Retortable packaging film

Abstract

A retortable package film is disclosed. The retortable package film includes a laminate including a BOPP film and an MDOPP film. The retortable package film further includes a seal layer disposed on the laminate. The seal layer includes a blend including a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE. The seal layer has a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg. The retortable package film further includes a total composition including at least 80% polypropylene by weight.

Description

Technical Field

[0001] This application generally relates to a retortable package film, a hermetically sealed packaged food containing the retortable package film, and a method of manufacturing the retortable package film.

Background Art

[0002] Retortable packages such as stand-up pouches are typically made from multi-polymer laminates such as PET / OPA / PP (polyester / oriented polyamide / polypropylene), and PET / ALU / PP (polyester / aluminum / polypropylene). However, due to the presence of materials such as PET, ALU, and OPA, such multi-polymer laminates may not comply with certain recycling guidelines (e.g., CEFLEX).

[0003] To comply with recycling guidelines, retortable packages can be made using mono-polymer laminates (e.g., PE, or PP-based laminates). However, making a retortable package from a mono-polymer laminate can present several challenges. For example, a retortable package may need to have high sealing strength and exhibit a straight-line tear property in one direction to facilitate opening of the retortable package while being sufficiently robust for retort processing.

[0004] Conventionally, linear tear properties are typically imparted onto a multi-polymer laminate via a scoring process (e.g., laser scoring). However, the scores created from such scoring processes can be visible features that can have an adverse effect on the aesthetic appearance of a retortable package made from the multi-polymer laminate. Scoring may also not be feasible with a mono-polymer laminate. Further, the mono-polymer laminate may need to be heat-sealed at a relatively low temperature (e.g., 120 °C to 140 °C) so that the mono-polymer laminate does not suffer damage (e.g., melting, warping, or clouding).

[0005] Accordingly, there is a need for a retortable package film that meets recycling guidelines, has high seal strength, is sufficiently robust for retort processing, exhibits linear tear properties in one direction that facilitate opening of the retortable package, and does not require visual features (e.g., scores) that can be detrimental to the aesthetic appearance of the retortable package, and that includes a high level of polyolefin (i.e., 80% or more by weight, or more than 90%). SUMMARY OF THE INVENTION

[0006] A retortable package film has been developed. The retortable package film includes a mono-polymer laminate and can thus comply with certain recycling guidelines. Further, the mono-polymer laminate can provide suitable robustness for the retortable package film to withstand retort and other high-temperature sterilization processes.

[0007] The retortable package film further includes a sealing layer disposed on the monopolymer laminate. The sealing layer can provide high sealing strength at a low sealing start temperature. In other words, the retortable package film may be sealed at a relatively low temperature (e.g., 120 °C to 140 °C) and can provide high sealing strength (e.g., exceeding 10 N / 15 mm), which may be essential for retort processing. The monopolymer laminate may be elastic and may not be damaged by heat sealing by having a low sealing start temperature.

[0008] The sealing layer may be suitable for an extrusion coating on the monopolymer laminate and may not be suitable for blown film extrusion and cast film extrusion. Specifically, the sealing layer may be designed for extrusion coating and may be suitable for extrusion coating. The sealing layer may not be ideal for blown film extrusion and cast film extrusion. A sealing layer designed for and suitable for blown film extrusion typically has a melt flow index of less than 5 g / 10 min and is not suitable for the sealing layer of the present invention. A sealing layer designed for and suitable for cast film extrusion typically has a melt flow index of less than 10 g / 10 min or less than 7 g / 10 min and is not suitable for the sealing layer of the present invention.

[0009] The retortable package film can exhibit linear tear properties (e.g., along the machine direction). The linear tear properties may be provided by the orientation of one or more films of the monopolymer laminate. As a result, the retortable package film can exhibit linear tear properties without using a score or any visible feature. Therefore, any graphic or other appearance feature that can be printed on a retortable package made from the retortable package film may not be obstructed by such a score or visual feature. This may improve the aesthetic appearance of the retortable package.

[0010] The straight-line tear property may facilitate the opening of a retortable package made from a retortable packaging film. Advantageously, the sealing layer may have a low sealing start temperature while not adversely affecting the straight-line tear property of the retortable packaging film.

[0011] The retortable packaging film may comply with recycling guidelines, may have a high sealing strength, may be sufficiently robust for retort processing, and may exhibit straight-line tear properties in one direction (e.g., the machine direction) to facilitate the opening of a retortable package made from the retortable packaging film.

[0012] One embodiment of the present disclosure is a retortable packaging film. The retortable packaging film includes a laminate including a biaxially oriented polypropylene (BOPP) film and a machine direction oriented polypropylene (MDOPP) film. The retortable packaging film further includes a sealing layer disposed on the laminate. The sealing layer includes a blend including a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of low-density polyethylene (LDPE) and medium-density polyethylene (MDPE). The sealing layer has a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg. The retortable packaging film further includes a total composition including at least 80% polypropylene by weight.

[0013] The sealing layer may provide a high sealing strength at a low sealing start temperature. In other words, the retortable packaging film may be sealed at a relatively low temperature (e.g., 120°C to 140°C) and may provide a high sealing strength (e.g., greater than 10 N / 15 mm), which may be essential for retort processing. The laminate including the BOPP film and the MDOPP film may not be damaged for heat sealing at a relatively low temperature.

[0014] The sealing layer may be suitable for extrusion coating and may be unsuitable for blown film extrusion and cast film extrusion. Specifically, the melt flow index of the sealing layer (i.e., between 5 g / 10 min and 25 g / 10 min at 230 °C / 2.16 kg) may make the sealing layer suitable for extrusion coating. The sealing layer may not be ideal for blown film extrusion and cast film extrusion. A sealing layer designed for and suitable for blown film extrusion typically has a melt flow index of less than 5 g / 10 min and is not suitable for the sealing layer of the present invention. A sealing layer designed for and suitable for cast film extrusion typically has a melt flow index of less than 10 g / 10 min, or less than 7 g / 10 min, and is not suitable for the sealing layer of the present invention.

[0015] The retortable package film may exhibit linear tear properties (e.g., along the machine direction). The linear tear properties may be provided by the MDOPP film of the laminate. Advantageously, the retortable package film may exhibit linear tear properties without using a score or any visible feature. Thus, any graphic or other appearance feature that may be printed on a retortable package made from the retortable package film may be free from interference from such scores or visual features. This may improve the aesthetic appearance of the retortable package.

