LOW-DENSITY POLYETHYLENE WITH HOT BOND STRENGTH AND METAL ADHESION IMPROVED BY THE ADDITION OF IONOMERS

Abstract

Polymer blends, films, and coated substrates, including polymer blends. The polymer blends include at least 90 wt% low-density polyethylene polymer and 1 to 10 wt% ionomer. The LDPE polymer has a melting index (I2) of 2 g / 10 min to 6 g / 10 min and a molecular weight distribution of 5 to 11, as determined by a conventional gel permeation chromatography method. The ionomer includes an ethylene-acid copolymer, in which 15% to 70% of the acid groups are neutralized with a sodium cation, depending on the total amount of acid groups in the acid copolymer. The ethylene and acid copolymer is the polymerized reaction product of: at least 50% by weight of ethylene, from 2% to 40% by weight of monocarboxylic acid monomer, and from 0 to 20% by weight of alkyl acrylate, depending on the total weight % of the monomers present in the ethylene and acid copolymer.

Description

LOW-DENSITY POLYETHYLENE WITH HOT BOND STRENGTH AND METAL ADHESION IMPROVED BY THE ADDITION OF IONOMERS FIELD OF INVENTION The modalities of the present description generally refer to polymer blends for extrusion coating that have improved hot bond strength compared to LDPE polymers, and improved adhesion to metal of the polymer blends; and coated films and substrates that include the polymer blends. BACKGROUND OF THE INVENTION Low-density polyethylene (LDPE) is widely used in the extrusion coating process to make food packaging, such as coated cartons for milk and coated films for condiment sachets. The LDPE coating provides airtight seals to protect the product from leakage. During the sealing process, the sealing area is heated to melt and bond the sealant. Hot adhesion is the ability of the newly formed seal to remain bonded before cooling back to a solid state. High hot adhesion strength is needed to form strong seals on a package to prevent leaks. Generally, LDPE has adhesion strength κ / ηίηη / ζζηζ / Ε / γίΛΐ Ref. 331142 poor hot adhesion. This is generally believed to be due to the high level of long-chain branching in LDPE polymers. Long-chain branching impedes molecular diffusion at the interface between the two contact surfaces during heat sealing. This diffusion is necessary to develop hot adhesion strength, and a lack of diffusion, such as that caused by the highly twisted path created by long-chain branching, results in poor hot adhesion. Hot adhesion is further reduced for LDPE polymers with a low melt index, typically less than 6.0 dg / min. A low melt index generally indicates a higher molecular weight, which also slows diffusion at the interface. Strong peel strength is needed to prevent delamination between the coating and the substrate, thus maintaining the integrity of the packaging. To allow polyethylene coatings to adhere to polar substrates, the coatings must be oxidized. Generally, polyethylene coatings oxidize with prolonged exposure to air and high temperatures. However, this method does not consistently create improved peel strength. SUMMARY OF THE INVENTION There is a continuing need to create a polymer or polymer blend that, when placed as a coating on a substrate, has a maximum hot bond strength of more than 9.5 N / inch with a sealing bar temperature of 120°C to 160°C and a maximum load peel strength of more than 2 N / inch. The modalities of this description include a polymer blend. The polymer blend includes at least 90 wt% of a low-density polyethylene (LDPE) polymer and 1 to 10 wt% of an ionomer. The LDPE polymer has a melting index (I3) of 2 g / 10 min to 6 g / 10 min as determined in accordance with ASTM D1238 (190 °C, 2.16 kg, Procedure B) and a conventional molecular weight distribution (MWD = Mw / Mn, conv.) as determined by conventional triple detector gel permeation chromatography (TDGPC) calibration of 5 to 11. The ionomer includes an ethylene-acid copolymer, in which 15 to 70% of the carboxylic acid groups are neutralized as carboxylic acid salts including sodium cations.The ethylene and acid copolymer is the polymerized reaction product of: at least 50 wt% ethylene, depending on the total wt% of monomers present in the ethylene and acid copolymer; from 2 wt% to 30 wt% monocarboxylic acid monomer, depending on the total wt% of monomers present in the ethylene and acid copolymer; and from 0 wt% to 25 wt% alkyl acrylate, depending on the total wt% of monomers present in the ethylene and acid copolymer. The forms described herein include coated substrates. Coated substrates include a substrate and a coating comprising the polymer mixture described herein. BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a graph of hot bond strength as a function of sealing bar temperatures for Example 3 and AGILITY EC 7030™. DETAILED DESCRIPTION OF THE INVENTION The variations described here include a polymer blend. The polymer blend includes at least 90% by weight of low-density polyethylene (LDPE) polymer and from 1% to 10% by weight of ionomer. In some embodiments of the polymer blend, the LDPE polymer has a melt index (I2) of 2 g / 10 min to 6 g / 10 min as determined according to ASTM D1238 (190 °C, 2.16 kg). In various embodiments, the LDPE polymer has a melt index (I2) of 3 g / 10 min to 5 g / 10 min, or of 2 g / 10 min to 4.5 g / 10 min. In one or more forms of the polymer blend, the LDPE polymer has a molecular weight distribution (MWD = Mw / Mn) of 5 to 11, 8 to 10, or 8.5 to 11 as determined by a conventional gel permeation chromatography method. In some embodiments of the polymer blend, the LDPE polymer is produced using a tubular reactor. The LDPE polymer can have a density of 0.910 g / cc to 0.930 g / cc. In some embodiments, the LDPE polymer can have a density of 0.910 g / cc to 0.920 g / cc, 0.916 g / cc to 0.930 g / cc, 0.918 g / cc to 0.926 g / cc, or 0.915 g / cc to 0.920 g / cc. In one or more embodiments, the polymer blend includes from 1% to 7% by weight or from 1% to 5% by weight of the ionomer. In some embodiments, the polymer blend includes from 3% to 6% by weight, from 4% to 6% by weight, or from 5% to 7% by weight of the ionomer. In one or more embodiments of the polymer blend, the ionomer includes an ethylene-acid copolymer, wherein the acid copolymer has 15% to 70% of the carboxylic acid groups neutralized as carboxylic