RU2811922C1 - Heat-resistant, autoclavable packaging ready for recycling - Google Patents

Abstract

FIELD: polymer materials.

SUBSTANCE: autoclavable packaging film and packaged products made from them. A polypropylene-based laminate film suitable for autoclavable packaging includes an outer film, a barrier layer, and a sealing layer. Autoclavable packaging film has a general composition containing large amounts of polyolefin-based polymers and polypropylene-based polymers. The material is effective in the process of recycling polypropylene.

EFFECT: packaging film that retains the properties required to adequately withstand the autoclave sterilization process and produce a high-quality packaged shelf-stable product.

8 cl, 7 dwg, 4 tbl

Description

TECHNICAL FIELD

[1] The present invention relates to film structures, in particular to autoclavable packaging films and packaged products made from them. The packaging films described herein may be suitable for recycling in a polyolefin-based process.

BACKGROUND OF THE INVENTION

[2] Pasteurization operations (i.e., autoclave sterilization) are used to sterilize and heat treat food or other products contained in hermetically sealed packaging components. Food or other products are packaged and sealed in an autoclave-sterilizable package, such as a pouch, and transferred to an autoclave where they are exposed to temperatures typically above the boiling point of water for an extended period. The autoclave sterilization process also uses positive pressure to complete the sterilization step.

[3] Specialized flexible packaging films are used for applications that use an autoclave sterilization process to create a shelf-stable or sterilized product. Commercially available shelf-stable foods, such as pre-cooked rice, wet pet foods, or tuna, are available in flexible packaging formats such as stand-up pouches, lidded trays, or flow packaging. Packaged products can be stored in ambient conditions for months or years, depending on the barrier ability of the packaging films.

[4] Flexible packaging films used for in-pack sterilization often have many different layers, with each layer having one or more important properties required for demanding applications. For example, packaging films may require high rigidity and high temperature resistance to perform effectively in a high-speed packaging process. The packaging film must be able to withstand the high temperatures and pressure changes during the sterilization process without losing seal integrity or becoming unattractive in appearance.

[5] A typical flexible packaging film intended for sterilized product applications may include a combination of materials, such as polyester or polyamide, that provide excellent heat resistance, dimensional stability, and rigidity; aluminum foil providing high barrier properties and rigidity; and/or polyolefins providing suitable sealing characteristics. Unfortunately, when such a wide variety of materials are combined into one packaging film, it becomes difficult to recycle.

SUMMARY OF THE INVENTION

[6] Disclosed herein is a flexible laminated packaging film that can be used in autoclave product applications having the important advantage of being recyclable in the polyolefin recycling stream. Despite its high polyolefin composition, autoclavable packaging film retains characteristics that allow it to perform well in high-speed packaging operations and withstand the sterilization cycle while maintaining good appearance, excellent barrier properties and sealability.

[7] The autoclavable packaging films described herein have a polypropylene-based outer film, a barrier layer, and a seal layer. Autoclavable packaging film has a general composition containing at least 80% polyolefin-based polymers by weight. Autoclavable packaging film has a general composition of at least 80% polypropylene-based polymers by weight.

[8] In some embodiments, the autoclavable packaging film further has a polypropylene-based inner film. One or both of the polypropylene-based inner and outer films may be oriented.

[9] Preferred embodiments of autoclavable packaging film have a barrier layer comprising a metal or inorganic oxide. The barrier layer is applied to the surface of either the outer or inner polypropylene-based film.

[10] In some embodiments, the sealing layer of the autoclavable packaging film is part of a multilayer film that also has a protective layer. The sealing layer can be thermally sealed to itself at a sealing temperature of 130°C, sealing for 1 second and a pressure of 440 N/15 cm ² . In some cases, this sealing characteristic is achieved when the sealing layer contains a polypropylene copolymer having a melting point that is less than or equal to 135°C. Ideally, the polypropylene-based outer film and sealing layer contain virtually no polymers other than polyolefins.

[11] An autoclavable package may be formed from one or more autoclavable packaging films.

[12] As for autoclave-sterilizable packaging, it is made from autoclave-sterilizable packaging film with a general composition of at least 80% polyolefin-based materials. Autoclavable packaging film has a barrier layer that provides an oxygen transmission rate of less than 2.0 cm ³ /m ² per day, or preferably less than 1.0 cm ³ /m ² per day.

[13] Also disclosed herein are packaged shelf-stable foods. The shelf-stable packaged product contains an autoclavable packaging film having at least 80% polypropylene-based polymers and a product hermetically sealed in an autoclave-sterilizable film.

[14] Also disclosed herein are methods for producing a shelf-stable packaged product. The methods include making an initial package by heat sealing an autoclave-sterilizable packaging film to itself using a sealing temperature that is less than or equal to 160°C, filling the initial package with product, heat sealing the original package to completely enclose the product within the final package, and subjecting the final package to the process sterilization in an autoclave.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

[15] The present invention may be more fully understood by reference to the following detailed description of various embodiments of the present invention in connection with the accompanying drawings, in which:

[16] in Fig. 1 is a schematic side view of an embodiment of an autoclavable packaging film;

[17] in Fig. 2 is a schematic side view of an embodiment of an autoclavable packaging film;

[18] in Fig. 3 is a schematic side view of an embodiment of an autoclavable packaging film;

[19] in Fig. 4 is a schematic side view of an embodiment of an autoclavable packaging film;

[20] in Fig. 5 is a top view of an embodiment of an autoclave-sterilizable package;

[21] in Fig. 6 is a top view of an embodiment of a packaged shelf-stable product; And

[22] in Fig. 7 shows a flow diagram according to an embodiment of a method for producing a packaged shelf-stable product.