[0016] The linear tear properties may facilitate the opening of a retortable package made from the retortable package film. Advantageously, the sealing layer may have a low sealing start temperature while not adversely affecting the linear tear properties of the retortable package film.

[0017] A retortable package film can comply with recycling guidelines because the total composition of the retortable package film contains at least 80% polypropylene by weight. Further, the retortable package film can be sufficiently robust for retort processing. The retortable package film can have high sealing strength due to the sealing layer. Advantageously, the sealing layer can provide high sealing strength at a low sealing start temperature so that the laminate does not melt, warp, or become cloudy. Further, the retortable package film can exhibit linear tear characteristics in one direction (e.g., the machine direction) to facilitate opening of a retortable package made from the retortable package film.

[0018] In some embodiments, the blend of the sealing layer contains between 4% and 50% long-chain branched polyethylene by weight and 50% to 90% polypropylene terpolymer by weight.

[0019] In some embodiments, the polypropylene terpolymer has a melting temperature above 130°C.

[0020] In some embodiments, the sealing layer has a sealing start temperature below 140°C when measured using ASTM F88 Technique A.

[0021] In some embodiments, the melt flow index of the sealing layer is between 5 g / 10 min and 15 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg.

[0022] In some embodiments, the sealing layer is not oriented. The non-oriented sealing layer can enable the sealing layer to have a low sealing start temperature.

[0023] In some embodiments, the sealing layer is extrusion coated onto the laminate. The melt flow index of the sealing layer can render the sealing layer suitable for extrusion coating. The melt flow index of the sealing layer can render the sealing layer unsuitable for blown film extrusion and cast film extrusion.

[0024] In some embodiments, the laminate further includes a barrier layer attached to a BOPP film or an MDOPP film. The barrier layer can impart various barrier properties, such as moisture barrier properties, gas barrier properties, and / or odor barrier properties, to a retortable package film.

[0025] In some embodiments, the barrier layer includes one of a metal layer or an oxide coating layer deposited on the surface of a BOPP film or an MDOPP film.

[0026] In some embodiments, the barrier layer includes a polymeric barrier material.

[0027] In some embodiments, the total composition includes at least 90% by weight of polypropylene.

[0028] In some embodiments, the total composition includes less than 20% by weight of non-polyolefin material.

[0029] In some embodiments, the total composition includes less than 10% by weight of non-polyolefin material.

[0030] In some embodiments, the MDOPP film is located on the outer surface of a retortable package film.

[0031] In some embodiments, the BOPP film is located on the outer surface of a retortable package film.

[0032] Another embodiment of the present disclosure is a hermetically sealed packaged food. The hermetically sealed packaged food includes a retortable package film. The hermetically sealed packaged food may be recyclable and may have a linear tear property of the retortable package film. As a result, the hermetically sealed packaged food can be easily opened when desired.

[0033] Another embodiment of the present disclosure is a method of manufacturing a retortable package film. The method includes laminating a BOPP film to an MDOPP film to form a pre-laminate. The method further includes extrusion coating a seal layer onto the pre-laminate. The seal layer includes a blend including a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE. The seal layer has a melt flow index between 5 g / 10 min and 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg.

[0034] Another embodiment of the present disclosure is a method of manufacturing a retortable package film. The method includes extruding and orienting the film in the machine direction to manufacture an MDOPP film. The method further includes extrusion coating a seal layer onto the MDOPP film. The method further includes applying a barrier coating to the BOPP film. The method further includes adhering and laminating the MDOPP film and the BOPP film. The seal layer includes a blend including a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE. The seal layer has a melt flow index between 5 g / 10 min and 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg.

[0035] There are several aspects of the subject matter that may be embodied separately or together. These aspects may be employed alone or in combination with other aspects of the subject matter described herein, and the description of these aspects is not intended together to preclude claiming these aspects separately or in different or distinct combinations thereof.

[0036] Brief Description of the Drawings The present disclosure may be more fully understood in consideration of the following detailed description of various embodiments of the present disclosure in connection with the accompanying drawings.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0038] The drawings are not necessarily to scale. Like numbers used in the drawings refer to like components. However, it will be understood that the use of a number to refer to a component in a given drawing is not intended to limit the component in another drawing that is labeled with the same number.

[0039] Detailed Description A retortable package film has been developed. The retortable package film includes a laminate including a BOPP film and an MDOPP film. The retortable package film further includes a seal layer disposed on the laminate. The seal layer includes a blend including a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE. The seal layer has a melt flow index between 5 g / 10 min and 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg. The retortable package film further includes a total composition including at least 80% polypropylene by weight.

[0040] The seal layer can provide high sealing strength at a low sealing start temperature. In other words, the retortable package film may be sealed at a relatively low temperature (e.g., 120°C to 140°C) and can provide a high sealing strength (e.g., greater than 10 N / 15 mm) that may be essential for retort processing. Laminates including a BOPP film and an MDOPP film may not be damaged for heat sealing at relatively low temperatures. The laminate may be elastic and may not be damaged by heat sealing by having a seal layer with a low sealing start temperature.

[0041] The sealing layer may be suitable for extrusion coating and may be unsuitable for blown film extrusion and cast film extrusion. Specifically, the melt flow index of the sealing layer (i.e., between 5 g / 10 min and 25 g / 10 min at 230 °C / 2.16 kg) may make the sealing layer suitable for extrusion coating and unsuitable for blown film extrusion processing. The melt flow index of the sealing layer may further make the sealing layer unsuitable for cast film extrusion processing. In other words, the sealing layer may not be ideal for blown film extrusion and cast film extrusion. A sealing layer designed for and suitable for blown film extrusion typically has a melt flow index of less than 5 g / 10 min and is not suitable for the sealing layer of the present invention. A sealing layer designed for and suitable for cast film extrusion typically has a melt flow index of less than 10 g / 10 min or less than 7 g / 10 min and is not suitable for the sealing layer of the present invention.

[0042] The retortable package film may exhibit linear tear properties (e.g., along the machine direction). The linear tear properties may be provided by the MDOPP film of the laminate. Advantageously, the retortable package film may exhibit linear tear properties without including a score or any other visible feature. Thus, any graphic or other appearance feature that may be printed on a retortable package made from the retortable package film may be free from interference from such scores or visible features. This may improve the aesthetic appearance of the retortable package.

