Flexible packaging film laminate and method for producing the laminate through thermal lamination

Abstract

Multilayer film embodiments are directed to films produced via thermal lamination without adhesives due to the use of tie layers comprising a blend of ethylene acrylate copolymer and anhydride-grafted ethylene alpha-olefin copolymer.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 62 / 867,979, filed on June 28, 2019, the entire disclosure of which is incorporated herein by reference.

[0002] Embodiments of the present disclosure generally relate to multilayer films, and more specifically to multilayer films and laminates manufactured without adhesives.

Background Art

[0003] Multilayer films can include films such as cast films or blown films that can be suitable for flexible packaging such as pouches or bags for various consumer products. Conventional laminates used in such applications typically include one or more layers of polyethylene terephthalate (PET) or biaxially oriented polypropylene (BOPP) laminated to a polyethylene sealant substrate. Such structures are printable, heat - resistant, and can withstand high - temperature sealing for good seal integrity, but such laminates cannot be recycled.

[0004] To address the recyclability issue, single - material polyethylene multilayer films have been introduced, but they typically lack the heat resistance required for use in high - temperature sealing high - speed packaging machines, which can result in printing distortion. Additionally or alternatively, such films may have limited rigidity, scratch resistance, tensile strength, and / or gloss. Further, the use of a laminating adhesive to enable adhesion to packaging inks may limit recyclability.

[0005] Accordingly, there is still a need for single - material polyethylene multilayer films that have suitable heat resistance without including a laminating adhesive.

Summary of the Invention

[0006] The present composition meets these needs by providing a film having a bonding layer that includes a blend having an ethylene acrylate copolymer and an anhydride-grafted ethylene α-olefin copolymer.

[0007] According to at least one embodiment of the present disclosure, a multilayer film is provided. The multilayer film includes a first layer, a second layer, and a bonding layer positioned between the first layer and the second layer, the bonding layer including a blend having an ethylene acrylate copolymer and an anhydride-grafted ethylene α-olefin copolymer. At least one of the first layer and the second layer is individually selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), aluminum, and combinations thereof.

[0008] These and other embodiments are described in more detail in the following mode for carrying out the invention.

Mode for Carrying Out the Invention

[0009] Here, specific embodiments of the present application will be described. However, the present disclosure may be embodied in different forms and should not be construed as limited to the embodiments described in the present disclosure. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the subject matter to those skilled in the art.

[0010] Definition The term "polymer" refers to a polymer compound prepared by polymerizing monomers, regardless of whether they are of the same or different types. Thus, the general term "polymer" usually encompasses the term "homopolymer", which is used to refer to a polymer prepared from only one type of monomer, and "copolymer", which refers to a polymer prepared from two or more different monomers. As used herein, the term "interpolymer" refers to a polymer prepared by the polymerization of at least two different types of monomers. Thus, the general term interpolymer includes copolymers and polymers prepared from three or more different monomers, such as terpolymers.

[0011] "Polyethylene" or "ethylene polymer" shall mean a polymer containing units derived from ethylene monomer in excess of 50 mol%. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). 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), medium density polyethylene (MDPE), and high density polyethylene (HDPE).

[0012] The term "LDPE" may also be referred to as "high pressure ethylene polymer" or "highly branched polyethylene" and is defined to mean that the polymer is partially or fully homopolymerized or copolymerized in an autoclave or tubular reactor at a pressure above 14,500 psi (100 MPa) using a free radical initiator such as a peroxide (see, for example, US 4,599,392, which is incorporated herein by reference). LDPE resins typically have a density in the range of 0.916 - 0.935 g / cm.

[0013] The term "LLDPE" includes resins made using Ziegler-Natta catalyst systems, as well as resins made using single-site catalysts, including but not limited to bis-metallocene catalysts (sometimes referred to as "m-LLDPE") and constrained geometry catalysts, and resins made using post-metallocene, molecular catalysts. LLDPE includes linear, substantially linear, or non-uniform polyethylene copolymers or homopolymers. LLDPE contains shorter chain branches than LDPE and includes substantially linear ethylene polymers further defined in U.S. Patent Nos. 5,272,236, 5,278,272, 5,582,923, and 5,733,155, homogeneous branched linear ethylene polymer compositions such as the compositions in U.S. Patent No. 3,645,992, non-uniformly branched ethylene polymers such as polymers prepared according to the process disclosed in U.S. Patent No. 4,076,698, and / or blends thereof (such as those disclosed in US3,914,342 or US5,854,045). LLDPE resins can be made by gas phase, liquid phase, or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

[0014] The term "MDPE" refers to polyethylene having a density of 0.926 to 0.945 g / cc. "MDPE" is typically made using a chromium or Ziegler-Natta catalyst, or using a single-site catalyst including but not limited to bis-metallocene catalysts and constrained geometry catalysts.

[0015] The term "HDPE" generally refers to polyethylene having a density greater than about 0.945 g / cc, prepared using a Ziegler-Natta catalyst, a chromium catalyst, or a single-site catalyst including but not limited to bis-metallocene catalysts and constrained geometry catalysts.

