Linear tear multilayer film based on polypropylene copolymer

Abstract

A product package that exhibits good linear tear behavior. The product package is a multilayer film having an inner layer made of a blend of an ethylene copolymer and a polypropylene copolymer. The inner layer of the multilayer film comprises a substantial proportion of the thickness of the multilayer film. The multilayer film has linear tear behavior even when force is applied at an angle that is offset from the direction of the tear.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Patent Application Serial No. 63 / 273,227, filed October 29, 2021, entitled “Polypropylene Copolymer Based Linear Tear Multi-Layer Film,” the entire contents of which are incorporated herein by reference. Background Technology

[0003] The subject matter disclosed herein relates to a packaging film. More specifically, the subject matter disclosed herein relates to a multilayer packaging film exhibiting linear tear behavior.

[0004] Packaging films are used for packaging a wide variety of products. Because the shrink film shrinks onto the packaging, the product gains an attractive appearance. High-end consumer electronics products are an example of products seeking shrink films that exhibit straight / linear tear properties when shrinkable. Currently available products exhibit random tearing behavior, resulting in uneven tearing and an unattractive appearance.

[0005] However, removing the packaging film can sometimes be difficult. Knives, blades, and scissors are often used to open the packaging. However, the use of these tools increases the risk of injury to consumers and damage to the product.

[0006] Furthermore, opening such packaging requires more time and effort and can lead to frustration. This frustration can result in negative biases towards the packaged product.

[0007] To make opening the packaging easier, tear initiators have been used to induce easier manual tearing of the packaging film. However, some films produce uneven tears, and the tear line may deviate from the intended path, resulting in uneven tearing.

[0008] The above discussion is provided for general background information only and is not intended to be used as an aid in determining the scope of the claimed subject matter. Summary of the Invention

[0009] A product packaging exhibiting good linear tear behavior. The product packaging is a multilayer film having an inner layer made of a blend of ethylene copolymer and polypropylene copolymer. The inner layer of the multilayer film occupies a substantial proportion of the multilayer film thickness. Even when force is applied at an angle deviating from the tear direction, the multilayer film exhibits linear tear behavior.

[0010] One advantage that can be achieved in practice with some publicly available implementations of product packaging is that it is wrapped in a film that exhibits good linear tear resistance, resulting in a satisfactory opening appearance.

[0011] In one exemplary embodiment, a packaging product is disclosed. The packaging product includes a first product and a multilayer film shrunken to the outer surface of the first product. The multilayer film includes: a first outer layer having a first thickness; a second outer layer having a second thickness; and an inner layer comprising a blend of 60-80 wt% polypropylene copolymer and 20-40 wt% ethylene copolymer; a first intermediate layer disposed between the first outer layer and the inner layer; and a second intermediate layer disposed between the second outer layer and the inner layer. The thickness of the inner layer is at least 45% or 50% of the thickness of the multilayer film. The multilayer film has at least one tear initiation portion to initiate tear propagation along a tear line. The multilayer film, when torn in at least one direction in a machine or in the lateral direction, has a diameter not greater than at least one selected from 150 mm. 2 200mm 2 250mm 2 300mm 2 350mm 2 400mm 2 450mm 2 500mm 2 550mm 2 600mm 2 650mm 2 700mm 2 750mm 2 and 800mm 2 The value of the angular tear deviation area is calculated from a 13cm tear using a tear force applied at an angle of 26.6° away from the desired linear tear path and measured according to the angular tear deviation test.

[0012] In another exemplary embodiment, a multilayer film is disclosed. The multilayer film includes a first outer layer having a first thickness; a second outer layer having a second thickness; an inner layer comprising a blend of 60-80 wt% polypropylene copolymer and 20-40 wt% ethylene copolymer; a first intermediate layer disposed between the first outer layer and the inner layer; and a second intermediate layer disposed between the second outer layer and the inner layer. The thickness of the inner layer is at least 45% or 50% of the thickness of the multilayer film. The multilayer film, when torn in at least one direction in a machine or in the transverse direction, has a diameter not greater than at least one element selected from 150 mm. 2 200mm 2 250mm 2 300mm 2 350mm 2 400mm2 450mm 2 500mm 2 550mm 2 600mm 2 650mm 2 700mm 2 750mm 2 and 800mm 2 The value of the angular tear deviation area is calculated from a 13cm tear using a tear force applied at an angle of 26.6° away from the desired linear tear path and measured according to the angular tear deviation test.

[0013] In another exemplary embodiment, a method of packaging a product is disclosed. The method includes the steps of: providing a first product; wrapping the first product in a multilayer film; sealing the multilayer film; and shrinking the multilayer film to fit tightly around the first product. The multilayer film includes: a first outer layer having a first thickness; a second outer layer having a second thickness; and an inner layer comprising a blend of 60-80% by weight of a polypropylene copolymer and 20-40% by weight of an ethylene copolymer; a first intermediate layer disposed between the first outer layer and the inner layer; and a second intermediate layer disposed between the second outer layer and the inner layer. The thickness of the inner layer is at least 45% or 50% of the thickness of the multilayer film. The multilayer film has a tear diameter of no more than at least 150 mm when torn in at least one direction, either in a machine or in the transverse direction. 2 200mm 2 250mm 2 300mm 2 350mm 2 400mm 2 450mm 2 500mm 2 550mm 2 600mm 2 650mm 2 700mm 2 750mm 2 and 800mm 2 The value of the angular tear deviation area is calculated from a 13cm tear using a tear force applied at an angle of 26.6° away from the desired linear tear path and measured according to the angular tear deviation test.

[0014] This brief description of the invention is intended only to provide a brief overview of the subject matter disclosed herein according to one or more illustrative embodiments, and is not intended as a guide for interpreting the claims or for limiting or restricting the scope of the invention, which is defined only by the appended claims. This brief description is provided to present an illustrative choice of concepts in a simplified form, which will be further described below in a detailed description. This brief description is not intended to identify key or essential features of the claimed subject matter, nor is it intended to serve as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to embodiments that address any or all the disadvantages pointed out in the background art. Attached Figure Description

[0015] The invention can be described in detail with reference to certain embodiments, some of which are illustrated in the accompanying drawings, in a manner that enables understanding of its features. However, it should be noted that the drawings illustrate only certain embodiments of the invention and are therefore not intended to limit its scope, which encompasses other equally effective embodiments. The drawings are not necessarily to scale, and the emphasis is generally placed on illustrating the features of certain embodiments of the invention. In the drawings, the same numerals are used throughout the various views to indicate the same parts. Therefore, for a further understanding of the invention, reference can be made to the following detailed description, read in conjunction with the accompanying drawings, wherein:

[0016] Figure 1 This is a schematic diagram of the process for manufacturing a multilayer film according to the embodiment described herein;

[0017] Figure 2 This is a schematic diagram of the hot blown film manufacturing process according to the embodiment described herein;

[0018] Figures 3A-3B This is an exemplary embodiment illustrating a membrane with good linear tear propagation according to the embodiments described herein;

[0019] Figure 4 It is a contrast film showing the linear tear propagation with difference;

[0020] Figures 5A-5C This is an exemplary embodiment of a packaged product encased in a multilayer film according to the embodiments described herein.

[0021] Figures 6A-6B This is the presentation of the angular tear deviation test described in this article.

[0022] Figure 7 An exemplary membrane exhibiting good linear tear behavior in the angular tear deviation test described herein is depicted.