[23] The drawings show some, but not all, embodiments. Elements depicted in the graphics are illustrative and not necessarily to scale, and the same (or similar) reference numbers indicate the same (or similar) elements throughout the graphics.

DETAILED DESCRIPTION

[24] Modern flexible autoclavable packaging films contain a variety of different materials designed to provide high performance in demanding applications. The structures typically comprise layers that contain polyester, polyamide, polyethylene, polypropylene, metal and/or ethylene-vinyl alcohol copolymer. Each layer of structure is designed to provide properties such as barrier, stiffness, heat resistance, dimensional stability, puncture resistance, seam strength and visual appeal, to name a few. The complex functional requirements of autoclavable packaging and the variety of materials in existing structures pose a major obstacle to the search for a more sustainable and recyclable packaging solution.

[25] As disclosed herein, an autoclavable packaging film structure has been developed containing large quantities of polyolefin-based materials, in particular large quantities of polypropylene-based materials. Despite eliminating many of the materials typically used in autoclavable packaging, the structure retains all the essential properties of barrier, heat resistance, appearance and seal integrity. The structure is advantageously suitable for easy recycling.

[26] In particular, the structure of the autoclave-sterilizable packaging film is designed such that the thermal seal initiation temperature of the sealing layer is low enough to correspond to the only moderate heat resistance of the outer surface. Although the seal layer now has a fairly low softening point, the seal layer still has sufficient integrity to withstand the high temperatures of the autoclave sterilization process, as well as other abuses that the package may be subjected to during distribution and use. Autoclavable packaging film can be formed into autoclavable packages at lower sealing temperatures while maintaining a superior appearance. Additionally, the packaging structure retains excellent barrier properties and appearance even after the film has been formed into a package, filled, hermetically sealed and subjected to an autoclave sterilization process.

[27] The autoclavable packaging films described herein contain at least 80% polyolefin-based polymers by weight and at least 50% polypropylene-based polymers by weight. The use of materials other than polyolefin-based polymers is kept to a minimum. The outside of the packaging film has a heat-resistant polypropylene-based film. The inside of the packaging film has a sealing layer, which is a mixture of polypropylene-based polymers. Autoclavable packaging film contains a barrier layer that is not typically a polyolefin-based material. The film may also contain other materials such as adhesives and printing inks.

[28] By using the packaging film structural components described herein, it is possible to obtain a recyclable packaging film. The films are suitable for recycling in polyolefin-based recycling processes due to their high polyolefin content. The films are also suitable for recycling in polypropylene-based recycling processes due to their high polypropylene content. In particular, the films may contain little or no amounts of materials such as polyester, polyamide, chlorinated polymers and aluminum foil. Preferably, autoclavable packaging films do not contain aluminum foil. As used herein, "aluminum foil" is a sheet of metal at least 1 micron thick, typically greater than 5 microns. Films may contain non-polyolefin based polymers, such as those used in adhesive layers or printing ink layers, but these are kept to a minimum and typically constitute less than 10% of the total composition by weight. Films may contain non-polymeric materials such as barrier materials, but these are kept to a minimum and typically constitute less than 10% of the total composition by weight.

AUTOCLAVABLE PACKAGING FILM

[29] This document describes autoclavable packaging films and polypropylene-based laminates suitable for autoclave-sterilizable packaging, as well as autoclavable packages and shelf-stable packaged products made from them. As used herein, "autoclaveable packaging film" or "autoclaveable packaging" is a film or package made from film that can be filled with a product, sealed, and remain sealed after a typical autoclave sterilization process. Typical autoclave sterilization is a batch process that uses temperatures from about 100°C to about 150°C, pressures up to about 70 psig (483 kPa), and can last from several minutes to several hours. Common autoclave sterilization processes used for products packaged in flexible films include steam or water immersion. Food or other products packaged in autoclavable packaging film and sterilized in an autoclave can be stored under ambient conditions for extended periods of time (i.e., are shelf stable) while maintaining sterility. Because the autoclave sterilization process is incredibly aggressive, very specialized flexible packaging films have been developed to withstand this process.

[30] Various types of packaging materials can be used in autoclave sterilization processes, including cans, cans, and polymer-based flexible packaging such as the autoclavable packaging films and polypropylene-based laminate films described herein. Advantages of using flexible packaging for autoclave sterilization applications include reduced weight and reduced energy required to bring the contents of the package to sterilization conditions. Autoclavable packaging film can have a thickness of from about 2.5 mils (63.5 microns) to about 10 mils (254 microns) or from about 3 mils (76.2 microns) to about 6 mils (152.4 microns).

[31] Referring now to FIG. 1, an embodiment of an autoclavable packaging film 10 comprises a polypropylene-based outer film 20, a barrier layer 40, and a seal layer 32. The polypropylene-based outer film 20 is disposed on one main surface of the autoclavable packaging film and becomes the exposed outer surface of the autoclavable packaging film. packaging. The sealing layer 32 is located on the other main surface of the autoclaveable packaging film and becomes the product contact side when the autoclaveable packaging film is formed into an autoclaveable package. The barrier layer 40 is located internally relative to the surfaces of the autoclavable packaging film. Autoclavable packaging film has a general composition containing at least 80% polyolefin-based polymers by weight. Autoclavable packaging film has a general composition of at least 80% polypropylene-based polymers by weight.

[32] As used herein, a “layer” is a homogeneous building block of films. The layers may be continuous or discontinuous (i.e., structured) along the length and width of the film. As used herein, the term "film" is a single or multi-layer web that has a small z-direction dimension (thickness) compared to its x- and y-direction dimensions (length and width), similar to a piece of paper. Films are generally considered to have two main surfaces opposite each other and extending in the length and width directions. The films can be made from an unlimited number of films and/or layers, with the films and/or layers bonded to each other to form a composite product. A piece of packaging film may be called a layer or film.

