Multilayer films, tapes, and methods of making multilayer films

Abstract

The present disclosure provides a multilayer film including a core layer including a first polypropylene having an ash content of 0.2 to 5.0 weight percent, based on the total weight of the first polypropylene, a first skin layer including a second polypropylene, and a second skin layer including a third polypropylene. The core layer is disposed between the first skin layer and the second skin layer. The first polypropylene displays a crystallization peak higher than the second polypropylene in a differential scanning calorimetry thermogram. Methods of making a multilayer film and tapes including a multilayer film are also provided.

Description

PA103206W002MULTILAYER FILMS, TAPES, AND METHODS OF MAKING MULTILAYER FILMSBACKGROUND

[0001] Sustainability has been a growing megatrend in the global economy. Consumers are increasingly discerning and sensitive to the environmental impact based on their purchasing choices. As a result, there has been a growing demand for sustainable products in the market. One such class of products that would benefit from incorporating recycled materials is multilayer films.

[0002] Polypropylene has been a key homopolymer in various thermoplastic industrial applications due to its simplicity and good performance characteristics. Over time, homopolymers of polypropylene have also been used in its various isomeric forms such as isotactic, syndiotactic and atactic polypropylene, with all three types presenting different properties due to their arrangement of pendant groups within the polymer chain. In addition, the various homopolymers of polypropylene can be blended with other polymer types to tune performance properties.SUMMARY

[0003] In a first aspect, a multilayer film is provided. The multilayer film comprises a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 weight percent, based on the total weight of the first polypropylene; a first skin layer comprising a second polypropylene; and a second skin layer comprising a third polypropylene. The core layer is disposed between the first skin layer and the second skin layer. The first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

[0004] In a second aspect, a tape is provided. The tape comprises a multilayer film according to any embodiment of the first aspect and an adhesive disposed on at least a portion of the first skin layer opposite the core layer.

[0005] In a third aspect, a method of making a multilayer film is provided. The method comprises coextruding a first skin composition, a core composition, and a second skin composition, thereby forming a three-layer multilayer film. The multilayer film comprises a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 wt.%, based on the total weight of the first polypropylene; a first skin layer comprising a second polypropylene; and a second skin layer comprising a third polypropylene. The core layer is disposed between the first skin layer and the second skin layer, and wherein the first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

[0006] Various aspects and advantages of exemplary embodiments of the disclosure have been summarized. The above Summary is not intended to describe each illustrated embodiment or every implementation of the present certain exemplary embodiments of the present disclosure. The Drawingsand the Detailed Description that follow more particularly exemplify certain preferred embodiments using the principles disclosed herein.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 figures, in which:

[0008] FIG. 1 is a generalized schematic cross-sectional view of an exemplary multilayer film, according to various exemplary embodiments disclosed herein;

[0009] FIG. 2 is a scanning electron microscopy (SEM) image of a cross-section of a portion of an exemplary multilayer film;

[0010] FIG. 3 A is a differential scanning calorimetry thermogram of a comparative film;

[0011] FIG. 3B is a differential scanning calorimetry thermogram of an exemplary multilayer film; and

[0012] FIG. 4 is a generalized schematic cross-sectional view of an exemplary tape, according to various exemplary embodiments disclosed herein.

[0013] In the drawings, like reference numerals indicate like elements. While the above-identified drawings, which may not be drawn to scale, set forth various embodiments of the present disclosure, other embodiments are also contemplated, as noted in the Detailed Description. In all cases, this disclosure describes the presently disclosed disclosure by way of representation of exemplary embodiments and not by express limitations. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of this disclosure.DETAILED DESCRIPTION

[0014] For the following Glossary of defined terms, these definitions shall be applied for the entire application, unless a different definition is provided in the claims or elsewhere in the specification.Glossary

[0015] Certain terms are used throughout the description and the claims that, while for the most part are well known, may require some explanation. It should be understood that:

[0016] The term “adhesive” refers to pressure-sensitive adhesives and / or hot melt adhesives.

[0017] As used herein, “adjacent” encompasses both in direct contact (e.g., directly adjacent) and having one or more intermediate layers present between the adjacent materials.

[0018] The term “film” or “layer” refers to a single stratum within a multilayer film.

[0019] The term “substrate” encompasses films, layers, and articles.

[0020] As used herein, “thickness” refers to the smallest dimension of a film or layer, e.g., in a z-axis while a major surface of the film or layer is in the x- and y-axes. Thickness may be determined using a micrometer gauge or doing a microscopic analysis of a cross-sectional sample of a layer, a multilayer film, or an article.

[0021] The term “ethylene segment mixture” means a mixture of ethylene units that are in multiple bonding patterns, i.e. ethylene-co-propylene, propylene-co-ethylene, propylene-butylene, ethylene-co- butylene, polypropylene-co-hexene, ethylene-co-hexene, polyethylene.

[0022] The term “isotactic” refers to all the side groups of a polymer chain positioned on the same side of the polymer backbone.

[0023] The term “pentad” refers to five adjacent structural units in a polymer molecule. Tacticity can be defined by the measurement and quantification of the abundance of different pentad configurations in a polymer chain.

[0024] The term “polymer” means a material that contains repeating chemical units, regularly or irregularly arranged, “polymeric” and “plastic” each mean a material that mainly includes one or more polymers and may contain other components.

[0025] The term “polyethylene” refers to ethylene homopolymers, i.e., polyethylene, or those polyolefins composed primarily of ethylene.

[0026] The term “polypropylene” refers to propylene homopolymers, i.e., polypropylene, or those polyolefins composed primarily of propylene.

[0027] The term “copolymers” refers to polymers that contain two or more different monomer types that can be mixed and copolymerized. This can include block copolymers or random copolymers. In block copolymers, this can include sequential ethylene units (a polyethylene block) alternating with sequential propylene units (a polypropylene block). In random copolymers, the ethylene and propylene repeat units are distributed randomly in the polymer chain. Examples of other comonomers that can be incorporated include ethylene, 1 -octene, 1 -hexene, or other monomers. Copolymer can also include branched polyethylene sections like poly-l-butene and poly-l-hexene. A structure including an overall composition of ethylene of 25 weight percent, means that 25% of the weight of the structure is of made of ethylene segments.

[0028] The term “Melt Flow Index” (MFI) is a measure of the ease of flow of the melt of a thermoplastic polymer. It is defined as the mass of polymer, in grams, flowing in ten minutes through a capillary of a specific diameter and length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures. The MFI is an indicator of the polymer’s melt viscosity, thus a higher MFI indicates a lower viscosity.

[0029] The term “virgin” refers to polymer resin that has been produced directly from raw materials such as petroleum or natural gas. These polymer resins have not been used, processed or extruded to form end products.

[0001] The term “recycled” refers to polymer resin that has been diverted from a waste stream during a manufacturing process or after consumer use. The polymer resin has gone through at least one process, such as extrusion into a finished product. In some cases, the polymer product is then taken to be ground down into smaller pieces or flakes and used as resin for a second processing process to make a new product. Some such recycled polymers are called regrind. In some cases, a polymer film goes through a grinder or shredder to make flakes, which are then pelletized and used as resin for a new product. Thistype of recycling can be called repelletization. Recycled polymer as a whole can also refer to a blend of different recycled polymers. Thus, the process of recycling can alter the material composition to something different than virgin polypropylene.

[0030] The term “post-industrial recycled material” refers to a polymer that has been recovered from an industrial waste stream, e.g., material left over from making a product.

[0031] The term “post-consumer recycled material” refers to a polymer that has been recovered from a waste stream after being used by a consumer for the original product’s intended application (e.g., a plastic container).

[0032] The term “stereo defects” refers to defects, irregularities or deviations from the ideal stereochemistry in a polymer chain. For example, stereo defects in an isotactic polypropylene polymer chain will result in introduction of atactic and syndiotactic characteristics as the methyl groups are not in a regular arrangement. Additional processing of the polymer, such as recycling, can induce rearrangements of the methyl-groups within polypropylene and change the overall percent of stereo defects.

[0033] The term “thermoplastic” refers to a polymer that becomes plastic on heating and hardens on cooling. This process can be repeated multiple times, provided the heating temperature does not exceed the degradation temperature of the polymer.

[0034] The term “(meth)acryl” or “(meth)acrylate” with respect to a monomer, oligomer, (co)polymer or compound means a vinyl-functional alkyl ester formed as the reaction product of an alcohol with an acrylic or a methacrylic acid.