[0023] Figure 8 An exemplary membrane exhibiting poor linear tearing behavior in the angular tear deviation test described herein is depicted. Detailed Implementation

[0024] As used herein, the term "membrane" includes plastic web, whether it is a film or a sheet. The membrane may have a thickness of 3 mils or less, or 2 mils or less, or 1 mil or less, or a thickness of 0.5 to 8 mils, or 0.5 to 5 mils, or 0.5 to 2 mils, or 0.5 to 1 mil.

[0025] The multilayer membranes described herein may comprise at least and / or at most any of the following numbers of layers: 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15. As used herein, the term "layer" refers to a discrete membrane assembly that extends substantially co-exists with the membrane and has a substantially uniform composition. For the purposes of this application, two or more directly adjacent layers having substantially the same composition may be considered as a single layer. In one embodiment, the multilayer membrane employs microlayers. Microlayer portions may comprise 10 to 1,000 microlayers in each microlayer portion.

[0026] Below are some examples of combinations, where letter symbols represent membrane layers. In the multilayer membrane expressions below, where the same letter appears more than once, each occurrence of that letter can represent the same or different components within a category performing similar functions.

[0027] A / B / C / B / A, A / B / C / D / A, A / D / C / D / A, A / B / D / C / B / A, A / D / B / C / B / A, A / C / B / C / B / A, A / C / B / C / D / A, A / C / D / C / D / A, A / B / D / C / D / B / A, A / D / B / C / D / B / A, A / B / C / D / C / B / A, A / B / C / B / D / B / C / B / A.

[0028] “A” represents the outer layer as discussed below.

[0029] “B” represents the intermediate layer discussed below.

[0030] “C” represents the linear tear layer discussed below.

[0031] “D” represents the bulk layer, as discussed below.

[0032] All percentages of composition used in this article are presented on a "by weight" basis unless otherwise specified.

[0033] Linear tear layer

[0034] The multilayer membrane described herein includes a linear tear layer constituting a substantial portion of the multilayer membrane. This linear tear layer allows the multilayer membrane to be torn sufficiently easily, such that the membrane can be torn without the use of sharp tools such as blades, knives, or scissors. The linear tear layer further imparts good linear tear propagation in the machine direction of the membrane. The multilayer membrane, when torn, leaves a relatively smooth edge with a clean appearance.

[0035] As used in this article, the verb "tear" means to pull an object apart by force. The noun "tear" refers to the breakage caused in the torn object. A membrane is torn due to placing it under sufficient tension, causing it to be pulled apart by force. The tension is concentrated at the initiation of the tear, which allows a smaller tension to pull the membrane apart, i.e., to tear the membrane.

[0036] For tears in packaging products made from them, as used herein, the phrase “tears can be extended” refers to the way in which the film tends to extend the tear when subjected to ordinary manual opening.

[0037] The linear tear layer comprises a blend of 60-80% by weight of a polypropylene copolymer and 20-40% by weight of an ethylene copolymer. Suitable ethylene copolymers include ethylene homopolymers, such as low-density polyethylene; ethylene / α-olefin copolymers, such as those defined below; and other ethylene copolymers, such as ethylene / vinyl acetate copolymers; ethylene / alkyl acrylate copolymers; or ethylene / (meth)acrylic acid copolymers. Ethylene / α-olefin copolymers as used herein refer to copolymers of ethylene with one or more comonomers selected from C4-C10 α-olefins such as butene-1, hexene-1, and octene-1, wherein the copolymer molecules comprise long polymer chains having relatively few side chains from the α-olefins reacting with ethylene. This molecular structure contrasts with conventional high-density polyethylene (HDPE), which is highly branched relative to ethylene / α-olefin copolymers and contains both long and short chain branches. Ethylene / α-olefin copolymers include one or more of the following: 1) high-density polyethylene, for example, having a density greater than 0.94 g / cm³. 3 2) Medium-density polyethylene, for example, with a density of 0.93 to 0.94 g / cm³. 3 3) Linear medium-density polyethylene, for example, with a density of 0.926 to 0.94 g / cm³; 4) Low-density polyethylene, for example, with a density of 0.915 to 0.939 g / cm³. 3 5) Linear low-density polyethylene, for example, with a density of 0.915 to 0.935 g / cm³. 3 6) Very low or ultra-low density polyethylene, for example, with a density of less than 0.915 g / cm³. 3And homogeneous ethylene / α-olefin copolymers. Homogeneous ethylene / α-olefin copolymers include those with densities less than about any of the following: 0.925, 0.922, 0.92, 0.917, 0.915, 0.912, 0.91, 0.907, 0.905, 0.903, 0.90, and 0.86 g / cm³. 3 Unless otherwise specified, all densities herein are measured according to ASTM D1505. In one embodiment, the ethylene copolymer is linear low-density polyethylene. In one embodiment, the density of the ethylene copolymer, measured according to ASTM D1505, is from 0.915 to 0.935 g / cm³. 3 .

[0038] Suitable polypropylene copolymers include ethylene-propylene copolymers. In one embodiment, the density of the ethylene-propylene copolymer, as measured according to ASTM D1505, is between 0.860 and 0.920 g / cm³. 3 In one embodiment, the melt flow rate of the ethylene-propylene copolymer, as measured according to ISO 1133, is 6.0 to 9.0 g / 10 min at 230 °C / 0.216 kg.

[0039] In one embodiment, the linear tear layer comprises a blend of linear low-density polyethylene and an ethylene-propylene copolymer having an ethylene content of 3-20% by weight. In another embodiment, the ethylene-propylene copolymer has an ethylene content of 8-15% by weight. In yet another embodiment, the linear tear layer comprises a blend of a linear low-density ethylene / octene copolymer having an octene content of less than 9% by weight and an ethylene-propylene copolymer having an ethylene content of 9-14% by weight.

[0040] The thickness of the linear tear layer is selected to provide sufficient tear resistance for the multilayer film. The thickness of the linear tear layer can be at least any of the following values: 0.05 mil, 0.1 mil, 0.15 mil, 0.2 mil, 0.25 mil, 0.3 mil, 0.35 mil, 0.4 mil, 0.45 mil, 0.5 mil, and 0.6 mil. The thickness of the linear tear layer can be less than any of the following values: 4 mil, 3 mil, 2 mil, 1 mil, 0.7 mil, 0.5 mil, and 0.3 mil. The thickness of the linear tear layer as a percentage of the total film thickness is at least any of the following values: 45%, 50%, 55%, 60%, 65%, 70%, 75%, and 80%; and can be between any of the foregoing values ​​(e.g., 50% to 60% or 45% to 80%).

[0041] outer layer

[0042] At least one outer layer is a heat seal layer. In an embodiment, both outer layers of the membrane are heat seal layers. As used herein, the phrases “seal layer,” “sealing layer,” “heat seal layer,” and “sealant layer” refer to one or more outer layers that relate to the sealing of the membrane with itself, with another layer of the same or another membrane, and / or with another article that is not a membrane.

[0043] As used herein, the term "heat-seal" and the phrase "heat-sealing" refer to any seal between a first region of a membrane surface and a second region of a membrane surface, wherein the seal is formed by heating the regions to at least their respective seal initiation temperatures. Heat sealing is the process of joining two or more thermoplastic films or sheets by heating the areas in contact with each other to a temperature at which fusion occurs, typically with the aid of pressure. Heating can be performed by any one or more of a wide variety of methods, such as using heating rods, hot wires, hot air, infrared radiation, ultraviolet radiation, electron beams, ultrasound, and melt-beads. Heat sealing is typically a relatively narrow seal on the membrane (e.g., 0.02 inches to 1 inch wide). A particular type of heat sealing is heat sealing using a pulse sealing mechanism, which uses a combination of heat and pressure to form a seal, wherein the heating method provides short pulses of heat while pressure is applied to the membrane by a sealing rod or sealing wire, followed by rapid cooling of the rod or wire.

