WO2025006214A1 - Multilayer film having enhanced creep, tear, and dart - Google Patents

Abstract

A multilayer film (100) may comprise a first skin layer (102), a second skin layer (104), and a core(106) positioned between the first skin layer (102) and the second skin layer (104). The first skin layer (102) and the second skin layer (104) may independently comprise linear low density polyethylene (LLDPE) resin. The core (106) may comprise a first core layer (108), a second core layer (110), and a third core layer (112). The first core layer (108) and the third core layer (112) may independently comprise high density polyethylene (HDPE), LLDPE, or a combination of these. The second core layer (110) may comprise an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer. The thickness of the second core layer (110) may be less than 15 % of a thickness of the multilayer film (100). At least one of the core layers (108,110,112) may comprise HDPE.

Description

MULTILAYER FILM HAVING ENHANCED CREEP, TEAR, AND DART

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of Spanish Patent Application No. P202330544 filed June 28, 2023, the contents of which are incorporated in their entirety herein.

TECHNICAL FIELD

[0002] Embodiments described herein generally relate to multilayer films and, more specifically, to multilayer films used for heavy duty shipping sacks (HDSS).

BACKGROUND

[0003] In the interest of improving sustainability and reducing cost, it is desirable to reduce the thickness of the films used to make heavy-duty shipping sacks ("HDSS "). Reducing thickness reduces the amount of material employed and therefore the total emissions. However, this reduction in thickness (also called “downgauging”) must be accomplished without sacrificing impact resistance, tear resistance, and creep resistance. It becomes progressively more difficult to meet these specifications as the film is downgauged, especially below 100 pm.

[0004] With regard to creep, it is well known that creep is inversely proportional to the cube of the thickness when thickness is near 100 pm. Creep can be improved by adding more HDPE and increasing the overall film stiffness. However, this worsens other mechanical properties, such as impact resistance.

BRIEF SUMMARY

[0005] Accordingly, thinner films which can still meet impact resistance, tear resistance, and creep resistance are desired. Embodiments of the present disclosure meet this need by providing a multilayer film comprising a core layer which comprises ethylene-acrylate copolymer, ethylenepropylene copolymer, or combinations thereof. Further embodiments of the present disclosure meet this need by providing a core layer which comprises ethylene-acrylate copolymer, ethylenepropylene copolymer, or combinations thereof and which is relatively thin, such as less than 20 % of the thickness of the multilayer film.

[0006] According to one embodiment of the present disclosure, a multilayer film may comprise a first skin layer, a second skin layer, and a core positioned between the first skin layer and the second skin layer. The first skin layer and the second skin layer may independently comprise linear low density polyethylene (LLDPE) resin. The core may comprise a first core layer, a second core layer, and a third core layer. The first core layer and the third core layer may independently comprise high density polyethylene (HDPE), linear low density polyethylene (LLDPE) or a combination of these. The second core layer may comprise an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer. The thickness of the second core layer may be less than 15 % of a thickness of the multilayer film. At least one of the core layers may comprise HDPE.

[0007] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows and the claims.

[0008] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced. Where two embodiments include the same component, like numerals will be used to describe like components (e.g. first layer 204 in FIG. 2 will correspond to first layer 104 in FIG. 1).

[0010] FIG. 1 illustrates a side view of one embodiment of the present multilayer film.

[0011] FIG. 2 illustrates a side view of one embodiment of the present multilayer film.

DETAILED DESCRIPTION

[0012] Specific embodiments of the present application will now be described. The disclosure may be embodied in different forms and should not be construed as limited to the embodiments set forth in this disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0013] As discussed above, thinner films which can still meet impact resistance, tear resistance, and creep resistance for use in HDSS are desired. Embodiments of the present disclosure meet this need by providing a multilayer fdm comprising a second core layer which comprises ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer; and which is relatively thin, such as less than 15 % of the thickness of the multilayer fdm.

[0014] Definitions

[0015] "Ethylene-acrylate copolymer" refers to ethylene-based polymers with acrylate comonomers. The ethylene-acrylate copolymers of the present disclosure may comprise a majority (greater than 50 wt. %) of the residues of ethylene monomers, based on the total polymer weight of the ethylene acrylate copolymer. The remainder of the polymer weight of the ethylene-acrylate copolymer may comprise the residues acrylate monomers.

[0016] "Ethylene-propylene copolymer" refers to ethylene-based polymers with propylene comonomers. The ethylene-propylene copolymers of the present disclosure may comprise a majority (greater than 50 wt. %) of the residues of ethylene monomers, based on the total polymer weight of the ethylene-propylene copolymer. The remainder of the polymer weight of the ethylene-propylene copolymer may comprise the residues propylene monomers.

[0017] “Residues” refers to the portion of a polymer derived from a specific monomer.

[0018] "gf/pm" refers to grams force per micron.

[0019] "Heavy duty shipping sacks", also referred to herein as "HDSS" refers to packaging designed to contain large quantities of granular goods, such as polymer resins, solid chemicals, cement, animal feeds, rice and similar goods. The HDSS disclosed herein may be suitable to contain more than 20 kg of granular goods.

[0020] "Multilayer film" refers to any structure having more than one layer. For example, the multilayer structure may have five or more layers, such as 6, 7, 8 9, 10, or 11 layers. In embodiments, the multilayer film may have an odd number of layers, such as 5, 6, 9, or 11 layers. [0021] “Polyethylene” as used herein, refers to "ethylene-based polymer" shall mean polymers comprising greater than 50% by weight of units which have been derived from ethylene monomer. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include Tow Density Polyethylene (EDPE); Einear Low Density Polyethylene (LLDPE); Ultra Low Density Polyethylene (ULDPE); Very Low Density Polyethylene (VLDPE); single-site catalyzed Linear Low Density Polyethylene, including both linear and substantially linear low density resins (m- LLDPE); Medium Density Polyethylene (MDPE); and Eligh Density Polyethylene (EIDPE).

[0022] The term “ULDPE” is defined as a polyethylene -based copolymer having a density in the range of 0.895 to 0.915 g/cc.

[0023] The term “LDPE” may also be referred to as “high pressure ethylene polymer” or “highly branched polyethylene” and is defined to mean that the polymer is partly or entirely homopolymerized or copolymerized in autoclave or tubular reactors at pressures above 14,500 psi (100 MPa) with the use of free-radical initiators, such as peroxides (see for example U.S. Pat. No. 4,599,392, incorporated herein by reference).

[0024] The term “LLDPE”, includes resins made using the traditional Ziegler-Natta catalyst systems as well as single-site catalysts such as metallocenes (sometimes referred to as “m- LLDPE”). LLDPEs contain less long chain branching than LDPEs and include the substantially linear ethylene polymers which are further defined in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272, U.S. Pat. No. 5,582,923 and U.S. Pat. No. 5,733,155; the homogeneously branched linear ethylene polymer compositions such as those in U.S. Pat. No. 3,645,992; the heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Pat. No. 4,076,698; and/or blends thereof (such as those disclosed in U.S. Pat. No. 3,914,342 or U.S. Pat. No. 5,854,045). The LLDPE can be made via gas-phase, solutionphase or slurry polymerization or any combination thereof, using any type of reactor or reactor configuration known in the art, including, but not limited to, gas and solution phase reactors.

[0025] The term “C6 LLDPE” refers to ethylene based polymers produced from ethylene monomer and hexene comonomer. Similarly, “C4 LLDPE” refers to ethylene-based polymers produced from ethylene monomer and butene comonomer, and “C8 LLDPE” refers to ethylenebased polymers produced from ethylene monomer and octene comonomer.

[0026] The term “HDPE” generally refers to polyethylenes having densities greater than about 0.935 g/cm³ and up to about 0.980 g/cm³, which are generally prepared with Ziegler-Natta catalysts, chrome catalysts or single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, phosphinimine catalysts & polyvalent aryloxyether catalysts (typically referred to as bisphenyl phenoxy).

[0027] "Polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The term polymer thus embraces the term homopolymer (employed to refer to polymers prepared from only one type of monomer, with the understanding that trace amounts of impurities can be incorporated into the polymer structure), and the term copolymer or interpolymer. Trace amounts of impurities (for example, catalyst residues) may be incorporated into and/or within the polymer. A polymer may be a single polymer or a polymer blend.

[0028] As used herein, the term “copolymer” means a polymer formed by the polymerization reaction of at least two structurally different monomers. The term “copolymer” is inclusive of terpolymers. For example, ethylene copolymers, such as ethylene-propylene copolymers, include at least two structurally different monomers (e.g., ethylene-propylene copolymer includes copolymerized units of at least ethylene monomer and propylene monomer) and can optionally include additional monomers or functional materials or modifiers, such as acid, acrylate, or anhydride functional groups. Put another way, the copolymers described herein comprise at least two structurally different monomers, and although the copolymers may consist of only two structurally different monomers, they do not necessarily consist of only two structurally different monomers and may include additional monomers or functional materials or modifiers.

