Resealable bags having controllable water vapor transmission rate

Abstract

Provided is a resealable bag for packaging fresh produce, the resealable bag includes: a multilayer film including a high water vapor transmission rate (high-WVTR) layer including polyamide polymer, wherein the multilayer film has a WVTR value of at least 20 g / m2 per day; and a resealable closure element affixed along an opening edge of the bag, wherein the resealable closure element is made substantially of polyolefin or thermoplastic polyurethane (TPU) polymer, and wherein a compatibilizer being grafted to the polyolefin or TPU polymer, to facilitate the affixation of the resealable closure element to the multilayer film.

Description

[0001] RESEALABLE BAGS HAVING CONTROLLABLE WATER VAPOR TRANSMISSION RATE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of produce packaging. More specifically, the disclosure relates to resealable bags for packing fresh produce, where the packaging film has a controllable high water vapor transmission rate.

[0004] BACKGROUND

[0005] Fresh produce packaging often employs polyolefin-based films such as cast polypropylene, biaxially oriented polypropylene, and certain grades of polyethylene or laminated film structures such as BOPP / PET and PE / PET. While these films offer good mechanical properties, they share a notable drawback: low water vapor transmission rates (WVTR). During storage, water vapor released by produce respiration raises the headspace relative humidity inside the packaging. Because polyolefins and laminates containing them transmit water vapor poorly, the headspace quickly approaches saturation. Such high humidity and the condensate that inevitably forms from it accelerate microbial decay and can trigger physiological disorders, including regrowth of shoots and sprouting in root vegetables.

[0006] By contrast, polyamide films have a high WVTR, allowing excess moisture to escape from the headspace. This moisture regulation helps maintain the visual quality of fresh produce and reduces microbial spoilage and the aforementioned physiological disorders throughout the supply chain.

[0007] In cases where resealable packaging is desired, closure elements such as zippers are often applied at the opening edge. These elements allow the consumer to repeatedly open, reseal, and store the produce. However, attaching resealable closures to polyamide films presents compatibility challenges, as such closures are commonly made from polyolefins or thermoplastic polyurethane, which do not readily bond to polyamides.

[0008] Accordingly, there remains a need in the art for a well-suited assembly that enables the use of moisture-regulating polyamide films with resealable closure elements, thereby combining extended produce freshness with convenient, repeated access.

[0009] SUMMARY

[0010] The disclosure herein is directed, in embodiments thereof, to a resealable bag for packaging fresh produce. The bag includes a polyamide film to which a resealable closure element, such as a zipper, is affixed. The film includes a multilayer structure configured to provide a high WVTR value of at least 20 g / m2per day.

[0011] In some embodiments, the resealable closure element is made predominantly from polyolefin or thermoplastic polyurethane (TPU), which incorporates a compatibilizer compound. Advantageously, the polyolefin / TPU-grafted compatibilizer, according to some embodiments, facilitates the compatibility between the polyamide polymer of the bag film and the polyolefin / TPU polymer of the closure element. As a result, the film / closure element assembly can withstand at least a hand-applied tensile force in an attempt to separate them.

[0012] Furthermore, the film configuration may improve welding or adhesion strength by providing a sealing layer with a relatively low sealing temperature compared to that of the high- WVTR layer. The lower sealing temperature is compatible with the melting point of the closure element, thereby facilitating a production process of the assembly.

[0013] There is provided, in accordance with some aspects of the presently disclosed subject matter, a resealable bag for packaging fresh produce, the resealable bag includes: a multilayer film including a high water vapour transmission rate (high-WVTR) layer including polyamide polymer, wherein the multilayer film has a WVTR of at least 20 g / m2per day; and a resealable closure element affixed along an opening edge of the bag, wherein the resealable closure element is made substantially of polyolefin or thermoplastic polyurethane (TPU) polymer, and wherein a compatibilizer being grafted to the polyolefin or TPU polymer, to facilitate the affixation of the resealable closure element to the multilayer film.

[0014] According to some embodiments, the high-WVTR layer has a sealing temperature of at least 210 °C.

[0015] According to some embodiments, the multilayer film further includes a sealing layer including a copolymer and / or a blend of polymers, the sealing layer is adhered to a first surface of the high-WVTR layer.

[0016] According to some embodiments, the sealing layer has a sealing temperature of less than 205 °C.

[0017] According to some embodiments, the sealing layer constitutes less than 35% (v / v) of the multilayer film.

[0018] According to some embodiments, the compatibilizer includes maleic anhydride, glycidyl methacrylate, acrylic acid, itaconic acid, itaconic anhydride, fumaric anhydride, butyl acrylate, succinic anhydride, isophorone diisocyanate, vinyl sulfone, and / or sulfonyl chloride. According to some embodiments, the compatibilizer includes maleic anhydride, glycidyl methacrylate, acrylic acid, itaconic acid, itaconic anhydride, and / or fumaric anhydride.

[0019] According to some embodiments, the compatibilizer includes maleic anhydride.

[0020] According to some embodiments, the resealable closure element includes the compatibilizer in an amount of 0.2-5 wt% of the element.

[0021] According to some embodiments, the resealable closure element includes the compatibilizer in an amount of 1.0-2.5 wt% of the element.

[0022] According to some embodiments, the resealable closure element includes a portion configured to be affixed to the multilayer film, wherein the portion comprises the compatibilizer.

[0023] According to some embodiments, the multilayer film is devoid of polypropylene and / or polyethylene.

[0024] According to some embodiments, the polyolefin in the resealable closure element includes polypropylene, polyethylene, and / or polyethylene vinyl acetate).

[0025] According to some embodiments, the resealable closure element is affixed to the multilayer film through the sealing layer.

[0026] According to some embodiments, the resealable closure element is in a form selected from: press-to-close, hook-to-hook, slider, double track, tripletrack, slider, tamper, and evident.

[0027] According to some embodiments, the resealable bag is a stand-up bag.

[0028] According to some embodiments, the high-WVTR layer includes two or more sublayers.

[0029] According to some embodiments, the polyamide of the high-WVTR layer includes polycaprolactam (PA6).