[0044] The heat-sealing layer comprises a thermoplastic polymer, including but not limited to thermoplastic polyolefins, polyamides, polyesters, and polyvinyl chloride. In embodiments, the polymer used for the sealing layer includes homogeneous ethylene / α-olefin copolymers, heterogeneous ethylene / α-olefin copolymers, ethylene homopolymers, and ethylene / vinyl acetate copolymers. In some embodiments, the heat-sealing layer may comprise a polyolefin, particularly an ethylene / α-olefin copolymer. For example, a polyolefin with a density of 0.88 g / cc to 0.917 g / cc, or 0.90 g / cc to 0.917 g / cc, or less than 0.92 g / cc. More particularly, the sealing layer may comprise at least one member selected from: high-density polyethylene, linear low-density polyethylene, medium-density polyethylene, low-density polyethylene, very low-density polyethylene, homogeneous ethylene / α-olefin copolymers, and polypropylene. As used herein, "polymer" refers to homopolymers, copolymers, terpolymers, etc. As used herein, "copolymer" includes copolymers, terpolymers, etc.

[0045] As used herein, the term "polyolefin" refers to olefin polymers and copolymers, particularly ethylene and propylene polymers and copolymers, and polymeric materials having at least one olefinic comonomer. Polyolefins can be linear, branched, cyclic, aliphatic, aromatic, substituted, or unsubstituted. The term polyolefin includes homopolymers of olefins, copolymers of olefins, copolymers of olefins and non-olefinic comonomers that can copolymerize with olefins, such as vinyl monomers, modified polymers of the aforementioned polymers, etc. Modified polyolefins include modified polymers prepared by copolymerizing homopolymers of olefins or copolymers thereof with unsaturated carboxylic acids such as maleic acid, fumaric acid, etc., or their derivatives such as acid anhydrides, ester metal salts, etc. It can also be obtained by incorporating unsaturated carboxylic acids such as maleic acid, fumaric acid, etc., or their derivatives such as acid anhydrides, ester metal salts, etc., into olefin homopolymers or copolymers. In one embodiment, the heat-sealing layer is primarily composed of polyolefins. In one embodiment, based on the total composition of the heat-sealing layer, the total polyolefin content of the heat-sealing layer is 50 to 90% by weight. In one embodiment, based on the total composition of the heat-sealing layer, the total polyolefin content of the heat-sealing layer is 70 to 90% by weight. In another embodiment, based on the total composition of the heat-sealing layer, the total polyolefin content of the heat-sealing layer is at least any of the following values: 50% by weight, 55% by weight, 60% by weight, 65% by weight, 70% by weight, 75% by weight, 80% by weight, 85% by weight, 90% by weight, or 95% by weight.

[0046] Ethylene homopolymers or copolymers refer to ethylene homopolymers, such as low-density polyethylene; ethylene / α-olefin copolymers, such as those defined below; and other ethylene copolymers, such as ethylene / vinyl acetate copolymers; ethylene / alkyl acrylate copolymers; or ethylene / (meth)acrylic acid copolymers. Ethylene / α-olefin copolymers as used herein refer to copolymers of ethylene with one or more comonomers selected from C4-C10 α-olefins such as butene-1, hexene-1, and octene-1, wherein the copolymer molecules comprise long polymer chains having relatively few side chains from the α-olefins reacting with ethylene. This molecular structure contrasts with conventional high-density polyethylene (HDPE), which is highly branched relative to ethylene / α-olefin copolymers and contains both long and short chain branches. Ethylene / α-olefin copolymers include one or more of the following: 1) high-density polyethylene, for example, having a density greater than 0.94 g / cm³. 3 2) Medium-density polyethylene, for example, with a density of 0.93 to 0.94 g / cm³. 3 3) Linear medium-density polyethylene, for example, with a density of 0.926 to 0.94 g / cm³. 3 4) Low-density polyethylene, for example, with a density of 0.915 to 0.939 g / cm³. 3 5) Linear low-density polyethylene, for example, with a density of 0.915 to 0.935 g / cm³.3 6) Very low or ultra-low density polyethylene, for example, with a density of less than 0.915 g / cm³. 3 Homogeneous ethylene / α-olefin copolymers include those with densities less than about any of the following: 0.925, 0.922, 0.92, 0.917, 0.915, 0.912, 0.91, 0.907, 0.905, 0.903, 0.90, and 0.86 g / cm³. 3 Unless otherwise specified, all densities mentioned herein are measured according to ASTM D1505.

[0047] In one embodiment, the melting point of the heat-sealing layer is less than any of the following values: 220°C, 210°C, 200°C, 190°C, 180°C, 170°C, 160°C, 150°C, 140°C, and 130°C; and the melting point of the heat-sealing layer may be at least any of the following values: 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, and 150°C. All references to polymers, resins, or films in this application refer to the melting peak temperature of the main molten phase of the polymer, resin, or film, determined by differential scanning calorimetry according to ASTM D-3418.

[0048] In embodiments where the heat-sealing layer comprises an amorphous material, the heat-sealing layer may not clearly display a melting point. The glass transition temperature of the heat-sealing layer can be less than any of the following values ​​and can be between any of the following values: 125°C, 120°C, 110°C, 100°C, 90°C, 80°C, 70°C, 60°C, and 50°C; measured with relative humidity that can be any of the following values: 100%, 75%, 50%, 25%, and 0%. The glass transition temperature (Tg) of all mentioned polymers is... g All measurements were taken by Perkin Elmer “half Cp extrapolated” (the point on the curve where the specific heat change is half that in the complete transition) according to ASTM D3418 “Standard Test Method of Transition Temperatures of Polymers by Thermal Analysis”, which is hereby incorporated herein by reference in its entirety.

[0049] In one embodiment, the heat seal layer has a melt index or composite melt index of at least 0.5, 1.0, 1.5, 2.0, 2.5 or 3.0 g / 10 min at 190°C and 2.16 kg, as measured by ASTM D1238.

[0050] The thickness of the heat-sealing layer can be selected to provide sufficient material to induce a strong heat-sealed bond, but not so thick as to adversely affect the film properties to an unacceptable level. The thickness of the heat-sealing layer can be at least any of the following values: 0.05 mil, 0.1 mil, 0.15 mil, 0.2 mil, 0.25 mil, 0.3 mil, 0.35 mil, 0.4 mil, 0.45 mil, 0.5 mil, and 0.6 mil. The thickness of the heat-sealing layer can be less than any of the following values: 2 mil, 1 mil, 0.7 mil, 0.5 mil, and 0.3 mil. The thickness of the heat-sealing layer as a percentage of the total film thickness can be less than any of the following values: 25%, 20%, 15%, 10%, and 5%; and can be between any of the foregoing values ​​(e.g., 10% to 20%).