[0043] The linear tear properties may facilitate the opening of a retortable package made from the retortable package film. Advantageously, the sealing layer may have a low sealing start temperature while not adversely affecting the linear tear properties of the retortable package film.

[0044] A retortable package film can comply with recycling guidelines because the total composition of the retortable package film contains at least 80% polypropylene by weight. Further, the retortable package film can be sufficiently robust for retort processing. The retortable package film can have high seal strength due to the seal layer. Advantageously, the seal layer can provide high seal strength at a low seal start temperature so that the laminate does not melt, warp, or cloud. Further, the retortable package film can exhibit linear tear characteristics in one direction (e.g., the machine direction) to facilitate opening of a retortable package made from the retortable package film.

[0045] As used herein, the terms "first" and "second" are used as identifiers. Accordingly, such terms should not be construed as limitations of the present disclosure. When used in conjunction with a feature or element, the terms "first" and "second" may be interchanged throughout the embodiments of the present disclosure.

[0046] As used herein, the term "film" is a material having a very high ratio of length or width to thickness. The film has two major surfaces defined by the length and the width. The film typically has good flexibility and can be used for a wide range of applications. The film can also be of a suitable thickness and / or material composition to be flexible, semi-rigid, or rigid. The film may be described as single-layer or multi-layer.

[0047] As used herein, the terms "inner" and "outer" refer to the major surfaces of the film or layer.

[0048] As used herein, the term "retort treatment" refers to a process in which food, medicine, or other items packaged in a flexible package are heated under high pressure (e.g., in the presence of water, steam, or pressurized steam) at a high temperature (e.g., 104°C to 149°C, or 120°C to 135°C) for a long period of time, e.g., 10 to 60 minutes. The term "retort treatment" may also include other high-temperature sterilization treatments such as hot filling.

[0049] As used herein, the term "retortable package" refers to a package that is hermetically sealed and can maintain its hermetically sealed state during retort processing. For example, a retortable package can maintain its hermetically sealed state during the cooking of a food composition hermetically sealed within the retortable package. The term "retortable package film" refers to a film that can be used to form a retortable package.

[0050] As used herein, the term "laminate" refers to a product made by bonding together two or more films or other materials. The laminate may be made by any lamination method. For example, lamination can be achieved by joining films together with an adhesive, by joining them with heat and pressure, and further by spreading coatings and extrusion coatings. The term "laminate" also includes coextruded multilayer films containing one or more adhesive layers.

[0051] As used herein, the term "prelaminate" refers to a laminate to which one or more polymer layers can be attached by coating, adhesion, or other means.

[0052] As used herein, the term "BOPP film" refers to a biaxially oriented polypropylene film. A BOPP film is a polypropylene film that has been subjected to a stretching process in both the machine direction and the transverse direction.

[0053] As used herein, the term "MDOPP film" refers to a polypropylene film oriented in the machine direction. An MDOPP film is a polypropylene film that has been subjected to a stretching process in the machine direction.

[0054] As used herein, the term "sealing layer" refers to a layer of a film, sheet, etc. that is involved in sealing, refers to itself, and / or refers to another layer of the same or a different film, sheet, etc.

[0055] As used herein, the term "terpolymer" refers to a copolymer produced from three different monomers. The term "polypropylene terpolymer" refers to a polypropylene molecular chain modified with two additional comonomers in a polymerization process. Examples of the two additional comonomers can include ethylene and / or C4 - C16 α-olefins, ethylene and / or C4 - C8 α-olefins, and ethylene and butylene.

[0056] As used herein, the term "low density polyethylene", or "LDPE", typically refers to a branched-chain homopolymer having a density of 0.910 g / cm 3 ~0.930 g / cm 3 and copolymers containing polar groups resulting from copolymerization (e.g., with vinyl acetate, ethyl acrylate, etc.).

[0057] As used herein, the term "medium density polyethylene", or "MDPE", typically refers to a branched-chain homopolymer having a density of 0.928 g / cm 3 ~0.940 g / cm 3 Linear medium density polyethylene (LMDPE) is an example of medium density polyethylene.

[0058] As used herein, the term "melt flow index," or "MFI," refers to a measure of the ease of flow of a melt of a polymer. The melt flow index means the amount, in grams, of resin that can be extruded through a plastometer, or rheometer (as defined in ASTM D1238), in 10 minutes at a given temperature and force.

[0059] As used herein, the term "melting temperature," or "Tm," refers to the temperature at which the solid and liquid phases of a material can coexist in equilibrium.

[0060] As used herein, the term "sealing start temperature" refers to the sealing temperature at which a sealing strength of approximately 5 N / 15 mm is achieved. The sealing start temperature can be evaluated using ASTM F88.

[0061] As used herein, the term "orientation" refers to a film, sheet, web, etc. that is stretched in at least one of the machine direction and the transverse direction. The terms "non-oriented," or "not oriented," refer to a film, sheet, web, etc. that substantially does not include orientation after formation.

[0062] As used herein, the term "extrusion coating" refers to a process of applying a molten coating material onto at least a portion of a substrate, optionally under pressure and / or at an elevated temperature.

[0063] As used herein, the term "barrier layer" refers to a layer of a film that includes any material that controls the permeation elements of the film. The barrier layer can provide, for example, an oxygen barrier, a moisture barrier, a chemical barrier, a thermal barrier, and / or an odor barrier.

[0064] As used herein, the term "adhesive layer" refers to a layer having the primary function of joining two adjacent layers together. The adhesive layer is positioned between two layers of a multilayer film and can hold the two layers in a predetermined position relative to each other and prevent unwanted delamination. Unless otherwise indicated, the adhesive layer can have any suitable composition that provides a desired level of adhesion to one or more surfaces in contact with the adhesive layer material. The adhesive layer can alternatively be referred to as a "bonding layer".

[0065] As used herein, the term "polyethylene" refers to a homopolymer or copolymer having at least one ethylene monomer bond within the repeating backbone of the polymer. The ethylene bond can be represented by the following general formula: [CH2-CH2] n . Polyethylene may be formed by any method known to those skilled in the art.

