Barrier film for packaging materials, and packaging materials

Abstract

A barrier film (1) for a packaging material based on paper or cardboard, the barrier film having a basis weight in the range of 20 to 100 g / m 2 and a density higher than 650 kg / m 3 and comprising an MFC layer (2). The barrier film further comprises a primer layer (3, 9) coated with a PHA dispersion and having a coating weight of 0.5 to 12 g / m 2 , the primer layer (3, 9) being coated on at least one side of the MFC layer and containing 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 vacuum-deposited thin layer (4) having a thickness of 20 to 500 nm coated on the first primer layer (3), the vacuum-deposited thin layer containing 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 a packaging material based on paper or cardboard, the barrier film comprising a microfibrillated cellulose layer (MFC layer) having a first side and a second side, the MFC layer having a basis weight in the range of 20 to 100 g / m 2 preferably in the range of 20 to 50 g / m 2 and having a density higher than 650 kg / m 3 .

[0002] The present invention also relates to a paper or cardboard-based packaging material comprising a paper or cardboard substrate having a first side (so-called printing side) and a second side opposite to the first side.

[0003] Background Art - Problems Packaging materials for food and liquids (including aseptic containers for ambient distribution, chilled distribution, or hot filled products) play an important role in protecting the packaged contents. The packaging should not only extend the shelf life of the packaged contents but also provide a laminate structure or packaging structure that enables reuse and recycling.

[0004] Fiber-based materials are renewable resources and sustainable alternatives to fossil fuel-based or plastic-based packaging. Fiber-based substrates (such as paper or cardboard) are typically extrusion-coated or coated with a dispersion and / or laminated with a thin polymer layer to provide barrier properties and other functions (such as sealing properties).

[0005] In more demanding applications, aluminum foil is used in the laminate, especially to provide barrier properties against aroma, light, and water vapor and gas.

[0006] In order to provide more sustainable solutions to the market, it is necessary to find solutions that do not use aluminum foil, but more sustainable laminate structures are also needed in terms of recycling, reuse, and / or compostability.

[0007] In one technical solution disclosed in the prior art, for carrier substrates of vacuum-evaporated organic or inorganic materials, solutions based on paper (especially high-density paper grades such as greaseproof paper or parchment paper) are proposed to be used.

[0008] These barrier papers are then laminated to cardboard using an adhesive layer. A typical structure is PE / cardboard / adhesive layer / barrier paper / metallization layer / PE. In some cases, the adhesive layer (PE) has been replaced by a water-soluble polymer layer (such as polysaccharides or polyvinyl alcohol). Another lamination structure is a barrier paper with, for example, a PVOH coating or a modified analogue or formulation thereof before vacuum coating or metallization.

[0009] When using PVOH as a pre-coating or adhesive layer, there is a problem in that the risk of delamination may increase when exposed to high relative humidity or when moisture diffusion occurs, such as during sterilization that enables solubilization of PVOH. Another problem is that when composting the aforementioned structure, metals from the metallization layer may leach into the soil, which may cause serious environmental problems over time.

[0010] Object of the Invention The object of the present invention is to provide a barrier film having good barrier properties and being recyclable and reusable.

[0011] Another object is to provide a retortable barrier film and laminate with improved recyclability, especially recyclability before and after the consumer.

[0012] Yet another object is to provide a barrier film that solves or at least reduces the above problems.

[0013] Summary of the Invention According to the present invention, the barrier film of the present invention further comprises · a primer layer coated with a dispersion of PHA and coated on at least one side of the MFC layer, with a coating weight of 0.5 to 12 g / m 2 , preferably 1 to 8 g / m 2 and containing 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 · a vacuum-deposited thin layer with a thickness of 20 to 500 nm, preferably 20 to 200 nm, coated on the first primer layer and containing a material selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide and is provided with characterized by

[0014] The packaging material based on paper or cardboard further comprises · a PHA adhesive layer coated on the second side of the substrate, and · the aforementioned barrier film and is characterized in that the barrier film is attached to the substrate through the adhesive layer. characterized by

[0015] Definition Microfibrillated cellulose (MFC) Microfibrillated cellulose (MFC) shall refer to cellulose particles, fibers or fibrils with a width or diameter of 4 nm to 1000 nm in the context of this patent application.