[0030] According to some embodiments, the sealing layer has a sealing temperature of less than 200 °C.

[0031] According to some embodiments, the copolymer includes a copolymer of polyamide.

[0032] According to some embodiments, the copolymer of polyamide is selected from PA6 / 66, PA6 / 12, and PA66 / 69 / 610 / 61.

[0033] According to some embodiments, the copolymer includes a copolymer of polystyrene.

[0034] According to some embodiments, the copolymer of polystyrene is a copolymer including monomer units selected from: styrene butadiene styrene (SBS), styrene butadiene (SB), styrene ethylene butylene styrene (SEBS), styrene ethylene propylene styrene (SEPS), and styrene isoprene styrene (SIS). According to some embodiments, the copolymer includes SBS copolymer.

[0035] According to some embodiments, the blend of polymers includes two or more polymers selected from polycaprolactam (PA6), polyhexamethylene adipamide (PA66), polydodecanolactam (PA12), polyhexamethylene azelaamide (PA69), hexamethylene sebacamide (PA610), poly(ll-aminoundecanoamide) (PA11), poly(hexamethylene dodecanoamide (PA6 / 12), PA6 / 66, PA6 / 12, and PA66 / 69 / 610 / 61.

[0036] According to some embodiments, the two or more polymers include polymers PA6 / 66 and PA66 / 69 / 610 / 61.

[0037] According to some embodiments, the resealable bag further includes an additional layer adhered to a second surface of the high-WVTR layer.

[0038] There is provided, in accordance with some aspects of the presently disclosed subject matter, a process of producing the resealable bag disclosed herein, including affixation of the resealable closure element to the multilayer film by heating an assembly of said multilayer film and resealable closure element at a temperature of between 145-250 °C.

[0039] According to some embodiments, during the affixation, steps of a cross seal, a crush seal, and / or a skirt seal are performed at a heating temperature of between 145-250 °C.

[0040] One or more technical advantages may be readily apparent to those skilled in the art from the figures, descriptions and claims included herein. Moreover, various embodiments may include all, some or none of the technical advantages.

[0041] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the figures and by study of the following detailed descriptions.

[0042] BRIEF DESCRIPTION OF THE FIGURES

[0043] Some embodiments of the disclosure are described herein with reference to the accompanying figures. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments may be practiced. The figures are for the purpose of illustrative description, and no attempt is made to show structural details of an embodiment in more detail than is necessary for a fundamental understanding of the disclosure. For the sake of clarity, some objects depicted in the figures are not to scale.

[0044] In the figures:

[0045] FIGURE 1 shows an example of a pouch including green beans, according to some embodiments; FIGURE 2 shows an example of a pouch including cucumbers, according to some embodiments; and

[0046] FIGURE 3 shows an example of a pouch including lychee, according to some embodiments.

[0047] DETAILED DESCRIPTION

[0048] In the following description, various aspects of the disclosure will be described. For the purpose of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the different aspects of the disclosure. However, it will also be apparent to one skilled in the art that the disclosure may be practiced without specific details being presented herein. Furthermore, well-known features may be omitted or simplified in order not to obscure the disclosure.

[0049] Prior to setting forth the present subject matter in detail, it may be helpful to provide definitions of certain terms to be used herein. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this subject matter pertains. The following definitions are provided for clarity.

[0050] The term “a” or “an” as used herein includes the singular and the plural, unless specifically stated otherwise. Therefore, the terms “a,” “an,” or “at least one” can be used interchangeably in this application.

[0051] In this description and in the claims, the verb “comprise” and its conjugations are used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded.

[0052] As used herein, the term “about” when used in connection with a numerical value includes ±10% from the indicated value. In addition, all ranges directed to the same component or property herein are inclusive of the endpoints, are independently combinable, and include all intermediate points and ranges.

[0053] As used herein, the term “multilayer film” refers to a flexible sheet material composed of two or more layers of polymers (and sometimes other materials) that are co-extruded, laminated, or otherwise bonded together into a single structure. The layers may include a similar, identical, or different polymer. As used herein, the term “resealable closure element” refers to a device, such as a zipper, that is attached to the opening of a package and allows the package to be repeatedly opened and closed while maintaining a seal to protect its contents.

[0054] Fresh produce packaging often relies on polyolefin films or laminated structures thereof, which have low water vapor transmission rates (WVTR) that trap humidity and accelerate spoilage. Polyamide films, with their higher WVTR, allow excess moisture to escape, preserving freshness and appearance during storage and transport.

[0055] The disclosed packaging combines a moisture-regulating polyamide film with a resealable closure element, such as a zipper, to provide both extended shelf life and consumer convenience. The multilayer film is configured for a WVTR of at least 20 g / m2per day. The closure, made from polyolefin or thermoplastic polyurethane, incorporates a grafted compatibilizer compound to promote strong bonding with the polyamide film. This configuration delivers a durable assembly, which can withstand manual separation forces. Further, the configuration enables efficient production by matching sealing temperatures to the closure’s melting point.

[0056] There is provided, in accordance with some aspects of the presently disclosed subject matter, a resealable bag for packing fresh produce. The resealable bag includes a multilayer film, characterized by a high-water vapor transmission rate (high -WVTR), hereinafter: high- WVTR layer, of at least 20 g / m2per day.

[0057] As used herein, the term “water vapor transmission rate” or “WVTR” refers to the water vapor transmission rate as measured in accordance with ASTM E96 at 23 °C, under a relative humidity gradient of 100 / 50% or 100 / 10%.

[0058] According to some embodiments, the high-WVTR layer is made substantially from polyamide. The polyamide enables the high WVTR characteristics of the high-WVTR layer, and as a result, it permits the high WVTR of the multilayer film, in total. In some embodiments, at least 70% of the multilayer film is made of polyamide, for example, at least 75%, at least 80%, at least 90%, or 100% of the multilayer film is made of polyamide. The high-WVTR layer of the multilayer film includes polyamide and has a WVTR value of at least 20 g / m2per day.

