Longitudinal oriented film for tearing and laminate thereof

Abstract

A multilayer film having a first surface layer of a polyethylene or polypropylene polymer; a tear layer comprising from 70% to 95% by weight of a continuous phase polyethylene polymer and from 5% to 30% by weight of one or more dispersed phase olefin polymers selected from the group consisting of polybutylene, polypropylene, cycloolefin copolymers, EVOH and ionomers; and optionally a second surface layer of a polyethylene or polypropylene polymer. The multilayer film is oriented in the machine direction and is characterized by a ratio of transverse Elmandoff tear strength to longitudinal Elmandoff tear strength of greater than 10. A multilayer film may have a sealing layer added to form a laminate, and the laminate may be used to form a packaging product.

Description

Technical Field

[0001] The present disclosure relates to machine direction oriented multilayer films that exhibit specific machine direction tear properties, laminates containing the multilayer films, and packaged products formed from the laminates. Background Art

[0002] Polymeric films having directional tear properties are useful in applications such as packaging films. Films that tear cleanly, easily, and consistently straight can provide packaging films with a variety of features, such as ventilation features or easy-opening devices. In the past, the tear properties of polymeric films have been manipulated by a variety of means, such as film thickness, film structure, orientation, and scoring.

[0003] As packaging films with high olefin content become desirable from a recycling perspective, the physical properties of packaging films may change. The tear properties may be significantly different because olefin polymers are not suited to having low tear resistance. In addition, many olefin polymers are more difficult to laser score than polar polymers, further complicating the incorporation of tear features into packaging films and packaging.

[0004] The orientation of polymeric films can affect mechanical properties such as puncture strength, COF, stiffness and tear resistance. Specifically, longitudinal orientation has been used to reduce the tear resistance of the film in the longitudinal direction. When combined with conventional low seal initiation temperature sealant films, HDPE-rich films that have been longitudinally oriented can have reduced longitudinal tear strength, but not low enough to cause linear tearing. Significant reductions in tear resistance have been achieved by adding inorganic additives to longitudinally oriented films. However, these films often suffer from appearance problems due to haze caused by cavitation. In addition, the tear may remain jagged in feel and appearance. Summary of the invention

[0005] Disclosed herein are multilayer films, laminated films including the multilayer films, and packaging products formed from the laminated films. Each of these articles benefits from corresponding specific elements in terms of polyolefin / polyethylene content, directional tear properties, and haze properties. Various combinations of these excellent features have not been demonstrated in the prior art.

[0006] The multilayer film described herein comprises a first surface layer comprising polyethylene or polypropylene polymer and a tear layer. The tear layer comprises a continuous phase polyethylene polymer in the range of 70% to 95% by weight, and one or more dispersed phase olefin polymers in the range of 5% to 30% by weight, the dispersed phase olefin polymer being selected from the group consisting of polybutene, polypropylene, cyclic olefin copolymer, EVOH and ionomer. The thickness of the tear layer is in the range of 60% to 90% of the total thickness of the multilayer film. The multilayer film is oriented in the longitudinal direction, and the ratio of the transverse Elmendorf tear strength (Elmendorf tearstrength) of the multilayer film to the longitudinal Elmendorf tear strength of the multilayer film is greater than 10, and the Elmendorf tear strength is measured according to ASTM D1922.

[0007] Some embodiments of the multilayer film have a first surface layer comprising a density of 0.918 g / cm 3 Up to 0.970g / cm 3 A polyethylene or polypropylene homopolymer within the range.

[0008] The multilayer film may also include a second surface layer comprising a polyethylene or polypropylene polymer. The second surface layer may include a density of 0.918 g / cm 3 Up to 0.970g / cm 3 A polyethylene or polypropylene homopolymer within the range.

[0009] In some embodiments of the multilayer film, the continuous phase polyethylene polymer of the tear layer is a medium density polyethylene. In some embodiments of the multilayer film, the continuous phase polyethylene polymer has a melt flow index less than or equal to 3.0 g / 10 min according to ASTM D1238 (190° C. / 2.16 kg).

[0010] The multilayer film may have free shrink values ​​of less than 10% in the machine and transverse directions when tested according to ASTM D2732 using a bath temperature of 90°C.

[0011] Some embodiments of the multilayer film may have tear properties wherein the ratio of transverse Elmendorf tear to longitudinal Elmendorf tear is greater than 20. Some embodiments will have a haze of less than 15% when measured according to ASTM D1003.

[0012] The multilayer film may have an overall composition comprising a polyolefin content in the range of 95 wt% to 100 wt%.The overall composition of the multilayer film may comprise a polyethylene content in the range of 85 wt% to 100 wt%.

[0013] Some embodiments of the multilayer film may have a total thickness in the range of 0.75 mil (19.1 micrometers) to 3.5 mils (88.9 micrometers), a first surface layer comprising high density polyethylene and having a thickness in the range of 5 volume % to 20 volume % of the total thickness, a second surface layer comprising high density polyethylene and having a thickness in the range of 5 volume % to 20 volume % of the total thickness, and a tear layer located between the first surface layer and the second surface layer. The tear layer includes a continuous phase medium density polyethylene or a continuous phase high density polyethylene in the range of 70 weight % to 95 weight %, and one or more dispersed phase olefin polymers in the range of 5 weight % to 30 weight %, the dispersed phase olefin polymer being selected from the group consisting of polybutene, polypropylene, cyclic olefin copolymer, EVOH and ionomer. The multilayer film is oriented in the machine direction, and the ratio of the transverse Elmendorf tear strength of the multilayer film to the longitudinal Elmendorf tear strength of the multilayer film is greater than 10, and the Elmendorf tear strength is measured according to ASTM D1922.

[0014] Some laminate films disclosed herein include a multilayer film and a seal layer selected from one of a heat seal coating or a cold seal blend. The seal layer can be coextensive with the multilayer film or patterned relative to the multilayer film.

[0015] Other laminated films disclosed herein include a multilayer film, a sealing film including a sealing layer, and an adhesive layer between the multilayer film and the sealing film. The adhesive layer may be in direct contact with the multilayer film and the sealing film. When the multilayer film is separated from the sealing film, the bonding strength measured using ASTM F904 is greater than 200 g / in.

[0016] In some embodiments of the laminated film, the sealing film has a normalized peak load impact strength of less than 0.5 N / micrometer according to ASTM D7192. The laminated film may have a normalized peak load impact strength in the range of 10 N / mil to 15 N / mil (0.39 N / micrometer to 0.59 N / micrometer) according to ASTM D1792.

[0017] Some embodiments of the laminated film have a longitudinal Elmendorf tear value of less than 150 g and a ratio of the transverse Elmendorf tear strength of the multilayer film to the longitudinal Elmendorf tear strength of the multilayer film greater than 2, the Elmendorf tear strength being measured according to ASTM D1922. The laminated film may further include a line of weakness in at least one of the multilayer film and the sealing film. The laminated film may be free of a line of weakness.

[0018] The laminated film may have an overall composition comprising a polyolefin content in the range of 95 to 100 wt%.The laminated film may have an overall composition comprising a polyethylene content in the range of 90 to 100 wt%.

[0019] Also discussed herein are packaging products made using the laminated film and having at least one seal bonding the sealing layer to itself and a tear initiating feature. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present disclosure may be more fully understood by considering the following detailed description of various embodiments of the present disclosure in conjunction with the accompanying drawings, in which:

[0021] Figure 1 is a cross-sectional view of one embodiment of a multilayer film;

[0022] Figure 2 is a cross-sectional view of one embodiment of a multilayer film;

[0023] Figure 3A and 3B is a cross-sectional view of an embodiment of a tear layer;

[0024] Figure 4 is a cross-sectional view of one embodiment of a laminated film;

[0025] Figure 5 is a plan view of a sealing layer side of an embodiment of a laminated film;

[0026] Figure 6 is a perspective view of an embodiment of a packaging product including a laminated film;

[0027] Figure 7 is a cross-sectional view of one embodiment of a laminated film;

[0028] Figure 8 is a front view of an embodiment of a packaging product including a laminated film; and

[0029] Fig. 9 is a plan view of the front side of an embodiment of a packaging product including a laminated film.

