Multilayer films containing ethylene-based polymers

Abstract

A multilayer film comprising an ethylene-based polymer is provided. The multilayer film can be fully compatible with polyethylene recycling streams. The multilayer film comprises a first outer layer, a second outer layer, and a core, the core comprising a first core layer comprising an ethylene-propylene copolymer. The multilayer film of the present invention can exhibit improved, maintained, or desirable properties, such as high tear resistance, compared to existing multilayer film structures that are not fully compatible with polyethylene recycling streams.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to multilayer films, and specifically to multilayer films comprising ethylene-based polymers.

[0002] Introduction Multilayer films incorporating various materials including polypropylene, polyamide, and polyethylene terephthalate are widely used in industrial and consumer products. Such films used in industrial and consumer products often require sufficient tear resistance to avoid the film being damaged during the film packaging process, for example, on a pallet. Although the combination of layers and materials can enable good performance of the film, such multilayer films can be difficult, if not impossible, to recycle together due to different types of materials that are not compatible with each other for recycling. As the demand for sustainable and recyclable materials continues to rise, there remains a need for multilayer films that are more easily recycled and have comparable or improved performance characteristics, such as tear resistance. Summary of the Invention

[0003] The present disclosure satisfies one or more of the above-mentioned needs by providing a multilayer film that exhibits comparable or desirable tear resistance and includes a recycle-compatible ethylene-based polymer. The multilayer film can be fully recycle-compatible in polyethylene recycle streams, and the tear resistance performance of the multilayer film of the present invention can be comparable to or better than other multilayer films that do not include the recycle-compatible polymer.

[0004] Disclosed herein is a multilayer film. In one embodiment, the multilayer film includes a first outer layer, a second outer layer, and a core, the core includes one or more core layers, the core layer being disposed between the first outer layer and the second outer layer, the core includes 100 wt. % ethylene-based polymer, based on the total polymer weight of the core, the first core layer includes an ethylene-propylene copolymer including 60-95 wt. % ethylene monomer and 5-40 wt. % propylene comonomer, and the ethylene-propylene copolymer has the following properties: 0.865-0.920 g / cm 3 %, a melt index (I2) of at least 0.5 g / 10 min, and a molecular weight distribution (Mw / Mn) of 3.0 to 5.0.

[0005] These and other embodiments are described in greater detail in the Detailed Description. [Brief description of the drawings]

[0006] [Figure 1] 1 is an ICCD elution profile for Poly.2, a commercially available ethylene-propylene copolymer described below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Aspects of the disclosed multilayer film are described in more detail below. The multilayer film can have a wide variety of applications, including cast stretch films, blown films, oriented films, stretch food films, etc. However, the disclosure should not be construed as limiting the embodiments described below, as the disclosure is an exemplary implementation of the embodiments described herein.

[0008] As used herein, the term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. Thus, the generic term polymer encompasses the terms homopolymer (used to refer to a polymer prepared from only one type of monomer) and copolymer. Trace amounts of impurities (e.g., catalyst residues) may be incorporated and / or present in the polymer. The polymer may be a single polymer, a polymer blend, or a polymer mixture, including a mixture of polymers formed in situ during polymerization.

[0009] As used herein, the term "copolymer" refers to a polymer formed by the polymerization reaction of at least two structurally different monomers. The term "copolymer" includes terpolymers. For example, an ethylene copolymer, such as an ethylene-propylene copolymer, can include at least two structurally different monomers (e.g., an ethylene-propylene copolymer can include at least copolymerized units of an ethylene monomer and a propylene monomer), and can optionally include additional monomers or functional materials or modifiers, such as acid, acrylate, or anhydride functional groups. In other words, the copolymers described herein include at least two structurally different monomers, and while the copolymers can consist of only two structurally different monomers, they do not necessarily consist of only two structurally different monomers and can include additional monomers or functional materials or modifiers.

[0010] As used herein, the term "polyethylene" or "ethylene-based polymer" shall mean a polymer that contains a majority (greater than 50% by weight) of units derived from ethylene monomer. This includes polyethylene homopolymers and copolymers. Unless otherwise specified, the ethylene copolymers disclosed herein (e.g., the ethylene-propylene copolymers described herein) are ethylene-based polymers.

[0011] Common forms of polyethylene known in the art include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ultra low density polyethylene (ULDPE), very low density polyethylene (VLDPE), single-site catalyzed linear low density polyethylene (m-LLDPE), including both linear and substantially linear low density resins, ethylene-based plastomers (POP) and ethylene-based elastomers (POE), medium density polyethylene (MDPE), and high density polyethylene (HDPE). These polyethylene materials are generally well known in the art. However, the following description may be helpful in understanding the differences between some of these different polyethylene resins.

[0012] The term "LDPE", which may also be referred to as "high pressure ethylene polymer", or "highly branched polyethylene", is defined to mean that the polymer is partially or fully homopolymerized or copolymerized in an autoclave or tubular reactor at pressures in excess of 14,500 psi (100 MPa) using a free radical initiator, such as peroxide (see, for example, U.S. Pat. No. 4,599,392, incorporated herein by reference). LDPE resins typically have a viscosity of 0.916 to 0.935 g / cm. 3 The density is in the range of

[0013] The term "LLDPE" includes both resins made using traditional Ziegler-Natta catalyst systems and chromium-based catalysts, as well as single-site catalysts, including, but not limited to, mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts and polyaryloxy ether catalysts (typically referred to as bisphenylphenoxy), and includes linear, substantially linear, or heterogeneous polyethylene copolymers or homopolymers. LLDPE contains less long chain branching than LDPE and includes substantially linear ethylene polymers as further defined in U.S. Patent Nos. 5,272,236, 5,278,272, 5,582,923, and 5,733,155, homogeneously branched linear ethylene polymer compositions such as those in U.S. Patent No. 3,645,992, heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Patent No. 4,076,698, and / or blends thereof (such as those disclosed in U.S. Patent Nos. 3,914,342 or 5,854,045). LLDPE may be made via gas phase, solution phase, or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

[0014] The term "MDPE" means 0.926 to 0.935 g / cm 3 "MDPE" refers to polyethylene having a density of greater than 2.5, typically produced using chromium or Ziegler-Natta catalysts, or using single-site catalysts, including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts, and polyaryloxy ether catalysts (typically referred to as bisphenylphenoxy), and typically has a molecular weight distribution ("MWD") greater than 2.5.

