Film having a boiling impact recovery

Abstract

A multilayer barrier film for food packaging, the multilayer barrier film comprising: an outer layer comprising a first polymeric material having a water vapor transmission rate (MVTR) of greater than or equal to 10 g. mil / 100 in 2 / day; a first inner layer adjacent to the outer layer, the first inner layer comprising a first cookable grade ethylene vinyl alcohol (EVOH) copolymer; a second inner layer adjacent to the first inner layer, the second inner layer comprising a second polymeric material having a water vapor transmission rate (MVTR) of greater than or equal to 10 g. mil / 100 in 2 / day; a third inner layer adjacent to the second inner layer, the third inner layer comprising a second cookable grade EVOH copolymer; and a seal layer adjacent to the third inner layer; wherein the first polymeric material is not a cookable grade EVOH copolymer. Excellent recovery of oxygen barrier over time is achieved by these films and cookable containers made therefrom.

Description

Technical Field

[0001] This disclosure relates to high-barrier, heat-sealable films for retort applications. Specifically, the disclosed films can be used in thermoformed retort packaging. Background Technology

[0002] Cooking is used for heat-processed foods and sterilized primary packaging components. Food packaged in a retortable container (such as a bag) is transferred to an autoclave, where it is subjected to cooking conditions, including temperatures typically exceeding the boiling point of water and increased pressure, for a sustained period of time. Therefore, retortable containers are designed to withstand cooking conditions.

[0003] Ethylene-vinyl alcohol (“EVOH”) copolymers are well known for their oxygen barrier properties. The effectiveness of EVOH in blocking oxygen is highly dependent on relative humidity. That is, exposure to moisture reduces the ability of EVOH to provide gas barriers, which can be measured as oxygen permeability (OTR). As an oxygen barrier, a lower OTR is desirable. In co-extruded films, in addition to its oxygen barrier properties, EVOH also exhibits excellent durability, good thermoforming properties, and a good appearance, which are desirable characteristics in retortible containers.

[0004] Some membranes used for cooking utilize a high moisture barrier on the outer layer of the membrane containing EVOH to protect it. Even so, due to the container's exposure to humid and hot conditions, an increase in OTR is expected after the cookable container is exposed to cooking conditions. This temporary increase in OTR is known as cooking shock. The loss of oxygen barrier / increase in OTR is reversible for most cases, and the oxygen barrier recovers as the material dries. Some existing EVOH-containing cookable containers can experience long cooking shock recovery times because the oxygen barrier does not fully re-establish itself only after a considerable period of time (days / weeks).

[0005] Although other barrier materials, such as SiOx or LCP (liquid crystal polymer), do not exhibit cooking impact, these materials are either not suitable for deep drawing (e.g. for plates / containers) or are not cost-effective.

[0006] Some other retort packaging products combine materials such as oriented polyethylene terephthalate (OPET), bidirectional oriented nylon (BON), AlOx, foil, etc., with polypropylene sealants. These products are manufactured by laminating multiple layers to form, for example, 3-layer and 4-layer structures. Furthermore, these laminates cannot be deeply drawn.

[0007] There is a continued need for EVOH-containing films for packaging, which offer good retort shock recovery, long shelf life, high oxygen barrier properties, and optical transparency. Summary of the Invention

[0008] The membranes and retortable containers disclosed herein enable excellent recovery of oxygen barrier properties after thermal processing, thereby improving the overall shelf-life expectation of any given packaged product.

[0009] The first aspect is a multilayer barrier film for food packaging, the multilayer barrier film comprising: a first outer layer, the first outer layer comprising a layer having a density greater than or equal to 10 g. mils / 100 inches. 2 A first polymer material with a water vapor transmission rate (MVTR) of / day; a first inner layer adjacent to the first outer layer, the first inner layer comprising a first retortable grade ethylene vinyl alcohol (EVOH) copolymer; and a second inner layer adjacent to the first inner layer, the second inner layer comprising a material having a water vapor transmission rate (MVTR) of greater than or equal to 10 g·mil / 100 inches. 2 A second polymer material with a water vapor transmission rate (MVTR) of / day; a third inner layer adjacent to the second inner layer, the third inner layer comprising a second retortable grade ethylene vinyl alcohol (EVOH) copolymer; and a second outer layer adjacent to the third inner layer, the second outer layer comprising a sealing layer; wherein the first polymer material is not a retortable grade ethylene vinyl alcohol (EVOH) copolymer.

[0010] Another aspect is a multilayer barrier film for food packaging, comprising: a first outer layer comprising a first polyamide; a first inner layer adjacent to the first outer layer, the first inner layer comprising a first retortable grade ethylene vinyl alcohol (EVOH) copolymer; a second inner layer adjacent to and in direct contact with the first inner layer, the second inner layer comprising a second polyamide; a third inner layer adjacent to and in direct contact with the second inner layer, the third inner layer comprising a second retortable grade ethylene vinyl alcohol (EVOH) copolymer; a fourth inner layer adjacent to and in direct contact with the third inner layer, the fourth inner layer comprising a polymer material comprising polyamide or polypropylene; and a second outer layer adjacent to the fourth inner layer; wherein the multilayer barrier film is thermoformable and has a thickness ranging from about 38.1 micrometers (1.5 mils) to about 1,143 micrometers (45 mils).

[0011] On the other hand, retortable containers include any of the multilayer barrier films disclosed herein. The retortable container may include a bottom sheet and a top sheet, the bottom sheet comprising a thermoformed film and the top sheet comprising a non-thermoformed film; wherein at least one of the bottom sheet and the top sheet includes the multilayer barrier film. The retortable container may be in the form of a bag, the bag including one or more sidewalls formed by the multilayer barrier film. The retortable container may include a bag including sidewalls and gussets; wherein at least one of the sidewalls and the gussets includes the multilayer barrier film.

[0012] In one aspect, a method for preparing a multilayer barrier film for food packaging includes: extruding a first polymer resin of a first polymer material through a die to form a first outer layer, the first outer layer comprising a layer having a density greater than or equal to 10 g·mil / 100 inch. 2 A first polymer material with a water vapor transmission rate (MVTR) of / day; a second polymer resin of a first retortable grade ethylene vinyl alcohol (EVOH) copolymer is extruded through a die to form a first inner layer; a third polymer resin of the second polymer material is extruded through a die to form a second inner layer, the second inner layer comprising a water vapor transmission rate (MVTR) of greater than or equal to 10 g·mil / 100 inches. 2 A second polymer material with a water vapor transmission rate (MVTR) of / day; a fourth polymer resin of a second retortable grade ethylene vinyl alcohol (EVOH) copolymer is extruded through a die to form a third inner layer; and a second outer layer is formed from one or more extrudable polymer resins.

[0013] The method may further include extruding a fifth polymer resin through a die to form a fourth inner layer located between the third inner layer and the second outer layer. The second outer layer may include co-extruded sublayers, such that a first sublayer of the second outer layer comprises a polyolefin, and a second sublayer of the second outer layer is an adhesive layer, such that the second sublayer is located between the first sublayer and the third or fourth inner layer.

[0014] Another aspect is a method of packaging food in a retortable container, the method comprising: obtaining any retortable container disclosed herein; packaging food in the retortable container; and exposing the retortable container to cooking conditions. Attached Figure Description

[0015] This disclosure can be more fully understood by taking into consideration the following detailed description of various embodiments of the present disclosure in conjunction with the accompanying drawings, wherein:

[0016] Figure 1 This is a cross-sectional view of an exemplary multilayer barrier film;

[0017] Figure 2 This is another exemplary cross-sectional view of a multilayer barrier film;

[0018] Figure 3 This is an exploded perspective view of an exemplary cookable container;

[0019] Figure 4 This is a plan view of an exemplary cookable container;

[0020] Figure 5 This is a plan view of an exemplary cookable container;

[0021] Figure 6 This is a schematic side view of an exemplary cookable container; and

[0022] Figure 7 This is a plan view of an exemplary cookable container;

[0023] Figure 8 This is a graph of the oxygen permeability (OTR) of an exemplary membrane versus time.

