Multilayer film containing post-consumer recycled (PCR) material with higher tear resistance.

Abstract

In one embodiment, the multilayer film comprises a first outer layer, a second outer layer, and at least one core layer located between the first and second outer layers, wherein the at least one core layer comprises a post-consumer recycled (PCR) polyethylene resin having a density of 0.930 to 0.950 g / cc as determined according to ASTM D792, a melt index (I2) of 1.0 to 3.0 dg / min as determined according to ASTM D1238 (2.16 kg, 190°C), and a molecular weight distribution (MWD = Mw / Mn) of 5 to 12, and the first and second outer layers comprise an ethylene-based polymer, a propylene-based polymer, or a combination thereof.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims the benefits of U.S. Provisional Patent Application No. 63 / 517,027, filed on 1 August 2023, which is incorporated herein by reference in its entirety.

[0002] The embodiments described herein generally relate to multilayer films, more specifically to multilayer films containing recycled resins. [Background technology]

[0003] The market is seeing a growing trend towards using post-consumer recycled (PCR) materials in low- and high-performance stretched films for unitization applications, ensuring favorable stability, integrity, and safety of unit loads while simultaneously providing a sustainable solution.

[0004] New legislation and / or brand owners' efforts to reach a certain level of PCR content in packaging materials over the next few years have created new challenges in recent years. Based on this new market demand, many companies are working to replace some of their virgin resins with post-consumer resins.

[0005] Currently, the suitable use of PCR in stretched films is limited due to the potential for contaminants (e.g., cellulose impurities from labels), the poor and / or variability of the mechanical properties of recycled resins, and processing disadvantages, such as degradation that can lead to pressure fluctuations or breakage in the molten web.

[0006] PCR can also affect the performance of the film, as it may reduce the maximum elongation (ultimate stretch) the film can achieve, as well as other mechanical properties such as puncture and tear resistance.

[0007] As a result, PCRs that minimize contaminants and maintain or even enhance abuse properties, such as tear resistance, are still needed today. [Overview of the project]

[0008] Embodiments of this disclosure meet sustainability needs while maintaining or improving heavy-duty performance.

[0009] In one embodiment, the multilayer film comprises a first outer layer, a second outer layer, and at least one core layer located between the first and second outer layers, wherein the at least one core layer comprises a post-consumer recycled (PCR) polyethylene resin having a density of 0.930–0.950 grams / cubic centimeter (g / cc) as determined according to ASTM D792, a melt index (I2) of 1.0–3.0 decigrams / min (dg / min) as determined according to ASTM D1238 (2.16 kg, 190°C), and a molecular weight distribution (MWD=Mw / Mn) of 5–12, and the first and second outer layers comprise an ethylene-based polymer, a propylene-based polymer, or a combination thereof.

[0010] Additional features and benefits are described below in the “Modes for Carrying Out the Invention,” some of which will be readily apparent to those skilled in the art from that description, or will be recognized by carrying out the embodiments described herein, including the “Modes for Carrying Out the Invention” and the “Claims.”

[0011] It should be understood that both the general description above and the detailed description below are intended to illustrate various embodiments and to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. [Brief explanation of the drawing]

[0012] [Figure 1] A schematic diagram illustrating one embodiment of the multilayer film of the present invention is shown. [Modes for carrying out the invention]

[0013] definition "Polymer" refers to a polymer compound prepared by polymerizing monomers, whether of the same type or different types. Therefore, the term polymer encompasses the terms homopolymer (used to refer to a polymer prepared from only one type of monomer, with the understanding that trace amounts of impurities may be incorporated into the polymer structure) and copolymer or interpolymer. Trace amounts of impurities (e.g., catalyst residue) may be incorporated into and / or present within the polymer. The polymer may be a single polymer or a polymer blend.