[0051] In one embodiment, the heat-sealing layer comprises 30 to 70% by weight of a low-density polyethylene copolymer or a linear low-density polyethylene copolymer having a melting point of 90-130°C. In one embodiment, the heat-sealing layer comprises 10 to 40% by weight of a medium-density polyethylene copolymer having a melting point of 90-140°C. In one embodiment, the heat-sealing layer comprises at least 50%, 60%, and 70% by weight of an ethylene copolymer. In one embodiment, the heat-sealing layer comprises 5 to 25% by weight of an ethylene / vinyl acetate copolymer. In one embodiment, the heat-sealing layer comprises at least 9% by weight of an ethylene / vinyl acetate copolymer. In one embodiment, the heat-sealing layer comprises one or more additives that can be used in thermoplastic films, such as anti-blocking agents, slip agents, anti-fogging agents, colorants, pigments, dyes, antioxidants, fillers, radiation stabilizers, and antistatic agents. Available additives may be included as a masterbatch. Additives include, but are not limited to, stearates such as metal stearates, zinc stearate and aluminum stearate, silica, ceramic beads, and waxes such as erucamide wax and oleamide wax.

[0052] Intermediate layer

[0053] The membrane may include one or more intermediate layers. In this document, “intermediate” refers to a layer of a multilayer membrane located between the outer layers. In this document, “intermediate layer” refers to a layer that is not an outer or surface layer, and is typically the central, adhesive, or core layer of the membrane. In this document, “outer layer” refers to the typically outermost layer of a multilayer membrane, generally a surface layer or top layer, although additional layers, coatings, and / or membranes may be adhered to it.

[0054] An intermediate layer can be, for example, between a heat-sealing layer and a linear tear layer. An intermediate layer can be directly adjacent to the heat-sealing layer, such that there is no intermediate layer between the intermediate layer and the heat-sealing layer. An intermediate layer can be directly adjacent to both the heat-sealing layer and the linear tear layer.

[0055] The intermediate layer can be an adhesive layer. An adhesive layer is an inner membrane layer that adheres two layers to each other. Available adhesive polymers include thermoplastic polymers that are compatible with both the polymer of one directly adjacent layer and the polymer of the other directly adjacent layer. This dual compatibility enhances the adhesion between the bonded layers. The adhesive layer can be made of polyolefins such as modified polyolefins, ethylene / vinyl acetate copolymers, modified ethylene / vinyl acetate copolymers, and homogeneous ethylene / α-olefin copolymers. Typical adhesive layer polyolefins include anhydride-modified grafted linear low-density polyethylene, anhydride-grafted (i.e., anhydride-modified) low-density polyethylene, anhydride-grafted polypropylene, anhydride-grafted methyl acrylate copolymers, anhydride-grafted butyl acrylate copolymers, homogeneous ethylene / α-olefin copolymers, and anhydride-grafted ethylene / vinyl acetate copolymers.

[0056] The interlayer may have a thickness of at least about and / or at most about any of the following: 0.05, 0.1, 0.15, 0.2, 0.25, 0.5, 1, and 2 mils. The thickness of the interlayer as a percentage of the total film thickness may be at least about and / or at most about any of the following percentages: 1%, 3%, 5%, 7%, 10%, 15%, 20%, and 25%.

[0057] In one embodiment, the interlayer comprises 30 to 70% by weight of a low-density polyethylene copolymer or a linear low-density polyethylene copolymer having a melting point of 90-130°C. In one embodiment, the interlayer comprises 10 to 40% by weight of an ethylene-propylene copolymer having… In one embodiment, the interlayer comprises 5 to 25% by weight of an ethylene / vinyl acetate copolymer. In one embodiment, the interlayer comprises one or more additives that can be used in thermoplastic films, such as antiblocking agents, slip agents, antifogging agents, colorants, pigments, dyes, antioxidants, fillers, radiation stabilizers, and antistatic agents.

[0058] Fill layer

[0059] The membrane may include one or more other layers, such as filler layers. Filler layers are typically one or more layers of a membrane that can improve the membrane's abuse resistance, toughness, or modulus. In some embodiments, the membrane includes filler layers that function to improve the membrane's abuse resistance, toughness, and / or modulus. Filler layers typically contain polymers that are inexpensive compared to other polymers in the membrane that provide some specific purpose unrelated to abuse resistance, modulus, etc. In one embodiment, the filler layer contains at least one member selected from: ethylene / α-olefin copolymers, ethylene homopolymers, propylene / α-olefin copolymers, propylene homopolymers, and combinations thereof.

[0060] The filler layer may have a thickness of at least about and / or at most about any of the following: 0.05, 0.1, 0.15, 0.2, 0.25, 0.5, 1, and 2 mils. The thickness of the filler layer as a percentage of the total film thickness may be at least about and / or at most about any of the following percentages: 1%, 3%, 5%, 7%, 10%, 15%, 20%, and 25%. In one embodiment, the filler layer comprises one or more additives that can be used in thermoplastic films, such as antiblocking agents, slip agents, antifogging agents, colorants, pigments, dyes, antioxidants, fillers, radiation stabilizers, and antistatic agents.

[0061] Multilayer film

[0062] Figure 1 The diagram illustrates the membrane manufacturing process. Figure 1 In the process illustrated in the diagram, solid polymer beads (not shown) of various polymer formulations are fed into multiple extruders (extruder 88 is shown for simplicity). Within extruder 88, the polymer beads are conveyed, melted, and degassed, and the resulting bubble-free melt is then conveyed to die 90 and extruded through an annular die to obtain a strip 92, which is preferably about 10 to 20 mils thick and preferably has a flattened width of about 2 to 10 inches.

[0063] After being cooled or quenched by water spray from cooling ring 94, the strip 92 is collapsed by clamp roller 96 and then fed through a vault 98 surrounded by a protective body 100, where the strip 92 is irradiated with high-energy electrons (i.e., ionizing radiation) from the core transformer accelerator 102. The strip 92 is guided through the vault 98 on roller 104. Preferably, the strip 92 is irradiated to a level of about 40 to about 120 kGy to obtain an irradiated membrane 106, which then passes through guide roller 116, after which the irradiated membrane 106 is conveyed to and through a hot water bath 118 containing hot water 120. In some embodiments, the hot water bath is an oven or a steam bath. The irradiated membrane 106 is immersed in the hot water 120 (at a temperature of 185 to 210°F in embodiments) for about 10 to about 100 seconds, i.e., a sufficiently long period of time for the membrane to reach the temperature required for biaxial orientation. Subsequently, the resulting hot, radiated film 122 is guided through pressure roller 124, and air bubbles 126 are blown out, thereby laterally stretching the hot, radiated film 122 to form an oriented film 128. Furthermore, during blowing, i.e., laterally stretching, the surface velocity of pressure roller 130 is higher than that of pressure roller 124, resulting in longitudinal orientation. As a result of lateral stretching and longitudinal stretching, an oriented film 128 is prepared, which in this embodiment has been stretched at a ratio of about 1:1.5 to about 1:6 and stretched at a ratio of about 1:1.5 to about 1:6. In this embodiment, stretching and stretching are each performed at a ratio of about 1:2 to about 1:4. The result is a biaxial orientation of about 1:2.25 to about 1:36, or in this embodiment, about 1:4 to about 1:16. While bubble 126 is held between pinch rolls 124 and 130, alignment film 128 is folded by roll 132 and subsequently conveyed through pinch roll 130 and guide roll 134, then wound onto winding roll 136. Inert roll 138 ensures good winding. This process can be performed continuously in a single operation or intermittently, for example as a two-stage process, in which the extruded, radiated strip is wound up after radiation and, after a period of storage, unwound and heated and aligned to obtain alignment film 128.