[0030] The accompanying drawings show some but not all embodiments. The elements depicted in the drawings are illustrative and are not necessarily drawn to scale, and the same (or similar) reference numerals represent the same (or similar) features throughout the drawings. DETAILED DESCRIPTION

[0031] Multilayer machine direction oriented (MDO) films are described herein, which include high polyolefin content and excellent machine direction tear properties. The design of the structure relies on a combination of film structure, layer composition and film orientation to achieve surprising results. Laminates including tearable MDO films are also described herein, and the tear properties of the laminates are also beneficial to the tear properties. The films disclosed herein can be used in many applications, including packaging. Many types and various packaging forms of packaged products can benefit from excellent tear properties, such as those that require easy ventilation or easy opening features. When a portion of the package is torn open, the packaged product can show excellent quality, thereby providing low effort and visually pleasing opening for the package.

[0032] It has been advantageously discovered that in order to obtain excellent longitudinal tear properties (clean, no flutter, shoelaces or webbing) on ​​a multilayer polyolefin film, it is necessary not only to reduce the tear propagation resistance in the longitudinal direction (reducing MD tear resistance), but also to increase the tear propagation resistance in the transverse direction (increasing TD tear resistance). This imbalance in tear properties is achieved by creating a tear layer with a two-phase blend of slightly immiscible polymers and subjecting the film to longitudinal orientation. Unexpectedly, the resulting film was found to have very low longitudinal tear resistance and higher transverse tear resistance while maintaining very low haze. The resulting film is highly desirable because it not only allows easy longitudinal tearing, but also has a premium appearance with minimal stretching along tear propagation and very low haze.

[0033] definition

[0034] As used herein, the term "layer" refers to a building block of a film or laminate of a structure that is a single material type, a uniform blend of materials, or a dispersed blend of materials. A layer can be a single polymer, a blend of materials within a single polymer type, or a blend of various polymers, can contain a metallic material, and can have additives. A layer can be continuous with the film (i.e., coextensive with the film) or can be discontinuous or patterned. A layer has an insignificant thickness (z direction) compared to the length and width (xy direction), and is therefore defined as having two major surfaces, whose area is limited by the length and width of the layer. An outer layer is a layer that is connected to another layer only at one of the main layer surfaces. In other words, one major surface of the outer layer is exposed. An inner layer is a layer that is connected to another layer at two major surfaces. In other words, the inner layer is between two other layers. A layer may have a sublayer.

[0035] Similarly, as used herein, the term "film" refers to a web constructed of layers and / or films, all of which are adjacent and connected to each other. The film can be described as having a thickness that is not significant compared to the length and width of the film. The film is generally considered to have two main surfaces relative to each other that extend in length and width. As used herein, a "laminate" is a film that can be constructed of an unlimited number of films and / or layers, which are bonded together by any known method, such as but not limited to coextrusion, coating or lamination, to form a composite product.

[0036] The term "package" is used herein to describe an article that can contain an object (ie, a product) that is formed by bonding one or more laminates or other packaging components to itself or to each other around the perimeter to form a package interior space.

[0037] As used herein, the terms "outer layer", "external film", "surface layer" or "surface film" are used to describe a film or layer located on one major surface of a film or laminate comprising it. As used herein, the terms "inner layer" or "inner film" are used to describe a film or layer that is not located on the surface of a film comprising it. An inner film or layer is adjacent to another film or layer on both sides.

[0038] As used herein, the term "seal layer" is a film layer located on an outer surface that provides adhesion to another surface. The seal layer may contain a material suitable for forming a heat seal, such as a low seal temperature polymer. The seal layer may contain a material that forms a seal under pressure alone, i.e., a cold seal blend.

[0039] As used herein, a "dispersed phase" is a portion of a blended system containing at least two phases that is divided into smaller portions and distributed throughout a "continuous phase." The continuous phase is typically interrupted only by the dispersed phase. As used in this application, the dispersed phase and the continuous phase are both polymeric in nature and slightly immiscible such that they do not form a completely uniform blend throughout the layer.

[0040] As used throughout this application, the term "copolymer" refers to a polymer product obtained by the polymerization or copolymerization of at least two monomeric species. The term "copolymer" also includes polymerizations of three, four or more monomeric species having reaction products known as terpolymers, tetrapolymers, etc. As used throughout this application, the term "homopolymer" refers to a polymer product obtained by the polymerization of a single monomeric species.

[0041] As used herein, the term "polyolefin" or "olefin polymer" includes polymers derived from olefin monomers.

[0042] As used throughout this application, unless otherwise specified, the term "polyethylene" or "PE" refers to an ethylene homopolymer or copolymer. Such ethylene copolymers include copolymers of ethylene and other units or groups, such as vinyl acetate, acid groups, acrylate groups or other. The term "polyethylene" or "PE" is used regardless of the presence or absence of substituent branched groups. Polyethylene includes, for example, medium density polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, ethylene alpha-olefin copolymers, ethylene vinyl acetate, ethylene acid copolymers, ethylene acrylate copolymers, cycloolefin copolymers or their blends. Various polyethylene polymers can be recycled as regenerated polyethylene or regenerated polyolefins.

[0043] As used throughout this application, the term "high density polyethylene" or "HDPE" refers to (a) a polyethylene having a density of about 0.960 g / cm 3 To about 0.970g / cm 3 and (b) a density of about 0.940 g / cm 3 To about 0.960g / cm 3 Copolymers of ethylene and α-olefins (typically 1-butene or 1-hexene) of the type described herein. High-density polyethylene includes polymers made with Ziegler or Phillips type catalysts and polymers made with single-site metallocene catalysts. High-density polyethylene may be bimodal and may be pre-nucleated. As used throughout this application, the term "medium density polyethylene" (MDPE) refers to a polymer having a density of about 0.926 g / cm 3 To about 0.940g / cm 3 Ethylene homopolymers and copolymers.

[0044] As used throughout this application, unless otherwise specified, the term "polypropylene" or "PP" refers to a propylene homopolymer or copolymer. Such propylene copolymers include copolymers of propylene with at least one alpha-olefin and copolymers of propylene with other units or groups. The term "polypropylene" or "PP" is used without regard to the presence or absence of substituent branching groups or other modifiers. Polypropylene includes, for example, homopolymer polypropylene, polypropylene impact copolymers, polypropylene random copolymers, etc. Various polypropylene polymers can be recycled as recycled polypropylene or recycled polyolefins.

[0045] As used herein, "polybutene", "PB-1" or "polybutene-1" refers to a saturated polymer represented by the following general formula: [(CH2CH(CH3)) n ].

[0046] As used throughout this disclosure, the term "cyclic olefin copolymer" refers to a polymer produced by copolymerization of a cyclic monomer with ethylene. Examples of cyclic olefin copolymers include ethylene norbornene copolymers. The properties of cyclic olefin copolymers, such as T g (glass transition temperature), can vary widely based on the monomer content.

[0047] As used throughout this application, the term "ethylene vinyl alcohol copolymer", "EVOH copolymer" or "EVOH" refers to a copolymer composed of repeating units of ethylene and vinyl alcohol. Ethylene vinyl alcohol copolymer can be represented by the following general formula: [(CH2-CH2) n -(CH2-CH(OH))] n . Ethylene vinyl alcohol copolymers may include saponified or hydrolyzed ethylene vinyl acetate copolymers. EVOH refers to vinyl alcohol copolymers having ethylene comonomers and prepared by, for example, hydrolysis of vinyl acetate copolymers or by chemical reaction with vinyl alcohol. Ethylene vinyl alcohol copolymers may contain 28 mol % (or less) to 48 mol % (or more) ethylene.

[0048] As used throughout this application, "ionomer" refers to the ionized or partially ionized form of a copolymer of ethylene and acrylic acid or methacrylic acid, wherein the neutralizing cation may be any suitable metal ion, such as zinc or sodium.