[0024] Figure 9 This is a graph showing the oxygen permeability (OTR) of the comparison membrane relative to time.

[0025] Figure 10 This is a graph of the oxygen permeability (OTR) of an exemplary membrane versus time; and

[0026] Figure 11 This is a graph showing the oxygen permeability (OTR) of the comparison membrane relative to time.

[0027] These figures are not necessarily drawn to scale. The same reference numerals used in the figures refer to the same parts. However, it should be understood that the use of reference numerals to indicate parts in a given figure is not intended to limit the part to being labeled with the same reference numerals in another figure. Detailed Implementation

[0028] Membranes and cookable vessels are provided that offer excellent cook shock recovery. Rapid recovery of oxygen permeability (OTR) after exposure to cook conditions can be achieved using membranes comprising a water-permeable outer layer and two inner layers containing ethylene-vinyl alcohol (“EVOH”) separated by another water-permeable layer. The water-permeable layers may include layers with a permeability greater than or equal to 10 g·mil / 100 inches. 2 Polymer materials with a water vapor transmission rate (MVTR) of 20 g·mil / 100 inch / day. Highly permeable layers can include those with a MVTR greater than or equal to 20 g·mil / 100 inch. 2 Polymer materials with a water vapor transmission rate (MVTR) of 10 g·mil / 100 inch / day. When two or more EVOH-based layers in a multilayer membrane are located near the outer water-permeable layer, this can be achieved by using polymer materials with a MVTR greater than or equal to 10 g·mil / 100 inch. 2 A polymeric membrane with a water vapor transmission rate (MVTR) of / day, placed as an outer layer between EVOH-based layers, can improve cooking shock recovery.

[0029] In one or more embodiments, the water-permeable or highly water-permeable layer comprises a polyamide that is also hygroscopic. Accordingly, these polyamide layers are expected to absorb water during cooking. However, despite the presence of a water-permeable material between the EVOH-based layers, the membranes of this invention unexpectedly exhibit excellent cook recovery over time. Compared to membranes having a polyamide outer layer rather than a polyolefin (such as polypropylene) between the EVOH-based layers and a polyamide layer between the EVOH layer and the sealing layer, or without such a polyamide inner layer, the membranes of this invention exhibit lower oxygen permeation over time (e.g., over the assumed shelf life of the product).

[0030] The multilayer films described herein are advantageous for thermoformed packaging. For example, the films described herein are suitable for semi-rigid or flexible thermoformed webs combined with a lid, which may or may not be a multilayer film according to this invention. The multilayer films described herein provide a durable oxygen barrier when handled and processed in various ways. The benefits of the multilayer films described herein compared to other retort structures containing, for example, AlOx or SiOx include the ability to be thermoformed or otherwise stretched and used without compromising the oxygen barrier properties.

[0031] The following definitions are used in this document:

[0032] As used herein, a “layer” refers to a structural unit of a membrane, which is a structure of a single polymer type or a blend of polymers, or may contain additives. As used herein, layers are “adjacent” if they are close to each other, with or without an intermediate layer, such as a bonding layer. As used herein, layers are “in direct contact” if they share a common interface.

[0033] The term "outer layer" as used in this article refers to the outermost part of the membrane among all its layers.

[0034] As used herein, "inner layer" refers to a layer not exposed to handling and the environment. Inner layers can provide functionality as needed for a specific application. Inner layers typically allow for the thermoforming of the entire film. Furthermore, inner layers can provide barrier protection and / or structural strength. An exemplary inner layer is a barrier layer that provides freshness protection for packaged food and / or provides a barrier against moisture and / or oxygen. The barrier layer can also protect the EVOH layer from migration from the packaged contents (e.g., oils, etc.). An exemplary inner layer can also be a structural layer that provides one or more of the following: general durability, puncture strength, curl resistance, and flexural crack resistance.

[0035] A "sealing layer" is a layer that can be heat-sealed to itself or another sealing layer to form an airtight seal. That is, the sealing layer contains a thermoplastic polymer or polymer mixture that softens when exposed to heat or other energy sources and returns to its initial state when cooled to room temperature.

[0036] As used herein, the term "polymer" refers to the product of a polymerization reaction and includes homopolymers, copolymers, terpolymers, etc. Generally speaking, a membrane layer may consist essentially of a single polymer or may have additional polymers present together, i.e., blended with it.

[0037] As used herein, the term "polymer" refers to a polymer formed by the polymerization of at least two different monomers. As used herein, a copolymer identified by multiple monomers, such as "propylene / ethylene copolymer," refers to a copolymer in which any one monomer can be copolymerized at a higher weight or molar percentage than one or more other monomers. However, the monomers listed first are preferably polymerized at a higher weight percentage than the monomers listed second.

[0038] As used herein, “EVOH” refers to ethylene-vinyl alcohol copolymer. EVOH is also known as saponified or hydrolyzed ethylene-vinyl acetate copolymer and refers to ethylene alcohol copolymer having ethylene comonomers. EVOH is prepared by hydrolysis (or saponification) of ethylene-vinyl acetate copolymer. The degree of hydrolysis is preferably from about 50 to 100 mol%, more preferably from about 85 to 100 mol%, and most preferably at least 97%. It is well known that in order to be an effective oxygen barrier layer, hydrolysis-saponification must be almost complete, i.e., to a degree of at least 97%. EVOH is commercially available in resin forms with various percentages of ethylene and there is a direct relationship between ethylene content and melting point. Higher ethylene content is expected to promote processability and orientation; however, permeability, especially to oxygen, may become unsuitably high for certain packaging applications that are sensitive to microbial growth in the presence of oxygen. Conversely, lower ethylene content may provide lower gas permeability, but processability and orientation may be more difficult. Preferably, the EVOH contains from about 27-48 mol% ethylene or even 27-38 mol% ethylene.

[0039] The reference to “retorable grade” EVOH copolymers refers to EVOH copolymers in film form that do not melt or otherwise degrade under “retorable conditions”, which are exposure to high-temperature steam or superheated water at approximately 120°C ± 5°C at 30 psi atmosphere for approximately 30 to 60 minutes.

[0040] The reference to "retorable" polyamide refers to a film-form polyamide that does not melt or otherwise degrade under "retorting conditions," which are exposure to high-temperature steam or superheated water at approximately 120°C ± 5°C at 30 psi for approximately 30 to 60 minutes. In one or more embodiments, a layer comprising retortable polyamide did not exhibit whitening after exposure to a spray of superheated water at approximately 120°C ± 5°C at 30 psi for 60 minutes.

[0041] As used herein, the term "polyamide" refers to a homopolymer or copolymer having amide bonds between monomer units, which can be formed by any method known to those skilled in the art. Useful polyamide homopolymers include nylon 6 (polycaprolactam), etc. Other useful polyamide homopolymers include nylon 6,6 (polyhexamethylene adipamide). Useful polyamide copolymers include nylon 6,6 / 6 copolymer (polyhexamethylene adipamide / caprolactam copolymer), nylon 6 / 6,6 copolymer (polycaprolactam / hexamethylene adipamide copolymer), and other nylons not specifically described herein. Other useful polyamides can be block copolymers of polyamides, such as those produced by Arkema Technical Polymers under the trade name... MV 3000 is a polyether / polyamide block copolymer for sale. Other suitable copolymers include those from BASF under the trade name... Nylon sold under the brand name C33LN 01 (PA6 / 66 grade) and nylon sold by Ube Industries, Ltd. (UBE) under the brand name 5033FD825 (PA6 / 66).

