Multilayer packaging film with polypropylene and polyethylene

Abstract

A packaging film is disclosed, comprising an oriented polypropylene film coupled to a polyethylene film. The polyethylene film includes a compatibilizer selected from a group including a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer, or a combination thereof; or a stabilizer selected from a group including a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer, or a combination thereof; or both.

Description

TECHNICAL FIELD

[0001] The present application relates to packaging films and packaged products made therefrom. The packaging film comprises a structure and composition aimed at recycling ease. BACKGROUND

[0002] Previous approaches to packaging films have involved combining various types of materials to achieve desired properties such as strength, flexibility, and barrier properties. For instance, polypropylene films have been commonly used in packaging applications due to their excellent mechanical properties and heat resistance. However, polypropylene films alone may lack certain properties such as sealability and impact resistance, which are crucial for packaging applications. To address these limitations, polyethylene films have been incorporated into packaging structures to enhance sealability and impact resistance. The combination of polypropylene and polyethylene films has been explored to leverage the individual strengths of each material in packaging applications. SUMMARY

[0003] In one aspect, a packaging film includes an oriented polypropylene film coupled to a polyethylene film, where the polyethylene film includes at least one of a) a compatibilizer selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butcnc / cthylcnc plastomcr, a polypropylene hctcrophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof, and b) a stabilizer selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof. A packaged product includes a packaging film, and a product, where the packaging film is sealed to form a package and the product is enclosed within the package.

[0004] In another aspect, a packaging film adapted for recycling in a polyolefin recycling stream includes an oriented film includes in a range of from 80% to 100% polypropylene, by weight, a multilayer film includes in a range of from 50% to 100% polyethylene, by weight, and an adhesion layer coupling the oriented film to the multilayer film, where the multilayer film includes at least one of a compatibilizer and a stabilizer, where the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof. The packaging film adapted also includes the stabilizer is selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof.

[0005] In another aspect, a packaging film adapted for recycling in a polyolefin recycling stream includes a biaxially oriented polypropylene film coupled to a multilayer polyethylene film; where the multilayer polyethylene film includes at least one of a compatibilizer and a stabilizer, and where the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrcnc block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof, where the stabilizer is selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof, where the packaging film includes a composition includes the at least one of a compatibilizer and a stabilizer in a range of from 10% to 35%, by weight.

[0006] Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings, in which:

[0008] FIG. 1 is a cross-sectional view of an embodiment of a packaging film including an oriented polypropylene film coupled to a polyethylene film.

[0009] FIG. 2 is a cross-sectional view of an embodiment of a packaging film including an oriented film coupled to a multilayer film by an adhesion layer.

[0010] FIG. 3 is a cross-sectional view of an an embodiment of a packaging film including a biaxially oriented polypropylene film coupled to a multilayer polyethylene film.

[0011] FIG. 4 is a perspective view of an embodiment of a packaged product including a packaging film.

[0012] The drawings show some but not all embodiments. The elements depicted in the drawings are illustrative and not necessarily to scale, and the same (or similar) reference numbers denote the same (or similar) features throughout the drawings. DETAILED DESCRIPTION

[0013] The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments, which are also referred to herein as “examples,” are described in enough detail to enable those skilled in the art to practice the invention. The embodiments may be combined, other embodiments may be utilized, or structural, and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense. Before the present invention is described in such detail, however, it is to be understood that this invention is not limited to particular variations set forth and may, of course, vary.

[0014] Various changes may be made to the invention described and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s), to the objective(s), spirit or scope of the present invention. All such modifications are intended to be within the scope of the disclosure made herein.

[0015] Unless otherwise indicated, the words and phrases presented in this document have their ordinary meanings to one of skill in the art. Such ordinary meanings can be obtained by reference to their use in the art and by reference to general and scientific dictionaries.

[0016] References in the specification to “one embodiment” indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment.

[0017] Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0018] The following explanations of certain terms are meant to be illustrative rather than exhaustive. These terms have their ordinary meanings given by usage in the art and in addition include the following explanations.

[0019] As used herein, the term “and / or” refers to any one of the items, any combination of the items, or all of the items with which this term is associated.

[0020] As used herein, the singular forms “a,” “an,” and “the” include plural reference unless the context clearly dictates otherwise.

[0021] As used herein, the terms “include,” “for example,” “such as,” and the like are used illustratively and are not intended to limit the present invention.

[0022] As used herein, the terms “preferred” and “preferably” refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances.

[0023] Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention.

[0024] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the teachings of the disclosure.

[0025] This disclosure includes packaging film designs that include polyethylene-based sealant films that enable easy recycling of an OPP / PE sealant structure into polyethylene recycling streams. The OPP can be compatibilized and recycled in a polyethylene recycling stream when laminated with properly designed sealant films, including compatibilizers, stabilizers or both. The resulting recycled polypropylene / polyethylene blend can be used for high performance film extrusion when stabilizers are included in the sealant film.

