Barrier film for packaging material and packaging material

Abstract

A barrier film (1) for a paper-based or paperboard-based packaging material comprises an MFC layer (2) having a grammage in the range of 20-100 g / m2 and a density higher than 650 kg / m3. The barrier film further comprises a dispersion coated primer layer (3, 9) of PHA coated on at least one side of the MFC layer, wherein the primer layer has a coating weight of 0.5-12 g / m2; the primer layer (3, 9) comprises a PHA type selected from the group consisting of PHB, PHBV, PHBH, P (3HB4HB), other copolymers of PHB, other homopolymers such as PHO, PHH, P3HP, and combinations thereof; and a thin vacuum deposited layer (4) coated on the first primer layer (3), the vacuum deposited layer having a thickness of 20-500 nm, the vacuum deposited layer comprising a material selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide.

Description

Technical Field

[0001] The present invention relates to a barrier film for paper-based or paperboard-based packaging materials, the barrier film comprising a microfibrillated cellulose layer, an MFC layer, having a first side and a second side, having a molecular weight of 20-100, preferably 20-50 g / m 2 Weights in the range of 650 kg / m 3 density.

[0002] The invention further relates to a paper-based or paperboard-based packaging material comprising a paper or paperboard substrate having a first side, the so-called printed side, and a second side facing away from the first side. Background Art

[0003] Packaging materials for food and liquids, including aseptic packaging in ambient distribution, frozen distribution or hot-fill products, play an important role in protecting the contents of the package. The packaging should not only extend the shelf life of the contents of the package, but also provide a laminate or packaging structure that can be reused and recycled.

[0004] Fiber-based materials represent a renewable resource and a sustainable alternative to fossil-based or plastic-based packaging. Fiber-based substrates such as paper or paperboard are typically extruded or dispersion coated and / or laminated with thin polymer layers to provide barrier properties to provide other functions such as sealing properties.

[0005] For more demanding applications, aluminum foil has been used in laminates to provide barrier properties against particularly aroma, light, and water vapor and gases.

[0006] In order to provide more sustainable solutions to the market, it is necessary to find aluminum foil-free solutions as well as laminate structures that are more sustainable in terms of recycling, reuse and / or compostability.

[0007] One solution disclosed in the prior art presents the use of paper-based solutions, in particular high-density paper grades such as greaseproof paper or parchment paper, for the carrier substrate of the vacuum-deposited organic or inorganic material.

[0008] These barrier papers are subsequently laminated to paperboard using a tie layer. A typical structure is PE / board / tie layer / barrier paper / metallized layer / PE. In some cases, the tie layer (PE) has been replaced by a water-soluble polymer layer such as a polysaccharide or polyvinyl alcohol. Another laminate structure is a barrier paper with, for example, a PVOH coating or its modified analogs or formulations before vacuum coating or metallization.

[0009] One problem is that when PVOH is used as a pre-coat or tie layer, the risk of delamination can be increased when relatively high humidity is experienced or if moisture diffusion occurs, such as in sterilization, if the PVOH is allowed to dissolve. Another problem is that upon composting of the above-mentioned structures, metals from the metallized layer leach into the soil and over time can cause serious environmental problems.

[0010] Purpose of the Invention

[0011] It is an object of the present invention to provide a barrier film which has good barrier properties and which is recyclable and reusable.

[0012] Another object is to provide retortable barrier films and laminates, with respect to which recyclability, and in particular pre- and post-consumer recyclability, is improved.

[0013] Yet another object is to provide a barrier film which solves or at least reduces the above mentioned problems. Summary of the invention

[0014] According to the present invention, the barrier film of the present invention is characterized in that the film further comprises

[0015] - a primer layer coated with a dispersion of PHA coated on at least one side of the MFC layer, wherein the primer layer has a PHA dispersion of 0.5-12 g / m 2 , preferably 1-8 g / m 2 The primer layer comprises a PHA type selected from the group consisting of PHB, PHBV, PHBH, P(3HB4HB), other copolymers of PHB, other homopolymers such as PHO, PHH, P3HP, and combinations thereof; and

[0016] - a thin vacuum deposited layer coated on the first primer layer, the vacuum deposited layer having a thickness of 20-500 nm, preferably 20-200 nm, the vacuum deposited layer comprising a material selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide.