[0042] The reference to "water vapor transmission rate" (MVTR) refers to the ability of a polymer layer to transmit moisture, as measured according to ASTM-1249-13, entitled "Standard Test Method for Water Vapor Transmission Through Plastic Films and Sheets Using Modulated Infrared Sensors." The conditions used for measurement include atmospheric pressure, 38°C, and 90% relative humidity.

[0043] The reference to "Oxygen Transmission Rate" (OTR) refers to the ability of a polymer membrane to transmit oxygen, as measured according to ASTM-1927-14, entitled "Standard Test Method for Determining the Oxygen Transmission Rate, Permeability and Infiltration Through Barrier Materials under Controlled Relative Humidity Using a Coulomb Detector." The conditions used for measurement include: 1 atm pressure, 23°C, and 50% relative humidity on the outside and 90% relative humidity on the inside (sealant side).

[0044] The terms "adhesive layer," "adhesive layer," or "adhesive coating" refer to a material, partially or entirely, applied to one or more layers to promote adhesion between those layers and another surface. Preferably, the adhesive layer or coating is positioned between two layers of a multilayer film to hold the two layers in their opposite positions and prevent undesirable delamination. Unless otherwise specified, the adhesive layer or coating may have any suitable composition to provide a desired level of adhesion to one or more surfaces in contact with the adhesive layer material. Optionally, the adhesive layer or coating positioned between a first and a second layer in a multilayer film may contain components of both the first and second layers to promote simultaneous adhesion of the adhesive layer to both the first and second layers on opposite sides of the adhesive layer.

[0045] "Sidewall" refers to a discrete component of a polymer film or multilayer laminate that is sealed, for example by welding or adhesive, to itself or another sidewall to form a bag or pouch.

[0046] membrane

[0047] Multilayer membranes and containers having such membranes preferably possess sealing strength, stability, heat resistance, and oxygen and water vapor permeability characteristics that allow them to withstand boiling conditions without loss of desired functional properties. The membranes disclosed herein can also be used for pasteurization purposes.

[0048] For example, after exposure to boiling conditions, according to ASTM-F88 with a clamp speed of 12 in / min (30.48 cm / min), the seal strength typically ranges from about 5 N / 15 mm (863 g / in) to about 100 N / 15 mm (17,267 g / in), and is typically from about 6 N / 15 mm (1,036 g / in) to about 50 N / 15 mm (8,634 g / in). Advantageously, seal strength retention is also observed based on a seal strength loss that is typically less than about 35%, typically less than about 20%, and often less than about 10% when subjected to boiling conditions.

[0049] Furthermore, the multilayer membranes described herein also exhibit acceptable heat resistance in resisting delamination or other visible defects. Preferably, no delamination of the membrane structure was observed after the membrane was subjected to 100°C (212°F) for 30 minutes, or even 60 minutes.

[0050] Other representative membrane properties include less than 0.4 cc / m² after 1 hour of exposure to a 250°F water spray and a 145-hour recovery period at 30 psi. 2The membrane can exhibit a 90% or even 95% recovery rate after approximately 46.5 hours following exposure to cooking conditions at 250°F ± 5°F for 60 minutes and an overpressure of 30 psi. It should be understood that the time following exposure to cooking conditions refers to the steady-state condition after the conditioning time specified in the ASTM OTR test method, typically 4.25 to 5 hours, including approximately 4.5 hours. Data acquisition typically begins after the test equipment and the loaded sample have completed their conditioning cycle and sufficient time has elapsed to measure the first data point.

[0051] Representative multilayer films also comply with the regulations set forth in 21C.FR §177.1390 ​​(which are hereby incorporated by reference).

[0052] The thickness of multilayer membranes can have a minimum of about 38.1 micrometers (1.5 mils), about 50.8 micrometers (2.0 mils), about 76.2 micrometers (3.0 mils), about 101.6 micrometers (4 mils), or about 127 micrometers (5 mils). The thickness of multilayer barrier membranes can have a maximum of about 254 micrometers (10 mils), about 381 micrometers (15 mils), about 508 micrometers (20 mils), about 762 micrometers (30 mils), or about 1,143 micrometers (45 mils). For example, the total thickness of representative multilayer membranes as described herein that can be used to form retortible containers is typically in the range of about 38.1 micrometers (1.5 mils) to about 1,143 micrometers (45 mils), or in the range of about 101.6 micrometers (4 mils) to about 760 micrometers (29.9 mils).

[0053] Material

[0054] The multilayer membrane includes a first outer layer that is positioned furthest from the contents of the container after container formation. This first outer layer is water-permeable or highly water-permeable. In one or more embodiments, the first outer layer comprises a first polymer material having a density greater than or equal to 10 g·mil / 100 inch. 2 Water vapor transmission rate per day (MVTR), including values ​​greater than 10 g·mil / 100 inches. 2 / day, greater than or equal to 20 grams per 100 inches 2 / day, greater than 20 grams per 100 inches 2 / day, greater than or equal to 25 grams per 100 inches 2 / day, or greater than or equal to 30 mils / 100 inches 2 / day. In one or more embodiments, the water vapor transmission rate (MVTR) of the first polymer material of the first outer layer is less than or equal to 80 g·mil / 100 inches. 2 / day, including 70 grams per 100 inches or less.2 / day, less than or equal to 60 mils / 100 inches 2 / day or less than or equal to 40 mils / 100 inches 2 / day. For example, in a multilayer film embodiment, the first outer layer may have a density greater than 10 g·mil / 100 inches. 2 / less than or equal to 70 grams per 100 inches 2 MVTR within the range of / day.

[0055] In one or more embodiments, the polymer material of the first outer layer comprises a polyamide. In one or more embodiments, the polyamide comprises a polymer based on nylon 6,6 / 6 copolymer (polyhexamethylene adipamide / caprolactam copolymer) or a polymer based on nylon 6 / 6,6 copolymer (polyhexamethylene adipamide / caprolactam copolymer). In one or more embodiments, the polyamide comprises nylon 6,6 / 6 copolymer (polyhexamethylene adipamide / caprolactam copolymer) or nylon 6 / 6,6 copolymer (polyhexamethylene adipamide / caprolactam copolymer). In one or more embodiments, the first outer layer comprising polyamide herein contains more than 10 g·mil / 100 inch. 2 / less than 40 grams per day per 100 inches 2 MVTR within the range of / day, and all values ​​and subranges in between.

[0056] The thickness of the first outer layer is typically from about 1 micrometer (0.039 mil) to about 100 micrometers (3.9 mil), and typically from about 2 micrometers (0.079 mil) to about 30 micrometers (1.18 mil) or about 4 micrometers (0.16 mil) to about 25 micrometers (0.98 mil).

[0057] The multilayer membrane comprises two or more inner layers containing ethylene-vinyl alcohol (“EVOH”). Each EVOH-containing layer independently contains retortable grade ethylene-vinyl alcohol (EVOH). An exemplary EVOH is SoarnoL. TM RB7405 (Soarus) is a retortable grade EVOH containing 29% ethylene. In one or more embodiments, the EVOH-containing layer independently contains >97% to 100% EVOH. In one or more embodiments, the EVOH-containing layer each contains 100% EVOH.