[0026] The packaging films described herein include significant proportions (i.e., greater than 20%, 25%, 30%, 40%, 50% or 60%) of polypropylene. The remaining portion of the packaging films may be polyethylene or they may be mostly polyethylene with some other materials such as ink, adhesive, barrier materials (i.e., EVOH, polyamide, SiOx), etc. Polypropylene is immiscible in polyethylene and therefore is generally not acceptable to add into the polyolefin recycling stream which includes melting and blending the incoming polymer materials. Development by the inventors resulted in the surprising effect that packaging film structures including significant proportions of polypropylene can be rendered recyclable in the polyolefin recycling stream by including specific compatibilizers into the structure. [00271 The properties of immiscible polymer blends depend on factors like the droplet sizes of the dispersed (minor) phase and interfacial adhesion. When droplet sizes are large, resultant light scatter can reduce the transparency of the blend. Low interfacial adhesion can reduce strength properties and promote cavitation during deformation operations like thermoforming and uniaxial or biaxial stretching. An immiscible polymer can cause the articles made from the polymer blend to have less desirable appearance and / or mechanical properties. To improve transparency and strength, it is often desirable to maintain a stabilized distribution of small droplets in a multiphase polymer blend.

[0028] When thermodynamically immiscible polymers are blended in a mixing device and elongational stresses exceed the elastic limits of the minor polymer fractions, those minor fractions break into droplets which become the dispersed phase of the multiphase system. The mixing device can utilize moving elements (e.g., extruder) or it can be stationary (e.g., static mixer).

[0029] The deformation and break-up of viscous droplets in a flow field are governed by the capillary number (Ca). The capillary number compares the relative strengths of the viscous stress (tends to cause droplet elongation) and the interfacial stress (a surface tension effect which tends to make the droplet spherical). When the capillary number reaches a critical value, the viscous stress dominates, and the interfacial stress is insufficiently large to prohibit droplet break-up. That is, surface tension can no longer maintain a spherical droplet, so the droplet elongates and eventually ruptures into smaller units.

[0030] Droplet break-up increases the system free energy due to a concurrent increase in interfacial area since smaller droplets create more interface. When a polymer blend exits the intensive mixing section of a mixing device, that is, it enters a region of lower elongational stress, droplet collisions cause coalescence, total interfacial area decreases, and the system energy decreases as well. Thus, some of the transparency and strength benefits provided by intensive mixing are lost. To minimize coalescence and maintain small droplets, compatibilizers are used to influence polymer interaction at the phase boundaries. Successful compatibilizers show affinities for both phases. These affinities can be chemical (e.g., maleic anhydride modified compatibilizer reacting with amine functionality in polymer droplets (e.g., Dow Retain 3000 used in a PE / polyamide system)) or physical (e.g., compatibilizer chain entangles with droplets and / or continuous phase (e.g., PE / PP block copolymer used in a PE / PP system)). Ideally, a compatibilizer prevents coalescence of dispersed droplets and maintains a stable, multi-phase polymer system.

[0031] As used herein, the term “recyclable” is meant to indicate that the film can be converted into a new useful item by means of reprocessing in a polyolefin recycling stream. Reprocessing may entail washing, separating, melting and forming, among many other steps. Typically, when plastic packaging is reprocessed, the material is mechanically chopped into small pieces and then melted to be reformed into the new product. If multiple incompatible materials are present in the packaging, interactions occur during reprocessing causing gels, brittle material, poor appearance and generally un-usablc or poor-quality products. Using the term “recyclable” indicates that these drawbacks are generally not present. Qualification as a recyclable material is not regulated by any specific agencies but can be obtained from specific groups such as Association of Plastic Recyclers (APR) and How2Recycle™ in the US and Canada. Recyclable films disclosed herein may be suitable for “Store Drop-off” recycling streams which are common in the US, Canada and the UK. These streams may accept the following: 100% polyethylene bags, wraps, and films; very close to 100% polyethylene bags, wraps, and How2Recycle-approved polyethylene-based carrier packing with or without compatibilizer technology. Introduction of a recyclable film into any of these recycling-byreprocessing avenues should not require additional compatibilizer. As used herein, the term "polyolefin recycling stream" refers to an industrial process of reprocessing resulting in a product that can be reformed into a new product. A polyolefin recycling stream may be dedicated to polyethylene (i.e., a polyethylene recycling stream), polypropylene (i.e., a polypropylene recycling stream) or blends of polyolefins.

[0032] The packaging films disclosed herein may be free from materials that contaminate the polyolefin recycling stream. In particular, the packaging films may be free from polyamide (PA), ethylene vinyl alcohol copolymer (EVOH) and / or metal foils (i.e., aluminum foil having thickness above 5 micron). In some packaging films, polymers such as PA and EVOH may be present but at a low level, such as below 5%, by weight of the entire packaging film.

[0033] FIG. 1 shows an embodiment of a packaging film 100 that includes an oriented polypropylene film 10 coupled to a polyethylene film 12.

[0034] As used herein, the term "packaging film" refers to a film capable of being formed into a package. The packaging film may be flexible. A flexible packaging film may be bent or flexed into a shape and then bonded to itself or other packaging components such that a cavity is formed and generally retains the shape. A product may be contained in the cavity. A packaging film may be capable of forming hermetic seals and may provide oxygen and / or moisture barrier properties. A packaging film has two exterior surfaces defined by a length and a width. A packaging film may have a thickness in a range of from 15 microns to 200 microns or any range therein.