[0059] In some embodiments, the multilayer film has a WVTR of at least 25 g / m2per day, at least 30 g / m2per day, or at least 40 g / m2per day. In some embodiments, the multilayer film has a WVTR of 20-40 g / m2per day, 30-80 g / m2per day, 40-90 g / m2per day, 50-100 g / m2per day, or 80-120 g / m2per day. The multilayer film preferably has a WVTR value suitable to provide little or no condensation on the internal surface of the packaging film when used to package fresh produce under typical storage and shipment conditions of the produce in question. This may be also enhanced by the incorporation of an anti-fog agent in the film (detailed below).

[0060] The multilayer film may be perforated to provide suitable O2 and CO2 permeability for the fresh produce that is to be packaged. The number, size, and pattern of the perforations required depend on the respiration rate of the produce to be packed and the desired modified atmosphere. For example, the film may be macroperforated to provide holes having a diameter of approximately 1-10 mm covering up to about 0.5% of the surface area of the packaging film, and / or the multilayer film may be microperforated to provide holes having a diameter of about 0.05-1 mm diameter at a density of up to about 2000 holes per square meter of material. Preferably, the packaging film is microperforated to provide holes having a diameter of about 0.1-0.8 mm at a density of up to about 500 holes per square meter of material. Microperforations are typically provided by laser treatment. Macroperforations may be provided by physical puncturing or cutting of the film. For example, a packaging film used for packing 1.51b Persian cucumbers typically contains laser perforations of 125±15 pm and will provide modified atmosphere conditions of 10-15% O2 and 5-10% CO2 under steady state conditions at 10-12°C, the optimal storage temperature for such cucumbers. These conditions will preserve the quality of the cucumbers, slowing aging processes.

[0061] The resealable bag includes a resealable closure element. The element may be affixed along an opening edge of the bag and enables repeated opening and closure of the bag. Resealing a high WVTR resealable bag may help regenerate the required relative humidity and gas compositions in the bag to preserve quality until it is consumed.

[0062] The resealable closure element may be made substantially of polyolefin polymer. In contrast, the multilayer film is substantially made of polyamide.

[0063] In some embodiments, the multilayer film is substantially devoid of polyolefin, such as polypropylene and / or polyethylene or TPU. The multilayer film may be substantially devoid of a polymer that is compatible with the polymer of the resealable closure element. The multilayer film may be devoid of a polymer that is compatible with the polymer of the resealable closure element. The polymer of the film (e.g., polyamide), which is incompatible with the polymer of the closure element, constitutes at least 80%, at least 85%, or at least 90%, of the total polymers in the film. Each possibility is a separate embodiment. In some embodiments, at least 80% of the film is not made of polyolefin or TPU. Hence, the presently disclosed resealable bag herein provides a compatibilized assembly of a multilayer film, including mainly polyamide, and a resealable closure element, including mainly polyolefin or TPU. The compatibility is enabled by an incorporation of a compatibilizer in the resealable closure element.

[0064] According to some embodiments, a compatibilizer is grafted to the polyolefin polymer to facilitate the affixation of the resealable closure element, which is substantially made of polyolefin, to the multilayer film, which is substantially made of polyamide. The compatibilizer may improve the compatibility of polyolefin with the polyamide. As a result, the resealable closure element is well affixed to the multilayer film.

[0065] As used herein, the term “compatibilizer” refers to a molecular additive used to improve adhesion or compatibility between two otherwise incompatible polymers. As a result, the compatibilizer enhances seal integrity and mechanical strength of the assembled parts (e.g., multilayer film and closure element). As used herein, the term “grafted” refers to a moiety / functional group / chemical entity that is chemically attached to a polymer.

[0066] In some embodiments, the resealable closure element, including the compatibilizer, remains attached / adhered / welded to the multilayer film, even when subjected to a parting trial of the assembly. When the assembly is subjected to a peel force of a strong 80 kg man's hands, delamination is not determined. The integrity of the bond between the film and the element, according to some embodiments, is high. The compatibilizer grafted to the polyolefin strengthens the affixation between the film and the closure element. In contrast, when a compatibilizer is not included in the resealable closure element, the resealable closure element will not seal to the film and / or will be removed with minimum, if any, applied force.

[0067] According to some embodiments, the multilayer film further includes a sealing layer. The sealing layer may be adhered to one surface of the high-WVTR layer.

[0068] As used herein, the term “sealing layer” refers to a layer having a lower sealing temperature, as compared to the high-WVTR layer and / or the multilayer film. It may enable a smooth sealing of the film as a result of its lower melting point.

[0069] The sealing layer may include copolymer(s) and / or a blend of polymers. The copolymer(s) and / or a blend of polymers may be substantially made of polyamide derivatives. The combination of the type of polyamide derivatives as a blend and / or as a copolymer may lower the melting temperature of the sealing layer. As a result, in some embodiments, the sealing layer has a sealing temperature of less than 205 °C. As used herein, the term “sealing temperature” is intended to be the lowest temperature at which the layer in question will melt sufficiently to fuse with another layer to form a hermetic seal when subjected to heat and pressure in a heat-sealing apparatus.

[0070] The sealing temperature may be measured using a Laboratory Heat Sealer according to ASTM F2029 at constant pressure and sealing time. The pressure may be in the range from 0.05 MPa to 0.7 MPa (e.g. 0.5 MPa) and the sealing time may be in the range from 0.15 s to 0.5 s (e.g. 0.3 s). The sealing temperature may be determined across a range of temperatures, e.g. from 150 °C to 300 °C, or 250 °C. For example, the sealing temperature of the sealing layer may be less than 200 °C, less than 195 °C, less than 190 °C, less than 180 °C, less than 170 °C, or less than 160 °C. Each possibility is a separate embodiment.

[0071] According to some embodiments, the high-WVTR layer has a sealing temperature of at least 210 °C, for example, at least 215 °C, at least 220 °C, at least 230 °C, or at least 240 °C. Each possibility is a separate embodiment.

[0072] The sealing layer facilitates sealing of a package including the herein disclosed multilayer film. One side / end of the film may be fin-sealed with another side / end of the film, utilizing the low sealing temperature of the sealing layer. In a fin sealing, according to some embodiments, an inner layer of one end of the film is sealed to another inner layer of another end of the film.