[0015] The term "HDPE" refers to poly(ethylene glycol) having a viscosity of about 0.935 g / cm, typically prepared using single-site catalysts including, but not limited to, Ziegler-Natta, chromium, or substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts, and polyaryloxy ether catalysts (typically referred to as bisphenylphenoxy). 3 Super ~ maximum approx. 0.980g / cm 3 It refers to polyethylene having a density of

[0016] The term "ULDPE" refers to poly(ethylene glycol) copolymers (ULDPE) having a viscosity of 0.855 to 0.912 g / cm, typically prepared using single-site catalysts including, but not limited to, Ziegler-Natta, chromium, or substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocenes), constrained geometry catalysts, phosphinimine catalysts, and polyaryloxy ether catalysts (typically referred to as bisphenylphenoxy). 3 ULDPE refers to polyethylene having a density of 1000 to 2000 mm. ULDPE includes, but is not limited to, polyethylene (ethylene based) plastomers and polyethylene (ethylene based) elastomers.

[0017] As used herein, the term "core layer" refers to a non-skin or non-outer layer of a multilayer film. The core layer is an inner layer of a multilayer film, i.e., a layer located between two outer layers. In one embodiment, the core layer is a non-outer layer of a three-layer film including a first outer layer and a second outer layer. The entire core layer, i.e., one or more, of the multilayer film of the present invention constitutes the "core" of the film.

[0018] The terms "comprising," "including," "having," and their derivatives are not intended to exclude the presence of any additional components, steps, or procedures, whether or not they are specifically disclosed. For the avoidance of any doubt, all compositions claimed through the use of the term "comprising" may include any additional additives, adjuvants, or compounds, whether polymeric or otherwise, unless otherwise stated to the contrary. In contrast, the term "consisting essentially of" excludes from the scope of any succeeding description any other component, step, or procedure, except those that are not essential to operability. The term "consisting of" excludes any component, step, or procedure not specifically delineated or listed.

[0019] Disclosed herein is a multilayer film. In some embodiments, the multilayer film can be an oriented film that is oriented in the machine direction and / or the transverse direction. In some embodiments, the multilayer film is a blown film. In some embodiments, the multilayer film is a cast film. In some embodiments, the multilayer film is a stretch food film.

[0020] A multilayer film according to embodiments disclosed herein includes a first outer layer, a second outer layer, and a core, the core including one or more core layers. The core is disposed between the first outer layer and the second outer layer. The core includes a first core layer including an ethylene-propylene copolymer.

[0021] First and second outer layers of the multilayer film The first and second outer layers of the multilayer film are not particularly limited. The first and second outer layers can have the same polymer composition or different polymer compositions. In some embodiments, each of the first and second outer layers has a thickness that is 10 to 30% of the total thickness of the multilayer film.

[0022] In some embodiments, the first outer layer and / or the second outer layer comprises an ethylene-based polymer such as, for example, LLDPE, LDPE, MDPE, or HDPE. For example, in some embodiments, the first outer layer and / or the second outer layer comprises LLDPE, LDPE, or a blend thereof.

[0023] In embodiments in which the first outer layer and / or the second outer layer comprises LLDPE, the LLDPE has a viscosity of 0.930 g / cm 3 It may have a density of 0.930 g / cm 3 All individual values ​​and subranges below are included and disclosed herein, for example, the density of linear low density polyethylene is 0.870 g / cm3 as a lower limit. 3 ~ 0.928, 0.925, 0.920, or 0.915 g / cm 3 0.870 to 0.930 g / cm 3 All individual values ​​and subranges are included and disclosed herein.

[0024] In embodiments in which the first outer layer and / or the second outer layer comprises an LLDPE, the LLDPE can have a melt index (I2) in the range of 0.1 g / 10 min to 50 g / 10 min. All individual values ​​and subranges 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 (I2) in the range of 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.

[0025] Commercially available examples of LLDPE that may be used in the first and / or second outer layers include those available under the name ELITE™ AT from The Dow Chemical Company, including, for example, ELITE™ AT6410.

[0026] Multilayer film core The multilayer film includes a core. The core includes one or more core layers and includes 100% by weight of an ethylene-based polymer including an ethylene-propylene copolymer (described below). The core is disposed between a first outer layer and a second outer layer. The core includes a first core layer. In some embodiments, the multilayer film is a three-layer film including a first outer layer, a second outer layer, and a core, and the core includes a first core layer. In other embodiments, the core includes a first core layer, a second core layer, and a third core layer, where the first core layer is disposed between the second core layer and the third core layer, where the second core layer is disposed between the first outer layer and the first core layer, and where the third core layer is disposed between the first core layer and the second outer layer. In embodiments in which the core comprises a first core layer, a second core layer, and a third core layer, the multilayer film comprises at least five layers (e.g., a multilayer film having a structure of first outer layer / second core layer / first core layer / third core layer / second outer layer).