[0035] The oriented polypropylene film may be monoaxially oriented or biaxially oriented. The oriented polypropylene film may be of any standard type including, but not limited to, transparent, white, cavitated, heat sealable, matte, glossy, and one or two side treated. The oriented polypropylene film may have a thickness in a range of from 5 micron to 50 micron or any range therein. The oriented polypropylene film may have a propylene content in a range of from 50% to 100% or 80% to 100%, by weight. The oriented polypropylene film may have a propylene content of 100%, by weight. The oriented polypropylene film may have a core including homopolymer polypropylene and polypropylene copolymer skins.

[0036] The oriented polypropylene film may be printed, such that there is ink on either or both surfaces. There may be ink located on the surface of the oriented polypropylene film between the oriented polypropylene film and the polyethylene film.

[0037] As used herein, the term "film" refers to refers to a web built of one or more layers and / or films, all of which are directly adjacent to and connected to each other. A film can be described as having a thickness that is insignificant as compared to the length and width of the film. A film has two major surfaces, the area of which are defined by the length and width of the film. As used herein, the term "layer" refers to refers to a building block of a film. As used herein, a polymer layer may have a composition that is a single material type or a homogeneous blend of materials. A layer may be a single polymer, a blend of materials within a single polymer type or a blend of various polymers, may contain metallic materials and may have additives. Layers may be continuous with the film or may be discontinuous or patterned. A layer has an insignificant thickness (z direction) as compared to the length and width (x-y direction), and therefore is defined to have two major surfaces, the area of which are defined by the length and width of the layer.

[0038] As used herein, a “polyethylene film” may be a monolayer or multilayer film having a composition of at least 50%, at least 70% or at least 90% polyethylene, by weight. The polyethylene film may be unoriented and produced by a blown film or cast process. The polyethylene film may be monoaxially oriented (MDOPE). The polyethylene film may be biaxially oriented (BOPE). The polyethylene film may have a thickness in a range of from 25 microns to 200 microns, or any range therein. The polyethylene film may be transparent or white. The polyethylene film may be capable of forming a heat seal.

[0039] As described herein, films may be oriented. Orientation may be the result of monoaxially oriented (machine direction or transverse direction), or biaxially oriented (machine direction and transverse direction) stretching of the film, increasing the machine direction and / or transverse direction dimension and subsequently decreasing the thickness of the material. Biaxial orientation may be imparted to the film simultaneously or successively. Stretching in either or both directions is subjected to the film in the at a temperature just below the melt temperature of the polymers in the film. In this manner, the stretching causes the polymer chains to “orient”, changing the physical properties of the film. At the same time, the stretching thins the film. The resulting oriented films are thinner and can have significant changes in mechanical properties such as toughness, heat resistance, stiffness, tear strength and barrier. Orientation is typically accomplished by a double- or triple-bubble process, by a tenterframe process or an MDO process using heated rolls. A typical blown film process or cast film process does impart some stretching of the film, but not enough to be considered oriented as described herein. An oriented film may be heat set (i.e., annealed) after orientation, such that it is relatively dimensionally stable under elevated temperature conditions that might be experienced during conversion of the retort film laminate (i.e., printing or laminating) or during the use of the laminate (i.e., heat sealing or retort sterilization). As used herein, the term "unoriented" or the phrase “not oriented” refers to a monolayer or multilayer film, sheet or web that is substantially free of post-extrusion orientation. A film is unoriented if each of the layers or films that are part of the film is substantially free of post extrusion orientation.

[0040] The polyethylene film may include a compatibilizer selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof; or a stabilizer selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof. The polyethylene film may include both a compatibilizer and a stabilizer.

[0041] The compatibilizer may be selected from a group consisting essentially of a propylene / ethylene copolymer, a polypropylene heterophasic olefin copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof. The compatibilizer may be a propylene-rich propylene / ethylene copolymer. The compatibilizer may be a propylene / alpha-olefin copolymer. The stabilizer may be a homogeneously branched linear ethylene polymer. The stabilizer may be an ethylene / hexene copolymer or an ethylene / octene copolymer. As used herein, the polymer layer includes at least one compatibilizer selected from the list of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof.

[0042] Preferably, the compatibilizer has a composition that includes both propylene and ethylene. In some embodiments of the packaging film, the polymer layer includes at least one compatibilizer selected from the list of a propylene / ethylene copolymer, a polypropylene heterophasic olefin copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof. In some embodiments of the packaging film, the polymer layer includes at least one compatibilizer that is selected from a propylene / ethylene copolymer and a polypropylene heterophasic olefin copolymer. In some embodiments the compatibilizer may be a propylene-rich copolymer (i.e., more than 50% of the linkages are propylene).

[0043] A propylene / ethylene copolymer may be a propylene / alpha-olefin copolymer. Examples of a propylene-rich propylene / ethylene copolymer include elastomers such as Dow Versify™ 3401 or 3300 and ExxonMobil Vistamaxx 6102 and 6202, and plastomers such as Dow Versify™ 3000.

[0044] A propylene ethylene copolymer may be a propylene-rich propylene / ethylene / butene terpolymer. Examples of a propylene-rich propylene / ethylene / butene terpolymer include LyondellBassell Adsyl 5 C 30 F and 7416 XCP.

