Multilayer polymeric foam films for packaging applications and methods for making same

Abstract

A multi-layer foamed film suitable for direct and non-direct food contact and aseptic packaging applications and a method of making said film are disclosed. The multi-layer foamed film includes a foam layer containing a plurality of cells, where at least 10% of the cells are closed cells, and two solid skin layers including HDPE on each side of the foam layer, and a solid layer including ethylene vinyl alcohol (EVOH), where the foam layer is between one of the solid skin layers and the solid layer including EVOH, the film has an overall thickness of 8 mils or greater, and the creased, folded or scored film has a cc / m2 density according to ASTM D3985. 2 The ratio of the oxygen transmission rate at 100 / 24 ​​hr to the oxygen transmission rate of the same film before creasing, folding or scoring is less than 1.1.

Description

[Technical field]

[0001] Field The present invention relates to multi-layer polymeric foam films (eg, containing high density polyethylene (HDPE)) that can be used for paper replacement applications in the aseptic packaging industry. [Background technology]

[0002] background Paperboard usage for packaging applications accounts for approximately one-third of the total packaging market. In direct food contact packaging, paperboard functions safely with some form of barrier coating. Traditionally, in food packaging applications where barrier properties are essential, paperboard is paraffin wax coated or laminated with a polymer film, usually polyethylene. For shelf-stable products that are stored at room temperature and where the packaging is aseptically sealed followed by hermetic sealing, oxygen barrier properties are essential. The advent of paper-foil-plastic laminate containers, such as Tetrahedron in 1959, was an inflection point in the packaging industry where it could replace metal cans and glass containers. Thus, typically, a layer of metalized polymer or aluminum film is incorporated into the structure of the paperboard. This can cause significant recycling problems, as the majority of recycling facilities lack the infrastructure that can provide specific recycling technologies.

[0003] For example, there has been an accumulative popularity and interest in aseptically packaged sterilized and pasteurized products, such as milk, baby food, tomato products, broths, soups, vegetables, desserts, liquid eggs, yogurt, dressings, etc., that eliminate refrigeration and prevent spoilage without the use of preservatives. Therefore, with the enormous and growing demand for food packaging in emerging markets, it is desirable to produce lightweight, recyclable polymeric films with improved oxygen and moisture barrier properties that possess surface quality for printing and preprinting shelf life, bending stiffness values ​​comparable to paperboard used in packaging, and sufficient barrier properties, all of which may be essential properties for a product to replace the types of paperboard currently used in the packaging industry. Furthermore, the above-mentioned products can address the wicking issue of coated paperboard.

[0004] One of the most important problems during the production of flexible sterile packaging products made of multilayer sheets or films is package defects due to the occurrence of any form of physical damage to the sheets, and especially to the oxygen barrier layer, in the form of microcracks that can be initiated and then propagated during the process of creasing, scoring, piercing, punching, or folding. For example, these cracks typically occur in the aluminum layer, metallized layer, or even ethylene vinyl alcohol (EVOH) layer that are traditionally included in the structure of multilayer sheets and films currently used in the packaging industry. These defects can deteriorate the integrity of the oxygen barrier properties of the entire package, resulting in a reduced shelf life of the product. Therefore, it is beneficial to innovate a method to protect the barrier layer in the multilayer sheet or film from being physically damaged when undergoing the above processes. Summary of the Invention

[0005] overview For example, described herein are multi-layer polymeric foam films that can be used in aseptic packaging applications. As further described below, in some embodiments, the multilayer films retain their oxygen transmission rate (OTR) properties after a creasing, folding or scoring process. That is, the creasing, folding or scoring multilayer film has an OTR similar to that of the same multilayer film before creasing, folding or scoring. This can be advantageous over conventional multilayer films that may experience an increase in OTR, for example, as a result of physical damage during creasing, folding or scoring. In some embodiments, the films can have a very smooth surface that provides excellent print quality and bending stiffness high enough to replace paperboard. The films can be recyclable and lightweight.

[0006] In one aspect, a creased, folded, or scored multi-layer foam film is provided. The film includes a foam layer containing a plurality of cells. At least 10% of the cells are closed cells. The film further includes two solid skin layers including HDPE on each side of the foam layer. The film further includes a solid layer including ethylene vinyl alcohol (EVOH). The foam layer is between one of the solid skin layers and the solid layer including EVOH. The film has an overall thickness of 8 mils or greater. The creased, folded, or scored film has a cc / m2 by ASTM D3985. 2 The ratio of the oxygen transmission rate at 100 / 24 ​​hr to the oxygen transmission rate of the same film before creasing, folding, or scoring is less than 1.1.

[0007] In another aspect, a method of making a creased, folded, or scored multilayer film is provided. The method includes co-extruding a foam layer, two solid skin layers including HDPE, and one solid layer including ethylene vinyl alcohol (EVOH) to form a multilayer film. The foam layer contains a plurality of cells, where at least 10% of the cells are closed cells. The foam layer is between one of the solid skin layers and the layer including EVOH. The film has an overall thickness of 8 mils or greater. The method further includes creasing, folding, or scoring the multilayer film. The creased, folded, or scored film is measured for cc / m according to ASTM D3985. 2 Oxygen transmission rates at 1000 / day are measured in cc / m3 per ASTM D3985 for multilayer films before creasing, folding, or scoring. 2 / day does not increase oxygen transmission rate by more than 10%. Other aspects, features, advantages and features will become apparent from the following detailed description.