[0035] The term “optically clear” refers to an article in which there is no visibly noticeable distortion, haze or flaws as detected by the naked eye at a distance of about 1 meter, preferably about 0.5 meters.

[0036] By using terms of orientation such as “atop”, “on”, “over,” “covering”, “uppermost”, “underlying” and the like for the location of various elements in the disclosed coated articles, it is referring to the relative position of an element with respect to a horizontally -disposed, upwardly -facing substrate. However, unless otherwise indicated, it is not intended that the substrate or articles should have any particular orientation in space during or after manufacture, or in interpreting the claims.

[0037] As used herein, “radiation” refers to electromagnetic radiation unless otherwise specified.

[0038] As used herein, “transparent” refers to a material (e.g., film or layer) that absorbs less than 20% of light having wavelengths between 350 nm and 2500 nm.

[0039] The term “at least one” includes all integers of one and greater (e.g., at least 2, at least 4, at least 6, at least 8, at least 10, at least 25, at least 50, at least 100, etc.).

[0040] The terms “about” or “approximately” with reference to a numerical value or a shape means + / - five percent of the numerical value or property or characteristic, but expressly includes the exact numerical value.

[0041] The term “substantially” with reference to a property or characteristic means that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited. For example, a substrate that is “substantially” transparent refers to a substrate that transmitsmore radiation (e.g., visible light) than it fails to transmit (e.g., absorbs and reflects). Thus, a substrate that transmits more than 50% of the visible light incident upon its surface is substantially transparent, but a substrate that transmits 50% or less of the visible light incident upon its surface is not substantially transparent.

[0042] As used in this specification and the appended embodiments, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. Thus, for example, reference “a compound” includes a mixture of two or more compounds. As used in this specification and the appended embodiments, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

[0043] Unless otherwise indicated, all numbers expressing quantities or ingredients, measurement of properties and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached listing of embodiments can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0044] By definition, the total weight percentages of all ingredients in a composition equals 100 weight percent.

[0045] Various exemplary embodiments of the disclosure will now be described. Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the present disclosure. Accordingly, it is to be understood that the embodiments of the present disclosure are not to be limited to the following described exemplary embodiments but is to be controlled by the limitations set forth in the claims and any equivalents thereof.Multilayer Films

[0046] In a first aspect, a multilayer film is provided. The multilayer film comprises:

[0047] a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 weight percent (wt.%), based on the total weight of the first polypropylene;

[0048] a first skin layer comprising a second polypropylene; and

[0049] a second skin layer comprising a third polypropylene,

[0050] wherein the core layer is disposed between the first skin layer and the second skin layer, and wherein the first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

[0051] Referring to FIG. 1, a generalized schematic cross-sectional view of an exemplary multilayer film 100 is provided. The multilayer film 100 includes a core layer 110 comprising a first polypropylene having an ash content of 0.2 to 5.0 wt.%; a first skin layer 120 comprising a second polypropylene; and asecond skin layer 130 comprising a third polypropylene. The core layer 110 is located inbetween the first skin layer 120 and the second skin layer 130.

[0052] As depicted in FIG. 1, in some embodiments the core layer 110 has a greater thickness than either of the first skin layer 120 or the second skin layer 130. In such embodiments, considering the multilayer film being composed of a combination of the core layer, first skin layer, and second skin layer that total 100 wt.%, the multilayer film may contain 60 wt.% or greater of the core layer, such as 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, or 85 wt.% or greater of the core layer; and 95 wt.% or less of the core layer, such as 90 wt.%, 85 wt.%, 80 wt.%, 75 wt.%, or 70 wt.% or less of the core layer. Concomitantly, such multilayer films may contain 5 wt.% or greater of a combination of the first skin layer and the second skin layer, such as 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.%, or 35 wt.% or greater of a combination of the first skin layer and the second skin layer; and 40 wt.% or less, 35 wt.%, 30 wt.%, 25 wt.%, 20 wt.%, 15 wt.%, or 10 wt.% or less of a combination of the first skin layer and the second skin layer. In certain embodiments a multilayer film may contain 60-95 wt.% of the core layer and 5-40 wt.% of a combination of the first skin layer and the second skin layer, in which a combination of the core layer, first skin layer, and second skin layer total 100 wt.%. In other embodiments, the core layer 110 may have an equal or lesser thickness than the first skin layer 120 and / or the second skin layer 130.

[0053] Often, polypropylene films are subjected to orientation. In certain embodiments, the multilayer film is monoaxially oriented and in other embodiments the multilayer film is biaxially oriented. Orientation is described in greater detail with respect to the third aspect (i.e., methods) below.

[0054] In some embodiments, a multilayer film according to the present disclosure comprises at least one void within the core layer. Referring to FIG. 2, a scanning electron microscopy (SEM) image of a cross-section of a portion of an exemplary multilayer film 200 is provided. The SEM was taken using a magnification of 500X. The portion of the multilayer film 200 includes a core layer 210 comprising a first polypropylene having an ash content of 0.2 to 5.0 wt.%; a first skin layer 220 comprising a second polypropylene; and a second skin layer 230 comprising a third polypropylene. The portion of the multilayer film 200 shown in FIG. 2 had a thickness of 2.3 mils (58.4 micrometers). The core layer 210 is located in between the first skin layer 120 and the second skin layer 230. Numerous voids are visible within the core layer 210; just a few voids 202, 204, and 206 are identified in the core layer 210. Without wishing to be bound by theory, it is believed that the presence of particles and / or defects due to the high ash content of the first polypropylene can result in the formation of at least one void (e.g., gap or cavity) in the core layer of multilayer films of some embodiments of the present application.

[0055] In some cases, one or more voids are located at a depth from an exterior surface of the first skin layer or the second skin layer that are greater than 5% of a full thickness of the multilayer film, such as 7%, 10%, 12%, 15%, 17%, or greater than 20% of a full thickness of the multilayer film. Referring again to FIG. 2, this concept is represented with a bracket indicating a full thickness, TF, of the multilayer film 200 and a bracket indicating 5%, T5%, of the full thickness TF, from an exterior surface 232 of the second film layer. It is noted that in this particular multilayer film 200 the skin layers 220, 230 each contribute over 5% of the full thickness, so for a void to be present in the core layer 210, the void will necessary belocated at a depth from an exterior surface 222 of the first skin layer 200 or from an exterior surface 232 of the second skin layer 230 that is greater than 5%. Each of labeled voids 202, 204, and 206 are located further into the depth of the multilayer film than 5% of the full thickness TF. Often, the multilayer film has a density of greater than 0.72 grams per cubic centimeter (g / cc), such as 0.75 g / cc, 0.77 g / cc, 0.80 g / cc, 0.82 g / cc, or greater than 0.85 g / cc. This is an indication that the multilayer film is primarily a solid polymeric article despite the potential presence of at least one void, which is in contrast to a porous multilayer film having a substantial amount of cavities, such as having a form of a foam, a porous membrane, etc.

[0056] Referring to FIGS. 3A and 3B, differential scanning calorimetry thermograms are provided of an exemplary multilayer film (FIG. 3B) and a comparative film (FIG. 3A). The exemplary multilayer film, FE-01, displays two crystallization peaks in a differential thermogram, which were deconvoluted into a sum of Gaussians with a background function, as described in detail in the Examples below. This is due to the presence of a first polypropylene in the core layer that is different than each of the second polypropylene in the first skin layer and the third polypropylene in the second skin layer. In FE-01, the second polypropylene and the third polypropylene were the same. In FIG. 3B, the first crystallization peak (Gaussian - 1) is at 113 degrees Celsius and is for the second and third polypropylene polymers, while the second crystallization peak (Gaussian - 2) is at 123 degrees Celsius and is for the first polypropylene of the core layer. As such, the first polypropylene displaying a crystallization peak higher than the second polypropylene refers to a comparison of the peak crystallization temperatures of the first and second polypropylenes, with the peak crystallization temperature of the first polypropylene being higher than the peak crystallization temperature of the second polypropylene. In contrast to FE-01, FIG. 3 A shows a single crystallization peak (Gaussian - 2) for Comparative Example Film 1 (FC-01). The Gaussian -1 is not contributing the overall crystallization peak and the overall crystallization peak can be well described with a single Gaussian (Gaussian-2).

[0057] In some embodiments, each of the first skin layer, the second skin layer, and the core layer exhibits a melting point of between 155 and 170 degrees Celsius, using differential scanning calorimetry and determined according to ASTM D3418-21, at a cooling rate of 10 degrees Celsius per minute. As polypropylene has a melting point in the vicinity of 160 degrees Celsius, this demonstrates that the polypropylene content of the multilayer film is significant, as opposed to polypropylene being a minor component of the overall multilayer film among other polymeric materials.