[0064] The resulting multilayer film can be used to form bags, sleeves, thermoformed articles, etc., which can then be used for product packaging. Although various embodiments are shown and described herein, other packaging structures are also considered, such as resealable bags, side-sealed bags, vertical form-filled bags, vertical pouchpackaging, end-sealed bags, overlap-sealed bags, etc.

[0065] In one embodiment, the membrane has a first outer layer directly adhered to a first surface of a first intermediate layer and a second outer layer adhered to a first surface of a second intermediate layer, and the second surface of the first intermediate layer is directly adhered to the first surface of the inner tear layer, and the second surface of the second intermediate layer is directly adhered to the second surface of the inner tear layer.

[0066] In the implementation plan, through Figure 2 The diagram shows the blown film production process. Figure 2 A schematic diagram of a process for manufacturing a "thermally blown" film is shown, in which the film is oriented in a molten state and therefore not heat-shrinkable. Although in Figure 2 Only one extruder 139 is shown, but it should be understood that more than one extruder can be used to manufacture the film.

[0067] exist Figure 2 In the process, extruder 530 supplies molten polymer to annular die 531 for film formation, which can be single-layer or multi-layer, depending on the die design and the arrangement of extruders (one or more) relative to the die, as is known to those skilled in the art. Polymer granules suitable for film formation are supplied to extruder 530. Extruder 530 subjectes the polymer granules to sufficient heat and pressure to melt the polymer and convey the molten flow through annular die 531.

[0068] The extruder 530 is equipped with a screen pack 532, a breaker plate 533, and a heater 534. The film is extruded between a mandrel 535 and a die 531, and the resulting extrudate is cooled by cold air from an air ring 536. The molten extrudate is immediately blown into blow bubbles 537 to form a molten-oriented film. The molten-oriented film is cooled and solidified as it is conveyed upwards along the length of the bubble 537. After solidification, the film tube is conveyed through a guide roller 538 and folded into a flat configuration by a pressure roller 539. The folded film tube optionally passes through a treater bar 540, then through an idler roller 541, and then around a dancer roll 542 that applies tension control to the folded film tube 543, after which the folded film tube 543 is wound into a roll 544 via a winder 545.

[0069] In one non-limiting embodiment, the multilayer film is a 5-layer symmetrical film, wherein the two outer layers have the same composition and thickness, the two intermediate layers have the same composition and thickness, and a linear tear layer is located between the two intermediate layers. In other non-limiting embodiments, the multilayer film is an asymmetric film.

[0070] orientation

[0071] The membrane can be oriented in the machine direction (i.e., longitudinal), transverse, or both directions (i.e., biaxial orientation), for example to enhance the membrane's strength, optical properties, and durability. The web or tube of the membrane can be uniaxially or biaxially oriented by applying a stretching force at a temperature at which the membrane softens (e.g., above the Vicat softening point; see ASTM 1525) but below the membrane's melting point. The membrane can then be rapidly cooled to retain the physical properties acquired during the orientation process and to provide the membrane with thermal shrinkage characteristics. The membrane can be oriented using, for example, tenter frame processes or bubble processes (double bubble, triple bubble, etc.). These processes are known to those skilled in the art and therefore are not discussed in detail here. The orientation can occur in at least one direction at at least about and / or at most about any of the following ratios: 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 12:1, and 15:1.

[0072] The membrane may have free shrinkage at 212°F (100°C) in at least one direction (e.g., machine orientation or transverse orientation) and / or in both the machine and transverse orientations, with at least about and / or at most about any of the following values: 10%, 15%, 20%, 25%, 30%, 35%, and 40%. The membrane may be annealed or heat-set to slightly or significantly reduce the free shrinkage of the oriented membrane. The free shrinkage of the membrane is determined according to ASTM D 2732, the entire contents of which are incorporated herein by reference, by measuring the percentage change in size in a 10cm x 10cm membrane specimen subjected to selected heat (i.e., exposure at a specified temperature). All free shrinkage mentioned in this application is measured in oil according to this standard. In an embodiment, the membrane has free shrinkage at 100°C in at least one direction (e.g., machine orientation or transverse orientation) and / or in both the machine and transverse orientations, between at least one of the following ranges: 10%-70%, 15%-65%, and 20%-60%.

[0073] The membrane may have at least about and / or at most about any of the following values ​​of free shrinkage at 248°F (120°C) in at least one direction (e.g., machine orientation or transverse orientation) and / or in both the machine and transverse orientations: 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and 90%. The membrane may be annealed or heat-set to slightly or significantly reduce the free shrinkage of the oriented membrane. The free shrinkage of the membrane is determined according to ASTM D 2732, the entire contents of which are incorporated herein by reference, by measuring the percentage change in size in a 10 cm x 10 cm membrane specimen subjected to selected heat (i.e., exposure at a specified temperature).

[0074] In this embodiment, the multilayer heat-shrinkable film exhibits linear tear behavior when a tear is induced in the machine direction. Linear tear behavior is tear propagation along the line of the intended tear path, wherein the film has a reduced deviation from the line of the intended tear path. The film is also capable of being easily torn, allowing the package to be opened without cutting or tools. In this embodiment, the film has a tear initiation of less than 300 gf, less than 250 gf, or less than 200 gf in the machine direction, as measured according to ASTM D-1004.

[0075] Optical properties

[0076] Film transparency (also referred to herein as film clarity) was measured according to ASTM D 1746-97 "Standard Test Method for Transparency of Plastic Sheeting," published in April 1998, the entire contents of which are hereby incorporated by reference. Results are reported herein as "percentage transparency." Using ASTM D 1746-97, the multilayer heat-shrinkable film exhibits at least 65%, or at least 70%, or at least 75%, or at least 80% transparency.

[0077] The film haze value was measured according to ASTM D 1003-00, "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics," published in July 2000, which is incorporated herein by reference in its entirety. Results are reported herein as "percentage haze." Using ASTM D 1003-00, the multilayer heat-shrinkable film may exhibit a haze of less than 8%, or less than 7%, or less than 6%, or less than 5%, or less than 4%.

[0078] The film gloss values ​​were measured according to ASTM D 2457-97 "Standard Test Method for Specular Gloss of Plastic Films and Solid Plastics," published on January 10, 1997, the full text of which is incorporated herein by reference. Results are reported herein as "percentage gloss." Using ASTM D 2457-97, the films exhibit a gloss of 60% to 100% or 70% to 90%.

[0079] Crosslinking

[0080] One or more layers of the membrane—or at least a portion of the entire membrane—may be cross-linked, for example, to improve the membrane's strength or alter its melting or softening properties. Cross-linking can be achieved by using chemical additives or by subjecting one or more membrane layers to one or more energy radiation treatments—such as ultraviolet radiation or ionizing radiation such as X-rays, gamma rays, beta rays, and high-energy electron beams—to induce cross-linking between molecules of the irradiated material. This results in a cross-linked polymer composition. Available ionizing radiation doses include at least about and / or at most about any of the following values: 5, 7, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, 100, 110, 120, 130, and 150 kGy (kilogray). Cross-linking can occur before the orientation process, for example, to enhance the membrane strength prior to orientation, or cross-linking can occur after the orientation process. In the implementation scheme, the entire membrane is cross-linked by an ionizing radiation dose of less than 100, 90, 80, 70, 60 or 50 kGy.