[0014] As used herein, the term “copolymer” means a polymer formed by the polymerization reaction of at least two structurally distinct monomers. The term “copolymer” includes terpolymers. For example, an ethylene copolymer, such as an ethylene-propylene copolymer, comprises at least two structurally distinct monomers (for example, an ethylene-propylene copolymer comprises at least two copolymer units of ethylene monomer and propylene monomer), and optionally may contain additional monomers or functional materials or modifiers, such as acids, acrylates, or anhydride functional groups. In other words, the copolymers described herein comprise at least two structurally distinct monomers, and copolymers may consist of only two structurally distinct monomers, but they do not necessarily consist of only two structurally distinct monomers, and may contain additional monomers or functional materials or modifiers.

[0015] A "multilayer film" refers to any structure having two or more layers. For example, a multilayer structure may have five or more layers, such as 6, 7, 8, 9, 10, or 11 layers. In embodiments, a multilayer film may have an odd number of layers, such as 5, 6, 9, or 11 layers.

[0016] As used herein, “polyethylene” means “ethylene-based polymer” and refers to a polymer containing more than 50% by weight of units derived from ethylene monomers. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more comonomers). Common forms of polyethylene known in the art include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE), very low-density polyethylene (VLDPE), single-site catalyst linear low-density polyethylene (m-LLDPE) including both linear low-density resins and substantially linear low-density resins, medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).

[0017] "Ethylene-propylene copolymer" refers to an ethylene-based polymer having a propylene comonomer. The ethylene-propylene copolymer of this disclosure may contain more than half (more than 50% by weight) of ethylene monomer residues based on the total polymer weight of the ethylene-propylene copolymer. The remainder of the polymer weight of the ethylene-propylene copolymer may consist of propylene monomer residues.

[0018] "Polypropylene" or "propylene polymer" means a polymer containing more than 50% by weight of units derived from propylene monomer. This includes polypropylene homopolymers or copolymers (meaning units derived from comonomers such as ethylene). Common forms of polypropylene known in the art include homopolymer polypropylene (hPP), random copolymer polypropylene (rcPP), impact copolymer polypropylene (hPP+, with at least one elastomer-based impact modifier) ​​(ICPP), high impact polypropylene (HIPP), high melt strength polypropylene (HMS-PP), isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), and combinations thereof.

[0019] A "residue" refers to a portion of a polymer derived from a specific monomer.

[0020] The term “LDPE” may also be called “high-pressure ethylene polymer” or “highly branched polyethylene,” and is defined to mean that the polymer is partially or completely homopolymerized or copolymerized in an autoclave or tubular reactor at a pressure greater than 14,500 psi (100 MPa) using a free radical initiator such as a peroxide (see, for example, U.S. Patent No. 4,599,392, incorporated herein by reference).

[0021] The term "LLDPE" includes resins made using conventional Ziegler-Natta catalyst systems as well as single-site catalysts such as metallocenes (the latter may also be referred to as "m-LLDPE"). LLDPE contains fewer long-chain branches than LDPE and includes substantially linear ethylene polymers further defined in U.S. Patent No. 5,272,236, U.S. Patent No. 5,278,272, U.S. Patent No. 5,582,923, and U.S. Patent No. 5,733,155, homogeneous branched linear ethylene polymer compositions such as those of U.S. Patent No. 3,645,992, heterogeneous branched ethylene polymers prepared according to the process disclosed in U.S. Patent No. 4,076,698, and blends thereof (such as those disclosed in U.S. Patent No. 3,914,342 or U.S. Patent No. 5,854,045). LLDPE can be made using any type of reactor or reactor configuration known in the art via gas-phase, liquid-phase, or slurry polymerization, or any combination thereof; reactors include, but are not limited to, gas-phase and liquid-phase reactors.

