WO2020068497A1 - Multilayer films and methods of making the same - Google Patents

Abstract

Disclosed herein are multilayer films including polyethylene polymers and hydrocarbon resins and methods for making such films.

Description

MULTILAYER FILMS AND METHODS OF MAKING THE SAME

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit to Serial No. 62/735,960, filed September 25, 2018, the disclosure of which is hereby incorporated by reference in its entirety.

FIELD OF THE INVENITON

[0002] This invention relates to films, and in particular, to multilayer films comprising polyethylene polymers and hydrocarbon resins, and methods for making such films.

BACKGROUND OF THE INVENTION

[0003] Coextruded blown films are widely used in a variety of packaging as well as other applications. Film properties are often subject to the combined effect of the coextrusion process conditions and polymer compositions selected for the different layers. In order to address requirements of particular end-uses, film producers have to accordingly highlight certain film properties while balancing between mechanical properties such as stiffness and impact strength, to ensure package integrity without distortion and rupture, and optical properties such as clarity and haze, which impact the attractiveness of the packaging and visual inspection of the goods at the point of sale. Good sealing performance under common heat sealing conditions and, for some applications, barrier to moisture, light and/or oxygen transmission are also desired.

[0004] Laminates, prepared from a flexible film structure comprising a polyethylene sealant film adhered to a substrate film commonly made of polyester (PET), biaxially oriented polypropylene (BOPP), or biaxially oriented polyamide (BOPA), are commonly employed to provide barrier solutions. Among others, polyamide, while well-known for its good oxygen and aroma barrier as well as favored mechanical properties including both toughness and stiffness, is difficult to be effectively recycled. In response, there has recently arisen a growing trend to provide“pure” polyethylene solutions, i.e. by laminating a polyethylene sealant to a substrate also made of polyethylene. Based on a single class of resins, such laminates can be conveniently recycled to improve sustainability and can deliver material cost-effectiveness by virtue of the more inexpensive polyethylene polymers. However, the“pure” polyethylene solutions usually tend to weaken other properties. For example, barrier films made of high density polyethylene (HDPE) have limited use because properties of such films, including impact strength, tear strength, and sealing temperature, are inferior to those of lower density polyethylene (LDPE). On the other hand, introduction of LDPE into barrier films to offset the abovementioned defect is in turn likely to compromise barrier performance provided by HDPE. Moreover, flexibility in tailoring barrier levels is desired to satisfy diverse end-uses but has been restricted by the available selection of film design with polyethylene and other barrier materials, such as polyamide. Therefore, film manufacturers have long been challenged to better accommodate the conflict between current solutions without strengthening one property at the expense of impairing the other.

[0005] WO 2018/071250 relates to oriented films comprising linear low density polyethylene polymer and having improved balance of properties including improved machine direction tear strength. This oriented polymer film has at least one layer comprising 50 to 100 wt% of an ethylene-based polymer. This MDO polymer film has a normalized MD Elmendorf Tear (ASTM D-1922) of at least 40 g/pm. In certain embodiments, this MDO polymer film does not tear when MD Elmendorf Tear is measured according to ASTM D- 1922.

[0006] WO 2016/135213 provides laminated film structures comprising one first film being laminated to a second film and whereby this laminated film structures are based on polyethylene only, i.e. polymers other than polyethylene are substantially absent and wherein the first film is an MDO film, which can be down-gauged to a film thickness below 30 pm, preferably to 25pm and below, e.g. to a film thickness of 20pm.

[0007] WO 2016/097951 discloses a multilayer film having Machine Direction Orientation (MDO) prepared by first co-extruding a multilayer film, then stretching the multilayer film in the machine direction at a temperature lower than the melting point of the polyethylene resin that is used to prepare the film. At least one layer of this film is a first polyethylene composition having a density of from about 0.94 to about 0.97 g/cc and at least one second layer is prepared from a polyethylene composition having a lower density than the first polyethylene composition.

[0008] U.S. Patent No. 7,794,848 provides a multilayer film and a method of making the film. In this method a multilayer film is post-oriented uniaxially in the machine direction resulting in a film that has a water vapor transmission rate of less than 2.5 g-mil/m²-day and an oxygen transmission rate of less than 1.5 cm²-mil/m²-day.

[0009] As discussed above, numerous efforts have been made to explore alternative film designs with well-balanced overall performance, yet room for improvement remains. Applicant has found that such objective can be achieved by applying a particular amount of hydrocarbon resin as described herein in the core layer of a polyethylene film of at least three layers. Presence of the hydrocarbon resin can lead to significant reduction in oxygen transmission rate, accompanied by increase in puncture resistance. Furthermore, the inventive film can establish a different set of favored film performance after machine direction orientation than that achievable before machine direction orientation by increasing water vapor barrier level, optical performance, stiffness, puncture resistance, as well as hot tack peak and window. Therefore, convenience and flexibility in modifying film performance, particularly pending machine direction orientation of the inventive film, can be expected to enhance certain properties appealing to specific applications, in parallel with delivering a well-accomplished overall performance profile.

SUMMARY OF THE INVENTION

[0010] Provided are multilayer films comprising polyethylene polymers and hydrocarbon resins, and methods for making such films.

[0011] Thus, in one aspect, the present disclosure provides a multilayer film comprising two outer layers and a core layer between the two outer layers, each layer comprising at least about 50 wt% of a polyethylene polymer, based on total weight of polymer in the layer, wherein the polyethylene has a density of about 0.910 to about 0.945 g/cm³, a melt index (MI), I2_.16, of about 0.1 to about 15 g/lO min, a molecular weight distribution (MWD) of about 1.5 to about 5.5, and a melt index ratio (MIR), I21_.6/I2_.16, of about 10 to about 100; wherein the core layer further comprises from about 7 to about 15 wt% of a hydrocarbon resin, based on total weight of polymer in the core layer, wherein the hydrocarbon resin is selected from the group consisting of an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, and mixtures or combinations thereof.

[0012] In a further aspect, the present disclosure provides a method for making a multilayer film, the method comprising the steps of: (a) preparing two outer layers and a core layer between the two outer layers, each layer comprising at least about 50 wt% of a polyethylene polymer, based on total weight of polymer in the layer, wherein the polyethylene polymer has a density of about 0.910 to about 0.945 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR, I21_.6/I2_.16, of about 10 to about 100; wherein the core layer further comprises from about 7 to about 15 wt% of a hydrocarbon resin, based on total weight of polymer in the core layer, wherein the hydrocarbon resin is selected from the group consisting of an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, and mixtures or combinations thereof; and (b) forming a film comprising each of the layers of step (a).

[0013] Often, the multilayer film described herein or made according to any method disclosed herein may have at least one of the following properties at a film thickness of about 130 pm: (i) a maximum puncture force of at least about 140 N; and/or (ii) an oxygen transmission rate (OTR) of about 100 cm³/(m²-day) or less.

[0014] Alternatively or additionally, the multilayer film is a machine direction oriented (MDO) film. Preferably, the multilayer film may have at least one of the following properties at a film thickness of about 30 pm: (i) a haze of at about 5% or less; (ii) a gloss at 45° of at least about 75 or more; (iii) an average 1% Secant Modulus of at least about 1150 or more; (iv) a maximum puncture force of at least about 45 N; (v) a water vapor transmission rate (WVTR) of at least about 6 g/(m²-day) or less; and/or (vi) a hot tack force of at least about 10 N/30 mm at a sealing temperature of l40°C.

[0015] Also provided are laminates comprising a substrate comprising the multilayer films described herein or made according to any method disclosed herein and seals comprising such multilayer films or laminates.

BRIEF DESCRIPTION OF THE DRAWING

[0016] The Figure depicts hot tack forces over a range of sealing temperatures for the samples in Example 2.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0017] Various specific embodiments, versions of the present invention will now be described, including exemplary embodiments and definitions that are adopted herein. While the following detailed description gives specific exemplary embodiments, those skilled in the art will appreciate that these embodiments are exemplary only, and that the present invention can be practiced in other ways. Any reference to the“invention” may refer to one or more, but not necessarily all, of the present inventions defined by the claims. The use of headings is for purposes of convenience only and does not limit the scope of the present invention.

[0018] As used herein, a“polymer” may be used to refer to homopolymers, copolymers, interpolymers, terpolymers, etc. A“polymer” has two or more of the same or different monomer units. A“homopolymer” is a polymer having monomer units that are the same. A “copolymer” is a polymer having two or more monomer units that are different from each other. A“terpolymer” is a polymer having three monomer units that are different from each other. The term“different” as used to refer to monomer units indicates that the monomer units differ from each other by at least one atom or are different isomerically. Accordingly, the definition of copolymer, as used herein, includes terpolymers and the like. Likewise, the definition of polymer, as used herein, includes copolymers and the like. Thus, as used herein, the terms “polyethylene,”“ethylene polymer,”“ethylene copolymer,” and“ethylene based polymer” mean a polymer or copolymer comprising at least 50 mol% ethylene units (preferably at least 70 mol% ethylene units, more preferably at least 80 mol% ethylene units, even more preferably at least 90 mol% ethylene units, even more preferably at least 95 mol% ethylene units or 100 mol% ethylene units (in the case of a homopolymer)). Furthermore, the term“polyethylene composition” means a composition containing one or more polyethylene components.

As used herein, when a polymer is referred to as comprising a monomer, the monomer is present in the polymer in the polymerized form of the monomer or in the derivative form of the monomer.

[0019] As used herein, when a polymer is said to comprise a certain percentage, wt%, of a monomer, that percentage of monomer is based on the total amount of monomer units in the polymer.