[0049] The term "adhesive layer" or "tie layer" refers to a layer or material placed on one or more layers to promote adhesion of the layer to another surface. For example, a tie layer can be positioned between two layers of a multilayer film to maintain the two layers in place relative to each other and prevent undesired delamination. In another example, an adhesive layer can be positioned between two films of a laminate to maintain the two layers in place relative to each other and prevent undesired delamination.

[0050] As used herein, layers or films that are "directly in contact" or "immediately adjacent" to each other have no intervening materials therebetween.

[0051] The packaging described herein includes parts formed by the laminate of multilayer film.Laminate and packaging can be recyclable.As used herein, the term "recyclable" is intended to reflect that the material can be easily processed in the recycling process of accepting "full polyethylene" products or "full polyolefin" products.Generally, these recycling processes can accept some low-level pollutant materials.Therefore, as used herein, recyclable refers to packaging or laminates with very high levels of polyethylene and low levels of acceptable pollutants.The total composition defined by the weight of the material defines the recyclability of the packaging film.As described herein, the "total composition" of multilayer film, laminate or packaged product refers to all parts except the actual product in the package, including panels, zippers and any other additional parts.The total composition of multilayer film, laminate or packaging can independently include polyolefins in the range of 80% by weight to 100% by weight or polyolefins in the range of 90% by weight to 100% by weight.In certain embodiments, the total composition of multilayer film, laminate laminate or packaging is independently greater than 80% by weight, or greater than 85% by weight, or greater than 90% by weight, or greater than 95% by weight polyolefins. The total composition of the multilayer film, laminate or package can each independently include polyethylene in the range of 85 wt % to 100 wt %, or 95 wt % to 100 wt %. In some embodiments, the total composition of the multilayer film, laminate or package is each independently greater than 85 wt %, greater than 90 wt % or greater than 95 wt % polyethylene.

[0052] As described herein, the multilayer film is longitudinally oriented. Orientation can be the result of uniaxial orientation (longitudinal) stretching of the film, increasing the longitudinal dimension and subsequently reducing the thickness of the material. After the film is heated to a temperature just below the melting temperature of the polymer in the film, the film is subjected to a tensile force. In this way, stretching "orients" the polymer chains, thereby changing the physical properties of the film. At the same time, stretching makes the film thinner. The resulting oriented film is thinner and can have significant changes in mechanical properties such as toughness, heat resistance, stiffness, tear strength and barrier properties. Orientation is generally achieved by using an MDO method using a heated roller. Typical blown film coextrusion processes do impart some stretching to the film, but are not sufficient to be considered as oriented as described herein. The oriented film can be heat-set (i.e., annealed) after orientation so that it is relatively stable in size and has low free shrinkage under high temperature conditions that may be experienced during the conversion (i.e., printing or lamination) of the multilayer film or during the use (i.e., heat sealing) of the resulting laminate.

[0053] The films described herein are produced by a variety of methods, all of which include long spans of relatively narrow webs. The films are processed by winding the films into rolls. As used herein, reference to "machine direction" or "longitudinal direction" is along the relatively long web path of this type of production process. Reference to "transverse direction" or "cross direction" is perpendicular to the machine direction along the relatively short web width.

[0054] A number of standard test procedures are referenced herein to characterize the disclosed films and comparative materials. These test methods are incorporated herein by reference: ASTM D1922-09 "Standard Test Method for Propagation Tear Resistance of Plastic Film and Thin Sheeting by Pendulum Method" describes the Elmendorf tear test; ASTM D1238-10 "Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer" describes the measurement of melt index or melt flow rate; ASTM D2732-03 "Standard Test Method for Unrestrained Linear Thermal Shrinkage of Plastic Film and Sheeting" describes the measurement of free shrink; ASTM D1003-07 "Standard Test Method for Haze and Luminous Transmittance of Transparent Plastics" describes a procedure for measuring haze; ASTM F904 "Standard Test Method for Comparison of Bond Strength or Ply Adhesion of Simally Laminates Made From Flexible Materials" describes a procedure for measuring laminate bond strength; and ASTM D7192 "Standard Test Method for Comparison of Bond Strength or Ply Adhesion of Simally Laminates Made From Flexible Materials" describes a procedure for measuring laminate bond strength. for High Speed ​​Puncture Properties of Plastic Films Using Load and Displacement Sensors” describes a procedure for measuring peak load impact strength and related properties.

[0055] Multilayer film

[0056] Figure 1 A cross-sectional view of an embodiment of a multilayer film 10 is shown. The multilayer film 10 has a first surface layer 12 and a tear layer 14. Figure 2 Another embodiment of the multilayer film 10 ′ is shown, which now includes a second surface layer 16 .

[0057] As described, the first surface layer 12 and the second surface layer 16 are located at the relative major surfaces of the multilayer film. The first surface layer and the second surface layer may have the same composition or different compositions. Each of the first surface layer and the second surface layer contains a polyethylene polymer or a polypropylene polymer. In some embodiments, the first surface layer and / or the second surface layer comprises a density greater than 0.926 g / cm 3 In some embodiments, the first surface layer and / or the second surface layer is made of a polyethylene (i.e., MDPE or HDPE) with a density greater than 0.926 g / cm 3 In some embodiments, the first surface layer and / or the second surface layer comprises a polypropylene homopolymer. In some embodiments, the first surface layer and / or the second surface layer consists of a polypropylene homopolymer.

[0058] The thickness of each of the first surface layer and / or the second surface layer may be in the range of 0.05 mil (1.25 microns) to 0.40 mil (10.2 microns) or 0.10 mil (2.5 microns) to 0.40 mil (10.2 microns). The thickness of each of the first and / or second surface layers may be in the range of 5% to 20% of the total thickness of the multilayer film. The thickness of the tear layer may be in the range of 0.4 mil (10.2 microns) to 2.8 mil (71.1 microns) or 0.8 mil (20.3 microns) to 2.8 mil (71.1 microns). The thickness of the tear layer may be in the range of 60% to 90% of the total thickness of the multilayer film.

[0059] like Figure 2 As shown in , if a second surface layer is present, the tear layer is located between the first surface layer and the second surface layer. Each of the first surface layer, the tear layer, and the second surface layer (if present) is coextensive with the multilayer film. The tear layer is a polymer blend comprising a continuous phase including a polyethylene polymer in the range of 70 wt % to 95 wt % and a dispersed phase olefin polymer in the range of 5 wt % to 30 wt %. The tear layer can be composed of a continuous phase polyethylene polymer and a dispersed phase olefin polymer.

[0060] The polyethylene polymer of the continuous phase polymer can be a medium density polyethylene (MDPE), such as a linear medium density polyethylene (LMDPE). In some embodiments of the multilayer film, the continuous phase polymer can be a polyethylene having a melt flow index less than or equal to 3.0 g / 10 min or less than or equal to 1.0 g / 10 min measured according to ASTM D1238 using 190°C / 2.16 kg.

[0061] The dispersed phase olefin polymer can be polybutene, polypropylene, cycloolefin copolymer, EVOH or ionomer. The dispersed phase olefin copolymer should be selected so that it is slightly immiscible with the continuous phase polymer. If a small dispersed portion is not formed during melt blending and the tear layer is a uniform blend, a more incompatible combination should be selected. If the haze level of the multilayer film is too high during orientation, cavitation may occur, and a more compatible combination should be selected. For example, if the dispersed phase olefin polymer used is a cycloolefin copolymer, the miscibility of the blend can be adjusted by selecting a polymer whose glass transition temperature is closer to the continuous phase to obtain better miscibility, or by selecting a polymer whose glass transition temperature is further away from the continuous phase to adjust the miscibility to obtain less miscibility. In another example, EVOH with a higher ethylene content may be more miscible with the continuous phase.

