Multilayer films containing ethylene-based copolymers

Abstract

A multilayer film comprising an ethylene-based copolymer is provided. The multilayer film may 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-based copolymer selected from the group consisting of ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer. The first core layer according to the embodiments disclosed herein is less than 20% of the total thickness of the multilayer film. The multilayer film of the present invention may exhibit improved or desirable properties, such as high tear resistance, compared to existing multilayer film structures.

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 copolymers.

[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 desired properties, such as sufficient tear resistance, to avoid the film being damaged during the film packaging process 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, exhibit desirable tear resistance, and have other properties maintained or improved. Summary of the Invention

[0003] The present disclosure satisfies one or more of the above needs by providing a multilayer film that exhibits 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 better than other multilayer films. The multilayer film according to the embodiments disclosed herein includes at least a first outer layer, a second outer layer, and a first core layer, the first core layer includes an ethylene-based copolymer and is less than 20% of the total thickness of the multilayer film. Without being bound by theory, the structure of the film with a thin first core layer (less than 20% of the total thickness of the film) and a specific ethylene-based copolymer, among other features, results in surprisingly desirable tear resistance and maintained or improved dart impact compared to existing film structures.

[0004] Disclosed herein is a multilayer film.In one embodiment, the multilayer film comprises a first outer layer, a second outer layer, and a core, the core comprises one or more core layers, the core is disposed between the first outer layer and the second outer layer, the core comprises more than 90 wt% of an ethylene-based polymer based on the total polymer weight of the core, the first core layer comprises an ethylene-based copolymer selected from the group consisting of ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer, the first core layer is less than 20% of the total thickness of the multilayer film, and the multilayer film has a transverse tear resistance of at least 25 g / μm.

[0005] These and other embodiments are described in greater detail in the Detailed Description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] 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 film, blown film, oriented film, stretch food film, and the like. The multilayer film is also suitable for use in trash bags or trash bag liners, heavy duty shipping bags, mattress films, food storage, frozen food storage, fertilizer storage, silage, and grain storage applications. However, the present disclosure is an exemplary implementation of the embodiments described herein, and therefore the present disclosure should not be construed as limiting the embodiments described below.

[0007] 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.

[0008] 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, ethylene-based copolymers such as ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer can include at least two structurally different monomers (e.g., ethylene / butyl acrylate copolymer includes at least 50% by weight copolymerized units of ethylene monomer and butyl acrylate comonomer), 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 although the copolymers can consist only of two structurally different monomers, they do not necessarily consist only of two structurally different monomers, and can include additional monomers or functional materials or modifiers.

[0009] As used herein, the term "ethylene-based copolymer" is intended to mean a copolymer that contains a majority amount (greater than 50% by weight) of units derived from ethylene monomer and units of at least one different comonomer. An ethylene-based copolymer is an ethylene-based polymer as that term is defined below. Examples of ethylene-based copolymers include ethylene / butyl acrylate copolymer (units of ethylene monomer copolymerized with units of butyl acrylate comonomer), ethylene / ethyl acrylate copolymer (units of ethylene monomer copolymerized with units of ethyl acrylate comonomer), ethylene / methyl acrylate copolymer (units of ethylene monomer copolymerized with units of methyl acrylate comonomer), and ethylene / vinyl acetate copolymer (units of ethylene monomer copolymerized with units of vinyl acetate comonomer).

[0010] As used herein, the term "polyethylene" or "ethylene-based polymer" is intended to mean a polymer that contains a majority (greater than 50% by weight) of units derived from ethylene monomer. This includes polyethylene homopolymers and ethylene-based copolymers. Unless otherwise specified, the ethylene-based copolymers disclosed herein (e.g., ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer) 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 components, steps, or procedures, 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-based copolymer selected from the group consisting of ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer.

[0021] In some embodiments, a multilayer film comprises a first outer layer, a second outer layer, and a core, the core comprising one or more core layers, the core layer being disposed between the first outer layer and the second outer layer, the core comprising greater than 90 weight percent ethylene-based polymer based on the total polymer weight of the core, the first core layer comprising an ethylene-based copolymer selected from the group consisting of ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer, the first core layer being less than 20% of the total thickness of the multilayer film, and the multilayer film having a lateral tear resistance of at least 25 g / μm.