[0016] The term "ULDPE" generally refers to polyethylene having a density of 0.880 to 0.909 g / cc, prepared with Ziegler-Natta catalysts, including but not limited to single-site catalysts such as bis-metallocene catalysts and constrained geometry catalysts, as well as post-metallocene, molecular catalysts. As used herein, the term "propylene-based polymer" refers to a polymerization form that refers to a polymer containing more than 50% by weight of units derived from propylene monomers. This includes propylene homopolymers, random copolymer polypropylenes, impact copolymer polypropylenes, propylene / α-olefin interpolymers, and propylene / α-olefin copolymers. These polypropylene materials are generally known to those skilled in the art.

[0017] "Multilayer film" means any structure having a plurality of layers. For example, the multilayer structure may have 2, 3, 4, 5, or more layers. The multilayer film can be described as having layers designated by letters. For example, a three-layer structure having a core layer B and two outer layers A and C may be designated as A / B / C. Similarly, a structure having two core layers B and C and two outer layers A and D may be designated as A / B / C / D. Additionally, those skilled in the art will know that additional layers E, F, G, etc. can also be incorporated into this structure.

[0018] "Blend", "polymer blend", and similar terms mean a composition of two or more polymers. Such blends may or may not be miscible. Such blends may or may not be phase-separated. Such blends may or may not contain one or more domain configurations determined from transmission electron spectroscopy, light scattering, X-ray scattering, and any other methods known in the art. A blend is not a laminate, but one or more layers of a laminate may contain a blend. Such blends can be formed as dry blends, in situ (e.g., in a reactor), as melt blends, or using other techniques known to those skilled in the art.

[0019] Here, referring in detail to an embodiment of the multilayer film of the present disclosure, the multilayer film includes a first layer, a second layer, and a bonding layer positioned between the first layer and the second layer. The bonding layer includes a blend having an ethylene acrylate copolymer and an anhydride-grafted ethylene α-olefin copolymer. At least one of the first layer and the second layer is individually selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), aluminum, and combinations thereof.

[0020] In one embodiment, only one of the first layer and the second layer includes PP, PET, PE, PA, aluminum, and combinations thereof. In another embodiment, the first layer and the second layer may both be selected from the group consisting of PP, PET, PE, PA, aluminum, and combinations thereof. In yet another embodiment, the first layer or the second layer may include a PE sealant layer. The PE sealant layer may include a single-layer or multilayer, for example, a coextruded multilayer film having 2 to 11 layers. The PE sealant layer may include LDPE, LLDPE, ethylene acid copolymer, ionomer, ethylene vinyl acetate, polyamide, ethylene vinyl alcohol, or combinations thereof. In a further embodiment, at least one of the first layer and the second layer is uniaxially oriented or biaxially oriented.

[0021] Bonding layer The ethylene acrylate copolymer in the bonding layer blend may include various suitable compositions. In some embodiments, the bonding layer includes an ethylene acrylate copolymer. The ethylene acrylate copolymer is a polymerization reaction product of ethylene and one or more acrylate comonomers. Suitable ethylene acrylate copolymers may include ethylene (meth)acrylate (EMA), ethylene ethyl acrylate (EEA), and ethylene butyl acrylate (EBA). In certain embodiments, the ethylene acrylate copolymer includes ethylene (meth)acrylate.

[0022] The ethylene acrylate copolymer may have a density of 0.920 to 0.950 g / cc, or 0.925 to 0.945 g / cc. Further, the ethylene acid copolymer may have a melt index (I2) of 1.0 g / 10 min to 5 g / 10 min, 1.5 g / 10 min to 2.5 g / 10 min.

[0023] In one or more embodiments, the ethylene acrylate copolymer has an acrylate comonomer content of 5 to 40 wt%, 15 wt% to 40 wt%, or 20 wt% to 30 wt%. Conversely, in one or more embodiments, the ethylene acrylate copolymer has more than 50 wt% ethylene monomer, more than 60 wt% ethylene monomer, or more than 70 wt% ethylene monomer.

[0024] Various amounts of ethylene acrylate copolymer are contemplated within the blend. In one or more embodiments, the blend may include 50 to 90 wt% ethylene acrylate copolymer, or 60 to 90 wt%, 70 to 85 wt%, or 70 to 80 wt% ethylene acrylate copolymer.

[0025] The anhydride-grafted ethylene α-olefin copolymer within the tie layer blend may also include various suitable copolymer compositions. Examples of suitable α-olefins that may be either aliphatic or aromatic are C3-C 20 α-olefin, C3-C 16 α-olefin, or C3-C 10 α-olefin. In one or more embodiments, the α-olefin is a C3-C selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. 10 It may be an aliphatic α-olefin.

[0026] The anhydride-grafted ethylene-based polymer has a density of 0.880 to 0.930 g / cc, 0.900 to 0.930 g / cc, or 0.910 to 0.925 g / cc. In some embodiments, the anhydride-grafted ethylene-based polymer has a melt flow rate of 0.1 g / 10 min to 50 g / 10 min, or 0.5 g / 10 min to 20 g / 10 min, or 1.0 g / 10 min to 10 g / 10 min, or 2.0 to 5 g / 10 min.