[0017] The paper-based or paperboard-based packaging material is characterized in that it further comprises:

[0018] - a PHA adhesive layer coated on the second side of the substrate; and

[0019] - The barrier film as mentioned above, wherein the barrier film is connected to the substrate via an adhesive layer.

[0020] definition

[0021] Microfibrillated cellulose (MFC)

[0022] Microfibrillated cellulose (MFC) in the context of the present patent application shall mean cellulose particles, fibers or fibrils having a width or diameter from 4 nm to 1000 nm.

[0023] There are various methods to make MFC, such as single or multiple pass refining, pre-hydrolysis followed by refining or high shear decomposition or release of fibrils. One or more pretreatment steps are usually required to make MFC production energy-efficient and sustainable at the same time. Therefore, the cellulose fibers of the pulp used in the production of MFC can be natural or enzymatic or chemically pretreated, for example to reduce the amount of hemicellulose or lignin. Cellulose fibers can be chemically modified before fibrillation, wherein the cellulose molecules contain (or more) functional groups different from those found in the original cellulose. Such groups include carboxymethyl (CMC), aldehydes and / or carboxyl groups (cellulose obtained by N-oxyl-mediated oxidation, such as "TEMPO"), or quaternary ammonium (cationic cellulose) and the like. After modification or oxidation in one of the methods described above, it is easier to decompose the fibers into MFC.

[0024] Preferred grades that can be used are refined cellulose fiber compositions, wherein the refined cellulose fiber composition has a Schopper-Riegler (SR) value determined by standard ISO 5267-1 in the range of >80 and wherein the refined cellulose fiber composition has a content of fibers having a length >0.2 mm of at least 12 million fibers / g, based on dry weight.

[0025] MFC can be produced from wood cellulose fibers, both hardwood and softwood fibers. It can also be made from microbial sources, agricultural fibers such as wheat straw pulp, bamboo, bagasse or other non-wood fiber sources. It can be made from pulp including pulp from virgin fibers such as mechanical, chemical and / or thermomechanical pulp. It can also be made from broke or recycled substrates.

[0026] Thin barrier substrates made from cellulose, such as barriers comprising MFC or, for example, highly refined pulp, can be effective barrier materials in packaging or in various laminate structures.

[0027] Polyhydroxyalkanoates (PHA)

[0028] In the context of this patent application, PHA or polyhydroxyalkanoate shall refer to a family of biopolyesters with a variety of structures, and it is synthesized by a wide range of natural and genetically engineered bacteria and genetically engineered plant crops. PHA can be synthesized by 30% of bacteria living in the soil in a wide range of environmental conditions and media. Bacteria produce PHA by fermentation of sugars or lipids, where the purpose is to store carbon and energy. Examples of strains that can produce PHA include Alcaligenes eutrophus, Alcaligenes latus, Azotobacter, Aeromonas, Comamonas, Pseudomonads, and other genetically engineered organisms such as genetically engineered microorganisms like Pseudomonas, Ralstonia, and Escherichia coli. Typically, PHA is formed by enzymatic polymerization of one or more monomer units inside living bacteria or plant cells. More than 100 different types of monomers have been identified and incorporated into PHA polymers, including 3-hydroxybutyric acid and 3-hydroxyvaleric acid. PHAs can be classified into homopolymers such as the well-known polyhydroxybutyrate (PHB), or copolymers like poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Additionally, they are further classified into short chain length (SCL), medium chain length (MCL) or long chain length (LCL) PHAs based on the size of the carbon chain. Because they constitute a broad family of biodegradable polymers, PHAs exhibit very versatile properties that can benefit many different industrial applications including cosmetics, biopharmaceuticals, and packaging. DETAILED DESCRIPTION

[0029] Hereinafter, the present invention will refer to Figure 1-6 Further description. Please note that Figure 1-6 The drawings in the drawings are schematic and not to scale.

