Heat resistant recycle-ready retort packaging

Abstract

To provide a flexible laminated packaging film that can be used in retorted product applications, having the important advantage of being recyclable in a polyolefin recycling stream.SOLUTION: Provided is a laminated polypropylene-based film suitable for retort packaging, having an exterior film, a barrier layer, and a sealing layer. The retort packaging film has a total composition including high levels of polyolefin-based polymers and polypropylene-based polymers, such that the material can be processed efficiently in a polypropylene recycling process. Advantageously, the film retains the properties required to suitably withstand the retort process and produce a high-quality shelf-stable packaged product.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present disclosure relates to film structures, specifically retortable packaging films and packaged products made therefrom. The packaging films described herein may be recyclable in polyolefin-based processes. [Background technology]

[0002] Pasteurization operations (i.e., retort) are used for the sterilization and thermal processing of food or other products held within components of hermetically sealed packaging material. The food or other product is packed and sealed within a retortable package, such as a pouch, and transferred to an autoclave apparatus where it is subjected to temperatures generally above the boiling point of water for an extended period of time. The autoclave process also uses excess pressure to complete the sterilization step.

[0003] Specialized flexible packaging films are used for applications that make products that are shelf-stable or sterilized using an autoclave sterilization process. Commercially available shelf-stable products such as pre-cooked rice, moist pet food, or tuna are available in flexible packaging formats such as stand-up pouches, lidded trays, or flow-wraps. The packaged products can be stored at ambient conditions for months or years, depending on the barrier of the packaging film.

[0004] Flexible packaging films used for in-pack sterilization often have many different layers, with each layer contributing one or more critical attributes required for high demand applications. For example, a packaging film may require high stiffness and high heat resistance to perform well in high speed packaging processes. The packaging film must be able to withstand the high temperature and pressure changes of the sterilization process without losing seal integrity or becoming unattractive in appearance.

[0005] A typical flexible packaging film for sterile product applications may contain a combination of materials such as polyester or polyamide, which provide good heat resistance, dimensional stability, and stiffness, aluminum foil, which provides high barrier and stiffness, and / or polyolefins, which provide suitable sealing properties. Unfortunately, when this wide variety of materials is combined into a single packaging film, the film becomes difficult to recycle. Summary of the Invention [Problem to be solved by the invention]

[0006] Described herein is a flexible laminated packaging film that can be used in retort product applications, with the important advantage of being recyclable in the polyolefin recycle stream. Despite having a composition with a high polyolefin content, the retort packaging film retains properties that enable it to perform well in high speed packaging operations and withstand sterilization cycles while retaining good appearance, excellent barrier properties and hermetic integrity. [Means for solving the problem]

[0007] The retort packaging film described herein has an outer polypropylene-based film, a barrier layer and a sealing layer. The retort packaging film has a total composition including at least 80% by weight of a polyolefin-based polymer. The retort packaging film has a total composition including at least 80% by weight of a polypropylene-based polymer.

[0008] In some embodiments, the retort packaging film further comprises an inner polypropylene-based film. One or both of the inner and outer polypropylene-based films may be oriented.

[0009] A preferred embodiment of the retort packaging film has a barrier layer containing a metal or inorganic oxide that is deposited on either the outer or inner polypropylene-based film surface.

[0010] In certain embodiments, the sealing layer of the retort packaging film is part of a multi-layer film that also has a backing layer. The sealing layer is subjected to a 1 second dwell time and a 440 N / 15 cm 2 When sealed at a pressure of 100° C., the outer polypropylene-based film can be heat sealed to itself at a sealing temperature of 130° C. In some cases, this sealing performance is achieved when the sealing layer contains a polypropylene copolymer having a melting temperature of 135° C. or less. Ideally, the outer polypropylene-based film and the sealing layer are essentially free of polymers other than polyolefins.

[0011] The retort package may be formed from one or more retort packaging films.

[0012] In terms of retort packaging, it is made from a retort packaging film having a total composition with at least 80% polyolefin-based material. 3 / m 2 Less than 1.0 cm 3 / m 2 The barrier layer has an oxygen permeability of less than 1000 nm.

[0013] Also disclosed herein is a shelf-stable packaged product, comprising a retort packaging film having at least 80% polypropylene-based polymer and a product hermetically sealed within the retort packaging film.

[0014] Also disclosed herein is a method of making a shelf-stable packaged product, the method comprising the steps of forming an initial package by heat sealing a retort packaging film to itself using a sealing temperature of 160° C. or less, filling the initial package with the product, heat sealing the initial package to completely enclose the product in the final package, and subjecting the final package to an autoclave process.

[0015] The present disclosure will be more fully understood upon consideration of the following detailed description of various embodiments of the disclosure in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic side view of an embodiment of a retort packaging film. [Diagram 2] 1 is a schematic side view of an embodiment of a retort packaging film. [Diagram 3] 1 is a schematic side view of an embodiment of a retort packaging film. [Figure 4] 1 is a schematic side view of an embodiment of a retort packaging film. [Diagram 5] FIG. 1 is a plan view of an embodiment of a retort package. [Figure 6] FIG. 1 is a top view of an embodiment of a shelf-stable packaged product. [Figure 7] 1 is a process diagram of an embodiment of a method for producing a shelf-stable packaged product. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The drawings show some, but not all, embodiments, and elements depicted in the drawings are for illustrative purposes and are not necessarily drawn to scale, with the same (or similar) reference numerals referring to the same (or similar) features throughout the drawings.