[0045] Examples of 1-butene-rich 1-butene / ethylene copolymer include Mitsui TAFMER BL3110 or BL3450.

[0046] A polypropylene heterophasic olefin copolymer as noted herein preferably has a polypropylene matrix (55 to 90 %, by weight) and an elastomer (10 to 45 %, by weight), such as an ethylene / propylene copolymer or a C4 to CIO alpha-olefin copolymer.

[0047] An olefin block copolymer may be a polypropylene-based olefin block copolymer such as Dow INTUNE™ or may have alternating blocks of rigid and elastomeric segments, such as Dow INFUSE™.

[0048] An olefin block copolymer may be a triblock or multiblock.

[0049] Examples of hydrogenated styrene-butadiene-styrene block copolymer (SEBS) include resins available in the Kraton CirKular+™ product line.

[0050] An ethylene propylene rubber (EPR) as noted herein preferably has a polyethylene component (50 to 80 %, by weight) and a polypropylene (20% to 50%, by weight), such as a random rubber copolymer of ethylene and propylene.

[0051] Examples of ethylene propylene diene monomer (EPDM) rubber include ExxonMobil Vistaion™ and Dow NORDEL™.

[0052] The packaging film composition may include greater than 6%, 8%, 10%, 12% or 14% compatibilizer, by weight. The packaging film composition may include less than 40%, 35% or 30% compatibilizer, by weight. For example, the packaging film composition may include compatibilizer in a range of from 10% to 35%, by weight.

[0053] The theoretical function of the stabilizer is to offset the negative effects of the incompatibility of the mixed olefin (polyethylene and polypropylene) blend. The stabilizer may “build back” or otherwise improve the physical properties of the blend to result in higher quality films containing the recycled blend. As used herein, the “stabilizer” is a homogeneously branched linear ethylene polymer or a heterogeneously branched linear ethylene polymer. The stabilizer may be a homogeneously branched linear ethylene / alpha olefin copolymer, such as an ethylene / hexene copolymer or an ethylene / octene copolymer.

[0054] Examples of polymers that may be used as a stabilizer include C6-mLLDPE, C6-LLDPE, C8-LLDPE, C8-ULDPE, and C8 plastomer. Examples of homogeneously branched linear ethylene polymers include ENGAGE™ grades 8100, 8180 and 8200 (C8 elastomers), available from Dow, Exact™ 0210 (C8 plastomer) from ExxonMobil, TAFMER® grades from Mitsui, and Queo® grades from Borealis. Examples of heterogeneously branched linear ethylene polymers include DOWLEX 3010 available from Dow and ATTANE grades available from Dow.

[0055] As used herein, the phrase “heterogeneous polymer” refers to polymerization reaction products of relatively wide variation in molecular weight and relatively wide variation in composition distribution, i.e., typical polymers prepared, for example, using conventional Ziegler-Natta catalysts. Heterogeneous polymers are useful in various layers of the film used in the present invention. Although there are a few exceptions (such as TAFMER™ linear homogeneous ethylene- and alpha-olefin copolymers produced by Mitsui, using Ziegler-Natta catalysts), heterogeneous polymers typically contain a relatively wide variety of chain lengths and co-monomer percentages.

[0056] As used herein, the phrase “homogeneous polymer” refers to polymerization reaction products of relatively narrow molecular weight distribution and relatively narrow composition distribution. Homogeneous polymers are structurally different from heterogeneous polymers, in that homogeneous polymers exhibit a relatively even sequencing of co-monomers within a chain, a mirroring of sequence distribution in all chains, and a similarity of length of all chains, i.e., a narrower molecular weight distribution. Furthermore, homogeneous polymers are typically prepared using metallocene, or other single-site type catalysts, rather than using Ziegler Natta catalysts.