acid salts comprising sodium cations. The percentage is based on the total amount of acid groups in the polymer. In some embodiments, the ethylene-acid copolymer has 40% to 60%, 30% to 70%, or 40% to 70% of the carboxylic acid groups neutralized as carboxylic acid salts comprising sodium cations. The ethylene and acid copolymer is the polymerized reaction product of: at least 50 wt% of ethylene, depending on the total wt% of the monomers present in the ethylene and acid copolymer; from 2 wt% to 30 wt% of monocarboxylic acid monomer, depending on the total wt% of the monomers present in the ethylene and acid copolymer; and from 0 to 25 wt% of alkyl acrylate, depending on the total wt% of the monomers present in the ethylene and acid copolymer. In one or more embodiments, the ethylene-acid copolymer is the polymerized reaction product of ethylene monomer, monocarboxylic acid monomer, and optionally alkyl acrylate monomer. The monocarboxylic acid monomer may be present in amounts of 2 wt% to 25 wt%, 8 wt% to 25 wt%, 8 wt% to 20 wt%, 5 wt% to 23 wt%, 15 wt% to 30 wt%, or 20 to 25 wt%, depending on the total wt% of the monomers present in the ethylene-acid copolymer. Alkyl acrylate may be present in amounts from 0% by weight to 20% by weight, from 1% by weight to 10% by weight, or from 4% by weight to 15% by weight depending on the total weight % of monomers present in the ethylene and acid copolymer. In some embodiments of the polymer blend, the alkyl acrylate of the acid copolymer may be, by way of example and not limitation, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, or combinations thereof. In various embodiments, the alkyl acrylate is a C2-C8 alkyl acrylate, that is, an alkyl acrylate having an alkyl group with 1 to 8 carbons. In various forms of the polymer blend, the monocarboxylic acid monomer comprises acrylic acid, methacrylic acid, or combinations thereof. In one or more embodiments of the polymer blend, the ionomer has a melt index (I2) of 0.5 g / 10 min to 15 g / 10 min as determined in accordance with ASTM D1238 (190 °C, 2.16 kg). In some embodiments, the ionomer has a melt index (I2) of 4 g / 10 min to 10 g / 10 min, 0.5 to 10 g / 10 min, or 0.5 to 4 g / 10 min. The ethylene-acid copolymer can be prepared by standard free-radical copolymerization methods under high pressure and continuous operation. Monomers are introduced into the reaction mixture in a ratio related to the monomer's activity and the amount of monomer to be incorporated into the copolymer. This results in a uniform and nearly random distribution of monomer units along the chain. Unreacted monomers can be recycled. Additional information on the preparation of ethylene-acid copolymers can be found in U.S. Patent Nos. 3,264,272 and 4,766,174, each of which is incorporated herein by reference in its entirety. κ / ηίηη / ζζηζ / Ε / γίΛΐ Additional information on the preparation of ionomers can be found in U.S. Patent No. 3,264,272 A, U.S. Patent No. 3,322,734 A and U.S. Patent No. 9,783,352 B2, each of which is incorporated herein by reference in its entirety. As would be familiar to those in the mid-level trade, the components can be blended in various ways, such as dry blending or melt blending. For example, the ionomer and LDPE polymer can be dry blended, for instance, by adding the components as pellets to an extruder, where they are heated and mixed together and then applied as a coating to the substrate. Alternatively, the ionomer and LDPE polymer can be melt blended, where each component is melted and blended in the mixer or extruder and then pelletized. The pellets are then fed into the extruder to produce the coated substrate. Other blending methodologies for mixing the components are also considered herein. In some embodiments, the polymer blend does not include additives. In one or more embodiments, the polymer blend may include additives. The polymer blend may also include small amounts of additives, including plasticizers, stabilizers (including viscosity stabilizers, hydrolytic stabilizers), primary and secondary antioxidants, ultraviolet light absorbers, antistatic agents, dyes, pigments or other coloring agents, inorganic fillers, flame retardants, lubricants, reinforcing agents such as fiberglass and sheets, synthetic fiber or pulp (e.g., aramid), foaming or blowing agents, processing aids, slip additives, antiblocking agents such as silica or talc, release agents, tack-enhancing resins, or combinations of two or more of these.Inorganic fillers, such as calcium carbonate, and similar materials, can also be incorporated into the mixture. Various embodiments of this description include a coated substrate. The coated substrate includes a substrate and a coating bonded to the substrate. The coating includes any of the polymer blends disclosed in this description. In various embodiments, a coextrusion adhesive is disposed between the polymer substrate and the coating. In one or more embodiments of the coated substrate, the substrate includes a metallic substrate, a polymer substrate, or a paper substrate. In some embodiments, the polymer substrate includes polyester, polyethylene, polypropylene, polyamide, metallized polyester, metallized polyethylene, metallized polypropylene, or metallized polyamide. In several embodiments, the metallic substrate may be aluminum. In one or more embodiments, the coated substrate has a maximum load peel strength of at least 2 N / in. In some embodiments, the coated substrate has a maximum hot bond strength of at least 9.5 N / in within a sealing bar temperature range of 120°C to 160°C, as measured by ASTM F-1921 (Method B). The forms described herein include films made from the polymer blends described above. The film is extruded from any of the polymer blends described herein. Hot bond strength is the force per unit length, in newtons per inch, required to separate two films in a partially molten condition. This test is used to simulate a container's ability to maintain its seal and prevent leakage while the heat seal is still hot. Because the ionomer described here was mixed into the LDPE, the hot bond strength increased, as did the temperature range in which hot bonding was observed. Polymerizations The acid copolymer and LDPE used to manufacture the ionomer are produced by high-pressure free-radical polymerization. Two