[0073] The low sealing temperature of the sealing layer may facilitate welding of the multilayer film with the resealable closure element.

[0074] Accordingly, in some embodiments, the resealable closure element may be affixed to the multilayer film through the sealing layer, utilizing the low melting temperature of the sealing layer.

[0075] In some other embodiments, the resealable closure element may be affixed directly to the high-WVTR of the multilayer film, i.e., without a sealing layer. For example, a resealable closure element made substantially of TPU, including a compatibilizer, may be affixed to the high-WVTR layer.

[0076] According to some embodiments, the compatibilizer may be selected from: maleic anhydride, glycidyl methacrylate, acrylic acid, itaconic acid, itaconic anhydride, fumaric anhydride, butyl acrylate, succinic anhydride, isophorone diisocyanate, vinyl sulfone, and / or sulfonyl chloride. Each possibility is a separate embodiment. The compatibilizer may include maleic anhydride, glycidyl methacrylate, acrylic acid, itaconic acid, itaconic anhydride, and / or fumaric anhydride. Each possibility is a separate embodiment. The compatibilizer may include or is maleic anhydride. According to some embodiments, the resealable closure element includes the compatibilizer in an amount of 0.1-5 wt% of the element, for example, 0.5-4 wt%, 2-4 wt%, or 0.2-3 wt%. In some embodiments, a portion of the resealable closure element, which is associated with the film, e.g., an outer / exterior portion or an outer layer of the element, includes the compatibilizer in an amount of 0.1-5 wt% of the element, for example, 0.2-4 wt%, 0.2-3 wt%, or 0.2-3 wt%. Each possibility is a separate embodiment.

[0077] The compatibilizer may constitute 0.2-4 wt%, 0.2-3 wt%, or 0.2-3 wt% of the element closure’s polymer. The compatibilizer may constitute 0.2-4 wt%, 0.2-3 wt%, or 0.2-3 wt% of the element closure’s polymer portion, which is associated with the multilayer film. Each possibility is a separate embodiment. Preferably, according to some embodiments, the resealable closure element includes the compatibilizer in an amount of 1.0-2.5 wt% of the element. The compatibilizer may constitute 1.0-2.2 wt% of the polymer portion, which is associated with the multilayer film, for example, 1.0-2.0 wt%, 1.0-1.8 wt%, or 1.2-1.7 wt%. Each possibility is a separate embodiment. The amount of the compatibilizer may ensure the affixation of the resealable closure element to the multilayer film. A lower amount of the compatibilizer may compromise the beneficial mechanical affixation / welding / binding of the assembly (i.e., assembly of the film with the element).

[0078] According to some embodiments, the peripheral portion of the resealable closure element may include the compatibilizer. The peripheral portion, including the compatibilizer, may be configured to be affixed / associated with the multilayer film, thereby facilitating the affixation / welding of the film with the element. The compatibilizer may be disposed in a portion of the element that is associated with the multilayer film, e.g., the peripheral portion of the resealable closure element. In some embodiments, the resealable closure element has a peripheral / external layer that includes the compatibilizer. The inclusion of the compatibilizer may be via grafting of the compatibilizer to the polyolefin in said portion associated / affixed to the multilayer film, e.g., via reactive extrusion.

[0079] In some embodiments, the resealable closure element includes TPU and / or polyolefin, such as polypropylene, polyethylene, and / or ethylene vinyl acetate. Each possibility is a separate embodiment. In some embodiments, the resealable closure element includes or is substantially made of polyolefin, such as polypropylene and / or polyethylene. In some embodiments, the resealable closure element may include or be substantially made of thermoplastic polyurethane (TPU). The resealable closure element (e.g., zipper) may be in a form selected from: press-to- close, hook-to-hook, slider, double track, triple track, slider, tamper, and evident. Each possibility is a separate embodiment.

[0080] In some embodiments, the resealable bag may be a stand-up bag / pouch.

[0081] According to some embodiments, the high-WVTR layer may be composed of two or more sub-layers, which together form the high-WVTR layer of the multilayer film. For example, the high-WVTR layer may include two, three, or four sub-layers. Each possibility is a separate embodiment. In some embodiments, the high-WVTR includes three or four sublayers. The sub-layers may have identical composition to each other, or one or more of the sublayers may have a different composition. For example, one or more of the sub -layers may include an additive or additives as described in more detail below. One or more of the sublayers may be substantially free from additives. Typically, the sub-layers include a polyamide, which is the same polyamide.

[0082] Typically, the high-WVTR layer of the multilayer film includes PA6 (polycaprolactam). It may include PA6 in combination with EVA (polyethylene vinyl acetate)), EBA (poly(ethylene butyl acrylate)) and / or EMA (poly(ethylene methyl acrylate)). The copolymers may include vinyl acetate (VA), butyl acrylate (BA), or methyl acrylate (MA), in an amount of between 7-40 wt%, of the copolymer, or in any intermittent range or value within this range, e.g., 7-11 wt%, 15-30 wt%, or 20-35 wt%. Thus, the WVTR of film including sub-layers of EVA, EMA, or EBA depends, respectively, on the percentage of vinyl acetate, methyl acrylate, or butyl acrylate in the copolymer. For example, EVA copolymer containing 24% vinyl acetate can be used at a concentration of up to 60% of the total formulation weight.

[0083] The high-WVTR layer may include at least 1 wt % in total of EVA, EBA and / or EMA with respect to the total weight of the multilayer film, e.g. at least 3 wt %, at least 5 wt % at least 10 wt%, or at least 15 wt%, wherein the percentage of the non-ethylene units (e.g., VA, BA, or MA) is between 7-10 wt% of the copolymer. Each possibility is a separate embodiment. The addition of EVA, EBA, and / or EMA permits the WVTR value of the high-WVTR layer of the film to be manipulated. Typically, the addition of these polymers tends to reduce the WVTR value. Nevertheless, the value of WVTR of the multilayer film is kept above 20 gr / m2per day.