[0018] Current flexible retort packaging films contain a number of different materials designed to provide high performance in demanding applications. The structures generally comprise layers including polyester, polyamide, polyethylene, polypropylene, metal and / or ethylene vinyl alcohol copolymers. Each layer of the structure is designed to provide properties such as barrier, stiffness, heat resistance, dimensional stability, puncture resistance, seal strength, and visual appeal, to name a few. The stringent functionality requirements of retort packaging and the material diversity of current structures pose great challenges when wishing to provide more sustainable packaging solutions, solutions that are recyclable.

[0019] As disclosed herein, retort packaging film structures have been designed that include high levels of polyolefin-based materials, specifically high levels of polypropylene-based materials, and yet the structures retain all the required attributes of barrier, heat resistance, appearance and seal integrity, despite eliminating many of the materials commonly used in retort packaging.

[0020] Advantageously, the structure lends itself to easy recycling.

[0021] Specifically, the retort packaging film structure has a design in which the heat seal initiation temperature of the sealing layer is low enough to accommodate only moderate heat resistance of the outer surface. Even though the sealing layer now has a relatively low softening point, the sealing layer still has sufficient integrity to survive the high temperatures of the retort sterilization process along with other abuses that the package may endure during shipping and use. The retort packaging film can be formed into a retort package at a lower sealing temperature and retains excellent appearance. Furthermore, even after the film is formed into a package, stuffed, hermetically sealed, and subjected to a retort sterilization process, the package structure maintains excellent barrier properties and appearance.

[0022] The retort packaging film described herein contains at least 80% by weight of a polyolefin-based polymer and at least 50% by weight of a polypropylene-based polymer. Materials that are not polyolefin-based polymers are minimized. The outside of the packaging film has a heat-resistant polypropylene-based film. The inside of the packaging film has a sealing layer that is a polypropylene-based blend of polymers. The retort packaging film contains a barrier layer that is generally not a polyolefin-based material. The film can also have other materials such as adhesives and inks.

[0023] Using the packaging film structural design elements described herein, a recyclable packaging film can be achieved. The film is suitable for recycling in a polyolefin-based recycling process due to its high polyolefin content. Also, the film is suitable for recycling in a polypropylene-based recycling process due to its high polypropylene content. Specifically, the film can have low amounts or essentially no materials such as polyester, polyamide, chlorine-containing polymers and aluminum foil. Preferably, the retort packaging film does not contain aluminum foil. As used herein, "aluminum foil" is a metal web having a thickness of at least 1 micron, typically greater than 5 microns. The film can contain non-polyolefin-based polymers, such as those used in the adhesive layer or ink layer, but these are minimized and generally less than 10% by weight of the total composition. The film can contain non-polymeric materials such as barrier materials, but these are minimized and generally less than 10% by weight of the total composition.

[0024] Retort packaging film Described herein are retort packaging films and laminated polypropylene-based films suitable for retort packaging, and retort packages and shelf-stable packaged products made therefrom. As used herein, a "retort packaging film" or "retort package" is a film, or a package made from a film, that can remain hermetically sealed after being stuffed, sealed, and subjected to a typical retort sterilization process. A typical retort sterilization is a batch process using temperatures of about 100°C to about 150°C, overpressures up to about 70 psi (483 kPa), and can have durations from minutes to hours. Common retort processes used for products packaged in flexible films include steam or immersion in water. Food or other products packaged in retort packaging films and retort sterilized can be stored at ambient conditions for extended periods of time (i.e., shelf-stable) and retain sterility. Because the retort process is very hard, highly specialized flexible packaging films are designed to withstand the process.

[0025] Various types of packaging materials can be used in the retort sterilization process, such as cans, jars, and flexible polymer-based packaging, such as the retort packaging films and laminated polypropylene-based films described herein. Advantages of using flexible packaging for retort applications include weight reduction as well as reduced energy required to bring the contents of the package to the conditions at which sterilization occurs. Retort packaging films can have a thickness of about 2.5 mils (63.5 microns) to about 10 mils (254 microns), or about 3 mils (76.2 microns) to about 6 mils (152.4 microns).

[0026] 1, an embodiment of a retort packaging film 10 includes an outer polypropylene-based film 20, a barrier layer 40, and a sealing layer 32. The outer polypropylene-based film 20 is disposed on one major surface of the retort packaging film and will be the exposed outer surface of the retort package. The sealing layer 32 is disposed on the other major surface of the retort packaging film and will be the product contact surface when the retort packaging film is formed into a retort package. The barrier layer 40 is disposed inwardly relative to the surface of the retort packaging film. The retort packaging film has an overall composition including at least 80% by weight of a polyolefin-based polymer. The retort packaging film has an overall composition including at least 80% by weight of a polypropylene-based polymer.

[0027] As used herein, a "layer" is a homogenous component of a film. A layer can be continuous or discontinuous (i.e., patterned) with respect to the length and width of the film. As used herein, the term "film" is a single or multi-layer web having a z-dimension (thickness) that is small compared to the x- and y-dimensions (length and width), not unlike a sheet of paper. A film is generally considered to have two opposing major surfaces that extend in length and width. A film can be composed of an infinite number of films and / or layers that are joined together to form a composite article. A packaging film portion can be referred to as a layer or a film.

