, 90%, 95%, or 99%, taking into account any of the aforementioned lower to higher ranges. The composition distribution width index (CDBI) is defined as the weight percentage of copolymer molecules containing comonomers within 50% of the intermediate total molar comonomer content. The CDBI of a copolymer can be readily determined using well-known techniques for separating individual fractions of a copolymer sample. One such technique is thermal rinsing fractionation (TREF), as described in Wild, et al., J. Poly. Sci., Poly. Phys. Ed., Vol. 20, p. 441 (1982) and U.S. Patent No. 5,008,204, which is incorporated herein by reference in its entirety.

[0112] Suitable LCB mLLDPEs can also have MWD (Mw / Mn) in the range of 2.5 to 5.5, such as in the range of 3 or 3.5 to 4.5 or 5.

[0113] Suitable LCB mLLDPE may further have a melt index (I2, determined according to ASTM D1238 at 190°C and 2.16 kg load) in the range of 0.1 to 3.0 g / 10 min, or the range may be from any one of the low 0.1, 0.15, 0.2 or 0.22 to any one of the high 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0, 1.5, 2.0, 2.2, 2.5, 2.7 or 3.0 g / 10 min; a range from any of the aforementioned low end to any of the aforementioned high end (provided that the high end is greater than the low end), for example from 0.1 to 2.5 g / 10 min; 0.15 to 1.0 g / 10 min; or 0.2 to 0.50 g / 10 min.

[0114] High load melt index (HLMI, or I) 21 According to ASTM D1238 (measured at 190°C and 21.6 kg load), the value can be in the range of 10 to 75 g / 10 min, such as from 12 to 70 g / 10 min.

[0115] The density of LCB-mLLDPE can range from 0.900 to 0.940 g / cm³. 3 Within the range, such as from low 0.905, 0.910, 0.920 or 0.925 g / cm³ 3Any one of them up to 0.930, 0.932, 0.933, 0.934, 0.935 or 0.940 g / cm³ 3 Any of the above, this paper considers a range from any of the aforementioned low to any of the aforementioned high (e.g., 0.910 to 0.935 g / cm³). 3 ).

[0116] In the compositions described herein, these LCB-mLLDPEs may be referred to as “first mLLDPEs.” Specific examples of such first mLLDPEs with the aforementioned unique combination of properties include certain Enable™ and Exceed™ XP brand polyethylenes from ExxonMobil Chemicals, such as Exceed™ XP 6026, Enable™ 2010, Enable™ 2703, Enable™ 3505, Enable™ 4002, and Enable™ 4009 high-performance polyethylenes. Other commercial examples include DowInnate™ ST70, Dow Agility™ 2001, Dow Elite™ 5940, Dowlex™ 2038.68G, Dow Elite™ AT 6401, Dow Attane™ 4701G, Marlex™ TR130, and Nova Surpass™ 117 / 116.

[0117] additive

[0118] The polymer compositions containing COC and polyethylene described herein can be used in combination with the following additives and other components.

[0119] - First antioxidant

[0120] The first antioxidant includes one or more antioxidants. These include, but are not limited to, hindered phenols, such as octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate (CAS002082-79-3), which is commercially available as Irganox™ 1076, and pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (CAS 6683-19-8), which is commercially available as Irganox™ 1010; and combinations thereof.

[0121] They can be combined with one or more polymers, ranging from 100 to 4000 parts by weight of a first antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 250 to 3000 parts by weight of a first antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 500 to 2500 parts by weight of a first antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 750 to 2500 parts by weight of a first antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 750 to 2000 parts by weight of a first antioxidant based on one million parts of the polymer or polymer composition; and alternatively, from 1000 to 2000 parts by weight of a first antioxidant based on one million parts of the polymer or polymer composition.

[0122] -Second antioxidant

[0123] The second antioxidant comprises one or more antioxidants. These include, but are not limited to, liquid phosphites, such as C2-C7, preferably C2-C4, and mixed structures of alkylaryl phosphites. Non-limiting examples include mono-pentylphenyl phosphite, di-pentylphenyl phosphite, dimethylpropyl phosphite, 2-methylbutyl phosphite, and combinations thereof. In several embodiments of the invention, the second antioxidant may also be represented by a phosphate ester of the formula [4-(2-methylbutane-2-yl)phenyl]x[2,4-bis(2-methylbutane-2-yl)phenyl]3-x, where x = 0, 1, 2, 3, or a combination thereof.

[0124] Such antioxidants and their use with polyolefin polymers have been described in U.S. Patent Applications Nos. 2005 / 0113494; 2007 / 0021537; 2009 / 0326112; 2013 / 0190434; 2013 / 225738; 2014 / 0045981 and U.S. Patents Nos. 5,254,709; 6,444,836; 7,888,414; 7,947,769; 8,008,383; 8,048,946; 8,188,170; and 8,258,214. Examples of commercially available liquid phosphites are marketed under the trade name WESTON™ 705 (Addivant, Danbury, Conn.).

[0125] The second antioxidant may be combined with one or more polymers, ranging from 100 to 4000 parts by weight of the second antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 250 to 3000 parts by weight of the second antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 300 to 2000 parts by weight of the second antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 400 to 1450 parts by weight of the second antioxidant based on one million parts of the polymer or polymer composition; alternatively, from 425 to 1650 parts by weight of the second antioxidant based on one million parts of the polymer or polymer composition; and alternatively, from 1 to 450 parts by weight of the second antioxidant based on one million parts of the polymer or polymer composition.

[0126] Polymers and / or compositions containing the first and / or second antioxidants described above may be used in combination with neutralizers, additional additives and other components.

[0127] - Neutralizing agent

[0128] One or more neutralizing agents (also known as catalyst deactivators) include, but are not limited to, calcium stearate, zinc stearate, calcium oxide, synthetic hydrotalcite (such as DHT4A), and combinations thereof.