[0084] In some embodiments, one of the sub-layers of the multilayer film may include at least 80 wt% of the EVA (polyethylene vinyl acetate)), EBA (poly(ethylene butyl acrylate)), and / or EMA (poly(ethyl methyl acrylate)), with respect to that sub-layer weight. For example, one of the sub-layers includes at least 82 wt%, at least 85 wt%, at least 87 wt%, or at least 90 wt%, EVA, EBA, or EMA (e.g., EVA) with respect to that sub-layer weight. Each possibility is a separate embodiment.

[0085] In some embodiments, the sublayer including the EVA (polyethylene vinyl acetate)), EBA (poly(ethylene butyl acrylate)) and / or EMA (poly(ethyl methyl acrylate)), constitutes between 7-25% of the total multilayer film thickness, for example, between 10-25%, between 10-15%, or between 7-17%, of the total multilayer film thickness. Each possibility is a separate embodiment.

[0086] Typically, the sealing layer of multilayer film has a thickness of 5 pm or less, more preferably 4 pm or less, 3 pm or less, or 2 pm or less. Typically, the sealing layer of the multilayer film has a thickness of at least 0.53 pm or at least 0.8 pm. According to some embodiments, the sealing layer constitutes less than 35% of the multilayer film thickness, for example, less than 30%, less than 25%, less than 20%, or less than 15% of the multilayer film thickness. Each possibility is a separate embodiment. The thickness distribution of the sealing layer may be 3-35%, with respect to the total multilayer film thickness, e.g., 3-30%, 3-25%, 5- 20%, 5-15%, or preferably 3-20% or 3-10%. Each possibility is a separate embodiment.

[0087] The sealing layer of the multilayer film may be composed of two or more sub-layers, which together form the sealing layer of the multilayer film. In some embodiments, the sublayers may have identical compositions to each other, or, in some embodiments, one or more of the sub-layers may have a different composition. For example, one or more of the sub-layers may include an additive or additives as described in more detail below. One or more of the sublayers may be substantially free from additives. In some embodiments, all of the sub-layers comprise the same polymer. Typically, the sealing layer is formed from a single layer (i.e., does not include sub-layers).

[0088] The sealing layer of the multilayer film may include:

[0089] (i) a copolyamide, such as PA6 / 66, PA6 / 12, optionally in combination with a multipolyamide such as PA66 / 69 / 610 / 61;

[0090] (ii) a blend of two or more polyamides / copolyamides (i.e., homo-, co- or multipolyamides) selected from, but not limited to, PA6 (polycaprolactam), PA66 (Polyhexamethylene adipamide), PA12 (Polydodecanolactam), PA69 (Polyhexamethylene azelaamide), PA610 (hexamethylene sebacamide), PA11 (Poly(ll-aminoundecanoamide), PA6 / 12 Poly(hexamethylene dodecanoamide), PA6 / 66, PA6 / 12, and PA66 / 69 / 610 / 61;

[0091] (iii) one or more styrene copolymers, optionally blended with PS (polystyrene) or HIPS (high impact polystyrene), for example one or more styrene copolymers selected from the group consisting of SBS (styrene butadiene styrene copolymer), SBC (styrene butadiene copolymers), SEBS (styrene ethylene butylene styrene), SEPS (styrene ethylene propylene styrene), SIS (styrene isoprene copolymers); or

[0092] (iv) a single homopolymer selected from PA11 and PA12.

[0093] As the skilled person will understand, PA6I (included in multi-polyamide PA66 / 69 / 610 / 61 identified above) is polyhexamethylene isophthalamide.

[0094] Particularly suitable is a blend of PA6 / 66 with PA66 / 69 / 610 / 61. In some embodiments, the ratio between the copolyamides of the blend may be between 5: 1 and 2: 1, respectively. For example, between 4: 1 and 2: 1, or between 3: 1 and 2:1. Each possibility is a separate embodiment.

[0095] Particularly suitable is SBS.

[0096] In some embodiments, the two or more sub-layers of the high-WVTR layer may each independently include polyamide polymer in an amount of at least 85% with respect to the total thickness of the sub-layer, for example, at least 87%, at least 90%, or at least 92%. Each possibility is a separate embodiment. A sub-layer of the high-WVTR layer may include, for example, a thickness that is 90-100%, 92-100%, 95-100%, or 100% polyamide (e.g., PA6), with respect to the thickness of that sub-layer.

[0097] According to some embodiments, the thickness distribution of each sub-layer of the high-WVTR layer may be 10-40%, with respect to the total thickness of the multilayer film, for example, 12-35%, 15-35%, or 15-30%. Each possibility is a separate embodiment.

[0098] According to some embodiments, the high-WVTR layer and / or the sealing layer may include one or more additives. For example, anti-block additive may be added to reduce the risk of blocking, which is the adhesion of two adjacent layers of film. Anti-block additive may be provided to the high-WVTR layer and / or sealing layer. Typically, it is provided to one or more sub-layers of the high-WVTR layer, in an amount of 0.1 -5 wt% with respect to the weight of that sub-layer. Alternatively, 0.1 -5 wt% of anti -block additive may be added to the sealing layer of the multilayer film (or sub-layers thereof). The skilled person will be familiar with the selection of suitable anti-block additives. Suitable anti-block additives include Ultramid B40LN available from BASF (a high viscosity PA6 with enhanced formability due to the addition of nucleating and slip agents), and S tyrolux NB10 available from Styrolution (an SBC polymer including an active wax system to reduce sheet blocking).

[0099] An anti-fog additive may be added to reduce fogging of the resealable bag multilayer film. The anti-fog additive may be added to any one of the sub-layers, e.g., at a level of 0.1 -20 wt% with respect to the total weight of the sub-layer to which it is added, e.g. at a level of 0.5- 15 wt%. The skilled person will be familiar with the selection of suitable anti -fog additives. Suitable anti-fog additives include Polybatch AF1088 (a polyolefin based anti -fog additive) available from A. Shulman.