[0030] Figure 1 A first embodiment of a barrier film is shown.

[0031] Figure 2 A second embodiment of a barrier film is shown.

[0032] Figure 3 A third embodiment of a barrier film is shown.

[0033] Figure 4 A first embodiment of a paper-based or paperboard-based packaging material comprising a barrier film is shown.

[0034] Figure 5A second embodiment of a paper-based or paperboard-based packaging material comprising a barrier film is shown.

[0035] Figure 6 A third embodiment of a paper-based or paperboard-based packaging material comprising a barrier film is shown.

[0036] Barrier Film

[0037] The barrier film 1 for a paper-based or paperboard-based packaging material will be described in more detail.

[0038] MFC Layer

[0039] The barrier film 1 comprises a microfibrillated cellulose layer 2 (MFC layer). The MFC layer 2 has a first side 2a and a second side 2b facing away from the first side 2a. The MFC layer 2 has a molecular weight of 20-100, preferably 20-50 g / m 2 The grammage is in the range of 650-1400 kg / m2 as determined by ISO 534. 3 The density of the MFC layer of the barrier film of the present invention may be unmodified MFC or chemically modified MFC, or a mixture thereof. The MFC layer may further contain a filler. The MFC layer contains at least 50%, such as 60-100% or 70-98%, of MFC, based on the total organic content determined by the residue of burning of the cellulosic material according to ISO 1762:2015.

[0040] In a preferred embodiment, at least the first side 2a of the MFC layer 2 has a surface roughness Parker Print-Surf (PPS) in the range of 0.5-5.5 μm, preferably 0.8-5 μm, measured according to ISO 8791-4 with a clamping pressure of 1.0 MPa.

[0041] Preferably, the MFC layer 2 has a thickness of less than 50 g / m 2 , preferably less than 45 g / m 2 , more preferably 10-40 g / m 2 , and most preferably 15-35 g / m 2 The water absorption value COBB 60 is determined according to SCAN-P 12:64.

[0042] The air resistance of the MFC layer 2 measured by Gurley-Hill ISO 5636-5:2013 is higher than 5000 s / 100 ml, preferably higher than 20000 s / 100 ml, and most preferably 30000-42300 s / 100 ml. 42 300 s / 100 ml is the maximum value for the device (Gurley-Hill).

[0043] Furthermore, the MFC contains 0-50% of unrefined or lightly refined fibers such that the hardwood or softwood fibers have a Schopper-Riegler (SR) value between 12-50, preferably 20-45. This part may be important for ensuring mechanical strength during dispersion coating of PHA (see below). Alternatively, the MFC layer may simply consist of highly refined cellulose - so-called coarse MFC grades, which are easier to dehydrate than conventional fine MFC grades. This grade provides surprisingly good barrier in combination with PHA coatings.

[0044] The MFC layer can be a free-standing film made by papermaking techniques or by casting on a non-porous substrate.

[0045] One option is to deposit the MFC layer on the fibrous web, such as by the wet-on-wet principle, which forms the MFC layer on a fiber-based base substrate.

[0046] PHA primer layer

[0047] The barrier film 1 further comprises at least one PHA dispersion coated primer layer 3 , 9 . Figure 1 A first embodiment of a barrier film is disclosed, wherein a first side 2a of the MFC layer is coated with a first primer layer 3 . Figure 2 A preferred second embodiment of the barrier film 1 is disclosed and Figure 3 A preferred third embodiment of the barrier film 1 is disclosed, wherein the first side 2a of the MFC layer 2 is coated with a first primer layer 3 and the second side 2b of the MFC layer 2 is coated with a second primer layer 9. The primer layers 3, 9 have a thickness of 0.5-12 g / m 2 , preferably 1-8g / m 2 coating weight.