[0027] The core comprises a first core layer. In some embodiments, the first core layer comprises an ethylene-propylene copolymer comprising 60-95% by weight ethylene monomer and 5-40% by weight propylene comonomer. In some embodiments, the ethylene-propylene copolymer has the following properties: 0.865-0.920 g / cm 3 a melt index (I2) of at least 0.5 g / 10 min; and a molecular weight distribution (Mw / Mn) in the range of 3.0 to 5.0. In some embodiments, the ethylene-propylene copolymer is formed in the presence of a catalyst composition comprising a single-site metallocene catalyst. In some embodiments, the ethylene-propylene copolymer has a single peak in an improved comonomer composition distribution (ICCD) elution profile between the temperature range of 40 to 100° C.

[0028] In some embodiments, the ethylene-propylene copolymer of the first core layer comprises 60-95 wt% ethylene monomer and 5-40 wt% propylene comonomer, based on the total weight of the ethylene-propylene copolymer. All individual values ​​and subranges between 60 wt% and 95 wt% ethylene monomer and 5-40 wt% propylene comonomer are disclosed and included herein. For example, the ethylene-propylene copolymer can comprise 60-95 wt%, 60-90 wt%, 70-90 wt%, or 80-90 wt% ethylene monomer and 5-40 wt%, 10-40 wt%, 10-30 wt%, or 10-20 wt% propylene comonomer, based on the total weight of the ethylene-propylene copolymer.

[0029] In some embodiments, the ethylene-propylene copolymer has a viscosity of 0.865 to 0.920 g / cm 3 It has a density in the range of 0.865 to 0.920 g / cm 3 All individual values ​​and subranges are disclosed and included herein. For example, ethylene-propylene copolymers have a viscosity of 0.865 to 0.910 g / cm 3 , 0.865~0.905g / cm 3 , 0.865~0.900g / cm 3 , or 0.865 to 0.895 g / cm 3 The density may be in the range of 0.1 to 1.0 μm.

[0030] In some embodiments, the ethylene-propylene copolymer has a heat of fusion in the range of 40-110 J / g. All individual values ​​and subranges between 40-110 J / g are disclosed and included herein. For example, the ethylene-propylene copolymer can have a heat of fusion in the range of 40-110 J / g, 45-110 J / g, 50-110 J / g, 60-110 J / g, 70-110 J / g, 80-110 J / g, 90-110 J / g, where the heat of fusion is measured according to the DSC test method described below.

[0031] In some embodiments, the ethylene-propylene copolymer has a melt index (I2) 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 can 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, or at least 0.9 g / 10 min, or can have a melt index (I2) in the range of 0.5 g / 10 min to 500 g / 10 min, 0.5 g / 10 min to 200 g / 10 min, 0.5 g / 10 min to 100 g / 10 min, 0.5 g / 10 min to 50 g / 10 min, 0.5 g / 10 min to 10 g / 10 min, or 0.5 g / 10 min to 2 g / 10 min.

[0032] In some embodiments, the ethylene-propylene copolymer has a single peak in the improved comonomer composition distribution (ICCD) elution profile between the temperature range of 40 to 100° C. The improved comonomer composition distribution (ICCD) profile of the first ethylene-propylene copolymer can be obtained by the test method described below.

[0033] In some embodiments, the ethylene-propylene copolymer has a molecular weight distribution (Mw / Mn) in the range of 3.0 to 5.0. All individual values ​​and subranges from 3.0 to 5.0 are disclosed and included herein. For example, the ethylene-propylene copolymer can have a molecular weight distribution (Mw / Mn) in the range of 3.0 to 5.0, 3.2 to 5.0, 3.4 to 5.0, 3.0 to 4.5, 3.2 to 4.5, 3.4 to 4.5, 3.0 to 4.0, 3.2 to 4.0, or 3.4 to 4.0. The molecular weight distribution (Mw / Mn) can be measured according to the GPC test method described below.

[0034] In some embodiments, the ethylene-propylene copolymer has a melt flow ratio (I 10All individual values ​​and subranges from 5 to 20 are disclosed and included herein. For example, the ethylene-propylene copolymers may have a melt flow ratio (I / I2) of 5 to 20, 6 to 20, 7 to 20, 8 to 20, 9 to 10, 10 to 20, 5 to 15, 6 to 15, 7 to 15, 8 to 15, 9 to 15, 6 to 10, 6 to 9, or 5 to 9. 10 / I2).

[0035] In some embodiments, the ethylene-propylene copolymer has a percentage of propylene units reverse-inserted based on 2,1 insertion greater than 0.7 weight percent based on the total weight of the ethylene-propylene copolymer. All individual values ​​and subranges greater than 0.7 weight percent are disclosed and included herein. For example, the ethylene-propylene copolymer can have a percentage of propylene units reverse-inserted based on 2,1 insertion greater than 0.7 weight percent, greater than 0.8 weight percent, greater than 1.0 weight percent, greater than 1.5 weight percent, greater than 2.0 weight percent, or greater than 2.5 weight percent, or within the range of 0.7 to 5.0 weight percent, 0.7 to 4.5 weight percent, 0.7 to 4.0 weight percent, 0.7 to 3.5 weight percent, or 0.7 to 3.2 weight percent, based on the total weight of the ethylene-propylene copolymer. The percentage of propylene units reverse-inserted based on 2,1 insertion can be measured according to the test method described below.

[0036] In some embodiments, the first core layer comprises 20-40 wt% ethylene-propylene copolymer based on the total weight of the first core layer. All individual values ​​and subranges between 20-40 wt% are disclosed and included herein. For example, the first core layer can comprise 20-40 wt%, 20-35 wt%, 25-40 wt%, or 25-35 wt% ethylene-propylene copolymer based on the total weight of the first core layer. In other embodiments, the first core layer comprises 80-100 wt% ethylene-propylene copolymer based on the total weight of the first core layer. All individual values ​​and subranges between 80-100 wt% are disclosed and included herein. For example, the first core layer can comprise 80-100 wt%, 80-95 wt%, 80-90 wt%, or 90-100 wt% ethylene-propylene copolymer based on the total weight of the first core layer.