[0100] A bonding agent may be added to the sealing layer of multilayer film to enhance bonding. The skilled person is familiar with the selection of suitable bonding agents. For example, the bonding agent is added where the sealing layer comprises one or more styrene copolymers. Bonding agent is typically added at a level of 5-40 wt%, e.g. 5-35 wt% with respect to the total weight of the sub-layer to which it is added. Suitable bonding agents may be modified polyamides or modified polyolefins, e.g., a modified linear low density polyethylene. The agent may be modified with maleic anhydride. A suitable bonding agent is Orevac 18910 available from Arkema.

[0101] A Slip- / Anti-block masterbatch may be used to lower the coefficient of friction (COF) and to avoid blocking of the films. The Slip additive may be added to any one of the sub-layers, e.g., at a level of 0.1-10 wt% with respect to the total weight of the sub-layer to which it is added, e.g. at a level of 0.5-10 wt%. The skilled person will be familiar with the selection of suitable slip additives. Suitable slip additives include GSA3022ST (based on PETG polymer with anti-block particles and wax) available from IQAP masterbatch.

[0102] The slip agent may be included in one or more of the sub-layers of the multilayer film that is in an outer sub-layer with respect to the high-WVTR layer. The slip agent may be included in one or more of the sub-layers of the multilayer film that is on an opposite side of the high-WVTR layer, with respect to the sealing layer.

[0103] The particular layers that are chosen for any particular fresh produce packaging application are determined by factors such as the produce to be packed, supply chain length, sensitivity to excess moisture, sensitivity to dehydration, and surface area to volume ratio. For example, Persian cucumbers are sensitive to excess moisture that aggravates microbial decay. As such, a film with a WVTR value of 80-100 g / m2per day is suitable for shipment of such cucumbers throughout the supply chain from Mexico to USA and Canada.

[0104] Typically, the multilayer film of the present invention has a total thickness of 70 pm or less, e.g., 60 pm or less, 50 pm or less, 40 pm or less, or 25 pm or less. Each possibility is a separate embodiment. The multilayer film may have a thickness of at least 5 pm or at least 10 pm. The multilayer film may have a thickness of between 5-70 pm, for example, 5-50 pm, 5- 40 pm, or 5-35 pm. Each possibility is a separate embodiment.

[0105] Typically, the multilayer film is formed by extruding a first polymer for forming the first layer and a second polymer for forming the second layer and forming the first and second polymers into a multilayer film. Typically, the first and second polymers are extruded simultaneously (co-extruded). The extrusion is typically through annular film dies, e.g., with manifolds for the different layers being located at different radial distances from the center of the die. Air is typically injected into the center of the die to inflate a bubble of extruded polymer. The bubble is typically then cooled, collapsed, and slit to form flat sheet film. The layered film is typically rolled to provide a roll of film once cooled. The skilled person will be familiar with techniques for forming layered polymer films by extrusion.

[0106] The multilayer film may include a single layer, such as a single-layer film including PA6 blended with one or more co-polyamides or multi-polyamides, or a single-layer film including a co-polyamide, optionally blended with a multi-polyamide. The single-layer film may include one or more additives as described and defined above with reference to the multilayer packaging film. The co-polyamide and multi-polyamides are typically as described and defined above with reference to the multilayer packaging film.

[0107] The single-layer film may be composed of two or more sub-layers, which together form the multilayer film. The sub-layers may have identical composition to each other, or one or more of the sub-layers may have a different composition. For example, one or more of the sublayers may include an additive or additives. One or more of the sub-layers may be substantially free from additives.

[0108] There is provided, in accordance with some aspects of the presently disclosed subject matter, a package of fresh produce including the herein disclosed resealable bag. The fresh produce package is typically a modified atmosphere package. As used herein, “modified atmosphere” packaging is intended to include packaging wherein the multilayer film has been selected or modified to control one or more of the water vapors, CO2, and O2 concentrations inside the package in order to prolong the shelf life of the packaged fresh produce.

[0109] As used herein, the term “fresh produce” is intended to include fruits, vegetables, flowers, plants, mushrooms, and other edible or inedible horticultural or botanical products which are perishable and tend to spoil or otherwise have a limited shelf life. The present invention is particularly suitable for packaging fruits and vegetables that benefit from modified atmosphere packaging, suitable for packing in a container, and are sensitive to excess moisture. The fresh produce may be selected from, but not limited to, cucumbers, green beans, guava, squash, stone fruits, including nectarines, peaches, and plums, cherries, blueberries, longan, lychee, rambutan, mangosteen, and kiwi. Each possibility is a separate embodiment.

[0110] Reference is now made to FIG. 1, which shows a package of green beans packed with the herein disclosed resealable bag having a zipper at the upper part of the bag. The WVTR value of the pouch is 92 g / m2per day. This value is in accordance with the sensitivity of the beans to dehydration and excess moisture.

[0111] Reference is now made to FIG. 2, which shows a package of cucumbers packed with the herein disclosed resealable bag having a zipper at the upper part of the bag. The WVTR value of the pouch is 92 g / m2per day. This value is in accordance with the sensitivity of the cucumbers to dehydration and excess moisture.

[0112] Reference is now made to FIG. 3, which shows a package of lychee packed with the herein disclosed resealable bag having a zipper at the upper part of the bag. The WVTR value of the pouch is 24 g / m2per day. This value is in accordance with the sensitivity of the lychee to dehydration and excess moisture.

[0113] There is provided, in accordance with some embodiments, a process of producing the resealable bag disclosed herein. The process includes affixing the resealable closure element to the multilayer film by heating an assembly of said multilayer film and resealable closure element at a temperature of between 145-250 °C. For example, the process may include heating the assembled film-element at temperatures between 150-200 °C, 160-190 °C, 170-220 °C, 205-220 °C, 170-200 °C, and / or 220-235 °C. Each possibility is a separate embodiment.

[0114] In some embodiments, the lower sealing temperature is compatible with the melting point of the closure element, thereby facilitating the production process of the assembly.