[0008] Detailed Description The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. All ranges disclosed herein are inclusive of the recited endpoints and are independently combinable (e.g., a range of bending stiffness in the Taber unit construction of "18 to 100" includes the endpoints 18 and 100, and all intermediate values. In the same context, for example, an overall thickness of greater than 8 mm includes the endpoint 8 mm.)

[0009] As used herein, approximation may be applied to modify any quantitative indication that may be altered without resulting in a change in the basic function to which it pertains. As a result, a value modified by a term(s) such as "about" and "substantially" may not be limited to a precise specific value. The modifier "about" should also be considered as disclosing a range defined by the absolute values ​​of the two endpoints. For example, the expression "about 0.05 to about 15" also discloses the range "0.05 to 15".

[0010] As used herein, the term "lightweight" refers to the bulk density values ​​of the products described herein being less than or equal to the density of their solid counterparts made from the relevant base virgin resin, or the density of the relevant base virgin resin. In a similar context, it also refers to the bulk density values ​​of the products described herein being less than or equal to the density of their solid counterparts made from the relevant base virgin resin, or the density of the relevant base virgin resin. 2 For example, the bulk density value of the product of the present invention is 0.962 gr / cm 3 or its solid counterpart made from the relevant base raw resin is less than the density value of 0.962 gr / cm 3 The bulk density value is less than 0.962gr / cm 3 It may be less than.

[0011] The present disclosure relates to packaging including multi-layer lightweight polyethylene foam film suitable for use in all kinds of aseptic packaging; packaging of all kinds of oxygen sensitive products; packaging of pasteurized products; packaging of dry food products such as biscuits, cookies, cereals, tea, coffee, sugar, flour, dry food mixes, chocolates, confectionery, pet food, etc.; packaging of frozen foods such as chilled foods and ice cream; packaging of cooked and precooked products and foods; backing board for fresh products such as vegetables, fruits, meat and fish; packaging of baby foods; packaging of all kinds of desserts; packaging of liquid foods and beverages such as broths, soups, juice drinks, all kinds of milk and milk derived products, concentrates, all kinds of dressings, liquid eggs, tomato products, etc.; and packaging of laundry detergents, shampoos, and body washes; making all kinds of pouches including SUP, sachets; and packaging of pet foods. The above examples are not intended to limit the uses of the products of the present disclosure in any way, and other uses are possible.

[0012] One of the rationales behind the production of the synthetic lightweight films described herein and the material selection for replacing paperboard is to address recyclability and avoid the drawbacks of using wax coated paperboard, metallized films, and films and sheets with aluminum layers, all of which are not or are not easily recyclable; although, in practice, the majority of consumers intuitively believe that such products, such as aseptically packaged milk boxes or long-life beverage boxes, are recyclable.

[0013] Disclosed herein is a recyclable lightweight multilayer film that includes at least 5 layers, such as 7 layers, in some embodiments, to be a replacement for paperboard used in the packaging industry, for example, for aseptic packaging applications, and for direct and non-direct food contact packaging applications. The film includes high density polyethylene (HDPE), where at least one layer, except for the solid skin layer, has a cellular structure. In some embodiments, at least 10% of the cells are closed cells; in some embodiments, more than 50% of the cells are closed cells; and in some embodiments, more than 75% of the cells are closed cells. In some embodiments, 100% of the cells are closed cells. As used herein, "closed cells" refers to cells that have cell walls that completely surround the cells, without openings, such that there is no interconnectivity to adjacent cells. In some embodiments, the film includes at least one solid layer containing EVOH, where each solid layer is located somewhere between a foam layer and a solid layer, or between two solid layers. In some embodiments, the film comprises at least one foam layer and two solid skin layers, and one or more solid layers comprising EVOH, where the foam layer is located between the skin layer and the layer comprising EVOH.

[0014] In some embodiments, the mass concentration of EVOH in every unit area of ​​the multilayer film is less than 5 percent of the mass of the unit area of ​​the film. In some embodiments, the mass concentration of EVOH in every unit area of ​​the multilayer film is less than 10 percent of the mass of the unit area of ​​the film. In some embodiments, the mass concentration of EVOH in every unit area of ​​the multilayer film is less than 5 percent of the mass of the unit area of ​​the film. In some other embodiments, the mass concentration of EVOH in every unit area of ​​the multilayer film is less than 2 percent of the mass of the unit area of ​​the film.

[0015] Furthermore, in some embodiments, the bending stiffness of the disclosed multilayer foamed film products can be improved over their solid counterparts to meet the property requirements in the packaging industry. This can be done primarily and exclusively by including one or more cell layers in the core of the multilayer film or between two solid skin layers, by precisely adjusting and modifying the thickness of the cell layers, and by fine-tuning the thickness of the solid skin layers. In general, at the same thickness, a solid film of polyethylene can hardly possess the bending stiffness value that paperboard can provide. This is due to the high degree of fiber alignment of paperboard, which can significantly enhance bending stiffness. In addition, it can be due to the higher inherent stiffness of individual fibers in paperboard compared to the polymer chains in polymer film.

[0016] Generally, HDPE has a viscosity of about 0.3 to 0.5 (g / 100 in 2 / 24hr)。 Embodiments of the multilayer foam film products described herein can exhibit significantly higher moisture barrier properties compared to their solid counterparts having the same value of mass per unit area (grams / square meter). Also, embodiments of the multilayer foam film products described herein can exhibit enhanced oxygen barrier properties.