[0129] - Additional additives and other components

[0130] Additional additives and other components include, but are not limited to, fillers (especially silica, glass fiber, talc, etc.), colorants or dyes, pigments, colorants, whitening agents, cavitation agents, antislip agents, antiblocking agents (such as Polybatch™ F15 antiblocking agent, commercially available from A. Schulman, Ohio), lubricants, plasticizers, processing aids, antistatic agents, antifogging agents, nucleating agents, stabilizers, release agents, and other antioxidants (e.g., hindered amines and phosphates / esters). Nucleating agents include, for example, sodium benzoate and talc. Slip agents include, for example, oleamide and erucamide.

[0131] In one embodiment, one or more layers or films may comprise one or more of fillers, pigments, lubricating additives / reagents, colorants or dyes, colorants, whitening agents, cavitation agents, lubricants, plasticizers, processing aids, antifogging agents, nucleating agents, stabilizers, release agents, or antioxidants.

[0132] In some embodiments, the first outer layer and / or the second outer layer comprises an anti-blocking agent (such as Polybatch™ F15) in an amount based on the weight of the relevant layer ranging from 0.1, 0.2, 0.3, 0.4, or 0.5 wt% to 2.0, 2.5, 3.0, 3.5, or 4.0 wt%.

[0133] Membranes and their manufacturing methods

[0134] The polymer compositions comprising mLLDPE and HDPE as described above can be formed as monolayer or multilayer films. As used herein, a “film” or “multilayer film” is a material having an average thickness of less than or equal to 250 µm and may contain one or more substances such as polymers, fillers, additives, oils, etc. In some embodiments, the film or multilayer film is continuous in its measurable width and length, is typically flexible, and preferably has a thickness in the range of 50, 10, 20, 40, or 45 µm to 250, 100, 150, 200, or 250 µm.

[0135] In some embodiments of a multilayer film comprising at least a first outer layer, a second outer layer, and a core layer disposed between the first outer layer and the second outer layer, the thickness of the core layer is in the range of 25%, 35%, 45%, or 55% to 75%, 80%, 85%, or 90% of the total thickness of the multilayer film.

[0136] In some embodiments, the core layer of the membrane is sandwiched between two polyethylene surface layers. In some embodiments, at least one core layer is sandwiched between two to six layers comprising LLDPE. Some configurations include surface / core / surface layers and surface / subsurface / core / subsurface / core layer arrangements. In some embodiments, each surface layer independently comprises at least 50 wt% linear low-density polyethylene by weight of each surface layer. In any embodiment, the multilayer membrane further comprises a subsurface layer sandwiched between the core layer (one or more) and each surface layer. In some embodiments, each subsurface layer independently comprises at least 50 wt% linear low-density polyethylene by weight of each surface layer. In embodiments in which two or more core layers are present, they are preferably adjacent to each other, but an LLDPE layer may be present between them.

[0137] In any of the embodiments described herein, other materials may be incorporated into the membrane layer, or the membrane layer itself may contain or consist substantially of another material. Suitable materials include ethylene vinyl acetate, ethylene-based ionomers, polypropylene, propylene-based elastomers, ethylene-based plasmons, ethylene-propylene rubber, styrene-based block copolymers, styrene-based polymers, cellulose polymers, and combinations thereof.

[0138] In some embodiments, the films of the present invention are subjected to a biaxial orientation process after quenching. As is well known in the art, orientation can be achieved by reheating the extruded, quenched, and unoriented polymer films in an oven or heated zone (where the temperature of the polymer material is raised above its glass transition temperature). The material is then stretched in at least one direction to orient or align the polymer chains within the film. The film is then annealed and subsequently cooled, allowing crystals to reform, thereby maintaining the stretch and orientation.

[0139] Orientation in the extrusion direction is called machine orientation (MD). Orientation perpendicular to the extrusion direction is called transverse orientation (TD). Depending on the desired film characteristics, sequential or simultaneous orientation processes can be used. Sequential orientation can be achieved by stretching or pulling the film first on the MD and then on the TD. Simultaneous orientation processes refer to stretching the film in both the machine and transverse directions in a single step using a series of motors instead of clamps, such as the LISIM® process. Tensor-stretching orientation processes can also be used for biaxial orientation of the films of this invention. In some embodiments of this invention, a dual-bubble orientation process can be used.

[0140] In some embodiments, the machine orientation stretch ratio of the membrane disclosed herein is greater than or equal to 2.0:1, greater than or equal to 2.5:1, greater than or equal to 3.0:1, or greater than or equal to 3.5:1. In some embodiments, the machine orientation stretch ratio of the membrane disclosed herein is less than or equal to 7.5:1, less than or equal to 7.0:1, less than or equal to 6.5:1, or greater than or equal to 6.0:1.

[0141] In some embodiments, the transverse orientation ratio of the membrane disclosed herein is greater than or equal to 6.5:1, greater than or equal to 7.0:1, greater than or equal to 7.5:1, or greater than or equal to 8.0:1. In some embodiments, the transverse orientation ratio of the membrane disclosed herein is less than or equal to 11.5:1, less than or equal to 11.0:1, less than or equal to 10.5:1, or greater than or equal to 10.0:1.

[0142] The biaxial orientation ratio is the product of the machine orientation ratio and the transverse orientation ratio of the film. In some embodiments, after a post-quenching biaxial orientation process, the film has a biaxial orientation ratio ranging from about 20:1 to about 60:1.

[0143] In some embodiments, the biaxially oriented film disclosed herein has a machine-oriented (MD) contractile force in the range of 700 mN to 1,400 mN, 750 mN to 1,350 mN, 800 mN to 1,300 mN, or 850 mN to 1,250 mN.

[0144] In some embodiments, the biaxially oriented film disclosed herein has a normalized machine orientation (MD) contractile force in the range of 23.3 mN / µm to 46.7 mN / µm, 25.0 mN / µm to 45.0 mN / µm, 26.7 mN / µm to 43.3 mN / µm, or 28.3 mN / µm to 41.7 mN / µm.

[0145] In some embodiments, the biaxially oriented film disclosed herein has a transverse (TD) contractile force in the range of 700 mN to 1,400 mN, 750 mN to 1,350 mN, 800 mN to 1,300 mN, or 850 mN to 1,250 mN.