[0048] The PHA dispersion coated MFC layer should also be pinhole free.

[0049] Preferably the dispersion-coated MFC layer, i.e. the MFC layer and the dispersion-coated PHA primer coating, contains less than 10 pinholes / m 2 , preferably less than 8 pinholes / m 2 , and more preferably less than 2 pinholes / m 2 , which is measured according to standard EN13676:2001.

[0050] The primer layer 3, 9 comprises a PHA type selected from the group consisting of PHB, PHBV, PHBH, P(3HB4HB), other copolymers of PHB, other homopolymers such as PHO, PHH, P3HP, and combinations thereof.

[0051] The PHA primer layer 3, 9 is thermally stable, i.e. it has a relatively high melting temperature (Tm). The melting temperature (Tm) measured according to ISO 11357-3:2018 is in the range of 50-180°C, preferably 60-150°C, and most preferably 100-140°C.

[0052] In addition, the copolymer of PHB contains 0-40 mol%, preferably 2-30 mol%, more preferably 5-25 mol% of specific functional groups (e.g., valerate, hexanoate) or changes in the main chain (e.g., replacing 3HB and 4HB) to achieve flexibility. However, homopolymers other than PHB are essentially flexible.

[0053] The PHA dispersion layers 3, 9 contain stabilizers (e.g., PVOH, EVOH, PVAc, cellulose derivatives, polysaccharides), fillers (e.g., clay, calcium carbonate, talc, kaolinite, montmorillonite, bentonite, silica, chitin, titanium dioxide, nanoclay, nanocellulose, or mixtures thereof), nucleating agents (e.g., talc, mica, boron nitride, crystalline nanocellulose, sodium benzoate, calcium carbonate, silica, ionomers, clay, diacetal, titanium dioxide, dibenzylidene sorbitol, benzophenone, diacetal benzoate, lithium benzoate, sodium benzoate, potassium benzoate, thymine, sodium organic phosphate).

[0054] The PHA dispersion layer 3, 9 may further comprise:

[0055] Surfactants: Cationic, anionic, nonionic, and amphoteric surfactants - for example, polysorbates, aromatic polyethylene oxides, sorbitol derivatives, block copolymers of poly(ethylene oxide) and poly(propylene oxide), poly(glycol ethers), alkyl sulfates, alkyl phosphates, stearate saponins.

[0056] Foam suppressants: polyether siloxane, silicone, stearate, glycol, vegetable oil.

[0057] Plasticizers: glycerol, sorbitol, mannitol, xylitol, ethylene glycol, fatty acids, monosaccharides, urea, vegetable oils.

[0058] The solids content of the PHA dispersion is >20 wt%, preferably >35 wt%, and most preferably 45-60 wt%.

[0059] According to TAPPI test method T 701 pm-01, the dispersion has a 2 Below, preferably below 140g / m 2 , and most preferably 20-130 g / m 2 Water retention value.

[0060] The content of PHA in the primer layer 3, 9 is at least 40%.

[0061] The basecoat layer 3 , 9 can contain up to 40% by weight of pigments / fillers, which in turn have a great influence, namely a better barrier effect on UV transparency and light transmission.

[0062] After the first PHA primer layer 3 has been coated on the first side 2a of the MFC layer 2, the first side 2a has a surface roughness Parker Print-Surf (PPS) in the range of 0.5-4 μm measured according to ISO 8791-4 with a clamping pressure of 1.0 MPa.

[0063] The primer layer 3, 9 also provides a barrier effect, especially an improved KIT value, which is surprising. It also reduces MOAH / MOSH migration and enables the use of recycled fibers in the paperboard.