[0029] "wt. %" means weight percentage.

[0030] “g/10 min” means grams per ten minutes.

[0031] “g/cm³" also written “g/cc” means grams per cubic centimeter.

EMBODIMENTS

[0032] As depicted in FIG. 1, a multilayer film 100 may comprise a first skin layer 102, a second skin layer 104, and a core 106. The core 106 may be positioned between the first skin layer 102 and the second skin layer 104. The core 106 may comprise a first core layer 108, a second core layer 110, and a third core layer 112.

[0033] The Second Core Eayer

[0034] The second core layer 110 may comprise an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer. In embodiments, the second core layer 110 may comprise at least 50 wt. %, such as at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, at least 95 wt. %, at least 99 wt. %, or even at least 99.9 wt. % of the ethylene-based copolymer, based on the total polymer weight of the second core layer 110. [0035] The second core layer 110 may comprise an ethylene-acrylate copolymer (such as ethylene/butyl acrylate copolymer, ethylene/ ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and/or ethylene/vinyl acetate copolymer). The ethylene-acrylate copolymer may comprise residues of an acrylate monomer, such as a C2-C-6 acrylate monomer or a C2 to C5 monomer. In embodiments, the ethylene-acrylate copolymer may comprise from 1 wt. % to 49 wt. %, such as from 5 wt. % to 49 wt. %, from 10 wt. % to 49 wt. %, from 20 wt. % to 49 wt. %, from 30 wt. % to 49 wt. %, from 40 wt. % to 49 wt. %, from 1 wt. % to 40 wt. %, from 1 wt. % to 30 wt. %, from 1 wt. % to 20 wt. %, from 1 wt. % to 10 wt. %, from 10 wt. % to 40 wt. %, from 20 wt. % to 30 wt. %, from 15 wt. % to 30 wt. %, or any subset thereof of the acrylate monomer, on the basis of the total polymer weight of the ethylene-acrylate copolymer. It should be understood that at least 80 wt. %, at least 90 wt. %, at least 99 wt. %, or even at least 99.9 wt. % of the ethylene-acrylate copolymer may comprise the combination of ethylene residues and acrylate residues, based on the total polymer weight of the ethylene-acrylate copolymer. Suitable ethylene-acrylate copolymers may include the ETVATOY™ line of polymers, available from Dow Inc., Midland, MI.

[0036] The ethylene-acrylate copolymer may have a melt index (I2) of from 0.5 g/10 min to 8 g/10 min. In embodiments, the ethylene-acrylate copolymer may have a melt index (I2) of from 0.5 g/10 min to 8 g/10 min, from 0.5 g/10 min to 6 g/10 min, from 0.5 g/10 min to 4 g/10 min, from 0.5 g/10 min to 2 g/10 min, from 1 g/10 min to 10 g/10 min, from 2 g/10 min to 10 g/10 min, from 4 g/10 min to 10 g/10 min, from 6 g/10 min to 10 g/10 min, from 8 g/10 min to 10 g/10 min, from 2 g/10 min to 8 g/10 min, from 4 g/10 min to 6 g/10 min, or any subset thereof.

[0037] The second core layer 110 may comprise an ethylene-propylene copolymer. The ethylene-propylene copolymer may comprise residues of a propylene monomer. In embodiments, the ethylene-propylene copolymer may comprise from 1 wt. % to 49 wt. %, such as from 5 wt. % to 49 wt. %, from 10 wt. % to 49 wt. %, from 20 wt. % to 49 wt. %, from 30 wt. % to 49 wt. %, from 40 wt. % to 49 wt. %, from 1 wt. % to 40 wt. %, from 1 wt. % to 30 wt. %, from 1 wt. % to 20 wt. %, from 1 wt. % to 10 wt. %, from 10 wt. % to 40 wt. %, from 20 wt. % to 30 wt. %, or any subset thereof of the propylene monomer, on the basis of the total polymer weight of the ethylene-propylene copolymer. In embodiments, the ethylene-propylene copolymer may comprise from 60 wt. % to 95 wt. % of the ethylene monomer and from 5 wt. % to 40 wt. % of the propylene comonomer, on the basis of the total polymer weight of the ethylene-propylene copolymer. It should be understood that at least 80 wt. %, at least 90 wt. %, at least 99 wt. %, or even at least 99 wt. % of the ethylene-propylene copolymer may comprise the combination of ethylene residues and propylene residues, based on the total polymer weight of the ethylenepropylene copolymer. Suitable ethylene-propylene copolymers may include the XUS 39003.00 experimental resin, available from Dow Inc., Midland, MI. Further suitable ethylene-propylene copolymers are described in PCT/US23/061210, which is incorporated by reference herein.

[0038] The comonomer content may be measured using any suitable technique, such as techniques based on nuclear magnetic resonance (“NMR”) spectroscopy, and, for example, by ¹³C NMR analysis as described in U.S. Patent 7,498,282, which is incorporated herein by reference.

[0039] In some embodiments, the ethylene-propylene copolymer may have a density in the range of from 0.865 to 0.920 g/cc. All individual values and subranges of from 0.865 to 0.920 g/cc are disclosed and included herein. For example, the ethylene-propylene copolymer may have a density in the range of from 0.870 to 0.920 g/cc, from 0.880 to 0.910 g/cc, from 0.895 to 0.905 g/cc, or from 0.895 to 0.910 g/cc.

[0040] In some embodiments, the ethylene-propylene copolymer may have a melt index (U) of at least 0.5 g/10 min. All individual values and subranges of at least 0.5 g/10 min are disclosed and included herein. For example, the ethylene-propylene copolymer may have a melt index (I2) of at least 0.5 g/10 min, at least 0.6 g/10 min, at least 0.7 g/10 min, at least 0.8 g/10 min, at least 0.9 g/10 min, or at least 1.0 g/10 min, or can have a melt index (I2) in the range of from 0.5 g/10 min to 500 g/10 min, from 0.5 g/10 min to 200 g/10 min, from 0.5 g/10 min to 100 g/10 min, from 0.5 g/10 min to 50 g/10 min, from 0.5 g/10 min to 10 g/10 min, or from 0.5 g/10 min to 8 g/10 min.

[0041] In some embodiments, the ethylene-propylene copolymer may have a single peak in an improved comonomer composition distribution (ICCD) elution profde between a temperature range of from 40 °C to 100 °C. The improved comonomer composition distribution (ICCD) profde of the ethylene-propylene copolymer can be obtained via the test method described below.

[0042] In some embodiments, the ethylene-propylene copolymer may have a molecular weight distribution (M_w/M_n) in the range of from 1.5 to 5.0. All individual value and subrange of from 1.5 to 5.0 are disclosed and included herein. For example, the ethylene-propylene copolymer may have a molecular weight distribution (M_w/M_n) in the range of from 1.5 to 5.0, from 1.6 to 5.0, from 1.8 to 5.0, from 2.0 to 5.0, from 1.5 to 4.0, from 1.6 to 4.0, from 1.8 to 4.0, from 2.0 to 4.0, from 1.5 to 3.0, from 1.8 to 3.0, from 2.0 to 3.0, from 1.5 to 2.5, from 1.8 to 2.5, or from 2.0 to 2.5. Molecular weight distribution (M_w/M_n) can be measured in accordance with the GPC test method described below.

[0043] In some embodiments, the ethylene-propylene copolymer may be further characterized by having a melt flow ratio (I10/I2) of from 5 to 14. All individual values and subranges of from 5 to 14 are disclosed and included herein. For example, the ethylene-propylene copolymer may have a melt flow ratio (I10/I2) of from 5 to 14, from 6 to 12, from 6 to 10, or from 5 to 10.

[0044] In some embodiments, the ethylene-propylene copolymer may have a heat of fusion in the range of from 40 to 150 J/g. All individual values and subranges of from 40 to 150 J/g are disclosed and included herein. For example, the ethylene-propylene copolymer may have a heat of fusion in the range of from 40 to 108 J/g to 150 J/g, from 45 to 130 J/g, from 50 to 120 J/g, from 60 to 108 J/g, from 70 to 108 J/g, from 80 to 108 J/g, from 90 to 108 J/g, where heat of fusion is measured in accordance with the DSC test method described below.