basic types of reactors are known for a high-pressure free-radical-initiated polymerization process. The first type is a stirred autoclave vessel with one or more reaction zones (the autoclave reactor). The second type is a coated tube with one or more reaction zones (the tubular reactor). The pressure in each tubular reactor and autoclave zone of the process is typically from 100 MPa to 400 MPa, more typically from 120 MPa to 360 MPa, and even more typically from 150 MPa to 320 MPa. The polymerization temperature in each tubular reactor zone of the process is typically from 100 °C to 400 °C, from 130 °C to 360 °C or from 140 °C to 330 °C. The polymerization temperature in each autoclave reactor zone of the process is typically 150°C to 300°C, 165°C to 290°C, or 180°C to 280°C. A person of average skill understands that polymerization temperatures in autoclave reactors are considerably lower than those in a tubular reactor, and therefore, more favorable extractable levels are generally observed in polymers produced in an autoclave-based reactor system. A tubular reactor having at least three reaction zones can be used to produce the polymer mixtures of this description. To produce an ethylene-based polymer of the invention, including an inventive LDPE, a high-pressure, free-radical-initiated polymerization process is typically used. A coated tube is generally used as a reactor, having one or more reaction zones. Suitable, but not limiting, reactor lengths can be from 100 to 3000 meters (m), or from 1000 to 2000 meters. The start of a reaction zone for the reactor is typically defined by the side injection of the reaction initiator, ethylene, a chain transfer agent (or telogen), or any combination thereof. A high-pressure process can be carried out in one or more tubular reactors, each having one or more reaction zones, or in a combination of autoclave and tubular reactors, each comprising one or more reaction zones. A chain transfer agent can be used to control the molecular weight. In a preferred embodiment, one or more chain transfer agents (CTAs) are added to an inventive process. Typical CTAs that can be used include, but are not limited to, propylene, n-butane, 1-butene, isobutane, propionaldehyde, and methyl ethyl ketone. In one embodiment, the amount of CTA used in the process is from 0.03 to 10 percent by weight of the total reaction mixture. The ethylene used for the production of the ethylene-based polymer can be purified ethylene, which is obtained by removing the polar components from a looped recycling stream, or by using a reaction system configuration in which only fresh ethylene is used to prepare the inventive polymer. It is not typical for only purified ethylene to be required to prepare the ethylene-based polymer. In such cases, ethylene from the recycling loop can be used.In one form, the ethylene-based polymer is an LDPE. Initiators The process for producing the LDPE polymer described here is a free-radical polymerization process. The type of free-radical initiator used in this process is not critical, but preferably one of the initiators applied should allow operation at high temperatures in the range of 300 °C to 350 °C. Examples of suitable free-radical initiators include organic peroxides, such as peresters, percetals, peroxyketones, percarbonates, and multifunctional cyclic peroxides. These organic peroxy initiators are added to the reactor at a rate of 0.005 wt% to 0.2 wt%, depending on the total weight of polymerizable monomers in the reactor. The peroxides are usually injected as dilute solutions in a suitable solvent, for example, a hydrocarbon solvent. Other suitable initiators include azodicarboxylic esters, azodicarboxylic dinitriles and 1,1,2,2-tetramethylethane derivatives, and other components capable of forming free radicals in the desired operating temperature range. DEFINITIONS Unless otherwise stated, implied in the context, or customary in the art, all parts and percentages are by weight, and all test methods are current as of the date of submission of this description. The terms polymer blend or polymer mixture, as used in this description, mean an intimate physical mixture of two or more polymers without any chemical reaction between them. A blend may be miscible, with no phase separation at the molecular level, or it may be immiscible, exhibiting some degree of phase separation at the molecular level. A blend may include, but does not necessarily include, one or more domain configurations that can be determined from transmission electron spectroscopy, light diffraction, X-ray scattering, and other methods known in the art. The blend may be affected by physically mixing the two or more polymers at a macro or micro level. Examples of physical mixing at the macro level include the melt mixing of resins or the formation of compounds. An example of physical mixing at the micro level includes the simultaneous formation of the two or more polymers within the same reactor. The term polymer refers to a polymeric molecule prepared by the polymerization of monomers, whether of the same or different types. The generic term polymer therefore encompasses the terms homopolymer and copolymer. The term homopolymer refers to polymers prepared from a single type of monomer; the term copolymer refers to polymers prepared from two or more different monomers. The term ethylene-based polymer or ethylene polymer refers to a polymer comprising a majority of polymerized ethylene by weight. Ethylene-based polymers and ethylene polymers may be ethylene homopolymers or may include one or more comonomers, provided that ethylene constitutes the largest weight fraction of the polymer among all the monomers. The term monocarboxylic acid monomer means a molecule that has a reactive portion, such as vinyl or vinylene, which can bond with other monomers to form a polymer, and a carboxylic acid portion (-C(O)OH) that is not part of the reactive portion. For example, (meth)acrylic acid is a monocarboxylic acid monomer, in which vinylene is the reactive portion and there is a carboxylic acid. The term (meth)acrylic acid includes methacrylic acid and / or acrylic acid, and (meth)acrylate includes methacrylate, acrylate, or combinations of methacrylate and acrylate. TEST METHODS Density: Samples for density measurement are prepared in accordance