[0064] The primer layer 3, 9 can be applied in a single layer, a double layer or a triple layer. After each application of the primer layer 3, 9, the primer layer 3, 9 is dried. During drying, the surface temperature of the substrate reaches a maximum temperature of above 80° C., preferably above 85° C., and most preferably above 88° C. The moisture content after drying the substrate is below 6% by weight, preferably 1-5% by weight.

[0065] PHA purity (before additives) is >98 wt%, preferably >99 wt%, most preferably >99.8 wt% (impurities are typically fragments of bacterial cell walls, which may include proteins).

[0066] The PTS recyclability for barrier films is high, ie provides a reject rate of less than 20% when manufactured according to the PTS repulpability standard RH 021-97.

[0067] The surface energy of the PHA primer layer 3, 9 according to ISO 19403-2 when applied (and dried) on the MFC layer 2 is 30-70 mN / m, preferably 35-70 mN / m, and most preferably 40-65 mN / m.

[0068] Thin vacuum deposited layers

[0069] The barrier substrate 1 further comprises a thin vacuum deposited layer 4, which is obtained by vacuum deposition, i.e. deposition of a metal or non-metal or its oxide. The vacuum deposited layer 4 is coated on the first primer layer 3. The vacuum deposited layer 4 on the first primer layer 3 has a thickness of 20-500 nm, preferably 20-200 nm.

[0070] The vacuum deposited layer 4 comprises a material selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide.

[0071] After vacuum coating, the opposite side of the MFC layer 2 may need to be re-wetted to adjust the moisture content to 1-5 wt%.

[0072] In an alternative embodiment, the outer surface of the first primer coating layer may be treated with corona, plasma or flame before vacuum deposition of the surface layer 4. The mentioned treatments further pre-activate the primer coating, thereby providing better properties of the entire structure.

[0073] Examples of techniques for applying thin vacuum deposited layers include plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), conventional metallization, CCVD or PECVD, or methods known in the art in addition thereto. In certain embodiments, the aluminum oxide and / or silicon dioxide layer is deposited via CCVD or PECVD in an open atmosphere. Other methods are sputtering, chemical vapor deposition (CVD), combustion chemical vapor deposition (CCVD), physical vapor deposition (PVD), plasma enhanced chemical vapor deposition (PECVD), vacuum deposition, flame deposition, and flame hydrolysis deposition.

[0074] PHA protective layer

[0075] Figure 3 A preferred third embodiment of the barrier film is disclosed, wherein the vacuum deposited layer 4 is protected by a PHA protective layer 8. The protective layer has a PHA content of 0.5-20 g / m 2 coating weight.

[0076] The type of PHA in the protective layer 8 is selected from PHB, PHBV, PHBH, P(3HB4HB), and combinations thereof.

[0077] The protective layer has a melting temperature (Tm) in the range of 100-180°C, preferably 120-170°C, and most preferably 130-160°C.

[0078] The content of PHA in the protective layer 8 is at least 70%.

[0079] The protective layer 8 may be applied by extrusion coating, lamination or dispersion coating in one or more steps.

[0080] Barrier Film 1 has an oxygen transmission rate (OTR) of <10 mL / m at 23°C and 50% RH according to ASTM F 1927-20. 2 / day, preferably <5 mL / m 2 / day, and most preferably <2 mL / m 2 / sky.

[0081] Barrier Film 1 has an oxygen transmission rate (OTR) of <30 mL / m at 38°C and 90% RH according to ASTM F1927-20. 2 / day, preferably <20 mL / m 2 / day, and most preferably <10 mL / m 2 / sky.

[0082] Barrier Film 1 has a water vapor transmission rate (WVTR): <5 g / m2 at 23°C and 50% RH according to ASTM F1249-20. 2 / day, preferably <2 g / m 2 / day, and most preferably <1 g / m 2 / sky.

[0083] Barrier Film 1 has a water vapor transmission rate (WVTR): <20 g / m2 at 38°C and 90% RH according to ASTM F1249-20. 2 / day, preferably <15 g / m 2 / day, and most preferably <10 g / m 2 / sky.