[0057] More particularly, homogeneous ethylene- and alpha-olefin copolymers may be characterized by one or more methods known to those of skill in the art, such as molecular weight distribution (Mw / Mn ) composition distribution breadth index (CDBI), and narrow melting point range and single melt point behavior. The molecular weight distribution (Mw / Mn), also known as polydispersity, may be determined by gel permeation chromatography. The homogeneous ethylene- and alpha-olefin copolymers useful in this invention generally have (Mw / Mn) of less than 2.7; preferably from about 1.9 to about 2.5; more preferably, from about 1.9 to about 2.3. The composition distribution breadth index (CDBI) of such homogeneous ethylene- and alpha-olefin copolymers will generally be greater than about 70 percent. The CDBI is defined as the weight percent of the copolymer molecules having a comonomer content within 50 percent (i.e., plus or oriented polypropylene film 10 percent) of the median total molar co-monomer content. The CDBI of linear polyethylene, which does not contain a co-monomer, is defined to be 100 percent. The Composition Distribution Breadth Index (CDBI) is determined via the technique of Temperature Rising Elution Fractionation (TREF). CDBI determination clearly distinguishes the homogeneous copolymers used in the present invention (narrow composition distribution as assessed by CDBI values generally above 70 percent) from VLDPEs available commercially which generally have a broad composition distribution as assessed by CDBI values generally less than 55 percent. The CDBI of a copolymer is readily calculated from data obtained from techniques known in the art, such as, for example, temperature rising elution fractionation as described, for example, in Wild et. al., J. Poly. Sci. Poly. Phys. Ed., Vol. 20, p.441 (1982). Preferably, the homogeneous ethylene- and alpha-olefin co-polymers have a CDBI greater than about 70 percent, i.e., a CDBI of from about 70 percent to about 99 percent. In general, the homogeneous ethylene- and alpha-olefin co-polymers in the multi-layer films of the present invention also exhibit a relatively narrow melting point range, in comparison with “heterogeneous copolymers”, i.e., polymers having a CDBI of less than 55 percent. Preferably, the homogeneous ethylene- and alpha-olefin copolymers exhibit an essentially singular melting point characteristic, with a peak melting point (T m ), as determined by Differential Scanning Calorimetry (DSC), of from about 60 degrees centigrade to about 110 degrees centigrade Preferably the homogeneous copolymer has a DSC peak T m of from about 80 degrees centigrade to about 105 degrees centigrade As used herein, the phrase “essentially single melting point” means that at least about 80 percent, by weight, of the material corresponds to a single T m peak at a temperature within the range of from about 60 degrees centigrade to about 110 degrees centigrade, and essentially no substantial fraction of the material has a peak melting point in excess of about 115 degrees centigrade, as determined by DSC analysis. Melting information reported are second melting data, i.e., the sample is heated at a programmed rate of 10 degrees centigrade / min. to a temperature below its critical range. The sample is then reheated (2nd melting) at a programmed rate of 10 degrees centigrade / min. The presence of higher melting peaks is detrimental to film properties such as haze and compromises the chances for meaningful reduction in the seal initiation temperature of the final film.

[0058] A homogeneous ethylene- and alpha-olefin copolymer can, in general, be prepared by the co-polymerization of ethylene and any one or more and alpha-olefins. Preferably, the alphaolefin is a C 4 -C 2 and alpha-mono-olefin, still more preferably, a C 4 -C 8 and alpha-mono-olefin. Still more preferably, the alpha-olefin comprises at least one member selected from the group consisting of butene-1, hexene-1, and octene-1, i.e., 1-butene, 1-hexene, and 1-octene, respectively. Most preferably, the alpha-olefin comprises octene-1, and / or a blend of hexene-1 and butene-1.

[0059] The polyethylene film may be a single layer having a homogeneous composition including the compatibilizer and / or the stabilizer. The polyethylene film may be a multilayer film having one or more layers comprising a compatibilizer and / or one or more layers comprising a stabilizer. Any one or more layers of the polyethylene film may contain both a compatibilizer and a stabilizer.

[0060] As used herein, the phrase “ethylene- and alpha-olefin copolymer” refer to such heterogeneous materials as linear low density polyethylene (LLDPE), linear medium density polyethylene (LMDPE) and very low and ultra low density polyethylene (VLDPE and ULDPE); and homogeneous polymers such as metallocene-catalyzed EXACT™ linear homogeneous ethylene- and alpha-olefin copolymer resins obtainable from Exxon, single-site AFFFNITY™ linear homogeneous ethylene- and alpha-olefin copolymer resins obtainable from Dow, and TAFMER™ linear homogeneous ethylene- and alpha-olefin copolymer resins obtainable from Mitsui. All these materials generally include co-polymers of ethylene with one or more co-monomers selected from C4 to CIO and alpha-olefin such as butene-1, hexene-1, octene-1, etc. in which the molecules of the copolymers comprise long chains with relatively few side chain branches or cross-linked structures. The heterogeneous ethylene- and alphaolefin co-polymer commonly known as LLDPE has a density usually in the range of from about 0.915 g / cm3 to about 0.930 g / cm3, that commonly known as LMDPE has a density usually in the range of from about 0.930 g / cm3 to about 0.945 g / cm3, while those commonly identified as VLDPE or ULDPE have a density lower than about 0.915 g / cm3.

[0061] The packaging film may have a composition that includes in a range of from 15% to 75%, or 20% to 60%, or 20% to 50% polypropylene, by weight. The packaging film may have a composition that includes from 10% to 35% compatibilizer and / or stabilizer, by weight. The packaging film may have a composition that includes from 80% to 99% polyolefin, by weight.

[0062] FIG. 2 shows an embodiment of a packaging film 200 including an oriented film 20, a multilayer film 22 and an adhesion layer 24 coupling the oriented film 20 to the multilayer film 22. The packaging film 200 of this embodiment is similar to the packaging film 100 of the embodiment shown in FIG. 1, and the options and features described for the packaging film 100 of FIG. 1 apply to this packaging film 200 as well. The oriented film 20 of this embodiment is similar to the oriented polypropylene film 10 of the embodiment shown in FIG. 1, and the options and features described for the oriented polypropylene film 10 apply to the oriented film 20 as well. Likewise, the multilayer film 22 of this embodiment is similar to the polyethylene film 12 of the embodiment shown in FIG. 1, and the options and features described for the polyethylene film 12 apply to the multilayer film 22 as well.