[0020] For purposes of this invention and the claims thereto, an ethylene polymer having a density of 0.910 to 0.940 g/cm³ is referred to as a“low density polyethylene” (LDPE); an ethylene polymer having a density of 0.890 to 0.930 g/cm³, typically from 0.910 to 0.930 g/cm³, that is linear and does not contain a substantial amount of long-chain branching is referred to as“linear low density polyethylene” (LLDPE) and can be produced with conventional Ziegler- Natta catalysts, vanadium catalysts, or with metallocene catalysts in gas phase reactors, high pressure tubular reactors, and/or in slurry reactors and/or with any of the disclosed catalysts in solution reactors (“linear” means that the polyethylene has no or only a few long-chain branches, typically referred to as a g' vis of 0.97 or above, preferably 0.98 or above); and an ethylene polymer having a density of more than 0.940 g/cm³ is referred to as a“high density polyethylene” (HDPE).

[0021] As used herein,“core” layer,“outer” layer, and“inner” layer are merely identifiers used for convenience, and shall not be construed as limitation on individual layers, their relative positions, or the laminated structure, unless otherwise specified herein.

[0022] As used herein,“first” polyethylene,“second” polyethylene,“third” polyethylene, “fourth” polyethylene, and“fifth” polyethylene are merely identifiers used for convenience, and shall not be construed as limitation on individual polyethylene, their relative order, or the number of polyethylene polymers used, unless otherwise specified herein.

[0023] As used herein, stretch ratio through a machine direction (MD) orientation unit is the ratio of film length before MD orientation to the film length after MD orientation. This is stated, for example, as a stretch ratio of 4, where 4 represents the film length after MD orientation relative to a film of unit length before MD orientation, i.e., the film has been stretched to 4 times the original length. Orientation refers to the alignment of polymer chains in the film.

[0024] As used herein, a composition“free of’ a component refers to a composition substantially devoid of the component, or comprising the component in an amount of less than about 0.01 wt%, by weight of the total composition.

[0025] As used herein, film layers that are the same in composition and in thickness are referred to as“identical” layers.

[0026] As used herein, a“laminate” refers to a multilayer structure comprising a sealant and a substrate attached to each other by lamination.

Hydrocarbon Resin

[0027] In one aspect of the present invention, the multilayer film described herein may comprise in the core layer a hydrocarbon resin. Suitable hydrocarbon resins include, but are not limited to, aliphatic hydrocarbon resins, at least partially hydrogenated aliphatic hydrocarbon resins, aliphatic/aromatic hydrocarbon resins, at least partially hydrogenated aliphatic aromatic hydrocarbon resins, aromatic resins, at least partially hydrogenated aromatic hydrocarbon resins, cycloaliphatic hydrocarbon resins, at least partially hydrogenated cycloaliphatic resins, cycloaliphatic/aromatic hydrocarbon resins, cycloaliphatic/aromatic at least partially hydrogenated hydrocarbon resins, polyterpene resins, terpene-phenol resins, rosin esters, rosin acids, grafted resins, and mixtures or combinations of two or more of the foregoing. The hydrocarbon resins may be polar or apolar.

[0028] In one embodiment, the hydrocarbon resin useful herein is produced by the thermal polymerization of cyclopentadiene (CPD) or substituted CPD, which may further include aliphatic or aromatic monomers as described later. The hydrocarbon resin may be a non aromatic resin or an aromatic resin. The hydrocarbon resin may have an aromatic content between 0 wt% and 60 wt%, or between 1 wt% and 60 wt%, or between 1 wt% and 40 wt%, or between 1 wt% and 20 wt%, or between 10 wt% and 20 wt%. Alternatively or additionally, the hydrocarbon resin may have an aromatic content between 15 wt% and 20 wt%, or between 1 wt% and 10 wt%, or between 5 wt% and 10 wt%. Preferred aromatics that may be in the hydrocarbon resin include one or more of styrene, indene, derivatives of styrene, and derivatives of indene. Particularly preferred aromatic olefins include styrene, alpha methylstyrene, beta-methylstyrene, indene, and methylindenes, and vinyl toluenes. Styrenic components include styrene, derivatives of styrene, and substituted styrenes. In general, styrenic components do not include fused-rings, such as indenics.

[0029] In another embodiment, the hydrocarbon resin useful herein is produced by the catalytic (cationic) polymerization of linear dienes. Such monomers are primarily derived from Steam Cracked Naphtha (SCN) and include Cs dienes such as piperylene (also known as 1,3- pentadiene). Polymerizable aromatic monomers can also be used to produce resins and may be relatively pure, e.g., styrene, -methyl styrene, or from a C9-aromatic SCN stream. Such aromatic monomers can be used alone or in combination with the linear dienes previously described.“Natural” monomers can also be used to produce resins, e.g., terpenes such as alpha- pinene or beta-carene, either used alone or in high or low concentrations with other polymerizable monomers. Typical catalysts used to make these resins are AlCk and BF3, either alone or complexed. Mono-olefin modifiers such as 2-methyl, 2-butene may also be used to control the MWD of the final resin. The final resin may be partially or totally hydrogenated.

[0030] In another embodiment, the hydrocarbon resin may be at least partially hydrogenated or substantially hydrogenated. As used herein,“at least partially hydrogenated” means that the material contains less than 90% olefinic protons, or less than 75% olefinic protons, or less than 50% olefinic protons, or less than 40% olefinic protons, or less than 25% olefinic protons, such as from 20% to 50% olefinic protons. As used herein,“substantially hydrogenated” means that the material contains less than 5% olefinic protons, or less than 4% olefinic protons, or less than 3% olefinic protons, or less than 2% olefinic protons, such as from 1% to 5% olefinic protons. The degree of hydrogenation is typically conducted so as to minimize and avoid hydrogenation of the aromatic bonds.

[0031] In yet another embodiment, the hydrocarbon resin may comprise one or more oligomers such as dimers, trimers, tetramers, pentamers, and hexamers. The oligomers may be derived from a petroleum distillate boiling in the range of 30°C-2l0°C. The oligomers may be derived from any suitable process and are often derived as a byproduct of resin polymerization. Suitable oligomer streams may have an M_n between 130 and 500, or between 130 and 410, or between 130 and 350, or between 130 and 270, or between 200 and 350, or between 200 and 320. Examples of suitable oligomer streams include, but are not limited to, oligomers of cyclopentadiene and substituted cyclopentadiene, oligomers of C₄-Ce conjugated diolefins, oligomers of Cs-Cio aromatic olefins, and combinations thereof. Other monomers may be present. These include C₄-Ce mono-olefins and terpenes. The oligomers may comprise one or more aromatic monomers and may be at least partially hydrogenated or substantially hydrogenated. [0032] Preferably, the hydrocarbon resin comprises a dicyclopentadiene, cyclopentadiene, and methylcyclopentadiene derived content of about 60 wt % to about 100 wt % of the total weight of the hydrocarbon resin. In any embodiment, the hydrocarbon resin may have a dicyclopentadiene, cyclopentadiene, and methylcyclopentadiene derived content of about 70 wt% to about 95 wt%, or about 80 wt% to about 90 wt%, or about 95 wt% to about 99 wt% of the total weight of the hydrocarbon resin. Preferably, the hydrocarbon resin may be a hydrocarbon resin that includes, in predominant part, dicyclopentadiene derived units. The term“dicyclopentadiene derived units”,“dicyclopentadiene derived content”, and the like refers to the dicyclopentadiene monomer used to form the polymer, i.e., the unreacted chemical compound in the form prior to polymerization, and can also refer to the monomer after it has been incorporated into the polymer, which by virtue of the polymerization reaction typically has fewer hydrogen atoms than it does prior to the polymerization reaction.

[0033] Preferred hydrocarbon resins may have a dicyclopentadiene derived content of about 50 wt% to about 100 wt% of the total weight of the hydrocarbon resin, more preferably about 60 wt% to about 100 wt% of the total weight of the hydrocarbon resin, even more preferably about 70 wt% to about 100 wt% of the total weight of the hydrocarbon resin. Accordingly, in any embodiment, suitable hydrocarbon resins may have a dicyclopentadiene derived content of about 50% or more, or about 60% or more, or about 70% or more, or about 75% or more, or about 90% or more, or about 95% or more, or about 99% or more of the total weight of the hydrocarbon resin.

[0034] Useful hydrocarbon resins may include up to 5 wt% indenic components, or up to 10 wt% indenic components. Indenic components include indene and derivatives of indene. Often, the hydrocarbon resin includes up to 15 wt% indenic components. Alternatively, the hydrocarbon resin is substantially free of indenic components.

[0035] Preferred hydrocarbon resins have a melt viscosity of from 300 to 800 centipoise (cPs) at l60°C, or more preferably of from 350 to 650 cPs at l60°C. Preferably, the melt viscosity of the hydrocarbon resin is from 375 to 615 cPs at l60°C, or from 475 to 600 cPs at l60°C. The melt viscosity may be measured by a Brookfield viscometer with a type“J” spindle according to ASTM D 6267.

[0036] Suitable hydrocarbon resins have an M_w greater than about 600 g/mole or greater than about 1000 g/mole. In any embodiment, the hydrocarbon resin may have an M_w of from about 600 to about 1400 g/mole, or from about 800 g/mole to about 1200 g/mole. Preferred hydrocarbon resins have a weight average molecular weight of from about 800 to about 1000 g/mole. Suitable hydrocarbon resins may have an M_n of from about 300 to about 800 g/mole, or from about 400 to about 700 g/mole, or more preferably from about 500 to about 600 g/mole. Suitable hydrocarbon resins may have an M_z of from about 1250 to about 3000 g/mole, or more preferably from about 1500 to about 2500 g/mole. In any embodiment, suitable hydrocarbon resins may have an M_w/M_n of 4 or less, preferably from 1.3 to 1.7.

[0037] Preferred hydrocarbon resins have a glass transition temperature (T_g) of from about 30°C to about 200°C, or from about 0°C to about l50°C, or from about 50°C to about l60°C, or from about 50°C to about l50°C, or from about 50°C to about l40°C, or from about 80°C to about l00°C, or from about 85°C to about 95°C, or from about 40°C to about 60°C, or from about 45°C to about 65°C. Preferably, suitable hydrocarbon resins have a T_g from about 60°C to about 90°C. DSC is used to determine glass transition temperature at l0°C/min.