[0062] Some embodiments of the multilayer film may include additional layers. For example, the multilayer film may contain a thin oxygen barrier layer comprising a barrier polymer such as EVOH or polyamide. The multilayer film may include other functional layers such as a tie layer or a moisture barrier. Additional layers, particularly layers containing non-olefin polymers, should be minimized so that they do not disrupt the tear properties and / or recyclability of the film.

[0063] Ideally, the multilayer film is produced by combining all layers simultaneously by coextrusion. Alternatively, the layers of the multilayer film can be combined by other known methods, including but not limited to extrusion coating, extrusion lamination and adhesive lamination. Each layer of the multilayer film should be combined before the multilayer film is oriented. In other words, each layer should be subjected to the same orientation process at the same time.

[0064] The multilayer film of the present disclosure is a longitudinal oriented film. In some embodiments, the multilayer film is oriented only in the longitudinal direction and is not oriented to any significant amount in the transverse direction. The film can be oriented by any known method and to any extent so that the dispersed phase olefin polymer is elongated, as will be discussed. For the embodiments described herein, a longitudinal orientation level in the range of 2X to 8X may be suitable. In some embodiments, a longitudinal orientation of 3X to 6X may be suitable. In addition to orientation, the multilayer film should be annealed so that when tested according to ASTM D2732 using a bath temperature of 90°C, the free shrinkage value of the film in the longitudinal and transverse directions is less than 10%. When tested according to ASTM D2732 using a bath temperature of 90°C, the free shrinkage of the multilayer film in the longitudinal and transverse directions may be less than 9%, less than 8%, less than 7%, less than 6%, less than 5%, less than 4%, less than 3%, less than 2% or less than 1%. The multilayer film may have a final total thickness (after orientation) ranging from 0.75 mils (19.1 micrometers) to 3.5 mils (88.9 micrometers), or from 1 mil (25.4 micrometers) to 3 mils (76.2 micrometers).

[0065] Advantageously, upon orientation, the blend of tear layers such as Figure 3A and Figure 3B As shown, Figure 3A shows a cross section of an embodiment of a tear layer prior to orientation 14A, Figure 3B A cross section of an embodiment of a tear layer after orientation 14 is shown, as may be found in an embodiment of a multilayer film. For reference, the machine direction is shown by the double-headed arrow between the two figures. Prior to orientation, the tear layer 14A has a continuous phase 14B and a dispersed phase 14C. After orientation in the machine direction, the tear layer 14 has a continuous phase 14B and a dispersed phase 14C. Of note is the elongation of the dispersed phase in the machine direction. This deformation of the dispersed phase is critical to improving tear properties.

[0066] Without being limited by the proposed theory, the inventors believe that the composition and orientation of the tear layer have several different effects on tear propagation. First, tearing becomes easier because propagation may tend to follow more easily along the interface between the phases. The slight immiscibility of these phases means that they can be separated more easily when a force such as tearing is applied. The orientation brings some of the dispersed parts closer to each other and stretches the phase interface in the longitudinal direction, both of which have the effect of reducing the total force required for tear propagation. In addition, the elongation of the dispersed phase has a directional effect, particularly increasing the tendency of propagation to travel in the longitudinal direction and reducing the tendency of propagation to travel in the transverse direction. It should be noted that the dispersed phase blend does not affect the tearing properties of the unoriented film.

[0067] Additionally, it was surprisingly found that by adding the dispersed phase to the tear layer and orienting the film, a significant increase in haze was avoided. Typically, dispersed "contamination" type additions to the oriented layer will increase haze due to even a small amount of cavitation or separation of the dispersed and continuous phases.

[0068] The multilayer film has a haze level of less than 15% when measured according to ASTM D1003. Some embodiments of the multilayer film have a haze level of less than 14%, less than 12%, less than 10%, less than 8%, or less than 6%. This multilayer film can have a much lower haze level than other polyethylene-rich machine direction oriented films designed for MD tearing.

[0069] Due to the design of the film structure and layer composition as described herein, the multilayer film has excellent longitudinal tear characteristics. When tearing is initiated with a notch, the multilayer film has extremely easy and clean tear propagation in the longitudinal direction. The tear resistance is very low in the longitudinal direction and very high in the transverse direction. The ratio of the Elmendorf Tear value measured in the transverse direction to the Elmendorf Tear value measured in the longitudinal direction is greater than 10, greater than 20, greater than 30, greater than 40, or greater than 50.

[0070] Laminate

[0071] The multilayer films described herein have excellent longitudinal tear properties and low haze and can be used in many applications, including laminated films for packaging. In some cases, the multilayer film will have a sealant as part of its structure (i.e., the second surface layer is sealable). In this case, the multilayer film including the sealant is considered to be a "laminate" and can be used to form packaging. In other embodiments, a sealant and / or other additional layers can be added to the multilayer film to form a laminated film.

[0072] As described above, the oxygen or moisture barrier layer can be part of the multilayer film. In other embodiments, the barrier layer can be added to another part of the laminated film including the multilayer film. For example, a coating can be deposited on the surface of the multilayer film, such as a vacuum deposited SiOx layer or a solution coated EVOH layer. In other embodiments, a sealing film containing a barrier layer as will be described can be laminated to the multilayer film.

[0073] In some embodiments of the laminated film including the multilayer film, the exposed surface of the multilayer film (i.e., the first surface layer) is covered with a heat-resistant overprint varnish or paint. The overprint varnish may cover the entire exposed surface of the multilayer film, or it may be patterned. Preferably, this varnish layer is transparent and very thin, adding little additional rigidity to the overall structure. In addition, the laminated film may include printed indicia on either or both surfaces of the multilayer film, thereby providing graphics for the entire film and packaging.

[0074] The sealing layer added to the laminate film may have a composition that allows a heat seal to be formed, thereby forming an airtight sealed package. As used herein, the term "heat seal", "heat sealable" or "heat sealable" refers to two or more surfaces that have been or can be combined together by applying both heat and pressure. Heat sealing is a well-known and commonly used method for producing packaging, and is familiar to those skilled in the art. Without wishing to be bound by theory, during heat sealing, the sealing layer softens due to the application of heat, thereby allowing the formation of a heat seal bond. Since heat must be driven through the entire laminate film to raise the temperature of the sealable material, it is advantageous if the heat seal layer softens and seals at a relatively low temperature. A lower seal initiation temperature (SIT) can achieve a faster packaging line speed. For example, some embodiments of the laminate film may include a sealing layer that exhibits a SIT of less than or equal to 110°C, less than or equal to 100°C, or less than or equal to 90°C.

[0075] The laminate film may include a patterned sealant layer as a surface layer. As used herein, the term "patterned" means that the sealable material layer is discontinuous with the multilayer film. The sealant layer is discontinuous with the multilayer film to which it is applied. The patterned sealant layer may be applied to the area of ​​the laminate film involved in closing the package by sealing. The sealant layer may be applied to greater than or equal to 5%, greater than or equal to 10%, or greater than or equal to 15% of the surface of the multilayer film. The sealant layer may be applied to less than or equal to 30%, less than or equal to 25%, or less than or equal to 20% of the multilayer film.

[0076] Embodiments of the laminate film 100 including the patterned sealing layer 55 are Figure 4 and Figure 5 Shown in. Figure 4 is a cross-sectional view of a laminate film 100 including a multilayer film 10 and a sealant layer 55. As shown, the sealant layer 55 is discontinuous with the laminate (ie, is not continuous with the multilayer film). Figure 5 is a plan view of the laminate, showing a surface including a sealant layer 55 (hash marked area). Also visible on this surface are areas of the multilayer film 10 that are not covered by the sealant layer 55. The corners of the laminate film 100 have been turned up to show that the opposite surface of the laminate film 100 includes the multilayer film 10, and specifically, the first surface layer 12 of the multilayer film 10.

[0077] Possible heat sealable materials for use in the sealing layer may include, but are not limited to, acrylate copolymers, PET, PE, PP or hot melts (wax based). These may be applied as a thin coating over the entire surface of the laminate or in a pattern.