[0037] In some embodiments, in addition to the ethylene-propylene copolymer, the first core layer can include 60-80 wt% of an ethylene-based polymer, such as LLDPE, LDPE, MDPE, HDPE, or a combination thereof, based on the total weight of the first core layer. For example, in some embodiments, the first core layer includes 60-80 wt% LLDPE.

[0038] In embodiments where the first core layer comprises LLDPE, the LLDPE has a viscosity of 0.930 g / cm 3 It may have a density of 0.930 g / cm 3 All individual values ​​and subranges below are included and disclosed herein, for example, the density of linear low density polyethylene is 0.870 g / cm3 as a lower limit. 3 ~ 0.928, 0.925, 0.920, or 0.915 g / cm 3 0.870 to 0.930 g / cm 3 All individual values ​​and subranges are included and disclosed herein.

[0039] In embodiments in which the first core layer comprises an LLDPE, the LLDPE can have a melt index (I2) in the range of 0.1 g / 10 min to 50 g / 10 min. All individual values ​​and subranges 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 (I2) in the range of 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.

[0040] In some embodiments, in addition to the first core layer, the core of the multilayer film further includes a second core layer and a third core layer, where the second core layer is disposed between the first outer layer and the first core layer, and the third core layer is disposed between the second outer layer and the first core layer.

[0041] In some embodiments, the second core layer and the third core layer have the same polymer composition as the first core layer. In other embodiments, the second core layer and / or the third core layer have a different polymer composition than the first core layer. For example, in some embodiments, the second core layer and / or the third core layer also comprises an ethylene-propylene copolymer comprising 60-95 wt% ethylene monomer and 5-40 wt% propylene comonomer, the ethylene-propylene copolymer having the following properties: density in the range of 0.865-0.920 g / cc; melt index (I2) of at least 0.5 g / 10 min; and molecular weight distribution (Mw / Mn) of 3.0-5.0. In such embodiments, the second core layer and / or the third core layer can have the same polymer composition as the first core layer, and the ethylene-propylene copolymer of the second core layer and / or the third core layer can have the same properties as the ethylene-propylene copolymer of the first core layer (discussed above).

[0042] In embodiments where the multilayer film comprises a first core layer, a second core layer, and a third core layer, each of the second core layer and the third core layer can comprise an ethylene-based polymer, such as LLDPE, LDPE, MDPE, HDPE, or a combination thereof. For example, in some embodiments, each of the second core layer and the third core layer can comprise, independently, LLDPE, LDPE, or a blend thereof. In embodiments where each of the second core layer and the third core layer comprises, independently, LLDPE, LDPE, or a blend thereof, the LLDPE can be an ethylene-based polymer having a viscosity of 0.930 g / cm 3 It may have a density of 0.930 g / cm 3 All individual values ​​and subranges below are included and disclosed herein, for example, the density of linear low density polyethylene is 0.870 g / cm3 as a lower limit. 3 ~ 0.928, 0.925, 0.920, or 0.915 g / cm 3 0.870 to 0.930 g / cm 3 All individual values ​​and subranges are included and disclosed herein.

[0043] In embodiments in which each of the second and third core layers comprises an LLDPE, the LLDPE can have a melt index (I2) in the range of 0.1 g / 10 min to 50 g / 10 min. All individual values ​​and subranges 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 (I2) in the range of 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.

[0044] In some embodiments, the first core layer and the second core layer have a thickness of 5-30% of the total thickness of the multilayer film, or 10-30% of the total thickness of the multilayer film. In some embodiments, the second core layer has a total thickness of 20%-70% based on the total thickness of the multilayer film. In some embodiments, the core of the multilayer film has a thickness of 70-90% based on the total thickness of the multilayer film.

[0045] Additives It should be understood that any of the foregoing layers can further include one or more additives known to those skilled in the art, such as, for example, antioxidants, UV stabilizers, heat stabilizers, slip agents, antiblock agents, antistatic agents, pigments or colorants, processing aids, crosslinking catalysts, flame retardants, fillers, and foaming agents, etc. For example, in some embodiments, the first outer layer and the second outer layer each include an antiblock agent.

[0046] Multilayer Film The multilayer films disclosed herein can be manufactured using techniques known to those skilled in the art based on the teachings herein. For example, the multilayer films can be produced by coextrusion. The formation of coextruded multilayer films is known in the art and is applicable to the present disclosure. Coextrusion systems for making multilayer films use at least two extruders that feed into a common die assembly. The number of extruders depends on the number of different materials or polymers that make up the coextruded film. For example, a five-layer coextrusion may require up to five extruders, but fewer extruders may be used if two or more layers are made of the same material or polymer.

[0047] The multilayer film of the present invention may have several desirable properties in various embodiments. Without being bound by any theory, the specific structure of the multilayer film, together with the inclusion of a specific ethylene-propylene copolymer in the core, may result in the multilayer film having high tear resistance properties. In some embodiments, the multilayer film of the present invention exhibits a machine direction tear resistance of at least 1700g (or at least 1900g, or at least 2000g, or at least 2100g, or at least 2200g), or in the range of 1700g to 3000g, 2000g to 3000g, 2100g to 3000g, or 2200g to 3000g. The machine direction tear resistance may also be expressed in grams per μm of thickness of the multilayer film. For example, in some embodiments, the multilayer films of the present invention exhibit a machine direction tear resistance of at least 170 g / μm (or at least 190 g / μm, or at least 200 g / μm, or at least 210 g / μm, or at least 220 g / μm), or in the range of 170-300 g / μm, 200-300 g / μm, 210-300 g / μm, or 220-300 g / μm. Tear resistance can be measured according to ASTM D1922-09.