[0058] It was unexpectedly discovered that it was possible to form a multilayer film having a core layer containing a first polypropylene having an ash content above 0.2 wt.% that exhibits a haze of no more than 90%, such as a haze of no more than 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, or no more than 45%. The haze may be determined by a Haze-gard transparency and haze meter, as described in the Examples below. Such levels of haze still allow the multilayer film to be used for applications that may require some minimum level of transparency, such as shipping tape. Thickness of a multilayer film can affect optical properties such as haze. As such, the recited haze values apply to multilayer films having a thickness in a range of from 0.5 mils (12.7 micrometers) to 3 mils (76.2 micrometers).

[0059] Similar to exhibiting a certain haze that allows some transparency of the multilayer film, it has been discovered that it was possible to form a multilayer film of thickness less than 2 mils (less than 50.8 micrometers) having a core layer containing a first polypropylene having an ash content above 0.2 wt.% that exhibits a barcode decodability score within 0.6 of the barcode when uncovered, determined according to ISO Method 15416-1. Similarly, the same film having a thickness in a range of 2 mils (50.8 micrometers) to 3 mils (76.2 micrometers) can exhibit a barcode decodability score within 1.0 of the barcode when uncovered, determined according to ISO Method 15416-1. The complete barcode decodability method is described in the Examples below. It is to be understood that the decodability of a barcode itself when measured according to ISO Method 15416-1 may vary due to characteristics of the barcode such as sharpness of the barcode lines, color of the barcode lines, etc. Advantageously, when a multilayer film according to at least certain embodiments of the present disclosure is placed over a particular barcode, preferably the decrease in barcode decodability is 1.0 or less, such as 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3. or 0.2 or less, despite the presence of ash in the core layer.

[0060] In certain embodiments, the multilayer film is formed of at least 15 wt.% of post-industrial recycled material, based on the total weight of the multilayer film, such as 15 wt.% or greater, 20 wt.%, 25 wt.%, 30 wt.%, 35 wt.%, or even 40 wt.% or greater post-industrial recycled material, based on the total weight of the multilayer film. In certain embodiments, the multilayer film is formed of at least 30 wt.% of post-consumer recycled material, based on the total weight of the multilayer film, such as 30 wt.% or greater, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, or even 90 wt.% or greater post-consumer recycled material, based on the total weight of the multilayer film.Polypropylene

[0061] Because propylene is a chiral monomer, it can result in various stereo chemistries and isomers when polymerized. Moreover, as a result of reprocessing, the changes in tacticity values and pentad configurations can occur. Polypropylene can thus be atactic - where the side groups or substituents on the polymer chain are randomly distributed along the polymer chain, isotactic - where the side groups or substituents on the polymer chain are all on the same side along the polymer chain, or syndiotactic - where the side groups or substituents on the polymer chain alternate regularly on either side of the polymer backbone. In the case of polypropylene, the side chains or substituents would be the methyl group. In certain embodiments, a polypropylene component of a core layer and / or a skin layer is isotactic in an amount of at least 70 wt.%, at least 75 wt.%, at least 80 wt.%, or at least 85 wt.%, based on the total weight of the layer. In certain embodiments, a polypropylene component of a core layer and / or a skin layer is used in an amount of up to 90 wt.%, up to 91 wt.%, up to 92 wt.%, up to 93 wt.%, up to 94 wt.%, or up to 95 wt.%, based on the total weight of the layer.

[0062] Tacticity can be quantified through the measurement of stereo defects in a pentad of repeat units. For example, in isotactic polypropylene, a pentad (5 repeat units) would have the same stereochemistrydue to its regularity. Deviations from perfect isotacticity can occur, and in the extreme, this regularity is so disrupted that the material cannot crystallize and is categorized as atactic polypropylene.

[0063] The deviation of tacticity and deviation from perfect isotacticity can be detected through Nuclear Magnetic Resonance (NMR), through the quantification of stereo defects that deviate from ideal isotacticity. NMR can differentiate between meso diads, which are abbreviated as “m”, from racemeic diads, which are abbreviated as “r”. Drawing reference back to the discussion on tacticity, syndiotactic polypropylene would thus consist of all racemic diads. NMR can also determine the types of defects and distinguish between the degree of defects. For example, a single-site defect is where a dyad within a pentad is racemic. A two-site defect is where two diads within a pentad are racemic. NMR is able to identify single-site defects such as mmmr, mrmm, rmrr, or mrrr configurations. Typically, the higher the deviation from isotacticity, the higher the stereo defect percentage. Typically, recycled polymer resins would have a higher percentage of stereo defects when compared to virgin polymer resins, due to their additional processing history. Thus, NMR can be used to identify the presence of recycled polymer in a polymer composition or polymer blend.

[0064] In some embodiments, the pentad component of a core layer and / or a skin layer has at least 1%, at least 2%, at least 4%, or at least 8% stereo defects as measured by NMR. In one preferred embodiment, the pentad component of a core and / or skin layer has greater than 4% stereo defects as measured by NMR.

[0065] In one preferred embodiment, the stereo defects are of the single-site type. In certain embodiments, the pentad component of a core and / or skin layer has at least 1%, at least 2%, at least 4%, or at least 8% single-site stereo defects as measured by NMR. In one preferred embodiment, the pentad component has greater than 4% single-site stereo defects as measured by NMR.

[0066] Virgin polypropylene refers to polypropylene that has been produced directly from raw materials (e.g., natural gas, petroleum, agriculture feedstocks). These polymer resins have not been used, processed or extruded to form end products. Recycled resin, on the other hand, refers to polymer resin that has gone through at least one processing step, as noted above.

[0067] There are different types of recycled polymer. For instance, “post-industrial recycled material” refers to a polymer that has been recovered from an industrial waste stream, e.g., material left over from making a product. In contrast, “post-consumer recycled material” refers to a polymer that has been recovered from a waste stream after used by a consumer for the original product’s intended application. Post-consumer recycled material often contains impurities (e.g., other types of polymers, debris, etc.) due to having been used in a consumer product and having been recycled. In some cases, post-consumer recycled material is obtained from curbside recycling. In some cases, the post-consumer recycling material is designated as “ocean bound”, which is generally considered to be waste collected from an area of mismanaged waste that is within 50 kilometers of a coastline.

[0068] Examples of useful recycled post-industrial polypropylene include material produced by Deltco Plastics (Ashland, WI). Alternatively, useful recycled post-industrial polypropylene could be made internally from polypropylene film scraps that have been diverted from a waste stream. An example ofpost-consumer polypropylene includes material produced by KW Plastics (Troy, AL). Examples of virgin polypropylene include material such as Braskem FF030 from Braskem America (Philadelphia, PA), ExxonMobil 4712 from Exxon Mobil Corporation (Spring, TX), and 3371, from TotalEnergies (La Porte, TX).

[0069] In addition to the option of employing a polymer blend of virgin and recycled polypropylene, in certain embodiments one or more of the core layer, the first skin layer, or the second skin layer includes an ethylene segment mixture in the polymer composition. The ethylene segments can either be incorporated into the layer(s) through a polymer blend of polypropylene and polyethylene or included through copolymers of polyethylene and polypropylene.Core Layer

[0070] In some embodiments, at least 30 wt.% of the core layer is the first polypropylene, based on a total weight of polymeric materials in the core layer, such as 30 wt.% or greater, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, or even 99 wt.% or greater of the core layer is the first polypropylene, based on a total weight of polymeric materials in the core layer. As such, in certain cases, the core layer is substantially all (i.e., the first) polypropylene whereas in other cases the core layer may contain additional polymers (including additional polypropylene polymers). In certain embodiments, the first polypropylene is a recycled polypropylene, such as a post-consumer recycled polypropylene.