[0146] In some embodiments, the biaxially oriented film disclosed herein has a normalized transverse (TD) contractile force in the range of 23.3 mN / µm to 46.7 mN / µm, 25.0 mN / µm to 45.0 mN / µm, 26.7 mN / µm to 43.3 mN / µm, or 28.3 mN / µm to 41.7 mN / µm.

[0147] In some embodiments, the biaxially oriented film disclosed herein has a shrinkage temperature in the range of 120°C to 170°C, 130°C to 165°C, 140°C to 160°C, or 145°C to 155°C.

[0148] Shrink wrapping method

[0149] In some embodiments, a method for organizing shrink wrapping includes arranging two or more adjacent items in one or more rows of two or more items to form an organized bundle. The organized bundle defines a Cartesian coordinate system having a first horizontal axis parallel to one or more rows, a second horizontal axis perpendicular to one or more rows, and a vertical axis. The method further includes wrapping the organized bundle as described herein in a multilayer film at a temperature ranging from 10°C to 40°C to form a wrapped bundle, wherein: i) the multilayer film forms a tube that encloses the organized bundle of items; ii) the tube has a first opening at one end of the bundle and a second opening at the other end of the bundle; and iii) the tube is oriented such that the central axis of the tube is parallel to the first horizontal axis, the second horizontal axis, or the vertical axis. The method further includes heating the wrapped bundle to a temperature sufficient to cause the tube to shrink to conform to the outermost surface of the organized bundle to form a shrink-wrapped bundle.

[0150] In some embodiments, the first opening and the second opening are each reduced to substantially circular openings, having a maximum diameter smaller than the minimum size of the shape defined by the outer periphery of the neatly arranged bundle projected onto a plane perpendicular to the central axis.

[0151] In some embodiments, the temperature sufficient to cause the tube to shrink is in the range of 120°C to 170°C, 130°C to 165°C, 140°C to 160°C, or 145°C to 155°C.

[0152] In some embodiments, the bundled wrapping is arranged such that the machine orientation of the membrane is perpendicular to the central axis of the tube.

[0153] Some embodiments

[0154] In some embodiments, the multilayer film includes at least a first outer layer, a second outer layer, and a core layer disposed between the first and second outer layers. The core layer comprises a first polymer composition, wherein the first polymer composition comprises at least 50 wt% by weight of a first metallocene linear low-density polyethylene (mLLDPE) based on the first polymer composition. The multilayer film is biaxially oriented.

[0155] The first mL LDPE comprises 80 wt% to 99 wt% ethylene-derived units based on the first mL LDPE and 1 wt% to 20 wt% derivatives derived from one or more C3 to C4 groups. 20 The unit of α-olefin. The first mLLDPE has:

[0156] i) From 0.900 g / cm 3 Up to 0.940 g / cm 3 Density within the range;

[0157] ii) Composition distribution width index (CDBI) less than or equal to 40%;

[0158] iii) Melt index (I2) in the range of 0.1 g / 10 min to 5.0 g / 10 min; and

[0159] iv) Broad orthogonal copolymer distribution.

[0160] The first outer layer comprises a second polymer composition, and the second outer layer comprises a third polymer composition, wherein the second and third polymer compositions are the same or different and are each independently comprised of:

[0161] i) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min.

[0162] ii) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min.

[0163] iii) High-density polyethylene (HDPE); or

[0164] iv) its combination

[0165] In a further embodiment of the multilayer film, in addition to the limitations described above, the multilayer film may have one or more of the following features:

[0166] a) In the comonomer distribution analysis, the broad orthogonal comonomer distribution includes at least a first peak and a second peak, wherein the first peak has a log(M) value ranging from 4.0 to 5.4. w The maximum value of ) and the elution temperature of temperature-elution fractionation (TREF) from 70.0°C to 100.0°C, and the second peak in the comonomer distribution analysis has log(M) values ​​in the range of 5.0 to 6.0. w The maximum value under the specified value and the TREF elution temperature from 40.0°C to 60.0°C;

[0167] b) Broad orthogonal copolymer distribution includes T values ​​ranging from 5 to 10. 75 -T 25 Value, where T 25 It is the temperature in degrees Celsius at which the first 25% of mL LDPE was eluted, and T 75 It is the temperature at which 75% of the first mLLDPE is eluted, measured in degrees Celsius, by temperature-elution fractionation (TREF).

[0168] c) The first polymer composition further comprises:

[0169] i) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min.

[0170] ii) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min.

[0171] iii) High-density polyethylene (HDPE); or

[0172] iv) Their combination;

[0173] d) The multilayer film does not contain low-density polyethylene;

[0174] e) The multilayer film has a thickness ranging from 2, 10, 20, 40 or 45 µm to 50, 100, 150, 200 or 250 µm;

[0175] f) The thickness of the core layer is in the range of 25%, 35%, 45% or 55% to 75%, 80%, 85% or 90% of the total thickness of the multilayer film.

[0176] g) Biaxial orientation includes machine direction (MD) orientation draw ratios ranging from 2.0:1 to 7.5:1, from 2.5:1 to 7.0:1, from 3.0:1 to 6.5:1, or from 3.5:1 to 6.0:1, and transverse direction (TD) orientation draw ratios ranging from 6.5:1 to 11.5:1, from 7.0:1 to 11.0:1, from 7.5:1 to 10.5:1, or from 8.0:1 to 10.0:1;

[0177] h) The membrane has one or more of the following:

[0178] i) Machine-direction (MD) contraction force in the range of 700 mN to 1,400 mN;

[0179] ii) Normalized machine direction (MD) contraction force in the range of 23.3 mN / µm to 46.7 mN / µm;

[0180] iii) Lateral (TD) contraction force in the range of 700 mN to 1,400 mN; and

[0181] iv) Normalized transverse (TD) contractile force in the range of 23.3 mN / µm to 46.7 mN / µm;

[0182] v) The membrane has a shrinkage temperature in the range of 120°C to 170°C;

[0183] vi) The first polymer composition comprises a first mLLDPE in an amount ranging from 50 wt% to 95 wt% based on the total weight of the first polymer composition and an HDPE in an amount ranging from 5 wt% to 50 wt%.