[0027] Examples of the anhydride-grafted moiety include, but are not limited to, maleic anhydride, citraconic anhydride, 2-methylmaleic anhydride, 2-chloromaleic anhydride, 2,3-dimethylmaleic anhydride, bicyclo[2,2,1]-5-heptane-2,3-dicarboxylic anhydride, and 4-methyl-4-cyclohexene-1,2-dicarboxylic anhydride, bicyclo(2.2.2)oct-5-ene-2,3-dicarboxylic anhydride, lo-octahydronaphthalene-2,3-dicarboxylic anhydride, 2-oxa-1,3-diketospiro(4.4)nona-7-ene, bicyclo(2.2.1)hepta-5-ene-2,3-dicarboxylic anhydride, tetrahydrophthalic anhydride, norborn-5-ene-2,3-dicarboxylic anhydride, nadic anhydride, methyl nadic anhydride, himic anhydride, methyl himic anhydride, and x-methyl-bicyclo(2.2.1)hepta-5-ene-2,3-dicarboxylic anhydride. In one embodiment, the anhydride-grafted moiety includes maleic anhydride. The anhydride-grafted ethylene α-olefin copolymer can have an anhydride grafting level of 0.1 to 2.5 wt%.

[0028] Various amounts of the anhydride-grafted ethylene α-olefin copolymer are contemplated in the blend. The blend can include 5 to 45 wt% of the anhydride-grafted ethylene α-olefin copolymer. In further embodiments, the blend can include 5 to 20 wt% of the anhydride-grafted ethylene α-olefin copolymer, or 5 to 20 wt% of the anhydride-grafted ethylene α-olefin copolymer.

[0029] Optionally, the blend may further comprise an ethylene / α-olefin / non-conjugated diene interpolymer. The ethylene / α-olefin / non-conjugated diene interpolymer may comprise one or more interpolymers, where each ethylene / α-olefin / non-conjugated diene interpolymer comprises, in polymerized form, ethylene, an α-olefin, and a non-conjugated diene. In certain embodiments, the ethylene / α-olefin / non-conjugated diene interpolymer is a terpolymer.

[0030] Examples of suitable α-olefins, which may be aliphatic or aromatic, include C3-C 20 α-olefins, C3-C 16 α-olefins, or C3-C 10 α-olefins. In one or more embodiments, the α-olefin is a C3-C selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene. 10 It may be an aliphatic α-olefin. In one embodiment, the α-olefin is propylene.

[0031] Suitable examples of non-conjugated dienes include C4-C 40It contains non-conjugated dienes. Typical non-conjugated dienes include linear acyclic dienes such as 1,4-hexadiene and 1,5-heptadiene, branched-chain acyclic dienes such as 5-methyl-1,4-hexadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, 3,7-dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene, 5,7-dimethyl-1,7-octadiene, 1,9-decadiene, and mixed isomers of dihydromyrcene, monocyclic alicyclic dienes such as 1,4-cyclohexadiene, 1,5-cyclooctadiene, and 1,5-cyclododecadiene, polycyclic alicyclic condensed and bridged ring dienes such as tetrahydroindene and methyltetrahydroindene, and alkenyl, alkylidene, cycloalkenyl, and cycloalkylidene norbornenes such as 5-methylene-2-norbornene (MNB), 5-ethylidene-2-norbornene (ENB), 5-vinyl-2-norbornene, 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene, 5-(4-cyclopentenyl)-2-norbornene, and 5-cyclohexylidene-2-norbornene. In certain embodiments, the non-conjugated diene is preferably selected from the group consisting of ENB, dicyclopentadiene, 1,4-hexadiene, 7-methyl-1,6-octadiene, preferably ENB, dicyclopentadiene and 1,4-hexadiene, more preferably ENB and dicyclopentadiene, and even more preferably ENB.

[0032] In a further embodiment, the ethylene / α-olefin / non-conjugated diene interpolymer is an ethylene-propylene-diene interpolymer (EPDM), specifically, a terpolymer product of ethylene, propylene and ENB.

[0033] In ethylene / α-olefin / non-conjugated diene interpolymers, various amounts of each monomer are envisioned, but the interpolymer contains a majority amount of polymerized ethylene. In one or more embodiments, the ethylene / α-olefin / non-conjugated diene interpolymer contains 50 to 80 wt%, 55 to 75 wt%, or 60 to 70 wt% ethylene, based on the total weight of the ethylene / α-olefin / non-conjugated diene interpolymer. Similarly, the ethylene / α-olefin / non-conjugated diene interpolymer contains 15 to 45 wt%, 20 to 40 wt%, or 25 to 35 wt% propylene, based on the total weight of the ethylene / α-olefin / non-conjugated diene interpolymer. Further, the ethylene / α-olefin / non-conjugated diene interpolymer contains 0.1 to 10 wt%, 0.1 to 5 wt%, or 0.1 to 1 wt% non-conjugated diene, based on the total weight of the ethylene / α-olefin / non-conjugated diene interpolymer.

[0034] In one or more embodiments, the ethylene / α-olefin / non-conjugated diene interpolymer has a crystallinity of 7 to 20% when measured by differential scanning calorimetry. In further embodiments, the crystallinity is 8 to 18, 10 to 15, or 12 to 15.

[0035] Further, the ethylene / α-olefin / non-conjugated diene interpolymer may be characterized by a Mooney viscosity (ML 1+4 ) of 5 to 50, 10 to 40, or 15 to 30, where the Mooney viscosity (ML 1+4 ) is measured according to ASTM D1646.