[0078] The patterned sealing layer may alternatively be composed of a pressure-sensitive cold seal material. This embodiment of the laminated film is advantageous because the formation of the package does not require heating. Without intending to be bound by theory, the pressure-sensitive cold seal may be advantageous for the packaging of heat-sensitive products (e.g., ice cream or chocolate). Embodiments of the laminated film may include a pressure-sensitive cold seal system, including but not limited to natural or synthetic polyisoprene latex or styrene-butadiene copolymer latex. The cold seal material may include a blend including acrylates and / or tackifiers.

[0079] The patterned sealing layer can allow a hermetic seal to be applied in a thickness that allows for even challenging applications such as triple point region sealing. In some embodiments, the patterned sealing layer can be greater than or equal to 1 g / m 2 Or greater than or equal to 3g / m 2 In other embodiments, the sealant layer may be less than or equal to 8 g / m 2 , less than or equal to 9g / m 2 Or less than or equal to 10g / m 2 For example, the sealing layer may have a basis weight of about 1 g / m 2About 10g / m 2 In the range of about 3g / m 2 About 9g / m 2 within the range.

[0080] The continuous sealing layer may be applied to the multilayer film at a thickness that allows a hermetic seal. In some embodiments, the continuous sealing layer may be greater than or equal to 1 g / m 2 Or greater than or equal to 3g / m 2 In other embodiments, the sealant layer may be less than or equal to 8 g / m 2 , less than or equal to 9g / m 2 Or less than or equal to 10g / m 2 For example, the sealing layer may have a basis weight of about 1 g / m 2 About 10g / m 2 In the range of about 3g / m 2 About 9g / m 2 within the range.

[0081] As used herein, the term "basis weight" is used to refer to the amount of material by weight present in a predetermined area of ​​a film or layer. Typically, the defined area is a square meter, but any area can be used. The area is defined in the length-width (i.e., xy direction) of the film or layer. A material of a given thickness (z direction) and density has a specific weight when covering a defined area (i.e., square meters). Materials applied in discontinuous layers (e.g., patterned sealing layers) can be defined by basis weight. In the case of a pattern, basis weight refers to the amount of material by weight present when covering a defined area.

[0082] A thin sealing layer (e.g., a heat seal lacquer or a patterned cold seal) applied directly to the multilayer film or only interposed with a primer is very advantageous because it generally does not overly adversely affect the tear properties of the multilayer film. A laminated film consisting of a multilayer film, a sealing layer, and optional printed markings and varnishing will retain nearly all of the advantages of the multilayer film, including excellent tear properties and very low haze. In some embodiments, the laminate consists of a multilayer film and a sealing layer. In some embodiments, the laminate consists of a multilayer film, a printed graphic (marking), and a sealing layer.

[0083] The sealing layer may be added to the multilayer film by adhesive lamination of the sealing film to form a laminated film. Figure 7A cross section of an embodiment of a laminated film 100' is shown, the laminated film comprising a multilayer film 10, a sealing film 50 and an adhesive layer 30 therebetween. The sealing film 50 comprises a sealing layer 55. The sealing film 50 may be a single layer, in which case the sealing film 50 consists of the sealing layer 55). The sealing film 50 may be multilayer, including a sealing layer 55 located at an exposed surface of the laminate. The sealing film may be a coextruded blown film, comprising a sealing layer, a laminating layer (i.e., a layer attached to the adhesive layer), and optionally one or more barrier layers and / or tie layers.

[0084] The thickness of the sealing film may be 1 mil (25.4 microns) to 4 mils (101.6 microns) or 1 mil (25.4 microns) to 3 mils (76.2 microns). The sealing film may be produced by a blown film or cast film process. The sealing film may be oriented or unoriented, although the sealing function generally benefits from the lack of orientation. The sealing film should have a normalized peak load impact strength of less than 0.5 N / micron.

[0085] The adhesive layer of laminate plays an important role in optimizing the tearing characteristics of laminate. The adhesive layer can include any typical type of adhesive for film lamination, including those utilizing water-based chemistry, solvent-based chemistry, energy curing or solvent-free chemistry. The key factor is to obtain strong bonding with both multilayer film and sealing film. Strong bonding ensures that the tear strength of laminate remains relatively low. The bonding achieved by the adhesive layer should be greater than 200g / in, greater than 300g / in or greater than 500g / in. Lower bond strength causes the webbing of laminate, poor tear quality and high tear strength.

[0086] Sealing film should be designed to meet the overall goal of achieving excellent longitudinal tearing. A good predictor of easy tearing properties is low puncture strength. Sealing film can have a normalized peak load impact strength less than 0.5N / micron, less than 0.4N / micron or less than 0.3N / micron. In general, if the laminate has a normalized peak load impact strength less than 30N / mil (1.18N / micron), less than 20N / mil (0.79N / micron), less than 15N / mil (0.59N / micron) or less than 10N / mil (0.39N / micron) measured according to ASTM D7192, it is advantageous. Laminate should have a normalized peak load impact strength greater than 2N / mil (0.08N / micron), greater than 5N / mil (0.20N / micron) or greater than 10N / mil (0.39N / micron).

[0087] Due to the design of the laminated film structure as described herein and the inclusion of the multilayer film, the laminated film has excellent longitudinal tearing properties. When tearing is initiated with a notch, the laminated film has extremely easy and clean tear propagation in the longitudinal direction. The tear resistance is very low in the longitudinal direction and very high in the transverse direction. The longitudinal Elmendorf Tear value can be in the range of 1g to 100g, in the range of 2g to 50g, in the range of 5g to 25g, or in the range of 5g to 15g. The ratio of the Elmendorf Tear value measured in the transverse direction to the Elmendorf Tear value measured in the longitudinal direction is greater than 2, greater than 3, greater than 4, or greater than 5.

[0088] Weak lines or "weakened lines" may be present in one or more layers / films of a laminated film. In some embodiments, the weakened lines are mechanically formed. In other embodiments, the weakened lines may be formed by laser scoring (i.e., laser scored weakened lines). The weakened lines may be discontinuous (i.e., perforated) or continuous. The weakened lines may be partially or completely formed in one or more layers of a multilayer film or sealing film. In some embodiments, there are multiple weakened lines extending parallel to each other in a single laminated film. Particularly advantageous embodiments may include weakened lines that pass through part or all of the sealing film, and the multilayer film does not include weakened lines. The weakened lines may guide tearing in the longitudinal direction in whole or in part, and may or may not reduce tear resistance. In some embodiments, the laminate may be free of weakened lines.

[0089] Packaging products

[0090] Advantageously, the laminated film discussed herein can be used as a packaging film for packaging products. The packaging product can include one or more embodiments of the laminated film, plus other components, such as trays, cups, zippers, accessories and other types of films. The packaging portion of the packaging product can be formed by sealing. The sealing layer of the laminated film is attached to another surface, such as another sealing layer of itself or another component, by a sealing process. The sealing process can be, but is not limited to, heat sealing, ultrasonic sealing or cold sealing. Ideally, the sealing is completed in the following manner: the packaging is hermetically sealed and the product therein is protected from environmental influences.

[0091] In some embodiments, the sealing layer of the laminated film acts as a caulking agent. In some embodiments, the sealing layer flows into the gap of the triple point region (described below) under sealing conditions. It is not intended to be bound by theory, and the ability to properly seal the triple point can be produced by a combination of material properties, coating weight and sealing conditions. It is believed that having a relatively thick sealing layer in the heat seal area greatly increases the possibility of reducing the size of the triple point region of the seal. In one or more preferred embodiments, the sealing layer is not oriented.

[0092] An embodiment of a packaging product 500 formed using the laminated film 100 is Figure 6. The style of the packaged product 500 is a standard flow wrap, wherein the laminate film 100 is folded into a tubular shape around a product (not shown), and a fin seal 200 is formed in the longitudinal direction of the laminate film 100 along the length of the package, and a transversely oriented seal 200 forms the end of the package. A triple point seal 400 is formed at the intersection of the fin seal and the end seal. The sealing layer of the laminate film 100 faces the interior of the package (i.e., in contact with the product therein) and the multilayer film of the laminate film 100 faces the exterior of the package (i.e., exposed to the environment). This type of packaging can be advantageously made with a patterned sealing layer, but any type of laminate film can be used.