with ASTM D 1928. Polymer samples are pressed at 190 °C and 30,000 psi for three minutes, and then at 21 °C and 207 MPa for one minute. Measurements are performed within one hour of sample pressing using ASTM D792, Method B. Melting index: The melting index, or I2, (grams / 10 minutes or dg / min) is measured in accordance with ASTM D 1238, Condition 190 °C / 2.16 kg, Procedure B. Triple detector gel permeation chromatography (3D-GPC) The chromatographic system includes a PolymerChar GPC-IR high-temperature GPC chromatograph (Valencia, Spain), equipped with an internal IR5 infrared detector coupled to a Precision Detectors (now Agilent Technologies) model 2040 two-angle laser light scattering (LS) detector. For all light scattering measurements, a 15-degree angle was used. The autosampler oven compartment is set to 160 °C, and the column compartment is set to 150 °C. Available columns include four 30-cm Agilent Mixed A linear mixed-bed columns, 20 micrometers in diameter. Available chromatographic solvents include 1,2,4-trichlorobenzene and contain 200 ppm butylated hydroxytoluene (BHT). The solvent source is sprayed with nitrogen. The injection volume that can be used includes 200 microliters (μA) and the flow rate was 1.0 milliliters / minute. The calibration of the GPC column array is performed using at least 20 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000, arranged in six cocktail mixtures with at least a decade of separation between them. This means there is an order of magnitude of approximately a factor of 10 between the individual molecular weights. The standards are purchased from Agilent Technologies. The polystyrene standards are prepared at 0.025 grams in 50 milliliters of solvent for molecular weights equal to or greater than 1,000,000, and at 0.05 grams in 50 milliliters of solvent for molecular weights less than 1,000,000. The polystyrene standards are dissolved at 80 degrees Celsius, with gentle stirring, for 30 minutes. The peak molecular weights of the polyethylene standard are converted to polyethylene molecular weights by using Equation 1 (as described in Williams and Ward, J. Polym. Sci., Polym.Let., 6, 621 (1968)):. ^polyethylene—d X (Mp0¡jestjren0) (EC. 1) where M is the molecular weight, A has a value of 0.4315 and B is equal to 1.0. A fifth-order polynomial is used to adjust the respective polyethylene-equivalent calibration points. A small adjustment to A (from approximately 0.415 to 0.44) is made to correct for column resolution and band-broadening effects to obtain the NIST NBS 1475 standard at 52,000 g / mol Mw. κ / ηίηη / ζζηζ / Ε / γίΛΐ The total plate count of the GPC column array is performed using eicosane (prepared at 0.04 g in 50 mL of TCB and dissolved for 20 minutes with gentle stirring). The plate count (Equation 2) and symmetry (Equation 3) are measured in a 200-microliter injection according to the following equations: / \2 Plate count = 5.54 * I---\(EC 2) \ Peak width to height I where RV is the retention volume in milliliters, peak width is in milliliters, peak maximum is the maximum peak height and height is the peak maximum height. Symmetry [RV df¡ peak / ronin;.,,, ,,,c' í -Tuvi-no*1' P:cofrontal.,,, dial: I (EC. 3) κ / ηίηη / ζζηζ / Ε / γίΛΐ where RV is the retention volume in milliliters, peak width is in milliliters, peak maximum is the maximum peak position, one-tenth of the height is 1 / 10 of the peak maximum height, and where trailing peak refers to the peak tail in trailing retention volumes compared to peak maximum, and where fronting peak refers to the peak front in leading retention volumes compared to peak maximum. The plate count for the chromatographic system must be greater than 24000 and the symmetry must be between 0.98 and 1.22. The samples were prepared semi-automatically using PolymerChar's Instrument Control software, where the samples were directed by weight to 2 mg / ml, and the solvent (containing 200 ppm of BHT) was added to a septum-capped vial previously sprayed with nitrogen, using PolymerChar's high-temperature autosampler. The samples were dissolved for 2 hours at 160 °C with low-speed stirring. The calculations of Mn(GPC), Mw(GPC) and Mz(GPG) are based on the GPC results using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph according to equations 4-6, using the PolymerChar GPCOne™ software, the chromatogram of the initial IR value subtracted at each of the equally spaced data collection points (i), and the equivalent molecular weight of polyethylene obtained from the narrow standard calibration curve for point (i) of Equation 1. Σ'* Mnc-.·:: =--------------------MA—.. J Ml\\oro·, =----------St MZ(GPC) = —----------------Σ A κ / μην / ζηζ / Ε / γίΛΐ In order to monitor deviations over time, a flow rate marker (decane) is introduced into each sample via a micropump controlled by the GPC-TR PolymerChar system. This flow rate marker (FM) was used to linearly correct the pump flow rate (nominal flow rate) for each sample by aligning the RV of the respective decane peak within the sample (RV(FM sample)) with that of the decane peak within the narrow calibration of the standards (RV(FM calibrated)). It is assumed that any change over time in the decane marker peak corresponds to a linear change in flow rate (effective flow rate) during the entire run.To facilitate maximum accuracy in a flow marker peak RV measurement, a least-squares fitting routine is used to fit the flow marker concentration chromatogram peak to a quadratic equation. The first derivative of the quadratic equation is used to determine the true peak position. After calibrating the system based on a flow marker peak, the effective flow rate (with respect to the tight calibration of the standards) is calculated as Equation 7. Flow marker peak processing was performed using PolymerChar GPCONe™ software. The acceptable flow rate correction is such that the effective flow rate must be within ±2% of the nominal flow rate. Flow rate (effective) = Flow rate (nominal) * (RV(FM calibrated) / RV(FM Sample)) (EC. 7) The systematic approach to determining the displacements of multiple detectors is carried out in a manner consistent with that published by Balke, Mourey et al. (Mourey and Balke, Chromatography Polym. Chapter 12, (1992)) (Balke, Thitiratsakul, Lew, Cheung, Mourey, Chromatography Polym. Chapter 13,