[0048] Similarly, in some embodiments, the multilayer film exhibits a lateral tear resistance of at least 1400 g (or at least 1600 g, or at least 1800 g, or at least 1900 g, or at least 2000 g, or at least 2100 g, or at least 2200 g), or in the range of 1400 g to 3000 g, 2000 g to 3000 g, 2100 g to 3000 g, or 2200 g to 3000 g. The lateral tear resistance can also be expressed in grams per μm of thickness of the multilayer film. For example, in some embodiments, the multilayer film exhibits a transverse tear resistance of 140 g / μm (or at least 160 g / μm, or at least 180 g / μm, or at least 190 g / μm, or at least 200 g / μm, or at least 210 g / μm, or at least 220 g / μm), or in the range of 140-300 g / μm, 200-300 g / μm, 210-300 g / μm, or 220-300 g / μm. Transverse tear resistance can be measured according to ASTM D1922-09.

[0049] In some embodiments, the multilayer film has a thickness between 15 and 150 microns, or between 50 and 150 microns, or between 75 and 125 microns, or between 90 and 110 microns.

[0050] In some embodiments, the multilayer films of the present invention comprise at least 90% by weight ethylene-based polymer, or at least 95% by weight ethylene-based polymer, or at least 99% by weight ethylene-based polymer, or at least 99.5% by weight ethylene-based polymer, or at least 99.9% by weight ethylene-based polymer, based on the total weight of the multilayer film. Because the multilayer films in some embodiments comprise at least 90% by weight ethylene-based polymer, they may be compatible with polyethylene recycle streams.

[0051] Stretch Food Film In one embodiment, the multilayer film of the present invention is a stretch hood film. A stretch hood is a tube of film sealed at one end that is stretched over a palletized load to secure the contents to the pallet. The film is cut to the appropriate length, heat sealed at the top end, and gathered into four "fingers." These fingers stretch the film in the horizontal (cross) direction until the film's dimensions are slightly larger than the load's dimensions, and then the stretched film is pulled down onto the pallet and unfolded as it moves. By varying the unfolding speed, some stretch can be obtained in the vertical (machine) direction to better hold the load on the pallet. At the bottom of the pallet, the fingers release the film, and the film typically wraps around under the bottom of the pallet. Stretch hood films can be manufactured using techniques known to those skilled in the art based on the teachings herein.

[0052] Goods The present invention also provides an article comprising any of the multilayer films of the present invention described herein. Examples of such articles may include wraps, packaging, flexible packaging, pouches, and sachets. The articles of the present invention can be formed from the multilayer films disclosed herein using techniques known to those skilled in the art in view of the teachings herein.

[0053] Test Method density Density is measured in grams / cm according to ASTM D792. 3 (g / cm 3 )

[0054] Melt index (I2 and I 10 ) The melt index (I2) is measured according to ASTM D-1238 at 190°C and 2.16 kg. 10 ) is measured at 190°C and 10 kg according to ASTM D-1238. Melt index values ​​are reported in g / 10 min, which corresponds to grams dissolved per 10 minutes. The melt flow ratio is I 10 / I2.

[0055] DSC method - Heat of fusion Differential scanning calorimetry (DSC) is a common technique that can be used to study the melting and crystallization of semicrystalline polymers. DSC measurements in general and the application of DSC to the study of semicrystalline polymers are explained in standard textbooks (e.g., Thermal Characterization of Polymeric Materials, ed. by E A Turi, Academic Press, 1981).

[0056] The heat of fusion is determined using a DSC from TA Instruments, Inc. The test is performed with reference to ASTM standard D3428. Calibration is performed by preparing 2-3 mg of indium and placing it in a Tzero aluminum pan. The pan is then loaded into the DSC instrument and subjected to the following heating program cycle: 1) equilibrate the test chamber at 180°C, 2) hold the temperature at 180°C for 1 minute, 3) decrease the temperature to 130°C at 10°C / min, 4) hold the temperature at 130°C for 3 minutes, and 5) increase the temperature to 180°C at 10°C / min. Once complete, the last heating curve performed in step 5 is analyzed to determine the melting temperature of the indium sample. The DSC is considered to be functioning in accordance with the standard if the melting temperature is within 0.5°C tolerance of 156.6°C.

[0057] For sample testing, the polymer sample is first pressed into a thin film at a temperature of 190°C. Approximately 4-5 mg of sample is weighed and placed in the DSC pan. A lid is crimped onto the pan to ensure a sealed environment. The sample pan is placed into the DSC cell and equilibrated at 180°C. The sample is held at this temperature for 5 minutes. The sample is then cooled to -90°C at a rate of 10°C / min and held isothermal at that temperature for 5 minutes. The sample is subsequently heated to 150°C (to ensure complete melting) at a rate of 10°C / min, a step referred to as the second heating curve. The resulting enthalpy curve is analyzed for peak melting temperature, crystallization onset and peak crystallization temperatures, and heat of fusion (also known as heat of fusion) ΔHf. The heat of fusion (in joules / gram) is measured from the second heating curve by linear integration of the melting endotherm according to the baseline.

[0058] Improved Comonomer Composition Distribution (ICCD) An improved comonomer content analysis method (iCCD) was developed in 2015 (Cong and Parrott et al., WO 2017 / 040127(A1)). iCCD tests were performed using a Crystallization Elution Fractionation (CEF) instrument (PolymerChar, Spain) equipped with an IR-5 detector (PolymerChar, Spain) and a two-angle light scattering detector model 2040 (Precision Detectors, now Agilent Technologies). A 5 cm or 10 cm (length) x 1 / 4 inch (inner diameter) guard column packed with 20-27 micron glass (MoSCi Corporation, USA) on stainless steel was placed immediately before the 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, catalog number 10181-3) was obtained from EMD Chemicals (which could be used to dry the ODCB solvent earlier). The dried silica was packed into three empty HT-GPC columns to further purify the ODCB as the eluent. The CEF instrument was equipped with an autosampler with N2 purging capability. Before use, the ODCB was agitated for 1 h with dry nitrogen (N2). Sample preparation was performed at 4 mg / mL (unless otherwise specified) using the autosampler at 160 °C for 1 h with shaking. The injection volume was 300 μL. The temperature profile of the iCCD was crystallization from 105 °C to 30 °C at 3 °C / min, thermal equilibration at 30 °C for 2 min (including setting the soluble fraction elution time to 2 min), and elution from 30 °C to 140 °C at 3 °C / min. The flow rate during crystallization was 0.0 mL / min. The flow rate during elution is 0.50 mL / min. Data are collected at 1 data point / sec.