[0066] As used herein, the term "polyolefin" refers to a polymer having the general formula (CH2CHR) n , where R is an alkyl group. The term "non-polyolefin material" or "non-olefin material" refers to any material that is not a polyolefin. For example, non-polyolefin materials can include polyamides, polyesters, styrene, polyurethanes, and the like.

[0067] As used herein, the term "monopolymer laminate" refers to a laminate that includes a total composition that contains a substantial amount (e.g., more than 80%, 90%, or 95% relative to the total weight of the laminate) of a single polymer type.

[0068] As used herein, the term "linear tear property" refers to a property of a film, sheet, web, etc. that enables it to be easily torn in a substantially linear manner.

[0069] FIG. 1 shows a schematic cross-sectional view of a retortable package film 10 according to an embodiment of the present disclosure.

[0070] The retortable package film 10 includes a laminate 110. The laminate 110 includes an MDOPP film 112 and a BOPP film 114. The laminate 110 can be formed by any suitable laminating method, such as coextrusion, adhesive lamination, etc.

[0071] In the illustrated embodiment of FIG. 1, the laminate 110 further includes an adhesive layer 115 disposed between the MDOPP film 112 and the BOPP film 114. The adhesive layer 115 can bond the BOPP film 114 to the MDOPP film 112. The adhesive layer 115 can include any suitable adhesive, such as a water-soluble adhesive, a radiation-curable or thermosetting adhesive, a hot melt adhesive, and a pressure-sensitive adhesive. Examples of these aforementioned adhesive materials include polyacrylate, acrylic emulsion, polyurethane, polyamide, the reaction product of polyamide and vegetable fatty acid, epoxy, ethyleneamine, polysiloxane, silicone rubber, polyalkylene glycol, polyester, sulfopolyester, etc. It should be noted that the adhesive layer 115 is optional and can be omitted from the laminate 110, for example, when the laminate 110 is formed using a laminating method that does not utilize an adhesive.

[0072] The retortable package film 10 further includes a sealant layer 120 disposed on the laminate 110. The sealant layer 120 includes a blend including a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE. In some embodiments, the blend of the sealant layer 120 includes 4% - 50% by weight of long-chain branched polyethylene and 50% - 90% by weight of the polypropylene terpolymer. In some embodiments, the polypropylene terpolymer has a melting temperature above 130°C.

[0073] The sealing layer 120 has a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A, Condition 230 °C / 2.16 kg. In some embodiments, the melt flow index of the sealing layer 120 is in the range of 5 g / 10 min to 15 g / 10 min according to ASTM D1238 Procedure A, Condition 230 °C / 2.16 kg. In some embodiments, the melt flow index of the sealing layer 120 is in the range of 7 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A, Condition 230 °C / 2.16 kg. In some embodiments, the melt flow index of the sealing layer 120 is in the range of 10 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A, Condition 230 °C / 2.16 kg. In some embodiments, the melt flow index of the sealing layer 120 is in the range of 7 g / 10 min to 15 g / 10 min according to ASTM D1238 Procedure A, Condition 230 °C / 2.16 kg. In some embodiments, the melt flow index of the sealing layer 120 is in the range of 10 g / 10 min to 15 g / 10 min according to ASTM D1238 Procedure A, Condition 230 °C / 2.16 kg.

[0074] This melt flow index of the sealing layer 120 may be suitable for some processes and may be unsuitable for other processes. Table 1 provides the melt flow index ranges for typical polyethylene grades for each process. The melt flow index ranges in Table 1 are obtained from "The Science and Technology of Flexible Packaging: Multilayer Films from Resin and Process to End Use" by Barry A. Morrison.

[0075] Table 1: Melt Flow Index Ranges for Typical Polyethylene Grades for Each Process

Table 1

[0076] As shown in Table 1, the melt flow index of the sealing layer 120 (at 230 °C / 2.16 kg, 5 g / 10 min to 25 g / 10 min) can make the sealing layer 120 suitable for an extrusion coating on the laminate 110. Thus, in some embodiments, the sealing layer 120 is extrusion coated onto the laminate 110. Further, such a melt flow index of the sealing layer 120 can make the sealing layer 120 unsuitable for blown film extrusion and cast film extrusion. A sealing layer designed for and suitable for blown film extrusion typically has a melt flow index of less than 5 g / 10 min and is not suitable for use as the sealing layer 120. A sealing layer designed for and suitable for cast film extrusion typically has a melt flow index of less than 10 g / 10 min, or less than 7 g / 10 min, and is not suitable for use as the sealing layer 120.

[0077] The sealing layer 120 may provide a high sealing strength (e.g., a sealing strength of 5 Newtons / 15 millimeters or more), which can be important for retort applications. Further, the sealing layer 120 may have a low sealing start temperature. For example, the sealing layer 120 may have a sealing start temperature in the range of 100 °C to 140 °C, or in the range of 120 °C to 140 °C. In some embodiments, the sealing layer 120 has a sealing start temperature of less than 140 °C when measured using ASTM F88 Technique A. In some embodiments, the sealing layer 120 is not oriented. The fact that the sealing layer 120 is not oriented may enable the sealing layer 120 to have a low sealing start temperature.

[0078] The BOPP film 114 can provide sufficient rigidity to the retortable package film 10 for package applications. However, the laminate 110 including the MDOPP film 112 and the BOPP film 114 may not have high heat resistance. Thus, the laminate 110 may be prone to defects when exposed to high temperatures during heat sealing.

[0079] The sealing layer 120 can enable the retortable package film 10 to be heat-sealed at a low temperature (e.g., 125 °C) so that the laminate 110 may not melt, warp, or become cloudy. As a result, the retortable package film 10 may be heat-sealed without adversely affecting the laminate 110.

[0080] The retortable package film 10 can exhibit linear tear properties (e.g., along the machine direction). The linear tear properties can be provided by the MDOPP film 112 of the laminate 110. Accordingly, a retortable package formed by the retortable package film 10 can also exhibit linear tear properties to facilitate opening of the retortable package. Advantageously, the retortable package film 10 can exhibit linear tear properties without using a score or any visible feature. Accordingly, any graphic or other appearance feature that can be printed on the retortable package may not be obstructed by such a score or visual feature. This may improve the aesthetic appearance of the retortable package.

[0081] The retortable package film 10 includes a total composition that includes at least 80% polypropylene by weight. As a result, in some embodiments, the total composition includes less than 20% non-polyolefin material by weight. In some embodiments, the total composition includes at least 90% polypropylene by weight. As a result, in some embodiments, the total composition includes less than 10% non-polyolefin material by weight.