[0093] Another embodiment of a packaging product 500' that can be formed using the laminated film 100' includes Figure 8 . Herein, the laminate is folded and sealed (see seal 200), including the bottom gusset, with the longitudinal direction of the laminate film 100' running from left to right through the pouch, as shown. The pouch is then filled with product (not shown) and an additional seal 200 is formed on the top. In this way, the pouch can benefit from the laminate film because the top of the pouch can be cleanly torn off, providing easy opening.

[0094] As previously discussed, the laminated film may include a line of weakness. A line of weakness may be present in one or more laminates of a packaged product. A line of weakness may be continuous, spanning from one side edge of a pouch or package to another side edge of a pouch or package, or it may be discontinuous. In some embodiments, there are multiple lines of weakness extending parallel to each other in a single laminated film. Fig. 9 A particularly advantageous embodiment of a packaged product 500" in the form of a pouch or sachet is shown. Here, the packaged product 500" comprises a weakening line 350 in the laminate film 100' forming the front panel and a weakening line in the laminate film forming the back panel (not shown). Each weakening line spans the front panel or the back panel. In some embodiments, the packaged product may not contain a laminate comprising a weakening line.

[0095] The packaged product 500" further includes a tear initiator 300. As used herein, a "tear initiator" is a feature that helps initiate manual tearing of the film. An example of a tear initiator can be a cut or notch within the seal area 200 of the sealed package 500" (i.e., an area where a small portion of the film has been removed). In some embodiments, a line of weakness can be used as a tear initiator. Ideally, the tear initiator 300 is aligned or closely aligned with the line of weakness 350. Some embodiments of the packaged product include one or both of a tear initiator and a line of weakness.

[0096] Packaged products including laminated films as described herein can benefit from excellent tearing properties. Tearing the package in the direction following the longitudinal direction of the laminate will result in low effort tearing (low tear strength), straight tearing, and clean tearing without stretching the laminate film. Packaged products can benefit from these excellent tearing properties without the use of weakening lines. Packaged products will also benefit from low haze laminates, allowing the entire package and product to have a better appearance.

[0097] Examples and data

[0098] Multilayer films 1, 2, 3, 4, 5, 6, 7 and 8 were produced by a blown film coextrusion process and have the composition and structure shown below. In all examples of films given herein, unless otherwise stated, % is by weight, slashes ( / ) show layer interfaces, and the materials in parentheses are physical blends in which the minor component exists as a dispersed phase. Multilayer films 1 to 8 are not oriented and therefore do not represent the inventive multilayer films described herein and are included for comparative purposes.

[0099] Multilayer Film 1 has a total thickness of 5.5 mils (139.7 microns) and a structure of [15% HDPE / 70% (85% mLMDPE+15% PP copolymer) / 15% HDPE]. The total composition of Multilayer Film 1 includes 100 wt% polyolefin and 89.5 wt% polyethylene.

[0100] Multilayer Film 2 had a total thickness of 5.5 mils and a structure of [15% HDPE / 70% (85% mLMDPE+15% PP homopolymer) / 15% HDPE]. The total composition of Multilayer Film 2 included 100 wt% polyolefin and 89.5 wt% polyethylene.

[0101] Multilayer Film 3 had a total thickness of 5.5 mils and a structure of [15% HDPE / 70% (95% mLMDPE+5% PB copolymer) / 15% HDPE].Multilayer Film The total composition of Multilayer Film 3 included 100 wt% polyolefin and 89.5 wt% polyethylene.

[0102] Multilayer Film 4 had a total thickness of 5.5 mils and a structure of [15% HDPE / 70% (85% mLMDPE+15% PB copolymer) / 15% HDPE]. The total composition of Multilayer Film 4 included 100 wt% polyolefin and 89.5 wt% polyethylene.

[0103] Multilayer Film 5 had a total thickness of 5.5 mils and a structure of [15% HDPE / 70% (85% mLMDPE+15% PB homopolymer) / 15% HDPE]. The total composition of Multilayer Film 5 included 100 wt% polyolefin and 89.5 wt% polyethylene.

[0104] The multilayer film 6 had a total thickness of 5.5 mils and a structure of [15% HDPE / 70% (95% mLMDPE+5% COC1) / 15% HDPE]. The total composition of the multilayer film 6 included 100% by weight polyolefin and 100% by weight polyethylene.

[0105] Multilayer Film 7 had a total thickness of 5.5 mils and a structure of [15% HDPE / 70% (95% mLMDPE+5% COC2) / 15% HDPE]. The total composition of Multilayer Film 6 included 100% by weight polyolefin and 100% by weight polyethylene.

[0106] Multilayer Film 8 had a total thickness of 5.5 mils and a structure of [15% HDPE / 70% mLMDPE / 15% HDPE].The total composition of Multilayer Film 6 included 100 wt% polyolefin and 100 wt% polyethylene.

[0107] In multilayer films 1 to 8, the HDPE used has a viscosity of 0.958 g / cm 3 The density and melt index of 0.45 g / 10 min (190 ° C / 2.16 kg) of the mMDPE used have a melt index of 0.935 g / cm 3 The density and melt index of 0.50g / 10min (190℃ / 2.16kg) of PP copolymer are 0.90g / cm 3 The PP homopolymer is a nucleated polymer with a melt index of 2 g / 10 min (230 ° C / 2.16 kg), and the PB copolymer is a random copolymer of butene-1 and ethylene with a density of 0.906 g / cm 3 The melt index is 1g / 10min (190℃ / 2.16kg). PB homopolymer is a semi-crystalline polymer with a density of 0.914g / cm 3 The melt index is 0.4 g / 10 min (190 ° C / 2.16 kg), COC1 is a cycloolefin copolymer with a density of 1.02 g / cm 3 The glass transition temperature is 78°C, and COC2 is a cyclic olefin copolymer with a density of 1.02 g / cm 3 And the glass transition temperature is 140° C. These polymer names are also used in other examples.

[0108] Multilayer Films 1 through 7 were further processed by off-line machine direction orientation to produce corresponding Multilayer Films 1A through 7A, which represent the inventive multilayer films described herein. The films were oriented 5.5X to give a film thickness of approximately 1.0 mil (25.4 microns).

[0109] Additionally, multilayer film 8 was similarly oriented in the machine direction. However, corresponding film 8A did not include a dispersed phase within the interior layer. Thus, multilayer film 8A is not representative of the multilayer films of the present invention but is included for comparative purposes.

[0110] The tear properties of multilayer films 1 to 8 and 1A to 8A are shown in Table 1. Tear properties were measured according to ASTM D1922. The data collected included Elmendorf tear values ​​in the machine direction (MD) and the transverse direction (TD). For each film and tear direction, ten data points were collected, and the average Elmendorf tear values ​​are shown in Table 1. The calculated tear ratios are also given in Table 1, calculated using the average value (average TD tear / average MD tear). The pendulum weight used for the test is also shown in Table 1.

[0111] Table 1: Elmendorf tear values ​​measured according to ASTM D1922, and calculated tear ratio (TD / MD)

[0112]

[0113]

[0114] Although multilayer films 1 to 8 are not oriented, it is observed that adding dispersed phase to the core layer as in multilayer films 1 to 7 does not significantly reduce the tear resistance of the film. Compared with multilayer film 8 without dispersed phase olefin polymer, the tear value is almost the same. In addition, all multilayer films 1 to 8 have a tear value ratio (TD / MD) of 1.5 to 1.9. The added dispersed phase does not increase the ratio of the transverse tear value to the longitudinal tear value. In other words, compared with the film without dispersed phase olefin polymer, the added dispersed phase olefin polymer does not increase the tendency of the film to tear in the longitudinal direction, rather than tear in the transverse direction.