[0184] vii) The first outer layer and the second outer layer each independently contain a narrow-CD mLLDPE in an amount greater than or equal to 50 wt% of the total weight of the first outer layer and the second outer layer; and

[0185] viii) The first outer layer and / or the second outer layer each independently contain anti-adhesion additives.

[0186] In some embodiments, the method for organizing shrink wrap includes arranging two or more adjacent items in one or more rows of two or more items to form an organized bundle. The organized bundle defines a Cartesian coordinate system having a first horizontal axis parallel to the one or more rows, a second horizontal axis perpendicular to the one or more rows, and a vertical axis. The method further includes wrapping the organized bundle in a multilayer film at a temperature ranging from 10°C to 40°C to form a wrapped bundle, wherein:

[0187] i) A multilayer membrane forming tube, which encloses the bundled items;

[0188] ii) The tube has a first opening at one end of the bundle and a second opening at the other end of the bundle; and

[0189] iii) The tube is oriented such that the central axis of the tube is parallel to the first horizontal axis, the second horizontal axis, or the vertical axis.

[0190] The method further includes heating the bundle of packages to a temperature sufficient to cause the tube to shrink to conform to the outermost surface of the bundle to form a shrink-wrapped bundle.

[0191] The biaxially oriented multilayer film used in this method comprises at least a first outer layer, a second outer layer, and a core layer disposed between the first and second outer layers. The core layer contains a first polymer composition comprising at least 50 wt% by weight of a first metallocene linear low-density polyethylene (mLLDPE) and optionally up to 50 wt% by weight of a second polymer composition, wherein:

[0192] a) The first mLLDPE comprises 80 wt% to 99 wt% ethylene-derived units based on the first mLLDPE and 1 wt% to 20 wt% derivatives derived from one or more C3 to C4 groups. 20 The unit of α-olefin, and having:

[0193] i) From 0.900 g / cm 3 Up to 0.940 g / cm 3 Density within the range;

[0194] ii) Composition distribution width index (CDBI) less than or equal to 40%;

[0195] iii) Melt index (I2) in the range of 0.1 g / 10 min to 5.0 g / 10 min; and

[0196] iv) Broad orthogonal copolymer distribution; and

[0197] b) The first outer layer comprises a second polymer composition, and the second outer layer comprises a third polymer composition, wherein the second and third polymer compositions are the same or different and are each independently comprised of:

[0198] i) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min.

[0199] ii) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min.

[0200] iii) High-density polyethylene (HDPE); or

[0201] iv) Its combination.

[0202] In some embodiments of the method, the membrane further includes one or more additional constraints as described above.

[0203] In some embodiments of the method, the method is further characterized by one or more of the following:

[0204] a) The first and second openings are each reduced to substantially circular openings, having a maximum diameter less than the minimum size of the shape defined by the outer periphery of the bundle of tidying up projected onto a plane perpendicular to the central axis.

[0205] b) The temperature sufficient to cause the tube to shrink is in the range of 120°C to 170°C; and

[0206] c) The bundles are wrapped in a way that the machine orientation of the membrane is perpendicular to the central axis of the tube.

[0207] In some embodiments, a good MD / TD shrink balance will provide a better-shaped "bull's eye" for finishing shrink wrapping. A better-shaped bull's eye is a substantially circular hole at the other end of the shrink-wrapped bundle, formed by shrinking the end of a film tube formed around the finished bundle before heating in the shrink channel. Good shrink force is related to the film shrinkage rate, which can potentially increase the linear velocity of the shrink channel. Higher clamping force will provide better securing force for the items to be shrink-wrapped.

[0208] Test methods / polymer characterization

[0209] Density (g / cm³) 3 ): Density was measured according to ASTM D-1505.

[0210] Dynamic mechanical analysis (DMA) rheological measurements (e.g., small strain (10%) oscillatory shear measurements) were performed in frequency sweep mode under full nitrogen occlusion on a Dynamic Rheometrics SR5 Stress rotational rheometer with a 25 mm diameter parallel plate. Polymer samples were appropriately stabilized with antioxidant additives and then preheated in the test fixture for at least one minute to ensure that the normal force decreased back to zero. All DMA experiments were performed at 10% strain, 0.05 to 100 rad / s, and 190°C. Viscoelastic parameters, including storage modulus (Gʹ), loss modulus (Gʺ), phase angle (δ), complex modulus (Gʺ), and complex viscosity (η*), were determined using Orchestrator software. The storage modulus G′ was estimated at a constant loss modulus G″ at 500 Pa (Gʹ at Gʺ (500 Pa)). This was done to characterize and differentiate the viscoelastic properties of the copolymers of the present invention from those of the present invention. This testing technique provides an opportunity to study various characteristics of the polymer melt, in which elastic and viscous moduli (Gʹ and G″), viscosity (η*), and tanδ are generated as functions of dynamic oscillations (frequency) to provide information on rheological behavior related to molecular structure.

[0211] Gel permeation chromatography (GPC) 4D method:

[0212] a) Unless otherwise stated, the molecular weight distribution and moment (Mw, M) n M z M w / M n (etc.), comonomer content (C2, C3, C6, etc.), branching index (gʹ), and CCDI (M w -Specific, 5-95 and M n -M zThe polymer was determined using high-temperature gel permeation chromatography (Polymer Char GPC-IR) equipped with an infrared detector IR5 based on a multi-channel bandpass filter, an 18-angle light scattering detector, and a viscometer. Three Agilent PLgel 10-µm Mixed-B LS columns were used for polymer separation. Aldrich reagent-grade 1,2,4-trichlorobenzene (TCB) with 300 ppm of the antioxidant butylated hydroxytoluene (BHT) was used as the mobile phase. The TCB mixture was filtered through a 0.1-µm Teflon filter and degassed with an in-line degasser before entering the GPC instrument. The nominal flow rate was 1.0 ml / min and the nominal injection volume was 200 µl. The entire system, including the transfer line, column, and detector, was contained in an oven maintained at 145°C. A given amount of polymer sample was weighed and sealed in a standard vial, to which 80 µl of a flow marker (heptane) was added. After loading the vial into the autosampler, the polymer was automatically dissolved in the instrument by adding 8 ml of TCB solvent. The polymer was dissolved at 160°C, with continuous agitation for approximately 1 hour for most polyethylene samples or 2 hours for polypropylene samples. The TCB density used in the concentration calculation was 1.463 g / ml at room temperature and 1.284 g / ml at 145°C. Sample solution concentrations ranged from 0.2 to 2.0 mg / ml, with lower concentrations used for higher molecular weight samples. The concentration (c) at each point in the chromatogram was calculated using the following equation, from the baseline IR5 broadband signal intensity (I): c = βI, where β is the mass constant. The mass recovery was calculated as the ratio of the integral area of ​​the concentration chromatography within the elution volume to the injection mass (equal to the predetermined concentration multiplied by the injection loop volume). The conventional molecular weight (IR MW) was determined by combining a universal calibration relationship with column calibration using a series of monodisperse polystyrene (PS) standards ranging from 700 to 10 mg / mol. The MW for each elution volume was calculated using the following equation:

[0213]

[0214] Variables with the subscript "PS" represent polystyrene, while variables without subscripts represent the test sample. In this method, α PS = 0.67 and K PS= 0.000175, while α and K for other materials are calculated and published as in the literature (Sun, T. et al. Macromolecules 2001, 34, 6812), except for the purposes of this invention and its claims, α = 0.695 and K = 0.000579 for linear ethylene polymers, α = 0.705 and K = 0.0002288 for linear propylene polymers, α = 0.695 and K = 0.000181 for linear butene polymers, and α is 0.695 and K is 0.000579 x (1 - 0.0087 x w²b + 0.000018 x (w²b)) for ethylene-butene copolymers. 2 ), where w2b is the bulk weight percentage of the butene comonomer, and for ethylene-hexene copolymers α is 0.695 and K is 0.000579 x (l - 0.0075 x w2b), where w2b is the bulk weight percentage of the hexene comonomer, and for ethylene-octene copolymers α is 0.695 and K is 0.000579 x (l - 0.0077 x w2b), where w2b is the bulk weight percentage of the octene comonomer. Unless otherwise specified, concentration is expressed in g / cm³. 3 The molecular weight is expressed in g / mol, and the intrinsic viscosity (and therefore K in the Mark-Hovink equation) is expressed in dl / g.

[0215] b) The comonomer composition is determined by the ratio of the IR5 detector intensities corresponding to the CH2 and CH3 channels, calibrated using a series of PE and PP homopolymer / copolymer standards whose nominal values ​​are predetermined by NMR or FTIR. Specifically, this provides methyl groups / 1000 total carbons (CH3 / 1000TC) as a function of molecular weight. The short-chain branched (SCB) content / 1000TC (SCB / 1000TC) is then calculated as a function of molecular weight by applying chain-end correction to the CH3 / 1000TC function, assuming each chain is linear and end-capped with methyl groups. The weight % comonomer is then obtained by the following expression, where f is 0.3, 0.4, 0.6, 0.8, etc., for comonomers such as C3, C4, C6, and C8, respectively:

[0216]

[0217] c) The bulk composition of the polymer from GPC-IR and GPC-4D analyses was obtained by considering the entire signal of the CH3 and CH2 channels between the integration limits of the concentration chromatogram. First, the following ratios were obtained.

[0218]

[0219] d) Then, the same calibration for the CH2 and CH3 signal ratios is applied, as previously mentioned when obtaining CH3 / 1000TC as a function of molecular weight, to obtain the bulk CH3 / 1000TC. The bulk methyl chain-terminus / 1000TC (bulk CH3-terminus / 1000TC) is obtained by weighted averaging over the molecular weight range with chain-terminus correction. Then

[0220]

[0221] And convert the host SCB / 1000TC to host w2 in the same way as described above.

[0222] e) The LS detector was an 18-angle Wyatt Technology high-temperature DAWN HELEOS II. The LS molecular weight (M) at each point in the chromatogram was determined by analyzing the LS output using a Zimm model for static light scattering (Light Scattering from Polymer Solutions, Huglin, MB, ed.; Academic Press, 1972).

[0223]

[0224] Here, ΔR(θ) is the excess Rayleigh scattering intensity measured at scattering angle θ, c is the polymer concentration determined by IR5 analysis, A2 is the second virial coefficient, P(θ) is the shape factor of the monodisperse random coil, and K0 is the optical constant of the system.

[0225]

[0226] Where N A dn / dc is the Avogadro number, and (dn / dc) is the refractive index increment of the system. At 145°C and λ = 665 nm, the refractive index of TCB is n = 1.500. For the analysis of polyethylene homopolymers, ethylene-hexene copolymers, and ethylene-octene copolymers, dn / dc = 0.1048 ml / mg and A2 = 0.0015; for the analysis of ethylene-butene copolymers, dn / dc = 0.1048*(l - 0.00126*w2) ml / mg and A2 = 0.0015, where w2 is the weight percentage of butene comonomer.

[0227] f) The specific viscosity is determined using a high-temperature Agilent (or Viscotek Corporation) viscometer with four capillaries arranged in a Wheatstone bridge configuration with two pressure sensors. One sensor measures the total pressure drop across the detector, while the other sensor, located between the two sides of the bridge, measures the pressure difference. The specific viscosity η of the solution flowing through the viscometer is calculated from their outputs. s The intrinsic viscosity η at each point in the chromatogram. s From the equation [η] = η s / c is calculated, where c is the concentration and is determined by the IR5 broadband channel output. The viscosity MW at each point is calculated as M = K PS M aps+1 / [η], where α ps It is 0.67 and K ps It is 0.000175.

[0228] g) Branching index (gʹ) vis The output of the GPC-IR5-LS-VIS method is calculated as follows. The average intrinsic viscosity of the sample [η] 平均 Through the following calculations:

[0229]

[0230] The sum is taken from all chromatographic slices i between the integration limits.