[0022] "Recycled resin" refers to a resin that has been incorporated into a product and then remelted to form a recycled resin. The term "recycled resin" refers to a resin that has been mechanically recycled, melted, and reincorporated into a new product. "Recycled resin" does not include chemically recycled resins in which the polymer has been broken down into its constituent monomers and incorporated into a new virgin polymer. The term "recycled resin" encompasses both pre-consumer recycled polymers and post-consumer resins.

[0023] The terms “pre-consumer recycled polymer” and “post-industrial recycled polymer” refer to polymers that include blends of polymers recovered from pre-consumer materials, as defined by ISO 14021. Therefore, the collective term “pre-consumer recycled polymer” includes blends of polymers recovered from materials separated from waste streams during the manufacturing process. The collective term “pre-consumer recycled polymer” excludes the reuse of materials that are produced in a process and can be reused within the same process that produced them, such as reprocessing, re-grinding, or scrap.

[0024] As used herein, the term “post-consumer resin” (or “PCR”) refers to polymer materials that include materials previously used in consumer or industrial applications, i.e., pre-consumer recycled polymers and post-industrial recycled polymers. PCRs are typically recovered from recycling programs and recycling plants. PCRs may include one or more of the following: ethylene-based polymers such as LDPE, LLDPE, polyethylene, polypropylene, polyester, poly(vinyl chloride), polystyrene, acrylonitrile butadiene styrene, polyamide, ethylene vinyl alcohol, ethylene vinyl acetate, or polyvinyl chloride. PCRs may contain one or more contaminants. Contaminants may be the result of the use of the polymer material before any modifications were made for reuse. For example, contaminants may include paper, ink, food residue, or other recycled materials, in addition to polymers that may result from the recycling process. PCRs are different from virgin polymer materials. Virgin polymer materials (such as virgin polyethylene resins) do not contain materials that have been previously used in consumer or industrial applications. Virgin polymer materials have not undergone or been subjected to heating or molding processes after the initial polymer manufacturing process. The physical, chemical, and flow properties of PCR polyethylene resins differ from those of virgin polymer resins, which may present challenges in incorporating PCR into formulations for commercial use.

[0025] Embodiment As shown in FIG. 1, the multilayer film 100 may include a first outer layer 102, a second outer layer 104, and a core layer 106. The core layer 106 may be located between the first outer layer 102 and the second outer layer 104. In one or more embodiments, the multilayer film may include one core layer or multiple core layers, for example, three core layers. Regardless of whether it includes one or more core layers, one or more of the core layers may include a post-consumer recycled (PCR) polyethylene resin.

[0026] Core layer The core layer 106 may include a post-consumer recycled (PCR) polyethylene resin having a density of 0.930 to 0.950 g / cc determined according to ASTM D792, a melt index (I2) of 1.0 to 3.0 dg / min determined according to ASTM D1238 (2.16 kg, 190° C.), and a molecular weight distribution (MWD = Mw / Mn) of 5 to 12 measured by conventional gel permeation chromatography (GPC). The MWD is defined as M w / M n where M w is the weight average molecular weight and M n is the number average molecular weight.

[0027] In a further embodiment, the PCR polyethylene resin may have a density of 0.935 g / cc to 0.950 g / cc, 0.935 g / cc to 0.945 g / cc, 0.930 g / cc to 0.945 g / cc, 0.930 g / cc to 0.940 g / cc, 0.940 g / cc to 0.950 g / cc, or any subset thereof.

[0028] In other embodiments, the PCR polyethylene resin may have a melt index (I2) of 1 dg / min to 2.5 dg / min, 1 dg / min to 2 dg / min, 1.5 dg / min to 3 dg / min, 1.5 dg / min to 2.5 dg / min, 1.5 dg / min to 2.5 dg / min, or any subset thereof.

[0029] In other embodiments, the PCR polyethylene resin may have MWDs of 6-12, 7-12, 7-11, 7-10, or any subset thereof.