[0115] According to some embodiments, steps of a cross seal, a crush seal, and / or a skirt seal are performed at a heating temperature below 215 °C, below 210 °C, below 205 °C, or below 190 °C. Each possibility is a separate embodiment. The steps may be performed at a temperature of between 145-250 °C or 145-200 °C, for example, between 160-200 °C, 170- 200 °C, or 180-200 °C. Each possibility is a separate embodiment.

[0116] EXAMPLES

[0117] Film preparation

[0118] Multilayer films according to the present invention were prepared by extrusion through blown film dies. Extruders were used to melt and push molten resin into an annular film die. Each layer was formed by a separate spiral mandrel manifold at a different radial distance from the center of the die. Air was injected into the center of the annular die to inflate the polymer bubble. The bubble was cooled by an air ring that blows air on the surface of the bubble to lower its temperature until it solidifies. Above the die, a stabilizing cage was used to minimize movement of the bubble as it collapsed in the collapsing frame to make a flat film. This tubed film was then pulled over rolls, slit at the sides and fed into film winders to make the finished sheet film rolls.

[0119] The following temperature profile, as detailed in Table 1, was used to prepare the layered films:

[0120] Table 1. Temperature profile during extrusion

[0121] Testing models

[0122] Thickness was measured at 24 points across the width of the film using a Millimess Inductive Digital Comparator Extramess 2001.

[0123] WVTR value was measured at 23 °C and a gradient of 100 / 50% or 100 / 10% relative humidity according to ASTM E96.

[0124] Sealing temperature range was measured using a Laboratory Heat Sealer according to ASTM F2029 at constant pressure and time. Dwell time was 0.15-0.5 s in a temperature range of 150-200 °C.

[0125] Materials

[0126] The following materials, as detailed in Tables 2 and 3, were used in the Examples below:

[0127] Table 2, Material source

[0128] Table 3. Abbreviations

[0129] Example 1 - Multilayer films with blended polyamide sealing layer Four examples of film structures having a sealing layer formed from a blend of copolyamides were prepared by the process described above, and tested for WVTR value and sealing temperature using the testing methods described above. The compositions and testing results are given below in Tables 4-7.

[0130] Table 4. Multilayer film including a sealing layer made from blended copolyamides

[0131] Table 5. Multilayer film including a sealing layer made from blended copolyamides Table 6. Multilayer film including a sealing layer made from blended copolyamides

[0132] Table 7. Multilayer film including a sealing layer made from blended copolyamides Example 2 - Multilayer films with styrene-based sealing layer

[0133] Two examples of film structures having a sealing layer formed from a blend of styrene copolymer and a bonding agent were prepared by the process described above. The compositions of the films are given below in Tables 8 and 9.

[0134] Table 8. Multilayer film including a sealing layer made from a blend of styrene copolymer

[0135] Table 9. Multilayer film including a sealing layer made from a blend of styrene copolymer

[0136] Testing results

[0137] Packaging multilayer films prepared according to Examples 1 and 2 above were tested as described above. The results were as follows, in Table 10:

[0138] Table 10. Test results of thickness, WVTR, and sealing temperatures.

[0139] The WVTR value of a 20 pm film of PA6 is also 145 g / m2per day, and accordingly it can be seen that the addition of the sealing layer does not adversely affect the WVTR value of the multilayer film. However, the sealing temperature of PA6 is 220-245 °C, and accordingly it can be seen that the addition of the sealing layer advantageously reduces the sealing temperature.

[0140] Example 3 - welding the resealable closure element to the multilayer film of the bag

[0141] 1. Film Feeding and Web Alignment - supplied film under ideal tension and alignment.

[0142] • The film roll was mounted on the unwinder.

[0143] • Dancer rollers regulated film tension.

[0144] • Edge Position Control (EPC) kept the film centered for accurate print-to-seal registration.

[0145] 2. Zipper Feeding and Sealing - attached the zipper tape to the flat film.

[0146] • Zipper tape was unwound from a dedicated roll.

[0147] • A zipper applicator placed the tape on the inside face of the film near the top edge.

[0148] • Tacking seal bars bonded the zipper to the film at 445-455°F (229-235°C) on the top bar and 415-425°F (213-218°C) on the bottom bar, with a dwell time of 0.2 seconds. 3. Film Folding and Gusset Formation - formed the basic pouch shape.

[0149] A plough folding plate folded the film lengthwise with the zipper at the top edge. Gusset fingers pushed inward from both sides to create the bottom gusset.

[0150] As a result, the film was shaped like a flat pouch with a gusseted base.

[0151] 4. Zipper-End Crush Sealing - flattened zipper ends at the future side seal zones for hermetic sealing.

[0152] • Narrow heated compression jaws (or ultrasonic sealing units) applied pressure to the zones where the zipper crosses the side seal path.

[0153] • Sealing occurred at 360-380°F (182-193°C), reducing thickness and removing trapped air.

[0154] • The result was a flat, uniform seal area to support proper side sealing.

[0155] 5. Side Sealing (Cross Sealing) - created vertical side seams.

[0156] • Heat-seal bars pressed the folded film edges together at 360-380°F (182-193°C).

[0157] • Flattened zipper ends ensured even heat and pressure distribution across the seal.

[0158] 6. Bottom Sealing (Skirt Sealing) - sealed the bottom gusset closed.

[0159] • The bottom edge was flattened and sealed across its entire width.

[0160] • Sealing temperature was maintained at 360-380°F (182-193°C).

[0161] 7. K-Sealing (Comer or Diagonal Gusset Sealing) - reinforced the corners of the bottom gusset.

[0162] • Angled heated sealing jaws (typically at a 30°-45° angle) applied pressure at 375- 385°F (191-196°C).

[0163] • The jaws clamped across the gusset corner area at the side seam line.

[0164] • All layers were fused together in the triangular zone for added strength.

[0165] 8. Cutting and Separation - converted the continuous film web into individual pouches.

[0166] • Servo-driven rotary or guillotine knives cut between sealed areas.

[0167] • Finished pouches were discharged individually from the machine.