[0016] There are various methods for producing MFC, and one example is single-pass or multi-pass refining, pre-hydrolysis followed by refining, or high-shear degradation, or fibrillation release. Usually, one or more pretreatment steps are required to produce MFC energy-efficiently and sustainably. Thus, the cellulose fibers of the pulp used in producing MFC may be natural or pretreated enzymatically or chemically (e.g., to reduce the amount of hemicellulose or lignin). The cellulose fibers may be chemically modified prior to fibrillation, where the cellulose molecules contain functional groups other than (or more than) those found in the original cellulose. Such groups include, among others, carboxymethyl (CM), aldehyde, and / or carboxyl groups (cellulose obtained by N-oxyl-mediated oxidation, e.g., "TEMPO"), or quaternary ammonium (cationic cellulose). After modification or oxidation by any of the above methods, it becomes easier to decompose the fibers into MFC.

[0017] A preferred grade that can be used is a refined cellulose fiber composition, and the refined cellulose fiber composition has a Schopper-Riegler (SR) value in the range of >80 as determined by ISO 5267-1, and the refined cellulose fiber composition has a content of fibers with a length >0.2 mm of at least 12 million fibers per gram based on the dry weight.

[0018] MFC can be produced from lignocellulose fibers, from either hardwood or softwood fibers. MFC can also be made from microbial sources, agricultural fibers (e.g., wheat straw pulp, bamboo, bagasse), or other non-wood fiber sources. This can be made from pulp (including pulp from virgin fibers), e.g., mechanical pulp, chemical pulp, and / or thermomechanical pulp. MFC can also be made from waste paper or recycled substrates.

[0019] Thin barrier substrates made from cellulose (e.g., MFC or a barrier containing, for example, highly refined pulp) can be efficient barrier materials in packaging or various laminate structures.

[0020] Polyhydroxyalkanoate (PHA) PHA or polyhydroxyalkanoate refers to a family of biopolyesters having various structures in the context of this patent application, which refers to a family of biopolyesters synthesized by a wide range of natural and genetically engineered bacteria and genetically engineered plant crops. PHA can be synthesized by 30% of the bacteria living in the soil under a wide range of environmental conditions and media. The bacteria produce PHA by fermenting sugars or lipids for the purpose of storing carbon and energy. Examples of bacterial strains capable of producing PHA include Alcaligenes eutrophus, Alcaligenes latus, Azotobacter, Aeromonas, Comamonas, Pseudomonads, and other genetically engineered organisms, such as genetically engineered microorganisms, such as Pseudomonas, Ralstonia, and Escherichia coll. PHA is generally formed by the enzymatic polymerization of one or more monomer units inside living bacteria or plant cells. More than 100 monomers have been identified and incorporated into PHA polymers (including 3-hydroxybutyric acid and 3-hydroxypentanoic acid). PHA can be classified into homopolymers (such as the well-known polyhydroxybutyrate (PHB)) or copolymers (such as poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)). Further, depending on the size of the carbon chain, PHA is further classified into short-chain length (SCL), medium-chain length (MCL), or long-chain length (LCL) PHA. Since PHA constitutes a wide family of biodegradable polymers, it exhibits highly versatile properties that can bring benefits to many different industrial applications (including, but not limited to, cosmetics, biomedicine, and packaging).

[0021] Hereinafter, the present invention will be further described with reference to FIGS. 1 to 6. Note that the drawings of FIGS. 1 to 6 are schematic views and not to scale.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0023] Barrier film The barrier film 1 for packaging materials based on paper or cardboard will be described in more detail below.