[0017] One of the problems in industrial-scale use of polymer packages, which can also be a key factor in efficient and cost-effective packaging processes, is their ability to be de-nested quickly and freely. Denesting problems are typically caused by friction and static charges. The multilayer foam film embodiments described herein can exhibit antistatic and low friction behavior by manipulating the structure of the skin layer and by including appropriate amounts of slip agents, antiblocking agents and antistatic agents in the solid skin layer.

[0018] In some embodiments, one of the steps for making the disclosed product is the inclusion and control of the thickness of the core cell layer, or the cell layer between two skin layers, and the means of controlling and enhancing bending stiffness by fine-tuning the solid skin, as well as the means of significantly improving surface smoothness by adding a trace amount of supercritical expansion agent.Furthermore, how the unique structure and layer combination results in high barrier properties without the inclusion of aluminum or metallized barrier layers.That is, the film product can be free of any metal (e.g., aluminum) barrier layers.

[0019] In some embodiments, a blown film process may be used, where the extruder head pressure can be increased due to the extremely narrow gap that aids in the nucleation of cells in the foam layer. Using such techniques, melt fracture should be avoided, and the resin should have good thermal stability and sufficiently high melt strength. Typically, film manufacturers utilize blends of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE), while the blends are often immiscible blends, where LDPE improves processability and ductility, while LLDPE can enhance elasticity and strength. In some embodiments, all layers of the multilayer film described include HDPE, and in some cases, the polymeric material in one or more of these layers consists essentially of HDPE, and in some cases, the polymeric material in at least one of the solid layers, except for the solid skin layer, includes EVOH. In one embodiment, at least one layer of the multilayer film may include LDPE.

[0020] In some embodiments, the multilayer film can include 9 layers; in some embodiments, 7 layers; and in some embodiments, 5 layers. For example, a five-layer film may include a foamed core layer (e.g., including HDPE), and at least two solid layers (e.g., including HDPE), one on each side of the core layer, and at least one solid layer (e.g., including EVOH), one between the foamed layer and the solid skin layer. In one embodiment, a five-layer film may include a solid core layer (e.g., including EVOH), and at least two solid layers (e.g., including HDPE), one on each side of the core layer, and at least two foamed layers (e.g., including HDPE), one between the foamed layer and the solid skin layer. In some embodiments, the five-layer film may have a layer structure ABCBA (i.e., layer A is the outermost two (skin) layers, layer B is in contact with layer A and layer C, respectively, and layer C is the middle layer). For example, layer A may be a solid skin layer (e.g., including HDPE), layer B may be a foam layer (e.g., including HDPE), and layer C may be an EVOH (e.g., solid) layer.

[0021] In one case, the seven-layer foamed film comprises a foamed core layer (e.g., including HDPE) in the center, with two solid skin layers (e.g., including HDPE) on each side of the core layer, and at least one solid layer (e.g., including EVOH) between the foamed layer and the solid skin layer. In another case, the seven-layer foamed film comprises a solid core layer (e.g., including EVOH) in the center, with two solid skin layers (e.g., including HDPE) on each side of the core layer, and at least one foam layer (e.g., including HDPE) between the solid core layer and the solid skin layer. In some embodiments, the seven-layer film may have a layer structure ABCDCBA (i.e., layer A is the two outermost (skin) layers, layer B contacts each A layer and each C layer, layer C contacts each B layer and layer D, and layer D is the central layer). For example, Layer A may be a solid skin layer (e.g., comprising HDPE), Layer B may be a foam layer (e.g., comprising HDPE), Layer C may be a solid tie layer (e.g., comprising HDPE), and Layer D may be an EVOH (e.g., solid) layer.

[0022] In another embodiment, the nine-layer foamed film comprises a central foamed core layer (e.g., comprising HDPE) with two solid skin layers (e.g., comprising HDPE) on each side of the core layer, and at least one solid layer (e.g., comprising EVOH) between the foamed layer and the solid skin layer. In another embodiment, the nine-layer foamed film comprises a central solid core layer (e.g., comprising EVOH) with two solid skin layers (e.g., comprising HDPE) on each side of the core layer, and at least one foam layer (e.g., comprising HDPE) between the solid core layer and the solid skin layer. In some embodiments, the nine-layer film may have a layer structure ABCDEDCBA (i.e., layer A is the outermost two (skin) layers, layer B contacts each A layer and each C layer, layer C contacts each B layer and each D layer, layer D contacts each C layer and layer E, and layer E is the middle layer). For example, Layer A may be a solid skin layer (e.g., comprising HDPE), Layer B may be a solid tie layer (e.g., comprising HDPE), Layer C may be a (e.g., solid) EVOH layer, Layer D may be a solid tie layer (e.g., comprising HDPE), and Layer E may be a foam layer (e.g., comprising HDPE).

[0023] In another embodiment, the multilayer film, which may be 5, 7, or 9 layers, includes at least one foamed layer and two solid skin layers, and at least one solid layer (e.g., comprising EVOH). In another embodiment, the multilayer film, which may be 5, 7, or 9 layers, includes at least one solid layer comprising EVOH, each of which is located between the foamed layer and the solid layer, or between two solid layers. In some embodiments, the multilayer films described herein include multiple layers, e.g., 3 to 19 layers, including at least one foamed layer and one or more solid layers containing EVOH. In some other embodiments, the multilayer films described herein include multiple layers, e.g., 3 to 19 layers, including at least one solid layer containing EVOH. It should be understood that other layer configurations are possible.