[0030] PCR polyethylene resin may contain 15 to 125 gel levels (GI200), where the number of defects (24.6 cm²) is defined as the equivalent circle diameter being in the range of 200 to 400 μm. 3 (per film). In further embodiments, PCR polyethylene resins may have a gel level of 15 to 100. Typical virgin resins have a gel level of less than 10.

[0031] In some embodiments, the PCR polyethylene resin may optionally include several additional polyolefin PCR materials, such as a propylene-based PCR resin or an additional ethylene-based PCR resin.

[0032] The core layer may contain only PCR polyethylene resin, but core layer 106 may contain a blend of PCR polyethylene resin and a virgin ethylene-based polymer. In one or more embodiments, the core layer may contain 5-100% by weight, 5-50% by weight, 10-40% by weight, or 20-40% by weight of PCR polyethylene resin. Conversely, the core layer may contain 0-95% by weight, 50-95% by weight, 60-90% by weight, or 60-80% by weight of a virgin ethylene-based polymer.

[0033] The core layer 106 may also contain a virgin ethylene polymer having a density of 0.900 g / cc to 0.968 g / cc and a melt index (I2) of 0.2 to 5 dg / min. In one embodiment, the virgin ethylene polymer may include LLDPE.

[0034] LLDPE may have a melt index (I2) of 0.2 dg / min to 5 dg / min, 0.5 dg / min to 4 dg / min, 0.5 dg / min to 3 dg / min, 2 dg / min to 5 dg / min, 3 dg / min to 6 dg / min, or any subset thereof. In an embodiment, the multilayer film 100 may be a cast-stretched film, and the LLDPE may have a melt index (I2) of 2 dg / min to 5 dg / min. In an embodiment, the multilayer film 100 may be an inflation film, and the LLDPE may have a melt index (I2) of 0.5 dg / min to 3 dg / min.

[0035] LLDPE may have a density of 0.916 g / cc to 0.935 g / cc. In embodiments, LLDPE may have a density of 0.916 g / cc to 0.930 g / cc, 0.916 g / cc to 0.925 g / cc, 0.916 g / cc to 0.920 g / cc, 0.925 g / cc to 0.935 g / cc, 0.920 g / cc to 0.930 g / cc, or any subset thereof.

[0036] In a further embodiment, the core layer 106 may include LDPE. The LDPE may have a melt index (I2) in the range of 1 dg / min to 50 dg / min. All individual values ​​and subranges of 1 dg / min to 50 dg / min are disclosed and included herein. For example, the LDPE may have a melt index (I2) in the range of 1 dg / min to 20 dg / min, 2 dg / min to 10 dg / min, 2 dg / min to 8 dg / min, or any subset thereof.

[0037] outer layer Referring again to Figure 1, the first outer layer 102 and the second outer layer 104 include an ethylene-based polymer, a propylene-based polymer, or a combination thereof. While the disclosed embodiments focus on virgin ethylene-based polymers or unused propylene-based polymers in the first outer layer 102 and the second outer layer 104, it is intended that the first outer layer 102 and the second outer layer 104 may include PCR polyethylene resin.

[0038] In one embodiment, the first outer layer 102 may function as a release layer. The release layer may, for example, have non-adhesive properties or lower adhesive properties than the adhesive layer. The first outer layer 102 may contain any material suitable for use as a release layer. The second outer layer 104 may be an adhesive layer. The adhesive layer may, for example, allow the multilayer film 100 to adhere to itself when it is wrapped around a package. The second outer layer 104 may contain any material suitable for use as an adhesive layer.

[0039] The first outer layer 102, the second outer layer 104, or both thereof may contain an ethylene-based polymer such as LLDPE having a density range and a melt index (I2) range. In embodiments, the first outer layer 102 may contain at least 50% by weight, for example, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or even more than 99% by weight of LLDPE.