[0036] The ethylene / α-olefin / non-conjugated diene interpolymer may have a weight average molecular weight (Mw) measured according to conventional gel permeation chromatography (GPC) of at least 90,000 g / mol, at least 100,000 g / mol, at least 110,000 g / mol, at least 120,000 g / mol, at least 200,000 g / mol, at least 220,000 g / mol, at least 240,000 g / mol, at least 260,000 g / mol, or at least 280,000 g / mol. Further, the ethylene / α-olefin / non-conjugated diene interpolymer may have a weight average molecular weight (Mw) of 500,000 g / mol or less, 450,000 g / mol or less, 400,000 g / mol or less, 250,000 g / mol or less, 200,000 g / mol or less, 150,000 g / mol or less.

[0037] Further, the ethylene / α-olefin / non-conjugated diene interpolymer may have a number average molecular weight (Mn) of 20,000 g / mol or more, 25,000 g / mol or more, or 30,000 g / mol or more. In one or more embodiments, the ethylene / α-olefin / non-conjugated diene interpolymer has a number average molecular weight (Mn) of 60,000 g / mol or less, 55,000 g / mol or less, 50,000 g / mol or less, 40,000 g / mol or less.

[0038] As described above, the ethylene / α-olefin / non-conjugated diene interpolymer may have a molecular weight distribution (MWD) of at least 2.5, where MWD = Mw / Mn. Further, the ethylene / α-olefin / non-conjugated diene interpolymer may have an MWD of 10.00 or less, further 9.50 or less, further 9.00 or less, or further 5 or less. In one embodiment, or in combination with any one or more of the embodiments described herein, the ethylene / α-olefin / non-conjugated diene interpolymer may have an MWD of 3.00 or more, 3.25 or more, or 3.50 or more.

[0039] The ethylene / α-olefin / non-conjugated diene interpolymer compound may be present in the tie layer blend in an amount of 1 wt% to 30 wt%, 2 wt% to 10 wt%, or 2 wt% to 5 wt%.

[0040] Furthermore, the blend may optionally contain a styrene composition. In one embodiment, the styrene composition is high impact polystyrene (HIPS), which is a styrene polymer containing a grafted rubber component. The rubber component is a blend comprising both a rubbery conjugated diene and styrene copolymer (rubber copolymer), or a blend of a rubber copolymer and a small amount of a rubbery conjugated diene homopolymer (rubber homopolymer). The conjugated diene of both rubbers is usually a 1,3-alkadiene, preferably butadiene, isoprene, or both butadiene and isoprene, most preferably butadiene. The conjugated diene copolymer rubber can be a styrene / butadiene (S / B) block copolymer. Polybutadiene is a desirable rubber homopolymer.

[0041] For the styrene composition in the blend, various amounts are contemplated. For example, the blend may contain 1 to 30 wt% styrene, or 5 to 20 wt% styrene, or 5 to 15 wt% styrene.

[0042] Overall, the tie layer blend may have a melt index of 1.2 to 8.0 dg / min and a density of 0.930 to 0.949 g / cc as measured according to ASTM D792.

[0043] Additional compositions and additives are also contemplated to be included in the tie layer. For example, the tie layer may include tackifiers such as rosins and their derivatives, terpenes and modified terpenes, aliphatic, alicyclic and aromatic resins (C5 aliphatic resins, C9 aromatic resins, and C5 / C9 aliphatic / aromatic resins), hydrogenated hydrocarbon resins and mixtures thereof, and terpene-phenol resins (TPR), which are often used with ethylene-vinyl acetate adhesives. One suitable hydrogenated hydrocarbon resin is Regalite R1125 available from Eastman Chemical.

[0044] Sealant layer Multilayer films of various embodiments may optionally include a sealant layer positioned on the innermost layer of the package closest to the packaged contents. Means are also provided for sealing or closing the package around the package product, such as by bringing two portions of the sealant layer together, or heat-sealing to the surface of another portion of the package, such as sealing a lid film to a thermoformed package part. The composition of the sealant layer is selected to affect the sealing ability of the inner layer, for example, to achieve high seal adhesion strength at the lowest possible seal temperature.

[0045] The sealant layer may include one or more ethylene acid copolymers having 0 to 70 mol% of total acid units neutralized with a cation source, a polyethylene plastomer having a density below 0.910 g / cc, and an ethylene-based polymer having a melting point Tm (DSC) of 108 °C or less.

[0046] Ethylene acid copolymers having 0 to 70 mol% of total acid neutralized with a cation source can be called ionomers. The ethylene acid copolymer is a polymerization reaction product of ethylene, a monocarboxylic acid, and a softening comonomer. The monocarboxylic acid can be, for example, acrylic acid, methacrylic acid, or a combination thereof. In various embodiments, the monocarboxylic acid is present in an amount of 1 wt% to 25 wt%, 1 wt% to 20 wt%, or 5 wt% to 15 wt% based on the total weight of the monomers present in the ethylene acid copolymer. In various embodiments, the ethylene content of the ethylene acid copolymer is greater than 50 wt% or greater than 60 wt%. For example, the ethylene content of the ethylene acid copolymer is 50 wt% to 95 wt%, 50 wt% to 90 wt%, 50 wt% to 85 wt%, or 60 wt% to 80 wt%.

[0047] In various embodiments, the ethylene acid copolymer includes a softening comonomer selected from the group consisting of vinyl esters, alkyl vinyl esters, and alkyl (meth) acrylates. The softening comonomer can be present in an amount of 1 wt% to 40 wt% or 1 wt% to 30 wt% based on the total weight of the monomers present in the ethylene acid copolymer. In some embodiments, the softening comonomer is an alkyl acrylate. Suitable examples of alkyl acrylates include, but are not limited to, ethyl acrylate, methyl acrylate, n-butyl acrylate, isobutyl acrylate, or a combination thereof. In various embodiments, the alkyl acrylate has an alkyl group having 1 to 8 carbons.