[0024] In one embodiment, the process for producing the described multilayer film may utilize very small and precise amounts, e.g., less than 0.1 wt%, of supercritical gas as a processing aid and blowing agent. In some embodiments, other gas concentrations, e.g., greater than 0.1 weight percent, are possible. Such supercritical gas may be injected into the molten polymer at high pressures, e.g., greater than 34 bar, inside an efficient and effective mixer, e.g., a cavity transfer mixer, as an extension of the barrel of the extruder. The supercritical blowing agent used in the process can be either nitrogen, carbon dioxide, or a mixture of nitrogen and carbon dioxide. In some embodiments, the supercritical blowing agent is Gas can be introduced into the mixing section of the extruder at injection pressures of 34 bar or more; in some cases 70 bar or more; in some cases 240 bar or more, and in some cases 380 bar or more. The temperature of the mixer can be precisely controlled within ±1°C. The inclusion of small amounts of gas can provide several important advantages in the process and, for example, in blown film extrusion processes. For example, the gas can reduce the back pressure, which allows processing at a higher throughput and can spare any bubble instabilities. Thus, melt fracture could be significantly reduced. The gas can also enhance the processing ability of HDPE and act as a physical blowing agent due to the presence of a nucleating agent in the layer with a cellular structure. The addition of a physical blowing agent can suppress the occurrence of melt fracture due to the manipulation of the viscosity of the melt, which can lead to a high surface smoothness. Hence, the quality of the print on the film can be significantly improved.

[0025] Generally, conventional polymer processing equipment may be used to produce the films described herein. In some cases, for example, the films may be produced by a blown film process using an annular die with a die gap of 0.45-1.3 mm and a blow-up ratio ranging from 1.5:1 to 3.5:1. A higher blow-up ratio may result in a more balanced MD / TD (machine direction / transverse direction) orientation, which improves overall film toughness. The die geometry and specifications may be manufactured according to, for example, patent application US2012 / 0228793A1, the entirety of which is incorporated herein by reference.

[0026] The majority of conventional PE blown films are processed using blends of PE, including LDPE, to enhance bubble stability. Almost all HDPE films are made in a high stock blown film process; otherwise, the tear strength of HDPE films is significantly reduced. As described above, in an embodiment of the method used to produce multilayer films, supercritical gas may be injected into the melt at a precisely controlled rate inside the transfer mixer before entering the annular die. This unit could be controlled as separate temperature sections with an accuracy of ±1°C and gas injection pressure fluctuations of less than 1%. The plasticizing effect of the gas could result in a change in the viscosity of the molten resin, which would enhance the processability of the resin inside the annular die at lower temperatures compared to the processing temperatures traditionally used. Thus, a relatively stable bubble could be created inside the pocket. Then, due to the overall high specific heat capacity of polyethylene, the transverse extension of the bubble could be delayed until the film is cooled, further enhancing the stability of the bubble and the height of the frost line. This may also be beneficial in manipulating the crystallization kinetics of the skin layer to improve some other physical and mechanical properties: a higher degree of crystallinity in the skin may reduce the coefficient of friction of the skin layer. In some embodiments, the multilayer foamed films described herein may be produced by a blown film process, a cast film process, or other suitable methods.

[0027] In some embodiments, the polymeric composition of each layer contains some amount of other additives, such as pigments, slip agents, antistatic agents, UV stabilizers, antioxidants, nucleating agents, clarifying agents, or maleic anhydride. The foamed layer may optionally contain 0.05 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent. In some embodiments, the foamed layer may optionally contain 0.05 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent. In some embodiments, the foamed layer may optionally contain 1 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent. In some embodiments, the foamed layer may optionally contain 2.5 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent. In some embodiments, the foamed layer may optionally contain 5 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent. In some embodiments, the foam layer may optionally contain 7.5 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent. In some embodiments, the foam layer may optionally contain 10 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent. In some embodiments, the foam layer may optionally contain 12.5 to 15 weight percent of an inorganic additive, an organic additive, or a mixture of inorganic and organic additives as a nucleating agent.

[0028] For example, the foam layer may contain up to about 15% by weight of talc as a nucleating agent. In some embodiments, at least one layer may include less than 1 weight percent of a clarifying agent, such as less than 0.5 weight percent, such as less than 0.1 weight percent, such as less than 0.05 weight percent. In some cases, at least one layer of the film may contain up to about 35% by weight of calcium carbonate. In some cases, at least one layer of the film may contain up to about 30% by weight of calcium carbonate. In some cases, at least one layer of the film may contain up to about 25% by weight of calcium carbonate. In some cases, at least one layer of the film may contain up to about 20% by weight of calcium carbonate. In some cases, at least one layer of the film may contain up to about 15% by weight of calcium carbonate.