[0040] In some embodiments, the first outer layer 102 and / or the second outer layer 104 may include LDPE. The LDPE may have a melt index (I2) in the range of 1 dg / min to 50 dg / min. All individual values ​​and subranges of 1 dg / min to 50 dg / min are disclosed and included herein. For example, the LDPE may have a melt index (I2) in the range of 1 dg / min to 20 dg / min, 2 dg / min to 10 dg / min, 2 dg / min to 8 dg / min, or any subset thereof.

[0041] In some embodiments, the ethylene-based polymer of the first outer layer 102 and / or the second outer layer 104 may independently contain 0% to 30% by weight of LDPE based on the total weight of each layer. All individual values ​​of 0% to 30% by weight are disclosed herein and included therein. For example, the multilayer film 100 may contain 0% to 25% by weight, 0% to 20% by weight, 0% to 10% by weight, 0% to 5% by weight, 5% to 30% by weight, 5% to 20% by weight, or any subset thereof, based on the total polymer weight of each layer.

[0042] The first outer layer 102, the second outer layer 104, or both may contain a propylene-based polymer. The polypropylene may contain a polypropylene homopolymer or a random copolymer. The polypropylene may be catalyzed by a Ziegler-Natta catalyst, a single-site / metallocene catalyst, or a post-metallocene catalyst.

[0043] Polypropylene may contain at least 51% by weight of propylene monomer, based on the total polymer weight of the polypropylene. In embodiments, polypropylene may contain at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 75% by weight, at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 99% by weight, at least 99.9% by weight, or even at least 100% by weight of propylene monomer, based on the total polymer weight of the polypropylene.

[0044] In one embodiment, the propylene polymer is a polypropylene plastomer. The polypropylene plastomer may have a density of 0.850 g / cc to 0.910 g / cc. In embodiments, the polypropylene plastomer may have a density of 0.860 g / cc to 0.890 g / cc, 0.860 g / cc to 0.880 g / cc, 0.860 g / cc to 0.875 g / cc, 0.860 g / cc to 0.870 g / cc, 0.865 g / cc to 0.870 g / cc, or any subset thereof.

[0045] Polypropylene plastomers may have a melt flow rate (MFR) of 2 dg / min to 50.0 dg / min. In embodiments, polypropylene plastomers may have an MFR of 5 dg / min to 25 dg / min, 6 dg / min to 15 dg / min, 7 dg / min to 10 dg / min, 7.5 dg / min to 8.5 dg / min, or any subset thereof.

[0046] The first outer layer 102, the second outer layer 104, or both thereof are monomaterials and may contain only ethylene-based polymers or propylene-based polymers, but the first outer layer 102, the second outer layer 104, or both thereof may contain a blend of ethylene-based polymers or propylene-based polymers. In one or more embodiments, the first outer layer 102, the second outer layer 104, or both thereof may contain an amount of ethylene-based polymer ranging from a lower limit of 0, 10, 20, 30, 40, 50, 60, 70, 80, or 90% by weight to an upper limit of 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10% by weight. Conversely, the first outer layer 102, the second outer layer 104, or both thereof may contain a propylene polymer in an amount ranging from a lower limit of 0, 10, 20, 30, 40, 50, 60, 70, 80, or 90% by weight to an upper limit of 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10% by weight.

[0047] Middle class Optionally, an intermediate layer (not shown) may be provided between the core layer 106 and the first outer layer 102 and the second outer layer 104. Similar to the first outer layer 102 and the second outer layer 104, the intermediate layer may contain an ethylene-based polymer, a propylene-based polymer, or a combination thereof.

[0048] The intermediate layer may be a monomaterial and may contain only an ethylene-based polymer or a propylene-based polymer. However, these layers may also contain a blend of ethylene-based polymers or propylene-based polymers. In one or more embodiments, the intermediate layer may contain an amount of ethylene-based polymer ranging from a lower limit of 0, 10, 20, 30, 40, 50, 60, 70, 80, or 90% by weight to an upper limit of 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10% by weight. Conversely, the intermediate layer may contain an amount of propylene-based polymer ranging from a lower limit of 0, 10, 20, 30, 40, 50, 60, 70, 80, or 90% by weight to an upper limit of 100, 90, 80, 70, 60, 50, 40, 30, 20, or 10% by weight.