[0059] The iCCD column was packed with gold-coated nickel particles (Bright 7GNM8-NiS, Nippon Chemical Industrial Co.) in a 15 cm (length) x ¼ inch (inner diameter) stainless steel tube. Column packing and conditioning was performed with a slurry method according to references (Cong, R.; Parrott, A.; Hollis, C.; Cheatham, M. WO 2017040127 A1). The final pressure using TCB slurry packing was 150 bar.

[0060] Column temperature calibration was performed using the reference material linear homopolymer polyethylene in ODCB (comonomer content zero, melt index (I2) 1.0, polydispersity M w / M n Conventional gel permeation chromatography was performed using a mixture of 1.0 mg / mL elution of 100 mM NaCl (approximately 2.6 mg / mL) and eicosane (2 mg / mL). The iCCD temperature calibration consisted of four steps: (1) calculating the delay volume, defined as the temperature offset between the measured peak elution temperatures of eicosane minus 30.00°C; (2) subtracting the temperature offset of the elution temperature from the iCCD raw temperature data. Note that this temperature offset is a function of experimental conditions such as elution temperature, elution flow rate, etc.; (3) creating a linear calibration line converting elution temperatures over the range of 30.00°C to 140.00°C, such that a linear homopolymer polyethylene standard has a peak temperature at 101.0°C and eicosane has a peak temperature of 30.0°C; (4) linearly extrapolating elution temperatures below 30.0°C for soluble fractions measured isothermally at 30°C by using an elution heating rate of 3°C / min according to references (Cerk and Cong et al., U.S. Patent No. 9,688,795).

[0061] Comonomer content versus iCCD elution temperature was constructed using 12 reference materials (ethylene homopolymers and ethylene-octene random copolymers made with single-site metallocene catalysts, with ethylene equivalent weight average molecular weights ranging from 35,000 to 128,000). All of these reference materials were analyzed at 4 mg / mL with the same methodology as specified previously. The reported elution peak temperatures have an R of 0.978. 2 followed the plot of mole % of octene versus iCCD elution temperature.

[0062] [Table 1]

[0063] The molecular weights of the polymers and polymer fractions were determined directly from the LS detector (at a 90 degree angle) and the concentration detector (IR-5) according to the Rayleigh-Gans-Debys approximation (Striegel and Yau, "Modern Size Exclusion Liquid Chromatogram", Page 242 and Page 263) by assuming a form factor of 1 and all virial coefficients of zero. Set the integration window to integrate all chromatograms with elution temperatures ranging from 23.0 to 120 °C (temperature calibration specified above).

[0064] Calculating molecular weight (Mw) from the iCCD involves the following steps: (1) Measure the inter-detector offset. The offset is defined as the geometric volume offset between the LS detector relative to the concentration detector. It is calculated as the difference in elution volume (mL) of the polymer peak between the concentration detector and the LS chromatogram. This is converted to a temperature offset by using the elution heat rate and elution flow rate. A linear high density polyethylene (comonomer content zero, melt index (I2) of 1.0, polydispersity M w / M n(2) Conventional gel permeation chromatography uses about 2.6). The same experimental conditions as the conventional iCCD method above are used, except for the following parameters: crystallization from 140°C to 137°C at 10°C / min, thermal equilibration at 137°C for 1 min as soluble fraction elution time, soluble fraction (SF) time of 7 min, elution from 137°C to 142°C at 3°C / min. The flow rate during crystallization is 0.0 mL / min. The flow rate during elution is 0.80 mL / min. The sample concentration is 1.0 mg / mL. (2) Each LS data point of the LS chromatogram is shifted to correct for inter-detector offset before integration. (3) The baseline-subtracted LS and concentration chromatograms are integrated over the entire elution temperature range of step (1). The MW detector constant is calculated using HDPE samples of known MW in the range of 100,000-140,000 Mw and the area ratio of the LS to the concentration integrated signal. (4) The Mw of the polymer was calculated by using the ratio of the integrated light scattering detector (at a 90 degree angle) to the concentration detector and using the MW detector constant.

[0065] Conventional GPC (Mw / Mn) Conventional GPC is obtained by a high temperature gel permeation chromatography (GPC) instrument (PolymerChar, Spain). The IR5 detector ("measurement channel") is used as a concentration detector. The GPCOne software (PolymerChar, Spain) is used to calculate the weight average (Mw) and number average (Mn) molecular weight of the polymer and to determine the molecular weight distribution (Mw / Mn). The method uses four 20 micron PL gel mixed A columns (Agilent Technologies, column dimensions 100 x 7.6 mm) operating at a system temperature of 150 °C. The samples are prepared at a concentration of 2 mg / mL in 1,2,4-trichlorobenzene solvent containing 200 parts per million of the antioxidant butylated hydroxytoluene (BHT) at 160 °C for 3 hours with gentle shaking by an autosampler (PolymerChar, Spain). The flow rate is 1.0 mL / min and the injection size is 200 microliters. Use the GPCOne software to calculate the number of plates. The chromatography system requires a minimum of 22,000 plates.