[0071] The first polypropylene has an ash content of 0.2 wt.% or greater, based on the total weight of the first polypropylene, such as 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1.0 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.8 wt.%, 2.0 wt.%, 2.2 wt.%, 2.4 wt.%, 2.6 wt.%, 2.8 wt.%, 3.0 wt.%, 3.2 wt.%, 3.4 wt.%, 3.6 wt.%, 3.8 wt.%, or 4.0 wt.% or greater; and 5.0 wt.% or less, based on the total weight of the first polypropylene, 4.8 wt.%, 4.6 wt.%, 4.4 wt.%, 4.2 wt.%, 4.0 wt.%, 3.8 wt.%, 3.6 wt.%, 3.4 wt.%, 3.2 wt.%, 3.0 wt.%, 2.8 wt.%, 2.6 wt.%, 2.4 wt.%, 2.2 wt.%, 2.0 wt.%, 1.8 wt.%, 1.6 wt.%, 1.4 wt.%, 1.2 wt.%, or 1.0 wt.% or less, based on the total weight of the first polypropylene. The ash content can be determined by a thermogravimetric analysis (TGA) method or a bulk method, each of which is described in detail in the Examples below as “TGA- %Ash” and “Bulk - %Ash”, respectively. In select embodiments, the ash content is determined according to the Bulk - %Ash Method. Both methods give equivalent results (as demonstrated in the Examples below), although it is noted that a greater number of samples should be tested using the TGA method due to the small sample size and potential non-uniformities within samples of recycled resins.

[0072] In embodiments where the core layer includes polymeric material in addition to the first polypropylene, those polymeric materials may include homopolymers, copolymers, or polymer blends of thermoplastic polymers. Suitable thermoplastics include polyolefins and combinations of polyolefins due to their miscibility and compatibility during compounding and extrusion. Suitable polyolefins include, but are not limited to, poly(ethylene), poly(propylene), poly(l -butene), poly-l-hexene poly-4-methyl-l- butene, copolymers of ethylene and propylene, alpha olefin copolymers (such as copolymers of ethyleneor propylene with 1-butene, 1-hexene, 1-octene, 1-decene), poly(ethylene-co-l -butene), poly(4-methyl-l- penetne), poly(ethylene-co-l-butene-co- 1-hexene), or any combinations thereof.

[0073] The core layer optionally includes a polypropylene that has an ethylene segment mixture of 0.6 wt.% or greater as determined by Nuclear Magnetic Resonance (NMR), such as 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1.0 wt.%, 1.2 wt.%, 1.4 wt.%, 1.6 wt.%, 1.8 wt.%, 2.0 wt.%, 2.2 wt.%, 2.4 wt.%, 2.6 wt.%, 2.8 wt.%, 3.0 wt.%, 3.2 wt.%, 3.4 wt.%, 3.6 wt.%, 3.8 wt.%, 4.0 wt.%, 4.5 wt.%, 5.0 wt.%, 5.5 wt.%, 6.0 wt.%, 6.5 wt.%, 7.0 wt.%, 7.5 wt.%, 8.0 wt.%, 8.5 wt.%, or 9.0 wt.% or greater as determined by NMR; and 15.0 wt.% or less as determined by NMR, 14.5 wt.%, 14.0 wt.%, 13.5 wt.%, 13.0 wt.%, 12.5 wt.%, 12.0 wt.%, 11.5 wt.%, 11.0 wt.%, 10.5 wt.%, 10.0 wt.%, 9.5 wt.%, 9.0 wt.%, 8.5 wt.%, 8.0 wt.%, 7.5 wt.%, 7.0 wt.%, 6.5 wt.%, 6.0 wt.%, 5.5 wt.%, 5.0 wt.%, 4.8 wt.%, 4.6 wt.%, 4.4 wt.%, 4.2 wt.%, 4.0 wt.%, 3.8 wt.%, 3.6 wt.%, 3.4 wt.%, 3.2 wt.%, 3.0 wt.%, 2.8 wt.%, 2.6 wt.%, 2.4 wt.%, 2.2 wt.%, or 2.0 wt.% or less, as determined by NMR. Stated another way, in certain embodiments, the first polypropylene has an ethylene segment mixture of between 0.6 to 15 wt.% as determined by NMR. The ethylene segment mixture may be high due to the presence of impurities such as other polymers provided by recycled materials (in some cases post-consumer recycled materials).

[0074] The core layer may be made from polypropylenes having a melt flow index that is within a relatively large range, based on the various materials that may be present in the layer having a high ash content (e.g., recycled polypropylene). In some cases, the core layer exhibits a melt flow index of 2 grams (g) or greater per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms, such as 3 g, 4 g, 5 g, 6 g, 7 g, 8 g, 9 g, 10 g, 11 g, 12 g, 13 g, 14 g, or 15 g or greater per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms; and 20 g or less per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms, 19 g, 18 g, 17 g, 16 g, 15 g, 14 g, 13 g, 12 g, 11 g, or 10 g or less per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms. Stated a different way, in certain embodiments, the core layer exhibits a melt flow index between 2 and 20 grams per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms. It is to be understood that the melt flow index increases (and viscosity decreases) during extrusion. A complete description of a method to measure melt flow index is provided in the Examples below.

[0075] As noted above, in some cases, a polypropylene component of a core layer is isotactic in an amount of at least 70 wt.%, 75 wt.%, 80 wt.%, or at least 85 wt.%; and up to 90 wt.%, 91 wt.%, 92 wt.%, 93 wt.%, 94 wt.%, or up to 95 wt.%, based on the total weight of the layer based on the total weight of the layer. In select embodiments, the core layer contains a pentad component of first polypropylene segments that is isotactic of 85% to 91%, as measured by NMR.

[0076] It has been discovered that certain recycled polymers, such as post-consumer recycled polypropylene, may not be sufficiently oxidatively stable to undergo extrusion processes without undergoing large changes in MFI. Accordingly, in some cases, the core layer further includes at least one antioxidant. For instance, the antioxidant may be compounded with a polypropylene resin prior to extrusion. The antioxidant is sometimes provided as an antioxidant blend containing two or more different antioxidants. Advantageously, a core layer containing at least one antioxidant exhibits anoxidation induction time in air at 200 degrees Celsius of at least 100 minutes, as determined by differential scanning calorimetry, such as at least 105 minutes, 110 minutes, 115 minutes, or at least 120 minutes. A complete description of a method to measure oxidation induction time (in air) is provided in the Examples below. Examples of suitable antioxidants include for instance and without limitation, hindered phenolics like “IRGANOX 1010” from BASF USA (Florham Park, NJ), phosphite esters like “IRGAFOS 126” from BASF Corporation (Ludwigshafen, Germany), synergistic blends like “IRGANOX B215” from BASF USA, “CYCLOAID UPR001” (from Adeka Company (Tokyo, Japan), or metal deactivators like “IRGANOX MD-1024” from BASF USA.First Skin Layer and Second Skin Layer

[0077] It is to be understood that the first skin layer and the second skin layer may be either the same or different. Similarly, it is to be understood that the second polypropylene (of the first skin layer) and the third polypropylene (of the second skin layer) may be either the same or different. In some cases, the second polypropylene and the third polypropylene are identical.

[0078] In some embodiments, at least 30 wt.% of the first skin layer is the second polypropylene, based on a total weight of polymeric materials in the first skin layer, such as 30 wt.% or greater, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, or even 99 wt.% or greater of the first skin layer is the second polypropylene, based on a total weight of polymeric materials in the first skin layer. As such, in certain cases, the first skin layer is substantially all (i.e., the second) polypropylene whereas in other cases the first skin layer may contain additional polymers (including additional polypropylene polymers). In certain embodiments, the second polypropylene is a recycled polypropylene, such as a post-industrial recycled polypropylene.

[0079] In some embodiments, at least 30 wt.% of the second skin layer is the third polypropylene, based on a total weight of polymeric materials in the second skin layer, such as 30 wt.% or greater, 35 wt.%, 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.%, 96 wt.%, 97 wt.%, 98 wt.%, or even 99 wt.% or greater of the second skin layer is the third polypropylene, based on a total weight of polymeric materials in the second skin layer. As such, in certain cases, the second skin layer is substantially all (i.e., the third) polypropylene whereas in other cases the second skin layer may contain additional polymers (including additional polypropylene polymers). In certain embodiments, the third polypropylene is a recycled polypropylene, such as a postindustrial recycled polypropylene.

[0080] Similar to the core layer, in embodiments where the first skin layer and / or the second skin layer includes polymeric material in addition to the second polypropylene and / or third polypropylene, respectively, those polymeric materials may include the polyolefins mentioned above with respect to the core layer.