[0082] In the illustrated embodiment of FIG. 1, the BOPP film 114 is located on the outer surface 11 of the retortable package film 10. In other words, the BOPP film 114 defines the outer surface 11 of the retortable package film 10. The outer surface 11 may be on the opposite side of the sealing layer 120. The outer surface 11 may form the outer surface of a package formed using the retortable package film 10. Further, in the illustrated embodiment of FIG. 1, the sealing layer 120 is disposed on the MDOPP film 112. The sealing layer 120 may be extrusion coated on the MDOPP film 112.

[0083] FIG. 2 shows a schematic cross-sectional view of a retortable package film 20 according to another embodiment of the present disclosure. The retortable package film 20 is similar to the retortable package film 10 of FIG. 1, and like elements are denoted by like reference characters. However, the retortable package film 20 has a different configuration of the laminate 110 as compared to the retortable package film 10.

[0084] Specifically, in the illustrated embodiment of FIG. 2, the MDOPP film 112 is located on the outer surface 21 of the retortable package film 20. In other words, the MDOPP film 112 defines the outer surface 21 of the retortable package film 20. The outer surface 21 may be on the opposite side of the sealing layer 120. The outer surface 21 may form the outer surface of a package formed using the retortable package film 20. Further, in the illustrated embodiment of FIG. 2, the sealing layer 120 is disposed on the BOPP film 114. The sealing layer 120 may be extrusion coated on the BOPP film 114.

[0085] Figure 3 shows a schematic cross-sectional view of a retortable package film 30 according to another embodiment of the present disclosure. The retortable package film 30 is similar to the retortable package film 10 of FIG. 1, and like elements are denoted by like reference characters. However, the retortable package film 30 has a different configuration of the laminate 110 as compared to the retortable package film 10.

[0086] In some embodiments, the laminate 110 further includes a barrier layer 116 attached to the MDOPP film 112 or the BOPP film 114. It may be noted that the barrier layer 116 is optional and may be omitted from the laminate 110 based on the desired application attributes. In the illustrated embodiment of FIG. 3, the barrier layer 116 is attached to the BOPP film 114.

[0087] The barrier layer 116 may provide desirable barrier properties to the retortable package film 30. For example, the barrier layer 116 may provide gas (e.g., oxygen) barrier properties, moisture barrier properties, and / or odor barrier properties to the retortable package film 30.

[0088] In some embodiments, the barrier layer 116 includes a metal layer or an oxide coating layer deposited on the surface of the MDOPP film 112 or the BOPP film 114. In the illustrated embodiment of FIG. 3, the metal layer or the oxide coating layer is deposited on the surface of the BOPP film 114. The metal layer of the barrier layer 116 may include, for example, a foil (e.g., an aluminum foil). The oxide coating layer of the barrier layer 116 may include, for example, aluminum oxide, silicon oxide, metallized polyethylene terephthalate, and the like.

[0089] In some embodiments, the barrier layer 116 comprises a polymeric barrier material, which may include, but is not limited to, ethylene-vinyl alcohol (EVOH) copolymers, polyvinyl alcohol (PVOH) copolymers, poly(vinyl chloride), polyvinylidene polymers and copolymers, including polyvinylidene chloride, polyamides, including amorphous polyamides, acrylonitrile polymers, including acrylonitrile-methyl acrylate copolymers, polyurethane engineering plastics, poly(methylpentene) resins, ethylene-carbon monoxide copolymers, liquid crystal polymers, polyesters, such as polyethylene terephthalate, polyimides, including polyetherimides and polyacrylimides, and other such polymeric materials known to have relatively low gas permeability. Mixtures and grafts of these aforementioned materials may also be suitable for use as polymeric barrier materials, such as combinations of polyimides with crystalline polymers, such as liquid crystal polymers, polyamides, and polyethylene terephthalate, and combinations of polyamides with styrene.

[0090] 3, the BOPP film 114 is located on the exterior surface 31 of the retortable packaging film 30. In other words, the BOPP film 114 defines the exterior surface 31 of the retortable packaging film 30. The exterior surface 31 may be opposite the sealing layer 120. The exterior surface 31 may form the exterior surface of a package formed using the retortable packaging film 30.

[0091] In the illustrated embodiment of Figure 3, an adhesive layer 115 is disposed between the MDOPP film 112 and the barrier layer 116. Further, in the illustrated embodiment of Figure 3, a sealant layer 120 is disposed on the MDOPP film 112. The sealant layer 120 may be extrusion coated onto the MDOPP film 112.

[0092] Figure 4 shows a schematic cross-sectional view of a retortable package film 40 according to another embodiment of the present disclosure. The retortable package film 40 is similar to the retortable package film 30 of FIG. 3, and like elements are denoted by like reference numerals. However, the retortable package film 40 has a different configuration of the laminate 110 as compared to the retortable package film 30.

[0093] Specifically, in the illustrated embodiment of FIG. 4, the MDOPP film 112 is located on the outer surface 41 of the retortable package film 40. In other words, the MDOPP film 112 defines the outer surface 41 of the retortable package film 40. The outer surface 41 can be on the opposite side of the sealing layer 120. The outer surface 41 can form the outer surface of a package formed using the retortable package film 40. Further, in the illustrated embodiment of FIG. 4, the barrier layer 116 is attached to the MDOPP film 112.

[0094] In the illustrated embodiment of FIG. 4, the adhesive layer 115 is disposed between the BOPP film 114 and the barrier layer 116. Further, in the illustrated embodiment of FIG. 4, the sealing layer 120 is disposed on the BOPP film 114. The sealing layer 120 can be extrusion-coated on the BOPP film 114.

[0095] Figure 5 shows a schematic cross-sectional view of a retortable package film 50 according to another embodiment of the present disclosure. The retortable package film 50 is similar to the retortable package film 40 of FIG. 4, and like elements are denoted by like reference numerals. However, the retortable package film 50 has a different configuration of the laminate 110 as compared to the retortable package film 40.

[0096] Specifically, in the illustrated embodiment of FIG. 5, the barrier layer 116 is disposed on the BOPP film 114, on the opposite side of the sealing layer 120. Further, in the illustrated embodiment of FIG. 5, the adhesive layer 115 is disposed between the MDOPP film 112 and the barrier layer 116.