[0029] In some embodiments, at least one layer of a film described herein comprises less than 5 weight percent maleic anhydride, such as less than about 4 weight percent, such as less than about 3 weight percent, such as less than about 2.5 weight percent, such as less than about 2 weight percent, such as less than about 1 weight percent. In some cases, the multilayer foamed film can include two solid skin layers, where one of the skin layers contains a suitable amount, such as less than 1 weight percent, such as less than 0.75 weight percent, such as less than 0.5 weight percent, of black pigment, and the other solid skin layer contains a suitable amount, such as less than 1 weight percent, such as less than 0.75 weight percent, such as less than 0.5 weight percent, of white pigment. In some other embodiments, both solid skin layers contain a suitable amount of white pigment.

[0030] In another case, the solid skin layers of the multilayer foamed film contain less than 0.5 weight percent of an antiblocking agent and / or less than 0.2 weight percent of an antistatic agent. In one embodiment, the multilayer foamed film has at least one solid skin layer having a static coefficient of friction value of less than 0.4, such as less than 0.38. In another embodiment, the film has at least one solid skin layer having a dynamic coefficient of friction value of less than 0.3.

[0031] The described multilayer films comprising at least one foamed layer can have a significantly improved set of physical-mechanical properties compared to known foamed film articles, such as, inter alia, bending stiffness values ​​of greater than 18, in some cases greater than 20, and in some cases greater than 25, in the Taber stiffness unit configuration, according to TAPPI / ANSI T 489 om-15, where the mass per unit area (mass per unit area of ​​the film in grams per square meter (gr / m 2 )) to the stiffness value of the Taber unit constituents is less than or equal to 13, in some cases less than 11, and in some cases less than 10. In one embodiment, the film can have a Taber Flexural Stiffness value of less than 280 according to TAPPI / ANSI T 489 om-15.

[0032] The films described may have a surface with an average Sheffield smoothness according to TAPPI T538 of less than 100. In some embodiments, the films may have an average Sheffield smoothness of less than 50; in some cases, less than 40; in some cases, less than 30; and in some cases, less than 15. The multilayer foamed film may have an overall thickness of greater than 8 mm, in some cases greater than 10 mm, in some cases greater than 13 mm, and in some cases greater than 15 mm. In some embodiments, the lightweight films described herein have a coating density of 1 gr / cm 3 Less than 0.962 gr / cm in some cases 3 Less than 0.94 gr / cm in some cases 3 in some cases less than 0.9 gr / cm 3 Less than 0.85 gr / cm 3and in some cases, less than 0.8 gr / cm 3 has a bulk density of less than

[0033] In some embodiments, the foam layer of the disclosed films has, compared to known films, a uniformly distributed cell, e.g., closed cell morphology, and an average cell size of about 10-250 μm, e.g., 50-250 μm, e.g., 150-250 μm, e.g., 200-250 μm; 2 ~10 9 Cells / cm 3 The foam layer may have a much better cell morphology, having an average cell density relative to the unfoamed polymer volume of 100% and a foam layer expansion ratio of 1-9, e.g., a foam layer expansion ratio of 1-8, e.g., a foam layer expansion ratio of 1-7, e.g., a foam layer expansion ratio of 1-6, e.g., a foam layer expansion ratio of 1-5, e.g., a foam layer expansion ratio of 1-4, e.g., a foam layer expansion ratio of 1-3, e.g., a foam layer expansion ratio of 1-2. In some cases, the foam layer comprises at least 10% closed cells, and in some cases, more than 50% closed cells. In one embodiment, the foam layer has substantially full closed cell morphology (e.g., more than 95% closed cells).

[0034] In some embodiments, the multilayer foamed film comprises at least one layer containing a PE / EVOH blend. In some embodiments, the multilayer foamed film described herein comprises at least one layer, excluding the solid skin layer, and contains about 30-50 weight percent EVOH, e.g., about 35-49 weight percent EVOH, e.g., about 40-49 weight percent EVOH, e.g., about 45-49 weight percent EVOH, and less than 5 weight percent, e.g., 2 weight percent maleic anhydride. In some embodiments, the total mass concentration of EVOH in a unit area of ​​the film does not exceed 10 percent of the mass of the unit area of ​​the film. In some embodiments, the total mass concentration of EVOH in a unit area of ​​the film does not exceed 7.5 percent of the mass of the unit area of ​​the film. In some embodiments, the total mass concentration of EVOH in a unit area of ​​the film does not exceed 5 percent of the mass of the unit area of ​​the film. In some embodiments, the total mass concentration of EVOH in a unit area of ​​the film does not exceed 4 percent of the mass of the unit area of ​​the film. In some embodiments, the total mass concentration of EVOH in a unit area of ​​the film does not exceed 3 percent of the mass of the unit area of ​​the film. In some embodiments, the total mass concentration of EVOH in a unit area of ​​the film does not exceed 2.5 percent of the mass of the unit area of ​​the film.

[0035] The films described herein have a hardness rating of 0.05 gr / 100 in per ASTM E398-13. 2 In one case, the film has a water vapor transmission rate of less than 0.1 gr / 100 in. 2 In some embodiments, the water vapor transmission rate of the film is less than 1 gr / m 2 / day. In some embodiments, the films described have a viscosity of 0.65 cc / 100 in by ASTM D3985. 2 / 24hr or 10cc / m 2In some cases, the described films may have an oxygen transmission rate of less than 0.32 cc / 100 in. / 24 hr per ASTM D3985. 2 / 24hr or 5cc / m 2 In some embodiments, the films described can have an oxygen transmission rate of less than 0.13 cc / 100 in / 24 hr according to ASTM D3985. 2 / 24hr, or 2cc / m 2 The oxygen transmission rate may be less than 1 / 24hr.