[0038] Specific examples of commercially available hydrocarbon resins include Oppera™ PR 100, 100A, 101, 102, 103, 104, 105, 106, 111, 112, 115, and 120 materials, and Oppera™ PR 131 hydrocarbon resins, all available from ExxonMobil Chemical Company, ARKON™ M90, M100, Ml 15 and M135 and SUPER ESTER™ rosin esters available from Arakawa Chemical Company of Japan, SYLVARES™ phenol modified styrene- and methyl styrene resins, styrenated terpene resins, ZONATAC terpene- aromatic resins, and terpene phenolic resins available from Arizona Chemical Company, SYLVATAC™ and SYLVALITE™ rosin esters available from Arizona Chemical Company, NORSOLENE™ aliphatic aromatic resins available from Cray Valley of France, DERTOPHENE™ terpene phenolic resins available from DRT Chemical Company of Landes, France, EASTOTAC™ resins, PICCOTACT™ C5/C9 resins, REGALITE™ and REGALREZ™ aromatic and REGALITE™ cycloaliphatic/aromatic resins available from Eastman Chemical Company of Kingsport, Tenn., WINGTACK™ ET and EXTRA available from Goodyear Chemical Company, FORAL™, PENTALYN™, AND PERMALYN™ rosins and rosin esters available from Hercules (now Eastman Chemical Company), QUINTONE™ acid modified Cs resins, C5/C9 resins, and acid modified C5/C9 resins available from Nippon Zeon of Japan, and LX™ mixed aromatic/cycloaliphatic resins available from Neville Chemical Company, CLEARON hydrogenated terpene aromatic resins available from Yasuhara. The preceding examples are illustrative only and by no means limiting.

[0039] These commercial compounds generally have a Ring and Ball softening point (measured according to ASTM E-28 (Revision 1996)) of about l0°C to about 200°C, more preferably about 50°C to about l80°C, more preferably about 80°C to about l75°C, more preferably about l00°C to about l60°C, more preferably about H0°C to about l50°C, and more preferably about 125 °C to about l40°C, wherein any upper limit and any lower limit of softening point may be combined for a preferred softening point range. For hydrocarbon resins, a convenient measure is the ring and ball softening point determined according to ASTM E-28.

[0040] In one embodiment, the hydrocarbon resin is present in the core layer of the multilayer film described herein in an amount of from about 7 to about 15 wt%, for example, about 7 wt%, about 7.5 wt%, about 8 wt%, about 8.5 wt%, about 9 wt%, about 9.5 wt%, about 10 wt%, about 10.5 wt%, about 11 wt%, about 11.5 wt%, about 12 wt%, about 12.5 wt%, about 13 wt%, about 13.5 wt%, about 14 wt%, about 14.5 wt%, about 15 wt%, or in the range of any combination of the values recited herein, based on total weight of polymer in the core layer.

[0041] The hydrocarbon resin described herein may be optionally pre -blended with one or more polyethylene polymers described herein or other polymers that are miscible with the polyethylene polymers as described herein, e.g., in a masterbatch, and then blended with polyethylene to form the polymer composition in the core layer. Often, the pre-blend can comprise the hydrocarbon resin ranging from a lower limit of about 10 wt%, 20 wt%, about 30 wt%, about 40 wt%, about 50 wt%, about 60 wt%, or about 70 wt%, to an upper limit of about 90 wt%, about 80 wt%, about 70 wt%, about 60 wt%, about 50 wt%, or about 40 wt%, for example, about 10 wt%, about 20 wt%, about 30 wt%, about 40 wt%, about 50 wt%, about 60 wt%, about 70 wt%, about 80 wt%, or about 90 wt%, based on total weight of the pre-blend, or any ranges between two values as described above so long as the lower limit value is less than the upper limit value. Alternatively, the hydrocarbon resin described herein provided in a neat form, i.e. without being blended with any other polymers, and then blended with polyethylene to form the polymer composition in the core layer.

Polyethylene Polymer

[0042] In one aspect of the invention, the multilayer film may comprise two outer layers and a core layer between the two outer layers, each comprising a polyethylene having a density of about 0.910 to about 0.945 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR, I21_.6/I2_.16, of about 10 to about 100. The polyethylene that can be used for the multilayer film made according to the method described herein are selected from ethylene homopolymers, ethylene copolymers, and compositions thereof. Useful copolymers comprise one or more comonomers in addition to ethylene and can be a random copolymer, a statistical copolymer, a block copolymer, and/or compositions thereof. The method of making the polyethylene is not critical, as it can be made by slurry, solution, gas phase, high pressure or other suitable processes, and by using catalyst systems appropriate for the polymerization of polyethylene polymers, such as Ziegler-Natta-type catalysts, chromium catalysts, metallocene-type catalysts, other appropriate catalyst systems or combinations thereof, or by free-radical polymerization. In an exemplary embodiment, the polyethylene polymers are made by the catalysts, activators and processes described in U.S. Patent Nos. 6,342,566; 6,384,142; and 5,741,563; and WO 03/040201 and WO 97/19991. Such catalysts are well known in the art, and are described in, for example, ZIEGLER CATALYSTS (Gerhard Fink, Rolf Miilhaupt and Hans H. Brintzinger, eds., Springer-Verlag 1995); Resconi et al.; and I, II METALLOCENE-BASED POLYOLEFINS (Wiley & Sons 2000).

Polyethylene polymers that are useful in this invention include those sold under the trade names ENABLE™, EXACT™, EXCEED™, ESCORENE™, EXXCO™, ESCOR™, PAXON™, and OPTEMA™ (ExxonMobil Chemical Company, Houston, Texas, USA); DOW™, DOWLEX™, ELITE™, AFFINITY™, ENGAGE™, and FLEXOMER™ (The Dow Chemical Company, Midland, Michigan, USA); BORSTAR™ and QUEO™ (Borealis AG, Vienna, Austria); and TAFMER™ (Mitsui Chemicals Inc., Tokyo, Japan).

Preferred ethylene homopolymers and copolymers useful in this invention typically have one or more of the following properties:

1. an M_w of 20,000 g/mol or more, 20,000 to 2,000,000 g/mol, preferably 30,000 to 1,000,000, preferably 40,000 to 200,000, preferably 50,000 to 750,000, using a gel permeation chromatograph (“GPC”) according to the procedure disclosed herein; and/or

2. a T_m of 30°C to l50°C, preferably 30°C to l40°C, preferably 50°C to l40°C, more preferably 60°C to 135 °C, as determined by second melting curve based on ASTM D3418; and/or

3. a crystallinity of 5% to 80%, preferably 10% to 70%, more preferably 20% to 60%, preferably at least 30%, or at least 40%, or at least 50%, as determined by enthalpy of crystallization curve based on ASTM D3418 and calculated by the following formula:

Crystallinity % = Enthalpy (J/g)/ 298 (J/g) x 100%,

wherein 298 (J/g) is enthalpy of 100% crystallinity polyethylene; and/or

4. a heat of fusion of 300 J/g or less, preferably 1 to 260 J/g, preferably 5 to 240 J/g, preferably 10 to 200 J/g, as determined based on ASTM D3418-03; and/or

5. a crystallization temperature (T_c) of 15°C to 130°C, preferably 20°C to 120°C, more preferably 25°C to 110°C, preferably 60°C to 125°C, as determined based on ASTM D3418-03; and/or

6. a heat deflection temperature of 30°C to 120°C, preferably 40°C to 100°C, more preferably 50°C to 80°C as measured based on ASTM D648 on injection molded flexure bars, at 66 psi load (455 kPa); and/or 7. a Shore hardness (D scale) of 10 or more, preferably 20 or more, preferably 30 or more, preferably 40 or more, preferably 100 or less, preferably from 25 to 75 (as measured based on ASTM D 2240); and/or

8. a percent amorphous content of at least 50%, preferably at least 60%, preferably at least 70%, more preferably between 50% and 95%, or 70% or less, preferably 60% or less, preferably 50% or less as determined by subtracting the percent crystallinity from 100.

[0043] The polyethylene may be an ethylene homopolymer, such as HDPE. In one embodiment, the ethylene homopolymer has a molecular weight distribution (M_w/M_n) or (MWD) of up to 40, preferably ranging from 1.5 to 20, or from 1.8 to 10, or from 1.9 to 5, or from 2.0 to 4. In another embodiment, the 1 % secant flexural modulus (determined based on ASTM D790A, where test specimen geometry is as specified under the ASTM D790 section “Molding Materials (Thermoplastics and Thermosets),” and the support span is 2 inches (5.08 cm)) of the polyethylene falls in a range of 200 to 1000 MPa, and from 300 to 800 MPa in another embodiment, and from 400 to 750 MPa in yet another embodiment, wherein a desirable polymer may exhibit any combination of any upper flexural modulus limit with any lower flexural modulus limit. The MI of preferred ethylene homopolymers range from 0.05 to 800 dg/min in one embodiment, and from 0.1 to 100 dg/min in another embodiment, as measured based on ASTM D1238 (l90°C, 2.16 kg).

[0044] In an exemplary embodiment, the polyethylene comprises less than 20 mol% propylene units (preferably less than 15 mol%, preferably less than 10 mol%, preferably less than 5 mol%, and preferably 0 mol% propylene units).

[0045] In another embodiment of the invention, the polyethylene useful herein is produced by polymerization of ethylene and, optionally, an alpha-olefin with a catalyst having, as a transition metal component, a bis (n-C_3-4 alkyl cyclopentadienyl) hafnium compound, wherein the transition metal component preferably comprises from about 95 mol% to about 99 mol% of the hafnium compound as further described in U.S. Patent No. 9,956,088.