[33] The autoclavable packaging film comprises at least one polypropylene-based film. As used herein, “polypropylene-based film” has a composition containing at least 50% or at least 90% polypropylene-based polymer by weight. In some cases, the polypropylene-based film may consist essentially of 100% polypropylene-based polymer.

[34] The polypropylene-based outer film can be oriented. As used herein, the term "oriented" indicates that the film has been heated to a temperature below the melting point of the material and stretched to at least 2 times. This is typically achieved using a double blow or triple blow process, a frame process to stretch and orient the film, or an MDO process using heated rolls. The typical blown film process results in some stretching of the film, but not enough to be considered oriented as described herein. The film can be biaxially oriented or uniaxially oriented in any direction. The polypropylene-based outer film is preferably thermally shrinked (i.e., tempered) after orientation so that it remains dimensionally stable under elevated temperature conditions that may occur during conversion of the autoclaveable film laminate (i.e., printing or layering) or during use of the laminate (i.e., heat sealing or autoclave sterilization). Polypropylene-based outer film can be produced using certain polymers and can be oriented using certain conditions that optimize the thermal stability of the film.

[35] The polypropylene-based outer film may be an oriented polypropylene film such as biaxially oriented polypropylene. Oriented polypropylene film may have one or more layers and may have special finishes such as matte varnish. Any of the layers of oriented polypropylene film may contain a pigment, such as titanium dioxide, to make the film opaque to visible light. The film may be a biaxially oriented polypropylene foam, resulting in a film that is opaque to visible light. Biaxially oriented polypropylene can be transparent to visible light. In some embodiments, the polypropylene-based outer film is a biaxially oriented polypropylene film that substantially comprises polypropylene. The polypropylene-based outer film may have a thickness of about 12, about 20, about 25, or about 30 microns, but is not limited to.

[36] Commercial examples of films that can be used as polypropylene-based outer film include Bicor™ NND20 (non-thermal sealable single-sided BOPP available from Jindal Films), PL1 (non-thermal sealable single-sided BOPP available from Polibak Plastik Film San. ve Tic.A.S.) and PPTE_LAM (non-thermal sealable, single-sided, supplied by Poligal.

[37] In the context of this document, the term "outer side" is used to describe a film or layer that is located on one of the main surfaces of the film in which it is contained. As used herein, the term "inside" is used to describe a film or layer that is not located on the surface of the film in which it is contained. The inner film or layer is adjacent to the other film or layer on both sides.

[38] The barrier layer of the autoclaveable packaging film is typically the same extent as the autoclaveable packaging film and contains a barrier material. The barrier layer provides reduced transmission of gases such as oxygen (ie contains oxygen-impermeable material). The barrier layer may further provide reduced moisture transfer (ie, contain a moisture-impermeable material). The barrier layer is usually an inner layer of autoclavable packaging film to protect the integrity of this important layer. The barrier material may be polymeric in nature, such as polyamide, ethylene-vinyl alcohol copolymer, or polyvinyl alcohol copolymer. The barrier material may be metallic, such as a thin layer of aluminum. The barrier layer may be a transparent inorganic oxide coating such as AlOx or SiOx. The barrier layer may be multilayered and contain various layers of barrier materials. The barrier layer may be a mixture of several barrier materials. The barrier layer provides the defined barrier required to preserve the product in the autoclave-sterilized package for a long shelf life, which can be several months or even more than one year.

[39] The barrier layer may be located on the surface of the polypropylene-based outer film. In some embodiments of autoclavable packaging film, the barrier layer is located on the inner surface of the outer polypropylene-based film facing the seal layer. Alternatively, a barrier layer is applied to the surface of the inner film.

[40] The barrier layer reduces the flow of oxygen through the autoclavable packaging film during the shelf life of the packaged product (i.e., while the package is hermetically sealed). In some embodiments, before being subjected to the autoclave sterilization process, the autoclave sterilizable packaging film has an average oxygen transmission rate (OTR) of less than 2 cm ³ /m ² /day, less than 1 cm 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 at 1 atmosphere, 23°C and 50% relative humidity). In some embodiments, after exposure to a representative autoclave sterilization process, the autoclave packaging film has an average OTR value that is less than 2 ^cc /m ³ /day, less than 1 ^cc /m ² /day, less than 0.5 ^cc /m ² / day or less than 0.1 cm ³ / m ² / day. The average OTR may be close to, equal to, or below the minimum detection level of the test device. A representative autoclave sterilization process is completed by cutting a portion of the autoclave sterilizable packaging film to DIN A4 size and subjecting it to a steam sterilization process for 60 minutes at 128°C and 2.5 bar gauge pressure, followed by cooling with a water shower.

[41] The sealing layer of autoclavable packaging film has a composition that allows the formation of a sealed seam, thereby forming an airtight package. As used herein, the term "sealed seam" or "thermal sealed" refers to two or more surfaces that have been bonded together by applying both heat and pressure for a short period of time or through an ultrasonic energy sealing process. Thermal sealing and ultrasonic sealing are well known and widely used packaging processes familiar to those skilled in the art.

[42] The sealing layer is necessarily provided on the surface of the autoclave-sterilizable packaging film to facilitate the sealing function. During use of the autoclavable packaging film in the autoclaveable package, the sealing layer may be thermally sealed to itself or to another packaging component. During thermal sealing, the sealing layer softens to allow a thermally sealable bond to form at a sealing temperature that is below the temperature resistance of the polypropylene-based outer film. The sealing layer softens at a sealing temperature that is lower than the temperature resistance of the outer oriented film. The seal layer should soften and form a seal under sealing conditions (time, temperature and pressure) that do not cause excessive shrinkage or damage to the outer surface of the autoclaveable packaging film.