[0028] The retort packaging film contains at least one polypropylene-based film. As used herein, a "polypropylene-based film" has a composition that contains at least 50%, or at least 90% by weight of a polypropylene-based polymer. In some cases, the polypropylene-based film can be essentially 100% polypropylene-based polymer.

[0029] The outer polypropylene-based film may be stretched. As used herein, the term "stretched" indicates that the film is heated to a temperature below the melting point of the material and stretched at least twice. This is typically accomplished by a double or triple bubble process using hot rolls, by a tenter-frame process or by an MDO process. A typical blown film process provides a certain elongation of the film, but is not sufficient and is not considered to be oriented as described herein. The film may be biaxially stretched or uniaxially stretched in either direction. The outer polypropylene-based film is preferably heat set (i.e. annealed) after stretching so that it is dimensionally stable under the high temperature conditions that it may be subjected to during conversion to a retort film laminate (i.e. printing or laminating) or during use of the laminate (i.e. heat sealing or retort sterilization). The outer polypropylene-based film may be manufactured using specific polymers and may be stretched using specific conditions that optimize the heat resistance of the film.

[0030] The outer polypropylene-based film can be an oriented polypropylene film, such as biaxially oriented polypropylene. The oriented polypropylene film can have one or more layers and can have a specialized coating, such as a matte lacquer. Any of the layers of the oriented polypropylene film can contain a pigment, such as titanium dioxide, that makes the film opaque to visible light. The film can be a cavitated biaxially oriented polypropylene, which can result in a film that is opaque to visible light. The biaxially oriented polypropylene can be transparent to visible light. In some embodiments, the outer polypropylene-based film is a biaxially oriented polypropylene film that essentially comprises polypropylene. The outer polypropylene-based film can have a thickness of about 12, about 20, about 25, or about 30 microns, but is not limited thereto.

[0031] Commercial examples of films that can be used as the outer polypropylene-based film include Bicor® NND20 (non-heat sealable, single-sided treated BOPP available from Jindal Films), PL1 (non-heat sealable, single-sided treated BOPP available from Polibak Plastik Film San. ve Tic. AS) and PPTE_LAM (non-heat sealable, single-sided treated available from Poligal).

[0032] As used herein, the term "exterior" is used to describe a film or layer that is disposed on one of the major surfaces of the film in which it is contained. As used herein, the term "interior" is used to describe a film or layer that is not disposed on a surface of the film in which it is contained. An interior film or layer is adjacent to another film or layer on both sides.

[0033] The barrier layer of a retort packaging film is generally coextensive with the retort packaging film and contains a barrier material. The barrier layer reduces the transmission of gases such as oxygen (i.e., contains an oxygen barrier material). The barrier layer can also reduce the transmission of moisture (i.e., contains a moisture-proof material). The barrier layer is typically an inner layer of the retort packaging film to protect the integrity of this critical layer. The barrier material can be polymeric in nature, such as polyamide, ethylene vinyl alcohol copolymer, or polyvinyl alcohol copolymer. The barrier material can be metallic, such as a thin deposit of aluminum. The barrier layer can be a transparent inorganic oxide coating, such as AIOx or SiOx. The barrier layer can be multi-layered and contain different layers of barrier material. The barrier layer can be a blend of multiple barrier materials. The barrier layer provides the specific barrier required to preserve the product in the retort package over an extended shelf life that can exceed several months or even a year.

[0034] The barrier layer can be disposed on the surface of the outer polypropylene-based film. In some embodiments of the retort packaging film, the barrier layer is disposed on the inner surface of the outer polypropylene-based film opposite the sealing layer. Alternatively, the barrier layer is deposited on the surface of the inner film.

[0035] The barrier layer inhibits the ingress of oxygen through the retort packaging film during the shelf life of the packaged product (i.e., while the package is hermetically sealed). In some embodiments, the retort packaging film is sealed to a thickness of 2 cm prior to being subjected to a retort sterilization process. 3 / m 2 / day, less than 1cm 3 / m 2 / day, less than 0.5 cm 3 / m 2 / day or less than 0.1 cm 3 / m 2 / day (measured according to ASTM F1927 using conditions of 1 atmosphere, 23°C and 50% RH). In some embodiments, after being subjected to a typical retort sterilization process, the retort packaging film has an average oxygen transmission rate (OTR) value of less than 2 cm 3 / m 2 / day, less than 1cm 3 / m 2 / day, less than 0.5 cm 3 / m 2 / day or less than 0.1 cm 3 / m 2 The average OTR value is less than 1 / day. The average OTR value can be near, or below, the minimum detection level of the test device. To perform a typical retort sterilization process, a DIN A4 size portion of the retort packaging film was cut and subjected to a steam sterilization process at 128°C and 2.5 bar overpressure for 60 minutes, followed by water shower cooling.

[0036] The sealing layer of the retort packaging film has a composition that allows for the formation of a heat seal, thus forming an airtight package. As used herein, the term "heat seal" or "heat sealed" refers to two or more surfaces that are joined together by the brief application of both heat and pressure, or by an ultrasonic energy sealing process. Heat sealing and ultrasonic sealing are well known and commonly used processes for making packages, and are familiar to those skilled in the art.