[0084] Packaging Materials

[0085] The present invention also encompasses a packaging material 5 comprising a paper or paperboard substrate 6 and the barrier film 1 according to the present invention.

[0086] First embodiment

[0087] Figure 4 A first embodiment of the packaging material 5 is disclosed.

[0088] The packaging material 5 comprises a paper-based or paperboard-based substrate 6. The substrate 6 has a first side 6a, the so-called printed side, and a second side 6b facing away from the first side 6a. A layer of PHA adhesive 7 is deposited on the second side 6b of the substrate 6.

[0089] The packaging material further comprises a barrier film 1 , wherein only the first side 2 a of the MFC layer 2 is coated with a primer layer 3 .

[0090] The barrier film 1 is connected to the substrate 6 via the adhesive layer 7. In addition, the adhesive layer 7 may also protect the vacuum deposited layer 4. The adhesive layer activates the barrier film 1 and the surface on the substrate 6 and generates hydrogen bonds / covalent bonds / van der Waals bonds between the layers.

[0091] Figure 4 A preferred embodiment is disclosed, wherein the second side 2a of the MFC layer 2 faces the substrate 6 .

[0092] The second side 2b of the MFC layer 2 is preferably sealed by an inner liquid barrier layer 10, and the first side 6a of the substrate 6 is preferably sealed by an outer decorative layer 11. These layers 10, 11 can be single layers or multiple layers. For example, each layer 10, 11 can be two coextruded PHA layers.

[0093] In an alternative embodiment (not shown in the drawings), the second side 2 b of the MFC layer 2 faces the substrate 6 .

[0094] Second embodiment

[0095] Figure 5 A second embodiment of the packaging material 5 is disclosed.

[0096] The packaging material comprises a paper-based or paperboard-based substrate 6. The substrate 6 has a first side 6a, the so-called printed side, and a second side 6b facing away from the first side 6a. A layer of PHA adhesive 7 is deposited on the second side 6b of the substrate 6.

[0097] The packaging material further comprises the barrier film 1 of the present invention, wherein the first side 2a of the MFC layer 2 is coated with the first primer layer 3 and the second side 2b of the MFC layer 2 is coated with the second primer layer 9 .

[0098] The barrier film 1 is connected to the substrate 6 via the adhesive layer 7. Furthermore, the adhesive layer 7 may also protect the vacuum deposited layer 4.

[0099] Figure 5 A preferred embodiment is disclosed, wherein the second side 2a of the MFC layer 2 faces the substrate 6 .

[0100] The second primer layer 9 is preferably sealed by an inner liquid barrier layer 10, and the first side 6a of the substrate 6 is preferably sealed by an outer decorative layer 11. These layers 10, 11 can be single layers or multiple layers. For example, each layer 10, 11 can be two coextruded PHA layers.

[0101] In an alternative embodiment (not shown in the drawings), the second side 2 b of the MFC layer 2 faces the substrate 6 .

[0102] Third embodiment

[0103] Figure 6 A third embodiment of the packaging material 5 is disclosed.

[0104] The packaging material comprises a paper-based or paperboard-based substrate 6. The substrate 6 has a first side 6a, the so-called printed side, and a second side 6b facing away from the first side 6a. A layer of PHA adhesive 7 is deposited on the second side 6b of the substrate 6.

[0105] The packaging material further comprises a barrier film 1, wherein a first side 2a of the MFC layer 2 is coated with a first primer layer 3, and a second side 2b of the MFC layer 2 is coated with a second primer layer 9. The first primer layer 3 is coated with a vacuum deposited layer 4.

[0106] The barrier film 1 is connected to the second side 6b of the substrate 6 via an adhesive layer 7. Furthermore, the adhesive layer 7 may also protect the vacuum deposited layer 4.