[0036] In some embodiments, the films described have a viscosity of 0.65 cc / 100 in by ASTM D3985. 2 In another embodiment, the film comprises at least one layer, other than the solid skin layer, that contains ethylene vinyl alcohol (EVOH). In an exemplary embodiment, the multi-layer foamed film, e.g., a five-layer foamed film, has at least one solid skin layer with a static coefficient of friction value of less than 0.4 and / or less than 0.38. In another embodiment, the film, e.g., a five-layer foamed film, has at least one solid skin layer with a dynamic coefficient of friction value of less than 0.3.

[0037] In some embodiments, various thermoplastics such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyamide (PA), LLDPE copolymers including α-olefin comonomers such as butene, hexene, or octene; any resin known as the TPE family, including but not limited to propylene-ethylene copolymers, thermoplastic olefins (TPO), and thermoplastic polyurethanes (TPU), may be used in at least one layer of the multilayer foamed film and blown film process. In some embodiments described herein that include an HDPE layer, some or all of the HDPE layer is replaced by a PP layer in the multilayer structure. In some embodiments described herein that include an HDPE layer, some or all of the HDPE layer is replaced by a PET layer in the multilayer structure.

[0038] In another embodiment, at least one layer of the film (e.g., excluding the outer skin layer) may comprise LDPE, PP, PA, EVOH, EVA, or PVOH. The following examples illustrate the process of the present disclosure. The examples are illustrative only and are not intended to impose any limitations on the present disclosure with respect to the materials, conditions, or processing parameters set forth herein. Disclosed herein is a method for protecting an oxygen barrier layer (e.g., an EVOH layer) in a described multilayer film from acquiring any form of physical damage, such as, for example, microcracks, when the multilayer film undergoes a creasing, scoring, piercing, punching, or folding process. In said method, any oxygen barrier layer is supported on one or both sides by at least one foam layer adjacent to the oxygen barrier layer. In some embodiments, any oxygen barrier layer is supported by at least one foam layer adjacent to the oxygen barrier layer. In some embodiments, any oxygen barrier layer is protected by the inclusion of one foam layer adjacent to either or both skin layers. In some embodiments, the oxygen barrier layer comprises EVOH.

[0039] As used herein, there is provided a method for producing a film comprising the steps of: co-extruding at least one foam layer containing a plurality of cells, where at least 10% of the cells are closed cells; and two solid skin layers comprising HDPE, and one or more solid layers comprising ethylene vinyl alcohol (EVOH), where the foam layer is co-extruded between the skin layer and the layer comprising EVOH, and where the film has an overall thickness of 8 mils or greater; scoring, scoring or folding the film, where the scored, scored or folded film has a cc / m 2 by ASTM D3985. 2Disclosed are methods of making creased, folded, or scored multilayer films (and related products), including that the oxygen transmission rate value at 100 / day does not increase by more than 30% of the OTR value of the same multilayer film that is not creased, scored, or folded (i.e., before creasing, scoring, or folding). In some embodiments, the oxygen transmission rate value of the creased, scored, or folded film does not increase by more than 20%, or more than 10%, or more than 5 ... (cc / m per ASTM D3985) does not increase by more than 20% of the OTR value of the same film that is not creased, scored, or folded (i.e., before creasing, scoring, or folding). 2 The ratio of OTR to OTR (at 24 hr) is less than 1.1, in some cases less than 1.075, in some cases less than 1.05, and in some cases less than 1.025. EXAMPLES

[0040] example All products from the following examples were tested and characterized in terms of bending stiffness, surface smoothness, oxygen transmission rate, water vapor transmission rate, and density. A Taber Stiffness Tester, Model 150-E, from Taber Industries was used to characterize the bending stiffness of the films. The smoothness of the products was evaluated using a Gurley™ 4340 Automated Densometer and Smoothness Tester. The oxygen transmission rate (OTR) of the products was measured using an OX-TRAN 1 / 50 tester from AMETEK MOCON according to ASTM D3985. The water vapor transmission rate (WVTR) of the samples was measured using a PERMATRAN-W Model 1 / 50 G+ tester from AMETEK MOCON according to ASTM E398-13.

[0041] Example 1: Samples of multilayer HDPE films (7 layers) were produced using a Reifenhaeuser Extrusion System 7-layer blown film line consisting of 7 extruders including two 55 mm extruders labeled "A" and "G", two 65 mm extruders labeled "B" and "F", and three 35 mm extruders labeled "C", "D" and "E" with internal bubble cooling system, gauge control, mass throughput control, and layer thickness control for the skins. Both 65 mm extruders were equipped with supercritical gas injection units capable of injecting nitrogen, carbon dioxide, or a mixture of both, as well as two 65 mm MuCell Transfer Mixers (MTM) from MuCell Extrusion LLC. All films were produced by a blown film process using an annular die with die gaps ranging from 0.7 to 1.2 mm and blow-up ratios ranging from 2.8:1 to 3.5:1. The lips of the annular die were boron nitride coated.