[0037] A sealing layer is always present on the surface of the retort packaging film to facilitate the function of sealing. During use of the retort packaging film in retort packaging, the sealing layer can be heat sealed to itself or to another packaging material component. During heat sealing, the sealing layer softens and can form a heat seal bond at a sealing temperature lower than the heat resistance of the outer polypropylene-based film. The sealing layer softens at a sealing temperature lower than the heat resistance of the outer oriented film. The sealing layer should soften and form a heat seal under sealing conditions (time, temperature and pressure) that do not cause excessive shrinkage or marring on the outer surface of the retort packaging film.

[0038] Retort packaging films aim to contain high amounts of polyolefins, specifically polypropylene, so that they can be tolerated for the recycling process. Polyolefins have relatively low heat resistance compared to materials traditionally used for retort packaging films (i.e. polyester, aluminum foil, polyamide). As a result of the lower heat resistance, the retort packaging is formed using a heat sealing process at a lower temperature to avoid any shrinkage or burn-through. The challenge faced by the retort packaging films disclosed herein is to introduce a sealing layer with low heat seal initiation temperature (HSIT) and high seal strength and toughness to withstand both retort processing and normal shipping and handling (i.e. drop strength and burst strength). The sealing layer must also contain materials approved for contact with food during retort conditions as required by government agencies for food safety.

[0039] The sealing layer may contain a material that has a low heat seal initiation temperature (HSIT). In some embodiments of the retort packaging film, the sealing layer contains a polypropylene copolymer that has a melting temperature of 135° C. or less.

[0040] The sealing layer can be formed by any known process. For example, the sealing layer can be a heat seal lacquer coated onto other layers of the retort packaging film. In other embodiments, the sealing layer is formed by an extrusion process that applies a polymer melt directly to other layers of the retort packaging film. In yet other embodiments, the sealing layer can be formed off-line by a coextrusion process (i.e., a cast film or blown film process) and then adhered to other layers of the retort packaging film using a lamination process. The sealing layer can be included in a multi-layer film containing two, three, four or more layers.

[0041] 2, an embodiment of the retort packaging film 10 includes an outer polypropylene-based film 20, a barrier layer 40, a sealing layer 32, and a backing layer 34. The sealing layer 32 and the backing layer 34 are layers within a coextruded multilayer film 30. The outer polypropylene-based film 20 can be disposed on one major surface of the retort packaging film and will be the exposed exterior surface of the retort package. The sealing layer 32 is disposed on the other major surface of the retort packaging film and will be the product contact surface of the retort package. The backing layer 34 is disposed adjacent to the sealing layer 32. The barrier layer 40 is disposed inwardly relative to the surface of the retort packaging film 10. The retort packaging film has an overall composition that includes at least 80% by weight of a polyolefin-based polymer. The retort packaging film can have an overall composition that includes at least 80% by weight of a polypropylene-based polymer.

[0042] The backing layer of the coextruded multilayer film provides additional stiffness and toughness to the structure. The backing layer of the coextruded multilayer film can be formulated for sufficient adhesion of the retort packaging film layer to the other layers. In some embodiments, the backing layer contains one or more polypropylene-based polymers. The backing layer can also contain other polyolefin-based polymers, such as polyethylene-based polymers, along with the other layers of the multilayer film.

[0043] Although the structure of the retort packaging film and any packaging made therefrom contains several different elements (outer layer, barrier layer, sealing layer, etc.), the overall composition of the film or packaging should have a high level of a single material type (polyolefin or specifically polypropylene) to facilitate recycling. As used herein, the term "total composition" is used to describe the entire film structure or packaging. Any materials, layers or components that are connected to each other in any way are part of the overall composition of the article. The retort packaging film can have a high level of polyolefin-based polymer. The packaging film can have a high level of polypropylene-based polymer. The packaging film described herein, and any retort packaging made therefrom, can be recyclable in a polypropylene recycling process when the article contains a high amount of polypropylene-based polymer. The mixed polyolefin recycling process can also accept relatively high levels of polyolefins that are not polypropylene, so the article can also contain high levels of polyolefins that are not polypropylene and still be suitable for recycling.

[0044] As used herein, "polyolefin-based polymer" refers to a homopolymer or copolymer having at least one alkene monomer bond in the repeating backbone of the polymer. Primary examples of polyolefin-based polymers are polyethylene homopolymers and copolymers and polypropylene homopolymers and copolymers. Other examples of polyolefin-based polymers are ethylene vinyl alcohol copolymers and cyclic olefin copolymers.

[0045] The retort packaging film can have a total composition containing at least 80% by weight of polyolefin-based polymer. In other words, considering all materials (polymer and non-polymer) in the entire retort packaging film, at least 80% by weight is polyolefin-based polymer. The retort packaging film can have a total composition containing a minimum polyolefin-based polymer content of 80% by weight, 82% by weight, 84% by weight, 86% by weight, 88% by weight or 90% by weight. The retort packaging film can have a total composition containing a maximum polyolefin-based polymer content of 100% by weight, 99% by weight, 98% by weight, 97% by weight, 96% by weight or 95% by weight. For example, the retort packaging film can have a total composition having 90% to 99% by weight of polyolefin-based polymer, or the retort packaging film can have a total composition having 82% to 100% by weight of polyolefin-based polymer.

[0046] As used herein, "polypropylene-based polymer" means a homopolymer or copolymer having at least one propylene monomer bond in the repeating backbone of the polymer. The propylene bond can be represented by the general formula: [CH2-CH(CH3)]n. Such polypropylenes can be polypropylene impact copolymers, polypropylene random copolymers or polypropylene homopolymers, can be syndiotactic or isotactic, and / or can be nucleated or non-nucleated. The polypropylene-based polymer can be a propylene alpha-olefin copolymer.