[1992] ), optimizing the triple detector logarithm (MW and IV) results of a wide homopolymer polyethylene standard (Mw / Mn >3) to narrow standard column calibration results from the narrow standards calibration curve using PolymerChar GPCONe™ software. Adhesion strength on street Hot adhesion measurements on the film are performed using a commercial Enepay testing machine in accordance with ASTM F-1921 (Method B). Prior to testing, the films are conditioned for a minimum of 40 hours at 23°C and 50% RH (relative humidity) in accordance with ASTM D-618 (Procedure A). The hot adhesion test simulates filling a sack or bag with the material before the seal has had a chance to cool completely. Sheets measuring 8.5 inches by 14 inches are cut from the coated substrate, with the longest dimension in the machine direction. Strips 1 inch wide and 14 inches long are cut from the coated substrate. The samples need only be long enough for clamping. Tests are performed on these samples at a range of temperatures, and the results are reported as the maximum load as a function of the sealing bar temperature. Typical temperature increments are 5°C or 10°C, and six repetitions are performed at each temperature. For the purposes of this description, testing in accordance with ASTM F-1921 (Method B) was completed with: Sample dimensions: 1.0 inch x 14 inches Sample width: 25.4 mm (1.0 inch) Sealing pressure: 0.275 N / mm2 Sealing time: 0.5 s Delay time: 0.18 s Peel speed: 200 mm / s Seal depth = 0.5 inches Sample thickness = 7.2 mils Coating thickness = 1.2 mils Wood paper thickness = 6.0 The data are reported as a hot bond curve where the average hot bond strength (N) is plotted as a function of temperature. The coated substrate consists of polymer extrusion coated onto wood paper. The wood paper thickness is 6 mils. The coating thickness is 1.2 mils. The average improvement in hot bond strength (N / in) is calculated using the following equation (hot bond strength at five sealing bar temperatures, 120, 130, 140, 150 and 160 °C, selected for calculation): .(¡[(hot bond strength of LDPE — ionomer) — yield bond strength of LOPE yuro] to Γ. 5 Peel resistance as measured by the peel test An aluminum foil (aluminum foil laminated with LDPE and white paper with a total thickness of 5.2 to 5.5 mils) is extruded with the polymer or polymer blend using an extrusion coating process. The coating is applied to the aluminum side and is 1.2 mils thick. Masking tape is placed on a portion of the aluminum foil before the polymer or polymer blend is extruded and applied as a coating. Because there is weak adhesion between the masking tape and the coating, the masking tape may peel off the coating before the peel test. The peel test is then used to determine the peel strength between the coating and the aluminum foil. Before the adhesion strength test, the samples were conditioned for a minimum of 40 hours at 23 °C (±2 °C) and 50% (+10%) relative humidity (RH). The extrusion-coated sheet to be evaluated is cut into 1-inch-wide strips along the machine direction with the longer side facing the machine. The coating is peeled off the aluminum sheet (starting from the location marked with masking tape), and then the two grips of the tensile testing machine grasp the ends of the aluminum sheet and the peeled coating. The entire sample is then slowly pulled out at 1 inch / min to eliminate slack. The sample is then tested at 12 inches / min, and the maximum load and average load above 3 inches (from 1 inch to 4 inches) are reported. The improvement in detachment resistance (%) is obtained from the following equation. (LDPE + ionomer peel strength) - (pure LDPE peel strength) pure LDPE peel strength obtained from the peel test, and the reported peel strength is the average of five samples evaluated. Extrusion coating The extrusion coating test is performed using the following standard coating procedures. In summary, single-layer coatings are extruded using a 3-layer extrusion coating line, employing only the primary 3.5-inch diameter (30:1 L / D) extruder fed by a 150 HP Eurotherm unit. The extruder barrel consists of 6 heating zones with a temperature profile of zones 1 to 6 = 179 / 230 / 286 / 316 / 317 / 318 °C (354 / 446 / 546 / 601 / 603 / 605 °F). A 30-inch Cloeren coat hanger type internal frame die EBR III (edge ​​build-up reduction) is used, and a die gap of 0.50.6 mm (0.020 in) and an air gap of 153 mm (6 in) were established. The line is equipped with a 30-inch cooling roll, a pressure roll, a backing roll, and a shear. Extrusion coating runs are performed at 30 gsm (grams per square meter) at 600 °F (315 °C), a spindle speed of 90 RPM and 250 lb / h, a die width of 24 inches and a die spacing of 20 mil, which translates to a coating thickness of 1.2 mil (30 micrometers) at 440 ft / min. EXAMPLES Example compositions were prepared and the polymer characteristics of each were measured. κ / ηιηη / ζζηζ / Ε / γίΛΐ Table 1: Composition and characteristics of ionomer polymers in the example and comparative mixtures κ / ηίηη / ζζηζ / E / γίΛΐ Acid ionomer or copolymer Melting index (dg / min) Initial acid level (% by weight) Neutralization percentage (%) Ion type Thermonomer of BA* (% by weight) Ionomer 1 1.3 10 55 Sodium 4 Ionomer 2 0.8 15 56 Sodium 0 Ionomer 3 3.5 15 27 Sodium 0 Acid copolymer A 10 9 0 none 0 