[0024] MFC layer The barrier film 1 includes a microfibrillated cellulose layer 2 (MFC layer). The MFC layer 2 has a first side 2a and a second side 2b opposite to the first side 2a. The MFC layer 2 has a basis weight in the range of 20 - 100 g / m 2 Preferably in the range of 20 - 50 g / m 2 And a density (determined by ISO 534) in the range of 650 - 1400 kg / m 3 The MFC of the MFC layer of the barrier film according to the present invention can 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% MFC, for example 60 - 100% or 70 - 98% MFC, based on the total organic content (determined by the ignition residue of the cellulose material in accordance with ISO 1762:2015).

[0025] 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 to 5.5 μm, preferably in the range of 0.8 to 5 μm, as measured at a clamping pressure of 1.0 MPa in accordance with ISO 8791-4.

[0026] Preferably, the MFC layer 2 has a water absorbency (determined in accordance with Cobb 60, SCAN-P 12:64) of less than 50 g / m 2 Lower, preferably less than 45 g / m 2 Lower, more preferably in the range of 10 to 40 g / m 2 Most preferably in the range of 15 to 35 g / m 2 is.

[0027] The air permeability 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 in the range of 30,000 to 42,300 s / 100 ml. 42,300 s / 100 ml is the maximum value for the apparatus (Gurley-Hill).

[0028] The MFC also contains 0 to 50% of unpurified fibers or moderately purified fibers, and the hardwood or softwood fibers have a Schopper-Riegler (SR) value between 12 and 50, preferably between 20 and 45. This ratio can be important for ensuring mechanical strength during the dispersion coating of PHA (see below). Alternatively, the MFC layer may simply be composed of highly purified cellulose, so-called coarse MFC grades (easier to dewater than conventional fine MFC grades). By combining this grade with a PHA coating, a surprisingly good barrier is obtained.

[0029] The MFC layer can be a self-supporting film made by papermaking techniques or a self-supporting film made using casting on a non-porous substrate.

[0030] One option is to deposit the MFC layer on the fiber web (e.g., by the wet-on-wet principle), whereby an MFC layer is formed on the fiber-based substrate.

[0031] PHA primer layer Barrier film 1 further comprises at least one PHA dispersion coating primer layer 3, 9. FIG. 1 discloses a first embodiment of the barrier film, wherein the first side 2a of the MFC layer is coated by the first primer layer 3. FIG. 2 discloses a preferred second embodiment, and FIG. 3 discloses a preferred third embodiment of the barrier film 1, wherein the first side 2a of the MFC layer 2 is coated by the first primer layer 3 and the second side 2b of the MFC layer 2 is coated by the second primer layer 9. The primer layers 3, 9 have a coating weight of 0.5 - 12 g / m 2 , preferably 1 - 8 g / m 2 .

[0032] The PHA dispersion-coated MFC layer is also preferably pinhole-free.

[0033] Preferably, the dispersion-coated MFC layer, i.e., the MFC layer and the dispersion-coated PHA primer coating, when measured in accordance with EN standard 13676:2001, has less than 10 pinholes / m 2 , preferably less than 8 pinholes / m 2 , more preferably less than 2 pinholes / m 2 .

[0034] The primer layers 3, 9 include PHA types selected from the group consisting of PHB, PHBV, PHBH, P(3HB4HB), other copolymers of PHB, other homopolymers (e.g., PHO, PHH, P3HP), and combinations thereof.

[0035] The PHA primer layers 3 and 9 are thermally stable, i.e., they have a relatively high melting point (Tm). The melting point (Tm) is in the range of 50 to 180 °C, preferably 60 to 150 °C, and most preferably 100 to 140 °C, measured in accordance with ISO 11357 3:2018.

[0036] Furthermore, the copolymer of PHB contains 0 to 40 mol%, preferably 2 to 30 mol%, more preferably 5 to 25 mol% of specific functional groups (e.g., valerate, hexanoate), or the backbone changes for flexibility (e.g., alternating 3HB and 4HB). In contrast, homopolymers other than PHB are essentially flexible.