[0063] As used herein, the term “coupled” means the joining of two members directly or indirectly to one another. The term "adhesion layer" refers to a layer or material placed on one or more layers or films to promote the adhesion of that layer to another surface. Preferably, adhesion layers are positioned between two layers of a multilayer film to maintain the two layers in position relative to each other and prevent undesirable delamination. Unless otherwise indicated, an adhesion layer can have any suitable composition that provides a desired level of adhesion with the one or more surfaces in contact with the adhesion layer material. An adhesion layer may be an adhesive applied by a lamination process (i.e., one-component, two-component, solventless, solvent based, water based, or energy cured adhesive) or a polyethylene lamination layer applied by an extrusion lamination process.

[0064] FIG. 3 shows an embodiment of a packaging film 300 including a biaxially oriented polypropylene film 30, and a multilayer polyethylene film 32. The packaging film 300 of this embodiment is similar to the packaging film 100 of the embodiment shown in FIG. 1, and the options and features described for the packaging film 100 of FIG. 1 apply to this packaging film 300 as well. The biaxially oriented polypropylene film 30 of this embodiment is similar to the oriented polypropylene film 10 of the embodiment shown in FIG. 1, and the options and features described for the oriented polypropylene film 10 apply to the biaxially oriented polypropylene film 30 as well. Likewise, the multilayer polyethylene film 32 of this embodiment is similar to the polyethylene film 12 of the embodiment shown in FIG. 1, and the options and features described for the polyethylene film 12 apply to the multilayer polyethylene film 32 as well.

[0065] FIG. 4 shows an embodiment of a packaged product 1000 including a packaging film 400 formed into a package and a product (not shown) enclosed within the package. The package can take any form such as a pouch or tray / lid format and may include other packaging components besides the packaging film. The product enclosed within the package made of the packaging film is not limited. The product may be of the type that benefits from protection from moisture, oxygen or light, as may be provided by the packaging film. Examples of products include food, such as chips, crackers, snacks, grains, dry powders, confectionary, candy or nut butters. Examples of products include cosmetic items such as loose powder, facial wipes or lotions. Examples of products include home / industrial products such as cleaning wipes, powdered cleaner or pet food.

[0066] Any of the packaging film embodiments may also include a barrier layer such as, but not limited to EVOH, a metallization layer, or an inorganic oxide layer. The packaging film may also include other layers or materials as long as the inclusion of such materials does not hinder the recyclability of the packaging film. PROPHETIC PACKAGING FILM EXAMPLES

[0067] The inventors envision a number of embodiments of the packaging film, including, but not limited to: OPP / ink / adhesive layer / PE sealant; OPP I ink I polyethylene laminate layer I PE sealant; OPP I ink / adhesive layer I PE-EVOH-PE sealant; OPP I ink I polyethylene laminate layer I PE-EVOH-PE sealant; OPP / ink / adhesive layer / MDOPE sealant; and BOPE I adhesive layer / metalized OPP / adhesive layer / PE sealant. Here OPP is a standard biaxially oriented polypropylene film that has been printed with ink and the sealants listed contain compatibilizer and / or stabilizer as defined herein. PACKAGING FILM EXAMPLES AND DATA

[0068] Several laminations were produced for testing.

[0069] Multilayer sealant films were produced using a blown film process, each film having a composition of sealant A or sealant B. Sealant A includes 46% C4-LLDPE, 28% MDPE, 17.6% C6-mLLDPE and 8.4% LDPE. Sealant B includes 56% C6-LLDPE, 22% C8-LLDPE, 11.5% C6-mLLDPE, 9% C8-plastomer and 1.5% LDPE.

[0070] Control film: An all polyethylene film was produced for comparison. This type of film structure is recyclable in a polyethylene recycling stream but does not have the performance properties of a film that contains an oriented polypropylene film. The structure of the control film was 1.0 mil MDO PE film I ink I adhesive / 1.5 mil sealant B. The control film had a composition that contains 0% polypropylene.

[0071] Film 1: The structure of Film 1 was 70 ga (17.8 micron) BOPP / ink / adhesive / 2 mil sealant A. Film 1 had a composition that contains approximately 25% polypropylene by weight.

[0072] Film 2: The structure of Film 2 was 70 ga BOPP I ink I adhesive / 2 mil sealant B. Film 2 had a composition that contains approximately 25% polypropylene by weight.

[0073] Film 3: The structure of Film 3 was 70 ga BOPP I ink I adhesive / 1.5 mil sealant B. Film 3 had a composition that contains approximately 30% polypropylene by weight.

[0074] The BOPP films used had homopolymer polypropylene cores and polypropylene copolymer skin layers.

[0075] The ink was applied to the BOPP films at slightly over 2 pounds per ream, using 3% dried ink solids.

[0076] The recycling suitability assessment was completed according to standard APR (Association of Plastic Recyclers) protocols. The assessment included both a 50 / 50 blend of the film being tested and control material (reprocessed C4-LLDPE, MI=1, density=0.918), and 100% test film. The test includes production of a film produced from the blended / recycled material and physical testing of the resulting film. The base line of the test results is generated using the Control Film and the results shown are deltas compared to the control. APR guidance is that a film must have no more than a 25% drop in physical properties relative to the control film.