[43] Autoclavable packaging film is targeted to contain high levels of polyolefin, especially polypropylene, so that it may be acceptable for the recycling process. Polyolefins have relatively low heat resistance compared to materials traditionally used for autoclavable packaging films (eg polyester, aluminum foil, polyamide). Due to their lower heat resistance, autoclave sterilizable packages will be formed using a heat seal process at lower temperatures to avoid any shrinkage or burning. The challenge addressed by the autoclavable packaging films described herein is to include a seal layer that has a low heat seal initiation temperature (HSIT) and high seam strength and seam toughness to withstand both processing in an autoclave, and normal distribution and handling (i.e., drop strength and tensile strength). The seal layer must also contain materials approved for food contact under autoclave sterilization conditions as prescribed by government food safety authorities.

[44] The sealing layer may comprise a low thermal seal onset temperature (HSIT) material. In some embodiments of autoclavable packaging film, the seal layer comprises a polypropylene copolymer having a melting point that is equal to or less than 135°C.

[45] The sealing layer can be formed by any known process. For example, the sealing layer may be a heat-sealable varnish that is applied to other layers of autoclavable packaging film. In other embodiments, the seal layer is formed through an extrusion process in which a polymer melt is applied directly to other layers of the autoclave-sterilizable package. In yet other embodiments, the seal layer may be formed in an off-line coextrusion process (ie, a film cast or blown film process) and subsequently adhered to other layers of autoclaveable packaging film using a layering process. The sealing layer may be enclosed in a multilayer film containing 2, 3, 4 or more layers.

[46] Referring now to FIG. 2, an embodiment of an autoclaveable packaging film 10 comprises a polypropylene-based outer film 20, a barrier layer 40, a seal layer 32, and a protective layer 34. The seal layer 32 and the protective layer 34 are layers within a coextruded multilayer film 30. The outer film 20 on polypropylene base can be located on one main surface of the autoclavable packaging film and becomes the exposed outer surface of the autoclavable packaging. The sealing layer 32 is located on the other main surface of the autoclavable packaging film and becomes the product contact side of the autoclaveable package. The barrier layer 34 is located adjacent to the seal layer 32. The barrier layer 40 is located internal to the surfaces of the autoclaveable packaging film 10. The autoclaveable packaging film has a general composition containing at least 80% polyolefin-based polymers by weight. Autoclavable packaging film may have a general composition of at least 80% polypropylene-based polymers by weight.

[47] The protective layer of the coextruded multilayer film provides additional rigidity and strength to the structure. The protective layer of the coextruded multilayer film can be formulated to provide good adhesion to the remaining layers of the autoclavable packaging film. In some embodiments, the protective layer comprises one or more polypropylene-based polymers. The protective layer, along with other layers of the multilayer film, may also contain other polyolefin-based polymers, such as polyethylene-based polymers.

[48] While the structure of autoclavable packaging film and any packages made from it contains several different elements (outer layer, barrier layer, sealing layer, etc.), the overall composition of the film or package must have large quantities one type of material (polyolefin or, in particular, polypropylene) to facilitate recycling. In the context of this document, the term "overall composition" is used to describe the entire structure of the film or package. Any materials, layers or components that are bonded together in any way are part of the overall composition of this product. Autoclavable packaging films may contain large quantities of polyolefin-based polymers. Packaging films can have large quantities of polypropylene-based polymers. The packaging films described herein, and any autoclavable packaging made from them, may be recyclable in the polypropylene recycling process if the product contains a large amount of polypropylene-based polymers. The mixed polyolefin recycling process can also accept relatively large amounts of polyolefins that are not polypropylene, so products can also contain large amounts of polyolefins that are not polypropylene and still be recyclable.

[49] As used herein, “polyolefin-based polymer” refers to a homopolymer or copolymer having at least one alkene monomer linkage in a repeating polymer backbone. Basic 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 copolymer and cyclic olefin copolymer.

[50] Autoclavable packaging film may have a general composition containing at least 80% polyolefin-based polymers by weight. In other words, considering all materials (polymer and non-polymer) in all autoclave-sterilizable packaging film, at least 80% by weight are polyolefin-based polymers. The autoclaveable packaging film may have a general composition containing a minimum polyolefin-based polymer content of 80%, 82%, 84%, 86%, 88% or 90% by weight. The autoclaveable packaging film may have a general composition containing a maximum polyolefin-based polymer content of 100%, 99%, 98%, 97%, 96% or 95% by weight. For example, an autoclaveable packaging film may have a general composition of 90% to 99% polyolefin-based polymer, or an autoclaveable packaging film may have a general composition of 82% to 100% polyolefin-based polymer by weight.

[51] As used herein, "polypropylene-based polymer" refers to a homopolymer or copolymer having at least one propylene monomer linkage in a repeating polymer backbone. The propylene bond can be represented by the general formula: [CH2-CH(CH3)]n. Such polypropylene may be an impact resistant polypropylene copolymer, a random polypropylene copolymer, or a polypropylene homopolymer, may be syndiotactic or isotactic, and/or may or may not have a structurant. The polypropylene-based polymer may be a copolymer of propylene and an alpha-olefin.

[52] Autoclavable packaging film may have a general composition containing at least 70% polypropylene-based polymers by weight. In other words, considering all materials (polymer and non-polymer) in all autoclave packaging film, at least 70% by weight are polypropylene-based polymers. Autoclavable packaging film may have a general composition containing a minimum polypropylene-based polymer content of 70%, 80%, 85%, 86%, 88% or 90% by weight. Autoclavable packaging film may have a general composition containing a maximum polypropylene-based polymer content of 100%, 99%, 98%, 97%, 96% or 95% by weight. For example, an autoclaveable packaging film may have a general composition of 70% to 98% polypropylene-based polymer, or an autoclaveable packaging film may have a general composition of 80% to 100% polypropylene-based polymer by weight.