[0097] In the illustrated embodiment of FIG. 5, the MDOPP film 112 is located on the outer surface 51 of the retortable package film 50. In other words, the MDOPP film 112 defines the outer surface 51 of the retortable package film 50. The outer surface 51 may be on the opposite side of the sealing layer 120. The outer surface 51 may form the outer surface of a package formed using the retortable package film 50.

[0098] FIG. 6 shows a schematic front view of a hermetically sealed packaged food 200 according to an embodiment of the present disclosure.

[0099] The hermetically sealed packaged food 200 may include a retortable package 210 and food (not shown) packaged inside the retortable package 210. In the illustrated embodiment of FIG. 6, the retortable package 210 is a stand-up pouch. However, it may be noted that the retortable package 210 may be any suitable type of flexible package.

[0100] In the illustrated embodiment of FIG. 6, the hermetically sealed packaged food 200 includes the retortable package film 10 of FIG. 1. Specifically, the retortable package 210 may include the retortable package film 10. In other words, the retortable package 210 may be made from the retortable package film 10. In some other embodiments, the hermetically sealed packaged food 200 may include the retortable package film 20 of FIG. 2, the retortable package film 30 of FIG. 3, the retortable package film 30 of FIG. 3, the retortable package film 40 of FIG. 4, or the retortable package film 50 of FIG. 5.

[0101] Referring to FIGS. 1 and 6, a retortable package film 10 can be hermetically heat-sealed to form a retortable package 210. As a result, the retortable package 210 can be suitable for undergoing a retort process. Advantageously, the retortable package 210 can exhibit a linear tear property along an opening direction 220. The opening direction 220 can correspond to the machine direction of the MDOPP film 112 of the retortable package film 10. As a result, the retortable package 210 can be easily torn along the opening direction 220 to access the food packaged therein. Advantageously, instruments such as a pair of scissors may not be required to open the retortable package 210.

[0102] FIG. 7 shows a flowchart illustrating various steps of a method 300 for manufacturing a retortable package film according to an embodiment of the present disclosure. For example, the method 300 can be used to manufacture the retortable package film 10 of FIG. 1, the retortable package film 20 of FIG. 2, the retortable package film 30 of FIG. 3, the retortable package film 40 of FIG. 4, or the retortable package film 50 of FIG. 5.

[0103] In step 310, the method 300 includes laminating a BOPP film to an MDOPP film to form a pre-laminate. Referring to FIGS. 1 and 7, for example, the method 300 can include laminating the MDOPP film 112 to the BOPP film 114 to form a laminate 110. The pre-laminate can have any suitable configuration, such as the configuration of the laminate 110 described above with reference to FIGS. 1-5.

[0104] In step 320, method 300 further includes extrusion coating a seal layer onto the prelaminate. The seal layer includes a blend comprising a polypropylene terpolymer and a long chain branched polyethylene selected from the group consisting of LDPE and MDPE. The seal layer has a melt flow index between 5 g / 10 min and 25 g / 10 min, according to ASTM D1238 Procedure A, Condition 230°C / 2.16 kg. Referring to FIGS. 1 and 7, for example, method 300 may include an extrusion coating seal layer 120 on laminate 110. The seal layer 120 may include a blend comprising a polypropylene terpolymer and a long chain branched polyethylene selected from the group consisting of LDPE and MDPE. Further, the seal layer 120 may have a melt flow index of between 5 g / 10 min and 25 g / 10 min, according to ASTM D1238 Procedure A, Condition 230°C / 2.16 kg.

[0105] Method 300 may enable the production of a retortable package film in a simple and economical manner.

[0106] FIG. 8 shows a flowchart illustrating various steps of a method 400 for manufacturing a retortable package film, according to an embodiment of the present disclosure. For example, method 400 may be used to manufacture the retortable package film 30 of FIG. 3.

[0107] In step 410, method 400 includes extruding and machine direction orienting a film to produce an MDOPP film. Referring to FIGS. 3 and 8, for example, method 400 may include extruding and machine direction orienting a film to produce an MDOPP film 112.

[0108] In step 420, method 400 further includes extrusion coating a seal layer onto the MDOPP film. Referring to FIGS. 3 and 8, for example, method 400 may include an extrusion coating seal layer 120 on MDOPP film 112.

[0109] In step 430, method 400 further includes applying a barrier coating to the BOPP film. Referring to FIGS. 3 and 8, for example, method 400 may include applying a barrier layer 116 to the BOPP film 114.

[0110] In step 440, method 400 further includes adhering and laminating an MDOPP film and a BOPP film. Referring to FIGS. 3 and 8, for example, method 400 may include adhering and laminating an MDOPP film 112 and a BOPP film 114.

[0111] The seal layer includes a blend comprising a polypropylene terpolymer and a long chain branched polyethylene selected from the group consisting of LDPE and MDPE. The seal layer has a melt flow index between 5 g / 10 min and 25 g / 10 min according to ASTM D1238 Procedure A Condition 230° C. / 2.16 kg. Referring to FIGS. 3 and 8, for example, the seal layer 120 may include a blend comprising a polypropylene terpolymer and a long chain branched polyethylene selected from the group consisting of LDPE and MDPE. Further, the seal layer 120 may have a melt flow index between 5 g / 10 min and 25 g / 10 min according to ASTM D1238 Procedure A Condition 230° C. / 2.16 kg.

[0112] Method 400 may enable a retortable package film to be manufactured in a simple and economical manner.

[0113] Examples In the following examples, the following test protocols were used. · Melt Flow Index - Unit: g / 10 min, tested at 230° C. using ASTM D1238 2.16 kg unless otherwise specified. The melt flow index (MFI) may be interchangeably referred to as the melt flow rate (MFR). · Seal Strength ASTM F88 - Seal using two side heat seal bars, 0.5 seconds, 400 N / cm 2Pressure, sealing to itself, peel in the mechanical direction, peel at 300 mm / min with a 15 mm wide tensile unit. · The sealing start temperature is the sealing temperature at which a sealing strength of approximately 5 N / 15 mm is achieved. · Tear strength, trouser tear test, mechanical direction, ASTM D1938. This test can further show the straight-line tear characteristics of the film.