[0047] The retort packaging film can have a total composition containing at least 70% by weight of polypropylene-based polymer. In other words, considering all of the materials (polymer and non-polymer) in the entire retort packaging film, at least 70% by weight is polypropylene-based polymer. The retort packaging film can have a total composition containing a minimum polypropylene-based polymer content of 70%, 80%, 85%, 86%, 88% or 90% by weight. The retort packaging film can have a total composition containing a maximum polypropylene-based polymer content of 100%, 99%, 98%, 97%, 96% or 95% by weight. For example, the retort packaging film can have a total composition having 70% to 98% by weight of polypropylene-based polymer, or the retort packaging film can have a total composition having 80% to 100% by weight of polypropylene-based polymer.

[0048] In some embodiments, the retort packaging film has a total composition that contains less than 10% by weight of polymers other than polyolefin-based polymers. In addition to having high polyolefin and polypropylene content, the retort packaging film can have a low level of non-polyolefin polymers relative to the total composition. Non-polyolefin polymers that can be contained in the retort packaging film include polyamides, polyacrylates, and polyurethanes. These polymers can be present in the extrusion layer or in the printing ink or adhesive layer. The retort packaging film can have a total composition that contains less than 9%, 8%, 7%, 6%, or 5% by weight of polymers other than polyolefin-based polymers.

[0049] In some embodiments, the retort packaging film is essentially free of polymers other than polyolefin-based polymers, in other words, any non-polyolefin polymers that may be present in the retort packaging film do not affect the basic and material properties of the film.

[0050] 3, an embodiment of the retort packaging film 10 includes an outer polypropylene-based film 20, a barrier layer 40, an inner polypropylene-based film 50, a sealing layer 32, and a backing layer 34. The sealing layer 32 and the backing layer 34 are layers within the coextruded multilayer film 30. The outer polypropylene-based film 20 can be disposed on one major surface of the retort packaging film, which will be the exposed exterior surface of the retort package. The sealing layer 32 is disposed on the other major surface of the retort packaging film, which will be the product contact surface of the retort package. The backing layer 34 is disposed adjacent to the sealing layer 32. The inner polypropylene-based film 50 and the barrier layer 40 are disposed on the inner surface of the retort packaging film 10. The retort packaging film can have an overall composition that includes at least 80% by weight of a polyolefin-based polymer. The retort packaging film has an overall composition that includes at least 80% by weight of a polypropylene-based polymer.

[0051] The barrier layer can be in contact with the inner surface of the outer polypropylene-based film. The barrier layer can be in contact with either surface of the inner polypropylene-based film.

[0052] The inner polypropylene-based film may be oriented. The film may be biaxially oriented or uniaxially oriented in either direction. The inner polypropylene-based film is preferably heat set (i.e. annealed) so that it is dimensionally stable under the high temperature conditions that it may be subjected to during conversion into a laminate or during use of the laminate (i.e. heat sealing or retort sterilization). The inner polypropylene-based film, if present, may be the same as or different from the outer polypropylene-based film.

[0053] The inner polypropylene-based film can be an oriented polypropylene film, such as biaxially oriented polypropylene. The oriented polypropylene film can have one or more layers and can have a specialized coating, such as a matte finish. Any of the layers of the oriented polypropylene film can contain a pigment, such as titanium dioxide, that makes the film opaque to visible light. The film can be hollowed biaxially oriented polypropylene, resulting in a film that is opaque to visible light. The biaxially oriented polypropylene can be transparent to visible light. In some embodiments, the outer polypropylene-based film is a biaxially oriented polypropylene film that essentially comprises polypropylene.

[0054] In embodiments containing an inner polypropylene-based film, the inner polypropylene-based film can be the same or different from the outer polypropylene-based film. Commercial examples of films that can be used as the inner polypropylene-based film include Bicor® NND20 (non-heat sealable, single-sided treated BOPP available from Jindal Films), PL1 (non-heat sealable, single-sided treated BOPP available from Polibak Plastik Film San. ve Tic.AS) and PPTE_LAM (non-heat sealable, single-sided treated available from Poligal).

[0055] The barrier layer may be a coating or deposition applied to one of the films used to make the retort packaging film. For example, the barrier layer 40 shown in the embodiment shown in FIG. 3 may be a silicon oxide material deposited on the inner polypropylene-based film 50 disposed between the outer and inner polypropylene-based films. Alternatively, the barrier layer 40 shown in the embodiment shown in FIG. 3 may be a silicon oxide material deposited on the outer polypropylene-based film 20 disposed between the outer and inner polypropylene-based films. Alternatively, the barrier layer may be a silicon oxide material deposited on the side of the inner polypropylene-based film facing the sealant layer (this embodiment is not shown).

[0056] Any embodiment of the retort packaging film can contain other materials and layers. For example, the film structure can contain either an extruded tie layer or other adhesive layer intended to bond different materials. The film can contain an ink layer anywhere in the structure.