[0048] Ethylene acid copolymers can be prepared by standard free radical copolymerization methods using high pressure and continuous operation. The monomers are supplied into the reaction mixture in a ratio related to the activity of the monomers and the amount desired to be incorporated. In this way, a uniform and nearly random distribution of monomer units along the chain is achieved. Unreacted monomers can be recycled. Additional information on the preparation of ethylene acid copolymers, including the softening copolymer, can be found in U.S. Patent No. 3,264,272 and U.S. Patent No. 4,766,174, each of which is hereby incorporated by reference in its entirety.

[0049] Ethylene acid copolymers can be used to produce ionomers by treatment with a cation source. The cation source can be a monovalent or divalent cation source including, but not limited to, formates, acetates, hydroxides, nitrates, carbonates, and bicarbonates. In various embodiments, the ethylene acid copolymer can be treated with one or more cations of magnesium, sodium, or zinc. In embodiments, 0 to 70 mol%, 1 to 70 mol%, 5 to 60 mol%, or 10 to 55 mol% of the total acid units of the ethylene acid copolymer are neutralized.

[0050] In some embodiments, the ionomer has a density of 0.930 g / cc to 0.980 g / cc, 0.940 g / cc to 0.970 g / cc, or 0.950 g / cc to 0.960 g / cc. In one or more embodiments, the ionomer has an MFR of 2 g / 10 min to 12 g / 10 min, 3.5 g / 10 min to 10 g / 10 min, or 5 g / 10 min to 8 g / 10 min. Commercially available ionomers include those available under the trade name SURLYN® from E. I. du Pont de Nemours and Company.

[0051] In light of the present disclosure, percent neutralization data is presented using the assumption that each cation reacts with the maximum number of carboxylic acid groups calculated from its ionic charge. That is, for example, Mg 2+ and Zn2+ reacts with two carboxylic acid groups and Na + is assumed to react with one.

[0052] In some embodiments, the sealant layer comprises a linear low density polyethylene plastomer. The polyethylene plastomer can include resins made using single site catalysts such as metallocenes and constrained geometry catalysts. The polyethylene plastomer has a density below 0.910 g / cc. The density can be, for example, 0.885 - 0.910 g / cc, 0.895 - 0.910 g / cc, 0.900 - 0.910 g / cc, 0.905 - 0.910 g / cc. In some embodiments, the polyethylene plastomer has a density of 0.885 - 0.907 g / cc.

[0053] In some embodiments, the polyethylene plastomer has a melt flow rate (MFR) of up to 20 g / 10 min. All individual values and subranges up to 20 g / 10 min are included herein and disclosed herein. For example, the polyethylene plastomer can have a melt index up to an upper limit of 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 g / 10 min. In certain aspects of the invention, the polyethylene plastomer has an MFR with a lower limit of 0.5 g / 10 min. One factor in specifying the melt index of the polyethylene plastomer is whether the sealant layer is manufactured as a blown film or as a cast film.

[0054] Examples of polyethylene plastomers that can be used in the sealant layer include those commercially available from The Dow Chemical Company under the name AFFINITY™, including, for example, AFFINITY™ PF7266, AFFINITY™ PL 1881G, and AFFINITY™ PF1140G.

[0055] In yet other embodiments, the sealant layer comprises an ethylene polymer having a melting point Tm (DSC) of 108 °C or less. In one embodiment, the ethylene polymer is linear low density polyethylene (LLDPE). Linear low density polyethylene has a density of 0.930 g / cc (cm 3 ) or less. All individual values and subranges of 0.930 g / cc or less are included herein and disclosed herein. For example, the density of linear low density polyethylene can be from an upper limit of 0.928, 0.925, 0.920, or 0.915 g / cc. In some embodiments, linear low density polyethylene has a density of 0.870 g / cc or more. All individual values and subranges from 0.870 to 0.930 g / cc are included herein and disclosed herein.

[0056] In some embodiments, the ethylene polymer has a peak melting point of 108 °C or less, preferably 70 to 108 °C, more preferably 70 to 99 °C.

[0057] The melt index of the ethylene polymer in the sealant layer can depend on many factors, including whether the film is a blown film or a cast film. In embodiments where the film is a blown film, the ethylene polymer has an MFR of 2.0 g / 10 min or less. All individual values and subranges from 2.0 g / 10 min are included herein and disclosed herein. For example, the ethylene polymer can have a melt index from an upper limit of 2.0, 1.7, 1.4, 1.1, or 0.9 g / 10 min or from a lower limit of 0.1, 0.2, 0.3, or 0.4 g / 10 min.