[0115] After the introduction of longitudinal orientation, each of the multilayer films 1A to 8A exhibited lower tear resistance in both the transverse and longitudinal directions. This can generally be attributed to the reduced thickness of the film compared to the unoriented films 1 to 8. However, longitudinal orientation has a greater impact on longitudinal tear resistance. Analysis of the tear ratio (TD / MD) (4.3) of multilayer film 8A shows a substantial increase due to longitudinal orientation. The effect of the dispersed phase olefin polymer on the tear ratio is significant, increasing to a range of 12.7 to 64.8.

[0116] The haze of oriented multilayer films 1A to 8A was also measured according to ASTM D1003, and the results are shown in Table 2. These results indicate that the addition of dispersed phase olefin polymer and subsequent longitudinal orientation does not cause voiding greater than 200 nm in the tear layer. gThe multilayer film 7A with COC of 100% tantalum begins to show increased haze, indicating that some cavitation occurs. This indicates that this is at the edge of the intent of the currently disclosed multilayer films. The present disclosure includes the use of dispersed phase olefin polymers in the tear layer that are dissimilar enough to produce a dispersion, but not so dissimilar that they separate from the main component under the stress of orientation. Possibly, the COC of multilayer film 7A does not soften during the orientation process and therefore does not flow with the main component and produce some slight cavitation and haze. The current films disclosed herein are intended to increase the tear ratio without significantly changing the haze level.

[0117] Table 2: Haze values ​​measured according to ASTM D1003

[0118] Multilayer film Haze(%) 1A 12.6 2A 11.5 3A 13.0 4A 11.9 5A 12.7 6A 10.9 7A 21 8A 10.9

[0119] Several laminates (Laminates A, B, C, D, E, F and G) were produced to analyze the tear properties of the inventive films. Each laminate was produced by bonding the MDO film to the sealing film using an adhesive lamination process, and the final structure of the film is shown below. Laminates A, B, C and E are comparative laminates, and laminates D, F and G are in accordance with the inventive laminates described herein.

[0120] Laminate A has a 1 mil MDOPE film laminated to a 2.5 mil white sealing film. The MDOPE film has a structure of 10% HDPE / 10% (HDPE+mLMDPE) / 60% mLMDPE / 10% (HDPE+mLMDPE) / 10% HDPE. The adhesive was applied at approximately 1.3 lb / rm dry weight and was a solvent-based epoxy amine type. The sealing film was a 2.5 mil blown film with a structure of 29% LLDPE / 42% (HDPE+white concentrate) / 29% mLLDPE.

[0121] Laminate B had a similar structure as Laminate A, with the same MDOPE film and the same sealant film. The adhesive was applied at about 1.7 lb / rm dry weight and was a water-based adhesive.

[0122] Laminate C also had a similar structure to Laminate B. MDOPE was a 0.9 mil MDO HDPE film. The sealing film and adhesive were the same as used in Laminate B.

[0123] Laminate D has a 1 mil MDO film (5:1 stretch) with a structure of 15% HDPE / 70% (90% mLMDPE + 10% PB copolymer) / 15%. Laminate D uses the same adhesive and sealant film as Laminate B. The total composition of Laminate D includes 96.8 wt% polyolefin and 95 wt% polyethylene.

[0124] Laminate E used the same MDO film as Laminate D. The laminate was prepared using approximately 1 lb / rm of solventless adhesive. The sealant film was a 2.5 mil blown film with a structure of 19% LLDPE / 62% (LLDPE+white concentrate) / 19% LLDPE.

[0125] Laminate F used the same MDO film and adhesive as Laminate E and the same sealant film as Laminate A. The overall composition of Laminate F included 98.1 wt% polyolefin and 96.2 wt% polyethylene.

[0126] The tear data of the laminated films were collected in the same manner as the multilayer laminates. The laminate tear data are shown in Table 3.

[0127] Table 3: Elmendorf tear values ​​measured according to ASTM D1922, and calculated tear ratio (TD / MD)

[0128]

[0129] Peak load impact strength was measured on laminates B, C and D. Data were collected according to ASTM D7192. Note that ASTM D7192 is used for films with a thickness of less than 10 mils, while ASTM D3763 is used for films with a thickness of more than 10 mils, although the tests are essentially the same. Data were collected using a 0.25 inch probe, which was pointed to the MDO film side of each laminate. The results reported in Table 4 are the averages of five samples for each laminate sample. The thickness of the film used to calculate the peak load was determined by measuring each laminate sample ten times.

[0130] Table 4: Peak load impact strength and normalized peak load measured according to ASTM D7192

[0131]

[0132] To successfully develop an easy tear structure, all elements in the structure must be considered. Starting with an easy tear printed web does not always lend itself to an easy tear structure if the sealant is too tear resistant. Ideally, the sealant should have a machine direction Elmendorf tear value of less than 400 g, less than 200 g, or less than 100 g.

[0133] Multilayer Film Examples

[0134] A. A multilayer film comprising:

[0135] a first surface layer comprising a polyethylene or polypropylene polymer; and

[0136] a tear layer comprising a continuous phase polyethylene polymer in the range of 70 wt% to 95 wt% and one or more dispersed phase olefin polymers in the range of 5 wt% to 30 wt%, the dispersed phase olefin polymers being selected from the group consisting of polybutene, polypropylene, cyclic olefin copolymers, EVOH, and ionomers, the tear layer having a thickness in the range of 60% to 90% of the total thickness of the multilayer film; and

[0137] wherein the multilayer film is oriented in a machine direction; and

[0138] The multilayer film has a ratio of a transverse Elmendorf tear strength to a longitudinal Elmendorf tear strength of the multilayer film of greater than 10, the Elmendorf tear strength being measured according to ASTM D1922.

[0139] B. A multilayer film according to any other multilayer film embodiment, wherein the first surface layer comprises a density of 0.918 g / cm 3 Up to 0.970g / cm 3 A polyethylene or polypropylene homopolymer within the range.

[0140] C. The multilayer film according to any other multilayer film embodiment, further comprising a second surface layer comprising a polyethylene or polypropylene polymer.

[0141] D. The multilayer film according to embodiment C, wherein the second surface layer comprises a density of 0.918 g / cm 3 Up to 0.970g / cm 3 A polyethylene or polypropylene homopolymer within the range.

[0142] E. The multilayer film according to any other multilayer film embodiment, wherein the continuous phase polyethylene polymer is a medium density polyethylene.

[0143] F. The multilayer film according to any other multilayer film embodiment, wherein the continuous phase polyethylene polymer has a melt flow index less than or equal to 3.0 g / 10 min according to ASTM D1238 (190° C. / 2.16 kg).

[0144] G. The multilayer film according to any other multilayer film embodiment further comprises a free shrink value of less than 10% in both the machine direction and the transverse direction when tested according to ASTM D2732 using a bath temperature of 90°C.

[0145] H. The multilayer film according to any other multilayer film embodiment, wherein the ratio of transverse Elmendorf tears to longitudinal Elmendorf tears is greater than 20.

[0146] I. The multilayer film according to any other multilayer film embodiment, wherein the haze is less than 15% when measured according to ASTM D1003.

[0147] J. The multilayer film according to any other multilayer film embodiment, further comprising a total composition comprising a polyolefin content in a range of 95 wt % to 100 wt %.

[0148] K. The multilayer film according to any other multilayer film embodiment, further comprising a total composition comprising a polyethylene content in a range of 85 wt % to 100 wt %.

[0149] L. A multilayer film comprising:

[0150] A total thickness in the range of 0.75 mils (19.1 micrometers) to 3.5 mils (88.9 micrometers); a first surface layer comprising high density polyethylene, the thickness of the first surface layer being in the range of 5 volume % to 20 volume % of the total thickness;

[0151] a second surface layer comprising high-density polyethylene, the second surface layer having a thickness ranging from 5 volume % to 20 volume % of the total thickness; and

[0152] a tear layer between the first surface layer and the second surface layer, the tear layer comprising in the range of 70 wt % to 95 wt % of a continuous phase medium density polyethylene or a continuous phase high density polyethylene, and in the range of 5 wt % to 30 wt % of one or more dispersed phase olefin polymers selected from the group consisting of polybutene, polypropylene, cyclic olefin copolymer, EVOH, and ionomers; and

[0153] wherein the multilayer film is oriented in a machine direction; and

[0154] The multilayer film has a ratio of a transverse Elmendorf tear strength to a longitudinal Elmendorf tear strength of the multilayer film of greater than 10, the Elmendorf tear strength being measured according to ASTM D1922.