[53] In some embodiments, the autoclavable packaging film has a general composition that contains less than 10% polymers other than polyolefin-based polymers by weight. In addition to high polyolefin and polypropylene content, autoclaveable packaging film may have small amounts of non-polyolefin polymers relative to the total composition. Non-polyolefin polymers that can be included in autoclavable packaging film include polyamides, polyacrylates and polyurethanes. These polymers may be present in the extruded layer or within a layer of printing ink or adhesive. Autoclavable packaging film may have a general composition that contains less than 9%, 8%, 7%, 6%, or 5% polymers other than polyolefin-based polymers by weight.

[54] In some embodiments, the autoclavable packaging film is substantially free of polymers other than polyolefin-based polymers. In other words, any non-polyolefin polymers that may be present in autoclaveable packaging film do not affect the essential properties and properties of the film material.

[55] Referring now to FIG. 3, an embodiment of an autoclaveable packaging film 10 comprises a polypropylene-based outer film 20, a barrier layer 40, an inner polypropylene-based film 50, a seal layer 32, and a protective layer 34. The seal layer 32 and the protective layer 34 are layers within a coextruded multilayer film 30. The polypropylene-based outer film 20 may be positioned on one major surface of the autoclaveable packaging film and becomes the exposed outer surface of the autoclaveable packaging film. The sealing layer 32 is located on the other main surface of the autoclavable packaging film and becomes the product contact side of the autoclaveable package. A protective layer 34 is disposed adjacent to a sealing layer 32. A polypropylene-based inner film 50 and a barrier layer 40 are disposed internally relative to the surfaces of the autoclaveable packaging film 10. The autoclaveable packaging film may have a general composition containing at least 80% polymers on a polyolefin based on weight. Autoclavable packaging film has a general composition of at least 80% polypropylene-based polymers by weight.

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

[57] The polypropylene-based inner film can be oriented. The film can be biaxially oriented or uniaxially oriented in any direction. The polypropylene-based inner film is preferably heat-shrinkable (i.e., tempered) so that it maintains its dimensions under elevated temperature conditions that may occur during conversion of the laminate or during use of the laminate (i.e., heat sealing or sterilization in an autoclave). The polypropylene-based inner film, if present, may be the same or different from the polypropylene-based outer film.

[58] The polypropylene-based inner film may be an oriented polypropylene film, such as biaxially oriented polypropylene. Oriented polypropylene film may have one or more layers and may have special finishes such as a matte finish. Any of the layers of oriented polypropylene film may contain a pigment, such as titanium dioxide, to make the film opaque to visible light. The film may be a biaxially oriented polypropylene foam, resulting in a film that is opaque to visible light. Biaxially oriented polypropylene can be transparent to visible light. In some embodiments, the polypropylene-based outer film is a biaxially oriented polypropylene film that substantially comprises polypropylene.

[59] In embodiments that include a polypropylene-based inner film, the polypropylene-based inner film may be the same as or different from the polypropylene-based outer film. Commercial examples of films that can be used as polypropylene backing films include Bicor™ NND20 (non-thermal sealable single-sided BOPP available from Jindal Films), PL1 (non-thermal sealable single-sided BOPP available from Polibak Plastik Film San. ve Tic. A.S.) and PPTE_LAM (non-thermal sealable, single-sided, supplied by Poligal.

[60] The barrier layer may be a coating or spray that is applied to one of the films used to make the autoclavable packaging film. For example, the barrier layer 40 shown in the embodiment shown in FIG. 3 may be a silica-based material that has been applied to a polypropylene-based inner film 50 positioned between the outer polypropylene-based film and the inner polypropylene-based film. Or the barrier layer 40 shown in the embodiment shown in FIG. 3 may be a silica-based material that has been applied to the polypropylene-based outer film 20 located between the polypropylene-based outer film and the polypropylene-based inner film. Alternatively, the barrier layer may be a silica-based material applied to the side of the polypropylene-based inner film that faces the seal layer (this embodiment is not shown in the figures).

[61] Any embodiments of autoclavable packaging film may contain other materials and layers. For example, the film structure may contain either extruded bond layers or other adhesive layers for bonding dissimilar materials. The film may contain layers of printing ink in any position of the structure.

[62] Also disclosed herein is a polypropylene-based laminate film suitable for autoclavable packaging. An embodiment of polypropylene-based laminate film 60 is shown in FIG. 4. The polypropylene-based laminate film has an outer oriented film 70, a barrier layer 80, and a multi-layer film 90 containing a sealing layer 92. The polypropylene-based laminate film can be thermally sealed to itself (sealing layer to sealing layer) at a sealing temperature of less than 130 °C using a pressure of 440 N/15 ^cm2 and a dwell time of 1 second. In other words, when thermally sealed to themselves under these conditions, the sealing layers form a strong seal that is more than just tacky. A strong weld can be determined by measuring the force to separate the materials, with an average weld strength of at least 10 N/15 mm using ASTM F88 (grip separation at 100 mm/min). In some embodiments, the sealed seam strength of the polypropylene-based laminate film when heat sealed to itself is greater than 30 N/15 mm, 40 N/15 mm, or greater than 50 N/15 mm.

[63] In some embodiments of autoclaveable polypropylene-based packaging film or laminate film, the outer film, inner film, and laminate film are substantially free of polymers other than polyolefins.

AUTOCLAVABLE PACKAGING

[64] This document describes autoclavable packaging films and polypropylene-based laminates suitable for autoclaveable packaging, as well as autoclavable packages and shelf-stable packaged products made from them. As used herein, "autoclaveable packaging film" or "autoclaveable packaging" is a film or package made from film that can be filled with a product, sealed, and remain sealed after a typical autoclave sterilization process.