[0058] In other embodiments, the film can be a cast film. In such embodiments, the ethylene polymer has an MFR of 2.0 g / 10 min or more. All individual values and sub-ranges exceeding 2.0 g / 10 min are included herein and disclosed herein. For example, the ethylene polymer can have a melt index from a lower limit of 2.0, 3.0, 4.0, 5.0, 6.0, or 10 g / 10 min. In some embodiments, the ethylene polymer for cast film applications can have an upper limit melt index of 15 g / 10 min. In some embodiments, depending on the other components in the multilayer film, the ethylene polymer in the sealant layer for cast film applications can have an MFR of less than an upper limit of 2.0 g / 10 min. In some embodiments, the ethylene polymer in the sealant layer for cast film applications can have a melt flow rate (MFR) of 0.1 - 2.0 g / 10 min, or 0.5 - 2.0 g / 10 min. All individual values and sub-ranges of 0.1 - 2.0 g / 10 min are included herein and disclosed herein.

[0059] Examples of ethylene polymers that can be used in the sealant layer include those commercially available from The Dow Chemical Company under the name ELITE™ AT, including, for example, ELITE™ AT 6101, ELITE™ AT 6202, ELITE™ AT 6410.

[0060] Multilayer film The multilayer film may be formed and oriented (e.g., biaxially oriented) by any suitable process. Information on these processes can be found, for example, in references such as the Kirk Othmer Encyclopedia, the Modern Plastics Encyclopedia, or the Wiley Encyclopedia of Packaging Technology, 2d edition, A.L. Brody and K.S. Marsh, Eds., Wiley-Interscience (Hoboken, 1997). For example, the multilayer film may be formed by dip coating, film casting, sheet casting, solution casting, compression molding, injection molding, lamination, melt extrusion, blow film including circular blow film, extrusion coating, tandem extrusion coating, or any other suitable procedure. In some embodiments, the film is formed by a melt extrusion, melt coextrusion, melt extrusion coating, or tandem melt extrusion coating process. In some embodiments, the film is formed by thermal lamination or extrusion lamination and coating. Suitable orientation processes include tenter frame technology and machine direction orientation (MDO) technology.

[0061] Optionally, in some embodiments, the multilayer structure may include one or more additional layers, such as one or more core layers and one or more additional tie layers. For example, such additional layers may be positioned between the outer layer and the sealant layer. In one particular embodiment, the multilayer structure may include an outer layer, a core layer, a tie layer, and a sealant layer, and the tie layer is disposed between the core layer and the sealant layer. In some other embodiments, the multilayer structure may include an outer layer, a first tie layer, a core layer, a second tie layer, and a sealant layer, the first tie layer is disposed between the outer layer and the core layer, and the second tie layer is disposed between the core layer and the sealant layer. In some of such embodiments, the outer layer may include HDPE, and the core layer may include biaxially oriented polyethylene (BOPE) having a density of 0.910 to 0.940 g / cc. Other structures are contemplated.

[0062] Further, in a further embodiment, the multilayer film consists essentially of an ethylene-based polymer. As used herein, "consists essentially of" means that the multilayer film may contain other additives, but is limited to an ethylene-based polymer. In one or more embodiments, the multilayer film may comprise at least 90 wt% ethylene-based polymer, at least 93 wt% ethylene-based polymer, at least 95 wt% ethylene-based polymer, at least 97 wt% ethylene-based polymer, or at least 99 wt% ethylene-based polymer.

[0063] It should be understood that any of the layers within the multilayer films of the various embodiments described herein may further comprise one or more additives known to those skilled in the art, such as antioxidants, UV stabilizers, heat stabilizers, slip agents, antiblocking agents, pigments or colorants, processing aids, crosslinking catalysts, flame retardants, fillers, and foaming agents.

[0064] In the various embodiments described herein, the multilayer film is a laminate that does not include solvent-based adhesives, solventless adhesives, and aqueous lamination adhesives. As described above, the multilayer films described herein are provided with a unique combination of heat resistance, high rigidity, and gloss without using an adhesive. Additionally, in a further embodiment, the multilayer film does not include a primer layer disposed between the first and second layers and the bonding layer.

[0065] Article In various embodiments, the multilayer films disclosed herein can be used to form articles such as packaging. Such articles can be formed from any of the multilayer films described herein. Examples of packaging that can be formed from the multilayer films of various embodiments can include flexible packaging, pouches, sachets, stand-up pouches, and off-the-shelf packaging or pouches. In some embodiments, the multilayer films described herein can be used for food packaging such as packaging for meat, cheese, cereal, nuts, juice, sauce, and the like. Such packaging can be formed using techniques known to those of skill in the art based on the teachings herein and based on the particular use of the packaging (e.g., type of food, amount of food, etc.).

[0066] Test Methods The test methods include the following. Density Samples for density measurement were prepared according to ASTM D4703 and reported in grams per cubic centimeter (g / cc or g / cm 3 ) units. The measurement was performed within 1 hour of sample compression using ASTM D792, Method B.

[0067] Melt Index (I2) The melt index (I2) was measured according to ASTM D-1238 at 190 °C and 2.16 kg. The value was reported in g / 10 min, which corresponds to the grams eluted per 10 minutes.

[0068] Heat Seal Strength The heat seal strength, or seal strength, was measured according to ASTM F1921. The value is reported in N / 25 mm.

[0069] Bond Strength In accordance with ASTM F904-91, the bond strength was measured using a Zwick tensile testing machine at a tensile speed of 250 mm / min and a 25 mm wide strip. The tensile testing machine is equipped with gripper fixtures (holding the sample in a T-shape) to hold and then separate the two ends of a sample that is partially delaminated or partially peeled. The upper gripper connected to the crosshead is driven in the tensile direction to measure the force or bond strength required between two adjacent layers of the multilayer sample. The maximum force and average force results are calculated from five measurements and recorded in units of Newton (N / 25 mm strip).