[0114] Comparative Example To demonstrate the detrimental effect that the orientation of the sealing layer can have on the sealing start temperature, two sample films were made. The three-layer film was made by cast coextrusion, and the sealing layer has a mixture of 67% polypropylene terpolymer (Tm = 131 °C, MFR = 6.0 g / 10 min), 25% thermoplastic polyolefin copolymer (Tm = 142 °C, MFR = 0.6 g / 10 min), 5% homopolymer polypropylene, and 3% antiblock masterbatch. This film was laminated to two BOPP films to create a first three-layer laminate structure. When this film was heat-sealed, it was found that the laminate had a sealing start temperature of approximately 121 °C and a sealing strength of 16.9 N / 15 mm when sealed at 130 °C. These sealing characteristics are highly desirable for retort packaging. The film had a tear strength (trouser tear) of approximately 1.6 N, which is acceptable. However, this laminate structure has very poor straight-line tear performance.

[0115] The second laminate was produced by first orienting the above three-layer cast coextruded film in the machine direction (3:1 draw), and then laminating this MDO film to two BOPP films to create a second three-layer laminate structure. When this film was heat sealed, the laminate was found to have a seal start temperature of about 134 °C and a seal strength of less than 1 N / 15 mm at 130 °C. This indicates that while the orientation of the seal film can assist in tear property performance, the detrimental effect on the heat seal start temperature is unacceptable. The draw ratio of this film was 3:1. By increasing the draw ratio (i.e., 5:1), it is possible to improve the tear performance of this film. However, this change will have a further detrimental effect on the seal performance due to the orientation of the seal layer.

[0116] Examples of the present invention [BOPP / adhesive / MDOPP / extrusion coated sealant] structure was used to fabricate a film laminate. The MDO film contained randomly oriented PP drawn at a ratio of 5:1 and had a final thickness of 30 microns. The sealant was applied by extrusion coating at a weight of 24 g / m 2 The sealant consisted of 65% (by weight) polypropylene terpolymer (Tm = 131 °C, MFR = 6.0 g / 10 min), 20% LDPE with long chain branches (MFR = 3.8 g / 10 min at 190 °C, Tm = 108 °C), 10% homopolymer polypropylene (MFR = 25 g / 10 min ISO 1133), and 5% random copolymer polypropylene (density = 0.88 g / cm 3, a mixture with an MFR of 6 g / 10 min at 230 °C / 2.16 kg. The measured MFR of the sealant blend was 7.7 g / 10 min. When this film was heat-sealed, a seal start temperature of approximately 125 °C was found. This laminate showed a straight tear and a trouser tear value of 2.05 N. This film had a total composition containing 3.5% polyethylene, 94.2% polypropylene, 97.7% polyolefin, and 2.3% non-olefin material (adhesive). Note that when the MDOPP film is further optimized for sealing (such as the MDOPP film used in the above comparative example), it is possible to achieve a lower trouser tear value.

[0117] A film laminate was produced to demonstrate the effectiveness of introducing an MDOPP film into the laminate and applying a sealant layer using an extrusion coating. The final laminate structure was BOPP / adhesive / MDOPP / sealant. The MDOPP film was a three-layer co-extruded film stretched 5X in the machine direction, with a final thickness of 30 microns. The MDOPP film had a core layer containing 100% homopolymer polypropylene and a surface layer of 80% heterophase polypropylene block copolymer and 20% random copolymer polypropylene (density = 0.88 g / cm 3 , MFR = 6 g / 10 min at 230 °C / 2.16 kg). The sealant was 24 g / m 2Applied by extrusion coating at a weight of. The sealant was a mixture of approximately 50% polypropylene terpolymer (Tm = 131°C, MFR = 9 g / 10 min), approximately 25% random copolymer polypropylene, approximately 20.5% polypropylene, and approximately 4.5% long-chain branched LDPE. The melt flow rate of the sealant blend was calculated to be approximately 12.2 g / 10 min (at 230°C / 2.16 kg). When this film was heat-sealed, the laminate was found to have a seal start temperature of approximately 123°C and a seal strength of 13.7 N / 15 mm at 130°C. The laminate also had advantageous machine direction tear properties, a clean straight tear, and had 1.2 N in a trouser tear test. This film had a total composition containing 3.2% polyethylene, 94.5% polypropylene, 97.7% polyolefin, and 2.3% non-olefin material (adhesive). This indicates that optimized MDOPP and an extruded coated sealant deliver the desired combination of suitable sealing for retort and good machine direction tear.

[0118] Each and every document cited in this application, including cross-references, is hereby incorporated by reference in its entirety into this application, unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any embodiment disclosed in this application, or that it alone, or in any combination with any other reference(s), teaching, suggestion, or disclosure, discloses any such embodiment. Further, the meaning or definition assigned to a term in this application shall be controlling over the meaning or definition of the same term in a document incorporated by reference, to the extent that the meaning or definition of the term in this application conflicts with the meaning or definition of the same term in the incorporated document.

[0119] Unless otherwise indicated, all numbers expressing sizes, amounts, ranges, limits, and all physical and other properties used in this application are to be understood as being preceded by the term "about" in all instances. Accordingly, unless explicitly indicated to the contrary, the numerical parameters set forth in this application are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art without undue experimentation from the teachings disclosed herein.

[0120] As used in this application, the singular forms "a", "an", and "the" include embodiments having a plurality of references unless the context clearly dictates otherwise. As used in this application, the term "or" is generally used in its sense including "and / or" unless the context clearly dictates otherwise.

[0121] As used in this application, spatially relative terms, including but not limited to "lower", "upper", "beneath", "below", "above", "bottom", and "top", are used for ease of description to describe the spatial relationship of one element to another. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if an object depicted in the drawings is turned over or inverted, an element described as below or beneath other elements will then be above those other elements.

[0122] The drawings show some but not all embodiments. The elements shown in the drawings are illustrative and not necessarily to scale, and like (or similar) reference numerals designate like (or similar) features throughout the drawings.

[0123] The disclosed descriptions, examples, embodiments, and drawings are merely illustrative and should not be construed as limiting. The present invention includes the disclosed descriptions, examples, embodiments, and drawings, but is not limited to such descriptions, examples, embodiments, or drawings. As briefly described above, the reader should assume that the features of one disclosed embodiment can be applied to all other disclosed embodiments as well, unless explicitly indicated to the contrary. Modifications and other embodiments will be apparent to those skilled in the art in the field of packaging technology, and all such modifications and other embodiments are intended to be within the scope of and considered in the present invention.