[0107] Figure 6 A preferred embodiment is disclosed, wherein the second side 2a of the MFC layer 2 faces the substrate 6 .

[0108] The second side 2b of the MFC layer 2 is preferably sealed by an inner liquid barrier layer 10, and the first side 6a of the substrate 6 is preferably sealed by an outer decorative layer 11. These layers 10, 11 may be single or multilayer, for example, each layer 10, 11 may be two coextruded PHA layers.

[0109] In an alternative embodiment (not shown in the drawings), the second side 2 b of the MFC layer 2 faces the substrate 6 .

[0110] A great benefit of using the barrier film of the present invention, compared to barrier films using a water soluble tie layer, is that it is retortable.

[0111] Another benefit of the present invention is that the broke from the primer coated MFC layer, i.e., MFC layer 2 and PHA dispersion coated layers 3, 9 can be broken down in an amount of 0-60 wt% and reused when making a new MFC layer 2. Such an MFC layer 2 may contain 0-50 wt% uncoated broke (without PHA dispersion primer), 0-50 wt% coated broke (with PHA dispersion primer), 0-50 wt% unrefined or lightly refined pulp, and >50 wt% MFC or highly refined pulp.

[0112] Example 1 of ingredient composition:

[0113] 10 wt% uncoated broke

[0114] 10 wt% coated broke

[0115] 10 wt% pulp, refined to Schopper-Riegler, SR 25

[0116] 70 wt% MFC pulp, refined to SR 92

[0117] Example 2 of ingredient composition:

[0118] 15 wt% coated broke

[0119] 5 wt% pulp, refined to SR 25

[0120] 80 wt% MFC pulp, refined to SR 92

[0121] The present invention discloses a packaging material designed for aseptic packaging and for use in a shelf life extension heat treatment at elevated temperatures, such as using steam as a heat medium. Examples of such a shelf life extension heat treatment are hot filling followed by pasteurization or retorting and steam autoclaving.

[0122] The treatment is typically carried out at a temperature above 80° C. The heat treatment can, for example, co-sterilize the package and the package contents, such as a food product.

[0123] The heat treatment may be performed under overpressure and at a temperature above 100°C, such as above 110°C or above 121°C, such as 121-140°C.

[0124] The alternative heat treatment method for such sterilization cooking or pressure sterilization treatment is the so-called "hot filling under pasteurization" treatment, which, in addition to the aseptic filling of the preheated and thus partially sterilized food product, also keeps the filled and sealed package at an elevated temperature such as a continuous extended heat treatment at a temperature of from 80 to 100°C. The package is kept at an elevated temperature by pushing the package through a hot sterilization tunnel, which is divided into several treatment zones, including a warm zone, a heat treatment zone, and a cooling zone. The warm zone and the heat treatment zone can be treated with dry heat, i.e., by hot air in the absence of steam, or with steam and / or with water sprayed or flushed on the package. Cooling is usually completed by flushing the package with cooling water. Most commonly, water is used to adjust (warm and cool) the hot filling pasteurization temperature.

[0125] In the foregoing, the present invention has been described with respect to some specific embodiments. However, it will be appreciated by those skilled in the art that other embodiments and variations are possible within the scope of the following claims.

Claims

1. A barrier film (1) for paper-based or paperboard-based packaging material, the barrier film comprising a microfibrillated cellulose layer, an MFC layer, (2), the MFC layer having a first side (2a) and a second side (2b), having a molecular weight of 20-100, preferably 20-50 g / m 2 Weights in the range of 650 kg / m 3 The density is characterized by The barrier film (1) further comprises: - a primer layer (3, 9) coated with a dispersion of PHA coated on at least one side of the MFC layer, wherein the primer layer (3, 9) has a PHA dispersion of 0.5-12 g / m 2 , preferably 1-8 g / m 2 The primer layer (3, 9) comprises a PHA type selected from the group consisting of PHB, PHBV, PHBH, P(3HB4HB), other copolymers of PHB, other homopolymers such as PHO, PHH, P3HP, and combinations thereof; and - a thin vacuum deposited layer (4) coated on the first primer layer (3), the vacuum deposited layer (4) having a thickness of 20-500 nm, preferably 20-200 nm, the vacuum deposited layer comprising a material selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide.