[0022] In some embodiments, the ethylene-based copolymer comprises 80-100 wt% of the first core layer, based on the total weight of the first core layer. In some embodiments, the ethylene-based copolymer has a melt index (I2) of less than 5 g / 10 min. In some embodiments, the ethylene-based copolymer is an ethylene / vinyl acetate copolymer comprising 9-28 wt% vinyl acetate comonomer, based on the total weight of the ethylene / vinyl acetate copolymer. In other embodiments, the ethylene-based copolymer is an ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, or ethylene / methyl acrylate copolymer comprising 15-30 wt% acrylate comonomer, based on the total weight of the ethylene-based copolymer.

[0023] In some embodiments, the first outer layer and the second outer layer comprise polyethylene having a density less than 0.930 g / cc and a melt index (I2) less than 7 g / 10 min.

[0024] In some embodiments, the core comprises 100 weight percent ethylene-based polymer. In some embodiments, the multilayer film comprises greater than 90 weight percent ethylene-based polymer, greater than 95 weight percent ethylene-based polymer, or greater than 99 weight percent ethylene-based polymer.

[0025] In some embodiments, the first core layer is 5-15% of the total thickness of the multilayer film.

[0026] In some embodiments, the multilayer film comprises at least five layers including a first outer layer, a second outer layer, a first core layer, a second core layer, and a third core layer, the first core layer being disposed between the second core layer and the third core layer, the second core layer and the third core layer independently comprising a polyethylene having a density less than 0.930 g / cc and a melt index (I2) less than 7 g / 10 min. In some embodiments, the multilayer film comprises 5 to 11 layers.

[0027] The multilayer films of the present invention may comprise a combination of two or more embodiments described herein.

[0028] 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, the first and second outer layers have a thickness that is 80-90% of the total thickness of the multilayer film.

[0029] In some embodiments, the first outer layer and the second outer layer each comprise a polyethylene having a density less than 0.930 g / cc and a melt index (I2) less than 7 g / 10 min. 3All individual values ​​and subranges below are included and disclosed herein, for example, the density of polyethylene is 0.870 g / cm 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 of the melt index (I2) less than 7 g / 10 min are included and disclosed herein. All individual values ​​and subranges of the melt index (I2) less than 7 g / 10 min are included and disclosed herein. For example, the melt index (I2) of the polyethylene can be less than 6 g / 10 min, less than 5 g / 10 min, less than 4 g / 10 min, less than 3 g / 10 min, less than 2 g / 10 min, or less than 1 g / 10 min.

[0030] In some embodiments, the first outer layer and / or the second outer layer comprises an ethylene-based polymer such as, for example, ULDPE, LLDPE, LDPE, MDPE, or HDPE. For example, in some embodiments, the first outer layer and / or the second outer layer comprises ULDPE, LLDPE, LDPE, or blends thereof.

[0031] 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.

[0032] Suitable polyethylenes for use in the first and / or second outer layers of some embodiments of the present invention include very low density polyethylene (ULDPE), low density polyethylene (LDPE), polyethylene plastomer / elastomer, linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), 0.930 g / cm 3 Examples of polyolefins include, but are not limited to, other ethylene-based polymers (e.g., reinforced polyethylenes), olefin block copolymers, and combinations thereof having a density of 1000 to 10000 MPa. In some embodiments of the present invention, various commercially available polyethylenes are contemplated for use as polyolefins. Examples of commercially available polyethylene plastomers / elastomers that may be used in embodiments of the present invention include those available from The Dow Chemical Company under the names AFFINITY™ and ENGAGE™, such as AFFINITY™ PL 1880G. Examples of commercially available LDPEs that may be used in embodiments of the present invention include those available from The Dow Chemical Company under the names DOW LDPE™ and AGILITY™. Examples of commercially available ULDPEs that may be used in embodiments of the present invention include ATTANE™ very low density polyethylene available from The Dow Chemical Company. Examples of commercially available LLDPEs that may be used in embodiments of the present invention include DOWLEX™ linear low density polyethylene available from The Dow Chemical Company. Examples of commercially available olefin block copolymers that may be used in embodiments of the present invention include those available from The Dow Chemical Company under the name INFUSE™. Examples of other commercially available ethylene-based polymers that may be used in some embodiments include those available from The Dow Chemical Company under the names ELITE™, ELITE™ AT, and INNATE™.