[0049] additives It should be understood that any of the aforementioned layers may further contain one or more additives known to those skilled in the art, such as antioxidants, ultraviolet stabilizers, heat stabilizers, slip agents, anti-tack agents, antistatic agents, pigments or colorants, processing aids, crosslinking catalysts, flame retardants, fillers, and foaming agents. A layer may contain any amount of such additives, based on the weight of the layer, such as 0% to 10% by weight, 0% to 5% by weight, 0% to 1% by weight, 0% to 0.1% by weight, 0% to 0.001% by weight, or any subset thereof.

[0050] Multilayer film The multilayer films 100 and 200 may have a thickness of less than 70 μm. As mentioned above, it is desirable to produce a multilayer film that can satisfy the required mechanical properties while minimizing the film thickness. In the embodiment, the multilayer films 100 and 200 may have a thickness of less than 60 μm, less than 50 μm, less than 40 μm, less than 30 μm, less than 25 μm, less than 23 μm, less than 19 μm, 10 μm to 70 μm, 10 μm to 50 μm, 10 μm to 30 μm, 10 μm to 25 μm, 10 μm to 20 μm, 15 μm to 70 μm, 15 μm to 50 μm, 15 μm to 30 μm, 15 μm to 25 μm, 15 μm to 20 μm, or any subset thereof.

[0051] It should be understood that the multilayer film 100 may include three or more layers. In an embodiment, the multilayer film may include six or more layers, such as five, seven, nine, or eleven layers. The multilayer film 100 may be an inflation film or a cast film. In one embodiment, the cast film is a stretched film. In embodiments of the stretched film, the multilayer film has an ESTL tear resistance of more than 7 seconds, an ESTL puncture of more than 5.5 pounds, and an ultimate elongation of more than 200%.

[0052] Test method Density

[0053] The density is measured according to ASTM D792 and expressed in grams per cubic centimeter (g / cc).

[0054] Melt index (I2) The melt index (I2) is measured according to ASTM D1238-10 at 190 °C and 2.16 kg, method B, and the elution amount is expressed in dg / min.

[0055] Melt flow rate (MFR) The melt flow rate is measured according to ASTM D1238-10 at 230 °C and 2.16 kg, method B, and the elution amount is expressed in dg / min.

[0056] Conventional GPC (M w , M n , M w / M n ) Details of the GPC method can be found in U.S. Patent Application No. 17 / 632598, which is incorporated herein by reference.

[0057] Number of gel level (GI200) defects The defect count is a measure of defects detected in extruded films using optical imaging techniques, in accordance with the practices and guidance in ASTM D7310-20, "Standard Practice for Defect Detection and Rating of Plastic Film Using Optical Sensors." The defect count is calculated by counting the number of optical defects with an equivalent circle diameter within a series of defined ranges: 200–400 μm, 400–800 μm, 800–1600 μm, and 1600 μm or larger, across 24.6 cm². 3 This is reported as the number of particles per unit. This is measured by the Optical Control Systems Film Surface Analyzer FSA100 (OCS FSA100) optical imaging system. The OCS FSA100 optical imaging system consists of an illumination unit, a charge-coupled device (CCD) line scan camera, and a computer with image / data analysis software version 5.0.4.6.

[0058] The OCS FSA100 optical imaging system detects defects that obscure the transmission of light from halogen light sources. The average grayscale was set to 170 with a threshold sensitivity setting of 35%. Furthermore, the gain of the CCD system can be adjusted to compensate for film haze. The imaging system creates a composite region of each defect by adding defect pixels from each subsequent line scan. The system then reports the number of defects that were within a user-defined size range based on the diameter of the circle with the corresponding area.