[0058] Compared to the entire multilayer barrier film, the volume percentage of each EVOH-containing layer is independently from about 1% to about 20% by volume, and typically from about 1% to about 15% by volume. In one or more embodiments, the total EVOH-containing layers in the multilayer film are typically from about 2 vol% to about 40 vol%, or from about 2 vol% to about 30 vol%. Preferably, the total amount of EVOH-containing layers is 20% or less, or 10% or less, or 5% or less by weight.

[0059] The inner layer between the EVOH-containing layers is water-permeable or highly water-permeable. In one or more embodiments, the inner layer between the EVOH-containing layers comprises a second polymer material having a content greater than or equal to 10 g·mil / 100 inch. 2 Water vapor transmission rate per day (MVTR), including values ​​greater than 10 g·mil / 100 inches. 2 / day, greater than or equal to 20 grams per 100 inches 2 / day, greater than 20 grams per 100 inches 2 / day, greater than or equal to 25 grams per 100 inches 2 / day, or greater than or equal to 30 mils / 100 inches 2 / day. In one or more embodiments, the water vapor transmission rate (MVTR) of the second polymer material of the inner layer between the EVOH-containing layers is less than or equal to 80 g·mil / 100 inches. 2 / day, including 70 grams per 100 inches or less. 2 / day, less than or equal to 60 mils / 100 inches 2 / day or less than or equal to 40 mils / 100 inches 2 / day. For example, in embodiments of multilayer films, the inner layers between the EVOH-containing layers can have a density greater than 10 g·mil / 100 inches. 2 / less than or equal to 80 grams per 100 inches 2 MVTR within the range of / day.

[0060] In one or more embodiments, the second polymer material comprises a polyamide. In one or more embodiments, the polyamide comprises a polymer based on a nylon 6,6 / 6 copolymer (polyhexamethylene adipamide / caprolactam copolymer) or a polymer based on a nylon 6 / 6,6 copolymer (polyhexamethylene adipamide / caprolactam copolymer). In one or more embodiments, the polyamide comprises a nylon 6,6 / 6 copolymer (polyhexamethylene adipamide / caprolactam copolymer) or a nylon 6 / 6,6 copolymer (polyhexamethylene adipamide / caprolactam copolymer). In one or more embodiments, the polyamide-containing layer herein comprises more than 10 g·mil / 100 inch.2 / less than 40 grams per day per 100 inches 2 MVTR within the range of / day, and all values ​​and subranges in between.

[0061] The thickness of the inner layer between the EVOH-containing layers is typically from about 2 micrometers (0.079 mils) to about 20 micrometers (0.79 mils), and typically from about 4 micrometers (0.16 mils) to about 15 micrometers (0.59 mils).

[0062] The reference to inner layers between EVOH-containing layers means that any EVOH-containing layer present in a multilayer film is separated by a water-permeable or highly water-permeable layer, which may include, for example, layers containing greater than or equal to 10 g·mil / 100 inch. 2 The polymeric material used for MVTR per day is, for example, polyamide. When two EVOH-containing layers are present, there is a permeable stratification between them in addition to the outer layer of the multilayer membrane. When three EVOH-containing layers are present, there are two such permeable stratifications between them in addition to the outer layer of the multilayer membrane.

[0063] The second outer layer of a multilayer film typically refers to the innermost layer exposed to the internal contents of the container, such as food. This second outer layer, including the sealing layer, can be used to form a bag, in which case the sealing layer is typically heat-sealed to itself. Alternatively, the sealing layer can be used to bond to the base material at adjacent bonding surfaces, typically by heat sealing, to form a peripheral seal. The base material can be, for example, a rigid or flexible container bottom comprising polypropylene or polyethylene. The base material can also be a second multilayer film of the same or different type as the multilayer film. For example, in embodiments where a retortable container is formed by folding a multilayer film over itself and heat-sealing the overlapping edges, the multilayer film and the base material must be identical, as must their adjacent sealing layers. Generally, the sealing layer can comprise any suitable thermoplastic material, including but not limited to synthetic polymers such as polyesters, polyamides, polyolefins, polystyrene, etc. Thermoplastic materials can also include any synthetic polymer crosslinked by radiation or chemical reaction during manufacturing or post-manufacturing process operations. Exemplary polyolefins include polyethylene (PE) and polypropylene (PP).

[0064] The preferred sealing layer comprises (e.g., more than 50% by weight of a major amount) or is substantially composed of: (1) polypropylene or (2) a blend of polypropylene and at least one other polyolefin. The polyolefin includes polyolefin plastics that can be blended in the sealing layer, such as polyethylene. The sealing layer may also comprise (e.g., more than 50% by weight of a major amount) or is substantially composed of: (i) cast retortable polypropylene, (ii) a co-extruded polypropylene polymer or copolymer, or (iii) a co-extruded polypropylene polymer or copolymer and at least one other polyolefin. In one specific embodiment, the sealing layer comprises 100% cast retortable polypropylene by weight. A specific representative cast retortable polypropylene has about 0.9 g / cm³. 3 (For example, from approximately 0.85 g / cm³) 3 To approximately 0.95 g / cm 3 The density is within the range of 2.1 g / 10 min (e.g., in the range of about 1.9 g / 10 min to about 2.3 g / 10 min).

[0065] The thickness of the sealing layer is typically from about 1 micrometer (0.039 mil) to about 75 micrometers (3.0 mil), and typically from about 2 micrometers (0.079 mil) to about 25 micrometers (0.98 mil).

[0066] An adhesive layer or coating or layer can be provided between any layers to provide adhesion and continuity between these layers. The adhesive resin composition may include, but is not limited to: modified and unmodified polyolefins, preferably modified polyolefins containing anhydride groups; modified and unmodified acrylate resins, preferably selected from the group consisting of: ethylene / vinyl acrylate copolymers, ethylene / ethyl acrylate copolymers, ethylene / butyl acrylate copolymers, or blends thereof. EVA is an ethylene / vinyl acetate copolymer, which can be particularly used as a forming layer to facilitate the bonding of dissimilar polymer layers.

[0067] The adhesive layer or binder coating may suitably be less than 10% of the total thickness of the multilayer film, and preferably between 0.1% and 10%. Adhesive resins are often more expensive than other polymers, so the adhesive layer thickness is typically kept to a minimum to achieve the desired effect.

[0068] A moisture barrier layer can be placed between the last (second or third) EVOH-containing layer and the sealing layer. The sealing layer provides a moisture barrier.

[0069] In one or more embodiments, the multilayer film comprises less than or equal to 20% by weight of EVOH-containing material, including less than or equal to 10% by weight, or less than or equal to 5% by weight. In one or more embodiments, the multilayer film comprises less than or equal to 20% by weight of polyamide-containing material, including less than or equal to 10% by weight, or less than or equal to 5% by weight. In one or more embodiments, the multilayer film comprises both EVOH-containing material and polyamide-containing material in an independent amount of less than or equal to 20% by weight, including less than or equal to 10% by weight, or less than or equal to 5% by weight.

[0070] manufacture

[0071] Exemplary multilayer films can be formed by co-extruding several polymer resins.

[0072] One or more embodiments of a method for preparing a multilayer barrier film for food packaging include: extruding a first polymer resin of a first polymer material through a die to form a first outer layer, wherein the first polymer material has a water vapor transmission rate (MVTR) greater than or equal to 10 g·mil / 100 inch² / day; extruding a second polymer resin of a first retortable grade ethylene vinyl alcohol (EVOH) copolymer through a die to form a first inner layer; extruding a third polymer resin of the second polymer material through a die to form a second inner layer, wherein the second polymer material has a water vapor transmission rate (MVTR) greater than or equal to 10 g·mil / 100 inch² / day; extruding a fourth polymer resin of a second retortable grade ethylene vinyl alcohol (EVOH) copolymer through a die to form a third inner layer; and forming a second outer layer from one or more extrudable polymer resins.