[0045] The ethylene-based copolymer may be an ethylene/vinyl acetate (EVA) copolymer. The EVA copolymer may comprise from 9 to 28 wt.% vinyl acetate comonomer, based on the total polymer weight of the ethylene/vinyl acetate copolymer. All individual values and subranges of from 9 to 28 wt.% are disclosed and included herein. In embodiments, the ethylene/vinyl acetate copolymer may comprise from 10 to 25 wt.%, from 12 to 23 wt.%, or from 15 to 20 wt.% of vinyl acetate comonomer, based on total weight of the ethylene/vinyl acetate copolymer. Examples of suitable commercially available ethylene/vinyl acetate copolymers include polymers under the name ELVAX™, available from Dow Inc., Midland, MI.

[0046] The second core layer 110 may further comprise a fdler, such as calcium carbonate (CaCC ). 20 to 80 wt. % of calcium carbonate (CaCC ). Without intending to be limited by theory, it has been found that a synergy exists between calcium carbonate fdlers and ethylene-acrylate copolymers which results in improved mechanical properties. However, a variety of fdlers (including CaC'Os) may optionally be used with both ethylene-acrylate copolymers and ethylene- propylene copolymers to provide color and reduce cost. In embodiments, the second core layer 110 may comprise from 0 wt. % to 80 wt. %, such as from 10 wt. % to 80 wt. %, from 20 wt. % to 80 wt. %, from 40 wt. % to 80 wt. %, from 0 wt. % to 60 wt. %, from 0 wt. % to 40 wt. %, from 0 wt. % to 20 wt. %, from 10 wt. % to 70 wt. %, from 20 wt. % to 60 wt. %, from 30 wt. % to 70 wt. %, or any subset thereof of the fdlers, based on the total weight of the second core layer 110.

[0047] As depicted in FIG. 1, the second core layer 110 may be positioned within the core 106 between the first core layer 108 and the third core layer 112. As such, the second core layer 110 may be the central layer of the multilayer film 100, the central layer of the core 106, or both. Alternate embodiments are envisioned where the second core layer is not the central layer of the multilayer film and the core, as long as the second core layer is positioned between the first skin layer and the second skin layer. Without being limited by theory, it is believed that while the second core layer will improve mechanical strength in any internal layer between the first skin layer and the second skin layer, there will be a significant improvement in performance when the second core layer 110 is the central layer. The central layer may be the layer which includes the 50 % point within the multilayer film 100.

[0048] The First, Third, Fourth, and Fifth Core Layers

[0049] Still referring to FIG. 1, the core 106 may comprise a first core layer 108 and a third core layer 112. The first core layer 108 may be positioned between the first skin layer 102 and the second core layer 110. The third core layer 112 may be positioned between the second core layer 110 and the second skin layer. Referring now to FIG. 2, a multilayer film 200 may comprise a first skin layer 202, a second skin layer 204, and a core 206. The core 206 may be positioned between the first skin layer 202 and the second skin layer 204. The core 206 may comprise a first core layer 208, a third core layer 212, and a second core layer 210. The core 206 may further comprise a fourth core layer 214 and a fifth core layer 216.

[0050] The core 206 layers may be arranged in any order. In embodiments, the fourth core layer 214 may be positioned between the first skin layer 202 and the first core layer 208. In embodiments, the fifth core layer 216 may be positioned between the second skin layer 204 and the third core layer 212. In embodiments, the second core layer 210 may be positioned between the first core layer 208 and the third core layer 212. Accordingly, the second core layer 210 may be the central layer. As mentioned previously, it is believed that while the second core layer will add performance in any internal layer between the first skin layer and the second skin layer, there will be a significant improvement in performance when the second core layer is the central layer. [0051] Referring now to FIG. 1 and FIG. 2, the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214, and the fifth core layer 216 may each independently comprise HDPE, LLDPE, or combinations thereof. In embodiments, the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214, and the fifth core layer 216 may each independently comprise at least 70 wt. %, such as at least 80 wt. %, at least 90 wt. %, at least 99 wt. %, or even at least 99.9 wt. % of HDPE, LLDPE, or combinations thereof, based on the total polymer weight of the layer. [0052] At least one of the core 106, 206 layers may comprise high density polyethylene (HDPE). In embodiments, at least two of the core 106, 206 layers may comprise HDPE. In embodiments, at least one layer comprising HDPE may be disposed on each side of the second core layer.

[0053] In embodiments, the multilayer fdm 100, 200 may comprise at least 30 wt. % of the HDPE, based on the total weight of the multilayer film 100, 200. The use of a minimum percentage of HDPE may help to meet density and creep requirements. In embodiments, the multilayer film 100, 200 may comprise at least at least 35 wt. %, at least 40 wt. %, at least 45 wt. %, from 30 wt. % to 45 wt. %, from 35 wt. % to 45 wt. %, from 40 wt. % to 45 wt. %, from 35 wt. % to 40 wt. %, or any subset thereof of HDPE, based on the total weight of the multilayer film 100, 200.

[0054] In embodiments where the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214, and/or the fifth core layer 216 comprise HDPE, the HDPE may have a density greater than 0.940 g/cc, such as greater than 0.945 g/cc, greater than 0.950 g/cc, greater than 0.955 g/cc, greater than 0.960 g/cc, from 0.940 g/cc to 0.965 g/cc, from 0.940 g/cc to 0.960 g/cc, from 0.940 g/cc to 0.955 g/cc, 0.945 g/cc to 0.965 g/cc, or any subset thereof. Without being limited by theory, it is believed that increasing density of the HDPE results in improved creep resistance properties.

[0055] In embodiments where the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214, and/or the fifth core layer 216 comprise an HDPE, the HDPE may have a melt index (E) in the range of from 0.1 g/10 min to 1.5 g/10 min. All individual values and subranges of from 0.1 g/10 min to 1.5 g/10 min are disclosed and included herein. For example, the HDPE may have a melt index (I2) in the range of from 0.1 g/10 min to 1.3 g/10 min, from 0.1 g/10 min to 1.1 g/10 min, from 0.1 g/10 min to 0.9 g/10 min, from 0.1 g/10 min to 0.7 g/10 min, from 0.1 g/10 min to 0.5 g/10 min, from 0.3 g/10 min to 1.5 g/10 min, from 0.5 g/10 min to 1.5 g/10 min, from 0.7 g/10 min to 1.5 g/10 min, from 0.9 g/10 min to 1.5 g/10 min, from 0.3 g/10 min to 1.3 g/10 min, from 0.5 g/10 min to 1.1 g/10 min, or any subset thereof.

[0056] Commercially available examples of HDPE that can be used in the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214, and/or the fifth core layer 216 include those commercially available from Dow Inc. under the name UNIV AL™ including, for example, UNIV AL™ DMDA 6400.

[0057] In embodiments where the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214, and/or the fifth core layer 216 comprise an LLDPE, the LLDPE may have a density less than or equal to 0.930 g/cm³. All individual values and subranges less than or equal to 0.930 g/cm³ are included and disclosed herein; for example, the density of the linear low density polyethylene can be from a lower limit of 0.870 g/cm³ to an upper limit of 0.928, 0.925, 0.920 or 0.915 g/cm³. All individual values and subranges between 0.870 and 0.930 g/cm³ are included and disclosed herein.

[0058] In embodiments where the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214 and/or the fifth core layer 216 comprise an LLDPE, the LLDPE can have a melt index (h) in the range of from 0.1 g/10 min to 1.5 g/10 min. All individual values and subranges of from 0.1 g/10 min to 1.5 g/10 min are disclosed and included herein. For example, the LLDPE can have a melt index (L) in the range of from 0.1 g/10 min to 1.3 g/10 min, from 0.1 g/10 min to 1.1 g/10 min, from 0.1 g/10 min to 0.9 g/10 min, from 0.1 g/10 min to 0.7 g/10 min, from 0.3 g/10 min to 1.5 g/10 min, from 0.5 g/10 min to 1.5 g/10 min, from 0.7 g/10 min to 1.5 g/10 min, from 0.3 g/10 min to 1.3 g/10 min, from 0.5 g/10 min to 1.1 g/10 min, or any subset thereof.

[0059] Commercially available examples of LLDPEs that can be used in the first core layer 108, 208, the third core layer 112, 212, the fourth core layer 214 and/or the fifth core layer 216 include those commercially available from Dow Inc. under the name ELITE™ including, for example, ELITE™ 5400.

[0060] The Skin Layers

[0061] The first skin layer 102, 202 and the second skin layer 104, 204 may independently comprise a linear low-density polyethylene (hereinafter “LLDPE”). In embodiments, the multilayer film 200 may comprise at least 50 wt. %, such as at least 60 wt. %, at least 70 wt. %, at least 80 wt. %, at least 90 wt. %, or even at least 99 wt. % of LLDPE, based on the total polymer weight of the layer.