[65] Examples of autoclavable package formats include, but are not limited to, pouch or pouch, stand-up pouch (as shown in FIG. 5), tray, cup or bowl with lid, or flow package. Autoclavable packaging may be made entirely from one or more autoclavable packaging films as described herein. The autoclavable packaging may be made from various components, including at least one autoclavable packaging film, as described herein. Any components of autoclavable packaging that are not autoclavable packaging films described herein may also have large amounts of polypropylene polymer. In some embodiments of an autoclavable package, the package is made of at least one film as described herein and at least one other component, wherein the other component comprises at least 90% polypropylene-based polymer by weight, such that that all packaging is recyclable through the polypropylene recycling process.

[66] The autoclave-sterilizable package contains at least one sealed seam to enable the components of the package to be joined, the package to be formed, and the package to be hermetically sealed. An example of an autoclavable package 100 that contains an autoclavable packaging film 110 and a sealed seal 114 is shown as a stand-up pouch in FIG. 5. In this embodiment, the autoclavable packaging is constructed entirely from the autoclavable packaging films described herein, using sealed seams to form and close the package.

[67] In some embodiments of autoclavable packaging, certain components of the packaging are not recyclable in the polypropylene recycling process. In this case, the packaging components can be separated before recycling and/or disposal. Separation of packaging components can be accomplished by peeling off the sealed seams.

[68] In some embodiments of autoclavable packages formed from autoclaveable packaging film, the package has at least 90% polyolefin-based materials or at least 80% polyolefin-based materials by weight. In some embodiments of autoclavable packages formed from autoclavable packaging film, the package has at least 90% polypropylene-based materials or at least 80% polypropylene-based materials by weight. In some embodiments of autoclavable packages formed from autoclavable packaging film, the package has at least 90% polyolefin-based materials and at least 80% polypropylene-based materials by weight.

PACKED PRODUCT FOR LONG STORAGE

[69] Described herein are autoclavable packaging films and polypropylene-based laminate films suitable for autoclaveable packaging, as well as autoclavable packages and shelf-stable packages made therefrom, as shown in FIG. 6. An autoclavable packaging film 210 is used to form an autoclavable package containing a product 220, resulting in a shelf-stable packaged product 200. As discussed previously, sealed seams 214 are used to form an autoclavable package and hermetically seal the shelf-stable packaged product 200.

[70] In some embodiments of a shelf-stable packaged product, the product in the autoclavable package is a product that would be perishable if not for the sterilization process to which it was subjected while being hermetically sealed within the autoclavable packaging film. In the context of this document, the product may be a perishable food product where the sterilization process (i.e., autoclave sterilization) allows the product to be stored and preserved under ambient conditions for many months or years. The product undergoes a sterilization process while being hermetically sealed in a package formed from autoclavable packaging film. After sterilization, autoclavable packaging prevents the influx of oxygen (i.e. it has high oxygen barrier properties), which helps to extend the shelf life of the product.

[71] In some embodiments of a shelf-stable packaged product, the product in the autoclave-sterilizable package is a product that maintains sterility by being sterilized while sealed within the package.

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

EXAMPLES AND DATA

[73] Five samples of exemplary autoclavable packaging films were collected for testing. Details of Examples 1-5 can be found in Table 1 below.

[74] Each of Examples 1-4 were three-layer laminates and contained an outer film on a polypropylene base, which is a biaxially oriented polypropylene film (materials based on 100% polypropylene), a protective layer, which is a coating of silicon oxide applied to the biaxially oriented polypropylene film (materials based on 100% polypropylene) and multilayer film (materials based on 100% polypropylene) containing a sealing layer with a low sealing start temperature.

[75] Example 5 was a two-layer laminate and included a polypropylene-based outer film that is a biaxially oriented polypropylene film (100% polypropylene based materials) with a barrier layer of silicon oxide coating applied to the outer biaxially oriented polypropylene film ( materials based on 100% polypropylene) and multilayer film (materials based on 100% polypropylene) containing a sealing layer with a low sealing start temperature.

[76] The films of Examples 1-5 were bonded together using adhesive lamination and, in some cases, also contained ink. The adhesive used in these examples was a two-part solvent-based system of Dow Adcote 811A and Catalyst C9L10 available from Dow Chemical. The printing ink was of a grade that could withstand autoclave sterilization as is known in the art. The films of Examples 1-4 were layered such that the silica coating on the inner biaxially oriented polypropylene film was oriented to face the outer oriented polypropylene film. In Example 5, the silica coating on the outer biaxially oriented polypropylene film was oriented to face the multilayer film.

[77] For each layer of films from Examples 1-5, the amounts of polyolefin-based material and polypropylene-based material are indicated in Table 1. The biaxially oriented polypropylene films used contained 100% polypropylene-based materials (and therefore also 100% polyolefin-based) . The adhesives and printing inks were based on other polymers, so they contained 0% polyolefin based materials and 0% polypropylene based materials. The SiOx-coated biaxially oriented polypropylene film contained a non-olefin based varnish and an inorganic coating, neither of which are polyolefin or polypropylene based materials. Thus, only a portion of the mass of this layer (for example, 16.3 g/m ² out of 18.1 g/m ² ) is taken into account in the total composition of PO or PP. The general composition of Examples 1-5, relating to polyolefin-based (PO) materials and polypropylene-based (PP) materials, is shown in percentage by weight in Table 1.