[0042] Table 1 contains processing data and characterization results of the products produced as a non-limiting example to elucidate the invention. The sample had a melt index of 0.85 dg / min and 0.962 gr / cm 3 The samples were produced in high density polyethylene ELITE 5960 from Dow Chemical Company, having a density of 0.25 dg / min and 0.921 gr / cm. In all samples, additives, e.g. pigments, were added in the form of masterbatches using LDPE carriers, if necessary. Apparently, additives can be compounded in HDPE carriers. In some samples, only small amounts of 3 LDPE132I from Dow Chemical Company was used, having a density of 1000 .001 mm. Calcium carbonate and talc were prepared and introduced as highly loaded masterbatches of 80 wt% loaded calcium carbonate and 70 wt% loaded talc, respectively, into HDPE as the base carrier resin. All tie layers contain ADMER adhesive resin, which is an anhydride grafted polyolefin. In this example, the middle layer contains ethylene vinyl alcohol (EVOH) with an ethylene content of 32%.

[0043] All samples were coextruded at a total throughput of 300-340 kg / hr as it is listed in Table 1. The temperature of the mixing section where the supercritical gas was injected was maintained at 184°C for all samples. Supercritical nitrogen was used as a physical blowing agent and was injected very precisely into the molten polymer in a MuCell Transfer Mixer (MTM) at a concentration of 0.01 wt% to 0.07 wt%. The extruder zone temperatures were set according to conventional processing as indicated in the material data sheets. Samples 2 and 3 are 342gr / m 2 and a foam version of solid sample 1 having the same base weight, which has a density 40% and 45% lower compared to solid sample 1, respectively.

[0044] As reported in Table 1, sample 3 exhibits a 190% higher bending stiffness value compared to its solid counterpart. Samples 5 and 6 have a bending stiffness of about 390 gr / m 2 The foam versions of Sample 4 with the same basis weight of 1.5 cc / m2 have 37% and 39% lower densities compared to solid Sample 4. Samples 5 and 6 exhibit 140% and 160% higher bending stiffness values, respectively, compared to their solid counterparts. Sample 6 possesses a Sheffield surface smoothness value of about 17.5, which is comparable to Sample 4. Both Samples 5 and 6 have a Sheffield surface smoothness value of about 1.5 cc / m2, which is comparable to Sample 4. 2 / day. Samples 8, 9, 10, and 11 were approximately 240 g / m 2 The foam versions of sample 7 with similar base weights of 1000 cc / m2, which have approximately 20%-30% lower density. Samples 9 and 10 possess 140% and 190% higher bending stiffness compared to their solid counterparts. Although samples 8 and 9 have a much thinner (almost half) middle layer compared to sample 10, they have a 3 cc / m2 2 All show oxygen transmission rates in the same range, less than 10 / day. Samples 8 and 9 also have Sheffield surface smoothness values ​​of less than 10, which is comparable to their solid counterparts. Furthermore, almost all samples 1 to 11 were 1gr / m 2 It has a water vapor transmission rate of less than 100 / day.

[0045] [Table 1]

[0046] Example 2: Samples of multilayer HDPE films (3 layers) were produced using a Windmoeller & Hoelscher Corporation blown film line containing one 105 mm main extruder and two identical 75 mm co-extruders. The core extruders were both equipped with supercritical gas injection units capable of injecting nitrogen or carbon dioxide, and a 120 mm MuCell transfer mixer from MuCell Extrusion LLC. All films were produced by a blown film process using annular dies with die gaps ranging from 0.45 to 1.3 mm, and blow-up ratios ranging from 2.8:1 to 3.5:1. The lips of the annular die were boron nitride coated.

[0047] Table 2 contains the characterization results of the products made (samples 12-15) as non-limiting examples to elucidate some aspects of the present invention. The samples had a melt index of 0.85 dg / min and a melt strength of 0.962 gr / cm. 3 The foams were produced in Dow Chemical Company's high density polyethylene ELITE 5960 having a density of 1000 .mu.m. The calcium carbonate and talc were prepared and introduced as highly loaded masterbatches of 80 wt.% loaded calcium carbonate and 70 wt.% loaded talc, respectively, into HDPE as the base carrier resin. All tie layers contain ADMER adhesive resin, an anhydride grafted polyolefin. The foam core layer of all samples contains talc as a cell nucleating agent.

[0048] All samples were coextruded at a total throughput of about 260-290 kg / hr as it is listed in Table 2. The temperature of the mixing section where the supercritical gas was injected was maintained at 190°C for all samples 12-15. Supercritical nitrogen was used as a physical blowing agent and was injected very precisely into the molten polymer in a MuCell Transfer Mixer (MTM) at a concentration of 0.011 wt% to 0.02 wt%. Sample 15 is the solid counterpart of Samples 12, 13, and 14, which has a density approximately 18% to 25% lower than that of Sample 15. Sample 15 has a density of 1.4 cc / m 2 All samples exhibited a water vapor transmission rate of less than 1 and a Sheffield surface smoothness of less than 10.

[0049] [Table 2]

[0050] Example 3: A crease specimen of sample 11 in Table 1 was prepared according to TAPPI / ANSI T512 sp-12 and tested for oxygen transmission rate (OTR) before and after creasing and folding. As explained, the cc / m 2 The OTR values ​​at 100% crease / 24 hr were measured in accordance with ASTM D3985 at a standard temperature of 73°F (23°C) and 0% relative humidity (RH). All samples tested were identical. The average measured OTR value for sample 11 before and after creasing was 1.56 cc / m 2 / 24hr and 1.6cc / m 2 / 24hr. A creased sample of the solid counterpart of sample 11 in Table 1 was prepared and the OTR value was measured according to the method described above. The thickness of the sample was 260 μm. The average measured OTR value before and after creasing was 0.95 cc / m, respectively. 2 / 24hr and 1.17cc / m 2 / 24hr.