Table 2: Composition and characteristics of LDPE polymers in the example and comparative blends Samples melting index (dg / min) MWD (Mw / Mn, Conv.) Density (g / cm3) AGILITY™ EC 7000 3.9 8.82 0.919 Dow LDPE 5005 5.7 9.29 0.922 AGILITY™ EC 7030 2.5 8.97 0.918 Dow LDPE 722 8.0 10.81 0.918 Dow LDPE 4016 16 9.54 0.919 Dow LDPE 4010 10 >11.0 0.917 Dow LDPE 6211 2.3 >11.0 0.918 Examples 1 to 6 and Comparative Examples C1 to C22 were prepared by dry-mixing the LDPE and the acid ionomer or copolymer first with a drum mixer, and then feeding the mixture into the extruder hopper for the extrusion coating process. Example 1 was a polymer blend prepared from 95% by weight of AGILITY™ EC 7000 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 1 manufactured by Dow Inc. as the sodium-neutralized ionomer copolymer. Example 2 was a polymer blend prepared from 95 wt% LDPE 5005 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 1 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Example 3 was a polymer blend prepared from 95 wt% AGILITY™ EC 7030 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 1 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Example 4 was a polymer blend prepared from 95 wt% AGILITY™ EC 7000 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 2 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Example 5 was a polymer blend prepared from 95 wt% LDPE 5005 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 2 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Example 6 was a polymer blend prepared from 95 wt% AGILITY™ EC 7030 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 2 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example Cl was a polymer blend prepared from 95 wt% LDPE 6211 manufactured by Dow Inc. as the LDPE component and 5% ionomer 1 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C2 was a polymer blend prepared from 95 wt% LDPE 5005 manufactured by Dow Inc. as the LDPE component and 5% ionomer 3 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C3 was a polymer blend prepared from 95 wt% LDPE 722 manufactured by Dow Inc. as the LDPE component and 5% ionomer 3 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C4 was a polymer blend prepared from 95 wt% LDPE 4016 manufactured by Dow Inc. as the LDPE component and 5% ionomer 3 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C5 was a polymer blend prepared from 95 wt% LDPE 4010 manufactured by Dow Inc. as the LDPE component and 5% ionomer 3 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C6 was a polymer blend prepared from 95 wt% LDPE 6211 manufactured by Dow Inc. as the LDPE component and 5% ionomer 3 κ / ηίηη / ζζηζ / E / γίΛΐ manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C7 was a polymer blend prepared from 95 wt% LDPE 722 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 2 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C8 was a polymer blend prepared from 95 wt% LDPE 4016 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 2 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C9 was a polymer blend prepared from 95 wt% LDPE 6211 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 2 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. The Comparative Example CIO was a polymer blend prepared from 95 wt% LDPE 722 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 1 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example Cll was a polymer blend prepared from 95 wt% LDPE 4016 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 1 κ / ηίηη / ζζηζ / E / γίΛΐ manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C12 was a polymer blend prepared from 95 wt% LDPE 4010 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 1 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C13 was a polymer blend prepared from 95 wt% of AGILITY™ EC 7000 manufactured by Dow Inc. as the LDPE component and 5% of Ionomer 3 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C14 was a polymer blend prepared from 95 wt% of AGILITY™ EC 7030 manufactured by Dow Inc. as the LDPE component and 5% of Ionomer 3 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C15 was a polymer blend prepared from 95 wt% LDPE 4010 manufactured by Dow Inc. as the LDPE component and 5% Ionomer 2 manufactured by Dow Inc. as the neutralized sodium ionomer copolymer. Comparative Example C16 was a polymer blend prepared from 95 wt% AGILITY™ EC 7000 manufactured by Dow Inc. as the LDPE component and 5% of Acid A Copolymer manufactured by Dow Inc. Comparative Example C17 was a polymer blend prepared from 95 wt% LDPE 5005 manufactured by Dow Inc. as the LDPE component and 5% Acid Copolymer A manufactured by Dow Inc. Comparative Example C18 was a polymer blend prepared from 95 wt% LDPE 722 manufactured by Dow Inc. as the LDPE component and 5% Acid Copolymer A manufactured by Dow Inc. Comparative Example C19 was a polymer blend prepared from 95 wt% LDPE 4016 manufactured by Dow Inc. as the LDPE component and 5% Acid Copolymer A manufactured by Dow Inc. Comparative Example C20 was a polymer blend prepared from 95 wt% LDPE 4010 manufactured by Dow Inc. as the LDPE component and 5% Acid Copolymer A manufactured by Dow Inc. Comparative Example C21 was a polymer blend prepared from 95 wt% AGILITY™ EC 7030 manufactured by Dow Inc. as the LDPE component and 5% Acid Copolymer A manufactured