[0037] The PHA dispersion layers 3 and 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), and nucleating agents (e.g., talc, mica, boron nitride, crystalline nanocellulose, sodium benzoate, calcium carbonate, silica, ionomer, clay, diacetal, titanium dioxide, dibenzylidene sorbitol, benzophenone, diacetal benzoate, lithium benzoate, sodium benzoate, potassium benzoate, thymine, sodium organic phosphate).

[0038] The PHA dispersion layers 3 and 9 may also include the following: · Surfactants: cationic, anionic, non-ionic, and amphoteric surfactants, such as polysorbate, aromatic polyethylene oxide, sorbitan derivatives, block copolymers of poly(ethylene oxide) and poly(propylene oxide), poly(glycol ether), alkyl sulfate, alkyl phosphate, stearate, saponin. · Antifoaming agents: polyether siloxane, silicone, stearate, glycol, vegetable oil. · Plasticizers: glycerol, sorbitol, mannitol, xylitol, ethylene glycol, fatty acids, monosaccharides, urea, vegetable oils.

[0039] The solid content of the PHA dispersion is > 20% by weight, preferably > 35% by weight, and most preferably 45 - 60% by weight.

[0040] In accordance with the TAPPI test method T 701 pm - 01, the water retention value of the dispersion is 150 g / m 2 less, preferably 140 g / m 2 less, and most preferably 20 - 130 g / m 2 is.

[0041] The PHA content in the primer layers 3, 9 is at least 40%.

[0042] The primer layers 3, 9 can contain up to 40% by weight of pigments / fillers, which results in a greater impact, i.e., a better blocking effect on UV permeability and light transmittance.

[0043] After the first PHA primer layer 3 is 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 when measured at a clamping pressure of 1.0 MPa in accordance with ISO 8791 4.

[0044] The primer layers 3, 9 also provide a barrier effect, and surprisingly, especially the KIT value is improved. The primer layer also reduces the migration of MOAH / MOSH, making it possible to use recycled fibers in the cardboard.

[0045] The primer layers 3 and 9 may be coated once, twice, or three times. After each coating layer, the primer layers 3 and 9 are dried. The surface temperature of the substrate during drying reaches a maximum temperature exceeding 80°C, preferably exceeding 85°C, and most preferably exceeding 88°C. The moisture content of the substrate after drying is less than 6% by weight, preferably 1 - 5% by weight.

[0046] The PHA purity (before addition of the additive) is >98% by weight, preferably >99% by weight, and most preferably >99.8% by weight (usually, the impurities are fragments of bacterial cell walls, and such fragments may contain proteins).

[0047] The PTS recyclability of the barrier film is high, and when manufactured in accordance with the PTS repulping standard RH 021 - 97, the reject rate is less than 20%.

[0048] The surface energy of the PHA primer layers 3 and 9, when applied (and dried) to the MFC layer 2, is 30 - 70 mN / m, preferably 35 - 70 mN / m, and most preferably 40 - 65 mN / m in accordance with ISO 19403 - 2.

[0049] Vacuum - deposited thin layer The barrier substrate 1 further comprises a vacuum - deposited thin layer 4, which is obtained by vacuum deposition, i.e., by deposition of a metal or non - metal or their oxides. 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.

[0050] The vacuum - deposited layer 4 is a material selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably including aluminum oxide.

[0051] After vacuum coating, the opposite side of the MFC layer 2 may need to be re - moisturized to adjust the moisture content to 1 - 5% by weight.

[0052] In an alternative embodiment, the outer surface of the first primer coating layer can be treated by corona, plasma or flame prior to the vacuum deposited surface layer 4. By the above treatment, the primer coating is further pre-activated, so that the performance of the whole structure is better.

[0053] Examples of techniques for applying a vacuum deposited thin layer are plasma enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), conventional metallization, CCVD or PECVD, or others known in the art. In a particular embodiment, a layer of alumina and / or silica is deposited in an open atmosphere via CCVD or PECVD. 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.