[0046] In another embodiment of the invention, the polyethylene is an ethylene copolymer, either random or block, of ethylene and one or more comonomers selected from C₃ to C20 a- olefins, typically from C₃ to C10 a-olefins. Preferably, the comonomers are present from 0.1 wt% to 50 wt% of the copolymer in one embodiment, and from 0.5 wt% to 30 wt% in another embodiment, and from 1 wt% to 15 wt% in yet another embodiment, and from 0.1 wt% to 5 wt% in yet another embodiment, wherein a desirable copolymer comprises ethylene and C₃ to C20 a-olefin derived units in any combination of any upper wt% limit with any lower wt% limit described herein. Preferably the ethylene copolymer will have a weight average molecular weight of from greater than 8,000 g/mol in one embodiment, and greater than 10,000 g/mol in another embodiment, and greater than 12,000 g/mol in yet another embodiment, and greater than 20,000 g/mol in yet another embodiment, and less than 1,000,000 g/mol in yet another embodiment, and less than 800,000 g/mol in yet another embodiment, wherein a desirable copolymer may comprise any upper molecular weight limit with any lower molecular weight limit described herein.

[0047] In another embodiment, the ethylene copolymer comprises ethylene and one or more other monomers selected from the group consisting of C3 to C20 linear, branched or cyclic monomers, and in some embodiments is a C3 to C12 linear or branched alpha-olefin, preferably butene, pentene, hexene, heptene, octene, nonene, decene, dodecene, 4-methyl-pentene-l,3- methyl pentene-l,3,5,5-trimethyl-hexene-l, and the like. The monomers may be present at up to 50 wt%, preferably from up to 40 wt%, more preferably from 0.5 wt% to 30 wt%, more preferably from 2 wt% to 30 wt%, more preferably from 5 wt% to 20 wt%, based on the total weight of the ethylene copolymer.

[0048] Preferred linear alpha-olefins useful as comonomers for the ethylene copolymers useful in this invention include C3 to Cx alpha-olefins, more preferably 1 -butene, 1 -hexene, and 1 -octene, even more preferably 1 -hexene. Preferred branched alpha-olefins include 4-methyl- l-pentene, 3 -methyl- 1 -pentene, 3,5,5-trimethyl-l-hexene, and 5-ethyl- 1 -nonene. Preferred aromatic-group-containing monomers contain up to 30 carbon atoms. Suitable aromatic- group-containing monomers comprise at least one aromatic structure, preferably from one to three, more preferably a phenyl, indenyl, fluorenyl, or naphthyl moiety. The aromatic-group- containing monomer further comprises at least one polymerizable double bond such that after polymerization, the aromatic structure will be pendant from the polymer backbone. The aromatic-group containing monomer may further be substituted with one or more hydrocarbyl groups including but not limited to Ci to C10 alkyl groups. Additionally, two adjacent substitutions may be joined to form a ring structure. Preferred aromatic-group-containing monomers contain at least one aromatic structure appended to a polymerizable olefinic moiety. Particularly, preferred aromatic monomers include styrene, alpha-methylstyrene, para- alkylstyrenes, vinyltoluenes, vinylnaphthalene, allyl benzene, and indene, especially styrene, paramethyl styrene, 4-phenyl- 1 -butene and allyl benzene.

[0049] Preferred diolefin monomers useful in this invention include any hydrocarbon structure, preferably C₄ to C30, having at least two unsaturated bonds, wherein at least two of the unsaturated bonds are readily incorporated into a polymer by either a stereospecific or a non-stereospecific catalyst(s). It is further preferred that the diolefin monomers be selected from alpha, omega-diene monomers (i.e., di-vinyl monomers). More preferably, the diolefin monomers are linear di-vinyl monomers, most preferably those containing from 4 to 30 carbon atoms. Examples of preferred dienes include butadiene, pentadiene, hexadiene, heptadiene, octadiene, nonadiene, decadiene, undecadiene, dodecadiene, tridecadiene, tetradecadiene, pentadecadiene, hexadecadiene, heptadecadiene, octadecadiene, nonadecadiene, icosadiene, heneicosadiene, docosadiene, tricosadiene, tetracosadiene, pentacosadiene, hexacosadiene, heptacosadiene, octacosadiene, nonacosadiene, triacontadiene, particularly preferred dienes include l,6-heptadiene, l,7-octadiene, 1,8 -nonadiene, l,9-decadiene, l,lO-undecadiene, 1,11- dodecadiene, l,l2-tridecadiene, l,l3-tetradecadiene, and low molecular weight polybutadienes (Mw less than 1000 g/mol). Preferred cyclic dienes include cyclopentadiene, vinylnorbornene, norbomadiene, ethylidene norbornene, divinylbenzene, dicyclopentadiene, or higher ring containing diolefins with or without substituents at various ring positions.

[0050] In an exemplary embodiment, one or more dienes are present in the polyethylene at up to 10 wt%, preferably at 0.00001 wt% to 2 wt%, preferably 0.002 wt% to 1 wt%, even more preferably 0.003 wt% to 0.5 wt%, based upon the total weight of the polyethylene. In some embodiments, diene is added to the polymerization in an amount of from an upper limit of 500 ppm, 400 ppm, or 300 ppm to a lower limit of 50 ppm, 100 ppm, or 150 ppm.

[0051] Preferred ethylene copolymers useful herein are preferably a copolymer comprising at least 50 wt% ethylene and having up to 50 wt%, preferably 1 wt% to 35 wt%, even more preferably 1 wt% to 6 wt% of a C₃ to C₂₀ comonomer, preferably a C₄ to Cx comonomer, preferably hexene or octene, based upon the weight of the copolymer. Preferably these polymers are metallocene polyethylenes (mPEs).

[0052] Useful mPE homopolymers or copolymers may be produced using mono- or bis- cyclopentadienyl transition metal catalysts in combination with an activator of alumoxane and/or a non-coordinating anion in solution, slurry, high pressure or gas phase. The catalyst and activator may be supported or unsupported and the cyclopentadienyl rings may be substituted or unsubstituted.

[0053] In a class of embodiments, the polyethylene in the core layer may comprise at least one of a first polyethylene and a second polyethylene, both as a polyethylene defined herein, the first polyethylene having a density of about 0.910 to about 0.945 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 2.5 to about 5.5, and an MIR, I21_.6/I2_.16, of about 25 to about 100; the second polyethylene having a density of about 0.910 to about 0.940 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR, I21.6/I2.16, of about 10 to about 25. [0054] In various embodiments, the first polyethylene may have one or more of the following properties:

(a) a density (sample prepared according to ASTM D-4703, and the measurement according to ASTM D-1505) of about 0.910 to about 0.945 g/cm³, or about 0.920 to about 0.940 g/cm³;

(b) an MI (I2_.16, ASTM D-1238, 2.16 kg, l90°C) of about 0.1 to about 15 g/lO min, or about 0.1 to about 10 g/lO min, or about 0.1 to about 5 g/lO min;

(c) an MIR (I21.6 (l90°C, 21.6 kg)/l2.i6 (l90°C, 2.16 kg)) of greater than 25 to about 100, or greater than 30 to about 90, or greater than 35 to about 80;

(d) a composition distribution breadth index (CDBI) of greater than about 50%, or greater than about 60%, or greater than 75%, or greater than 85%; the CDBI may be determined using techniques for isolating individual fractions of a sample of the resin. The preferred technique is Temperature Rising Elution Fraction (“TREF”), as described in Wild, et a , J. Poly. Sci., Poly. Phys. Ed., Vol. 20, p. 441 (1982), which is incorporated herein for purposes of U.S. practice;

(e) a molecular weight distribution (MWD) or (M_w/M_n) of about 2.5 to about 5.5; MWD is measured using a gel permeation chromatograph (“GPC”) on a Waters 150 gel permeation chromatograph equipped with a differential refractive index (“DRI”) detector and a Chromatix KMX-6 on line light scattering photometer. The system is used at 135°C with 1,2,4-trichlorobenzene as the mobile phase using Shodex (Showa Denko America, Inc.) polystyrene gel columns 802, 803, 804, and 805. This technique is discussed in“Liquid Chromatography of Polymers and Related Materials III,” J. Cazes editor, Marcel Dekker, 1981, p. 207, which is incorporated herein by reference. Polystyrene is used for calibration. No corrections for column spreading are employed; however, data on generally accepted standards, e.g., National Bureau of Standards Polyethylene 1484 and anionically produced hydrogenated polyisoprenes (alternating ethylene-propylene copolymers) demonstrate that such corrections on MWD are less than 0.05 units. M_w/M_n is calculated from elution times. The numerical analyses are performed using the commercially available Beckman/CIS customized LALLS software in conjunction with the standard Gel Permeation package. Reference to M_w/M_n implies that the M_w is the value reported using the LALLS detector and M_n is the value reported using the DRI detector described above; and/or

(f) a branching index (“g”) of about 0.5 to about 0.97, or about 0.7 to about 0.95. Branching Index is an indication of the amount of branching of the polymer and is defined as g'=[Rg]²fcr/[Rg]²/m.“Rg” stands for Radius of Gyration, and is measured using a Waters 150 gel permeation chromatograph equipped with a Multi- Angle Laser Light Scattering (“MALLS”) detector, a viscosity detector and a differential refractive index detector.“| Rg|_/„” is the Radius of Gyration for the branched polymer sample and“[Rg]_/,„” is the Radius of Gyration for a linear polymer sample.

[0055] The first polyethylene is not limited by any particular method of preparation and may be formed using any process known in the art. For example, the first polyethylene may be formed using gas phase, solution, or slurry processes.

[0056] In one embodiment, the first polyethylene is formed in the presence of a Ziegler- Natta catalyst. In another embodiment, the first polyethylene is formed in the presence of a single-site catalyst, such as a metallocene catalyst (such as any of those described herein). Particularly useful catalyst systems include supported dimethylsilyl bis(tetrahydroindenyl) zirconium dichloride. Polyethylene polymers useful as the first polyethylene in this invention include those disclosed in U.S. Patent No. 6,476,171, which is hereby incorporated by reference for this purpose, and include those commercially available from ExxonMobil Chemical Company in Houston, Texas, such as those sold under the trade designation ENABLE™.