by Dow Inc. Comparative Example C22 was a polymer blend prepared from 95 wt% LDPE 5005 6211 manufactured by Dow Inc. as the LDPE component and 5% Acid Copolymer A manufactured by Dow Inc. κ / ηίηη / ζζηζ / Ε / γίΛΐ The characteristics of each of the polymer blends and the comparator polymers are summarized in Tables 1-5. The polymers were evaluated using the methods described above. Table 3: Increased heat resistance and improved peel resistance κ / ηίηη / ζζηζ / E / γίΛΐ Average improvement in hot bond strength (N / in) Improvement in peel strength (%) Example 1 2.7 242 Example 2 1.2 348 Example 3 4.1 39 Example 4 2.7 207 Example 5 1.1 426 Example 6 3.6 103 Comparative C1 Not applicable* Comparative C2 0.5 171 Comparative C3 0.4 36 Comparative C4 0.8 5 Comparative C5 0.4 0 Comparative C6 Not applicable* Comparative C7 0.2 411 Comparative C8 0.0 87 Comparative C9 Not applicable* Comparative C10 0.9 126 Comparative C11 1.4 78 Comparative C12 1.1 0 Comparative C13 1.1 100 Comparative C14 1.4 18 Comparative C15 1.6 1 Comparative C16 0.0 94 Comparative C17 0.0 11 Comparative C18 0.3 42 Comparative C19 0.3 183 Comparative C20 0.2 0 Comparative C21 0.0 34 Comparative C22 Not processable* *The mixture cannot be processed on the extrusion coating line with a line speed of 440 ft / min. (Manufacturing methods were described previously) The calculations to determine the improvement in N / in and the percentage improvement in peel strength and the improvement in hot adhesion were described previously. Table 4: Hot bond strength of example polymer blends κ / ηίηη / ζζηζ / E / γίΛΐ Example Hot Bond Strength (N / in) 100°C 110°c 120°C 130°C 140°C 150°C 160°C AGILITY™ EC 7000 0.070 0.797 6.65 7.11 6.77 6.30 5.72 LDPE 5005 0.100 0.353 8.00 7.60 7.98 8.53 7.64 LDPE 722 0.176 0.427 8.27 8.98 9.24 7.70 6.46 LDPE 4016 0.167 0.939 10.53 9.28 7.90 7.09 6.66 LDPE 4010 0.0867 1.83 8.90 8.37 7.62 6.82 6.45 AGILITY™ EC 7030 0.0567 2.60 5.05 5.23 5.23 5.32 4.27 Example 1 0.107 5.42 8.02 9.87 10.03 9.68 8.40 Example 2 0.126 0.198 8.61 9.43 10.27 9.32 8.12 Example 3 0.067 5.58 7.71 8.90 10.06 9.57 9.57 Example 4 0.155 0.898 9.03 9.06 9.94 10.14 8.93 Example 5 0.0833 0.163 9.11 10.22 9.69 8.38 7.61 Example 6 0.093 3.01 7.20 9.87 9.77 8.79 7.85 Comp. C1 -Not processable* — - - - - — Comp. C2 0.151 0.202 7.76 8.91 9.40 8.65 7.70 Comp. C3 0.107 3.81 9.54 10.11 8.68 7.05 7.18 Comp. C4 0.167 3.59 11.63 9.91 8.83 8.10 6.94 Comp. C5 0.073 4.21 9.32 8.85 7.99 7.31 6.79 Comp. C6 -Not actionable* — - - - - — Comp. C7 0.152 1.07 8.98 9.24 8.58 7.93 7.13 Comp. C8 0.090 5.02 12.11 9.01 7.24 6.74 6.51 Comp. C10 0.090 2.43 10.34 10.53 9.23 8.08 7.19 Comp. C11 0.174 1.10 12.53 10.37 9.02 8.81 7.73 Comp. C12 0.187 1.32 9.55 9.31 9.32 8.55 7.00 Comp. C13 0.077 4.16 7.53 7.74 7.62 7.89 7.23 Comp. C14 0.103 2.41 5.96 6.77 7.07 6.38 6.23 Comp. C15 0.157 4.06 10.36 10.05 8.81 8.74 8.01 Comp. C16 0.093 3.20 6.18 7.21 6.83 6.53 5.98 Comp. C17 0.158 0.141 7.50 7.62 7.97 8.15 6.85 Comp. C18 0.169 0.611 9.05 9.18 8.86 8.13 7.13 Comp. C19 0.165 0.875 11.48 9.944 8.13 7.26 6.08 Comp. C20 0.077 4.00 8.22 8.82 8.06 7.27 6.92 Comp. C21 0.103 2.38 4.57 4.86 5.53 4.88 4.60 Comp. C22 No procesable* — - - - - —. Figure 1, a graph of hot bond strength as a function of sealing bar temperatures, shows that Example 3 has a higher hot bond strength than the AGILITY™ EC 7030 comparator. The results in Figure 1 illustrate that the blend of an ionomer and an LDPE polymer has a higher hot bond strength than an LDPE resin. Table 5: Peel resistance data for example polymer blends Example Peel Strength (N / in) AGILITY™ EC 7000 Maximum Load 1.14 Average Load 0.625 LDPE 5005 Maximum Load 0.468 Average Load 0.197 LDPE 722 Maximum Load 0.402 Average Load 0.196 LDPE 4016 Maximum Load 0.343 Average Load 0.0674 LDPE 4010 Maximum Load 0.417 Average Load 0.0628 AGILITY™ EC 7030 Maximum Load 2.29 Average Load 1.55 Example 1 Maximum Load 3.92 Average Load 3.32 Example 2 Maximum Load 2.10 Average Load 1.52 Example 3 Maximum Load 3.18 Average Load 2.71 Example 4 Maximum Load 3.53 Average Load 2.92 Example 5 Maximum Load 2.46 Average Load 1.79 Example 6 Maximum load 4.66 Average load 2.42 Comp. C1 Maximum load Not processable* Average load — Comp. C2 Maximum load 1.27 Average load 0.814 Comp. C3 Maximum load 0.548 Average load 0.255 Comp. C4 Maximum load 0.362 Average load 0.136 Comp. C5 Maximum load 0.389 Average load 0.173 Comp. C6 Maximum load Not processable* Average load — Comp. C7 Maximum load 2.05 Average load 1.53 Comp. C8 Maximum load 0.640 Average load 0.326 Comp. C10 Maximum load 0.910 Average load 0.514 Comp. C11 Maximum load 0.611 Average load 0.220 Comp. C12 Maximum load 0.387 Average load 0.157 Comp. C13 Maximum load 2.30 Average load 1.69 Comp. C14 Maximum load 2.71 Average load 2.00 Comp. C15 Maximum load 0.420 Average load 0.200 Comp. C16 Maximum load 2.23 Average load 1.72 Comp. C17 Maximum load 0.519 Average load 0.251 Comp. C18 Maximum load 0.570 Average load 0.205 Comp. C19 Maximum load 0.971 Average load 0.411 Comp. C20 Maximum load 0.369 Average load 0.138 Comp. C21 Maximum load 3.07 Average load 2.57 Comp. C22 Maximum load Not processable* Average load — It is noted that with regard to this date, the method known to the applicant to carry out the aforementioned invention is the one that is clear from the description of the invention.