[0073] The method may further include extruding a fifth polymer resin through a die to form a fourth inner layer located between the third inner layer and the second outer layer.

[0074] In one or more embodiments, the second outer layer includes a co-extruded sublayer such that the first sublayer of the second outer layer includes a polyolefin, and the second sublayer of the second outer layer is an adhesive layer such that the second sublayer is between the first sublayer and the third or fourth inner layer.

[0075] To form the packaging, a sealing layer of any of the films disclosed herein is adhered to itself or another film to form a seam in the sidewall. The packaging may further include markings in its film.

[0076] Before describing several exemplary embodiments of the invention, it should be understood that the invention is not limited to the details of the construction or process steps set forth in the following description. The invention can have other embodiments and can be practiced or implemented in various ways.

[0077] See attached image. Figure 1 This is a cross-sectional view of an exemplary multilayer barrier film 100 having five layers. In order from the outside, these layers are: containing a density greater than or equal to 10 g·mil / 100 inches. 2 The first outer layer 114 of the first polymer material comprises a first retort-grade ethylene vinyl alcohol (EVOH) copolymer, having a water vapor transmission rate (MVTR) of 10 g·mil / 100 inch. 2 A second inner layer 110 of a second polymer material with a water vapor transmission rate (MVTR) of 110 / day, a third inner layer 108 comprising a second retortable grade ethylene vinyl alcohol (EVOH) copolymer, and a second outer layer 101 comprising two or more sublayers. In one or more embodiments, the second inner layer 110 and / or the second outer layer 101 further comprise an oxygen scavenging material for reacting with oxygen that has permeated the packaging or is trapped therein.

[0078] Figure 2 The image provides a cross-sectional view of another exemplary multilayer barrier film 150 as a 7-layer film. In order from the outside, the layers are: a first outer layer 164 containing polyamide, a first inner layer 162 containing a first retort-grade ethylene vinyl alcohol (EVOH) copolymer, a second inner layer 160 containing polyamide, a third inner layer 158 containing a second retort-grade ethylene vinyl alcohol (EVOH) copolymer, a fourth inner layer 156 containing polyamide, and a second outer layer 151 comprising two sublayers: a first sublayer 152 containing polyolefin and a second sublayer 154 containing an adhesive layer.

[0079] Figure 3 This is an exploded perspective view of an exemplary retortable container 200 having a top web 202 and a bottom web 204. The top web 202 is a membrane. In one or more embodiments, the top web 202 is any multilayer barrier membrane according to this disclosure. A sealing layer (not labeled) of the top web 202 is attached to a sealing surface 206 of the bottom web 204 via a heat-sealing portion 208. In one or more embodiments, the bottom web 204 is any multilayer barrier membrane according to this disclosure. In one or more embodiments, both the top web 202 and the bottom web 204 are independently any multilayer barrier membrane according to this disclosure. The bottom web 204 is preferably thermoformed, and the top web 202 may be thermoformed, otherwise formed, or may be unformed.

[0080] Figure 4This is a plan view of an exemplary retortable container 220 having a top web 222 and a bottom web 224. The bottom web 224 is any multilayer barrier film according to this disclosure. The bottom web 224 is thermoformed to provide a chamber for containing packaged products. The top web 222 is heat-sealed to a sealing surface 226 of the bottom web 224. The top web 222 is made of a film that may be the same as or different from the film of the bottom web 224. The top web 222 may be thermoformed, otherwise formed, or unformed.

[0081] Figure 5 This is a plan view of an exemplary retortable container in the form of an airtight package 240, including a product 246, such as a pharmaceutical or food product, sealed within an interior 244 of the package 240, which includes any multilayer barrier film 242 disclosed herein. The product 246 is in contact with a sealing layer (not labeled) of the film 242. In some embodiments, the package 240 consists essentially of the film 242. The film 242 forms the interior 244 of the package 240, which is defined by a heat-sealed portion 248 formed along each edge 250, 251, 252, 253 of the package. In the depicted embodiment, dashed lines indicate sealing portions of the package 240 that define the sealed interior 244.

[0082] Figure 6 This is a schematic side view of an exemplary retortable container in the form of a stand-up pouch 260, suitable for liquid packaging. Pouch 260 includes sidewalls 264, an opening 266, and a bottom gusset 268. The sidewalls 264 and / or the bottom gusset 268 can be formed from any film 262 disclosed herein. The film 262 is heat-sealed to form side seals 270, 272 and a bottom seal 276. After filling, the edges 274 are heat-sealed to form a top seal.

[0083] Figure 7 This is a plan view of another exemplary retortable container in the form of a bag 280, which is suitable for liquid packaging. Bag 280 includes sidewalls formed by any of the films 282 disclosed herein. Film 282 is heat-sealed to form a seal 290. Marking 292 may be provided as part of film 282 at any suitable location, including the location between a first outer layer and a second outer layer of film 282. Alternatively, marking 292 may be printed directly on the first outer layer.

[0084] like Figure 3-7As demonstrated, the multilayer film of this invention is advantageous for any component of retort packaging, especially thermoformed retort packaging. For example, the film of this invention is suitable for semi-rigid or flexible thermoformed webs. The film of this invention is also suitable for caps used with semi-rigid or flexible thermoformed webs. When handled and processed in different ways, the multilayer film of this invention provides a durable oxygen barrier layer. The advantage of the multilayer film of this invention over other retort structures containing, for example, AlOx or SiOx is that the multilayer film of this invention can be deep drawn by thermoforming. The multilayer film of this invention can also be stretched and used in other ways without compromising the oxygen barrier.

[0085] Example

[0086] from The layer made of C33LN (BASF) (which is the copolymer PA6 / 66 used in the examples herein) has a thickness of 10 g. mil / 100 inches or greater. 2 Water vapor transmission rate (MVTR) per day. The layer made from 5033FD825 (Ube Industries, Inc.) (which is a polyamide copolymer based on nylon 6,66 used in the examples herein) has a value greater than or equal to 20 g·mil / 100 inch. 2 Water vapor transmission rate (MVTR) per day.

[0087] Example 1

[0088] An asymmetric multilayer barrier film with a total thickness of 101.5 micrometers (4 mils) was manufactured using blown film co-extrusion technology. The barrier film has the following structure:

[0089] First outer layer: Polyamide, Nylon 6,66. Product name: C33LN (BASF) is a copolymer of PA6 / 66.

[0090] First inner layer (first EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus) - Ethylene-vinyl alcohol copolymer (EVOH), retortable grade.

[0091] Second inner layer: Polyamide, Nylon 6,66. Product name: C33LN (BASF) is a copolymer of PA6 / 66.

[0092] Third inner layer (second EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus Corporation).

[0093] Fourth inner layer: Polyamide, Nylon 6.66. Product name: C33LN (BASF).

[0094] Second outer layer (two sub-layers): Admer TM The polypropylene (PP)-based adhesive sublayer of QF-500A (“QF”) (maleic anhydride-grafted polypropylene); and the PP-based sealing sublayer of polypropylene impact copolymer PPC 4170 (all).

[0095] Example 1's structural abbreviation is: PA / EVOH / PA / EVOH / PA / PP adhesive layer / PP (blow molding).

[0096] Example 2

[0097] An asymmetric multilayer barrier film with a total thickness of 101.5 micrometers (4 mils) was manufactured using blown film co-extrusion technology. The barrier film has the following structure:

[0098] First outer layer: Trade name 5033FD825 (Ube Industries, Inc.), which is a copolymer based on nylon 6,66.