[0062] In embodiments where first skin layer 102, 202 and/or the second skin layer 104, 204 comprise an LLDPE, the LLDPE may have a density less than or equal to 0.940 g/cm³. All individual values and subranges less than or equal to 0.940 g/cm³ are included and disclosed herein; for example, the density of the LLDPE may be from a lower limit of 0.870 g/cm³, 0.880 g/cm³, 0.890 g/cm³, 0.910 g/cm³, 0.920 g/cm³ to an upper limit of 0.940 g/cm³, 0.938 g/cm³, 0.936 g/cm³, or 0.935 g/cm³. All individual values and subranges between 0.870 g/cm³ and 0.940 g/cm³ are included and disclosed herein.

[0063] In embodiments where the first skin layer 102, 202 and/or the second skin layer 104, 204 comprise an LLDPE, the LLDPE can have a melt index (I2) in the range of from 0.1 g/10 min to 50 g/10 min. All individual values and subranges of from 0.1 g/ 10 min to 50 g/ 10 min are disclosed and included herein. For example, the LLDPE can have a melt index (h) in the range of from 0.1 g/10 min to 40 g/10 min, 0.1 g/10 min to 30 g/10 min, 0.1 g/10 min to 20 g/10 min, 0.1 g/10 min to 10 g/10 min, or 0.1 g/10 min to 5 g/10 min.

[0064] Commercially available examples of LLDPEs that can be used in the multilayer fdm 200 and/or the multilayer fdm 200 include those commercially available from Dow Inc., under the name ELITE™ and under the name DOWLEX™.

[0065] In some embodiments, the first skin layer 102, 202 and/or the second skin layer 104, 204 may comprise a low density polyethylene (LDPE). It should be understood that the first skin layer 102, 202 and the second skin layer 104, 204 may comprise the LDPE in addition to the LLDPE. In embodiments where the multilayer film 200 and/or the multilayer film 200 comprise an LDPE, the LDPE may have a density in the range 0.916 g/cm³ to 0.935 g/cm³. All individual values and subranges of 0.916 g/cm³ to 0.935 g/cm³ are included and disclosed herein; for example, the density of the LDPE can be from a lower limit of 0.916 g/cm³, 0.918 g/cm³, 0.920 g/cm³, or 0.922 g/cm³ to an upper limit of 0.935 g/cm³, 0.933 g/cm³, 0.931 g/cm³, or 0.929 g/cm³.

[0066] In embodiments where the first skin layer 102, 202 and/or the second skin layer 104, 204 comprise an LDPE, the LDPE can have a melt index (I2) in the range of from 0.1 g/10 min to 50 g/10 min. All individual values and subranges of from 0.1 g/10 min to 50 g/10 min are disclosed and included herein. For example, the LDPE can have a melt index (I2) in the range of from 0.1 g/10 min to 40 g/10 min, 0.1 g/10 min to 30 g/10 min, 0.1 g/10 min to 20 g/10 min, 0.1 g/10 min to 10 g/10 min, or 0.1 g/10 min to 5 g/10 min.

[0067] In some embodiments the first skin layer 102, 202 and/or the second skin layer 104, 204 can independently comprise from 0 wt. % to 30 wt. % of the LDPE, based on the total weight of the respective layer. All individual values of 0 wt. % to 30 wt. % are disclosed and included herein. For example, the multilayer film 200 and/or the multilayer film 200 can comprise from 0 wt. % to 25 wt. %, from 0 wt. % to 20 wt. %, from 0 wt. % to 10 wt. %, from 0 wt. % to 5 wt. %, from 5 wt. % to 30 wt. %, from 5 wt. % to 20 wt. %, or any subset thereof, based on the total polymer weight of the respective layer.

[0068] Commercially available examples of LDPEs that can be used in the multilayer film 200 and/or the multilayer film 200 include those commercially available from Dow Inc. under the name AGILITY™.

[0069] The Multilayer Film [0070] The multilayer film 100, 200 may have a thickness of less than 180 pm. As described previously, it is desired to create multilayer films, which can meet the required mechanical properties while minimizing the thickness of the film. In embodiments, the multilayer film 100, 200 may have a thickness of less than 160 pm, less than 140 pm, less than 120 pm, less than 100 pm, less than 90 pm, from 70 pm to 180 pm, from 70 pm to 150 pm, from 70 pm to 125 pm, from 70 pm to 115 pm, from 70 pm to 105 pm, from 70 pm to 100 pm, from 70 pm to 95 pm, from 70 pm to 90 pm, from 80 pm to 180 pm, from 80 pm to 150 pm, from 80 pm to 125 pm, from 80 pm to 115 pm, from 80 pm to 105 pm, from 80 pm to 100 pm, from 80 pm to 90 pm, from 90 pm to 180 pm, from 90 pm to 150 pm, from 90 pm to 115 pm, from 90 pm to 105 pm, from 90 pm to 100 pm, or any subset thereof.

[0071] Still referring to FIG. 1 and FIG. 2, the first skin layer 102, 202 and/or the second skin layer 104, 204 may independently have a thickness of from 10 % to 30 % of a thickness of the multilayer film 100, 200. In embodiments, the first skin layer 102, 202 and/or the second skin layer 104, 204 may independently have a thickness of from 10 % to 25 %, from 10 % to 20 %, from 10 % to 15 %, from 15 % to 30 %, from 20 % to 30 %, from 15 % to 25 %, or any subset thereof of a thickness of the multilayer film 100, 200.

[0072] The first core layer 108, 208 and the third core layer 112, 212 may independently have a thickness of from 3 % to 45 %, from 3 % to 40 %, from 3 % to 35 %, from 3 % to 30 %, from 3 % to 25 %, from 3 % to 20 %, from 3 % to 15 %, from 3 % to 10 %, from 5 % to 45 %, from 10 % to 45 %, from 15 % to 45 %, from 20 % to 45 %, from 30 % to 45 %, from 5 % to 40 %, from 10 % to 35 %, from 15 % to 30 %, or any subset thereof of a thickness of the multilayer film 100, 200.

[0073] The second core layer 110, 210 may have a thickness of less than 15 % of a thickness of the multilayer film 100, 200. Without being limited by theory, it is believed that the performance of the multilayer film 100, 200 may be optimized when the second core layer 110, 210 is at its thinnest. However, due to manufacturing challenges and variability in layer thickness, it may not be possible to create an second core layer less than 3% of the thickness of the multilayer film 110, 210. In embodiments, the second core layer 110, 210 may have a thickness of less than or equal to 10 %, less than or equal to 5 %, from 3 % to 20 %, from 3 % to 15 %, from 3 % to 10 %, from 3 % to 7 %, from 3% to 5%, from 1 % to 20 %, from 5 % to 20 %, or any subset thereof of the thickness of the multilayer film 100, 200. In embodiments, the second core layer 110, 210 may have a thickness of from 3 % to 7 % of a thickness of the multilayer film 100, 200. [0074] Referring now to FIG. 2, the fourth core layer 214 and the fifth core layer 216 may independently have a thickness of from 3 % to 45 %, from 3 % to 40 %, from 3 % to 35 %, from 3 % to 30 %, from 3 % to 25 %, from 3 % to 20 %, from 3 % to 15 %, from 3 % to 10 %, from 5 % to 45 %, from 10 % to 45 %, from 15 % to 45 %, from 20 % to 45 %, from 30 % to 45 %, from 5 % to 40 %, from 10 % to 35 %, from 15 % to 30 %, or any subset thereof of a thickness of the multilayer film 100, 200.

[0075] Referring again to FIG. 1 and FIG. 2, the multilayer film 100, 200 may have a density of from 0.929 g/cc to 0.942 g/cc. In embodiments, the multilayer film 100, 200 may have a density of from 0.929 g/cc to 0.940 g/cc, from 0.929 g/cc to 0.9.35 g/cc, from 0.930 g/cc to 0.942 g/cc, from 0.935 g/cc to 0.942 g/cc, from 0.930 g/cc to 0.940 g/cc, from 0.932 g/cc to 0.938 g/cc or any subset thereof.

[0076] The multilayer film 100, 200 may have a normalized Dart Drop Impact Type A of at least 4.0 g/pm. In embodiments, the multilayer film 100, 200 may have a Dart Drop Impact Type A of at least 4.4 g/pm, at least 4.6 g/pm, at least 4.8 g/pm, at least 5.0 g/pm, from 4.0 g/pm to 6.0 g/pm, from 4.2 g/pm to 6.0 g/pm, from 4.4 g/pm to 6.0 g/pm or any subset thereof.

[0077] The multilayer film 100, 200 may have a Dart Drop Impact Type A of at least 400 g/pm, such as at least 425 g/pm, at least 450 g/pm, at least 500 g/pm, at least 600 g/pm, or any subset thereof.