[0231] h) Branching index gʹ vjs Defined as gʹ vjs = ([η] 平均 ) / (KM v α ), where M v The viscosity-average molecular weight is based on the molecular weight determined by LS analysis, and K and α are for a reference linear polymer. For the purposes of this invention and its claims, for linear ethylene polymers, α = 0.695 and K = 0.000579; for linear propylene polymers, α = 0.705 and K = 0.0002288; for linear butene polymers, α = 0.695 and K = 0.000181; for ethylene-butene copolymers, α = 0.695 and K is 0.000579 x (1 - 0.0087 w²b + 0.000018 x (w²b)). 2), where w2b is the bulk weight percentage of the butene comonomer, and for ethylene-hexene copolymers α is 0.695 and K is 0.000579*(1 - 0.0075 x w2b), where w2b is the bulk weight percentage of the hexene comonomer, and for ethylene-octene copolymers α is 0.695 and K is 0.000579*(1 - 0.0077 x w2b), where w2b is the bulk weight percentage of the octene comonomer. Unless otherwise specified, concentration is expressed in g / cm³. 3 The molecular weight is expressed in g / mol, and the intrinsic viscosity (and therefore K in the Mark-Hovink equation) is expressed in dl / g. The calculation of the w2b value is as discussed above.

[0232] High load melt index (g / 10 min. or dg / min.): HLMI, also known as I 21 Or I 21.6 (Based on the 21.6 kg load used in the test), it was measured according to ASTM D-1238, 190°C, 21.6 kg.

[0233] Melt index (g / 10 min. or dg / min.): MI, also known as I2 or I 2.16 (Based on the 2.16 kg load used in the test), it was measured according to ASTM D-1238, 190°C, 2.16 kg.

[0234] Small-angle oscillating shear (SAOS) frequency scanning melt rheology experiments were conducted at 190°C using a 25 mm conical plate (1° and flat plate construction) on an MCR301 controlled strain / stress rheometer (Anton Paar GmbH). Sample test discs (25 mm diameter, 1 mm thickness) were prepared by compression molding of granules (which could be made from fiber samples if necessary) at 190°C using a Schwaben Than laboratory press (200T). A typical cycle for sample preparation consisted of 1 minute without pressure, followed by 1.5 minutes under pressure (50 bar), and then cooling over 5 minutes between water-cooled plates. Samples were first equilibrated at 190°C for 13 minutes to eliminate any prior thermal and crystallization history. Next, strain values ​​from 500 rad / s to 0.0232 were measured at 6 points / orders of magnitude, representing 10% of the linear viscoelastic region determined by the strain scanning experiments. Angular frequency scans were performed in rad / s. All experiments were conducted in a nitrogen atmosphere to minimize any degradation of the samples during rheological testing.

[0235] Haze is the total haze measured according to ASTM D1003; gloss at 60° angle and gloss at 20° angle are measured according to ASTM D2457; transparency is measured according to ASTM D1746; Elmendorf tear value is measured according to ASTM D1922.

[0236] Shrinkage force and contractile force are measured using a Retramat™ device based on ISO 14616, reported in Newtons (N). The method involves exposing two membrane samples to a given temperature for a given time and then cooling them to room temperature, simulating what occurs inside a shrinkage device. The Retramat device is equipped with a heated oven. During the test, one sample is connected to a force sensor, and the other to a displacement sensor. Thermocouples are used to track the temperature a few millimeters from the center of the sample. The three parameters (force-displacement-temperature) are continuously displayed on the Retramat and recorded on a laboratory PC. Shrinkage force is defined as the force exerted by the membrane when it reaches a temperature corresponding to the temperature at which stress was induced during manufacturing. Contractile force is defined as the force exerted by the membrane during the cooling process. The test conditions are: the oven is heated to 160°C, and the oven is placed around the sample for 30 seconds.

[0237] Example

[0238] The following examples illustrate some embodiments of the invention. Those skilled in the art will understand that the techniques disclosed in the following examples represent techniques discovered by the inventors that work well in the practice of the invention and can therefore be considered as constituting a preferred mode of practice. However, based on this disclosure, those skilled in the art will understand that many changes can be made to the specific embodiments disclosed without departing from the spirit and scope of the invention and still obtaining similar or analogous results.

[0239] -Experimental Materials

[0240] The materials used in Examples 1-4 are shown in Table 1 below.

[0241] Table 1

[0242] *2.16 kg, at 190°C

[0243] -Example 1-14

[0244] In Examples 1-14, films with different layer arrangements and formulations were prepared in more detail below. In each example, six (6) standard 500 ml cans (66 mm diameter x 168 mm height) were shrink-wrapped in a 2x3 configuration in a shrink channel under specified conditions, with the bullseye of the package on the side of the package having two cans. The machine orientation (MD) of the film applied to each of the 6 cans is indicated as “channel”, where the MD is the same as the path traveling through the shrink channel, or “perpendicular”, where the MD is perpendicular to the path traveling through the shrink channel. The shrink-wrapping performance of each example is reported in the table below.

[0245] -Example 1-11

[0246] In Comparative Examples 1-11, shrink films with layer distributions A / B / C and a thickness of 30 µm and a relative thickness of 1 / 2 / 1, respectively, were prepared. Layers A and C were 50 wt% PE1 and 50 wt% PE4, respectively. Layer B was 40 wt% PE4, 45 wt% HDPE1, and 15 wt% LDPE1. The test conditions and shrinkage properties of Examples 1-11 are reported in Table 2 below.

[0247] Table 2

[0248] 1. Relative to the direction of movement of the contraction channel

[0249] -Example 12

[0250] In Comparative Example 12, shrink films with layer distributions A / B / C and thicknesses of 50 µm and relative thicknesses of 1 / 2 / 1 were prepared. Layers A and C were each 100 wt% PE2. Layer B was 60 wt% PE2 and 40 wt% PE4. The test conditions and shrinkage properties of Example 12 are reported in Table 3 below.