[0168] Example 4 - assessing the duality of the bond between the closure element and the film

[0169] Water Tank Leak Test:

[0170] The prepared resealable bag, as described in the previous examples, was subjected to a leak test by immersion in a water tank while pressurized to 20 inches of mercury (Hg) for a duration of 20 seconds. The internal pressurization was applied to approximately 60% of the total air volume of the bag. The presence of air bubbles during the test may indicate a leak failure. However, no bubbles were observed during the tests.

[0171] Zipper test: A cut perpendicular to the zipper direction was made through the zipper. Then, the zipper bonding was tested by attempting to remove the zipper from the sealant layer. The zipper, having a strong bond with the film, was broken apart rather than being separated from the film. It will be recognized that examples, embodiments, modifications, options, etc., described herein are to be construed as inclusive and non-limiting, i.e., two or more examples, etc., described separately herein are not to be construed as being mutually exclusive of one another or in any other way limiting, unless such is explicitly stated and / or is otherwise clear. Those skilled in the art to which this invention pertains will readily appreciate that numerous changes, variations, and modifications can be made without departing from the scope of the presently disclosed subject matter, mutatis mutandis.

Claims

CLAIMS1. A resealable bag for packaging fresh produce, the resealable bag comprising: a multilayer film comprising a high water vapour transmission rate (high- WVTR) layer comprising polyamide polymer, wherein the multilayer film has a WVTR of at least 20 g / m2per day; and a resealable closure element affixed along an opening edge of the bag, wherein the resealable closure element is made substantially of polyolefin or thermoplastic polyurethane (TPU) polymer, and wherein a compatibilizer being grafted to the polyolefin or TPU polymer, to facilitate the affixation of the resealable closure element to the multilayer film.

2. The resealable bag of claim 1 , wherein the high-WVTR layer has a sealing temperature of at least 210 °C.

3. The resealable bag of claim 1 or 2, wherein the multilayer film further comprises a sealing layer comprising a copolymer and / or a blend of polymers, the sealing layer is adhered to a first surface of the high-WVTR layer.

4. The resealable bag of claim 3, wherein the sealing layer has a sealing temperature of less than 205 °C.

5. The resealable bag of any one of claims 1-4, wherein the sealing layer constitutes less than 35% (v / v) of the multilayer film.

6. The resealable bag of any one of claims 1-5, wherein the compatibilizer comprises maleic anhydride, glycidyl methacrylate, acrylic acid, itaconic acid, itaconic anhydride, fumaric anhydride, butyl acrylate, succinic anhydride, isophorone diisocyanate, vinyl sulfone, and / or sulfonyl chloride.

7. The resealable bag of claim 6, wherein the compatibilizer comprises maleic anhydride, glycidyl methacrylate, acrylic acid, itaconic acid, itaconic anhydride, and / or fumaric anhydride.

8. The resealable bag of claim 7, wherein the compatibilizer comprises maleic anhydride.

9. The resealable bag of any one of claims 1-8, wherein the resealable closure element comprises the compatibilizer in an amount of 0.2-5 wt% of the element.

10. The resealable bag of claim 9, wherein the resealable closure element comprises the compatibilizer in an amount of 1.0-2.5 wt% of the element.

11. The resealable bag of any one of claims 1-10, wherein the resealable closure element comprises a portion configured to be affixed to the multilayer film, wherein the portion comprises the compatibilizer.

12. The resealable bag of any one of claims 1-11, wherein the multilayer film is devoid of polypropylene and / or polyethylene.

13. The resealable bag of any one of claims 1-12, wherein the polyolefin in the resealable closure element comprises polypropylene, polyethylene, and / or poly(ethylene vinyl acetate).

14. The resealable bag of any one of claims 3-13, wherein the resealable closure element is affixed to the multilayer film through the sealing layer.

15. The resealable bag of any one of claims 1-14, wherein the resealable closure element is in a form selected from: press-to-close, hook-to-hook, slider, double track, triple track, slider, tamper, and evident.

16. The resealable bag of any one of claims 1-15, being a stand-up bag.

17. The resealable bag of any one of claims 1-16, wherein the high-WVTR layer comprises two or more sub-layers.

18. The resealable bag of any one of claims 1-17, wherein the polyamide of the high- WVTR layer comprises polycaprolactam (PA6).

19. The resealable bag of any one of claims 3-18, wherein the sealing layer has a sealing temperature of less than 200 °C.

20. The resealable bag of any one of claims 3-19, wherein the copolymer comprises a copolymer of polyamide.

21. The resealable bag of claim 20, wherein the copolymer of polyamide is selected from PA6 / 66, PA6 / 12, and PA66 / 69 / 610 / 61.

22. The resealable bag of any one of claims 3-21, wherein the copolymer comprises a copolymer of polystyrene.

23. The resealable bag of claim 22, wherein the copolymer of polystyrene is a copolymer comprising monomer units selected from: styrene butadiene styrene (SBS), styrene butadiene (SB), styrene ethylene butylene styrene (SEBS), styrene ethylene propylene styrene (SEPS), and styrene isoprene styrene (SIS).

24. The resealable bag of claim 23, wherein the copolymer comprises a SBS copolymer.

25. The resealable bag of any one of claims 3-20, wherein the blend of polymers comprises two or more polymers selected from polycaprolactam (PA6), polyhexamethylene adipamide (PA66), polydodecanolactam (PA12), polyhexamethylene azelaamide (PA69), hexamethylene sebacamide (PA610), poly(ll-aminoundecanoamide) (PA11), poly(hexamethylene dodecanoamide (PA6 / 12), PA6 / 66, PA6 / 12, and PA66 / 69 / 610 / 61.

26. The resealable bag of claim 25, wherein the two or more polymers comprise polymers PA6 / 66 and PA66 / 69 / 610 / 61.

27. The resealable bag of any one of claims 1-26, further comprising an additional layer adhered to a second surface of the high-WVTR layer.

28. A process of producing the resealable bag of any one of claims 1-27, comprising affixation of the resealable closure element to the multilayer film by heating an assembly of said multilayer film and resealable closure element at a temperature of between 145-250 °C.

29. The process of claim 28, wherein during the affixation, steps of a cross seal, a crush seal, and / or a skirt seal are performed at a heating temperature of between 145-250 °C.

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