[0081] At least one of the first skin layer or the second skin layer optionally has a polypropylene (e.g., the second polypropylene and / or the third polypropylene, respectively) that has an ethylene segmentmixture of 0 wt.% (e.g., no measurable amount) or greater as determined by NMR, such as 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, 0.6 wt.%, 0.7 wt.%, 0.8 wt.%, 0.9 wt.%, 1.0 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.7 wt.%, 1.8 wt.%, 1.9 wt.%, or 2.0 wt.% or greater as determined by NMR; and 3.0 wt.% or less as determined by NMR, 2.8 wt.%, 2.9 wt.%, 2.8 wt.%, 2.7 wt.%, 2.6 wt.%, 2.5 wt.%, 2.4 wt.%, 2.3 wt.%, 2.2 wt.%, 2.1 wt.%, 2.0 wt.%, 1.9 wt.%, 1.8 wt.%, 1.7 wt.%, 1.6 wt.%, 1.5 wt.%, 1.4 wt.%, 1.3 wt.%, 1.2 wt.%, 1.1 wt.%, or 1.0 wt.% or less, as determined byNMR. Stated another way, in certain embodiments, at least one of the first skin layer or the second skin layer has a polypropylene having an ethylene segment mixture of between 0 to 3 wt.%, as determined by NMR. In select embodiments, each of the first skin layer and the second skin layer has a polypropylene having an ethylene segment mixture between 0 to 3 wt.%, as determined by NMR. Such an ethylene segment mixture content may be due to the presence of a post-industrial recycled polypropylene.

[0082] In some embodiments, at least one of the first skin layer or the second skin layer exhibits a melt flow index of 2 grams (g) or greater per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms (kg), such as 3 g, 4 g, 5 g, 6 g, 7 g, or 8 g or greater per 10 minutes at 230 degrees Celsius under a weight of 2.16 kg; and 10 g or less per 10 minutes at 230 degrees Celsius under a weight of 2.16 kg, 9 g, 8 g, 7 g, 6 g, 5 g, or 4 g or less per 10 minutes at 230 degrees Celsius under a weight of 2.16 kg. Stated a different way, in certain embodiments, at least one of the first skin layer or the second skin layer exhibits a melt flow index of between 2 grams and 10 grams or greater per 10 minutes at 230 degrees Celsius under a weight of 2.16 kg. In select embodiments, each of the first skin layer and the second skin layer exhibits a melt flow index of between 2 grams and 10 grams or greater per 10 minutes at 230 degrees Celsius under a weight of 2.16 kg.

[0083] As noted above, in some cases, a polypropylene component of a skin layer is isotactic in an amount of at least 70 wt.%, 75 wt.%, 80 wt.%, or at least 85 wt.%; and up to 90 wt.%, 91 wt.%, 92 wt.%, 93 wt.%, 94 wt.%, or up to 95 wt.%, based on the total weight of the layer. In select embodiments, at least one of the first skin layer or the second skin layer contains a pentad component of second polypropylene segments and third polypropylene segments, respectively, that is isotactic of between 85% to 92% as measured by NMR. In some preferred embodiments, each of the first skin layer and the second skin layer contains a pentad component of second polypropylene segments and third polypropylene segments, respectively, that is isotactic of between 85% to 92% as measured by NMR.Additives

[0084] In some embodiments, there is at least one additive present in at least one of the core layer, the first skin layer, or the second skin layer. At least one additive may be present in at least two of the three layers, or in each of the three layers.

[0085] Suitable additives include for instance and without limitation, charge enhancing additives, colorants (e.g., pigments or dyes), antioxidants, UV stabilizers, oil or waxes to aid in extrusion, plasticizers, tackifiers, flow control agents, cure promoters, expanded microspheres, thermally conductive particles, electrically conductive particles, silica, glass, talc, optical brighteners, mold release agents,peroxides, activated carbon, alumina, phosphite esters, thioethers, metal deactivators, rheology modifiers, flame retardants, pro-degradants, fillers, nucleators and combinations thereof. One or more additives may be included in an amount suitable for their purposes, such as up to 50 parts per hundred parts resin (phr).

[0086] The performance-enhancing additive can be blended with the resin(s) for a layer as solids before extrusion, or the components can also be melted and extruded separately and subsequently blended together as liquids. Alternatively, the additives and a portion of the resin(s) can be mixed as solids and melted to form a relatively additive-rich mixture that is subsequently combined with the non-additive containing resin(s). This latter method is also sometimes called master batching.Tapes

[0087] In a second aspect, a tape is provided. The tape comprises a multilayer film according to any embodiment of the first aspect and an adhesive disposed on at least a portion of the first skin layer opposite the core layer.

[0088] Referring to FIG. 4, a generalized schematic cross-sectional view of an exemplary tape 400 is provided. The tape 400 includes a multilayer film 401 including a core layer 410 comprising a first polypropylene having an ash content of 0.2 to 5.0 wt.%; a first skin layer 420 comprising a second polypropylene; and a second skin layer 430 comprising a third polypropylene. The core layer 410 is located in between the first skin layer 420 and the second skin layer 430. The tape 400 additionally includes an adhesive 440 disposed on at least a portion of the first skin layer 420 (e.g., on a first major surface 422 of the first skin layer 420) of the multilayer film 401 opposite the core layer 410. In the embodiment depicted in FIG. 4, the tape further includes an optional low adhesion backsize 450 disposed on at least a portion of the second skin layer 430 (e.g., on a first major surface 432 of the second skin layer 430) opposite the core layer 410.

[0089] In some preferred embodiments, the adhesive is a pressure-sensitive adhesive. Classes of suitable pressure sensitive adhesives include acrylics, tackified rubber, tackified synthetic rubber, ethylene vinyl acetate and the like. Suitable acrylic adhesives are disclosed, for example, in U.S. Pat. Nos. 3,239,478 (Harlan); 3,935,338 (Robertson); 5,169,727 (Boardman); 4,952,650 (Young et al.) and 4,181,752 (Martens et al.), incorporated herein by reference.

[0090] In select embodiments, the adhesive is optically clear, which means that the adhesive has both transparency and clarity (e.g., low haze). In certain embodiments, an optically clear adhesive (OCA) is selected from an acrylate, a polyurethane, a polyolefin (such as a styrene-isoprene block copolymer (SIS)), a silicone, or a combination thereof. Illustrative OCAs include those described in International Pub. No. WO 2008 / 128073 (Everaerts et al.) relating to antistatic optically clear pressure sensitive adhesives, U.S. Pat. App. Pub. Nos. US 2009 / 089137 (Sherman et al.) relating to stretch releasing OCA, US 2009 / 0087629 (Everaerts et al.) relating to indium tin oxide compatible OCA, US 2010 / 0028564 (Cheng et al.) relating to antistatic optical constructions having optically transmissive adhesive, US 2010 / 0040842 (Everaerts et al.) relating to adhesives compatible with corrosion sensitive layers, US 2011 / 0126968 (Dolezal et al.) relating to optically clear stretch release adhesive tape, and U.S. Pat. No.8,557,378 (Yamanaka et al.) relating to stretch release adhesive tapes. Suitable OCAs include acrylic optically clear pressure sensitive adhesives such as, for example, 3M OCA 8146, 8211, 8212, 8213, 8214, and 8215, each available from 3M Company, St. Paul, MN.

[0091] Exemplary thicknesses of a layer of a pressure-sensitive adhesive may be in the range from about 0.05 to about 100 micrometers.Methods

[0092] In a third aspect, a method of making a multilayer film is provided. The method comprises:

[0093] coextruding a first skin composition, a core composition, and a second skin composition, thereby forming a three-layer multilayer film comprising:

[0094] a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 wt.%, based on the total weight of the first polypropylene;

[0095] a first skin layer comprising a second polypropylene; and

[0096] a second skin layer comprising a third polypropylene,

[0097] wherein the core layer is disposed between the first skin layer and the second skin layer, and wherein the first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

[0098] Coextrusion processes generally involve compounding certain materials to ensure good mixing (by, for example, twin screw extrusion) and extruding (by, for example, single screw, twin screw, etc.) melted material through a feedblock and / or die. The feedblock and / or die typically contains three or more channels for material feedstock to flow and creates a multi-layer structure. The melted material is then quenched on a drum to make a coextruded multilayer film which can be subsequently processed for example by orientation.

[0099] Compounding and pelletizing is the first step, to prepare the individual compositions for the different layers. After compounding, the compositions may be coextruded through a die into a desired multilayer film construction in a single step. Coextrusion typically involves the simultaneous melt processing of multiple molten streams and the combination of such molten streams into a single unified structure or coextruded film.

[0100] The extrusion process involves processing the one or more feedstocks above their melt temperature through the die(s), resulting in extrusion of the coextruded film. A coextruded film is generally a composite of all the molten feedstocks placed within the coextrusion process. In some embodiments, at least some of the layers are in contact with one another in the molten state.