Claims

1. A polymer mixture, characterized in that it comprises: at least 90% by weight of low-density polyethylene (LDPE) polymer, wherein the LDPE polymer has a melt index (I2) of 2 to 6 g / 10 min as determined according to ASTM D1238 (190 °C, 2.16 kg, Procedure B), and a molecular weight distribution (MWD = Mw / Mn) of 5 to 11 as determined by a conventional gel permeation chromatography method; and from 1% by weight to 10% by weight of ionomer, wherein the ionomer comprises an ethylene and acid copolymer having from 15% to 70% of the carboxylic acid groups neutralized as carboxylic acid salts comprising sodium cations depending on the total amount of acid groups in the polymer, wherein the ethylene and acid copolymer is the polymerized reaction product of: at least 50% by weight of ethylene, depending on the total weight % of monomers present in the ethylene and acid copolymer;from 2% by weight to 30% by weight of monocarboxylic acid monomer, depending on the total weight % of monomers present in the ethylene and acid copolymer; and from 0% by weight to 25% by weight of alkyl acrylate, depending on the total weight % of monomers present in the ethylene and acid copolymer.

2. The polymer mixture according to claim 1, characterized in that the LDPE has a density of 0.910 g / cc to 0.930 g / cc and a conventional molecular weight distribution of 8.5 to 11.

3. The polymer mixture according to claim 1, characterized in that the LDPE has a melting index I2 of 2 g / 10 min to 4.5 g / 10 min.

4. The polymer mixture according to claim 1, characterized in that the ionomer has a melting index (I3) of 0.5 g / 10 min to 15 g / 10 min.

5. The polymer mixture according to claim 1, characterized in that the ionomer has a melting index (I2) of 0.5 g / 10 min to 4 g / 10 min.

6. The polymer mixture according to claim 1, characterized in that it comprises from 1% by weight to 5% by weight of the ionomer.

7. The polymer mixture according to claim 1, characterized in that the ionomer has from 40% to 60% acid groups neutralized by a sodium cation depending on the total amount of acid groups.

8. The polymer mixture according to claim 1, characterized in that the ethylene and acid copolymer comprises at least 70% by weight of ethylene, and from 8% by weight to 25% by weight of monocarboxylic acid monomer.

9. The polymer mixture according to claim 1, characterized in that the ethylene and acid copolymer comprises at least 70% by weight of ethylene, and from 8% by weight to 20% by weight of monocarboxylic acid monomer.

10. The polymer mixture according to claim 1, characterized in that the alkyl acrylate comprises methyl acrylate, ethyl acrylate, n-butyl acrylate or isobutyl acrylate, or combinations thereof, and the monocarboxylic acid monomer comprises one or more of acrylic acid, methacrylic acid or combinations thereof.

11. A coated substrate, characterized in that it comprises: a substrate; and a coating comprising the polymer mixture according to any preceding claim adhered to the substrate.

12. The coated substrate according to claim 11, characterized in that it comprises a metallic substrate, a paper substrate, or a polymer substrate.

13. The coated substrate according to claim 12, characterized in that the polymer substrate comprises polyester or metallized polyester.

14. The coated substrate according to claim 12, characterized in that the polymer substrate is metallized.

15. The coated substrate according to claim 12, characterized in that the polymer substrate is polypropylene, polyethylene, metallized polypropylene or metallized polyethylene.

16. The coated substrate according to claim 11, characterized in that it has a maximum hot bond strength of at least 9.5 N / in within a sealing bar temperature range of 120 °C to 160 °C, as measured by ASTM F-1921 (Method B).

17. The coated substrate according to claim 11, characterized in that the coating has a maximum load peel strength of at least 2 N / in, as measured by the peel test.

18. A film, characterized in that it comprises the polymer mixture according to claim 1.