2. The barrier film (1) according to claim 1, wherein the first side (2a) of the MFC layer (2) is coated with a first PHA primer layer (3).

3. The barrier film (1) according to claim 1, wherein the first side (2a) of the MFC layer (2) is coated with a first PHA primer layer (3), and the second side of the MFC layer (2) is coated with a second PHA primer layer (9).

4. The barrier film (1) according to any one of the preceding claims, wherein the barrier film (1) further comprises a PHA coating protective layer (8) on the vacuum deposited layer (4), the protective layer (8) having a PHA coating thickness of 0.5-20 g / m 2 The coating weight is 200 g / cm2 and the PHA type is selected from PHB, PHBV, PHBH, P(3HB4HB), and combinations thereof.

5. The barrier film (1) according to any of the preceding claims, wherein at least one side of the MFC layer (2) has a surface roughness Parker Print-Surf (PPS) in the range of 0.5-6 µm with a clamping pressure of 1.0 MPa according to ISO8791-4.

6. The barrier film (1) according to any one of the preceding claims, wherein the PHA primer layer (3, 9) has a melting temperature (Tm) measured according to ISO 11357-3:2018 in the range of 50-180°C, preferably 60-150°C and most preferably 100-140°C.

7. The barrier film (1) according to any of the preceding claims, wherein the PHA solids content in the dispersion is >20 wt%, preferably >35 wt%, most preferably 45-60 wt%.

8. The barrier film (1) according to any one of the preceding claims, wherein the PHA content in the primer layer (2) is at least 40%.

9. The barrier film (1) according to any one of the preceding claims, wherein the MFC layer has a molecular weight of less than 60 g / m 2 Water absorption value (COBB 60, determined according to SCAN-P 12:64).

10. The barrier film according to any one of the preceding claims, wherein the barrier film has a relative humidity of <10, preferably <5 and most preferably <2 mL / m 2 at 23°C and 50% RH according to ASTM F1927-20. 2 / day oxygen transmission rate (OTR).

11. The barrier film according to any one of the preceding claims, wherein the barrier film has a relative humidity of <30, preferably <20 and most preferably <10 mL / m 2 at 38°C and 90% RH according to ASTM F1927-20. 2 / day oxygen transmission rate (OTR).

12. The barrier film 1 according to any one of the preceding claims, wherein the barrier film has a water vapor transmission rate (WVTR) of < 5 g / m at 23°C and 50% RH according to ASTM F-1249-20. 2 / day, preferably <2 g / m 2 / day and most preferably <1 g / m 2 / sky.

13. The barrier film 1 according to any one of the preceding claims, wherein the barrier film has a water vapor transmission rate (WVTR) of < 20 g / m at 38°C and 90% RH according to ASTM F-1249-20. 2 / day, preferably <15 g / m 2 / day and most preferably <10 g / m 2 / sky.

14. A paper-based or paperboard-based packaging material (5) comprising a paper or paperboard substrate (6) having a first side (6a), the so-called printed side, and a second side (6b) facing away from the first side (6a), characterised in that The packaging material further comprises: - a PHA adhesive layer (7) coated on the second side (6b) of the substrate (6); and - The barrier film (1) according to any one of claims 1 to 13, wherein the barrier film (1) is connected to the substrate (6) via an adhesive layer (7).

15. The paper-based or paperboard-based packaging material (5) according to claim 14, wherein the first side (2a) of the MFC layer (2) faces the paper or paperboard substrate (6).

16. The paper-based or paperboard-based packaging material (5) according to claim 14, wherein the second side (2b) of the MFC layer (2) faces the paper or paperboard substrate (6).

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