[0059] Film production is achieved by an OCS ME19 cast film extrusion system equipped with a fixed lip coat hanger die. The die gap is 500 μm × 15 cm. The OCS ME19 cast film extrusion system is a single-screw extruder with a 19 mm screw provided by OCS. The screw design has an L / D compression ratio of 3:1 and has pineapple mixed chips. The total extrusion system mass output is 10 ± 5 kg / hour. The film thickness is 38 μm, which was achieved by adjusting the chill roll. Nitrogen purging was used at the extruder feed port. The temperature profile was in the range of 135°C to 190°C to achieve a target extrusion pressure of 220–240 bar.

[0060] The PCR resin was analyzed by diluting it with virgin polyethylene (50 / 50 wt%) in a dry blend before extrusion. The virgin polyethylene used for dilution was LDPE 132I (density of 0.921 g / cm³ and melt index of 0.25 dg / min measured at 190°C and 2.16 kg) commercially available from The Dow Chemical Company.

[0061] ESTL extreme stretching This test was performed using an ESTL FPT-750 apparatus. The test involves gradually stretching the film with rollers at different speeds until the film breaks, similar to the mechanism of a pallet wrapper. The test reports the force at the unwinding section, the force on the winding drum, the force required to stretch the film, the peeling angle, the peeling force, and the unwinding noise.

[0062] Extreme extension of highlights This test was also performed using the ESTL FPT-750 apparatus. Similar to the pallet wrapper mechanism, this test involves gradually stretching the film with rollers at different speeds until the film breaks. The test reports the maximum elongation at which the film breaks due to stretching.

[0063] ESTL puncture This test was performed using an ESTL FPT-750 instrument. The film was stretched to a specific predetermined pre-stretch level (250%) and then paused for 10 seconds. The film was then clamped in a frame and counterframe, allowing a sharp puncture probe to move at a constant predetermined speed until it reached the film. In this test, the maximum force, displacement, and energy required to puncture the film were reported.

[0064] ESTL tear propagation This test was performed using an ESTL FPT-750 apparatus. The film is stretched to a specific predetermined pre-stretch level (250%). The film is then clamped in a frame and counter frame to allow a sharp blade to move at a constant predetermined speed until it reaches the film. After the cut is made, the clamps are released and the force on the film is monitored. If the tear does not propagate, the winding drum slowly begins to pull and continues to pull until the film is completely ruptured. [Examples]

[0065] [Table 1]

[0066] ELITE® 5230G, DOWLEX® 2047G, and DOWLEX® 2247G, manufactured by Dow® Inc. (Midland, MI), are linear low-density polyethylene (LLDPE) containing octen comonomers.

[0067] VERSIFY® 3300 is a polypropylene elastomer manufactured by Dow® Inc. (Midland, MI).

[0068] PCR HDPE 94020 is a post-consumer recycled polyethylene with a lower gel level compared to post-consumer recycled resins made from stretched film. PCR HDPE 94020 is manufactured by Enka Company (Colombia). The gel level is analyzed according to GI200, and the value is 19-100. PCR is obtained from a mechanical recycling process, and HDPE is obtained as a by-product from the recycling process. PCR is washed, and then the PE is separated from other materials by density to obtain a complete PE stream. This stream is then washed again, dried, and fed into an extruder to produce the final PCR composition provided in Table 2 below.

[0069] [Table 2]

[0070] PCR#2 and PCR#3 are post-consumer recycled LLDPE resins made from recovered stretched film.

[0071] Films were extruded on a 5-layer Egan Davis Standard cast line using the film structures provided in Tables 3-4 and the process conditions in Table 4. All cast films were produced with a thickness of 20 μm.

[0072] [Table 3]

[0073] [Table 4]

[0074] [Table 5]

[0075] Three-layer cast films were extruded on the Egan Davis Standard cast line using the film structures provided in Table 6 and the process conditions in Table 7. All cast films were manufactured with a thickness of 20 μm.