[0124] Embodiment of a retortable packaging film

[0125] A. A retortable packaging film, which is a laminate, comprising a BOPP film and an MDOPP film, and a sealing layer disposed on the laminate and comprising a blend comprising a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE, the sealing layer having a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg, and a total composition comprising at least 80% polypropylene by weight.

[0126] B. Any other retortable packaging film embodiment, wherein the blend of the sealing layer comprises the long-chain branched polyethylene between 4% and 50% by weight and the polypropylene terpolymer between 50% and 90% by weight.

[0127] C. Any other retortable packaging film embodiment, wherein the polypropylene terpolymer has a melting temperature above 130°C.

[0128] D. A retortable package film according to an embodiment of any other retortable package film having a sealing start temperature of less than 140 °C when measured using ASTM F88 Technique A.

[0129] E. A retortable package film according to an embodiment of any other retortable package film, wherein the melt flow index of the sealing layer is in the range of 5 g / 10 min to 15 g / 10 min according to ASTM D1238 Procedure A Condition 230 °C / 2.16 kg.

[0130] F. A retortable package film according to an embodiment of any other retortable package film, wherein the sealing layer is not oriented.

[0131] G. A retortable package film according to an embodiment of any other retortable package film, wherein the sealing layer is extrusion coated onto the laminate.

[0132] H. A retortable package film according to an embodiment of any other retortable package film, wherein the laminate further comprises a barrier layer attached to the BOPP film or the MDOPP film.

[0133] I. The retortable package film according to embodiment H, wherein the barrier layer comprises a metal layer or an oxide coating layer deposited on the surface of the BOPP film or the MDOPP film.

[0134] J. The retortable package film according to embodiment H, wherein the barrier layer comprises a polymeric barrier material.

[0135] K. A retortable package film according to an embodiment of any other retortable package film, wherein the total composition comprises at least 90% by weight of polypropylene.

[0136] L. A retortable package film according to any other embodiment of a retortable package film, wherein the total composition comprises less than 20% by weight of a non-polyolefin material.

[0137] M. A retortable package film according to any other embodiment of a retortable package film, wherein the total composition comprises less than 10% by weight of a non-polyolefin material.

[0138] N. The retortable package film according to any one of embodiments A to M, wherein the MDOPP film is located on the outer surface of the retortable package film.

[0139] O. The retortable package film according to any one of embodiments A to M, wherein the BOPP film is located on the outer surface of the retortable package film.

[0140] Embodiments of hermetically sealed packaged food

[0141] P. Hermetically sealed packaged food comprising a retortable package film according to any one of embodiments A to O.

[0142] Embodiments of the method

[0143] Q. A method for manufacturing a retortable package film, the method comprising: laminating a BOPP film to an MDOPP film to form a prelaminate; extrusion coating a sealing layer onto the prelaminate, wherein the sealing layer comprises a blend comprising a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE, and the sealing layer has a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg.

[0144] R. A method for manufacturing a retortable package film, the method comprising: extruding and orienting the film in the machine direction to produce an MDOPP film; extrusion coating a sealing layer onto the MDOPP film; applying a barrier coating to a BOPP film; adhering and laminating the MDOPP film and the BOPP film, wherein the sealing layer comprises a blend comprising a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE, and the sealing layer has a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg.

Claims

1. A retortable package film, which is a laminate, comprising a BOPP film and an MDOPP film, and a sealing layer disposed on the laminate and comprising a blend containing a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE, the sealing layer having a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg, and a total composition containing at least 80% polypropylene by weight. A retortable package film.

2. The retortable package film according to claim 1, wherein the blend of the sealing layer contains the long-chain branched polyethylene in the range of 4% to 50% by weight and the polypropylene terpolymer in the range of 50% to 90% by weight.

3. The retortable package film according to claim 1, wherein the polypropylene terpolymer has a melting temperature above 130°C.

4. The retortable package film according to claim 1, wherein the sealing layer has a sealing start temperature below 140°C when measured using ASTM F88 Technique A.

5. The retortable package film according to claim 1, wherein the melt flow index of the sealing layer is in the range of 5 g / 10 min to 15 g / 10 min according to ASTM D1238 Procedure A Condition 230°C / 2.16 kg.

6. The retortable package film according to claim 1, wherein the sealing layer is not oriented.

7. The retortable package film according to claim 1, wherein the sealing layer is extrusion-coated on the laminate.

8. The retortable package film according to claim 1, wherein the laminate further comprises a barrier layer attached to the BOPP film or the MDOPP film.

9. The retortable package film according to claim 8, wherein the barrier layer comprises a metal layer or an oxide coating layer deposited on the surface of the BOPP film or the MDOPP film.

10. The retortable package film according to claim 8, wherein the barrier layer contains a polymer barrier material.

11. The retortable package film according to claim 1, wherein the total composition comprises at least 90% by weight of polypropylene.

12. The retortable package film according to claim 1, wherein the total composition comprises less than 20% by weight of non-polyolefin material.

13. The retortable package film according to claim 1, wherein the total composition comprises less than 10% by weight of non-polyolefin material.

14. The retortable package film according to claim 1, wherein the MDOPP film is located on the outer surface of the retortable package film.

15. The retortable package film according to claim 1, wherein the BOPP film is located on the outer surface of the retortable package film.

16. An airtight sealed packaged food containing the retortable package film according to claim 1.

17. A method for manufacturing a retortable package film, comprising: laminating a BOPP film to an MDOPP film to form a pre-laminate; comprising the step of extrusion coating a sealant layer onto the prelaminate; wherein the sealant layer comprises a blend comprising a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE, and the sealant layer has a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A condition 230 °C / 2.16 kg.

18. A method of manufacturing a retortable package film, comprising: extruding and orienting a film in the machine direction to produce an MDOPP film; extrusion coating a sealant layer onto the MDOPP film; applying a barrier coating to a BOPP film; and bonding and laminating the MDOPP film and the BOPP film, wherein the sealant layer comprises a blend comprising a polypropylene terpolymer and a long-chain branched polyethylene selected from the group consisting of LDPE and MDPE, and the sealant layer has a melt flow index in the range of 5 g / 10 min to 25 g / 10 min according to ASTM D1238 Procedure A condition 230 °C / 2.16 kg.

Images