[0057] Also disclosed herein is a laminated polypropylene-based film suitable for retort packaging. An embodiment of a laminated polypropylene-based film 60 is shown in FIG. 4. The laminated polypropylene-based film has an outer stretched film 70, a barrier layer 80, and a multi-layer film 90 including a sealing layer 92. The laminated polypropylene-based film has a strength of 440N / 15cm 2The laminated polypropylene-based film can be heat sealed to itself (sealing layer to sealing layer) at a sealing temperature of less than 130°C using a pressure of 1000 mm and a pause of 1 second. In other words, when heat sealed to itself under these conditions, the sealing layer forms a strong seal that goes beyond being merely tacky. A strong seal can be determined by measuring the force to separate the materials using ASTM F88 (grip separation at 100 mm / min), with an average seal strength of at least 10 N / 15 mm. In some embodiments, the heat seal strength of the laminated polypropylene-based film when heat sealed to itself is greater than 30 N / 15 mm, 40 N / 15 mm, or 50 N / 15 mm.

[0058] In some embodiments of the retort packaging film or laminated polypropylene-based film, the outer film, the inner film and the multi-layer film are essentially free of polymers other than polyolefins.

[0059] Retort packaging Described herein are retort packaging films and laminated polypropylene-based films suitable for retort packaging, and retort packages and shelf-stable packaged products made therefrom. As used herein, a "retort packaging film" or "retort package" is a film, or a package made from a film, that can remain hermetically sealed after being filled with a product, sealed, and subjected to a typical retort sterilization process.

[0060] Examples of retort packaging configurations include, but are not limited to, pouches or bags, stand-up pouches (as shown in FIG. 5), trays, cups or bowls with lids, or flow wraps. Retort packaging can be made entirely from one or more retort packaging films described herein. Retort packaging can be made from a variety of components, such as at least one retort packaging film described herein. Also, any component of the retort packaging that is not a retort packaging film described herein can have a high level of polypropylene polymer. In some embodiments of retort packaging, the packaging is made from at least one film described herein and at least one other component, which has at least 90% by weight of a polypropylene-based polymer, such that the entire packaging is recyclable in a polypropylene recycling process.

[0061] The retort package comprises at least one heat seal that allows for joining the components of the packaging material, forming the package, and hermetically sealing the package. An example of a retort package 100 comprising a retort packaging film 110 and a heat seal 114 is shown as a stand-up pouch in Figure 5. In this embodiment, the retort package is made entirely from the retort packaging films described herein, using the heat seal to form and seal the package.

[0062] In some embodiments of the retort packaging, some components of the packaging are not recyclable in the polypropylene recycling process. In that case, the components of the packaging material can be separated before recycling and / or disposal. Separation of the components of the packaging material can be accomplished by peeling off the heat seal.

[0063] In some embodiments of a retort package formed from a retort packaging film, the package comprises at least 90% by weight of a polyolefin-based material or at least 80% by weight of a polyolefin-based material. In some embodiments of a retort package formed from a retort packaging film, the package comprises at least 90% by weight of a polypropylene-based material or at least 80% by weight of a polypropylene-based material. In some embodiments of a retort package formed from a retort packaging film, the package comprises at least 90% by weight of a polyolefin-based material and at least 80% by weight of a polypropylene-based material.

[0064] Shelf-stable packaging products Retort packaging films and laminated polypropylene-based films suitable for retort packaging and retort packages and shelf-stable packaged products made therefrom are described herein, as shown in Figure 6. Retort packaging film 210 is used to form a retort package holding product 220, resulting in shelf-stable packaged product 200. As previously discussed, heat seal 214 is used to form the retort package and hermetically seal shelf-stable packaged product 200.

[0065] In some embodiments of shelf-stable packaged products, the product in the retort package is a perishable product if it were not for the sterilization process it undergoes while hermetically sealed in the retort packaging film. As used herein, the product may be a perishable food product, where the sterilization process (i.e., retort) allows for storage and preservation of the product at ambient conditions for months or years. The product undergoes the sterilization process while hermetically sealed in a package formed from the retort packaging film. Once sterilized, the retort package prevents oxygen from entering (i.e., has high oxygen barrier properties), helping to extend the shelf life of the product.

[0066] In some embodiments of shelf-stable packaged products, the product in the retort package is a product that has been sterilized while hermetically sealed in the package and therefore maintains its sterility.

[0067] An embodiment of a process used to produce a shelf-stable packaged product is shown in FIG. 7. As previously discussed, the initial package 320 is formed by a heat seal 314 on the retort packaging film 310. The heat seal 314 can be formed between two retort packaging films 310, as in the illustrated stand-up pouch configuration, or between a retort packaging film and another packaging material component. The heat seal can be formed at any sealing temperature high enough to form a heat seal but low enough to prevent shrinkage of the retort packaging film. For example, the heat seal temperature can be 160° C. or less, 150° C. or less, 140° C. or less, or 130° C. or less. The initial package 320 is then filled with a product 330. After filling, the initial package has an additional heat seal 314 applied to completely enclose the product within the final package 340. In other words, the initial package filled with the product is hermetically sealed to form the final package. The final package is subjected to an autoclave process 350, or another suitable sterilization process, resulting in a shelf-stable packaged product 360. EXAMPLES

[0068] Examples and Data Five example retort packaging films were constructed for testing, details of Examples 1-5 can be found in Table 1 below.

[0069] Each of Examples 1-4 was a three layer laminate with an outer polypropylene based film (100% polypropylene based material) that was a biaxially oriented polypropylene film, a barrier layer that was a silicon oxide coating deposited on the biaxially oriented polypropylene film (100% polypropylene based material), and a multilayer film (100% polypropylene based material) that contained a low sealing initiation temperature sealing layer.