[0078] The multilayer film 100, 200 may have a normalized Elmendorf Cross Direction Tear resistance of at least 16.6 gf/pm. In embodiments, the multilayer film 100, 200 may have an Elmendorf Cross Direction Tear resistance of at least 16.8 gf/pm, at least 17.0 gf/pm, at least 17.2 gf/pm, at least 17.4 gf/pm, at least 17.6 gf/pm, at least 17.8 gf/pm, at least 18.0 gf/pm, from 16.6 gf/pm to 20 gf/pm, or any subset thereof.

[0079] The multilayer film 100, 200 may have an Elmendorf Cross Direction Tear resistance of at least 1500 grams force (gf). In embodiments, the multilayer film 100, 200 may have an Elmendorf Cross Direction Tear resistance of at least 1600 gf, at least 1700 gf, at least 1800 gf, at least 1900 gf, at least 2000 gf, from 1500 gf to 3000 gf, from 1600 gf to 3000 gf, from 1700 gf to 3000 gf, from 1800 gf to 3000 gf, from 1900 gf to 3000 gf, from 2000 gf to 3000 gf, or any subset thereof.

[0080] The multilayer film 100, 200 may have a normalized Elmendorf Machine Direction Tear resistance of at least 8.8 gf/pm. In embodiments, the multilayer film 100, 200 may have an Elmendorf Machine Direction Tear resistance of at least 9.0 gf/pm, at least 9.2 gf/pm, at least 9.4 gf/pm, at least 9.6 gf/pm, at least 9.8 gf/pm, at least 10.0 gf/pm, from 8.8 gf/pm to 12 gf/pm, from 9.0 gf/pm to 12 gf/pm, from 9.2 gf/pm to 12 gf/pm, from 9.4 gf/pm to 12 gf/pm, or any subset thereof.

[0081] The multilayer film 100, 200 may have an Elmendorf Machine Direction Tear resistance of at least 800 gf, such as at least 825 gf, at least 850 gf, at least 900 gf, at least 1000 gf, at least 1100 gf, from 800 gf to 1500 gf, from 850 gf to 1500 gf, from 900 gf to 1500 gf, from 1000 gf to 1500 gf, or any subset thereof.

[0082] The multilayer film 100, 200 may have a high throughput creep of less than 50 %. In embodiments, the multilayer film 100, 200 may have a high throughput creep of less than 45 %, less than 40 %, less than 35 %, less than 30 %, less than 25 %, less than 20 %, less than 15 %, less than 10 %, less than 5 %, from 1 % to 50 %, from 1 % to 40 %, from 1 % to 30 %, from 1 % to 25 %, or any subset thereof.

[0083] It should be understood that the multilayer film 100 may comprise 5 or more layers. In embodiments, the multilayer film 100 may comprise more than 5 layers, such as 7, 9, or 11 layers. [0084] Multilayer films 100 disclosed herein can be produced using techniques known to those of skill in the art based on the teachings herein. For example, the multilayer film may be produced by film lamination and/or coextrusion. The formation of coextruded multilayer films 100 is known in the art and applicable to the present disclosure. Coextrusion systems for making multilayer films 100 employ at least two extruders feeding a common die assembly. The number of extruders is dependent upon the number of different materials or polymer. For example, a five-layer coextrusion may require up to five extruders although less may be used if two or more of the layers are made of the same materials or polymers.

[0085] In some embodiments, the multilayer film is a machine direction oriented film. In other embodiments, the multilayer film is a cast stretch film. In further embodiments, the multilayer is a stretch hood film.

[0086] Additives

[0087] It should be understood that any of the foregoing layers can further comprise one or more additives as known to those of skill in the art such as, for example, antioxidants, ultraviolet light stabilizers, thermal stabilizers, slip agents, antiblock agents, antistatic agents, pigments or colorants, processing aids, crosslinking catalysts, flame retardants, fillers and foaming agents. The layer may contain any amounts of such additives, such as from 0 wt. % to 10 wt. %, from 0 wt. % to 5 wt. %, from 0 wt. % to 1 wt. %, from 0 wt. % to 0.1 wt. %, from 0 wt. % to 0.001 wt. %, or any subset thereof, based on a weight of the layer.

[0088] Articles

[0089] Embodiments of the present disclosure also provide articles including any of the inventive multilayer fdms described herein. Examples of such articles can include wraps, packages, flexible packages, pouches, and sachets. Articles of the present disclosure can be formed from the multilayer fdms disclosed herein using techniques known to those of skill in the art in view of the teachings herein. Articles of the present disclosure may include a heavy-duty shipping sack comprising one or more multilayer fdms 100, 200.

TESTING METHODS

[0090] Density

[0091] Density is measured in accordance with ASTM D792, and expressed in grams/cm³ (g/cm³).

[0092] Melt Indices (b, I10, and I21

[0093] Melt Index (I2) is measured in accordance with ASTM D 1238-10 at 190 Celsius and 2.16 kg, Method B, and is expressed in grams eluted/10 minutes (g/10 min).

[0094] Melt Index (I10) is measured in accordance with ASTM D 1238-10 at 190 Celsius and 10 kg, Method B, and is expressed in grams eluted/10 minutes (g/10 min).

[0095] Melt Index (I21) is measured in accordance with ASTM D 1238-10 at 190 Celsius and 21.6 kg, Method B, and is expressed in grams eluted/10 minutes (g/10 min).

[0096] Improved .Comonomer Composition .Distribution (ICCD)

[0097] Improved method for comonomer content analysis (iCCD) was developed in 2015 (Cong and Parrott et al., W02017040127A1). iCCD test was performed with Crystallization Elution Fractionation instrumentation (CEF) (PolymerChar, Spain) equipped with IR-5 detector (PolymerChar, Spain) and two angle light scattering detector Model 2040 (Precision Detectors, currently Agilent Technologies). A guard column packed with 20-27 micron glass (MoSCi Corporation, USA) in a 5 cm or 10 cm (length)Xl/4” (ID) stainless was installed just before IR-5 detector in the detector oven. Ortho-dichlorobenzene (ODCB, 99% anhydrous grade or technical grade) was used. Silica gel 40 (particle size 0.2-0.5 mm, catalogue number 10181-3) from EMD Chemicals was obtained (can be used to dry ODCB solvent before). Dried silica was packed into three emptied HT-GPC columns to further purify ODCB as eluent. The CEF instrument is equipped with an auto sampler with N2 purging capability. ODCB is sparged with dried nitrogen (N2) for one hour before use. Sample preparation was done with auto sampler at 4 mg/ml (unless otherwise specified) under shaking at 160 °C for 1 hour. The injection volume was 300 pl. The temperature profile of iCCD was: crystallization at 3°C/min from 105 °C to 30 °C, the thermal equilibrium at 30 °C for 2 minute (including Soluble Fraction Elution Time being set as 2 minutes), elution at 3 °C/min from 30 °C to 140 °C. The flow rate during crystallization is 0.0 ml/min. The flow rate during elution is 0.50 ml/min. The data was collected at one data point/second.

[0098] The iCCD column was packed with gold coated nickel particles (Bright 7GNM8-NiS, Nippon Chemical Industrial Co.) in a 15 cm (length)Xl/4” (ID) stainless tubing. The column packing and conditioning were with a slurry method according to the reference (Cong, R.; Parrott, A.; Hollis, C.; Cheatham, M. W02017040127A1). The final pressure with TCB slurry packing was 150 Bars.

[0099] Column temperature calibration was performed by using a mixture of the Reference Material Einear homopolymer polyethylene (having zero comonomer content, Melt index (I2) of 1.0, polydispersity M_w/M_n approximately 2.6 by conventional gel permeation chromatography, 1.0 mg/ml) and Eicosane (2 mg/ml) in ODCB. iCCD temperature calibration consisted of four steps: (1) Calculating the delay volume defined as the temperature offset between the measured peak elution temperature of Eicosane minus 30.00° C; (2) Subtracting the temperature offset of the elution temperature from iCCD raw temperature data. It is noted that this temperature offset is a function of experimental conditions, such as elution temperature, elution flow rate, etc.; (3) Creating a linear calibration line transforming the elution temperature across a range of 30.00° C and 140.00° C so that the linear homopolymer polyethylene reference had a peak temperature at 101.0°C, and Eicosane had a peak temperature of 30.0° C; (4) For the soluble fraction measured isothermally at 30° C, the elution temperature below 30.0° C is extrapolated linearly by using the elution heating rate of 3° C/min according to the reference (Cerk and Cong et al., US9,688,795).

[0100] The comonomer content versus elution temperature of iCCD was constructed by using 12 reference materials (ethylene homopolymer and ethyl ene-octene random copolymer made with single site metallocene catalyst, having ethylene equivalent weight average molecular weight ranging from 35,000 to 128,000). All of these reference materials were analyzed same way as specified previously at 4 mg/mL. The reported elution peak temperatures followed the figure of octene mole% versus elution temperature of iCCD at R² of 0.978.