[78] The oxygen transmission rate (OTR) is indicated for each of Examples 1-5. OTR was measured according to ASTM F1927 under conditions of 1 atmosphere, 23°C and 50% relative humidity. OTR after autoclave sterilization was measured after the autoclaved packaging film was subjected to a representative autoclave sterilization process (cutting off a portion of the autoclave sterilizable packaging film to DIN A4 size and subjecting it to a steam sterilization process for 60 minutes at 128°C and 2 gauge pressure .5 bar followed by cooling with a water shower). Autoclavable packaging films maintain excellent OTR even after undergoing autoclave sterilization processing.

Table 1 Etc. Structure Layer Mass
(g/ ^m2 ) Polio-
lefin
Weight
(g/ ^m2 ) Polypro-
sawn
Weight
(g/ ^m2 ) OTR
(cm ³ / m ² / day) After sterilization in an autoclave
OTR
(cm ³ / m ² / day) 1 BOPP* 18.1 18.1 18.1 0.3 0.5 adhesive 4 0 0 BOPP/SiOx 18.1 16.3 16.3 adhesive 3 0 0 multilayer film 73.4 73.4 73.4 General composition: 92%PO 92%PP 2 BOPP 18.1 18.1 18.1 0.09 0.49 adhesive 4 0 0 BOPP/SiOx 18.1 16.3 16.3 adhesive 3 0 0 multilayer film 78.3 78.3 78.3 General composition: 93%PO 93%PP 3 BOPP 18.1 18.1 18.1 0.08 0.37 printing ink 3 0 0 adhesive 4 0 0 BOPP/SiOx 18.1 16.3 16.3 adhesive 3 0 0 multilayer film 78.3 78.3 78.3 General composition: 91%PO 91%PP 4 BOPP 18.1 18.1 18.1 0.1 0.17 adhesive 4 0 0 BOPP/SiOx 18.1 16.3 16.3 adhesive 3 0 0 multilayer film 58.7 58.7 58.7 General composition: 91%PO 91%PP 5 BOPP/SiOx 18.1 16.3 16.3 0.1 0.18 adhesive 4 0 0 multilayer film 63 63 63 General composition: 93%PO 93%PP

*BOPP=Biaxially Oriented Polypropylene Film

[79] As previously discussed, the polypropylene-based outer film may have a surface coating such as a matte varnish. Matte varnish provides additional heat resistance, allowing the use of a thinner polypropylene-based outer film. Additionally, a thinner multilayer film can be used. The resulting film will have a lower overall polyolefin and polypropylene composition, bringing both closer to 80%. Details of this proposed structure are shown in Table 2.

table 2 Structure Layer Mass
(g/ ^m2 ) Polyolefin
Weight
(g/ ^m2 ) Polypropylene
Weight
(g/ ^m2 ) Matt lacquer 2 0 0 BOPP 11.1 11.1 11.1 adhesive 4 0 0 BOPP/SiOx 18.1 16.3 16.3 adhesive 3 0 0 multilayer film 27 27 27 General composition: 83%PO 83%PP

[80] As discussed, portions of any of the films used in autoclavable packaging films may contain polyolefin-based polymers other than polypropylene. For example, the structure of Example 4 can be produced using a multilayer film containing approximately 20% polyethylene-based material. It is envisaged that the multilayer film can contain small amounts of polyethylene-based materials in the various layers of the film and still maintain the properties required for autoclave sterilization. The result of this inclusion of polyethylene-based materials is that the overall composition of the autoclavable packaging film in Example 8 remains the same relative to polyolefin-based materials, but is reduced to 80% relative to polypropylene-based materials when compared to Example 4. Details of the proposed structure of this type are shown in Table 3.

Table 3 Structure Layer Mass
(g/ ^m2 ) Polyolefin
Weight
(g/ ^m2 ) Polypropylene
Weight
(g/ ^m2 ) BOPP 18.1 18.1 18.1 adhesive 4 0 0 BOPP/SiOx 18.1 16.3 16.3 adhesive 3 0 0 multilayer film 58.7 58.7 47.0 General composition: 91%PO 80%PP

[81] Thermal seal data for Examples 2, 3 and 4 are shown in Table 4 below. The films were sealed to each other (seal layer to seal layer) using Teflon-coated thermal seal rods heated to temperatures ranging from 120°C to 150°C. Sutures were created under conditions involving 1 second and a pressure of 440 N/15 cm ² . The seam strength of said seam was then tested using ASTM F88 test method (separation speed at 100 mm/min) and the results are shown in Table 2. Additionally, the film samples were sealed and then subjected to steam autoclave sterilization conditions for 60 minutes at 128° C and an excess pressure of 3.5 bar. Cooling with a water shower was used before re-testing the seam strength. All results are shown in Table 4. The sealing layers of autoclavable packaging film can be sealed at low temperatures, such as 130°C, minimizing any damage to the outer layers of the film structure that may occur at higher sealing temperatures. Additionally, the strength of the seam remains high after exposure to autoclave sterilization conditions.

Table 4 Sealing temperature (°C) Example 2
Before autoclave sterilization (N/15 mm) Example 2
After autoclave sterilization (N/15 mm) Example 3 Before autoclave sterilization (H/15 mm) Example 3 After autoclave sterilization (H/15 mm) Example 4 Before autoclave sterilization (H/15 mm) Example 4 After autoclave sterilization (H/15 mm) 120 0 24 2.2 21.5 12.2 21.9 125 1.2 30.9 9.3 40.3 39.6 27.5 130 50.6 48 49.3 48.7 50.6 46.8 135 63.6 51.9 61.8 54.4 52.8 51.3 140 63.7 51.9 64.5 51.5 56.1 54.1 150 59.5 48.8 59.6 54.4 56.7 56.8 160 N/A N/A N/A N/A 68.1 67.1

OPTIONS FOR PRODUCING AUTOCLAVE STERILIZABLE PACKAGING FILM

(i) Autoclavable packaging film containing:

outer film on a polypropylene base,

barrier layer and

sealing layer

wherein the autoclavable packaging film has a general composition containing at least 80% polyolefin-based polymers by weight.