[0057] In various embodiments, the second polyethylene may have one or more of the following properties:

(a) a density (sample prepared according to ASTM D-4703, and the measurement according to ASTM D-1505) of about 0.910 to 0.940 g/cm³, or about 0.912 to about 0.935 g/cm³;

(b) an MI (I2_.16, ASTM D-1238, 2.16 kg, l90°C) of about 0.1 to about 15 g/lO min, or about 0.5 to about 10 g/lO min, or about 1 to about 5 g/lO min;

(c) an MIR (I21.6 (l90°C, 21.6 kg)/l2.i6 (l90°C, 2.16 kg)) of about 10 to about 25, or about 15 to about 20;

(d) an CDBI (measured according to the procedure disclosed herein) of up to about 85%, or up to about 75%, or about 5 to about 85%, or 10 to 75%. The CDBI may be determined using techniques for isolating individual fractions of a sample of the resin. The preferred technique is Temperature Rising Elution Fraction (“TREF”), as described in Wild, et a , J. Poly. Sci., Poly. Phys. Ed., Vol. 20, p. 441 (1982), which is incorporated herein for purposes of U.S. practice;

(e) an MWD (measured according to the procedure disclosed herein) of about 1.5 to about 5.5; and/or

(f) a branching index (“g”, determined according to the procedure described herein) of about 0.9 to about 1.0, or about 0.96 to about 1.0, or about 0.97 to about 1.0. [0058] The second polyethylene is not limited by any particular method of preparation and may be formed using any process known in the art. For example, the second polyethylene may be formed using gas phase, solution, or slurry processes.

[0059] In one embodiment, the second polyethylene is formed in the presence of a metallocene catalyst. For example, the second polyethylene may be an mPF produced using mono- or bis-cyclopentadienyl transition metal catalysts in combination with an activator of alumoxane and/or a non-coordinating anion in solution, slurry, high pressure or gas phase. The catalyst and activator may be supported or unsupported and the cyclopentadienyl rings may be substituted or unsubstituted. mPFs useful as the second polyethylene include those commercially available from ExxonMobil Chemical Company in Houston, Texas, such as those sold under the trade designation EXCEED™.

[0060] In an exemplary embodiment, the core layer of the multilayer film described herein may further comprise a third polyethylene (as a polyethylene defined herein) having a density of at least about 0.945 g/cm³, preferably about 0.945 g/cm³ to about 0.965 g/cm³. The third polyethylene is typically prepared with either Ziegler-Natta or chromium-based catalysts in slurry reactors, gas phase reactors, or solution reactors. Polyethylene polymers useful as the third polyethylene in this invention include those commercially available from ExxonMobil Chemical Company in Houston, Texas, such as HDPE.

[0061] In another exemplary embodiment, the hydrocarbon resin described herein is present in the core layer of the multilayer film in a pre-blend with a fourth polyethylene (as a polyethylene defined herein) having a density of at least about 0.945 g/cm³, preferably about 0.945 g/cm³ to about 0.965 g/cm³. In various embodiments, the fourth polyethylene may conform to characteristics as set out above for the third polyethylene. The fourth polyethylene may be the same as or different from the third polyethylene. Preferably, the fourth polyethylene is the same as the third polyethylene.

[0062] In another class of embodiments, the polyethylene in at least one of the two outer layers of the multilayer film described herein may comprise a fifth polyethylene, the fifth polyethylene having a density of about 0.910 to about 0.945 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 2.5 to about 5.5, and an MIR, I21_.6/I2_.16, of about 25 to about 100. In various embodiments, the fifth polyethylene may conform to characteristics as set out above for the first polyethylene. The fifth polyethylene may be the same as or different from the first polyethylene. Preferably, the fifth polyethylene is the same as the first polyethylene. [0063] The first, the second, the third, and the fourth polyethylene polymers, if present in the core layer, and the fifth polyethylene, if present in at least one of the two outer layers of the multilayer film described herein, may each be optionally in a blend with one or more other polymers, such as polyethylenes defined herein, which blend is referred to as polyethylene composition. In particular, the polyethylene compositions described herein may be physical blends or in situ blends of more than one type of polyethylene or compositions of polyethylenes with polymers other than polyethylenes where the polyethylene component is the majority component, e.g., greater than 50 wt% of the total weight of the composition.

[0064] In one embodiment, the two outer layers and the core layer of the multilayer film described herein may each comprise at least about 50 wt% of a polyethylene having a density of about 0.910 to about 0.945 g/cm³, a melt index (MI), I2_.16, of about 0.1 to about 15 g/lO min, a molecular weight distribution (MWD) of about 1.5 to about 5.5, and a melt index ratio (MIR), I21_.6/I2_.16, of about 10 to about 100. The polyethylene may be present in each of the above layers in an amount of, for example, about 50 wt%, about 55 wt%, about 60 wt%, about 65 wt%, about 70 wt%, about 75 wt%, about 80 wt%, about 85 wt%, about 90 wt%, about 95 wt%, or about 100 wt%, or in the range of any combination of the values recited herein, based on total weight of polymer in the layer. In an exemplary embodiment where the polyethylene in the core layer comprises at least one of the first polyethylene described herein and the second polyethylene described herein, the first polyethylene and the second polyethylene are present in a total amount of at least about 50 wt%, for example, about 50 wt%, about 55 wt%, about 60 wt%, about 65 wt%, about 70 wt%, about 75 wt%, about 80 wt%, about 85 wt%, about 90 wt%, about 95 wt%, about 100 wt%, or in the range of any combination of the values recited herein, based on total weight of polymer in the core layer. In an exemplary embodiment where the hydrocarbon resin in the core layer is present in a pre-blend with the fourth polyethylene described herein, the weight ratio between the hydrocarbon resin and the fourth polyethylene is from about 1:2 to about 2:1, for example, about 1:2, about 3:5, about 2:3, about 3:4, about 4:5, about 1: 1, about 5:4, about 4:3, about 3:2, about 5:3, about 2: 1, or anywhere between any combination of the values recited herein. In yet another exemplary embodiment, the polyethylene in at least one of the two outer layers is present in an amount of from about 80 to about 100 wt%, for example, about 80 wt%, about 82 wt%, about 84 wt%, about 86 wt%, about 90 wt%, about 92 wt%, about 94 wt%, about 96 wt%, about 98 wt%, about 100 wt%, or anywhere between any combination of the values recited herein, based on total weight of polymer in the layer. [0065] In a class of embodiments, in addition to polyethylene as described above, the multilayer film of the present invention may further comprise other polymers, including without limitation other polyolefins, polar polymers, and cationic polymers, in any layer of the multilayer film.

Film Structures

[0066] The multilayer film of the present invention may further comprise additional layer(s), which may be any layer typically included in multilayer film constructions. For example, the additional layer(s) may be made from:

1. Polyolefins. Preferred polyolefins include homopolymers or copolymers of C 2 to C40 olefins, preferably C2 to C20 olefins, preferably a copolymer of an a-olefin and another olefin or a-olefin (ethylene is defined to be an a-olefin for purposes of this invention). Preferably homopolyethylene, homopolypropylene, propylene copolymerized with ethylene and/or butene, ethylene copolymerized with one or more of propylene, butene or hexene, and optional dienes. Preferred examples include thermoplastic polymers such as ultra-low density polyethylene, very low density polyethylene, linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, polypropylene, isotactic polypropylene, highly isotactic polypropylene, syndiotactic polypropylene, random copolymer of propylene and ethylene and/or butene and/or hexene, elastomers such as ethylene propylene rubber, ethylene propylene diene monomer rubber, neoprene, and compositions of thermoplastic polymers and elastomers, such as, for example, thermoplastic elastomers and rubber toughened plastics.

2. Polar polymers. Preferred polar polymers include homopolymers and copolymers of esters, amides, acetates, anhydrides, copolymers of a C2 to C20 olefin, such as ethylene and/or propylene and/or butene with one or more polar monomers, such as acetates, anhydrides, esters, alcohol, and/or acrylics. Preferred examples include polyesters, polyamides, ethylene vinyl acetate copolymers, and polyvinyl chloride.

3. Cationic polymers. Preferred cationic polymers include polymers or copolymers of geminally disubstituted olefins, a-heteroatom olefins and/or styrenic monomers. Preferred geminally disubstituted olefins include isobutylene, isopentene, isoheptene, isohexane, isooctene, isodecene, and isododecene. Preferred a-heteroatom olefins include vinyl ether and vinyl carbazole, preferred styrenic monomers include styrene, alkyl styrene, para-alkyl styrene, a-methyl styrene, chloro-styrene, and bromo-para-methyl styrene. Preferred examples of cationic polymers include butyl rubber, isobutylene copolymerized with para methyl styrene, polystyrene, and poly-a-methyl styrene. 4. Miscellaneous. Other preferred layers can be paper, wood, cardboard, metal, metal foils (such as aluminum foil and tin foil), metallized surfaces, glass (including silicon oxide (SiO_x) coatings applied by evaporating silicon oxide onto a film surface), fabric, spunbond fibers, and non-wovens (particularly polypropylene spunbond fibers or non-wovens), and substrates coated with inks, dyes, pigments, and the like.

[0067] In particular, the multilayer film described herein can also include layers comprising materials such as ethylene vinyl alcohol (EVOH), polyamide (PA), polyvinylidene chloride (PVDC), or aluminium, so as to obtain barrier performance for the film where appropriate.

[0068] The thickness of the multilayer films may range from 10 to 200 pm in general and is mainly determined by the intended use and properties of the film. Stretch films may be thin; those for shrink films or heavy duty bags are much thicker. Conveniently, the film has a thickness of no more than about 170 pm, for example, from 10 to 170 pm, from 20 to 160 pm, from 30 to 150 pm, or from 40 to 130 pm. In an exemplary embodiment where the multilayer film is an MDO film, the MDO film may have a thickness of no more than about 30 pm. Preferably, the thickness ratio between one of the outer layers and the core layer is from about 1:2 to about 1:6, for example, about 1:2, about 1:3, about 1:4, about 1:5, about 1:6, or in the range of any combination of the values recited herein.