[0101] The coextruded multilayer film may further be processed, for example, by orientation (e.g., by stretching). Stretching can be carried out on a fdm web biaxially or monoaxially. Biaxial stretching means stretching in two different directions in the plane of the multilayer film. Typically, but not always, the first direction is the longitudinal direction “L”, and the second direction is the width direction “W”. Biaxial stretching can be performed sequentially by stretching multilayer film, for example, first in one of the first or second direction and subsequently in the other of the first or second direction. Biaxialstretching can also be performed essentially simultaneously in both directions. In a typical operation, the freshly extruded molten film is cast onto a chill roll to produce a quenched amorphous film, which is briefly heated and stretched in the down-web direction, and then conducted through a tenter frame where it is stretched transversely with moderate heating. Down-web direction stretching may be accomplished by passing between two sets of nip rolls, the second set rotating at a higher speed than the first.Monoaxial stretching refers to stretching in only one direction in the plane of the multilayer film. Typically, monoaxial stretching is performed in one of the “L” or “W” direction but other stretch directions are also possible.

[0102] In some cases, methods according to the present disclosure further include monoaxially orienting the multilayer film. When the multilayer film is monoaxially oriented, typically the multilayer film is oriented to a ratio of a final stretched area to an unoriented area of at least of 3 : 1 , such at least 5 : 1 , 8 : 1 , 10:1 or at least 12:1.

[0103] In some cases, methods according to the present disclosure further include biaxially orienting the multilayer film. When the multilayer film is biaxially oriented, typically the multilayer film is biaxially oriented to a ratio of a final stretched area to an unoriented area of at least 40:1, such as 41:1, 42 : 1 , 43:1, 44: 1, or at least 45:1. It was unexpectedly discovered that multilayer films according to at least certain embodiments of the present disclosure are capable of being significantly stretched (e.g., to a ratio of a final stretched area to an unoriented area of at least 18 : 1 ) . This was surprising because particles and defects typically found in resins having an ash content of greater than 0.2 wt.% are known to be stress concentrators that could prevent the multilayer film from successfully being stretched.

[0104] It is expressly contemplated that the multilayer film made by such methods may be according to any embodiment of the multilayer films of the first aspect, described in detail above.

[0105] Listing of Exemplary Embodiments

[0106] In a first embodiment, the present disclosure provides a multilayer film comprising: a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 weight percent (wt.%), based on the total weight of the first polypropylene; a first skin layer comprising a second polypropylene; and a second skin layer comprising a third polypropylene, wherein the core layer is disposed between the first skin layer and the second skin layer, and wherein the first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

[0107] In a second embodiment, the present disclosure provides a multilayer film according to the first embodiment, which is biaxially oriented.

[0108] In a third embodiment, the present disclosure provides a multilayer film according to the first embodiment, which is monoaxially oriented.

[0109] In a fourth embodiment, the present disclosure provides a multilayer film according to any of the first through third embodiments, wherein the core layer exhibits a melt flow index between 2 and 20 grams per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms.

[0110] In a fifth embodiment, the present disclosure provides a multilayer film according to any of the first through fourth embodiments, wherein each of the first skin layer and the second skin layer exhibits a melt flow index between 2 and 10 grams per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms.

[0111] In a sixth embodiment, the present disclosure provides a multilayer film according to any of the first through fifth embodiments, wherein the first polypropylene has an ethylene segment mixture between 0.6 to 15 wt.% as determined by Nuclear Magnetic Resonance (NMR).

[0112] In a seventh embodiment, the present disclosure provides a multilayer film according to any of the first through sixth embodiments, wherein each of the first skin layer and the second skin layer has a polypropylene having an ethylene segment mixture between 0 to 3 wt.% as determined by NMR.

[0113] In an eighth embodiment, the present disclosure provides a multilayer film according to any of the first through seventh embodiments, wherein each of the first skin layer, the second skin layer, and the core layer exhibits a melting point of between 155 and 170 degrees Celsius, using differential scanning calorimetry determined according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

[0114] In a ninth embodiment, the present disclosure provides a multilayer film according to any of the first through eighth embodiments, wherein the core layer further comprises at least one antioxidant.

[0115] In a tenth embodiment, the present disclosure provides a multilayer film according to the ninth embodiment, wherein the core layer exhibits an oxidation induction time in air at 200 degrees Celsius of at least 100 minutes, as determined by differential scanning calorimetry.

[0116] In an eleventh embodiment, the present disclosure provides a multilayer film according to any of the first through tenth embodiments, having a density of greater than 0.72 grams per cubic centimeter.

[0117] In a twelfth embodiment, the present disclosure provides a multilayer film according to any of the first through eleventh embodiments, having a thickness of less than 2 mils (less than 50.8 micrometers) and exhibiting a barcode decodability score within 0.6 of the barcode when uncovered, determined according to ISO Method 15416-1.

[0118] In a thirteenth embodiment, the present disclosure provides a multilayer film according to any of the first through twelfth embodiments, wherein the core layer contains a pentad component of first polypropylene segments that is isotactic of 85% to 91% as measured by NMR.

[0119] In a fourteenth embodiment, the present disclosure provides a multilayer film according to any of the first through thirteenth embodiments, wherein each of the first skin layer and the second skin layer contains a pentad component of second polypropylene segments and third polypropylene segments, respectively, that is isotactic of between 85% to 92% as measured by NMR.

[0120] In a fifteenth embodiment, the present disclosure provides a multilayer film according to any of the first through fourteenth embodiments, comprising at least one void within the core layer.

[0121] In a sixteenth embodiment, the present disclosure provides a multilayer film according to the fifteenth embodiment, wherein the at least one void is located at a depth from an exterior surface of the first skin layer or the second skin layer that greater than 5% of a full thickness of the multilayer film.

[0122] In a seventeenth embodiment, the present disclosure provides a multilayer film according to any of the first through sixteenth embodiments, having a thickness in a range of from 0.5 mils (12.7 micrometers) to 3 mils (76.2 micrometers) and exhibiting a haze of no more than 90%.

[0123] In an eighteenth embodiment, the present disclosure provides a multilayer film according to any of the first through seventeenth embodiments, which is formed of at least 15 wt.% of post-industrial recycled material, based on the total weight of the multilayer film.

[0124] In a nineteenth embodiment, the present disclosure provides a multilayer film according to any of the first through eighteenth embodiments, comprising 60-95 wt.% of the core layer and 5-40 wt.% of a combination of the first skin layer and the second skin layer, in which a combination of the core layer, first skin layer, and second skin layer total 100 wt.%.

[0125] In a twentieth embodiment, the present disclosure provides a multilayer film according to any of the first through nineteenth embodiments, wherein at least 30 wt.% of the core layer is the first polypropylene, based on a total weight of polymeric materials in the core layer.

[0126] In a twenty -first embodiment, the present disclosure provides a multilayer film according to any of the first through twentieth embodiments, further comprising at least one additive present in at least one of the core layer, the first skin layer, or the second skin layer.

[0127] In a twenty-second embodiment, the present disclosure provides a multilayer film according to any of the first through twenty -first embodiments, which displays two crystallization peaks in a differential thermogram.

[0128] In a twenty -third embodiment, the present disclosure provides a tape comprising the multilayer film according to any of the first through twenty-second embodiments and an adhesive disposed on at least a portion of the first skin layer opposite the core layer.

[0129] In a twenty -fourth embodiment, the present disclosure provides a tape according to the twenty- third embodiment, further comprising a low adhesion backsize disposed on at least a portion of the second skin layer opposite the core layer.

[0130] In a twenty-fifth embodiment, the present disclosure provides a method of making a multilayer film, the method comprising: coextruding a first skin composition, a core composition, and a second skin composition, thereby forming a three-layer multilayer film comprising: a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 weight percent (wt.%), based on the total weight of the first polypropylene; a first skin layer comprising a second polypropylene; and a second skin layer comprising a third polypropylene, wherein the core layer is disposed between the first skin layer and the second skin layer, and wherein the first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

[0131] In a twenty-sixth embodiment, the present disclosure provides a method of making a multilayer film according to the twenty -fifth embodiment, further comprising biaxially orienting the multilayer film.

[0132] In a twenty-seventh embodiment, the present disclosure provides a method of making a multilayer film according to the twenty -sixth embodiment, where the multilayer film is biaxially oriented to a ratio of a final stretched area to an unoriented area of at least 40:1.