(ii) An autoclavable packaging film according to any other embodiment, wherein the polypropylene-based outer film is oriented.

(iii) An autoclaveable packaging film according to any other embodiment, wherein the barrier layer comprises a metal or inorganic oxide.

(iv) An autoclavable packaging film according to embodiment (iii), wherein the barrier layer is applied to the surface of the polypropylene-based outer film.

(v) An autoclaveable packaging film according to any other embodiment, wherein the overall composition of the autoclaveable packaging film contains at least 80% polypropylene-based polymers by weight.

(vi) An autoclaveable packaging film according to any other embodiment, wherein the overall composition of the autoclaveable packaging film contains at least 90% polyolefin-based polymers by weight.

(vii) An autoclaveable packaging film according to any other embodiment, wherein the sealing layer is within the multilayer film, and the multilayer film also includes a protective layer.

(viii) Autoclavable packaging film containing:

outer film on a polypropylene base,

inner film on a polypropylene base,

a barrier layer applied to at least one surface of the inner and outer polypropylene-based film,

multilayer film containing a sealing layer,

wherein the autoclavable packaging film has a general composition containing at least 80% polypropylene-based polymers.

(ix) An autoclavable packaging film according to embodiment (viii), wherein at least one of the polypropylene-based inner or outer films is oriented.

(x) An autoclaveable packaging film according to any other embodiment, wherein the seal layer comprises a polypropylene copolymer having a melting point that is less than or equal to 135°C.

(xi) An autoclaveable packaging film according to any other embodiment, wherein the autoclaveable packaging film can be thermally sealed to itself at a sealing temperature of less than 130° C. using sealing conditions of 1 second and 440 N/15 cm ² .

(xii) An autoclaveable packaging film according to any other embodiment, wherein the outer oriented film and seal layer are substantially free of polymers other than polyolefins.

OPTIONS FOR IMPLEMENTING AUTOCLAVE STERILIZABLE PACKAGING

(I) An autoclavable package formed from one or more autoclavable packaging films according to any embodiment of an autoclavable packaging film.

(II) An autoclavable package comprising an autoclavable packaging film containing at least 80% polyolefin-based materials by weight, wherein the autoclavable package comprises a sealed seam.

(III) An autoclave-sterilizable package according to embodiment (I) or (II), wherein the autoclave-sterilizable packaging film further comprises a barrier layer, and the autoclave-sterilizable packaging film has an oxygen transmission rate of less than 2.0 cm ³ /m ² in day (ASTM F1927, 23°C, 50% relative humidity).

(IV) The autoclaveable packaging according to embodiment (I) or (II), wherein the autoclaveable packaging film further comprises a barrier layer, and the autoclaveable packaging film has an oxygen transmission rate of less than 1.0 cm ³ /m ² in day (ASTM F1927, 23°C, 50% relative humidity).

(V) An autoclavable package according to any other embodiment, wherein the autoclavable package substantially comprises one or more autoclavable packaging films, each containing at least 80% polypropylene-based materials and at least one sealed seam.

OPTION FOR PRODUCING PACKED PRODUCT WITH LONG-TERM STORAGE

(a) A packaged shelf-stable product containing:

an autoclavable packaging film having a general composition containing at least 80% polypropylene-based polymers, and

a product hermetically sealed in an autoclavable packaging film, which product would be perishable were it not for the sterilization process to which it was subjected while hermetically sealed in an autoclavable packaging film.

OPTION OF IMPLEMENTATION OF THE METHOD

(A) A method for producing a packaged shelf-stable product, comprising:

i) forming the original package by thermally sealing the autoclavable packaging film of any previous claim to itself using a temperature that is less than or equal to 160°C,

ii) filling the original packaging with the product,

iii) heat sealing of the original packaging to hermetically seal the product in the final packaging, and

iv) Subjecting the final packaging to an autoclave sterilization process.

Claims (13)

1. Autoclavable packaging film containing: outer film on a polypropylene base, inner film on a polypropylene base, a barrier layer applied to at least one surface of the inner and outer polypropylene-based films, multilayer film containing a sealing layer, wherein the autoclave-sterilizable packaging film has a general composition containing at least 80% polypropylene-based polymers by weight. 2. Autoclavable packaging film according to claim 1, characterized in that at least one of the inner or outer polypropylene-based films is oriented. 3. Autoclavable packaging film according to claim 1, characterized in that the sealing layer contains a polypropylene copolymer having a melting point less than or equal to 135°C. 4. Autoclavable packaging film according to claim 1, characterized in that the barrier layer contains a metal or inorganic oxide. 5. Autoclave-sterilizable packaging formed from one or more autoclavable packaging films according to claim 1. 6. Autoclave-sterilizable packaging according to claim 5, characterized in that the autoclave-sterilizable packaging film additionally contains a barrier layer, and the autoclave-sterilizable packaging film has an oxygen transmission rate of less than 2.0 cm ³ /m ² per day (ASTM F1927, 23°C, 50% relative humidity). 7. Autoclave-sterilizable packaging according to claim 5, characterized in that the autoclave-sterilizable packaging film additionally contains a barrier layer, and the autoclave-sterilizable packaging film has an oxygen transmission rate of less than 1.0 cm ³ /m ² per day (ASTM F1927, 23°C, 50% relative humidity). 8. The autoclavable packaging of claim 5, wherein the autoclavable packaging substantially comprises one or more autoclavable packaging films, each containing at least 80% polypropylene-based materials by weight and by weight. at least one sealed seam.

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