[0101] Molecular weight of polymer and the molecular weight of the polymer fractions was determined directly from LS detector (90 degree angle) and concentration detector (IR-5) according Rayleigh-Gans-Debys approximation (Striegel and Yau, Modern Size Exclusion Liquid Chromatogram, Page 242 and Page 263) by assuming the form factor of 1 and all the virial coefficients equal to zero. Integration windows are set to integrate all the chromatograms in the elution temperature (temperature calibration is specified above) range from 23.0 to 120 °C.

[0102] The calculation of Molecular Weight (Mw) from iCCD includes the following steps: (1) Measuring the interdetector offset. The offset is defined as the geometric volume offset between LS with respect to concentration detector. It is calculated as the difference in the elution volume (mL) of polymer peak between concentration detector and LS chromatograms. It is converted to the temperature offset by using elution thermal rate and elution flow rate. A linear high-density polyethylene (having zero comonomer content, Melt index (L) of 1.0, polydispersity M_w/M_n approximately 2.6 by conventional gel permeation chromatography) is used. Same experimental conditions as the normal iCCD method above are used except the following parameters: crystallization at 10°C/min from 140°C to 137°C, the thermal equilibrium at 137°C for 1 minute as Soluble Fraction Elution Time, soluble fraction (SF) time of 7 minutes, elution at 3°C/min from 137°C to 142°C. The flow rate during crystallization is 0.0 ml/min. The flow rate during elution is 0.80 ml/min. Sample concentration is l.Omg/ml. (2) Each LS datapoint in LS chromatogram is shifted to correct for the interdetector offset before integration. (3) Baseline subtracted LS and concentration chromatograms are integrated for the whole eluting temperature range of the Step (1). The MW detector constant is calculated by using a known MW HDPE sample in the range of 100,000 to 140,000Mw and the area ratio of the LS and concentration integrated signals. (4) Mw of the polymer was calculated by using the ratio of integrated light scattering detector (90 degree angle) to the concentration detector and using the MW detector constant.

[0103] Conyentipnal GPC (M_w,. M_n, M_wZM_n)

[0104] The chromatographic system consisted of a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with an internal IR5 infra-red detector (IR5) coupled to a Precision Detectors (Now Agilent Technologies) 2-angle laser light scattering (LS) detector Model 2040. For all Light scattering measurements, the 15 degree angle is used for measurement purposes. The autosampler oven compartment was set at 160° Celsius and the column compartment was set at 150° Celsius. The columns used were 4 Agilent “Mixed A” 30cm 20-micron linear mixed-bed columns. The chromatographic solvent used was 1,2,4 trichlorobenzene and contained 200 ppm of butylated hydroxytoluene (BHT). The solvent source was nitrogen sparged. The injection volume used was 200 microliters and the flow rate was 1.0 milliliters/minute.

[0105] Calibration of the GPC column set was performed with 21 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000 and were arranged in 6 “cocktail” mixtures with at least a decade of separation between individual molecular weights. The standards were purchased from Agilent Technologies. The polystyrene standards were prepared at 0.025 grams in 50 milliliters of solvent for molecular weights equal to or greater than 1,000,000, and 0.05 grams in 50 milliliters of solvent for molecular weights less than 1,000,000. The polystyrene standards were dissolved at 80 degrees Celsius with gentle agitation for 30 minutes. The polystyrene standard peak molecular weights were converted to polyethylene molecular weights using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym. Eet., 6, 621 (1968)).:

where M is the molecular weight, A has a value of 0.4315 and B is equal to 1.0

[0106] A fifth order polynomial was used to fit the respective polyethylene-equivalent calibration points. A small adjustment to A (from approximately 0.415 to 0.44) was made to correct for column resolution and band-broadening effects such that NIST standard NBS 1475 is obtained at 52,000Mw.

[0107] The total plate count of the GPC column set was performed with Eicosane (prepared at 0.04 g in 50 milliliters of TCB and dissolved for 20 minutes with gentle agitation.) The plate count (Equation 2) and symmetry (Equation 3) were measured on a 200 microliter injection according to the following equations:

where RV is the retention volume in milliliters, the peak width is in milliliters, the peak max is the maximum height of the peak, and A height is A height of the peak maximum.

where RV is the retention volume in milliliters and the peak width is in milliliters, Peak max is the maximum position of the peak, one tenth height is 1/10 height of the peak maximum, and where rear peak refers to the peak tail at later retention volumes than the peak max and where front peak refers to the peak front at earlier retention volumes than the peak max. The plate count for the chromatographic system should be greater than 24,000 and symmetry should be between 0.98 and 1.22.

[0108] Samples were prepared in a semi-automatic manner with the PolymerChar “Instrument Control” Software, wherein the samples were weight-targeted at 2 mg/ml, and the solvent (contained 200ppm BHT) was added to a pre nitrogen-sparged septa-capped vial, via the PolymerChar high temperature autosampler. The samples were dissolved for 2 hours at 160° Celsius under “low speed” shaking.

[0109] The calculations of Mn(GPC), MW(GPC), and MZ(GPC) were based on GPC results using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph according to Equations 4-6, using PolymerChar GPCOne™ software, the baseline-subtracted IR chromatogram at each equally-spaced data collection point (i), and the polyethylene equivalent molecular weight obtained from the narrow standard calibration curve for the point (i) from Equation 1 .

[0110] In order to monitor the deviations over time, a flowrate marker (decane) was introduced into each sample via a micropump controlled with the PolymerChar GPC-IR system. This flowrate marker (FM) was used to linearly correct the pump flowrate (Flowrate(nominal)) for each sample by RV alignment of the respective decane peak within the sample (RV(FM Sample)) to that of the decane peak within the narrow standards calibration (RV(FM Calibrated)). Any changes in the time of the decane marker peak are then assumed to be related to a linear-shift in flowrate (Flowrate(effective)) for the entire run. To facilitate the highest accuracy of a RV measurement of the flow marker peak, a leastsquares fitting routine is used to fit the peak of the flow marker concentration chromatogram to a quadratic equation. The first derivative of the quadratic equation is then used to solve for the true peak position. After calibrating the system based on a flow marker peak, the effective flowrate (with respect to the narrow standards calibration) is calculated as Equation 7. Processing of the flow marker peak was done via the PolymerChar GPCOne™ Software. Acceptable flowrate correction is such that the effective flowrate should be within +/-2% of the nominal flowrate.

Flowrate(effective) = Flowrate(nominal) * (RV(FM Calibrated) / RV(FM Sample)) (EQ7) [0111] The Systematic Approach for the determination of multi-detector offsets is done in a manner consistent with that published by Balke, Mourey, et. al. (Mourey and Balke, Chromatography Polym. Chpt 12, (1992)) (Balke, Thitiratsakul, Tew, Cheung, Mourey, Chromatography Polym. Chpt 13, (1992)), optimizing triple detector log (MW and IV) results from a broad homopolymer polyethylene standard (Mw/Mn > 3) to the narrow standard column calibration results from the narrow standards calibration curve using PolymerChar GPCOne™ Software.

[0112] The absolute molecular weight data was obtained in a manner consistent with that published by Zimm (Zimm, B.H., J. Chem. Phys., 16, 1099 (1948)) and Kratochvil (Kratochvil, P., Classical Eight Scattering from Polymer Solutions, Elsevier, Oxford, NY (1987)) using PolymerChar GPCOne™ software. The overall injected concentration, used in the determination of the molecular weight, was obtained from the mass detector area and the mass detector constant, derived from a suitable linear polyethylene homopolymer, or one of the polyethylene standards of known weight-average molecular weight. The calculated molecular weights (using GPCOne™) were obtained using a light scattering constant, derived from one or more of the polyethylene standards mentioned below, and a refractive index concentration coefficient, dn/dc, of 0.104. Generally, the mass detector response (IR5) and the light scattering constant (determined using GPCOne™) should be determined from a linear standard with a molecular weight in excess of about 50,000 g/mole. Other respective moments, Mn(Abs) and Mz(Abs) are be calculated according to equations 8-9 as follows:

[0113] DSC Method - Heat of Fusion

[0114] Differential scanning calorimetry is a common technique that can be used to examine the melting and crystallization of semi-crystalline polymers. General principles of DSC measurements and applications of DSC to studying semi-crystalline polymers are described in standard texts (e.g., E. A. Turi, ed., Thermal Characterization of Polymeric Materials, Academic Press, 1981).