[0066] The GPC column set is calibrated by running at least 20 narrow molecular weight distribution polystyrene standards. Calibration uses a third order fit to a system with three 10 micron PL gel mixed B columns or a fifth order fit to a system with four 20 micron PL gel mixed A columns. The molecular weights (MW) of the standards range from 580 g / mol to 8,400,000 g / mol, and the standards are included in six "cocktail" mixtures. There are approximately 10 separations between the individual molecular weights in each standard mixture. The standard mixtures are purchased from Agilent Technologies. The polystyrene standards are prepared at 0.025 g in 50 mL of solvent for molecular weights of 1,000,000 g / mol or greater, and at 0.05 g in 50 mL of solvent for molecular weights less than 1,000,000 g / mol. The polystyrene standards are dissolved at 80°C with gentle agitation for 30 minutes. The narrow standards mixtures are run first and in order of decreasing highest molecular weight component to minimize degradation. The polystyrene standard peak molecular weights are converted to polyethylene molecular weights using the following equation (1) (as described in Williams and Ward, J. Polym. Sci., Polym. Letters, 6, 621 (1968)):

[0067]

number

number

[0068] Chromatographic peaks should be set to contain areas that show significant visible deviations from the baseline when the chromatogram is viewed at 20% peak height. The baseline should not be integrated to less than 100 polyethylene equivalent molecular weights, and care should be taken in accounting for discrepancies in antioxidants from prepared samples and chromatographic mobile phases.

[0069] The use of a decane flow marker is shown in the IR5 chromatogram. The difference in baseline (response) Y values ​​between the start and end of the baseline should not exceed 3% of the integrated peak height of the chromatogram. In such cases, chromatographic samples should be treated with appropriate matching of antioxidants in the sample and mobile phase.

[0070] w(10 5 The weight fraction (w g / mol) of the 1000-fold increase in ... i vs. log M cc,i ) is calculated.

[0071]

number

[0072] Comonomer content and proportion of reverse-inserted propylene units based on 2,1 insertion The comonomer content was measured by 13C NMR according to the calculation method of Randall described in EP 3390056B1. The ethylene-propylene copolymer according to the embodiments disclosed herein may have a proportion of propylene units reverse inserted based on 2,1 insertion of more than 0.7 wt.% based on the total weight of the ethylene-propylene copolymer. The proportion of 2,1 insertion to total propylene insertion in the propylene polymer was calculated according to the calculation and test method described in EP 3390056B1 (incorporated herein by reference in its entirety). As described in EP 3390056B1, the proportion of 2,1 insertion to total propylene insertion in the propylene polymer was calculated by the following formula with reference to an article in the journal Polymer, Vol. 30 (1989), p. 1350: Proportion (%) of units reverse inserted based on 2,1 insertion =

[0073]

number

[0074] Samples were prepared by adding approximately 2.6 g of a 75 / 25 mixture of tetrachloroethane / tetrachloroethane-d2 orthodichlorobenzene, 0.025M in chromium acetylacetonate (relaxation agent), to 0.2 g of sample in a 10 mm NMR tube. The sample was dissolved and homogenized by heating the tube and its contents to 150°C. Data were collected using a Bruker 600 MHz spectrometer equipped with a multinuclear high temperature CryoProbe. Data were acquired at a sample temperature of 120°C using 2560 scans per data file, a pulse repetition delay of 7.8 seconds. Acquisition was performed using a spectral width of 35,700 Hz and a file size of 65K data points.

[0075] Cross direction (CD) and machine direction (MD) tear resistance The tear resistance of the example multilayer films is measured in both the machine direction (MD) and cross direction (CD) according to ASTM D1922-09, which determines the average force to propagate a tear in the machine and cross directions through a specified length of plastic film after the tear has been initiated. EXAMPLES

[0076] The example multilayer films discussed below contained the following materials:

[0077] ELITE™ 6410 is a linear low density polyethylene with a density of 0.912 g / cm 3 and a melt index (I2) of 0.85 g / 10 min, and is commercially available from The Dow Chemical Company, Midland, Mich. ELITE™ 6410 is an ethylene-based polymer, as that term is defined herein.

[0078] XZ89507.00 is a linear low density polyethylene commercially available from The Dow Chemical Company, Midland, Mich. XZ89507.00 has a density of 0.902 g / cm 3 and a melt index (I2) of 0.85 g / 10 min. XZ89507.00 is an ethylene-based polymer, as that term is defined herein.

[0079] XUS 39003.00 (herein "Poly.1") is an ethylene-propylene copolymer commercially available from The Dow Chemical Company, Midland, Mich. Poly.1 contains 27.1% by weight propylene comonomer and 72.9% by weight ethylene monomer, and has a viscosity of 0.867 g / cm. 3 Density: 0.90g / 10min Melt Index (I2): 10.82 10Poly.1 has a tensile strength of 1.01 to 1.01 mmHg, a heat of fusion of 50.24 J / g, and a Mw / Mn of 3.98. Poly.1 has a proportion of propylene units reverse inserted based on 2,1 insertion of 0.8 wt %, based on the total weight of Poly.1. Poly.1 is an ethylene-based polymer as that term is defined herein.

[0080] XUS 39005.00 (also referred to herein as "Poly.2") is an ethylene-propylene copolymer commercially available from The Dow Chemical Company, Midland, Mich. Poly.2 contains 17.7% by weight propylene comonomer and 82.3% by weight ethylene monomer, and has a viscosity of 0.893 g / cm. 3 Density: 1.0g / 10min Melt Index (I2): 17.50 10 Poly.2 has a .DELTA. / I2, a heat of fusion of 90.73 J / g, and a Mw / Mn of 3.99. As seen in FIG. 1, Poly.2 has a single peak in the improved comonomer composition distribution (ICCD) elution profile between the temperature range of 40-100° C. Poly.2 has a proportion of reverse inserted propylene units based on 2,1 insertion of 3.0 wt %, based on the total weight of Poly.2. Poly.2 is an ethylene-based polymer as that term is defined herein.