[0054] PHA protective layer FIG. 3 discloses a preferred third embodiment for the barrier film, in which the vacuum deposited layer 4 is protected by a PHA protective layer 8. The protective layer has a coating weight of 0.5 - 20 g / m 2 is.

[0055] The PHA type in the protective layer 8 is selected from the group consisting of PHB, PHBV, PHBH, P(3HB4HB), and combinations thereof.

[0056] The protective layer has a melting point (Tm) in the range of 100 - 180 °C, preferably 120 - 170 °C, most preferably 130 - 160 °C.

[0057] The PHA content in the protective layer 8 is at least 70%.

[0058] The protective layer 8 can be applied in one or several steps by any of extrusion coating, lamination or dispersion coating.

[0059] The barrier film 1 has an oxygen transmission rate (OTR) of < 10 mL / m 2 / day, preferably < 5 mL / m 2 / day, and most preferably < 2 mL / m 2 / day at 23°C and 50% RH in accordance with ASTM F1927-20.

[0060] The barrier film 1 has an oxygen transmission rate (OTR) of < 30 mL / m 2 / day, preferably < 20 mL / m 2 / day, and most preferably < 10 mL / m 2 / day at 38°C and 90% RH in accordance with ASTM F1927-20.

[0061] The barrier film 1 has a water vapor transmission rate (WVTR) of < 5 g / m 2 / day, preferably < 2 g / m 2 / day, and most preferably < 1 g / m 2 / day at 23°C and 50% RH in accordance with ASTM F1249-20.

[0062] The barrier film 1 has a water vapor transmission rate (WVTR) of < 20 g / m 2 / day, preferably < 15 g / m 2 / day, and most preferably < 10 g / m 2 / day at 38°C and 90% RH in accordance with ASTM F1249-20.

[0063] Packaging material The present invention also relates to a packaging material 5 comprising a base material 6 of paper or cardboard and the barrier film 1 according to the present invention.

[0064] First embodiment FIG. 4 discloses a first embodiment of the packaging material 5.

[0065] The packaging material 5 comprises a substrate 6 based on paper or cardboard. The substrate 6 has a first side 6a (so-called printing surface) and a second side 6b opposite to the first side 6a. A PHA adhesive layer 7 is deposited on the second side 6b of the substrate 6.

[0066] The packaging material further comprises a barrier film 1, and only the first side 2a of the MFC layer 2 is coated with a primer layer 3.

[0067] The barrier film 1 is attached to the substrate 6 via the adhesive layer 7. In addition, the adhesive layer 7 can also protect the vacuum-deposited layer 4. Due to the adhesive layer, the surface of the barrier film 1 and the substrate 6 are activated, and hydrogen / covalent bond / van der Waals bond is formed between these layers.

[0068] FIG. 4 discloses a preferred embodiment in which the second side 2a of the MFC layer 2 faces the substrate 6.

[0069] 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 either single-layer or multi-layer. For example, each of the layers 10, 11 can be two co-extruded PHA layers.

[0070] In an alternative embodiment (not shown), the second side 2b of the MFC layer 2 faces the substrate 6.

[0071] Second Embodiment FIG. 5 discloses a second embodiment of the packaging material 5.

[0072] The packaging material comprises a substrate 6 based on paper or cardboard. The substrate 6 has a first side 6a (so-called printing surface) and a second side 6b opposite to the first side 6a. A PHA adhesive layer 7 is deposited on the second side 6b of the substrate 6.

[0073] The packaging material further comprises the barrier film 1 according to 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.

[0074] The barrier film 1 is attached to the substrate 6 via the adhesive layer 7. In addition, the adhesive layer 7 can also protect the vacuum-deposited layer 4.

[0075] Fig. 5 discloses a preferred embodiment in which the second side 2a of the MFC layer 2 faces the substrate 6.