[0033] Multilayer film core The multilayer film includes a core. The core includes one or more core layers and includes greater than 90% by weight of an ethylene-based polymer, including an ethylene-based 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).

[0034] In some embodiments, the multilayer film comprises at least five layers including a first outer layer, a second outer layer, a first core layer, a second core layer, and a third core layer, the first core layer being disposed between the second core layer and the third core layer, the second core layer and the third core layer independently comprising a polyethylene having a density less than 0.930 g / cc and a melt index (I2) less than 7 g / 10 min.

[0035] The core comprises a first core layer. In some embodiments, the first core layer comprises an ethylene-based copolymer selected from the group consisting of ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer. In some embodiments, the ethylene-based copolymer comprises 80-100 weight percent of the first core layer, based on the total weight of the first core layer. All individual values ​​and subranges between 80-100 weight percent are disclosed herein. In some embodiments, the ethylene-based copolymer comprises 85-100 weight percent, 90-100 weight percent, 95-100 weight percent, or 99-100 weight percent of the first core layer, based on the total weight of the first core layer.

[0036] In some embodiments, the ethylene-based copolymer of the first core layer has a density of 0.900 g / cc to 0.950 g / cc. All individual values ​​and subranges between 0.900 and 0.950 g / cc are disclosed and included herein. For example, the ethylene-based copolymer of the first core layer can have a density of 0.900 g / cc to 0.945 g / cc, 0.905 g / cc to 0.945 g / cc, 0.910 g / cc to 0.945 g / cc, or 0.920 g / cc to 0.945 g / cc.

[0037] In some embodiments, the ethylene-based copolymer of the first core layer has a melt index (I2) of less than 5 g / 10 min. All individual values ​​and subranges less than 5 g / 10 min are disclosed and included herein. For example, the ethylene-based copolymer can have a melt index (I2) of less than 5 g / 10 min, less than 4 g / 10 min, less than 3 g / 10 min, less than 2 g / 10 min, or less than 1 g / 10 min.

[0038] In some embodiments, the ethylene-based copolymer is an ethylene / vinyl acetate copolymer that includes 9 to 28 weight percent vinyl acetate comonomer, based on the total weight of the ethylene / vinyl acetate copolymer. All individual values ​​and subranges between 9 and 28 weight percent are disclosed and included herein. For example, the ethylene / vinyl acetate copolymer can include 10 to 25 weight percent, 12 to 23 weight percent, or 15 to 20 weight percent vinyl acetate comonomer, based on the total weight of the ethylene / vinyl acetate copolymer.

[0039] In some embodiments, the ethylene-based copolymer is an ethylene / butyl acrylate copolymer, an ethylene / ethyl acrylate copolymer, or an ethylene / methyl acrylate copolymer that comprises 15 to 30 weight percent acrylate comonomer, based on the total weight of the ethylene-based copolymer. All individual values ​​and subranges between 15 and 30 weight percent are disclosed and included herein. For example, an ethylene / butyl acrylate copolymer, an ethylene / ethyl acrylate copolymer, or an ethylene / methyl acrylate copolymer can contain 15 to 28 weight percent or 15 to 26 weight percent acrylate comonomer.

[0040] Examples of commercially available ethylene-based copolymers selected from the group consisting of ethylene / butyl acrylate copolymers, ethylene / ethyl acrylate copolymers, ethylene / methyl acrylate copolymers, and ethylene / vinyl acetate copolymers that can be used in embodiments of the present invention include polymers designated ELVALOY™ and ELVAX™ available from The Dow Chemical Company.

[0041] In some embodiments, in addition to the ethylene-based copolymer, the first core layer can include an ethylene-based polymer such as, for example, ULDPE, LLDPE, LDPE, MDPE, HDPE, or combinations thereof.

[0042] In some embodiments, the core of the multilayer film further includes, in addition to the first core layer, 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 second outer layer and the first core layer.