[0081] It may be desirable to avoid irradiating one or more film layers. To do this, one or more layers can be extruded and irradiated, and subsequent layers can then be applied to the irradiated substrate, for example, by extrusion coating. This will produce an extrusion-coated interface in which at least one layer is substantially uncrosslinked.

[0082] Thermoplastic film formation

[0083] The film can be manufactured using thermoplastic film forming processes known in the art. The film can be prepared by extrusion or co-extrusion, using, for example, a tubular trapped bubble film process or a flat film process (i.e., cast film or slot die process). The film can also be prepared by applying one or more layers using extrusion coating, adhesive lamination, extrusion lamination, solvent coating, or by latex coating (e.g., spreading and drying on a substrate). Combinations of these processes can also be used.

[0084] Unless otherwise stated, all references to ASTM programs (and by reference incorporated herein by reference) refer to the most recently published ASTM program up to the date of the priority (i.e., original) application of this patent application with the U.S. Patent and Trademark Office.

[0085] Tear initiation

[0086] A tear initiation point allows for the concentration of manual tearing force on a point or small area of ​​the membrane, enabling tear initiation and propagation to be manually generated. A slit in the membrane can serve as a tear initiation point. Alternatively, the tear initiation point can be a notch, a circular notch, a rectangular notch, a slit orifice, a circular orifice, a pointed elliptical orifice, or a rectangular orifice. Many shapes of slits and notches can be used as tear initiation points. The tear initiation point can be a member of the group consisting of straight slits, curved slits, V-shaped notches, U-shaped notches, and Y-shaped notch-slit combinations. In one embodiment, the tear initiation point is oriented such that the tear can be manually initiated and manually propagated in the direction in which the membrane is extruded (i.e., the machine direction).

[0087] The tear initiation point can be a cut in the film. As used herein, the term "cut" refers to piercing or shearing through the film using a cutting tool or sharpening instrument. The term "cut" includes both slits and notches. As used herein, the term "slit" refers to a cut through the film without separating and removing the film sheet from the packaged article. Slits can originate from the edge of the packaged article (i.e., "edge slit") or inside, i.e., not extending to the edge (i.e., "internal slit," also referred to as "slit opening"). Slits can be straight, curved, or wavy.

[0088] like Figure 3A As shown, the membrane 300 has a tear initiation slit 301. When the membrane 300 and the tear initiation slit 301 are torn, the membrane expands in a linear direction, resulting in... Figure 3B The continuous smooth tear 302 is shown. Figure 4 The image shows a membrane with poor tearing properties. Once the membrane 410 is torn, the tear 410 is non-linear and random. The tear 412 also produces a serrated mark left on the membrane.

[0089] In addition to the tear initiation portion, the packaging article may include a "grip assister," also referred to herein as a "grip enhancement." The grip assister enhances the ease with which the film can be torn. The grip assister can be an aperture in the film, an integral extension of the film, or a separate film tab. The separate film tab can be made of a thermoplastic polymer, paper, or other materials, and can be heat-shrinkable or non-heat-shrinkable. The packaging article may include a combination of tear initiation portions and grip assisters. For example, the film may have a slit as a tear initiation portion and an aperture as a grip assister. The film may have two slits as a pair of tear initiation portions and an aperture between the two slits serving as a grip assister. In embodiments, the grip assister may be a protrusion used in conjunction with the slits.

[0090] The term "hole," as used herein, includes internal perforations (i.e., internal holes) or internal cuts (i.e., internal slits) through a membrane, as well as internal cuts in membrane sheets used to remove membranes from articles of production. The hole may be a straight cut or a curved cut. The hole may be circular, square, rectangular, or irregularly shaped.

[0091] A "notch" is created by cutting a membrane sheet along its originally straight or smoothly curved edge, resulting in a point of stress concentration during the subsequent manual application of tearing force. Notches can be V-shaped, circular, square, rectangular, or elliptical, or have any regular or irregular profile.

[0092] Packaging products

[0093] Turn now Figures 5A-5C An example of a packaged product is shown. Figures 5A-5C The design and arrangement of features illustrated herein are not intended to be limiting, but merely illustrate exemplary embodiments of packaged products encased in film as described herein. Figure 5A As shown, product box 501 is encased in multilayer film 502. The product box is depicted as a cuboid and contains another product inside. It is understood that the product box can be other shapes, including but not limited to spheres, cylinders, ellipsoids, cubes, triangular prisms, pyramids, other geometric shapes, or irregular shapes.

[0094] The membrane includes a pair of tear initiation portions 503 on a first surface 504 of the multilayer membrane 502. The pair of tear initiation portions 503 are spaced apart from each other and located below an upper surface 505 orthogonal to the first surface 504. In one embodiment, the distance from the pair of tear initiation portions to the upper surface is at least 10 mm. In another embodiment, the pair of tear initiation portions are spaced apart from each other by a distance of 5-100 mm. A gripping aid 506 is disposed between the tear initiation portions 503. The gripping aid allows a user to easily grip the membrane and initiate a tear. In another embodiment, the gripping aid is selected from a group consisting of holes in the multilayer membrane, integral extensions of the multilayer membrane, or individual membrane protrusions.

[0095] To open the packaging, force is applied to the gripping aid 506, and the tear line 507 begins to extend from the tear initiation part 503, as... Figure 5B As shown in the figure, the film tears linearly with minimal deviation from the intended tear line 508 (shown as a dashed line). The intended tear line and tear initiation may be positioned along the edge of the packaged product. In other embodiments, and as shown, the intended tear line and tear initiation are spaced apart from the edge of the packaged product.

[0096] As the force continues to pull on the gripping aid 506, the tear line 507 continues until the packaging is opened and the product box 501 can be removed from the multilayer film 502. The tear line may continue through part or all of the first surface 504. In other embodiments, the tear line may continue along the edge of the first surface and continue tearing along the edge of the second surface.

[0097] Methods of manufacturing packaged products

[0098] Methods for packaging products in the films disclosed herein are also considered. First, the product is wrapped in the film. The film can be a centerfold film, a tube, or a rollstock. The open ends or both ends of the film are sealed by known methods, such as heat sealing. Once sealed, the film is subjected to heating to cause it to shrink around the product. The shrinkage removes wrinkles and gives the product a satisfactory appearance. In embodiments, the film shrinks at least any of the following values ​​in at least one of the machine or transverse directions: 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, and 15%.

[0099] The tear initiation section and gripping aid section described herein can be further incorporated into the packaging.

[0100] Example

[0101] Table 1 - Types of resins used in the examples

[0102]

[0103] MB1 is a masterbatch blend of 91.5% by weight of EVA1 with slip agents, anti-blocking agents and lubricants.

[0104] MB2 is a masterbatch blend of 92.3% by weight of EVA1 with a slip agent and an anti-blocking agent.

[0105] Multilayer films are obtained through the above Figure 1 The membrane was prepared using the blow molding extrusion process described and illustrated herein, and a steam generator oven was used instead of a hot water bath 118. The membrane was irradiated at the level shown in parentheses.

[0106] Table 2 - Membranes

[0107]

[0108]

[0109] Various physical properties of the membrane were tested and reported in Table 3 below.