[0076] [Table 6]

[0077] [Table 7]

[0078] [Table 8]

[0079] [Table 9]

[0080] Referring to Table 8, all 5-layer Examples 1-4 of the present invention demonstrated higher tear resistance compared to Comparative Example 1, which did not contain PCR resin. Furthermore, all 5-layer Examples 1-4 of the present invention demonstrated higher tear resistance compared to Comparative Example 2, which contained PCR LLDPE. Moreover, 5-layer Example 1 of the present invention demonstrated improved extreme stretching using a simulated 3-layer core with PCR in each layer.

[0081] Example 4 of the present invention, a five-layer solution, showed improved tear resistance compared to a simulated three-layer film such as Example 1 of the present invention by including a PCR-free intermediate layer between the core layer and the adhesive / release layer. Furthermore, Example 4 of the present invention had better processing parameters such as lower pressure compared to Comparative Example 2 and process stability compared to Comparative Example 3, which was not stable enough to operate the cast extrusion line. These examples demonstrate that PCR can be used to produce more sustainable, high-quality stretched films with improved tear resistance and minimized reductions in extreme stretching and puncture.

[0082] Referring to Table 9, Examples 5 and 6 of the present invention, which are three-layer films, offer sustainability while still maintaining excellent ESTL ultimate stretch. Although the ESTL ultimate stretch may decrease slightly, this decrease still adequately meets the specifications of stretched wraps, which tend to require an ESTL ultimate stretch of 250-300%.

[0083] While specific embodiments of this disclosure have been illustrated and described, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of this disclosure. Accordingly, the appended claims are intended to cover all such changes and modifications that fall within the scope of this disclosure.

Claims

1. A multilayer film comprising a first outer layer, a second outer layer, and at least one core layer located between the first outer layer and the second outer layer, The at least one core layer has a density of 0.930–0.950 g / cc as determined according to ASTM D792, and a melt index (I) of 1.0–3.0 dg / min as determined according to ASTM D1238 (2.16 kg, 190°C). ２ ), and post-consumer recycled (PCR) polyethylene resin having a molecular weight distribution of 5 to 12 (MWD = Mw / Mn), The first outer layer and the second outer layer are multilayer films comprising an ethylene-based polymer, a propylene-based polymer, or a combination thereof.

2. The at least one core layer has a density of 0.900 g / cc to 0.968 g / cc and a melt index (I) of 0.2 to 5 dg / min. ２ The multilayer film according to claim 1, further comprising a virgin ethylene-based polymer having ).

3. The multilayer film according to claim 1 or 2, wherein the at least one core layer comprises a plurality of core layers, and one or more of the plurality of core layers comprises the PCR polyethylene resin.

4. The multilayer film according to any one of claims 1 to 3, wherein the ethylene-based polymer of the first outer layer and / or the second outer layer comprises linear low-density polyethylene (LLDPE).

5. The multilayer film according to any one of claims 1 to 4, wherein the propylene polymer of the first outer layer and / or the second outer layer comprises a polypropylene plastomer.

6. The multilayer film according to any one of claims 1 to 5, wherein the at least one core layer comprises 5 to 100% by weight of the PCR polyethylene resin.

7. The multilayer film according to any one of claims 1 to 6, wherein the multilayer film comprises 5 to 50% by weight of the PCR polyethylene resin, preferably 10 to 40% by weight of the PCR polyethylene resin, and more preferably 20 to 40% by weight of the PCR polyethylene resin.

8. The multilayer film according to any one of claims 1 to 7, wherein the PCR polyethylene resin comprises a gel level (G1200) of 15 to 125.

9. The multilayer film according to any one of claims 1 to 8, wherein the multilayer film has an ESTL tear resistance of more than 7 seconds, an ESTL puncture of more than 5.5 pounds, and an ESTL extreme stretch of more than 200%.

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

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