[0069] The multilayer film described herein may have an A/Y/B structure, wherein the A and B layers are the two outer layers, respectively, and Y is the core layer in contact with the outer layers. Suitably one or both the outer layers are a skin layer forming one or both film surfaces and can serve as a lamination skin (the surface to be adhered to a sealant film or a substrate film) or a sealable skin (the surface to form a seal). Preferably, one of the outer layers serves as the lamination skin to be attached to a sealant film. The composition of A and B layers may be the same or different, but conform to the limitations set out herein for the sealant. Preferably, the A and B layers are identical.

[0070] In an exemplary embodiment, the multilayer film has a three-layer A/Y/B structure, comprising two outer layers and a core layer between the two outer layers, wherein: (a) the core layer comprises a first polyethylene, a second polyethylene, a third polyethylene, and a blend of a hydrocarbon resin and a fourth polyethylene, the first polyethylene having a density of about 0.910 to about 0.945 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 2.5 to about 5.5, and an MIR, I21_.6/I2_.16, of about 25 to about 100; the second polyethylene having a density of about 0.910 to about 0.940 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR, I21.6/I2.16, of about 10 to about 25; the third polyethylene having a density of at least about 0.945 g/cm³; the hydrocarbon resin comprising an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, or a combination thereof; the fourth polyethylene being the same as the third polyethylene; wherein the first polyethylene and the second polyethylene are present in a total amount of at least about 50 wt%, based on total weight of polymer in the core layer; wherein the hydrocarbon resin is present in an amount of from about 5 to about 10 wt%, based on total weight of polymer in the core layer; wherein the weight ratio between the hydrocarbon resin and the fourth polyethylene in the blend is about 1:2 to about 2: 1; (b) each of the two outer layers comprises about 100 wt% of the first polyethylene, based on total weight of polymer in the layer; wherein the thickness ratio between each of the outer layers and the core layer is about 1:4. In particular, the multilayer film may be an MDO film, preferably formed at a stretch ratio of from about 4.0 to about 5.0.

Film Properties and Applications

[0071] The multilayer films of the present invention, preferably blown films, may be adapted to form flexible packaging laminate films, including stand-up pouches, as well as a wide variety of other applications, such as cling film, low stretch film, non- stretch wrapping film, pallet shrink, over-wrap, agricultural, and collation shrink film. The film structures that may be used for bags are prepared such as sacks, trash bags and liners, industrial liners, produce bags, and medium duty bags. The film may be used in flexible packaging, food packaging, e.g., fresh cut produce packaging, frozen food packaging, bundling, packaging and unitizing a variety of products.

[0072] The inventive multilayer film described herein may have at least one of the following properties: (i) a maximum puncture force of at least about 15% higher; and (ii) an oxygen transmission rate (OTR) reduced by at least about seven times, compared to that of a film comprising 5 wt% of the hydrocarbon resin, based on total weight of polymer in the core layer, but otherwise identical in terms of film formulation, thickness, and structure. For example, the multilayer film preferably has at least one of the following properties at a film thickness of about 130 pm: (i) a maximum puncture force of at least about 140 N; and/or (ii) an oxygen transmission rate (OTR) of about 100 cm³/(m²-day) or less.

[0073] In an exemplary embodiment where the multilayer film described herein is an MDO film, preferably a blown MDO film, the multilayer film has at least one of the following properties: (i) a haze of at least about 30% lower; (ii) a gloss at 45° of at least about 12% higher; (iii) an average 1% Secant Modulus of at least 8% higher; (iv) a maximum puncture force of at least about 35% higher; (v) a water vapor transmission rate (WVTR) of at least about 25% lower; (vi) a hot tack force of at least about 35% higher at a sealing temperature of l40°C; compared to that of an MDO film free of the hydrocarbon resin but otherwise identical in terms of film formulation, thickness, and structure. For example, the multilayer film preferably has at least one of the following properties at a film thickness of about 30 pm: (i) a haze of at about 5% or less; (ii) a gloss at 45° of at least about 75 or more; (iii) an average 1% Secant Modulus of at least about 1150 or more; (iv) a maximum puncture force of at least about 45 N; (v) a water vapor transmission rate (WVTR) of at least about 6 g/(m²-day) or less; and/or (vi) a hot tack force of at least about 10 N/30 mm at a sealing temperature of l40°C.

[0074] It has been unexpectedly discovered that the multilayer film design as set out herein, by virtue of introduction of the hydrocarbon resin described herein in a particular amount into the core layer, can advantageously and economically modify the overall profile with highlight in some properties without significantly compromising others and, even more notably, can establish different sets of performance profile subject to machine direction orientation of the film, thus allowing for flexibility in tailoring film performance per varying requirements by specific end-uses.

Methods for Making the Multilayer Film

[0075] Also provided are methods for making multilayer films of the present invention. A method for making a multilayer film may comprise the steps of: (a) preparing two outer layers and a core layer between the two outer layers, each comprising at least about 50 wt% of a polyethylene, based on total weight of polymer in the layer, the polyethylene having a density of about 0.910 to about 0.945 g/cm³, an MI, I2_.16, of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR, I21_.6/I2_.16, of about 10 to about 100; wherein the core layer further comprises from about 7 to about 15 wt% of a hydrocarbon resin, based on total weight of polymer in the core layer, the hydrocarbon resin comprising an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, or a combination thereof; and (b) forming a film comprising the layers in step (a). Preferably, the method may further comprise after step (b) a step of subjecting the film in step (b) to machine direction orientation. [0076] The multilayer films described herein may be formed by any of the conventional techniques known in the art including blown extrusion, cast extrusion, coextrusion, blow molding, casting, and extrusion blow molding.

[0077] In one embodiment of the invention, the multilayer film described herein is formed by using blown techniques, i.e., to form a blown film. For example, the polymer composition formulated as described herein can be extruded in a molten state through an annular die and then blown and cooled to form a tubular, blown film, which can then be axially slit and unfolded to form a flat film. As a specific example, blown films can be prepared as follows. The polymer composition is introduced into the feed hopper of an extruder, such as a 50 mm extruder that is water-cooled, resistance heated, and has an L/D ratio of 30:1. The film can be produced using a 28 cm die with a 1.4 mm die gap, along with a dual air ring and internal bubble cooling. The film is extruded through the die into a film cooled by blowing air onto the surface of the film. The film is drawn from the die typically forming a cylindrical film that is cooled, collapsed and, optionally, subjected to a desired auxiliary process, such as slitting, treating, sealing, or printing. Typical melt temperatures are from about l80°C to about 230°C. Blown film rates are generally from about 3 to about 25 kilograms per hour per inch (about 4.35 to about 26.11 kilograms per hour per centimeter) of die circumference. The finished film can be wound into rolls for later processing. A particular blown film process and apparatus suitable for forming films according to embodiments of the present invention is described in U.S. Patent No. 5,569,693. Of course, other blown film forming methods can also be used.

[0078] In blown film extrusion, the film may be pulled upwards by, for example, pinch rollers after exiting from the die and is simultaneously inflated and stretched transversely sideways to an extent that can be quantified by the blow up ratio (BUR). The inflation provides the transverse direction (TD) stretch, while the upwards pull by the pinch rollers provides a machine direction (MD) stretch. As the polymer cools after exiting the die and inflation, it crystallizes and a point is reached where crystallization in the film is sufficient to prevent further MD or TD orientation.

[0079] Variables in this process that determine the ultimate film properties include the die gap, the BUR, the take up speed and the frost line height. Certain factors tend to limit production speed and are largely determined by the polymer rheology including the shear sensitivity which determines the maximum output and the melt tension which limits the bubble stability, BUR and take up speed.

[0080] In an exemplary embodiment, the multilayer film described herein is subject to machine direction orientation (MD orientation). Some methods of producing a polymer film suitable for MD orientation subsequent to the film making may be blown and cast film methods. Particular blown film methods include extruding the polyethylene composition through an annular die to form an extruded tube of molten material to provide the tube with a tube diameter which is substantially the annular die diameter. At the same time, continuously extruding the tube, expanding the tube, downstream of said annular die, to attenuate the walls thereof to form the tube of molten material into a bubble of a bubble diameter which exceeds (i) the annular die diameter and (ii) the tube diameter. The bubble has a frost line which comprises a demarcation line between the molten material and crystalline film.

[0081] Some films suitable for MD orientation described herein are made by a cast film process. Typically, in a cast film process, forming the polyethylene composition into a film includes melt extruding the polyethylene composition through a flat or slot die to form an extrudate that is continuously moved onto a polished turning roller, where it is quenched from one side. The speed of the roller controls the draw ratio and final film thickness.

[0082] Increased stretch ratio reduces final film thickness. The film may then be then sent to a second roller for cooling on the other side. Typically, although not necessarily, the film passes through a system of rollers and is wound onto a roll. Most flat dies are of T-slot or coat hanger designs, which contain a manifold to spread the flowing polymer across the width of the die, followed downstream by alternating narrow and open slits to create the desired flow distribution and pressure drop.

[0083] Suitable blown film and cast film process are described in detail in "Plastics Films" by John H. Briston, Longman Scientific and Technical, 1986, which is incorporated herein by reference in its entirety.

[0084] Films suitable for MD orientation have a gauge (or thickness as defined above) before MD orientation ranging from 10 to 130 pm. The lower limit of film gauge before MD orientation can be 10, 15, 20, 25, 30, 40, 45, 50, 60, 70, 80, or 90 pm. The upper limit on gauge before MD orientation can be 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 35, 30, 25, or 20 pm. Any combination of lower and upper limits (where upper limit > lower limit) should be considered to be disclosed by the above limits, e.g., 10 to 130 pm, 20 to 130 pm, 30 to 130 pm, 40 to 130 pm, 50 to 130 pm, etc. In certain exemplary embodiments, the film before MD orientation has a gauge of 50 to 130 pm.