[0077] Impact strength is Dart Drop measured using ASTM D7192 implementing a 0.75 in radius probe, 10.63 +1- 0.02 ft / scc velocity and 10.55 pound weight. MD and TD tear data is Elmendorf Tear measured according to ASTM DI922 using a 200 g pendulum for the MD measurements and a 1,600 g pendulum for the TD measurements.

[0078] Table 1 below compares Film 1 and Film 2. We see a significantly more detrimental impact of the polypropylene content with sealant A versus sealant B, especially when the polypropylene is included at a higher rate. Specifically, there is a marked decrease in MD and TD tear strength and impact strength with the lower performance sealant A. Table 1: Film Properties Change Relative to Control, Values are the % Change in Measurement versus the Control Film Film Composition Tensile Strength Change (%) Elongation at Break Change (%) Tear Strength Change (%) Impact Strength Change (%) MD TD MD TD MD TD Film 1 50 / 50 blend -1.20 -13.17 -7.75 -13.92 -0.31 -22.91 2.01 100% -13.61 -19.79 -12.51 -23.05 -66.24 -59.23 -37.64 Film 2 50 / 50 blend -1.95 -12.83 -15.23 -17.76 45.18 7.17 37.36 100% 8.72 -12.93 -13.70 -21.86 74.48 -1.81 57.18

[0079] Table 2 below compares Film 2 and Film 3. We see that as the polypropylene content increases, the physical properties are diminished. However, in some cases Film 3 may be considered recyclable since the performance properties were diminished greater than 25% only on the test using 100% of the film. Table 2: Film Properties Change Relative to Control, Values are the % Change in Measurement versus the Control Film Film Composition Tensile Strength Change (%) Elongation at Break Change (%) Tear Strength Change (%) Impact Strength Change (%) MD TD MD TD MD TD Film 2 50 / 50 blend -1.95 -12.83 -15.23 -17.76 45.18 7.17 37.36 100% 8.72 -12.93 -13.70 -21.86 74.48 -1.81 57.18 Film 3 50 / 50 blend -9.49 -21.69 -16.78 -18.93 33.95 -10.05 33.05 100% -2.18 -15.98 -25.14 -26.30 5.96 -28.52 32.18

[0080] Embodiment 1: A packaging film comprising: an oriented polypropylene film coupled to a polyethylene film; wherein the polyethylene film comprises at least one of a) a compatibilizer selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof; and b) a stabilizer selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof.

[0081] Embodiment 2: The packaging film of embodiment 1, wherein the oriented polypropylene film is monoaxially oriented.

[0082] Embodiment 3: The packaging film of embodiment 1, wherein the oriented polypropylene film is biaxially oriented.

[0083] Embodiment 4: The packaging film of any one of embodiments 1 to 3, wherein the polyethylene film comprises at least one compatibilizer and at least one stabilizer.

[0084] Embodiment 5: The packaging film of any one of embodiments 1 to 4, further comprising a composition comprising polypropylene in a range of from 15% to 75%, by weight.

[0085] Embodiment 6: The packaging film of any one of embodiments 1 to 5, further comprising a thickness in a range of from 15 microns to 100 microns.

[0086] Embodiment 7: The packaging film of any one of embodiments 1 to 6, wherein the polyethylene film comprises one or more layers.

[0087] Embodiment 8: The packaging film of any one of embodiments 1 to 7, wherein the polyethylene film is oriented.

[0088] Embodiment 9: The packaging film of any one of embodiments 1 to 7, wherein the polyethylene film is not oriented.

[0089] Embodiment 10: The packaging film of any one of embodiments 1 to 9, wherein the compatibilizer is a propylene-rich propylene / ethylene copolymer.

[0090] Embodiment 11: The packaging film of any one of embodiments 1 to 10, wherein the compatibilizer is a propylene / alpha-olefin copolymer.

[0091] Embodiment 12: The packaging film of any one of embodiments 1 to 11, wherein the stabilizer is a homogeneously branched linear ethylene polymer.

[0092] Embodiment 13: The packaging film of embodiment 12, wherein the stabilizer is an ethylene / hexene copolymer or an ethylene / octene copolymer.

[0093] Embodiment 14: A packaging film adapted for recycling in a polyolefin recycling stream comprising: an oriented film comprising in a range of from 80% to 100% polypropylene, by weight; a multilayer film comprising in a range of from 50% to 100% polyethylene, by weight; and an adhesion layer coupling the oriented film to the multilayer film; wherein the multilayer film comprises at least one of a compatibilizer and a stabilizer; wherein the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof; and the stabilizer is selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof.

[0094] Embodiment 15: The packaging film of embodiment 14, further comprising a composition comprising the compatibilizer in a range of from 10% to 35%, by weight.

[0095] Embodiment 16: The packaging film of embodiment 14 or 15, wherein the multilayer film is oriented.

[0096] Embodiment 17: The packaging film of embodiment 14 or 15, wherein the multilayer film is not oriented.

[0097] Embodiment 18: The packaging film of any one of embodiments 14 to 17, further comprising a second adhesion layer coupling a biaxially oriented polyethylene film to the oriented film opposite of the multilayer film, and the packaging film comprises a thickness in a range of from 25 micron to 250 micron.