[0099] First inner layer (first EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus) - Ethylene-vinyl alcohol copolymer (EVOH), retortable grade.

[0100] The second inner layer, trade name 5033FD825 (Ube Industries, Inc.), is a copolymer based on nylon 6,66.

[0101] Third inner layer (second EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus Corporation).

[0102] Fourth inner layer: Trade name: 5033FD825 (Ube Industries, Inc.), which is a copolymer based on nylon 6,66.

[0103] Second outer layer (two sub-layers): Admer TM The polypropylene (PP)-based adhesive sublayer of QF-500A (“QF”) (maleic anhydride-grafted polypropylene); and the PP-based sealing sublayer of polypropylene impact copolymer PPC 4170 (all).

[0104] The structural abbreviation for Example 2 is: PA / EVOH / PA / EVOH / PA / PP adhesive layer / PP (blow molding).

[0105] Example 3

[0106] Comparison

[0107] An asymmetric multilayer barrier film with a total thickness of 101.5 micrometers (4 mils) was manufactured using blown film co-extrusion technology. The barrier film has the following structure:

[0108] First outer layer: Polyamide, Nylon 6,66. Product name: C33LN (BASF) is a copolymer of PA6 / 66.

[0109] First inner layer (first EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus) - Ethylene-vinyl alcohol copolymer (EVOH), retortable grade.

[0110] Second inner layer: Admer TM The adhesive layer of QF-500A (“QF”) (maleic anhydride-grafted polypropylene) is based on polypropylene (PP).

[0111] Third inner layer (second EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus Corporation).

[0112] Fourth inner layer: Polyamide, Nylon 6.66. Product name: C33LN (BASF) is a copolymer of PA6 / 66.

[0113] Second outer layer (two sub-layers): Admer TM The polypropylene (PP)-based adhesive sublayer of QF-500A (“QF”) (maleic anhydride-grafted polypropylene); and the PP-based sealing sublayer of polypropylene impact copolymer PPC 4170 (all).

[0114] This structure is abbreviated as: PA / EVOH / PP adhesive layer / EVOH / PA / PP adhesive layer / PP (blow molding).

[0115] Example 4

[0116] Comparison

[0117] An asymmetric multilayer barrier film with a total thickness of 101.5 micrometers (4 mils) was manufactured using blown film co-extrusion technology. The barrier film has the following structure:

[0118] First outer layer: Polyamide, Nylon 6,66. Product name: C33LN (BASF) is a copolymer of PA6 / 66.

[0119] First inner layer (first EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus) - Ethylene-vinyl alcohol copolymer (EVOH), retortable grade.

[0120] Second inner layer: Admer TM The adhesive layer of QF-500A (“QF”) (maleic anhydride-grafted polypropylene) is based on polypropylene (PP).

[0121] Third inner layer (second EVOH-containing layer): Ethylene-vinyl alcohol (EVOH) copolymer (29%). Trade name: SoarnoL TM RB7405 (Soarus Corporation).

[0122] Fourth inner layer: Polyamide, Nylon 6.66. Product name: C33LN (BASF) is a copolymer of PA6 / 66.

[0123] Second outer layer (three sub-layers): Admer TM The QF-500A (“QF”) (maleic anhydride-grafted polypropylene) consists of a polypropylene (PP)-based adhesive sublayer; a first PP-based sealing sublayer (all) of polypropylene impact copolymer PPC 4170; and a second PP-based sealing sublayer (all) of polypropylene impact copolymer PPC 4170.

[0124] This structure is abbreviated as: PA / EVOH / PP adhesive layer / EVOH / PA / PP adhesive layer / PP / PP (blow molding).

[0125] Example 5

[0126] test

[0127] The membranes of Examples 1-2 and Comparative Examples 3-4 were exposed to a first set of cooking conditions at 123°C (254°F) water spray for 1 hour under an overpressure of 30 psi.

[0128] After exposure to the first cooking conditions, the oxygen barrier properties of these membranes were determined. Figure 8 The oxygen permeability (OTR) cc / m² produced by the membranes in Examples 1-2 is provided. 2 A curve showing the time elapsed between the end of the first cooking condition and the end of the cooking process (recovery curve). Figure 9 The OTR cc / m values ​​generated by the membranes in Comparative Examples 3-4 are provided. 2 A graph showing the recovery period (days) relative to the time elapsed after the first cooking condition was completed. Table 1 provides an overview of other information about these membranes.

[0129] Table 1.A

[0130]

[0131]

[0132] Table 1.B

[0133]

[0134] For Example 2, the cookable copolymer containing nylon 6 / 6,6 produced a defect-free outer layer, with no blistering or white streaks visible upon visual inspection. Example 1, using a conventional nylon 6 / 6,6 copolymer, exhibited blistering and white streaks in the outer layer, which were visible upon visual inspection. Not intended to be theoretically sound, it is assumed that the defects caused by blistering and streaks allow more water to enter the EVOH layer during cooking. Therefore, Example 1 showed a higher initial OTR immediately after cooking compared to Example 2. Figure 8 As shown in the figure. Compared to Example 1, the absence of foaming and white streaks in Example 2 resulted in a lower initial OTR after cooking, which is evident in... Figure 8 As shown in the figure. Within approximately 35 hours after cooking, both Examples 1 and 2 recovered their oxygen barrier properties (≤1 cc / m³). 2 (days). The cooking recovery rate of Examples 1 and 2 was 99%, while the cooking recovery rate of the comparative examples was 47% for Comparative Example 3 and 48% for Comparative Example 4.

[0135] Transfer to Figure 9 Compared to Examples 1 and 2, Comparative Examples 3 and 4 showed lower initial OTR after cooking. However, compared to Examples 1 and 2, the OTR of Comparative Examples 3 and 4 recovered to ≤1 cc / m³. 2 The time taken is longer. Observations of equilibrium OTR values ​​(OTR 145 hours after cooking) at 50% RH outside / 90% provide some explanation, rather than being intended to be theoretically constrained. As can be seen from the equilibrium OTR data presented in Table 1, Examples 1 and 2 show improved oxygen barrier compared to Comparative Examples 3 and 4. Given the long shelf life of typical cooked products, the total oxygen ingress during the shelf life can be expected to be large. Assuming a product shelf life of one year (365 days), the approximate oxygen ingress is calculated using the following formula:

[0136]

[0137] Where t1 is the first time point (hr) after steaming, t n It is the nth time point (hr) after steaming or boiling, t ∞This is the time it takes for OTR to reach equilibrium (here, 145 hours), T (days) is the assumed product shelf life (here, 365 days), and OTR1 is the OTR at time point t1 (cc / (m2.day.atm)). n At time point t n The OTR (cc / (m2.day.atm)), and OTR ∞ It is recorded in Table 1 in t ∞ OTR (cc / (m2.day.atm)). OTR ∞ The equilibrium OTR concentrations are recorded in Table 1.