[0110] Table 3 - Membrane Properties

[0111]

[0112] Angle tear deviation test

[0113] The membrane samples were tested according to the angular tear deviation test described below. See also Figures 6A-6B A grid 600 is provided. Each small square is 0.93 mm wide and high. Each main grid mark contains a 10 × 10 portion of the small grid squares. The main grid mark is 9.3 mm in size. It is understood that grids with different units can be used, such as a grid where each square is 1 mm. The desired linear tear path 602 extends at least 13 cm along the Y-axis. The tearing force will be applied to the membrane 601 along an angular tear path 604. The angular tear path 604 deviates from the desired linear tear path 602 by an angle 605 of 26.6°. A 17.8 cm × 17.8 cm square of the membrane 601 is secured to the grid. The membrane is larger than the test area to avoid any edge effects that may affect the measurement. The membrane is secured with a strip 606 extending beyond the membrane, but may also be secured by any suitable means to prevent accidental movement of the membrane. The membrane 601 should be secured at least along a portion of the first edge 607 and the upper surface 608 of the membrane 601. The strip 606 extends along the upper surface 608 until it reaches the line shown as the desired linear tear path 602. A 1 cm slit 609 is cut in the membrane along the desired linear tear path 602 to serve as a tear initiation point. The membrane is oriented such that the desired linear tear path is in the machine direction or transverse direction. The upper surface 608 of the membrane 601 to the right of the desired linear tear path 602 is not fixed to allow tearing of the membrane 601. The membrane is then gripped through the upper surface 608 to the right of the slit 609. A tearing force is then applied by pulling the membrane 601 along the angled tear path 604 until the membrane tears at least the required distance. In the case of the example below, this is 13 cm. The membrane 601 torn along the angled tear path 604 is illustrated in... Figure 6B middle.

[0114] Once membrane 601 has been torn, measurements can be obtained. Now turn to... Figure 7 The membrane exhibits good linear tearing behavior. The remaining portion of the membrane after tearing remains fixed to the grid 600. Markings 620 are made along the tear edge 621 of the remaining membrane 601 after tearing. The membrane 601 prevents markings 620 from appearing on the grid 600. The removed portion of the membrane allows markings 620 to appear on the grid 600. This allows for easy identification of the distance from the tear edge 621 of the membrane 601 to the desired linear tear path 602. Measurements can be taken at each increment 622 to determine the distance from the desired linear tear path 602 to the tear edge 621 identified by markings 620.

[0115] Turn now Figure 8 The membrane 801, which has been torn in the angular tear deviation test, exhibits poor linear tear behavior. Membrane 801 underwent the same angular tear deviation test as membrane 601. Marker 820 provides a visual representation of the tear edge 820 of membrane 801. The tear edge 820 initially approaches the desired linear tear path 602, but rapidly drifts further away as the tear edge 820 extends.

[0116] The angular tear deviation test yielded three measurements to evaluate the linear tear propagation of the membrane reported below. The three measurements are angular tear deviation, average angular tear deviation, and angular tear deviation area, each discussed separately.

[0117] Angular tearing deviation

[0118] Angular tear deviation is a given point on the Y-axis (e.g.) Figure 7 The increment 622 shown is calculated. The angular tear deviation is measured along the X-axis from the desired linear tear path 602 to the tear edge 622. Figure 7 It is calculated based on the distance to the location.

[0119] Angle tear average deviation

[0120] The average deviation of the angular tear is calculated by summing the angular tear deviation values ​​(which are taken in equal increments along the Y-axis) and dividing by the total number of increments. At least 10 increments should be used to ensure good sampling. Increments can be taken every centimeter or even more frequently. Figure 7 As shown, 14 increments were used with an interval of 9.3 mm. The formula for the average deviation of the angular tear reported in Table 4 is as follows:

[0121] Average angular tear deviation = (Angle tear deviation at increment 1 + Angle tear deviation at increment 2 + Angle tear deviation at increment 3 + Angle tear deviation at increment 4 + Angle tear deviation at increment 5 + Angle tear deviation at increment 6 + Angle tear deviation at increment 7 + Angle tear deviation at increment 8 + Angle tear deviation at increment 9 + Angle tear deviation at increment 10 + Angle tear deviation at increment 11 + Angle tear deviation at increment 12 + Angle tear deviation at increment 13 + Angle tear deviation at increment 14) ÷ 14

[0122] Angular tear deviation area

[0123] The angular tear deviation area is an estimate of the total area of ​​the membrane that did not tear along the desired linear tear path. Each increment of tear deviation on the Y-axis is treated as a linear change, even if this is not actually the case. The angular tear deviation area is calculated by summing the estimated areas between each increment. The estimated area between each increment is calculated by multiplying the distance between each increment by the angular tear deviation value taken at that increment. The formula is as follows:

[0124] Angular tear deviation area = (angular tear deviation x increment distance at increment 1) + (angular tear deviation x increment distance at increment 2) + (angular tear deviation x increment distance at increment 3) + (angular tear deviation x increment distance at increment 4) + (angular tear deviation x increment distance at increment 5) + (angular tear deviation x increment distance at increment 6) + (angular tear deviation x increment distance at increment 7) + (angular tear deviation x increment distance at increment 8) + (angular tear deviation x increment distance at increment 9) + (angular tear deviation x increment distance at increment 10) + (angular tear deviation x increment distance at increment 11) + (angular tear deviation x increment distance at increment 12) + (angular tear deviation x increment distance at increment 13) + (angular tear deviation x increment distance at increment 14)

[0125] In an embodiment, the multilayer film, when torn in at least one direction in a machine or in the transverse direction, has a diameter of no more than at least 150 mm. 2 200mm 2 250mm 2 300mm 2 350mm 2 400mm 2 450mm 2 500mm 2 550mm 2 600mm 2 650mm 2 700mm 2 750mm 2 and 800mm 2 The angle of the tear deviates from the area.

[0126] Five samples from membrane 1 were tested using an angular tear deviation test. The increment was 9.3 mm. The average results for the five samples are reported in Table 4 below.

[0127] Table 4 - Tear Data

[0128] Membrane 1 Membrane 3 Membrane 4 Membrane 5 Angular tear deviation at the first increment 0.12mm 0.10mm 0.02mm 0.12mm Angular tear deviation at the second increment 0.22mm 0.30mm 0.02mm 0.18mm Angular tearing deviation at the third increment 0.34mm 0.60mm 0.02mm 0.26mm Angular tear deviation at the 4th increment 0.46mm 0.88mm 0.06mm 0.34mm Angular tear deviation at the 5th increment 0.58mm 1.06mm 0.12mm 0.48mm Angular tear deviation at the 6th increment 0.68mm 1.18mm 0.16mm 0.56mm Angular tear deviation at the 7th increment 0.80mm 1.26mm 0.22mm 0.68mm Angular tear deviation at the 8th increment 0.94mm 1.32mm 0.24mm 0.82mm Angular tear deviation at the 9th increment 1.02mm 1.44mm 0.30mm 0.92mm Angular tear deviation at the 10th increment 1.14mm 1.52mm 0.30mm 1.08mm Angular tear deviation at the 11th increment 1.24mm 1.56mm 0.34mm 1.30mm Angular tear deviation at increment 12 1.36mm 1.56mm 0.34mm 1.44mm Angular tear deviation at the 13th increment 1.46mm 1.5mm 0.36mm 1.64mm Angular tear deviation at increment 14 1.6mm 1.52mm 0.38mm 1.84mm Angle tear average deviation 0.85mm 1.13mm 0.21mm 0.83mm 13cm tear angle tear deviation area <![CDATA[111mm 2 ]]> <![CDATA[147mm 2 ]]> <![CDATA[27mm 2 ]]> <![CDATA[108mm 2 ]]>

[0129] Cuttability was tested by taking a 5-foot sample from the membrane roll. The membrane was folded laterally, the same action as a membrane center folding machine, but done by hand. Since the membrane tested was symmetrical, there was no need to pay attention to misuse or sealing sides.