[0098] Embodiment 19: The packaging film of any one of embodiments 14 to 18, further comprising ink coupled to the oriented film.

[0099] Embodiment 20: The packaging film of any one of embodiments 1-17 or 19, further comprising a thickness in a range of from 15 to 100 micron.

[0100] Embodiment 21: The packaging film of any one of embodiments 1 to 20, wherein the film composition comprises polyolefin in a range of from 80% to 99%, by weight.

[0101] Embodiment 22: A packaging film adapted for recycling in a polyolefin recycling stream comprising a biaxially oriented polypropylene film coupled to a multilayer polyethylene film; wherein the multilayer polyethylene film comprises at least one of a compatibilizer and a stabilizer; and wherein the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof; wherein the stabilizer is selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof; wherein the packaging film comprises a composition comprising the at least one of a compatibilizer and a stabilizer in a range of from 10% to 35%, by weight.

[0102] Embodiment 23: The packaging film of any one of embodiments 1 to 22, wherein the packaging film is recyclable in a polyethylene recycle stream.

[0103] Embodiment 24: The packaging film of any one of embodiments 1 to 23, wherein the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a polypropylene heterophasic olefin copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof.

[0104] Embodiment 25: A packaged product comprising: a packaging film of any one of embodiments 1 to 24, and a product; wherein the packaging film is sealed to form a package and the product is enclosed within the package.

Claims

1. A packaging film comprising:an oriented polypropylene film coupled to a polyethylene film;wherein the polyethylene film comprises at least one of a) a compatibilizer selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof; and b) a stabilizer selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof.

2. The packaging film of claim 1, wherein the oriented polypropylene film is monoaxially oriented.

3. The packaging film of claim 1, wherein the oriented polypropylene film is biaxially oriented.

4. The packaging film of claim 1, wherein the polyethylene film comprises at least one compatibilizer and at least one stabilizer.

5. The packaging film of claim 1, further comprising a composition comprising polypropylene in a range of from 15% to 75%, by weight.

6. The packaging film of claim 1, further comprising a thickness in a range of from 15 microns to 100 microns.

7. The packaging film of claim 1, wherein the polyethylene film comprises one or more layers.

8. The packaging film of claim 1, wherein the polyethylene film is oriented.

9. The packaging film of claim 1, wherein the polyethylene film is not oriented.

10. The packaging film of claim 1, wherein the compatibilizer is a propylene-richpropylene / ethylene copolymer.

11. The packaging film of claim 1, wherein the compatibilizer is a propylene / alpha-olefin copolymer.

12. The packaging film of claim 1, wherein the stabilizer is a homogeneously branched linear ethylene polymer.

13. The packaging film of claim 12, wherein the stabilizer is an ethylene / hexene copolymer or an ethylene / octene copolymer.

14. A packaging film adapted for recycling in a polyolefin recycling stream comprising:an oriented film comprising in a range of from 80% to 100% polypropylene, by weight;a multilayer film comprising in a range of from 50% to 100% polyethylene, by weight; andan adhesion layer coupling the oriented film to the multilayer film;wherein the multilayer film comprises at least one of a compatibilizer and a stabilizer;wherein the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof; andthe stabilizer is selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof.

15. The packaging film of claim 14, further comprising a composition comprising the compatibilizer in a range of from 10% to 35%, by weight.

16. The packaging film of claim 14, wherein the multilayer film is oriented.

17. The packaging film of claim 14, wherein the multilayer film is not oriented.

18. The packaging film of claim 14, further comprising a second adhesion layer coupling a biaxially oriented polyethylene film to the oriented film opposite of the multilayer film, and the packaging film comprises a thickness in a range of from 25 micron to 250 micron.

19. The packaging film of claim 14, further comprising ink coupled to the oriented film.

20. The packaging film of claim 14, further comprising a thickness in a range of from 15 to 100 micron.

21. The packaging film of claim 14, wherein the film composition comprises polyolefin in a range of from 80% to 99%, by weight.

22. A packaging film adapted for recycling in a polyolefin recycling stream comprising a biaxially oriented polypropylene film coupled to a multilayer polyethylene film;wherein the multilayer polyethylene film comprises at least one of a compatibilizer and a stabilizer; andwherein the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a 1-butene rich 1-butene / ethylene plastomer, a polypropylene heterophasic olefin copolymer, an olefin block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof;wherein the stabilizer is selected from a group consisting essentially of a homogeneously branched linear ethylene polymer, a heterogeneously branched linear ethylene polymer and a combination thereof;wherein the packaging film comprises a composition comprising the at least one of a compatibilizer and a stabilizer in a range of from 10% to 35%, by weight.

23. The packaging film of claim 1, wherein the packaging film is recyclable in a polyethylene recycle stream.

24. The packaging film of claim 1, wherein the compatibilizer is selected from a group consisting essentially of a propylene / ethylene copolymer, a polypropylene heterophasic olefin copolymer, an ethylene propylene rubber, an ethylene propylene diene monomer and a combination thereof.

25. A packaged product comprising:a packaging film of claim 1, and a product;wherein the packaging film is sealed to form a package and the product is enclosed within the package.

Images