[0070] Leakage test In accordance with ASTM D3078-02, the leakage test was a test conducted on a pillow pouch. The leakage test apparatus supplies negative pressure, submerges the inflated pillow pouch in water, and enables the detection of any leakage by the appearance of air bubbles emerging from the inflated pouch using a method. The pouch samples were tested under the following pressure conditions listed in Table 1.

Table 1

Examples

[0071] The following examples illustrate the features of the present disclosure and are not intended to limit the scope of the present disclosure.

[0072] Commercially available polymers used The following compositions listed in Table 2 were included in the multilayer examples discussed below. All materials were obtained from The Dow Chemical Company (Midland, MI).

Table 2

[0073] Example 1 The film 1 of the present invention is a 50-μm single-layer film using BYNEL® 21E961 and was used to study adhesion between various substrates or layers, as seen in Table 3. Similarly, Comparative Films 1 and 2 are 50-μm single-layer films containing a blend of Elvaloy AC 1224 and BYNEL® 41E710 and ELITE™ 5400, respectively.

Table 3

[0074] Next, Film 1 of the present invention and Comparative Films 1 and 2 were sandwiched between two substrates to be evaluated to ensure consistency in evaluating the adhesion strength between the film and the substrate.

[0075] The resulting sandwich structure was passed through a tabletop hot roll laminator (Cheminstruments) at 160°C and 60 PSI. The resulting laminate was manually delaminated on one side to evaluate the bonding strength. When corona treatment was utilized, corona treatment up to 38 dynes was performed prior to thermal lamination. All experiments were conducted at a roller speed setting of 2, and as shown in Table 4, the speed during calibration was as follows.

Table 4

[0076] The results of the force required to separate one side of the substrate from Film 1 of the present invention are provided in Table 5. The results of the force required to separate one side of the substrate from Comparative Film 1 (Elvaloy AC 1224) and Comparative Film 2 (BYNEL® 41E710 blended with ELITE™ 5400) are provided in Tables 6 and 7, respectively. All bonding strengths are measured in Newtons (N). The values of the bonding strength are the average of five tests.

Table 5

[0077] The results demonstrate that the film 1 of the present invention can adhere well to BOPP, printed BOPP, BOPET, printed PET, and BOPA. However, the highest performance is observed with aluminum where a force of 2.94 N is measured. For general applications, an adhesion strength of 2 N should be sufficient. Therefore, BYNEL® 21E961 can provide bonding strength to many different substrates at approximately 2 N (BOPA, aluminum, BOPP).

[0078] Compared to BYNEL® 21E961, which is a blend of an ethylene acrylate copolymer and an anhydride-grafted ethylene α-olefin copolymer, provided below are the bonding strengths for Comparative Films 1 and 2, which contain an ethylene acrylate copolymer (Elvaloy AC 1224) and an anhydride-grafted ethylene α-olefin copolymer (BYNEL® 41E710 blended with ELITE™ 5400), respectively. As shown in Tables 6 and 7, the bonding strengths of Comparative Films 1 and 2 were evaluated on various substrates at a temperature of 160°C.

Table 6

Table 7

[0079] As shown in Table 7, the bonding strength of Comparative Film 2 containing an anhydride-grafted ethylene α-olefin copolymer was low. Referring to Table 6, Comparative Film 1 (Elvaloy AC 1224) adhered well to PET, PA, and P.PET, but did not adhere to BOPP. Only the film 1 of the present invention containing a blend of an ethylene acrylate copolymer and an anhydride-grafted ethylene α-olefin copolymer was able to synergistically achieve good adhesion to BOPP as well as good adhesion to other substrates.

[0080] Example 2 To further demonstrate the adhesion performance, three side-sealed pillow pouch structures were manufactured. The pillow pouches had dimensions of 80 mm x 80 mm and had a 5 mm edge seal only on three sides. All the pouches were heat-sealed using a Jade PFS-600 impulse sealer with a temperature knob set at 3. The pouches included the following layer structures listed in Table 8 below. [Table 8]

[0081] The pouches of the present invention and Comparative Pouch 2 were manufactured by the experimental thermal lamination procedure listed above. The thermal lamination was carried out in a two-step process, i.e., applying BYNEL® 21E961 or NUCREL to the PET layer and then applying ELITE™ 5401G.

[0082] When performing a qualitative visual analysis of the pouches, Comparative Pouch 2 had many wrinkles on the surface because NUCREL® 31001 had a low adhesion strength to PET, i.e., only about 0.3 N to 0.5 N. This decrease in adhesion strength resulted in delamination, which was demonstrated in the wrinkled layer. The pouches of the present invention, including the BYNEL® 21E961 bonding layer, exhibited a similar wrinkle level to Comparative Pouch 1, which is a conventional pouch laminated with an adhesive, because BYNEL® 21E961 adheres well to PET.

[0083] Then, all three pouches in Table 8 were subjected to a leak test. As shown in Table 9 below, the pouches of the present invention were the only pouches that passed all the pressure conditions of the leak test. [Table 9]

[0084] As shown in Table 10, the thermally laminated pouch of the present invention surprisingly showed improved leak test performance compared to Comparative Pouch 1 using a lamination adhesive. This result further agrees with the seal strength results shown in Table 11 below, which is equivalent to or better than laminates manufactured by ordinary conventional methods such as Comparative Pouch 1. As shown, the pouch of the present invention has a seal strength much greater than that of Comparative Pouch 1 at temperatures of 110°C or higher.