[0070] Example 5 was a two-layer laminate with an outer polypropylene-based film (100% polypropylene-based material) that was a biaxially oriented polypropylene film and a barrier layer that was a silicon oxide coating deposited on the outer biaxially oriented polypropylene film (100% polypropylene-based material) and a multilayer film (100% polypropylene-based material) that contained a low seal initiation temperature sealing layer.

[0071] The films of Examples 1-5 were bonded together using adhesive lamination, which in some cases also contained ink. The adhesive used for these examples was a solvent-based two-component system of Dow Adcote 811A and Catalyst C9L10 available from Dow Chemical. The ink was a retortable grade, as known in the art. The films of Examples 1-4 were laminated such that the inner biaxially oriented polypropylene film bearing a silicon oxide coating was stretched and faced the outer oriented polypropylene film. For Example 5, the outer biaxially oriented polypropylene film bearing a silicon oxide coating was stretched and faced the multilayer film.

[0072] The amounts of polyolefin-based and polypropylene-based materials for each layer of the films of Examples 1-5 are given in Table 1. The biaxially oriented polypropylene film used contained 100% polypropylene-based material (and therefore also 100% polyolefin-based). The adhesives and inks were based on other polymers and therefore contained 0% polyolefin and 0% polypropylene-based materials. The biaxially oriented polypropylene film coated with SiOx contained a non-olefin lacquer and an inorganic coating, neither of which was a polyolefin-based or polypropylene-based material. Therefore, only a portion of the weight of this layer (e.g. 18.1 g / m2) was used. 2 from 16.3 g / m 2 ) is counted towards the total PO or PP composition. The total compositions of Examples 1 to 5 as weight percentages are given in Table 1, which pertains to the polyolefin-based material (PO) and the polypropylene-based material (PP).

[0073] The oxygen transmission rate (OTR) is described for each of Examples 1-5. The OTR was measured according to ASTM F1927 using the conditions of 1 atmosphere, 23C and 50%RH. The post-retort OTR was measured after the retort packaging film was subjected to a typical retort sterilization process (cut a DIN A4 size piece of the retort packaging film and subject it to a steam sterilization process at 128°C and 2.5 bar overpressure for 60 minutes, followed by water shower cooling). The retort packaging film retains excellent OTR even after being subjected to retort processing.

[0074] [Table 1]

[0075] [Table 2]

[0076] As discussed above, the outer polypropylene-based film can have a surface coating, such as a matte lacquer. The matte lacquer provides additional heat resistance, making a thinner outer polypropylene-based film feasible. Additionally, thinner multi-layer films can be used as well. The resulting film has a lower overall composition of polyolefin and polypropylene, both approaching 80%. Details of this envisioned structure are shown in Table 2.

[0077] [Table 3]

[0078] As discussed, any of the films used in the retort packaging film may contain a portion of a polyolefin-based polymer other than polypropylene. For example, the structure of Example 4 may be manufactured using a multi-layer film containing about 20% polyethylene-based material. It is believed that the multi-layer film may contain small amounts of polyethylene-based material in various layers of the film and still retain the properties required for retort. As a result of such inclusion of polyethylene-based material, the overall composition of the retort packaging film of Example 8 remains the same for polyolefin-based material but decreases to 80% for polypropylene-based material when compared to Example 4. Details of this type of envisioned structure are shown in Table 3.

[0079] [Table 4]

[0080] The heat seal data for Examples 2, 3 and 4 are shown below in Table 4. The film was sealed to itself (sealing layer to sealing layer) using a Teflon coated heat seal bar heated to a temperature ranging from 120° C. to 150° C. The seal was performed with a 1 second pause and 440 N / 15 cm 2 The seal strength of the seal was then tested using test method ASTM F88 (grip separation speed of 100 mm / min) and the results are listed in Table 2.

[0081] Additionally, samples of the film were sealed and then subjected to retort conditions of steam sterilization at 128°C and 3.5 bar overpressure for 60 minutes. Water shower cooling was used before retesting the seal strength. All results are listed in Table 4. The sealing layer of the retort packaging film can be sealed at low temperatures such as 130°C, minimizing any damage to the outer layer of the film structure that may occur at higher sealing temperatures. Additionally, the seal strength remains high after being subjected to retort conditions.

[0082] [Table 5]

[0083] Retort packaging film embodiment (i) an outer polypropylene-based film; A barrier layer; A retort packaging film including a sealing layer, A retort packaging film having a total composition comprising at least 80% by weight of a polyolefin-based polymer. (ii) The retort packaging film according to any other embodiment, wherein the outer polypropylene-based film is stretched. (iii) The retort packaging film according to any other embodiment, wherein the barrier layer comprises a metal or an inorganic oxide. (iv) The retort packaging film according to embodiment (iii), wherein a barrier layer is deposited on a surface of the outer polypropylene-based film. (v) The retort packaging film according to any other embodiment, wherein the total composition of the retort packaging film contains at least 80% by weight of a polypropylene-based polymer. (vi) The retort packaging film according to any other embodiment, wherein the total composition of the retort packaging film contains at least 90% by weight of a polyolefin-based polymer. (vii) The retort packaging film according to any other embodiment, wherein the sealing layer is within a multilayer film, the multilayer film also including a backing layer. (viii) an outer polypropylene-based film; and An inner polypropylene film; a barrier layer deposited on at least one surface of the inner and outer polypropylene-based films; A retort packaging film comprising a multilayer film including a sealing layer, A retort packaging film having a total composition comprising at least 80% polypropylene-based polymer. (ix) The retort packaging film according to embodiment (viii), wherein at least one of the inner or outer polypropylene-based films is stretched. (x) The retort packaging film according to any other embodiment, wherein the sealing layer comprises a polypropylene copolymer having a melting temperature of 135° C. or less. (xi) Retort packaging film: 1 sec. and 440 N / 15 cm 2 The retort packaging film according to any other embodiment, which can be heat sealed to itself at a sealing temperature of less than 130°C using the sealing conditions of (xii) The retort packaging film according to any other embodiment, wherein the outer stretch film and the sealing layer are essentially free of polymers other than polyolefins.