[0081] DOWLEX™ GM8090 is a linear low density polyethylene commercially available from The Dow Chemical Company, Midland, Mich. DOWLEX™ GM8090 has a density of 0.916 g / cm 3 and a melt index (I2) of 1.0 g / 10 min. DOWLEX™ GM8090 is an ethylene-based polymer as that term is defined herein.

[0082] DOWLEX™ 150E is a low density polyethylene available from Dow Chemical Company, Midland, Mich. LDPE 150E has a density of 0.921 g / cm 3and a melt index (I2) of 0.25 g / 10 min. LDPE 150E is an ethylene-based polymer as that term is defined herein.

[0083] VERSIFY™ 2300 has a viscosity of 0.867 g / cm 3 VERSIFY™ 2300 is a propylene elastomer having a density of 1000 to 15000 mm. VERSIFY™ 2300 is commercially available from The Dow Chemical Company, Midland, Mich. VERSIFY™ 2300 is not an ethylene-based polymer as that term is defined herein.

[0084] AFFINITY™ PF1140 is 0.897 g / cm 3 and a melt index (I2) of 1.6 g / 10 min. AFFINITY™ PF1140 is commercially available from The Dow Chemical Company, Midland, Mich. AFFINITY™ PF1140 is an ethylene-based polymer as that term is defined herein.

[0085] AFFINITY™ EG 8100G is 0.870 g / cm 3 and a melt index (I2) of 1.0 g / 10 min. AFFINITY™ EG 8100G is commercially available from The Dow Chemical Company, Midland, Mich. AFFINITY™ EG 8100G is an ethylene-based polymer as that term is defined herein.

[0086] Multilayer films are formed using the above materials. The multilayer films are produced on a Collin coextrusion blown film line with a blow-up ratio (BUR) of 3.5 and a total thickness of 100 μm by extruding the multilayer films. The Collin coextrusion blown film line is produced by Collin Lab&Pilot Solutions GmbH. The Collin coextrusion blown film line is configured as shown in Table 1 below to prepare the multilayer films described in Tables 2 and 3. Table 2 reports the structure of the three-layer multilayer film formed. Table 3 reports the structure of the five-layer multilayer film formed with a structure of 20 / 15 / 30 / 15 / 20 micron layers. Table 4 reports the structure of the five-layer multilayer film formed with a structure of 20 / 20 / 20 / 20 / 20 micron layers. The inventive and comparative examples have a thickness of 100 microns (μ).

[0087] [Table 2]

[0088] [Table 3]

[0089] [Table 4]

[0090] [Table 5]

[0091] Machine direction (MD) and cross direction (CD) tear resistance is measured for each of the comparative examples and inventive examples. The results are reported in Table 5 below. As can be seen from the results, the inventive examples show CD tear resistance and MD resistance that are comparable or improved over the comparative examples. The inventive examples include all ethylene-based polymers that are desirable for polyethylene recycle streams, but not Comparative Examples 1-3. Comparative Examples 4 and 5 include an ethylene-octene copolymer in the core, as opposed to an ethylene-propylene copolymer in the core, and show inferior tear strength compared to the inventive examples. The inventive examples show unexpectedly superior tear strength properties compared to these comparative examples.

[0092] [Table 6]

[0093] All documents cited herein, including any cross-referenced or related patents or applications, if any, and any patent applications or patents to which this application claims priority or the benefit thereof, are incorporated herein by reference in their entirety, unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein, or that it alone, or in any combination with any other reference, teaches, suggests, or discloses such invention. Furthermore, to the extent that a meaning or definition of any term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

[0094] While particular embodiments of the present invention 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 invention. Therefore, it is intended in the appended claims to cover all such changes and modifications that are within the scope of this invention.

Claims

1. A multilayer film, 1. A sintered body comprising: a first outer layer, a second outer layer, and a core comprising one or more core layers, the core being disposed between the first outer layer and the second outer layer, the core comprising 100 wt. % of an ethylene-based polymer, based on a total polymer weight of the core, the first core layer comprising an ethylene-propylene copolymer comprising 60 to 95 wt. % ethylene monomer and 5 to 40 wt. % propylene comonomer, the ethylene-propylene copolymer having the following properties: 0.865~0.920g / cm ３ and a density in the range of; A melt index (I) of at least 0.5 g / 10 min. ２ ); and A multilayer film having a molecular weight distribution (Mw / Mn) of 3.0 to 5.

0.

2. 10. The film of claim 1, wherein the ethylene-propylene copolymer is further characterized by having a single peak in an improved comonomer composition distribution (ICCD) elution profile between the temperature range of 40 and 100°C.

3. The ethylene-propylene copolymer has a melt flow ratio (I １０ / I ２ 10. The film of claim 1 further characterized by having:

4. 10. The film of claim 1, wherein the ethylene-propylene copolymer is formed in the presence of a catalyst composition comprising a single-site metallocene catalyst.

5. 10. The film of claim 1, wherein the first core layer further comprises linear low density polyethylene (LLDPE).

6. 10. The film of claim 1, wherein the first outer layer and the second outer layer each independently comprise linear low density polyethylene (LLDPE).

7. 10. The film of claim 1, wherein the core further comprises a second core layer and a third core layer, the second core layer being disposed between the first outer layer and the first core layer, and the third core layer being disposed between the first core layer and the second outer layer.

8. 8. The film of claim 7, wherein each of the second core layer and the third core layer independently comprises linear low density polyethylene (LLDPE).

9. The film of claim 1 , wherein the film is a machine direction oriented film.

10. The multilayer film of any one of claims 1 to 9, wherein the film is a stretch food film.

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