[0085] This application is directed to orientation of polymer films formed by either cast or blown processes after the film polymer is no longer in its molten state and has solidified having a crystalline structure. MD orientation can be achieved by any known MD orientation process either in-line or off-line with the extrusion on cast films or blown films. That is, the film produced by blown or cast process can either be temporarily stored (off-line) before MD orientation or can be fed directly (in-line) to the MD orientation equipment.

[0086] Orientation methods may be with or without heat added. Cold drawing or stretching are suitable methods. When the film is heated, no case will the polymer be heated above its melting temperature.

[0087] A preferred MD orientation process can consist of heating the film to an orientation temperature, preferably using a set of temperature controlled rollers. The orientation temperature may be up to the polymer’s melt temperature. Next the heated film is fed into a slow drawing roll with a nip roller, which has the same rolling speed as the heating rollers. The film then enters a fast drawing roller having a speed that is, for example, 1.5 to 12 times faster than the slow draw roll, which effectively orients (stretches) the film on a continuous basis. The oriented film then enters annealing thermal rollers, which allow stress relaxation by holding the film at an elevated temperature for a period of time. The annealing temperature is preferably within, or slightly below (e.g., 10 to 20°C below but not lower than room temperature, for purposes here room temperature is 23 °C), the same temperature range as used for stretching. Finally, the film is cooled through cooling rollers to an ambient temperature to produce a machine direction oriented (MDO) film.

[0088] In an exemplary embodiment, the multilayer film described herein is an MDO film formed with a stretch ratio of from about 4.0 to about 5.0, more preferably from about 4.2 to about 4.8.

[0089] The multilayer film can have a gauge after MD orientation ranging from 10 to 110 pm. The lower limit of film gauge after MD orientation can be 10, 15, 20, 25, 30, 40, 50, 60, 70, or 80 pm. The upper limit on gauge after MD orientation can be 110, 100, 80, 70, 60, 50, 40, 30, 25, or 20 pm. Any combination of lower and upper limits, where upper limit is > lower limit, should be considered to be disclosed by the above limits, e.g., 10 to 100 pm, 10 to 50 pm, 15 to 40 pm, 20 to 30 pm, 30 to 90 pm, 40 to 110 pm, 40 to 100 pm, etc. In certain exemplary embodiments, the film after MD orientation has a gauge of no more than about 30 pm, preferably 15 to 40 pm.

[0090] The multilayer film of the present invention can be used for a substrate film to form laminate structure. The laminate structure can be prepared by laminating a sealant to a substrate comprising the multilayer film described herein via respective lamination skins using any process known in the art, including solvent based adhesive lamination, solvent less adhesive lamination, extrusion lamination, heat lamination, etc. [0091] In one desirable embodiment, the method described herein may further comprise after the multilayer film described herein is formed a step of forming a seal comprising the multilayer film or the laminate prepared as described above, suitably by sealing together respective sealable skins of the multilayer film or the laminate· The seal described herein can be made by any process such as extrusion coating, lamination, sheet extrusion, injection molding or cast film processes. Particularly, it has been found that presence of the hydrocarbon resin in the multilayer film as MD oriented can contribute to remarkable increase in hot tack peak and width of hot tack window, so that enhanced sealing performance and operation convenience superior to those achievable with conventional polyethylene seals can be expected.

EXAMPLES

[0092] The present invention, while not meant to be limited by, may be better understood by reference to the following examples and tables.

Example 1

[0093] Example 1 illustrates puncture resistance and oxygen barrier demonstrated by an inventive non-MDO blown film sample (Sample 1) comprising 7.5 wt% of the hydrocarbon resin described herein in the core layer formulated as set out herein in comparison with a comparative non-MDO blown film sample (Samples la) comprising 5 wt% of the hydrocarbon resin, based on total weight of polymer in the core layer. Polyethylene and resin products used in the samples include: OPPERA™ PR 100N modifier (as the hydrocarbon resin described herein) (ExxonMobil Chemical Company, Houston, Texas, USA); PE-l polymer (as the first and the fifth polyethylene described herein) (density: 0.940 g/cm³; MI: 0.25 g/lO min; MIR: >60; MWD: ~4) (ExxonMobil Chemical Company, Houston, Texas, USA), PE-2 polymer (as the second polyethylene described herein) (density: 0.918 g/cm³; MI: 1.0 g/lO min; MIR: 16) (ExxonMobil Chemical Company, Houston, Texas, USA), and PE-3 polymer (as the third and the fourth polyethylene described herein) (density: 0.961 g/cm³; MI: 0.70 g/lO min) (ExxonMobil Chemical Company, Houston, Texas, USA). OPPERA™ PR 100N modifier was employed in a pre-blended masterbatch prepared by 50 wt% of OPPERA™ PR 100N modifier and 50 wt% of PE-3 polymer, based on total weight of the masterbatch. Both Sample 1 and Sample la were prepared with an A/Y/B structure at a layer thickness ratio of 1:4:1.

[0094] Puncture resistance was measured based on ASTM D5748, which is designed to provide load versus deformation response under biaxial deformation conditions at a constant relatively low test speed (change from 250 mm/min to 5 mm/min after reach pre-load (0.1N)). Film samples were tested below the cross-head area with the 2.5kN load cell. The sample was about 550mm* 900mm in size, and were conditioned for at least 40 hours at a temperature of 23 ± 2°C and a relative humidity of 50 ± 10%. Maximum puncture force (F_max) is the maximum load achieved by the film sample before the break point, expressed in (N).

[0095] Oxygen transmission rate (OTR) was measured by using a Mocon Oxtran testing system (Model 2/21) in accordance with ASTM D3985 at a temperature of 23 °C and a relative humidity (RH) of 0%, expressed in (cm³/(m²-day)). Water vapor transmission rate (WVTR) was measured by using a Mocon Permatran testing system (Model 3/33 or 3/34) in accordance with ASTM F1249 at a temperature of 38°C and an RH of 90%, expressed in (g/(m²-day)).

[0096] Structure-wise formulations (based on total weight of polymer the layer) and thickness of the samples, accompanied by test results therefor, are depicted in Table 1.

[0097] As shown in Table 1, without MD orientation, the inventive multilayer film featuring a particular amount of the hydrocarbon resin described herein in the core layer can outperform the comparative sample comprising the hydrocarbon in a less amount than the lower limit as set out herein by strengthening puncture resistance by about 20% and significantly reducing oxygen barrier to as low as about 13% of the original value, while maintaining moisture barrier at a close level. This suggests the quantified manner in which the hydrocarbon resin behaves in achieving the above properties and potential of the inventive multilayer film without MD orientation in conveniently modifying oxygen barrier performance at varying levels.

Table 1: Structure- wise formulations (wt%), layer thickness, and test results of Samples 1 & la in Example 1

Example 2

[0098] The inventive sample in Example 1, together with another comparative sample (Sample lb) formulated free of the hydrocarbon resin described herein, was subject to MD orientation at a stretch ratio of 4.4 (the inventive MDO sample referred to as Sample G) prior to test of mechanical, optical, and barrier properties listed herein.

[0099] Tensile properties of the films were measured by a method which is based on ASTM D882 with static weighing and a constant rate of grip separation using a Zwick 1445 tensile tester with a 200N. Since rectangular shaped test samples were used, no additional extensometer was used to measure extension. The nominal width of the tested film sample is 15 mm and the initial distance between the grips is 50 mm. A pre-load of 0.1N was used to compensate for the so called TOE region at the origin of the stress-strain curve. The constant rate of separation of the grips is 5 mm/min upon reaching the pre-load and 5 mm/min to measure 1% Secant modulus (up to 1% strain). 1% Secant modulus is calculated by drawing a tangent through two well defined points on the stress-strain curve. The reported value corresponds to the stress at 1% strain (with x correction). The result is expressed as load per unit area (MPa). The value is an indication of the film stiffness in tension. The 1% Secant modulus is used for thin film and sheets as no clear proportionality of stress to strain exists in the initial part of the curve. The film samples were tested in both MD and TD for tensile strength at break and 1% Secant modulus and test results are expressed by the average value of MD and TD readings.

[00100] Haze (wide-angle scattering) was measured based on ASTM D1003 using a haze meter Haze-Guard Plus AT-4725 from BYK Gardner and is defined as the percentage of transmitted light passing through the bulk of the film sample that is deflected by more than 2.5°. Total transmittance is a measurement of how much light passes through a film (ratio of total transmitted light to incident light). The haze is the ratio in % of the diffused light relative to the total light transmitted by the sample film.

[00101] Gloss was measured based on ASTM D2457 using a gloss meter Micro Gloss 45 from BYK Gardner. A light source is beamed onto the plastic surface at an angle of 45° and the amount of light reflected is measured as a Gloss Unit (GU) value. The higher the gloss value is, the shinier the plastic is.

[00102] Hot tack force refers to the seal strength of a seal while it is still in a molten state, which was determined based on ASTM F1921-12 using a J&B Hot Tack Tester Model 4000 with a 0.5 sec dwell time, with a 0.5 MPa bar pressure pulled at a speed of 200 mm/sec after 0.4 sec of welding seal.

[00103] Maximum puncture force (F_max), OTR, and WVTR were determined according to the test methods as described above. [00104] Structure-wise formulations (based on total weight of polymer the layer), thickness of the samples, and test results therefor, are demonstrated in Table 2. Hot tack results are illustrated in the Figure for comparison of hot tack force and width of hot tack window over the tested temperature range.

[00105] It can be seen from Table 2 that the inventive sample excelled the comparative sample in both mechanical properties, as demonstrated by puncture resistance and 1% Secant Modulus, and optical properties, as demonstrated by haze and gloss. Meanwhile, a 28% reduction in WVTR indicates more flexibility in altering moisture barrier after MD orientation. Moreover, as evidenced by the Figure, addition of the hydrocarbon resin described herein can also highlight sealing performance by moving the peak of the hot tack force curve upwards, as reflected by an increase by 38% in the peak at a sealing temperature of l40°C, accompanied by a broadened hot tack window at a specified hot tack force, e.g. of 6 N. All of the above amounts to an improved overall performance profile, providing advantages not only over the comparative sample without the hydrocarbon resin but also unique to MD orientation and different from those achievable in absence of the MD orientation.