[0155] Laminated Film Examples

[0156] M. A laminate film comprising any of the multilayer film embodiments and a seal layer selected from one of a heat seal coating or a cold seal blend.

[0157] N. The laminate film of embodiment M, wherein the seal layer is coextensive with the multilayer film.

[0158] O. The laminate film of embodiment M, wherein the sealing layer is patterned relative to the multilayer film.

[0159] P. A laminated film comprising:

[0160] Any multilayer film embodiment;

[0161] a sealing film comprising a sealing layer; and

[0162] An adhesive layer is located between the multi-layer film and the sealing film.

[0163] Q. A laminate film according to embodiment P, wherein:

[0164] The adhesive layer is in direct contact with the multilayer film;

[0165] The adhesive layer is in direct contact with the sealing film; and

[0166] When the multilayer film is separated from the sealing film, the bond strength as measured using ASTM F904 is greater than 200 g / in.

[0167] R. The laminate film according to embodiment P or Q, wherein the sealing film has a normalized peak load impact strength of less than 0.5 N / micrometer according to ASTM D7192.

[0168] S. The laminate film of embodiment P, Q or R, further comprising a normalized peak load impact strength in the range of 10 N / mil to 15 N / mil (0.39 N / micrometer to 0.59 N / micrometer) according to ASTM D1792.

[0169] T. The laminated film according to any other laminated film embodiment, further comprising:

[0170] A longitudinal Elmendorf tear value of less than 150 g; and

[0171] A ratio of the cross-machine direction Elmendorf tear strength of the multilayer film to the machine direction Elmendorf tear strength of the multilayer film of greater than 2, the Elmendorf tear strength being measured according to ASTM D1922.

[0172] U. The laminate film of embodiment P, Q, R, S or T, further comprising a line of weakness in at least one of the multilayer film and the sealing film.

[0173] V. The laminated film according to any other laminated film embodiment, further comprising a total composition comprising a polyolefin content in a range of 95 wt % to 100 wt %.

[0174] W. The laminated film according to any other laminated film embodiment, further comprising a total composition comprising a polyethylene content in a range of 90 wt % to 100 wt %.

[0175] Packaging product examples

[0176] X. A packaging product comprising any of the laminate film embodiments, wherein at least one seal bonds the seal layer to itself and to the tear initiating feature.

Claims

1. A multilayer film comprising: a first surface layer comprising a polyethylene or polypropylene polymer; and a tear layer comprising a continuous phase polyethylene polymer in the range of 70 wt% to 95 wt% and one or more dispersed phase olefin polymers in the range of 5 wt% to 30 wt%, the dispersed phase olefin polymers being selected from the group consisting of polybutene, polypropylene, cyclic olefin copolymers, EVOH, and ionomers, the tear layer having a thickness in the range of 60% to 90% of the total thickness of the multilayer film; and wherein the multilayer film is oriented in a machine direction; and The multilayer film has a ratio of a transverse Elmendorf tear strength to a longitudinal Elmendorf tear strength of the multilayer film of greater than 10, the Elmendorf tear strength being measured according to ASTM D1922.

2. The multilayer film of claim 1, wherein the first surface layer comprises a density of 0.918 g / cm 3 Up to 0.970g / cm 3 A polyethylene or polypropylene homopolymer within the range.

3. The multilayer film of claim 1, further comprising a second surface layer comprising polyethylene or polypropylene polymer.

4. The multilayer film of claim 3, wherein the second surface layer comprises a density of 0.918 g / cm 3 Up to 0.970g / cm 3 A polyethylene or polypropylene homopolymer within the range.

5. The multilayer film of claim 1 wherein the continuous phase polyethylene polymer is a medium density polyethylene.

6. The multilayer film of claim 1, wherein the continuous phase polyethylene polymer has a melt flow index less than or equal to 3.0 g / 10 min according to ASTM D1238 (190°C / 2.16 kg).

7. The multilayer film of claim 1 further comprising a free shrink value of less than 10% in both the machine direction and the transverse direction when tested according to ASTM D2732 using a bath temperature of 90°C.

8. The multilayer film of claim 1, wherein a ratio of the transverse Elmendorf tear to the longitudinal Elmendorf tear is greater than 20.

9. The multilayer film of claim 1, wherein the haze is less than 15% when measured according to ASTM D1003.

10. The multilayer film of claim 1, further comprising a total composition comprising a polyolefin content in the range of 95 wt% to 100 wt%.

11. The multilayer film of claim 1, further comprising a total composition comprising a polyethylene content in the range of 85 wt% to 100 wt%.

12. A multilayer film comprising: Total thickness ranging from 0.75 mils (19.1 microns) to 3.5 mils (88.9 microns); a first surface layer comprising high-density polyethylene, the first surface layer having a thickness ranging from 5% to 20% of the total thickness; a second surface layer comprising high-density polyethylene, the second surface layer having a thickness ranging from 5% to 20% of the total thickness; and a tear layer between the first surface layer and the second surface layer, the tear layer comprising in the range of 70 wt % to 95 wt % of a continuous phase medium density polyethylene or a continuous phase high density polyethylene, and in the range of 5 wt % to 30 wt % of one or more dispersed phase olefin polymers selected from the group consisting of polybutene, polypropylene, cyclic olefin copolymer, EVOH, and ionomers; and wherein the multilayer film is oriented in a machine direction; and The multilayer film has a ratio of a transverse Elmendorf tear strength to a longitudinal Elmendorf tear strength of the multilayer film of greater than 10, the Elmendorf tear strength being measured according to ASTM D1922.

13. A laminated film comprising the multilayer film according to claim 1 and a seal layer selected from one of a heat seal coating or a cold seal blend.

14. The laminate film of claim 13, wherein the sealant layer is coextensive with the multilayer film.

15. The laminate film of claim 13, wherein the sealing layer is patterned relative to the multilayer film.

16. A laminated film comprising: The multilayer film according to claim 1 or 12; a sealing film comprising a sealing layer; and An adhesive layer is located between the multilayer film and the sealing film.

17. The laminate film according to claim 16, wherein: The adhesive layer is in direct contact with the multilayer film; The adhesive layer is in direct contact with the sealing film; and When the multilayer film is separated from the sealing film, the bond strength as measured using ASTM F904 is greater than 200 g / in.

18. The laminate film of claim 16, wherein the sealing film has a normalized peak load impact strength of less than 0.5 N / micrometer according to ASTM D7192.

19. The laminate film of claim 16, further comprising a normalized peak load impact strength in the range of 10 N / mil to 15 N / mil (0.39 N / micrometer to 0.59 N / micrometer) according to ASTM D1792.

20. The laminate film according to claim 16, further comprising: A longitudinal Elmendorf tear value of less than 150 g; and A ratio of the cross-machine direction Elmendorf tear strength of the multilayer film to the machine direction Elmendorf tear strength of the multilayer film of greater than 2, the Elmendorf tear strength being measured according to ASTM D1922.

21. The laminate film of claim 16, further comprising a line of weakness in at least one of the multilayer film and the sealing film.

22. The laminate film according to claim 13 or claim 16, further comprising a total composition comprising a polyolefin content in the range of 95 wt% to 100 wt%.

23. The laminate film according to claim 13 or claim 16, further comprising a total composition comprising a polyethylene content in the range of 90 wt% to 100 wt%.

24. A packaging product comprising the laminate film of claim 13 or claim 16 wherein at least one seal bonds the seal layer to itself and to a tear initiating feature.

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