[0251] Table 3

[0252] 1. Relative to the direction of movement of the contraction channel

[0253] - Examples 13 and 14

[0254] In Examples 13 and 14 of this invention, shrink films were prepared having a thickness of 30 µm and a layer distribution A / B / C / D / E with a relative thickness of 1 / 1 / 10 / 1 / 1, an MD stretch ratio of approximately 4.5:1 to 5.0:1, and a TD stretch ratio of approximately 8.5:1 to 9.5:1, respectively. Layers A and E were each 98 wt% PE3 and 2 wt% AB1. Layers B and D were each 100 wt% PE3. Layer C was 85 wt% PE6 and 15 wt% HDPE2. The test conditions and shrinkage properties of Examples 13 and 14 are reported in Table 4 below.

[0255] Table 4

[0256] 1. Relative to the direction of movement of the contraction channel

[0257] -Example 15-17

[0258] In Examples 15-17, the shrinkage properties of films with different compositions are compared. Example 15 of the present invention is a biaxially oriented polyethylene shrink film (BOPE) as disclosed herein. Comparative Example 16 is a conventional finished shrink film (CS). Comparative Example 17 is a low-density polyethylene finished shrink film (LDPE). Example 15 of the present invention demonstrates a shrinkage force of 1,346 mN at 165°C. The shrinkage force of Example 15 of the present invention is nearly 50 times that of the shrinkage force in Comparative Example 16 (achieved at a temperature of 210°C, 45°C higher than the temperature of Example 15). The shrinkage force of Example 15 of the present invention is approximately 10 times that of the shrinkage force in Comparative Example 17 (achieved at a temperature of 195°C, 30°C higher than the temperature of Example 15). This is... Figure 1 The graph shows the trace of Retramat™ shrinkage force versus time, where maximum shrinkage force was achieved for each type of membrane at the temperatures disclosed above. Figure 1 In Table 5, the four traces indicated by Example 15 represent four experiments conducted using the membrane of Example 15; the two traces indicated by Example 16 represent two experiments conducted using the membrane of Example 16; and the single trace indicated by Example 17 represents a single experiment conducted using the membrane of Example 17. Table 5 discloses the shrinkage temperatures (already described above, but...) Figure 1 (not shown in the traces); and from Figure 1 The Retramat™ traces obtained clearly show quantitative load measurements (shrinkage force, indicated by the initial peak of the load value on the Retramat™ trace, obtained in this case for approximately 20–30 seconds per membrane; and clamping force, indicated by the lowest load force in the stable region of the approximately constant load in the Retramat™ trace).

[0259] Based on this test data, the shrinkage force of the biaxially oriented polyethylene film (Example 15) disclosed herein is significantly higher than that of conventional finished shrink films (Example 16) and LDPE films (Example 17). Furthermore, the shrinkage temperature of the biaxially oriented polyethylene film disclosed herein is significantly lower than that of conventional CS and LDPE films. Clamping force is not critical in these experiments, as it can be controlled by adjusting the film thickness and / or film formulation, as is known to those skilled in the art. Instead, the key finding of these experiments is that the shrinkage force obtained with the BOPE film (Example 15) is significantly greater, and in particular, the shrinkage temperature of Example 15 is lower compared to others. Such a film with a lower shrinkage temperature offers several advantages due to reduced film tackiness when shrinking for packaging (because higher temperatures that could cause tackiness can be avoided at such a lower shrinkage temperature while still achieving the desired shrink wrapping effect).

[0260] Table 5

[0261] Although the invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and alterations may be made herein without departing from the spirit and scope of the invention as defined by the appended claims. The ranges of various features and properties disclosed herein are listed in a progressively narrowing form. However, it should be understood that for the same feature or property, any lower endpoint of any range may be paired with any upper endpoint, and such pairing is also intended to be disclosed herein. All patents, test procedures, and other documents referenced in this application are fully incorporated herein by reference in all jurisdictions where such incorporation is permitted. Furthermore, the scope of this application is not intended to be limited to specific embodiments of the processes, machines, apparatuses, methods, and / or steps described in the specification. As will be readily understood by one of ordinary skill in the art from the disclosure of this invention, processes, machines, apparatuses, methods, and / or steps, whether currently existing or to be developed thereafter, can be utilized to perform substantially the same function or achieve substantially the same results as the corresponding embodiments described herein. Therefore, the appended claims are intended to include such processes, machines, apparatuses, methods, and / or steps within their scope.

Claims

1. A multilayer membrane, the multilayer membrane comprising at least a first outer layer, a second outer layer, and a core layer disposed between the first outer layer and the second outer layer, the core layer comprising a first polymer composition comprising at least 50 wt% by weight of a first metallocene linear low-density polyethylene (mLLDPE) based on the weight of the first polymer composition, wherein: a) The first mLLDPE comprises 80 wt% to 99 wt% ethylene-derived units based on the first mLLDPE and 1 wt% to 20 wt% derivatives derived from one or more C3 to C4 groups. 20 The unit of α-olefin, and having: i) From 0.900 g / cm 3 Up to 0.940 g / cm 3 Density within the range; ii) Composition distribution width index (CDBI) less than or equal to 40%; iii) Melt index (I2) in the range of 0.1 g / 10 min to 5.0 g / 10 min; and iv) Broad orthogonal copolymer distribution; b) The first outer layer comprises a second polymer composition, and the second outer layer comprises a third polymer composition, wherein the second and third polymer compositions are the same or different and each comprises independently: i) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min. ii) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min. iii) High-density polyethylene (HDPE); or iv) their combination; and c) The multilayer film is biaxially oriented.

2. The multilayer film as described in claim 0, wherein, The broad orthogonal comonomer distribution of the first mLLDPE is characterized by at least a first peak and a second peak in the comonomer distribution analysis, wherein the first peak has a log(M) value between 4.0 and 5.

4. w The maximum value of the value and the temperature rise elution fractionation (TREF) elution temperature from 70.0°C to 100.0°C, and the second peak in the comonomer distribution analysis has a log(M) value of 5.0 to 6.

0. w The maximum value under the value and the TREF elution temperature from 40.0°C to 60.0°C.