[0138] As shown in Table 1, Example 2 demonstrates the lowest oxygen ingress during the product's assumed shelf life. This unexpected result (despite a higher initial OTR after cooking) is a consequence of placing a moisture-permeable polyamide layer between the EVOH layers. Polyamide is a hygroscopic polymer that absorbs water during cooking. Placing polyamide between the two EVOH layers results in a significantly higher initial OTR after cooking. On the other hand, polypropylene between the EVOH layers (Comparative Examples 3 and 4) results in a lower initial OTR. However, polyamide also has a relatively high MVTR (>20 g mils / 100 inch² / day), while polypropylene has an MVTR of <5 g mils / 100 inch² / day. The relatively high MVTR of polyamide allows the buried EVOH to dry more quickly. Therefore, OTR recovery is faster. Examples 1 and 2 both show significant cooking recovery. On the other hand, Comparative Example 3, with polypropylene between the two EVOH layers, and Comparative Example 4, without polyamide in the inner layer, tend to confine the moisture / water absorbed during cooking within the buried EVOH layer for a longer period. Therefore, cooking recovery is slower. When the balanced OTR was extrapolated to cover the product shelf life, the results showed that Example 2 demonstrated a lower oxygen intake per unit area.

[0139] Example 6

[0140] test

[0141] Fresh samples of the membranes from Examples 1-2 and Comparative Examples 3-4 were exposed to a second set of distillation conditions at 121°C water spray for 1 hour at 40 psi atmosphere.

[0142] After exposure to the second cooking conditions, the oxygen barrier properties of these membranes were determined. Figure 10 The oxygen permeability (OTR) cc / m² produced by the membranes in Examples 1-2 is provided. 2 A graph showing the time elapsed between the end of the second cooking condition and the end of the recovery period (recovery curve). Figure 11 The OTR cc / m values ​​generated by the membranes in Comparative Examples 3-4 are provided. 2A graph showing the recovery time relative to the end of the second cooking condition. Tables 2.A and 2.B provide an overview of additional information about these membranes.

[0143] Table 2.A

[0144]

[0145]

[0146] Table 2.B

[0147]

[0148] At higher cooking pressures, Example 2 again had the lowest approximate oxygen inlet (OTR) of all examples. Example 1 and Comparative Example 3 were comparable. Comparative Example 4 had the highest OTR inlet relative to all examples. The cooking recovery rate of Example 2 was 96%, and that of Example 1 was 99%, while the cooking recovery rates of the comparative examples were 45% for Comparative Example 3 and 43% for Comparative Example 4.

[0149] Example

[0150] Example A: A multilayer barrier film for food packaging, the multilayer barrier film comprising:

[0151] The first outer layer comprises a layer having a density greater than or equal to 10 g. mils / 100 inches. 2 The first polymer material with a water vapor transmission rate (MVTR) of / day;

[0152] A first inner layer adjacent to the first outer layer, the first inner layer comprising a first retortable ethylene vinyl alcohol (EVOH) copolymer;

[0153] A second inner layer adjacent to the first inner layer, the second inner layer comprising a content greater than or equal to 10 g·mil / 100 inch. 2 The second polymer material has a water vapor transmission rate (MVTR) of / day;

[0154] A third inner layer adjacent to the second inner layer, the third inner layer comprising a second retortable ethylene vinyl alcohol (EVOH) copolymer; and

[0155] Including the second outer layer of the sealing layer;

[0156] The first polymer material is not a cookable grade ethylene vinyl alcohol (EVOH) copolymer.

[0157] Membrane Example B: A multilayer barrier membrane as described in any other membrane example, wherein the water vapor transmission rate (MVTR) of the first polymer material of the first outer layer is greater than or equal to 10 g·mil / 100 inches.2 / less than 80 grams per 100 inches per day. 2 Within the range of / day.

[0158] Membrane Example C: A multilayer barrier membrane as described in any other membrane example, wherein the water vapor transmission rate (MVTR) of the second polymer material of the second inner layer is greater than 20 g·mil / 100 inch. 2 / sky.

[0159] Membrane Example D: A multilayer barrier membrane as described in any other membrane example, wherein the water vapor transmission rate (MVTR) of the second polymer material of the second inner layer is greater than 10 g·mil / 100 inches. 2 / less than 80 grams per 100 inches per day. 2 Within the range of / day.

[0160] Membrane Example E: A multilayer barrier membrane as described in any other membrane example, wherein the first polymer material of the first outer layer and the second polymer material of the second inner layer independently comprise polyamide.

[0161] Membrane Example F: A multilayer barrier membrane as described in any other membrane example, wherein the first polymer material of the first outer layer is a retortable polyamide.

[0162] Membrane Example G: A multilayer barrier membrane as described in any other membrane example, wherein the first outer layer is in direct contact with the first inner layer, the first inner layer is in direct contact with the second inner layer, and the second inner layer is in direct contact with the third inner layer.

[0163] Membrane Example H: A multilayer barrier membrane as described in any other membrane example, further comprising a fourth inner layer located between the third inner layer and the second outer layer, the fourth inner layer comprising a third polymer material.

[0164] Membrane Example I: A multilayer barrier membrane as described in Membrane Example H, wherein the third polymer material comprises polyamide or polypropylene.

[0165] Membrane Example J: A multilayer barrier membrane as described in any other membrane example, wherein the second outer layer comprises two or more sublayers.

[0166] Membrane Example K: A multilayer barrier membrane as described in Membrane Example J, wherein the first sublayer of the second outer layer comprises a polyolefin, and the second sublayer of the second outer layer is an adhesive layer such that the second sublayer is between the first sublayer and the third or fourth inner layer.

[0167] Membrane Example L: A multilayer barrier membrane as described in any other membrane example, which is thermoformable.

[0168] Membrane Example M: ​​A multilayer barrier membrane as described in any other membrane example, wherein the first outer layer, the first, second, third, and fourth inner layers, and the second outer layer are co-extruded.

[0169] Membrane Example N: A multilayer barrier membrane as described in any other membrane example, having a thickness ranging from about 38.1 micrometers (1.5 mils) to about 1,143 micrometers (45 mils).

[0170] Membrane Example O: A multilayer barrier membrane as described in any other membrane example, having a cooking recovery rate of greater than or equal to 90% within approximately 46.5 hours after exposure to cooking conditions of 250°F ± 5°F for 60 minutes and 30 psi overpressure.

[0171] Example P: A multilayer barrier film for food packaging, the multilayer barrier film comprising:

[0172] The first outer layer comprises a first polyamide;

[0173] A first inner layer adjacent to the first outer layer, the first inner layer comprising a first retortable ethylene vinyl alcohol (EVOH) copolymer;

[0174] A second inner layer adjacent to and in direct contact with the first inner layer, the second inner layer comprising a second polyamide;

[0175] A third inner layer adjacent to and in direct contact with the second inner layer, the third inner layer comprising a second retortable ethylene vinyl alcohol (EVOH) copolymer;

[0176] A fourth inner layer, adjacent to and in direct contact with the third inner layer, comprising a polymer material containing polyamide or polypropylene; and

[0177] The second outer layer adjacent to the fourth inner layer;

[0178] The multilayer barrier film is thermoformable and has a thickness ranging from about 38.1 micrometers (1.5 mils) to about 1,143 micrometers (45 mils).

[0179] Membrane Example Q: A multilayer barrier membrane as described in Membrane Example P, wherein the first polyamide is a retortable polyamide.

[0180] Membrane Example R: A multilayer barrier membrane as described in Membrane Examples P or Q, wherein the water vapor transmission rate (MVTR) of the first outer layer and the second inner layer is independently greater than 10 g·mil / 100 inch. 2 / less than 40 grams per day per 100 inches 2 / sky.

[0181] Membrane Example S: A multilayer barrier membrane as described in membrane Examples P, Q or R, wherein the second outer layer includes a sublayer such that the first sublayer of the second outer layer includes a polyolefin, and the second sublayer of the sealing layer is an adhesive layer such that the first sublayer is between the first sublayer and the third or fourth inner layer.

[0182] Container Example A: A retortable container comprising a multilayer barrier membrane of any membrane example.