[0084] Retort Packaging Embodiments (I) A retort package formed from one or more of the retort packaging films according to any of the retort packaging film embodiments. (II) A retort package comprising a retort packaging film comprising at least 80% polyolefin-based material and comprising a heat seal. (III) The retort packaging film further comprises a barrier layer, and the retort packaging film has a thickness of 2.0 cm 3 / m 2 The retort package according to embodiment (I) or (II) has an oxygen transmission rate (ASTM F1927, 23C, 50% Rh) of less than 1000 rpm. (IV) The retort packaging film further comprises a barrier layer, and the retort packaging film has a thickness of 1.0 cm 3 / m 2 The retort package according to embodiment (I) or (II) has an oxygen transmission rate (ASTM F1927, 23C, 50% Rh) of less than 1000 rpm. (V) The retort package according to any other embodiment, wherein the retort package essentially comprises one or more retort packaging films each comprising at least 80% polypropylene-based material, and at least one heat seal.

[0085] Shelf-stable packaged product embodiments (a) a retort packaging film having a total composition containing at least 80% polypropylene-based polymer; A shelf-stable packaged product comprising a product hermetically sealed in a retort packaging film that would be perishable but for the sterilization process it is subjected to while hermetically sealed in the retort packaging film.

[0086] Method embodiments (A) A method for producing a shelf-stable packaged product, comprising the steps of: i) forming an initial package by heat sealing a retort packaging film according to any preceding claim to itself using a temperature of up to 160°C; ii) packing the product into the primary packaging; iii) heat sealing the initial package to hermetically seal the product within the final package; iv) A process comprising the step of subjecting the final packaging to an autoclave process.

Claims

1. An outer polypropylene film; A barrier layer; A retort packaging film including a sealing layer, A retort packaging film having a total composition comprising at least 80% by weight of a polyolefin-based polymer.

2. 10. The retort packaging film of claim 1, wherein the outer polypropylene-based film is oriented.

3. The retort packaging film according to claim 1 , wherein the barrier layer comprises a metal or an inorganic oxide.

4. The retort packaging film of claim 1 , wherein the barrier layer is deposited on a surface of the outer polypropylene-based film.

5. 2. The retort packaging film according to claim 1, wherein the total composition of the retort packaging film contains at least 80% by weight of a polypropylene-based polymer.

6. 2. The retort packaging film according to claim 1, wherein the total composition of the retort packaging film contains at least 90% by weight of a polyolefin-based polymer.

7. 10. The retort packaging film of claim 1, wherein the sealing layer is within a multilayer film, the multilayer film also including a backing layer.

8. An outer polypropylene film; An inner polypropylene film; a barrier layer deposited on at least one surface of the inner and outer polypropylene-based films; A retort packaging film comprising a multilayer film including a sealing layer, A retort packaging film having a total composition comprising at least 80% polypropylene-based polymer.

9. 9. The retort packaging film of claim 8, wherein at least one of the inner or outer polypropylene-based films is oriented.

10. 9. The retort packaging film of claim 8, wherein the sealing layer comprises a polypropylene copolymer having a melting temperature of 135°C or less.

11. The retort packaging film according to claim 8 , wherein the barrier layer comprises a metal or an inorganic oxide.

12. A retort package formed from one or more of the retort packaging films of claim 8.

13. A retort package comprising a retort packaging film comprising at least 80% polyolefin-based material, the retort package comprising a heat seal.

14. The retort packaging film further comprises a barrier layer, and the retort packaging film has a thickness of 2.0 cm 3 / m 2 14. The retort package of claim 13, having an oxygen transmission rate (ASTM F1927, 23C, 50% Rh) of less than days.

15. The retort packaging film further comprises a barrier layer, and the retort packaging film has a thickness of 1.0 cm 3 / m 2 14. The retort package of claim 13, having an oxygen transmission rate (ASTM F1927, 23C, 50% Rh) of less than days.

16. 14. The retort package of claim 13, wherein the retort package consists essentially of one or more retort packaging films each comprising at least 80% polypropylene-based material and at least one heat seal.

17. An outer stretched film; A barrier layer; A laminated polypropylene-based film suitable for retort packaging comprising a multi-layer film including a sealing layer, the film having a viscosity of 1 sec and 440 N / 15 cm 2 1. A laminated polypropylene-based film that can be heat sealed to itself at a sealing temperature of less than 130° C. using the sealing conditions of

18. 20. The laminated polypropylene-based film of claim 17, wherein said outer stretched films and said multilayer film are essentially free of polymers other than polyolefins.

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