Table 10

[0085] It will be apparent that modifications and changes can be made without departing from the scope of the disclosure as defined in the appended "Claims". More specifically, while some aspects of the disclosure are recognized herein as preferred or particularly advantageous, the disclosure is not necessarily intended to be limited to these aspects. The invention described in the original claims of the present application is appended below. [1] A multilayer film, comprising a first layer, a second layer, and a bonding layer positioned between the first layer and the second layer, the bonding layer comprising a blend having an ethylene acrylate copolymer and an anhydride-grafted ethylene α-olefin copolymer, wherein at least one of the first layer and the second layer is individually selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), aluminum, and combinations thereof. [2] The multilayer film according to [1], wherein both the first layer and the second layer are individually selected from the group consisting of PP, PET, PE, PA, aluminum, and combinations thereof. [3] The multilayer film according to either [1] or [2], wherein at least one of the first layer and the second layer is uniaxially or biaxially oriented. [4] The multilayer film according to any one of [1] to [3], wherein the first layer or the second layer comprises a PE sealant layer. [5] The multilayer film according to any one of [1] to [4], wherein the blend further comprises an ethylene / α-olefin / non-conjugated diene interpolymer. [6] The multilayer film according to any one of [1] to [5], wherein the blend further comprises styrene. [7] The multilayer film according to any one of [1] to [6], wherein the ethylene acrylate copolymer comprises ethylene (meth)acrylate. [8] The multilayer film according to any one of [1] to [7], wherein the ethylene acrylate copolymer has an acrylate comonomer content of 5 to 40% by weight. [9] The multilayer film according to any one of [1] to [8], wherein the blend has a melt index of 1.2 to 8.0 dg / min.

[10] The multilayer film according to any one of [1] to [9], wherein the blend has a density of 0.930 to 0.949 g / cc when measured according to ASTM D792.

[11] The multilayer film according to any one of [1] to

[10] , wherein the blend comprises 50 to 90% by weight of an ethylene acrylate copolymer.

[12] The multilayer film according to any one of [1] to

[11] , wherein the blend contains 5 to 45% by weight of an anhydride-grafted ethylene α-olefin copolymer.

[13] The multilayer film according to any one of [1] to

[12] , wherein the anhydride-grafted ethylene α-olefin copolymer has an anhydride grafting level of 0.1 to 2.5% by weight.

[14] The multilayer film according to any one of [1] to

[13] , wherein the multilayer film is formed by thermal lamination.

[15] The multilayer film according to any one of [1] to

[14] , wherein the multilayer film does not include a primer layer disposed between the first and second layers and the bonding layer.

[16] An article comprising the multilayer film according to any one of [1] to

[15] , wherein the article is a flexible packaging article.

Claims

1. A multilayer film, a first layer, a second layer, and a bonding layer positioned between the first layer and the second layer, the bonding layer comprising a blend having an ethylene acrylate copolymer and an anhydride-grafted ethylene α-olefin copolymer, wherein at least one of the first layer and the second layer is individually selected from the group consisting of biaxially oriented polyamide (BOPA), aluminum, biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET), and combinations thereof, the blend having a density of 0.930 to 0.949 g / cc when measured according to ASTM D792, a multilayer film.

2. The multilayer film according to claim 1, wherein both the first layer and the second layer are individually selected from the group consisting of biaxially oriented polyamide (BOPA), aluminum, biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET), and combinations thereof.

3. The multilayer film according to claim 1 or 2, wherein at least one of the first layer and the second layer is uniaxially or biaxially oriented.

4. The multilayer film according to claim 1, wherein the first layer or the second layer comprises a PE sealant layer.

5. The multilayer film according to any one of claims 1 to 4, wherein the blend further comprises an ethylene / α-olefin / non-conjugated diene interpolymer.

6. The multilayer film according to any one of claims 1 to 5, wherein the blend further comprises styrene.

7. The multilayer film according to any one of claims 1 to 6, wherein the ethylene acrylate copolymer contains ethylene (meth) acrylate.

8. The multilayer film according to any one of claims 1 to 7, wherein the ethylene acrylate copolymer has an acrylate comonomer content of 5 to 40% by weight.

9. The multilayer film according to any one of claims 1 to 8, wherein the blend has a melt index of 1.2 to 8.0 dg / min.

10. The multilayer film according to any one of claims 1 to 9, wherein the blend contains 50 to 90% by weight of an ethylene acrylate copolymer.

11. The multilayer film according to any one of claims 1 to 10, wherein the blend contains 5 to 45% by weight of an anhydride-grafted ethylene α-olefin copolymer.

12. The multilayer film according to any one of claims 1 to 11, wherein the anhydride-grafted ethylene α-olefin copolymer has an anhydride grafting level of 0.1 to 2.5% by weight.

13. The multilayer film according to any one of claims 1 to 12, wherein the multilayer film is formed by thermal lamination.

14. The multilayer film according to any one of claims 1 to 13, wherein the multilayer film does not include a primer layer disposed between the first and second layers and the bonding layer.

15. An article comprising the multilayer film according to any one of claims 1 to 14, wherein the article is a flexible packaging article.

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