[0183] Container Example B: A retortable container as described in Container Example A, comprising a bottom sheet and a top sheet, the bottom sheet comprising a thermoformed film and the top sheet comprising a non-thermoformed film; wherein at least one of the bottom sheet and the top sheet comprises the multilayer barrier film.

[0184] Container Example C: A retortable container as described in Container Example A, which is in the form of a bag, the bag including one or more sidewalls formed by the multilayer barrier film.

[0185] Container Embodiment D: A retortable container as described in Container Embodiment A, comprising a bag including a sidewall and a gusset plate; wherein at least one of the sidewall and the gusset plate includes the multilayer barrier film.

[0186] Method Example A: A method for preparing a multilayer barrier film for food packaging, the method comprising:

[0187] A first polymer resin of a first polymer material is extruded through a mold to form a first outer layer, wherein the first polymer material has a content greater than or equal to 10 g·mil / 100 inch. 2 Water vapor transmission rate (MVTR) per day;

[0188] The second polymer resin of the first retortable ethylene vinyl alcohol (EVOH) copolymer is extruded through a mold to form the first inner layer;

[0189] The second polymer material is extruded through a mold to form the second inner layer by a third polymer resin, wherein the second polymer material has a content greater than or equal to 10 g·mil / 100 inch. 2 Water vapor transmission rate (MVTR) per day;

[0190] The fourth polymer resin of the second retortable ethylene vinyl alcohol (EVOH) copolymer is extruded through a die to form the third inner layer;

[0191] and

[0192] The second outer layer is formed from one or more extrudable polymer resins.

[0193] Method Example B: The method described in Method Example A further includes extruding a fifth polymer resin through a mold to form a fourth inner layer located between the third inner layer and the second outer layer.

[0194] Method Example C: The method of Method Example A, wherein the second outer layer includes a co-extruded sublayer, such that the first sublayer of the second outer layer includes a polyolefin, and the second sublayer of the second outer layer is an adhesive layer, such that the second sublayer is between the first sublayer and the third or fourth inner layer.

[0195] Method Example D: A method for packaging food in a retortable container, the method comprising:

[0196] Obtain a retortable container of any container embodiment;

[0197] The product is packaged in this retortable container; and

[0198] Expose the cookable container to cooking conditions.

Claims

1. A multilayer barrier film for food packaging, the multilayer barrier film comprising: The first outer layer comprises a weight of 20 g. mils / 100 inches or greater. 2 / less than 40 grams per day per 100 inches 2 The first polymer material with a water vapor transmission rate (MVTR) of / day; A first inner layer adjacent to the first outer layer, the first inner layer comprising a first retortable grade ethylene vinyl alcohol (EVOH) copolymer; A second inner layer adjacent to the first inner layer, the second inner layer comprising a content greater than or equal to 20 g. mils / 100 inches 2 / less than 40 grams per day per 100 inches 2 The second polymer material has a water vapor transmission rate (MVTR) of / day; A third inner layer adjacent to the second inner layer, the third inner layer comprising a second retortable ethylene vinyl alcohol (EVOH) copolymer; and Including the second outer layer of the sealing layer; The first polymer material is not a retortable ethylene vinyl alcohol (EVOH) copolymer; The first polymer material of the first outer layer and the second polymer material of the second inner layer independently comprise polyamide; and The water vapor transmission rate (MVTR) was measured according to ASTM-1249-13 under conditions including atmospheric pressure, 38°C, and 90% relative humidity.

2. The multilayer barrier membrane of claim 1, wherein the water vapor transmission rate (MVTR) of the first polymer material of the first outer layer is greater than or equal to 30 g·mil / 100 inches. 2 / less than 40 grams per day per 100 inches 2 Within the range of / day.

3. The multilayer barrier membrane of claim 1, wherein the water vapor transmission rate (MVTR) of the second polymer material in the second inner layer is greater than 20 g·mil / 100 inch. 2 / sky.

4. The multilayer barrier membrane of claim 1, wherein the water vapor transmission rate (MVTR) of the second polymer material in the second inner layer is greater than 30 g·mil / 100 inches. 2 / less than 40 grams per day per 100 inches 2 Within the range of / day.

5. The multilayer barrier film as claimed in claim 1, wherein the first outer layer is in direct contact with the first inner layer, the first inner layer is in direct contact with the second inner layer, and the second inner layer is in direct contact with the third inner layer.

6. The multilayer barrier film of claim 1, further comprising a fourth inner layer located between the third inner layer and the second outer layer, the fourth inner layer comprising a third polymer material.

7. The multilayer barrier film of claim 6, wherein the third polymer material comprises polyamide or polypropylene.

8. The multilayer barrier film as claimed in claim 1 or 6, wherein the second outer layer comprises two or more sublayers.

9. The multilayer barrier film of claim 8, wherein the first sublayer of the second outer layer comprises a polyolefin, and the second sublayer of the second outer layer is an adhesive layer such that the second sublayer is between the first sublayer and the third or fourth inner layer.

10. The multilayer barrier film as claimed in claim 1, wherein the multilayer barrier film is thermoformable.

11. The multilayer barrier film of claim 6, wherein the first outer layer, the first, second, third, and fourth inner layers, and the second outer layer are co-extruded.

12. The multilayer barrier membrane of claim 1, having a cooking recovery rate of greater than or equal to 90% within approximately 46.5 hours after exposure to cooking conditions of 250°F ± 5°F for 60 minutes and 30 psi overpressure.

13. A multilayer barrier film for food packaging, the multilayer barrier film comprising: The first outer layer comprises a first polyamide; A first inner layer adjacent to the first outer layer, the first inner layer comprising a first retortable grade ethylene vinyl alcohol (EVOH) copolymer; A second inner layer adjacent to and in direct contact with the first inner layer, the second inner layer comprising a second polyamide; A third inner layer adjacent to and in direct contact with the second inner layer, the third inner layer comprising a second retortable ethylene vinyl alcohol (EVOH) copolymer; A fourth inner layer, adjacent to and in direct contact with the third inner layer, comprising a polymer material containing polyamide or polypropylene; and The second outer layer adjacent to the fourth inner layer; The multilayer barrier film is thermoformable and has a thickness ranging from 38.1 micrometers (1.5 mils) to 1,143 micrometers (45 mils); and The water vapor transmission rate (MVTR) of the first outer layer and the second inner layer is independently greater than or equal to 20 g·mil / 100 inch. 2 / less than 40 grams per day per 100 inches 2 / sky.

14. The multilayer barrier membrane of claim 13, wherein the water vapor transmission rate (MVTR) of the first outer layer and the second inner layer is independently greater than 20 g·mil / 100 inch. 2 / less than 40 grams per day per 100 inches 2 / sky.

15. The multilayer barrier film of claim 13, wherein the second outer layer comprises a sublayer, such that the first sublayer of the second outer layer comprises a polyolefin, and the second sublayer of the second outer layer is an adhesive layer, such that the second sublayer is between the first sublayer and the fourth inner layer.

16. A cookable container comprising the multilayer barrier membrane as described in claim 1.

17. The retortable container of claim 16, the retortable container comprising a bottom sheet and a top sheet, the bottom sheet comprising a thermoformed film and the top sheet comprising a non-thermoformed film; wherein at least one of the bottom sheet and the top sheet comprises the multilayer barrier film.

18. The retortable container of claim 16, wherein the retortable container is in the form of a bag, the bag including one or more sidewalls formed by the multilayer barrier film.

19. The retortable container of claim 16, the retortable container comprising a bag, the bag comprising a sidewall and a gusset plate; wherein at least one of the sidewall and the gusset plate comprises the multilayer barrier film.

Images