[0115] The Heat of Fusion is determined using DSC from TA Instruments, Inc. The test is conducted in reference to ASTM standard D3428. The calibration is performed by preparing 2-3 mg of indium and placing it in a T-zero aluminum pan. The pan is then loaded into the DSC instrument and subjected to the following heating program cycle: 1) equilibrate test chamber at 180 °C, 2) hold temperature at 180 °C for 1 min., 3) ramp temperature down to 130 °C at 10 °C/min., 4) hold temperature at 130 °C for 3 min., and 5) ramp temperature at 10 °C/min. to 180 °C. Once completed, the last heat curve conducted in step 5 is analyzed to determine the melting temperature of the indium sample. The DSC is considered to be working in compliance should the melting temperature be within a 0.5 °C tolerance of 156.6 °C.

[0116] For sample testing, the polymer samples are first pressed into a thin film at a temperature of 190 °C. About 4 to 5 mg of sample is weighed out and placed in the DSC pan. The lid is crimped on the pan to ensure a closed atmosphere. The sample pan is placed in the DSC cell and is equilibrated at 180 °C. The sample is kept at this temperature for 5 minutes. Then the sample is cooled at a rate of 10 °C/min to -90 °C and kept isothermally at that temperature for 5 minutes. Subsequently, the sample is heated at a rate of 10 °C/min to 150 °C (to ensure complete melting); this step is designated as the 2nd heating curve. The resulting enthalpy curves are analyzed for peak melt temperature, onset and peak crystallization temperatures, and the heat of fusion (also known as heat of melting), AHf. The heat of fusion, in Joules/gram, is measured from the 2nd heating curve by performing a linear integration of the melting endotherm in accordance to the baseline

[0117] Dart

[0118] The Dart Drop test follows ASTM DI 709 Method A and provides a measure of the energy needed to cause a plastic fdm to fail under specified conditions of impact by a free falling dart. The test result is the energy, expressed in terms of the weight of the missile falling from a specified height, which would result in the failure of 50% of the specimens tested. The film sample is conditioned for at least 40 hours at 23 °C (± 2 °C) and 50% R.H (± 10 %) before the test which is conducted at 23 °C (± 2 °C) and 50% R.H (± 10 %). Method-A, which uses a 1.5” diameter dart head and 26” drop height, was employed for the current film samples. The material of construction of Dart head is Aluminum. The sample thickness is measured at the sample center and the sample is then clamped by an annular specimen holder with an inside diameter of 5”. The dart is loaded above the center of the sample and released by either a pneumatic or an electromagnetic mechanism. The Dart is loaded with a starting weight which is subsequently either increased or decreased by a chosen weight depending on pass/fail from each drop. About 20-25 specimens are typically used for the drop experiments. Finally, a staircase method as per ASTM D1709 is employed to calculate the ‘Dart’ value based on the collection of pass/fail data, the starting weight and the weight increment.

[0119] Elmendorf Tear Resistance

[0120] Average Elmendorf Tear Resistance is measured in machine direction (MD) and cross-machine direction (CD) in accordance with ASTM D1922. [0121] High Throughput Creep

[0122] High Throughput Creep is determined in accordance with the ISO 899 standard.

ASPECTS

[0123] According to a first aspect, a multilayer film may comprise a first skin layer, a second skin layer, and a core positioned between the first skin layer and the second skin layer, wherein: the first skin layer and the second skin layer independently comprise linear low density polyethylene (EEDPE) resin; the core comprises a first core layer, a second core layer, and a third core layer; the first core layer and the third core layer may independently comprise high density polyethylene (HDPE), linear low density polyethylene (EEDPE), or a combination of these; the second core layer may comprise an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer; the thickness of the second core layer may be less than 15 % of the thickness of the multilayer film; and at least one of the core layers comprises high density polyethylene (HDPE).

[0124] According to a second aspect, in conjunction with the first aspect, the second core layer may be positioned between the first core layer and the third core layer.

[0125] According to a third aspect, in conjunction with the first or second aspects, the second core layer may further comprise calcium carbonate.

[0126] According to a fourth aspect, in conjunction with any one of aspects 1-3, the multilayer film may comprise at least 30 wt. % of HDPE, on the basis of the total polymer weight of the multilayer film.

[0127] According to a fifth aspect, in conjunction with any one of aspects 1-4, the second core layer may comprise an ethylene-based copolymer selected from the group consisting of ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, and ethylene/methyl acrylate copolymer.

[0128] According to a sixth aspect, in conjunction with any one of aspects 1-5, the first skin layer, the second skin layer, or both may further comprise low-density polyethylene (LDPE).

[0129] According to a seventh aspect, in conjunction with any one of aspects 1-6, the core may further comprise: a fourth core layer positioned between the first skin layer and the first core layer, and a fifth core layer positioned between the third core layer and the second skin layer. [0130] According to an eighth aspect, in conjunction with any one of aspects 1-7, the fourth core layer and the fifth core layer may each independently comprise HDPE, LLDPE, or combinations thereof.

[0131] According to a ninth aspect, in conjunction with any one of aspects 1-8, the second core layer may have a thickness of less than or equal to 10 % of a thickness of the multilayer film.

[0132] According to a tenth aspect, in conjunction with any one of aspects 1-8, 10. the multilayer film may have a thickness of less than 180 pm.

[0133] According to an eleventh aspect, in conjunction with any one of aspects 1-10, the multilayer film may have a normalized Dart Drop Impact Type A of at least 4.4 g/pm.

[0134] According to a twelfth aspect, in conjunction with any one of aspects 1-11, the multilayer film may have a normalized Elmendorf Cross Direction Tear resistance of at least 16.6 gf/pm.

[0135] According to a thirteenth aspect, in conjunction with any one of aspects 1-12, the multilayer film may have a normalized Elmendorf Machine Direction Tear resistance of at least 8.8 gf/pm.

[0136] According to a fourteenth aspect, in conjunction with any one of aspects 1-13, the multilayer film may have a high throughput creep of less than 50 %.

[0137] According to a fifteenth aspect, in conjunction with any one of aspects 1-14, the second core layer may be the central layer, the second core layer may be positioned between the first core layer and the third core layer, the multilayer film may have a density of from 0.929 g/cc to 0.942 g/cc, the first skin layer, the second skin layer, or both may further comprise low-density polyethylene (EDPE), the second core layer may have a thickness less than or equal to 10 % of a thickness of the multilayer film, the multilayer film may have a thickness of less than or equal to 110 pm, the multilayer film may have a Dart Drop Impact Type A of at least 4.4 g/pm, the multilayer film may have an Elmendorf Cross Direction Tear resistance of at least 16.6 gf/pm, and the multilayer film may have an Elmendorf Machine Direction Tear resistance of at least 8.8 gf/pm.

EXAMPLES

[0138] The following examples are provided to illustrate embodiments described in this disclosure and are not intended to limit the scope of this disclosure or its appended claims.

[0139] .Materials [0140] INNATE™ ST50 (also referred to herein as “ST50”), a linear low-density polyethylene having a density of 0.918 g/cm³ and melt index (I2) of 0.85 g/10 min and commercially available from Dow Inc., (Midland, MI). INNATE™ ST50 is an ethylene-based polymer as that term is defined herein.

[0141] INNATE™ ST70 (also referred to herein as “ST70”), a linear low-density polyethylene having a density of 0.926 g/cm³ and melt index (I2) of 0.85 g/10 min and commercially available from Dow Inc., (Midland, MI). INNATE™ ST70 is an ethylene-based polymer as that term is defined herein.

[0142] INNATE™ ST100 (also referred to herein as “ST100”), a linear low-density polyethylene having a density of 0.928 g/cm³ and melt index (I2) of 0.85 g/10 min and commercially available from Dow Inc., (Midland, MI). INNATE™ ST100 is an ethylene -based polymer as that term is defined herein.

[0143] ELITE™ 5400, a linear low-density polyethylene having a density of 0.916 g/cm³ and melt index (I2) of 1.0 g/10 min and commercially available from Dow Inc., (Midland, MI). ELITE™ 5400 is an ethylene-based polymer as that term is defined herein.

[0144] DOWLEX™ GM 8090 (also referred to herein as “GM 8090”) is a linear low-density polyethylene commercially available from Dow Inc., (Midland, MI). DOWLEX™ GM 8090 has a density of 0.916 g/cm³ and melt index (I2) of 1.0 g/10 min. DOWLEX™ GM 8090 is an ethylene-based polymer as that term is defined herein.

[0145] AGILITY™ AT 1604 is a low-density polyethylene having a density of 0.921 g/cm³ and a melt index (I2) of 0.25 g/10 min and commercially available from Dow Inc., (Midland, MI). AGILITY™ AT 1604 is an ethylene-based polymer as that term is defined herein.

[0146] UNIV AL™ DMDA 6400 (also referred to herein as “DMDA 6400”) is a high-density polyethylene having a density of 0.961 g/cm³, a melt index (I2) of 0.80 g/ 10 min, and a melt index (I21) of 57 g/10 min and commercially available from Dow Inc., (Midland, MI). UNIV AL™ DMDA 6400 is an ethylene-based polymer as that term is defined herein.