[0076] The second primer layer 9 is preferably sealed by the inner liquid barrier layer 10, and the first side 6a of the substrate 6 is preferably sealed by the outer decorative layer 11. These layers 10, 11 can be either single-layer or multi-layer. For example, each of the layers 10, 11 can be two co-extruded PHA layers.

[0077] In an alternative embodiment (not shown), the second side 2b of the MFC layer 2 faces the substrate 6.

[0078] Third Embodiment Fig. 6 discloses a third embodiment of the packaging material 5.

[0079] The packaging material comprises a substrate 6 based on paper or cardboard. The substrate 6 has a first side 6a (so-called printing surface) and a second side 6b opposite to the first side 6a. The PHA adhesive layer 7 is deposited on the second side 6b of the substrate 6.

[0080] The packaging material further comprises the barrier film 1, 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. The first primer layer 3 is coated with the vacuum-deposited layer 4.

[0081] The barrier film 1 is attached to the second side 6b of the substrate 6 via the adhesive layer 7. In addition, the adhesive layer 7 can also protect the vacuum-deposited layer 4.

[0082] FIG. 6 discloses a preferred embodiment in which the second side 2a of the MFC layer 2 faces the substrate 6.

[0083] The second side 2b of the MFC layer 2 is preferably sealed by the inner liquid barrier layer 10, and the first side 6a of the substrate 6 is preferably sealed by the outer decorative layer 11. These layers 10, 11 can be either single-layer or multi-layer. For example, each of the layers 10, 11 can be two co-extruded PHA layers.

[0084] In an alternative embodiment (not shown), the second side 2b of the MFC layer 2 faces the substrate 6.

[0085] A major advantage of the barrier film according to the present invention is that it is retortable as compared to a barrier film using a water-soluble bonding layer.

[0086] Another advantage of the present invention is that waste paper from the primer-coated MFC layer, i.e., the MFC layer 2 and the PHA dispersion coating layer 3, 9, can be decomposed when making a new MFC layer 2 and reused in an amount of 0 to 60% by weight. Such an MFC layer 2 may optionally contain 0 to 50% by weight of uncoated waste paper (without PHA dispersion primer), 0 to 50% by weight of coated waste paper (with PHA dispersion primer), 0 to 50% by weight of unrefined or moderately refined pulp, and >50% by weight of MFC or highly refined pulp.

[0087] Example 1 of the finished paper stock composition: 10% by weight of uncoated waste paper, 10% by weight of coated waste paper, 10% by weight of pulp (refined to Shopper-Reigler: SR25), 70% by weight of MFC pulp (refined to SR92).

[0088] Example 2 of the furnish composition: 15 wt% of uncoated broke, 5 wt% of pulp (refined to SR25), 80 wt% of MFC pulp (refined to SR92).

[0089] According to the present invention, there is disclosed a packaging material designed for aseptic packaging and also designed, for example, to extend the shelf life by heat-treating at a high temperature using steam as a heat medium. Examples of such heat treatments for extending the shelf life include pasteurization following hot filling, or retort and steam autoclave treatments.

[0090] The treatment is usually carried out at a temperature higher than 80°C. By the heat treatment, both the package and the packaged contents (e.g., food) can be sterilized.

[0091] The heat treatment can be carried out under overpressure and at a temperature exceeding 100°C (e.g., a temperature exceeding 110°C or 121°C, e.g., 121 - 140°C).

[0092] As an alternative heat treatment method for such sterilization for retort treatment or autoclave treatment, there is a so-called "hot fill by pasteurization" treatment (wherein, further, food that has been partially sterilized by being preheated is aseptically filled), and the filled and sealed package is kept at a high temperature (e.g., a temperature of 80 - 100°C) for a long heat treatment. To keep the package at a high temperature, the package is transferred through a thermal sterilization tunnel, which is divided into several treatment zones, and these treatment zones include a warm-up zone, a heat treatment zone, and a cooling zone. In the warm-up zone and the heat treatment zone, the package can be treated with dry heat, i.e., hot air without steam, or with steam and / or water sprayed or flowed over the package. Cooling is usually carried out by flowing cooling water over the package. Most commonly, the pasteurization temperature of the hot fill is adjusted (warmed up and cooled down) with water.