[0043] 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 ULDPE, LLDPE, LDPE, MDPE, HDPE, or a combination thereof. For example, in some embodiments, each of the second core layer and the third core layer, independently, comprises LLDPE, LDPE, or a blend thereof. In embodiments where each of the second core layer and the third core layer, independently, comprises LLDPE, LDPE, or a blend thereof, the LLDPE can be a 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 disclosed and included herein.

[0044] 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. For example, in some embodiments, the first outer layer and the second outer layer each include an antiblock agent.

[0045] 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.

[0046] The multilayer film of the present invention can have several desirable properties in various embodiments. Without being bound by any theory, the specific structure of the multilayer film, including a thin core layer including a specific ethylene-based copolymer, can result in a multilayer film with high tear resistance properties. In some embodiments, the multilayer film of the present invention has a machine direction tear resistance of at least 2000g (or at least 2200g, or at least 2400g, or at least 2600g, or at least 2800g, or at least 3000g), or in the range of 2000g to 4000g, 2400g to 3900g, 2800g to 3800g, or 3000g to 3700g. The machine direction tear resistance can 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 have a machine direction tear resistance of at least 20.0 g / μm (or at least 22.0 g / μm, or at least 24.0 g / μm, or at least 26.0 g / μm, or at least 28.0 g / μm, or at least 30.0 g / μm), or in the range of 20.0 to 40.0 g / μm, 24.0 to 39.0 g / μm, 28.0 to 38.0 g / μm, or 30.0 to 37.0 g / μm. Machine direction tear resistance can be measured according to ASTM D1922-09.

[0047] Similarly, in some embodiments, the multilayer film has a lateral tear resistance of at least 2500 g (or at least 2600 g, or at least 2800 g, or at least 3000 g, or at least 3200 g, or at least 3300 g, or at least 3400 g), or in the range of 2500 g to 4000 g, 2800 g to 4000 g, 3000 g to 4000 g, or 3200 g to 4000 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 has a transverse tear resistance of 25.0 g / μm (or at least 27.0 g / μm, or at least 29.0 g / μm, or at least 31.0 g / μm, or at least 32.0 g / μm, or at least 33.0 g / μm, or at least 34.0 g / μm), or in the range of 25.0 to 40.0 g / μm, 28.0 to 40.0 g / μm, 30.0 to 40.0 g / μm, or 32.0 to 40.0 g / μm. Transverse tear resistance can be measured according to ASTM D1922-09.

[0048] In some embodiments, the multilayer film has a dart impact of greater than 700 grams or greater than 725 grams, where the dart impact is measured according to ASTM D1709-16a.

[0049] In some embodiments, the multilayer film has a thickness of from 50 to 150 microns, alternatively from 75 to 125 microns, alternatively from 90 to 110 microns.

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

[0051] 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. For example, in one embodiment, the multilayer film of the present invention is a heavy-duty shipping bag. 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.

[0052] Test Method density Density is measured in grams / cm according to ASTM D792. 3 (g / cm 3 or g / cc).

[0053] Melt index (I2 and I 10 ) Melt index (I2) is measured according to ASTM D-1238 at 2.16 kg and 190° C. Values ​​are reported in g / 10 min, which corresponds to grams dissolved per 10 minutes.

[0054] 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.

[0055] Dart Impact Dart impact is measured in accordance with Method A of ISO 7765-1, Standard Test Method for Determination of Impact Resistance of Plastic Films by Free Falling Dart Test Method. Method A uses a 38 mm ± 1 mm diameter hemispherical head dart dropped from a height of 0.66 m ± 0.01 m. This test method can be used for films that have an impact resistance requiring a mass of about 0.05 kg to about 2 kg to destroy the film. Results are expressed in grams (g). EXAMPLES

[0056] The following examples illustrate the present invention but are not intended to limit the scope of the invention.

[0057] The raw materials shown in Table 1 are used to prepare the inventive and comparative films discussed below. Unless otherwise noted, each resin is commercially available from The Dow Chemical Company.

[0058] [Table 1] * Commercially available from LyondellBasell

[0059] A 3-layer multilayer film and a 9-layer multilayer film are formed using the above materials. The 3-layer multilayer film is produced on a Collin coextrusion blown film line with a blow-up ratio (BUR) of 3.5 and an overall thickness of 100 μm. 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 2 below to prepare the multilayer films described in Table 4.