[0147] ELVALOY™ AC 3117 (also referred to herein as “EA”) is an ethylene-acrylate copolymer (83 % ethylene and 17 % butyl acrylate) having a density of 0.924 g/cm³ and a melt index (I2) of 1.5 g/10 min and commercially available from Dow Inc., (Midland, MI). ELVALOY™ AC 3117 is an ethylene-acrylate copolymer as that term is defined herein. [0148] Some examples use a blend of ELVALOY™ AC 3117 and CaCCh (also referred to herein as "EA+CaCCh"). The blend comprises about 42 wt. % of calcium carbonate, with the balance of the ethylene-acrylate copolymer, based on the total weight of the layer.

[0149] XUS 39003.00 (also referred to herein as “EP”) is an ethylene-propylene copolymer commercially available from Dow Inc. (Midland, MI). EP comprises 27.1 wt.% propylene comonomer and 72.9 wt.% ethylene monomer and has a density of 0.867 g/cm³, a melt index (E) of 0.90 g/10 min, a I10/I2 of 10.82, a heat of fusion of 50.24 J/g, and a Mw/Mn of 3.98. EP has a proportion of inversely inserted propylene units based on 2, 1 insertion of 0.8 wt. %, where weight percent is based on total weight of EP. EP is an ethylene-based polymer as that term is defined herein.

[0150] Some examples use a blend of XUS 39003.0 (“EP”) and Calcium Carbonate (also referred to herein as “EP+CaCOs”). The blend comprises about 42 wt. % of calcium carbonate, with the balance of the ethylene-propylene copolymer, based on the total weight of the layer.

[0151] ELITE™ 5960G1 (also referred to herein as “5960”) is a high density polyethylene (HDPE) commercially available from Dow Inc. (Midland, MI). 5960 has a melt index (I2) of 8.5 g/10 min and density of 0.962 g/ cm³. 5960 is an ethylene-based polymer as that term is defined herein.

[0152] 5 -Lay er Films

[0153] A series of 5 layer, multilayer films were prepared by coextrusion on a Tarragona Collin coextrusion line. Each layer was extruded on a separate extruder. Unless otherwise specified, the resulting films had a thickness of about 100 pm.

[0154] Table 1 gives the compositions of some 5 -layer multilayer films of the present disclosure.

Table 1 : 5-Layer Film Compositions

[0155] Table 2 shows some mechanical properties of the five layer films described in Table 1.

Table 2: 5-Layer Film Properties

[0156] As is shown in Table 2, the comparative film CE-A has sufficient dart (specification is

>400g), and creep (specification is <50%) performance. However, both MD-Tear and CD-Tear are insufficient (specification is >800g and >1500g respectively). It should be noted that CE-A is 60 wt. % HDPE, while EX-1 to EX-11 each include 30 wt. % of HDPE.

[0157] The examples of the present disclosure which include the second core layer, show significant improvements in properties, especially when the density is above 0.934 g/c. The extremely high dart and tear performance would also allow for increased HDPE content (which would improve creep performance at the expense of dart and tear). This is the approach followed to optimize optimizing the 7-layer structures described below.

[0158] When looking at different components for the second core layer, EA+CaCCb provides most of the best mechanics due to the synergy between the ethylene-acrylate copolymer and the calcium carbonate. However, the embodiments without calcium carbonate provide improved creep.

[0159] As can be seen by comparing EX-1 with EX-9 and EX-20, the use of 5% high melt strength LDPE, such as AGILITY AT 1604, in the skin layers improves creep without negatively affecting the other properties (dart and tear). Additionally, there is an even greater improvement in creep when only one skin layer comprises LDPE. Further optimization is possible by choosing the best skin layers, or increasing the HDPE content also through blends in the core layers.

[0160] 7-Layer Films

[0161] A series of 7 layer, multilayer fdms were prepared by coextrusion on a Tarragona Collin coextrusion line. Each layer was extruded on a separate extruder. Unless otherwise specified, the resulting films had a thickness of about 100 pm. Details of the films are included below in Table 3.

Table 3

[0162] Table 4-A provides the material properties of some of the embodiments of the 7-layer films with provides the second core layer in the center.

Table 4-A

[0163] As can be seen from Table 4- A, the embodiments of the present disclosure show excellent mechanical properties. This is true for both the ethylene-acrylate copolymer embodiments and ethylene-propylene copolymer embodiments. Additionally, when the thickness of the second core layer is increased from 5 % to 10 %, the overall enhancement in properties is less than at 5 % but it is still significant. As can be seen by comparing EX- 18

[0164] Table 4-B provides the material properties of some of the embodiments of the 7-layer films where the second core layer in not in the center. In EX- 19, the second core layer is in layer B. In EX-20, the second core layer is in layer C.

Table 4-B

[0165] As can be seen by comparing EX- 19 and EX-20 with the other examples the mechanical properties are better when the second core layer is the center layer, relative to when the second core layer is one of the other core layers. However, there is still a significant improvement in mechanical properties relative to the absence of a second core layer. [0166] Table 4-C provides details of an embodiment of Example 14 which has been down gauged from 100 pm to 95 pm and labeled EX- 14(b). The relative thickness of each layer remains the same as is shown in Table 3.

[0167] Table 3: 7E Down gauged to 95 pm

Table 4-C

[0168] When the fdm of EX- 14 is downgauged from 100 pm to 95 pm, the resultant fdm still exceeds the required parameters for an HDSS fdm.

[0169] While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.

Claims

1. A multilayer film comprising a first skin layer, a second skin layer, and a core positioned between the first skin layer and the second skin layer, wherein: the first skin layer and the second skin layer independently comprise linear low density polyethylene (LLDPE) resin; the core comprises a first core layer, a second core layer, and a third core layer; the first core layer and the third core layer independently comprise high density polyethylene (HDPE), linear low density polyethylene (LLDPE), or a combination of these; the second core layer comprises an ethylene-based copolymer selected from the group consisting of ethylene/propylene copolymer, ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer, and ethylene/vinyl acetate copolymer; the thickness of the second core layer is less than 15 % of the thickness of the multilayer fdm; and at least one of the core layers comprise high density polyethylene (HDPE).

2. The multilayer fdm of claim 1, wherein the second core layer is positioned between the first core layer and the third core layer.

3. The multilayer film of any preceding claim, wherein the second core layer further comprises calcium carbonate.

4. The multilayer film of any preceding claim, wherein the multilayer film comprises at least 30 wt. % of HDPE, on the basis of the total polymer weight of the multilayer film.

5. The multilayer film of any preceding claim, wherein the second core layer comprises an ethylene-based copolymer selected from the group consisting of ethylene/butyl acrylate copolymer, ethylene/ethyl acrylate copolymer, and ethylene/methyl acrylate copolymer.

6. The multilayer film of any preceding claim, wherein the first skin layer, the second skin layer, or both further comprise low-density polyethylene (LDPE).

7. The multilayer film of any preceding claim, wherein the core further comprises: a fourth core layer positioned between the first skin layer and the first core layer, and a fifth core layer positioned between the third core layer and the second skin layer.

8. The multilayer film of claim 7, wherein the fourth core layer and the fifth core layer each independently comprise HDPE, LLDPE, or combinations thereof.

9. The multilayer film of any preceding claim, wherein the second core layer has a thickness of less than or equal to 10 % of a thickness of the multilayer film.

10. The multilayer film of any preceding claim, wherein the multilayer film has a thickness of less than 180 pm.

11. The multilayer film of any preceding claim, wherein the multilayer film has a Dart Drop Impact Type A of at least 4.4 g/pm.

12. The multilayer film of any preceding claim, wherein the multilayer film has an Elmendorf Cross Direction Tear resistance of at least 16.6 gf/pm.

13. The multilayer film of any preceding claim, wherein the multilayer film has an Elmendorf Machine Direction Tear resistance of at least 8.8 gf/pm.

14. The multilayer film of any preceding claim, wherein the multilayer film has a high throughput creep of less than 50 %.

15. The multilayer film of any preceding claim, wherein: the second core layer is the central layer, the second core layer is positioned between the first core layer and the third core layer, the multilayer film has a density of from 0.929 g/cc to 0.942 g/cc, the first skin layer, the second skin layer, or both further comprise low-density polyethylene (EDPE), the second core layer has a thickness less than or equal to 10 % of a thickness of the multilayer film, the multilayer film has a thickness of less than or equal to 110 pm, the multilayer film has a Dart Drop Impact Type A of at least 4.4 g/pm, the multilayer film has an Elmendorf Cross Direction Tear resistance of at least 16.6 gf/pm, and the multilayer film has an Elmendorf Machine Direction Tear resistance of at least

8.8 gf/pm.