[0093] The above has described the present invention based on several specific embodiments. However, those skilled in the art will understand that other embodiments and modifications are possible within the scope of the following claims.

Claims

1. A barrier film (1) for a paper or cardboard-based packaging material, the barrier film comprising a microfibrillated cellulose layer (MFC layer) (2) having a first side (2a) and a second side (2b), wherein the MFC layer has a basis weight of 20 to 100 g / m². ２ The range is preferably 20 to 50 g / m². ２ It is within the range and has a density of 650 kg / m³ ３ In a higher barrier film (1), The barrier film (1) - PHA is coated with a dispersion and coated on at least one side of the MFC layer, with a coating weight of 0.5 to 12 g / m². ２ Preferably 1 to 8 g / m ２ A primer layer (3,9) comprising 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, - A vacuum-deposited thin layer (4) coated on the first primer layer (3), having a thickness of 20 to 500 nm, preferably 20 to 200 nm, and containing a material selected from the group consisting of aluminum, magnesium, silicon, copper, aluminum oxide, magnesium oxide, silicon oxide, and combinations thereof, preferably aluminum oxide, Furthermore, A barrier film (1) characterized by the following features.

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. A barrier film (1) is coated onto a vacuum-deposited layer (4) with a coating weight of 0.5 to 20 g / m². ２ The barrier film (1) according to claim 1, further comprising a PHA coating protective layer (8), wherein the PHA type is selected from the group consisting of PHB, PHBV, PHBH, P (3HB4HB), and combinations thereof.

5. The barrier film (1) according to claim 1, wherein the MFC layer (2) has a surface roughness (Parkerprintsurf: PPS) on at least one side in the range of 0.5 to 6 μm at a clamping pressure of 1.0 MPa in accordance with ISO 8791-4.

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

7. The barrier film (1) according to claim 1, wherein the solid content of PHA in the dispersion is >20% by weight, preferably >35% by weight, and most preferably 45-60% by weight.

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

9. The MFC layer has a water absorption rate of 60 g / m² (determined according to COBB 60 and SCAN-P 12:64). ２ A lower barrier film (1) according to claim 1.

10. In accordance with ASTM F1927-20, at 23 °C and 50% RH, the oxygen transmission rate (OTR) is < 10 mL / m ２ / day, preferably < 5 mL / m ２ / day, most preferably < 2 mL / m ２ / day, the barrier film (1) according to claim 1.

11. In accordance with ASTM F1927-20, at 38°C and RH 90%, the oxygen permeability (OTR) is <30 mL / m². ２ / day, preferably <20 mL / m³ ２ / day, most preferably <10 mL / m³ ２ The barrier film (1) according to claim 1, which is / day.

12. In accordance with ASTM F-1249-20, the water vapor transmission rate (WVTR) is <5 g / m² at 23°C and 50% RH. ２ / day, preferably <2 g / m ２ / day, most preferably <1 g / m ２ The barrier film (1) according to claim 1, which is / day.

13. In accordance with ASTM F-1249-20, the water vapor transmission rate (WVTR) is <20 g / m² at 38°C and 90% RH. ２ / day, preferably <15 g / m ２ / day, most preferably <10 g / m ２ The barrier film (1) according to claim 1, which is / day.

14. A paper or cardboard-based packaging material (5) comprises a paper or cardboard substrate (6) having a first side (6a) (a so-called printing surface) and a second side (6b) facing the opposite direction from the first side (6a), The packaging material is - A PHA adhesive layer (7) coated on the second side (6b) of the substrate (6), and - The barrier film (1) according to claim 1 A packaging material (5) based on paper or cardboard, further comprising a barrier film (1) attached to a substrate (6) via an adhesive layer (7).

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

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

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