3. The multilayer film as described in claim 0 or claim 2, wherein, The broad orthogonal comonomer distribution of the first mLLDPE is characterized by the first mLLDPE having a T value in the range of 5 to 10. 75 -T 25 Value, where T 25 It is the temperature in degrees Celsius at which 25% of the first mL LDPE was eluted, and T 75 The temperature at which 75% of the first mLLDPE was eluted, measured in degrees Celsius, is determined by temperature-elution fractionation (TREF).

4. The multilayer film as claimed in claim 0 or any one of claims 2-3, wherein, The first polymer composition further comprises: a) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min. b) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min. c) High-density polyethylene (HDPE); or d) Its combination.

5. The multilayer film as claimed in claim 0 or any one of claims 2-4, wherein, The multilayer film does not contain low-density polyethylene.

6. The multilayer film as claimed in claim 0 or any one of claims 2-5, wherein, The multilayer film has a thickness of less than or equal to 250 µm.

7. The multilayer film as claimed in claim 0 or any one of claims 2-6, wherein, The thickness of the core layer is in the range of 25% to 90% of the total thickness of the multilayer film.

8. The multilayer film as claimed in claim 0 or any one of claims 2-7, wherein, The biaxial orientation includes a machine direction (MD) orientation draw ratio ranging from 2.0:1 to 7.5:1 and a transverse direction (TD) orientation draw ratio ranging from 6.5:1 to 11.5:

1.

9. The multilayer film as claimed in claim 0 or any one of claims 2-8, wherein, The membrane has one or more of the following: a) Machine-direction (MD) contraction force in the range of 700 mN to 1,400 mN; b) Normalized machine direction (MD) contraction force in the range of 23.3 mN / µm to 46.7 mN / µm; c) Lateral (TD) contraction force in the range of 700 mN to 1,400 mN; as well as d) Normalized transverse (TD) contraction force in the range of 23.3 mN / µm to 46.7 mN / µm.

10. The multilayer film as claimed in claim 0 or any one of claims 2-9, wherein, The membrane has a shrinkage temperature in the range of 120°C to 170°C.

11. The multilayer film as claimed in claim 0 or any one of claims 2-10, wherein, The first polymer composition comprises a first mLLDPE in an amount ranging from 50 wt% to 95 wt% based on the total weight of the first polymer composition and an HDPE in an amount ranging from 5 wt% to 50 wt%.

12. The multilayer film as claimed in claim 0 or any one of claims 2-11, wherein, The first outer layer and the second outer layer each independently contain a narrow-CD mLLDPE in an amount greater than or equal to 50 wt% of the total weight of the first outer layer and the second outer layer.

13. The multilayer film as claimed in claim 0 or any one of claims 2-12, wherein, The first outer layer and / or the second outer layer each independently contain an anti-adhesion additive.

14. A method for sorting shrink wrap, the method comprising: a) Arrange two or more adjacent items in one or more rows of two or more items each to form a neat bundle, wherein the Cartesian coordinate system is defined by a first horizontal axis parallel to the row or more, a second horizontal axis perpendicular to the row or more; and a vertical axis. b) The prepared bundle is wrapped in a multilayer film at a temperature ranging from 10°C to 40°C to form a wrapped bundle, wherein: i) The multilayer film forming tube, the tube enclosing the bundled items; ii) The tube has a first opening at one end of the bundle and a second opening at the other end of the bundle; and iii) The tube is oriented such that the central axis of the tube is parallel to the first horizontal axis, the second horizontal axis, or the vertical axis; c) Heat the bundle of the package to a temperature sufficient to cause the tube to shrink to conform to the temperature of the outermost surface of the bundle to form a shrink-wrapped bundle; The multilayer film comprises at least a first outer layer, a second outer layer, and a core layer disposed between the first outer layer and the second outer layer. The core layer comprises a first polymer composition comprising at least 50 wt% by weight of a first metallocene linear low-density polyethylene (mLLDPE) and optionally up to 50 wt% by weight of a second polymer composition, wherein: i) The first mLLDPE comprises 80 wt% to 99 wt% ethylene-derived units based on the first mLLDPE and 1 wt% to 20 wt% derivatives derived from one or more C3 to C4 groups. 20 The unit of α-olefin, and having: (1) From 0.900 g / cm 3 Up to 0.940 g / cm 3 Density within the range; (2) Composition distribution width index (CDBI) less than or equal to 40%; (3) Melt index (I2) in the range of 0.1 g / 10 min to 5.0 g / 10 min; and (4) Wide orthogonal copolymer distribution; ii) The first outer layer comprises a second polymer composition, and the second outer layer comprises a third polymer composition, wherein the second and third polymer compositions are the same or different and each comprises independently: (1) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min. (2) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min. (3) High-density polyethylene (HDPE); or (4) Its combination; and iii) The membrane is biaxially oriented.

15. The method of claim 0, wherein, The first polymer composition further comprises: a) Narrow-CD mLLDPE with a CDBI greater than or equal to 50% and a melt index (I2) greater than or equal to 1.2 dg / min. b) Long-chain branched (LCB) mLLDPE with a CDBI of greater than or equal to 60% and a melt index (I2) of less than 1.2 dg / min. c) High-density polyethylene (HDPE); or d) Its combination.

16. The method of claim 0 or claim 15, wherein, The first opening and the second opening are each reduced to substantially circular openings, having a maximum diameter smaller than the minimum size of the shape defined by the outer periphery of the bundle of tidying up projected onto a plane perpendicular to the central axis.

17. The method of claim 0 or any one of claims 15-16, wherein, The temperature sufficient to cause the tube to shrink is in the range of 120°C to 170°C.

18. The method of claim 0 or any one of claims 15-17, wherein, The wrapping of the bundle during the sorting process is such that the machine orientation of the membrane is perpendicular to the central axis of the tube.

19. The method of claim 0 or any one of claims 15-18, wherein, The first polymer composition comprises a first mLLDPE in an amount ranging from 50 wt% to 95 wt% based on the total weight of the first polymer composition and an HDPE in an amount ranging from 5 wt% to 50 wt%.

20. The method of claim 0 or any one of claims 15-19, wherein, The first outer layer and the second outer layer each independently contain a narrow-CD mLLDPE in an amount greater than or equal to 50 wt% of the total weight of the first outer layer and the second outer layer.

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