[0133] In a twenty -eighth embodiment, the present disclosure provides a method of making a multilayer film according to the twenty -fifth embodiment, further comprising monoaxially orienting the multilayer film.

[0134] In a twenty-ninth embodiment, the present disclosure provides a method of making a multilayer film according to the twenty -eighth embodiment, where the multilayer film is monoaxially oriented to a ratio of a final stretched area to an unoriented area of at least of 3 : 1.

[0135] In a thirtieth embodiment, the present disclosure provides a method of making a multilayer film according to any of the twenty -fifth through twenty-ninth embodiments, wherein the multilayer film is according to any of the first through twenty -second embodiments.EXAMPLES

[0136] Unless otherwise noted or readily apparent from the context, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight.Material CharacterizationTest Methods:Differential Scanning Calorimetry (DSC) :

[0137] DSC was used extensively to characterize the thermal transitions, oxidative stability, and screen for polymeric impurities in the resins.DSC-Oxidation Induction Time (OIT)

[0138] This procedure, called DSC-OIT, measures the oxidative stability of materials and is defined by the onset time required to begin oxidizing a material in the presence of oxygen. Using a TA Instruments Q200, the sample is prepared in an open pan, equilibrated at 50 °C, heated to 200 °C at 10 / min under a nitrogen flow and isothermed at 200 C for 5 minutes. The gas flow is then switched to air. The sample was then isothermed at 200 °C for > 120 minutes under air. The OIT is then defined as the time interval between the beginning of the isothermal step under air, to, and the onset of oxidiation, tonsetOIT — / onset - to.DSC - Heat-Cool-Heat (HCH)

[0139] This procedure, called DSC-HCH, measures the melting point, Tm, and crystallization temperature(s), Tc, of the material according to ASTM Method D3418-21 using a heating and cooling rate of 10 C / min. For this procedure, a sealed DSC pan is used under nitrogen gas, unlike the open pan procedure described above. The sample is initially cooled to -80 °C and then heated to 190 °C at a constant heating rate of 10 °C / min. An annealing step at 190 °C is omitted to avoid thermal degradationof the material. The sample is then cooled back to -80 °C at 10 °C / min. One or more crystallization peaks can be observed. The sample is then reheated back to 190 °C at 10 °C / min. The second heat thermogram is used to provide information regarding the melting point and can be used to identify polymeric impurities.

[0140] The quantification of %PE by DSC is set to zero if no melting peak is observed in the vicinity of 120 °C. If a peak is observed in this region, the peak is integrated from baseline to baseline where care is taken to not integrate the PP region, which can show a peak onset as low as 145 °C. A reference value of 293 J / g was for the polyethylene heat of fusion. Thus, the %PE as measured by DSC is a measurement of the crystallizable portion of the polyethylene segments.

[0141] In some instances, especially for multilayer films, the cooling curve may exhibit two crysatllization temperatures. If the peaks are not well separated, they can be decovoluted into a sum of Gaussians with a background function using non-linear least squares over the range of -50 to 180 °C. If the thermogram exhibits only one crystallization temperature, the thermogram can be fit to one Gaussain function. The equations for the 1 Gaussian fit and 2 Gaussian fit are listed below. In both instances, they include a background function.1G: / (T) = Aiexp( -AT- fy) / Ci2) + ml + b2G: / (T) = Aiexp( -(T - 71 ) / C i2) + A2exp( -(T - 72) / C22) + mT + b where T i and Z2are the first and second crystallization temperatures. The goodness of the fit is evaulationed by the root mean squared deviation between theTGA - %Ash:

[0142] Thermogravimetric analysis (TGA) is used to measure %volatiles and %ash for recycled materials. The %volatiles are determined by heating the sample under nitrogen to 120 °C and followed by an isothermal hold for 20 minutes. After the isotherm, the sample is then heated to 550 °C at 10 °C / min. The %ash is then computed by ratioing the final weight with the initial weight.Bulk - %Ash

[0143] Three aliquots of approximately 1-5 grams were obtained from each as-received sample and placed individually into porcelain crucibles. The aliquots were initially weighed to obtain a before ashing mass (in grams). The initially weighed aliquots within the porcelain crucibles were then covered and placed in a muffle furnace for at least twenty hours at 543°C (1000°F). The ashed aliquots within the crucibles were subsequently taken out of the furnace, allowed to cool, the covers removed, and then reweighed to obtain an after ashing mass (in grams). The percent ash results in each sample were calculated using the following equation:Percent (%) Ash = ^ass in grams W) AFTER AShina*10QMass in grams [g\) BEFORE AshingThe %ash as determined by the bulk ash and TGA methods should agree with the caveat that the TGA uses a smaller sample size and requires more replicates.Melt Flow Index

[0144] The melt flow index, MFI, is measured using a Tinius-Olsen MP600 instrument. In the MFI test, the material is packed in a heated barrel and allowed to melt. The barrel is heated to 230 °C. Sufficient time is given to allow for air bubbles to escape. A weight of 2.16 kg is placed on top of a piston and the polymer is forced through a single orifice die. The orifice is 2.095 mm. The extrudate is cut with scissors once the resin begins to flow without the presence of air bubbles. The str seconds until there is no more resin left for a complete 30 second sample. After c samples are weighed to the nearest 1000th of a gram. The MFI is then calculated 600, which produces a value with units of gm / (10 min). For reference, see ASTXylene Soluble Fraction

[0145] The Xylene soluble fraction, XSF, is a test for measuring the percent of xylene soluble material in polypropylene (PP) resins. The results are both reported in terms of mass percent.

[0146] The method used here is as follows: 1) 2 gm of PP sample was weighed out and transferred to a 4 oz. jar. 2) 75 gm of xylene was added to the 4 oz. jar. 3) The jar is sealed with a lid and wrapped with electrical tape. 4) The jar is heated in an aluminum block heater for 1 hour at 145 °C. At least once during the hour, the jar is removed from the heating block and inverted to help mix the material. 5) The material is cooled overnight. 6) The precipitated PP was filtered off using gravity filtration. 7) 10 mL of mother liquor was transferred to a tared- Aluminum weighing boat using a volumetric pipette. (The aluminum weighing boat was previously heated to 150 °C for 10 minutes and allowed to cool.) 8) The aluminum weighing boat with xylene solution was heated on a hot plate until all of the xylene had boiled off and the weight was constant. 9) The XSF was calculated as:%XSF = ((75gm / 0.87 g / mL) / 10 mL* xsoiubie) / xinitiai )* 100 where 0.87 g / mL is the density of xylene at standard conditions. In all instances, exact masses and volumes were used.High Temperature Gel Permeation Chromatography (HT-GPC)

[0147] Samples were analyzed by HT-GPC against narrow molecular weight polystyrene molecular weight standards. A measured 20 mg of sample was dissolved in 8 mL of 1,2,4-trichlorobenzene at 160 °C. The samples were then injected into a PLGel Mixed-B column and eluted at 150 °C. The molecular weight calculations were performed using the GPC One Software from Polymer Char. The molecular weight results and distribution curves are based on the calibration against narrow molecular weight polystyrene standards. Thus, the molecular weight results are not absolute, but they are relative to the hydrodynamic volume of polystyrene in the eluent and some uncertainty is expected. The key properties are M„ (Number-averaged molecular weight) and M„ (weight-averaged molecular weight). The poly dispersity index (PDI) is defined as Mw / M„.

[0148] Nuclear Magnetic Resonance (NMR): The NMR samples were prepped by dissolving the sample material in deuterated orthodichlorobenzene along with chromium(III) acetylacetonate. The sample was heated to fully dissolve the sample. A Bruker 600 MHz NMR was used to record the C-13 spectra. For the microstructure, we can determine the percent isotactity as measured by the mass fraction of pentads, the fraction of pentads containing defects, co-monomers, and regio-errors. Table 1 reports the integration limits used for the different microstmctures.Table 1. Integration limits used for the NMR analysis.