[0130] The membrane was placed on the SeleCTech machine and operated under the following conditions: end seal temperature set to 230°C; residence time set to 0.8 and pressure set to 0.6 MPa; allowing the SeleCTech machine to reach the appropriate end seal temperature; and placing the folded membrane directly under the end seal strip.

[0131] After the sealing process, check that the membrane remains attached and has not completely detached from the equipment. Small areas of membrane adhesion to the machine are considered a failure and deemed uncut. There is a difference between tack back and incomplete cut, as one is independent of the other. Tack back is a result of applying excessive time or heat to the membrane via the cutting blade or strip.

[0132] Five samples were tested for each membrane. If any of the five samples was incompletely cut, the membrane was considered uncut. If all five samples were cut, the membrane was considered cuttable. Table 5 below indicates "yes" for complete cuts and "no" for incomplete or no cuts.

[0133] Table 5 - Cutting Performance

[0134] membrane 1 2 3 4 5 Cutting yes no no yes yes

[0135] As shown in Table 5, membranes with a tear extension of less than 9 gf in the transverse direction exhibit good cutting performance. Membranes with higher tear extensions in the transverse direction did not cut in the tests described above.

[0136] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any of the included methods. The patentable scope of the invention is defined by the claims, but may include other examples that would occur to a person skilled in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that are not indistinguishable from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A packaged product comprising: a. The primary product; b. A multilayer film that shrinks to the outer surface of the first product; The multilayer film includes: A first outer layer having a first thickness; A second outer layer having a second thickness; and The inner layer comprises a blend of 60-80% by weight polypropylene copolymer and 20-40% by weight ethylene copolymer; A first intermediate layer, disposed between a first outer layer and an inner layer; and The second intermediate layer is disposed between the second outer layer and the inner layer; The thickness of the inner layer is at least 45% of the thickness of the multilayer film; The multilayer film has at least one tear initiation portion to initiate tear propagation of the multilayer film along the tear line; The multilayer film has a diameter of no more than 800 mm when torn in at least one direction, either in a machine or in the transverse direction. 2 The angular tear deviation area is calculated from a 13cm tear using a tear force applied at an angle of 26.6° away from the desired linear tear path and measured according to an angular tear deviation test.

2. The packaging product according to claim 1, wherein the first product is a box containing the second product.

3. The packaged product according to claim 1, wherein the first product is rectangular in shape.

4. The packaging product according to claim 1, wherein the multilayer film comprises a pair of tear initiations on a first surface of the packaging product.

5. The packaging product according to claim 4, wherein the pair of tear initiation portions are spaced at least 10 mm from the upper surface of the packaging product and are disposed on a surface orthogonal to the upper surface of the packaging product.

6. The packaging product according to claim 4 or 5, wherein the pair of tear initiations initiate linear tear propagation in a first plane, and the pair of tear initiations are spaced 5-100 mm apart in a second plane orthogonal to the first plane.

7. The packaging product according to claim 4 or 5, wherein the gripping aid is disposed between the pair of tear initiation portions.

8. The packaging product according to claim 7, wherein the gripping aid is selected from the group consisting of pores in a multilayer film, an integral extension of the multilayer film, and individual film protrusions.

9. The packaging product according to any one of claims 1-5, wherein the multilayer film is a 5-layer symmetrical film.

10. The packaging product according to any one of claims 1-5, wherein the thickness of the inner layer is 45% to 80% of the thickness of the multilayer film.

11. The packaging product according to any one of claims 1-5, wherein the first outer layer is directly adhered to the first surface of the first intermediate layer and the second outer layer is adhered to the first surface of the second intermediate layer, and the second surface of the first intermediate layer is directly adhered to the first surface of the inner layer and the second surface of the second intermediate layer is directly adhered to the second surface of the inner layer.

12. The packaged product according to any one of claims 1-5, wherein the first outer layer comprises at least 50% by weight of an ethylene copolymer.

13. The packaging product of claim 12, wherein the first outer layer further comprises at least 9% by weight of an ethylene / vinyl acetate copolymer.

14. The packaged product according to any one of claims 1-5, wherein the multilayer film has a tear initiation of less than 300 gf in the machine direction as measured according to ASTM D-1004.

15. A multilayer film comprising: a. A first outer layer having a first thickness; b. A second outer layer having a second thickness; and c. Inner layer, comprising a blend of 60-80% by weight polypropylene copolymer and 20-40% by weight ethylene copolymer; d. A first intermediate layer, disposed between the first outer layer and the inner layer; and e. A second intermediate layer, which is disposed between the second outer layer and the inner layer; The thickness of the inner layer is at least 45% of the thickness of the multilayer film; The multilayer film has a diameter of no more than 800 mm when torn in at least one direction, either in a machine or in the transverse direction. 2 The angular tear deviation area is calculated from a 13cm tear using a tear force applied at an angle of 26.6° away from the desired linear tear path and measured according to an angular tear deviation test.

16. The multilayer film according to claim 15, wherein the inner layer is 45% to 75% of the thickness of the multilayer film.

17. The multilayer film according to claim 15 or 16, wherein the multilayer film is a 5-layer symmetrical film.

18. The multilayer membrane according to claim 15 or 16, wherein the multilayer membrane contains 2 to 10% by weight of total vinyl acetate.

19. The multilayer film according to claim 15, wherein the thickness of the inner layer is 45% to 80% of the thickness of the multilayer film.

20. The multilayer film according to claim 15 or 16, wherein the first outer layer is directly adhered to the first surface of the first intermediate layer and the second outer layer is adhered to the first surface of the second intermediate layer, and the second surface of the first intermediate layer is directly adhered to the first surface of the inner layer and the second surface of the second intermediate layer is directly adhered to the second surface of the inner layer.

21. The multilayer film according to claim 15 or 16, wherein the multilayer film comprises at least one layer having a crosslinked polymer composition.

22. The multilayer film according to claim 15 or 16, wherein the multilayer film has a tear initiation of less than 300 gf in the machine direction as measured according to ASTM D-1004.

23. The multilayer film according to claim 15 or 16, wherein the multilayer film has free shrinkage of 10%-70% in at least one direction in the machine direction or transverse direction at 100°C, the free shrinkage being measured according to ASTM D 2732.

24. The multilayer film according to claim 15 or 16, wherein the multilayer film has a haze of less than 5% as measured according to ASTM D 1003 and a transparency of at least 70% as measured according to ASTM D 1746.

25. A method of packaging a product, comprising the following steps: a. Provide the primary product; b. Wrap the first product in a multi-layer film; The multilayer film includes: A first outer layer having a first thickness; A second outer layer having a second thickness; and The inner layer comprises a blend of 60-80% by weight polypropylene copolymer and 20-40% by weight ethylene copolymer; A first intermediate layer, disposed between a first outer layer and an inner layer; and The second intermediate layer is disposed between the second outer layer and the inner layer; The thickness of the inner layer is at least 45% of the thickness of the multilayer film; The multilayer film has a diameter of no more than 800 mm when torn in at least one direction, either in a machine or in the transverse direction. 2 The angular tear deviation area is calculated from a 13cm tear using a tear force applied at an angle of 26.6° away from the desired linear tear path and measured according to an angular tear deviation test. c. Sealing multi-layer film; d. Shrink the multilayer film to make it adhere tightly to the first product.

Images