[0051] Example 4. A creased sample of the packaging tube of AVENO daily moisturizing lotion was prepared according to TAPPI / ANSI T512 sp-12 and tested for oxygen transmission rate (OTR) before and after creasing and folding. The total thickness of the sample was 480 μm, including one EVOH layer with a thickness of 60 μm. As explained, the cc / m 2 The OTR values ​​at 1000 cc / m2 / 24 hr were measured according to ASTM D3985 at a standard temperature of 73°F (23°C) and 0% relative humidity (RH). The average measured OTR before and after creasing was 0.29 cc / m2, respectively. 2 / 24hr and 0.41cc / m 2 / 24hr.

Claims

1. a foam layer containing a plurality of cells, wherein at least 10% of the cells are closed cells; and two solid skin layers comprising HDPE on each side of the foam layer; and a solid layer comprising ethylene vinyl alcohol (EVOH); Including, wherein the foam layer is between one of the solid skin layers and a solid layer comprising EVOH, and the film has an overall thickness of 8 mm or greater, and the ratio of the oxygen transmission rate in cc / m2 / 24 hr according to ASTM D3985 of the creased, folded or scored film to the oxygen transmission rate of the same film before creasing, folding or scoring is less than 1.

1. Creased, folded, or scored multilayer foam film.

2. 10. The film of claim 1, wherein the film has an average Sheffield smoothness according to TAPPI T 538 of less than 40.

3. 3. The film of claim 1 or 2, wherein the film is pierced or punched.

4. 3. The film of claim 1 or 2, wherein the film has a bulk density value of less than 0.962 gr / cm.

5. 3. The film of claim 1 or 2, wherein the film has an average Sheffield smoothness according to TAPPI T 538 of less than 25.

6. 3. The film of claim 1 or 2, wherein the film has a Taber stiffness value according to TAPPI / ANSI T 489 om-15 of greater than 18 and a ratio of mass per unit area (mass per unit area, grams per square meter (gr / m2)) to Taber stiffness value of 13 or less.

7. 3. The film of claim 1 or 2, wherein the film has a water vapor transmission rate of less than 1 gr / m2 / 24 hr according to ASTM E398-13.

8. 3. The film of claim 1 or 2, wherein the film has an oxygen transmission rate of less than 10 cc / m2 / 24 hr according to ASTM D3985.

9. 3. The film of claim 1 or 2, wherein the foam layer comprises HDPE having a density of 0.94 to 0.962 gr / cm.

10. 3. The film of claim 1 or 2, wherein the film has a Taber Flexural Stiffness value of less than 280 according to TAPPI / ANSI T 489 om-15.

11. 3. The film of claim 1 or 2, wherein at least one layer contains amounts of other additives, including pigments, slip agents, antistatic agents, UV stabilizers, maleic anhydride, and antioxidants.

12. 3. The film of claim 1 or 2, wherein the film has at least one solid skin layer having a static coefficient of friction value according to ASTM D1894 of less than 0.

4.

13. 3. The film of claim 1 or 2, wherein the film has at least one solid skin layer having a dynamic coefficient of friction according to ASTM D1894 of less than 0.

3.

14. 3. The film of claim 1 or 2, wherein the film comprises 3, 5, or 7 layers and is produced by a blown film process using an annular extrusion die and a blow-up ratio of 1.5:1 to 3.5:

1.

15. 3. The film of claim 1, wherein a nucleating agent is used to produce a foamed layer having an average cell size of 10 to 100 μm.

16. 3. The film according to claim 1, wherein the cell density of the unfoamed volume in the foam layer is 10 to 10 cells / cm, and the film density is 0.1 to 0.9 g / cm.

17. 3. The film of claim 1 or 2, wherein the foam layer contains greater than 50% closed cells.

18. 3. The film of claim 1 or 2, wherein the foam layer is comprised of a nucleating agent having an inorganic additive, an organic additive, or a mixture of inorganic and organic additives in an amount of 0.05 to 15 weight percent.

19. 3. The film according to claim 1, wherein at least one layer is a solid layer comprising HDPE having a melt index of 0.02 to 20 dg / min.

20. 3. The film of claim 1 or 2, wherein at least one of the layers, excluding both outer skin layers, comprises LDPE.

21. 1. A method for making a creased, folded, or scored multilayer film, comprising: co-extruding a foam layer, two solid skin layers comprising HDPE, and one solid layer comprising ethylene vinyl alcohol (EVOH) to form a multilayer film, wherein the foam layer contains a plurality of cells, wherein at least 10% of the cells are closed cells, the foam layer is between one of the solid skin layers and the layer comprising EVOH, and the film has an overall thickness of 8 mils or greater; and creasing, folding, or scoring multilayer films; wherein the oxygen transmission rate value of the creased, folded, or scored film in cc / m2 / day according to ASTM D3985 does not increase by more than 10% of the oxygen transmission rate value of the multilayer film before creasing, folding, or scoring in cc / m2 / day according to ASTM D3985; A method comprising:

22. 22. The method of claim 21, wherein any foamed layer is coextruded immediately adjacent to the layer comprising EVOH.

23. 23. The method of claim 21 or 22, further comprising piercing or punching the film.