[0060] The nine layer multilayer films in Table 5 are produced on a nine layer Windmoller & Holscher VAREX II blown film line at a production rate of 200 kg / hr and a BUR of 2.1. The multilayer films in Table 5 were produced at 100 μm. All percent (%) values ​​provided in Table 5 are weight percent based on the total weight of each layer. The Windmoller & Holscher VAREX II blown film line is manufactured by Windmoller & Holscher Corporation. It consists of nine separate extruders (A-I) and is configured as shown in Table 3 below.

[0061] Table 4 reports the structure of a coextruded 3-layer multilayer film (A / B / A). The 3-layer film is a 100 micron film (45 / 10 / 45) with a first outer layer (45 microns), a core layer (10 microns), and a second outer layer (45 microns). Table 5 reports the structure of a coextruded 9-layer multilayer film (A / B / C / D / E / F / G / H / I). The 9-layer film is a 100 micron film (27 / 10 / 5.5 / 5.5 / 4 / 5.5 / 5.5 / 10 / 27).

[0062] [Table 2]

[0063] [Table 3]

[0064] [Table 4]

[0065] [Table 5]

[0066] The machine direction (MD) tear resistance, cross direction (CD) tear resistance, and dart impact are measured for each of the comparative and inventive films. The results are reported in Table 6 below. As can be seen from the results, the inventive films show surprisingly improved CD tear resistance and MD resistance over the comparative film. The dart impact of the inventive films is also improved or maintained compared to the comparative film, which is desirable. All of the inventive films contain ethylene-based polymers that are desirable for polyethylene recycle streams. The inventive films contain a thin core layer of an ethylene-based copolymer selected from the group consisting of ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, ethylene / vinyl acetate copolymer. This film structure with a thin core layer (e.g., 10% of the film for the inventive three-layer film) shows the surprising results of the excellent tear resistance properties that can be obtained by extrusion of a thin layer of ethylene-based copolymer in the film.

[0067] [Table 6]

[0068] 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.

[0069] 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, 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 greater than 90 wt% of an ethylene-based polymer, based on a total polymer weight of the core, the first core layer comprising an ethylene-based copolymer selected from the group consisting of ethylene / butyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl acrylate copolymer, and ethylene / vinyl acetate copolymer; the first core layer is 5 to 15% of the total thickness of the multilayer film; The multilayer film has a cross-direction tear resistance of at least 25.0 g / μm.

2. 10. The multilayer film of claim 1, wherein the ethylene-based copolymer comprises 80 to 100 weight percent of the first core layer, based on the total weight of the first core layer.

3. 10. The multilayer film of claim 1, wherein the ethylene-based polymer has a melt index (12) of less than 5 g / 10 min.

4. 10. The multilayer film of claim 1, wherein the ethylene-based copolymer is an ethylene / vinyl acetate copolymer comprising 9 to 28 weight percent vinyl acetate comonomer, based on the total weight of the ethylene / vinyl acetate copolymer.

5. 10. The multilayer film of claim 1, wherein the ethylene-based copolymer is an ethylene / butyl acrylate copolymer, an ethylene / ethyl acrylate copolymer, or an ethylene / methyl acrylate copolymer comprising 15 to 30 weight percent of an acrylate comonomer, based on the total weight of the ethylene-based copolymer.

6. 10. The multilayer film of claim 1, wherein the first outer layer and the second outer layer each comprise polyethylene having a density less than 0.930 g / cc and a melt index (12) less than 7 g / 10 min.

7. 10. The multilayer film of claim 1, wherein the core comprises 100% by weight of an ethylene-based polymer.

8. 10. The multilayer film of claim 1, wherein the multilayer film comprises at least five layers, including the first outer layer, the second outer layer, the first core layer, the second core layer, and a third core layer, the first core layer being disposed between the second core layer and the third core layer, and the second core layer and the third core layer independently comprise polyethylene having a density less than 0.930 g / cc and a melt index (I2) less than 7 g / 10 min.

9. The multilayer film of any one of claims 1 to 8, wherein the multilayer film comprises greater than 95 wt% of an ethylene-based polymer, based on the total weight of the multilayer film.