[0149] To compute the isotacticity, integrals for all of the pentads (112 - 120) are summed together and assigned variableThe isotactity fraction based on pentads is thenThe single-site defects are computedThe %ethylene segment mixture, by NMR, by NMR, is computed as (Ew+ Bw+ Hw) / TwTw= Pw+ Elv+ Bw+ Hw+ VAWPw= 42.08 (I2+ (I3+ I4) / 2 + I6)E„ = 28.05 (Bw= 56.12Hw= 84.16Barcode Verification

[0150] The barcode decodability as defined by ISO / IEC 15416-1 was determined using an Inspector 5000 Laser Verifier manufactured by RJS Technologies (Golden Valley, MN). The decodability of a printed GS 1-128 linear barcode was measured by scanning on a flat, non-reflective surface. The trigger was pulled while the laser beam was not over the barcode, then the distance of the laser was adjusted so that the beam was approximately twice as wide as the barcode and the angle of the laser exit window was approximately 30 degrees off vertical. Once at the proper angle and distance, the laser beam was brought over the barcode, maintaining the angle and distance. The 10-Scan Average Decodability was recorded. This procedure was repeated with films representing examples placed over the barcode. The barcode without a film covering it reads as a 4.0.Tensile and Elongation

[0151] The Tensile and Elongation properties were measured per the ASTM D882 - 18 Standard Test Method for Tensile Properties of Thin Plastic Sheeting. The test conditions were 10 in / min, sample width = 1 in, sample length = 6 in (gage length = 4 in) using an MTS Criterion Model 41 with 1000N load cell. The reported values are for the machine (MD).Haze, Transmittance, Cdarity

[0152] Haze, Transmittance, and Clarity were measured with a Haze-gard Plus instrument available from BYK-Gardner in conformity with ASTM D-1003.MaterialsTable 2A. Polypropylenesax 105Table 2B, Polypropylenes, continuedTable 3. Antioxidants and additives.%Ash Meaurement

[0153] PP-6 was also extruded with and without antioxidants to study the effects of antioxidants on %ash. The %ash was also measured by the previously described TGA method and ASTM B923. The results are shown in Table 4.Table 4, %ash as measured by TGA and ASTM B923,

[0154] For Comparative Film Examples FC-01 - FC-03 and Film Examples FE-01 - FE-08, a cast film was made by coextruding a multilayer melt stream having core and skin layers. The multilayer melt stream was cast onto a chilled roll and subsequently stretched using a continuous drawing process. The cast film was conveyed into a machine direction orienter (MDO), heated to a nominal temperature of 140- 150 °C, and stretched to a draw ratio ranging from 4 to 6. The film was then conveyed into a conventional tenter, preheated to a nominal temperature of 150 - 188 °C and drawn transversely to a peak nominal draw ratio of between 7 to 9. The films underwent an additional heat set before trimming and winding. The compositions of the oriented films are reported in Table 5 and the thickness are reported in Table 7.The thickness values can show variability up to 10%. In the films, the %core is 80% by mass relative to the skin layers.Table 5. Film compositions and thicknesses.RTP 199 X 143759 A NATURAL

[0155] The 1st cooling crystallization properties of the films in Table 5 were measured by DSC and the cooling curves were fit to 1 Gaussian (1G) and 2 Gaussian (2G) functions, as described above. FC-01 and FC-02 are films that only exhibit 1 crystallization temperature, which can be demonstrated by a low root mean squared deviation (RMSD) value when fitted to the 1G function and the RMSD does not significantly improve when the 2G function is used. Film examples FE-01 through FE-08 exhibit two crystallization temperatures and lower RMSD errors when fit to the 2G function.Table 6Table 7, Film properties for comparative films FC-01 - FC-03 and Example Films FE-01 - FE-08.

[0156] In Table 8, Comparative Examples 1 - 2 and Examples 6 - 7 report on the %ash values for multilayer films. These films were extruded using an 80 micron filter.Table 8: %ash as measured by TGA method

[0157] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

[0158] Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description prevails. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims.

Claims

What is claimed is:

1. A multilayer film comprising: a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 weight percent (wt.%), based on the total weight of the first polypropylene; a first skin layer comprising a second polypropylene; and a second skin layer comprising a third polypropylene, wherein the core layer is disposed between the first skin layer and the second skin layer, and wherein the first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21 at 10 degrees Celsius per minute.

2. The multilayer film of claim 1, which is biaxially oriented.

3. The multilayer film of claim 1, which is monoaxially oriented.

4. The multilayer film of any of claims 1 to 3, wherein the core layer exhibits a melt flow index between 2 and 20 grams per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms.

5. The multilayer film of any of claims 1 to 4, wherein each of the first skin layer and the second skin layer exhibits a melt flow index between 2 and 10 grams per 10 minutes at 230 degrees Celsius under a weight of 2.16 kilograms.

6. The multilayer film of any of claims 1 to 5, wherein the first polypropylene has an ethylene segment mixture between 0.6 to 15 wt.% as determined by Nuclear Magnetic Resonance (NMR).

7. The multilayer film of any of claims 1 to 6, wherein each of the first skin layer and the second skin layer has a polypropylene having an ethylene segment mixture between 0 to 3 wt.% as determined by NMR.

8. The multilayer film of any of claims 1 to 7, wherein each of the first skin layer, the second skin layer, and the core layer exhibits a melting point of between 155 and 170 degrees Celsius, using differential scanning calorimetry determined according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

9. The multilayer film of any of claims 1 to 8, wherein the core layer further comprises at least one antioxidant.

10. The multilayer film of claim 9, wherein the core layer exhibits an oxidation induction time in air at 200 degrees Celsius of at least 100 minutes, as determined by differential scanning calorimetry.

11. The multilayer film of any of claims 1 to 10, having a density of greater than 0.72 grams per cubic centimeter.

12. The multilayer film of any of claims 1 to 11, having a thickness of less than 2 mils (less than 50.8 micrometers) and exhibiting a barcode decodability score within 0.6 of the barcode when uncovered, determined according to ISO Method 15416-1.

13. The multilayer film of any of claims 1 to 12, wherein the core layer contains a pentad component of first polypropylene segments that is isotactic of 85% to 91% as measured by NMR.

14. The multilayer film of any of claims 1 to 13, wherein each of the first skin layer and the second skin layer contains a pentad component of second polypropylene segments and third polypropylene segments, respectively, that is isotactic of between 85% to 92% as measured by NMR.

15. The multilayer film of any of claims 1 to 14, comprising at least one void within the core layer.

16. The multilayer film of claim 15, wherein the at least one void is located at a depth from an exterior surface of the first skin layer or the second skin layer that greater than 5% of a full thickness of the multilayer film.

17. The multilayer film of any of claims 1 to 16, having a thickness in a range of from 0.5 mils (12.7 micrometers) to 3 mils (76.2 micrometers) and exhibiting a haze of no more than 90%.

18. The multilayer film of any of claims 1 to 17, which is formed of at least 15 wt.% of postindustrial recycled material, based on the total weight of the multilayer film.

19. The multilayer film of any of claims 1 to 18, comprising 60-95 wt.% of the core layer and 5-40 wt.% of a combination of the first skin layer and the second skin layer, in which a combination of the core layer, first skin layer, and second skin layer total 100 wt.%.

20. The multilayer film of any of claims 1 to 19, wherein at least 30 wt.% of the core layer is the first polypropylene, based on a total weight of polymeric materials in the core layer.

21. The multilayer film of any of claims 1 to 20, further comprising at least one additive present in at least one of the core layer, the first skin layer, or the second skin layer.

22. The multilayer film of any of claims 1 to 21, which displays two crystallization peaks in a differential thermogram.

23. A tape comprising the multilayer film of any of claims 1 to 22 and an adhesive disposed on at least a portion of the first skin layer opposite the core layer.

24. The tape of claim 23, further comprising a low adhesion backsize disposed on at least a portion of the second skin layer opposite the core layer.

25. A method of making a multilayer film, the method comprising: coextruding a first skin composition, a core composition, and a second skin composition, thereby forming a three-layer multilayer film comprising: a core layer comprising a first polypropylene having an ash content of 0.2 to 5.0 weight percent (wt.%), based on the total weight of the first polypropylene; a first skin layer comprising a second polypropylene; and a second skin layer comprising a third polypropylene, wherein the core layer is disposed between the first skin layer and the second skin layer, and wherein the first polypropylene displays a crystallization peak higher than the second polypropylene according to ASTM Method D3418-21, at a cooling rate of 10 degrees Celsius per minute.

26. The method of claim 25, further comprising biaxially orienting the multilayer film.

27. The method of claim 26, where the multilayer film is biaxially oriented to a ratio of a final stretched area to an unoriented area of at least 40 : 1.

28. The method of claim 25, further comprising monoaxially orienting the multilayer film.

29. The method of claim 28, where the multilayer film is monoaxially oriented to a ratio of a final stretched area to an unoriented area of at least of 3 : 1.

30. The method of any of claims 25 to 29, wherein the multilayer film is of any of claims 1 to 22.

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