[00106] Therefore, without being bound by theory, by manipulating addition of the hydrocarbon resin and MD orientation, flexibility in fine-tuning film performance in step with property improvement as desired by different end-uses can be expected.

Table 2: Structure- wise formulations (wt%), layer thickness, and test results of Samples G & lb in Example 2

[00107] All documents described herein are incorporated by reference herein, including any priority documents and/or testing procedures. When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. As is apparent from the foregoing general description and the specific embodiments, while forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited thereby.

Claims

CLAIMS What is claimed is:

1. A multilayer film, comprising two outer layers and a core layer between the two outer layers, each layer comprising at least about 50 wt% of a polyethylene polymer, based on total weight of the polymer in the layer, wherein the polyethylene polymer has a density of about 0.910 to about 0.945 g/cm³, a melt index (MI) I2.16 of about 0.1 to about 15 g/lO min, a molecular weight distribution (MWD) of about 1.5 to about 5.5, and a melt index ratio (MIR) I21.6/I2.16 of about 10 to about 100;

wherein the core layer further comprises from about 7 to about 15 wt% of a hydrocarbon resin, based on total weight of the polymer in the core layer and wherein the hydrocarbon resin is selected from the group consisting of an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, and mixtures or combinations thereof.

2. The multilayer film of clam 1, wherein the multilayer film has at least one of the following properties at a film thickness of about 130 pm: (i) a maximum puncture force of at least about 140 N; and/or (ii) an oxygen transmission rate (OTR) of about 100 cm³/(m²-day) or less.

3. The multilayer film of claim 1 or 2, wherein the multilayer film is a machine direction oriented (MDO) film.

4. The multilayer film of claim 3, wherein the MDO film is formed at a stretch ratio of from about 4.0 to about 5.0.

5. The multilayer film of claim 3 or 4, wherein the MDO film has a thickness of about 30 pm or less.

6. The multilayer film of any one of claims 3 to 5, wherein the multilayer film has at least one of the following properties at a film thickness of about 30 pm: (i) a haze of at about 5% or less; (ii) a gloss at 45° of at least about 75 or more; (iii) an average 1% Secant Modulus of at least about 1150 or more; (iv) a maximum puncture force of at least about 45 N; (v) a water vapor transmission rate (WVTR) of at least about 6 g/(m²-day) or less; and/or (vi) a hot tack force of at least about 10 N/30 mm at a sealing temperature of l40°C.

7. The multilayer film of any one of the preceding claims, wherein the polyethylene polymer in the core layer comprises a first polyethylene polymer and/or a second polyethylene polymer, wherein the first polyethylene polymer has a density of about 0.910 to about 0.945 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 2.5 to about 5.5, and an MIR I21_.6/I2.16 of about 25 to about 100; and wherein the second polyethylene polymer has a density of about 0.910 to about 0.940 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR I21_.6/I2.16 of about 10 to about 25.

8. The multilayer film of any one of the preceding claims, wherein the core layer further comprises a third polyethylene polymer, wherein the third polyethylene polymer has a density of at least about 0.945 g/cm³.

9. The multilayer film of any one of the preceding claims, wherein the multilayer film is formed from a hydrocarbon resin in neat form.

10. The multilayer film of any one of the preceding claims, wherein the multilayer film is formed from a blend comprising a hydrocarbon resin and a fourth polyethylene polymer, wherein the fourth polyethylene polymer has a density of at least about 0.945 g/cm³.

11. The multilayer film of claim 10, wherein the weight ratio of the hydrocarbon resin to the fourth polyethylene polymer in the blend is from about 1 :2 to about 2: 1.

12. The multilayer film of claim 10 or 11, wherein the fourth polyethylene polymer is the same as the third polyethylene polymer.

13. The multilayer film of any one of claims 1 to 12, wherein the polyethylene polymer in at least one of the two outer layers comprises a fifth polyethylene polymer, wherein the fifth polyethylene polymer has a density of about 0.910 to about 0.945 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 2.5 to about 5.5, and an MIR I21_.6/I2.16 of about 25 to about 100.

14. The multilayer film of claim 13, wherein the fifth polyethylene polymer is the same as the first polyethylene polymer.

15. The multilayer film of any one of claims 1 to 14, wherein the polyethylene polymer in at least one of the two outer layers is present in an amount of from about 80 to about 100 wt%, based on total weight of polymer in the layer.

16. The multilayer film of any one of claims 1 to 15, wherein the two outer layers are identical.

17. The multilayer film of any one of claims 1 to 16, wherein the thickness ratio of at least one of the outer layers to the core layer is from about 1:2 to about 1:6.

18. A multilayer film comprising two outer layers and a core layer between the two outer layers, wherein:

(a) the core layer comprises a first polyethylene polymer, a second polyethylene polymer, a third polyethylene polymer, and a hydrocarbon resin, wherein the first polyethylene polymer has a density of about 0.910 to about 0.945 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 2.5 to about 5.5, and an MIR I21.6/I2.16 of about 25 to about 100; wherein the second polyethylene polymer has a density of about 0.910 to about 0.940 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR I21_.6/I2.16 of about 10 to about 25; wherein the third polyethylene polymer has a density of at least about 0.945 g/cm³; wherein the hydrocarbon resin is selected from the group consisting of an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, and mixtures or combinations thereof; wherein the first polyethylene polymer and the second polyethylene polymer are present in a combined amount of at least about 50 wt%, based on total weight of polymer in the core layer; wherein the hydrocarbon resin is present in an amount of from about 7 to about 15 wt%, based on total weight of polymer in the core layer; and wherein the multilayer film is formed from a blend of the hydrocarbon resin and the third polyethylene polymer, wherein the weight ratio of the hydrocarbon resin to the third polyethylene polymer in the blend is from about 1 :2 to about 2: 1; (b) each of the two outer layers comprises about 100 wt% of the first polyethylene polymer, based on total weight of polymer in the layer;

wherein the thickness ratio of each of the outer layers to the core layer is about 1:4; and wherein the multilayer film has at least one of the following properties at a film thickness of about 130 pm: (i) a maximum puncture force of at least about 45 N; and/or (ii) an OTR of about 100 cm³/(m²-day) or less.

19. A multilayer film comprising two outer layers and a core layer between the two outer layers, wherein:

(a) the core layer comprises a first polyethylene polymer, a second polyethylene polymer, a third polyethylene polymer, and a hydrocarbon resin, wherein the first polyethylene polymer has a density of about 0.910 to about 0.945 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 2.5 to about 5.5, and an MIR I21_.6/I2.16 of about 25 to about 100; wherein the second polyethylene polymer has a density of about 0.910 to about 0.940 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR I21_.6/I2.16 of about 10 to about 25; wherein the third polyethylene polymer has a density of at least about 0.945 g/cm³; wherein the hydrocarbon resin is selected from the group consisting of an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, and mixtures or combinations thereof; wherein the first polyethylene polymer and the second polyethylene polymer are present in a combined amount of at least about 50 wt%, based on total weight of polymer in the core layer; wherein the hydrocarbon resin is present in an amount of from about 7 to about 15 wt%, based on total weight of polymer in the core layer; and wherein the multilayer film is formed from a blend of the hydrocarbon resin and the third polyethylene polymer, wherein the weight ratio of the hydrocarbon resin to the third polyethylene polymer in the blend is from about 1 :2 to about 2: 1;

(b) each of the two outer layers comprises about 100 wt% of the first polyethylene polymer, based on total weight of polymer in the layer;

wherein the thickness ratio of ach of the outer layers to the core layer is about 1:4;

wherein the multilayer film is an MDO film formed at a stretch ratio of from about 4.0 to about

5.0;

and wherein the multilayer film has at least one of the following properties at a film thickness of about 30 pm: (i) a haze of at about 5% or less; (ii) a gloss at 45° of at least about 75 or more; (iii) an average 1% Secant Modulus of at least about 1150 or more; (iv) a maximum puncture force of at least about 45 N; (v) a water vapor transmission rate (WVTR) of at least about 6 g/(m²-day) or less; and/or (vi) a hot tack force of at least about 10 N/30 mm at a sealing temperature of l40°C.

20. A laminate comprising a substrate and a sealant, wherein the substrate comprises the multilayer film of any one of the preceding claims.

21. A seal comprising the multilayer film of any one of claims 1 to 19 or the laminate of claim 20.

22. A method for making a multilayer film, the method comprising the steps of:

(a) preparing two outer layers and a core layer between the two outer layers, each layer comprising at least about 50 wt% of a polyethylene polymer, based on total weight of polymer in the layer, wherein the polyethylene polymer has a density of about 0.910 to about 0.945 g/cm³, an MI I2.16 of about 0.1 to about 15 g/lO min, an MWD of about 1.5 to about 5.5, and an MIR I21.6/I2.16 of about 10 to about 100;

wherein the core layer further comprises from about 7 to about 15 wt% of a hydrocarbon resin, based on total weight of polymer in the core layer, wherein the hydrocarbon resin is selected from the group consisting of an aliphatic hydrocarbon resin, a hydrogenated aliphatic hydrocarbon resin, an aromatic hydrocarbon resin, a hydrogenated aromatic hydrocarbon resin, a cycloaliphatic hydrocarbon resin, a hydrogenated cycloaliphatic hydrocarbon resin, a polyterpene resin, a terpene-phenol resin, a rosin ester resin, a rosin acid resin, and mixtures or combinations thereof; and

(b) forming a film comprising each of the layers of step (a).

23. The method of claim 22, wherein the film in step (b) is formed by blown extrusion, cast extrusion, coextrusion, blow molding, casting, and/or extrusion blow molding.

24. The method of claim 22 or 23, further comprising:

(c) orienting the film of step (b) in the machine direction orientation.

25. The method of claim 24, wherein the machine direction orientation is conducted at a stretch ratio of from about 4.0 to about 5.0.